Biodiesel science and technology: from soil to oil

i

Biodiesel science and technology

ii

Related titles: Bioalcohol production: biochemical conversion of lignocellulosic biomass (ISBN 978-1-84569-510-1) Bioethanol is one of the main biofuels used as a petroleum substitute in transportation. Second generation bioalcohol production technology, based on highly efficient biochemical conversion, offers advantages over existing, energy-intensive bioethanol production processes. This book covers the process engineering, technology, modelling and integration of the entire production chain, from feedstock pretreatment on to hydrolysis, fermentation, and purification. Primarily reviewing bioethanol production, coverage extends to the production of longer-chain bioalcohols which will be elemental to the future of the industry. Handbook of biofuels production: processes and technologies (ISBN 978-1-84569-679-5) This book provides a comprehensive and systematic reference on the range of biomass conversion processes and technology. The initial section of the book covers the biofuels production chain and analysis of the environmental, social and economic issues surrounding biofuels production. Sections then follow on the entire range of chemical, biochemical and thermochemical biofuels production routes, with chapters reviewing in detail the development of individual processes, from principles and feedstocks, to batch and continuous processes and technology, and also modelling and optimisation. Handbook of waste management and co-product recovery in food processing, Volume 2 (ISBN 978-1-84569-391-6) Food processors are under pressure, from both consumers and legislation, to reduce the amount of waste they produce and to consume water and energy more efficiently. Handbook of waste management and co-product recovery in food processing provides essential information about the major issues and technologies involved in waste co-product valorisation, methods to reduce raw material waste and water and energy consumption, waste reduction in particular industry sectors and endwaste management. Chapters in Volume 2 focus on the transformation of food co-products using microorganisms and enzymes, advanced methods to optimise food manufacturing, such as closed-loop factories, non-food uses of food waste co-product and commercialisation issues. Details of these and other Woodhead Publishing books can be obtained by:  visiting our web site at www.woodheadpublishing.com  contacting Customer Services (e-mail: [email protected]; fax: +44 (0) 1223 893694; tel.: +44 (0) 1223 891358 ext. 130; address: Woodhead Publishing Limited, Abington Hall, Granta Park, Great Abington, Cambridge CB21 6AH, UK) If you would like to receive information on forthcoming titles, please send your address details to: Francis Dodds (address, tel. and fax as above; e-mail: francis. [email protected]). Please confirm which subject areas you are interested in.

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Woodhead Publishing Series in Energy: Number 7

Biodiesel science and technology From soil to oil Jan C. J. Bart, Natale Palmeri and Stefano Cavallaro

CRC Press Boca Raton Boston New York Washington, DC

Woodhead

publishing limited

Oxford    Cambridge    New Delhi

iv Published by Woodhead Publishing Limited, Abington Hall, Granta Park, Great Abington, Cambridge CB21 6AH, UK www.woodheadpublishing.com Woodhead Publishing India Private Limited, G-2, Vardaan House, 7/28 Ansari Road, Daryaganj, New Delhi – 110002, India www.woodheadpublishingindia.com Published in North America by CRC Press LLC, 6000 Broken Sound Parkway, NW, Suite 300, Boca Raton, FL 33487, USA First published 2010, Woodhead Publishing Limited and CRC Press LLC © 2010, Woodhead Publishing Limited The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publishers cannot assume responsibility for the validity of all materials. Neither the authors nor the publishers, nor anyone else associated with this publication, shall be liable for any loss, damage or liability directly or indirectly caused or alleged to be caused by this book. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming and recording, or by any information storage or retrieval system, without permission in writing from Woodhead Publishing Limited. The consent of Woodhead Publishing Limited does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from Woodhead Publishing Limited for such copying. Trademark notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress. Woodhead Publishing ISBN 978-1-84569-591-0 (book) Woodhead Publishing ISBN 978-1-84569-776-1 (e-book) CRC Press ISBN 978-1-4398-2730-7 CRC Press order number: N10147 The publishers’ policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp which is processed using acid-free and elemental chlorine-free practices. Furthermore, the publishers ensure that the text paper and cover board used have met acceptable environmental accreditation standards. Typeset by Replika Press Pvt Ltd, India Printed by TJ International Limited, Padstow, Cornwall, UK

v

Contents



About the authors



Woodhead Publishing Series in Energy



Preface

1

Biodiesel as a renewable energy source

1.1 1.2 1.3 1.4 1.5 1.6 1.7

Introduction Energy policy Transformation of biomass Global biodiesel development Value chain of biodiesel Bibliography References

1 2 20 26 38 40 44

2

Development of non-food agricultural industries for biofuel applications

50

2.1 2.2 2.3 2.4 2.5 2.6

Introduction Biofuels Biomass potentials and limitations Advanced agroenergy crops Bibliography References

50 51 52 56 59 60

3

Oleochemical sources: basic science, processing and applications of oils

62

Introduction Biochemistry of lipid metabolism Modification of vegetable oil quality Industrial use of vegetable oils Unusual fatty acids

62 64 76 80 85

3.1 3.2 3.3 3.4 3.5

xi xiii xv 1

vi

Contents

3.6 3.7 3.8

Oil processing techniques Bibliography References

90 100 103

4

Vegetable oil formulations for utilisation as biofuels

114

4.1 4.2 4.3 4.4 4.5

Introduction Fuel properties of oils and fats Low-viscosity formulations Bibliography References

114 116 121 125 125

5

Feedstocks for biodiesel production

130

5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12

Introduction Global oilseed and oil production Resources for biodiesel production Main biodiesel crops Minor edible oil crops Fish oils Algae mass culture systems Oleaginous microorganisms Non-edible oilseeds Low-quality feedstocks Bibliography References

130 135 137 143 159 163 168 187 188 197 206 208

6

Emerging new energy crops for biodiesel production

226

6.1 6.2 6.3

Introduction Crop selection criteria for biodiesel application Structure and quality parameters for evaluating alternative feedstocks Agronomic potential of underexploited oil crops by region Bibliography References

226 227 231 244 273 274

Transesterification processes for biodiesel production from oils and fats

285

Introduction Process variables Transesterification kinetics In-situ transesterification Non-catalytic fatty acid alkyl ester production References

285 287 295 308 310 314

6.4 6.5 6.6 7 7.1 7.2 7.3 7.4 7.5 7.6

Contents

vii

8

Biodiesel catalysis

322

8.1 8.2 8.3 8.4 8.5 8.6

Introduction Homogeneous alkaline catalysis in biodiesel synthesis Liquid-phase acid catalysis Heterogeneous catalysis in biodiesel synthesis Bibliography References

322 327 340 348 371 371

9

Processes for biodiesel production from unrefined oils and fats

386

9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 9.9

Introduction Fatty acid esterification Transesterification of acidic feedstocks Jatrodiesel Algal biodiesel Vegetable oil soapstocks for biodiesel application Tall biodiesel Bibliography References

386 389 394 412 414 420 423 425 425

10

Biocatalytic production of biodiesel

434

10.1 10.2 10.3 10.4 10.5

Introduction Enzymatic (trans)esterification Bioplastic-to-biodiesel Bibliography References

434 435 454 454 455

11

Industrial process technology for biodiesel production

462

11.1 11.2 11.3

Introduction Biodiesel plant design and engineering Selected proprietary transesterification processing technologies Selected biodiesel producers Biodiesel blending techniques Bibliography References

462 467

11.4 11.5 11.6 11.7 12 12.1

487 497 505 508 509

Analytical methods and standards for quality assurance in biodiesel production

514

Introduction

514

viii

Contents

12.2 12.3 12.4 12.5 12.6 12.7

Quality control of biodiesel feedstocks Biodiesel standardisation Biodiesel quality management Biodiesel analytical methodology Bibliography References

515 516 526 540 562 563

13

Valorisation of the glycerol by-product from biodiesel production

571

13.1 13.2 13.3 13.4 13.5 13.6 13.7 13.8

Introduction Industrial glycerol production Glycerol purification Industrial uses and markets Innovative use of glycerol Renewable diesel synthesis without glycerol co-production Bibliography References

571 572 575 579 584 611 615 615

14

Sustainability and use of biodiesel

625

14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8

Introduction Energy balance Life cycle assessment of biodiesel Performance characteristics for biodiesel Biodiesel cost structure Biodiesel use and markets Bibliography References

625 627 630 637 658 677 701 703

15

Evolution of biodiesel and alternative diesel fuels

713

15.1 15.2 15.3 15.4 15.5 15.6 15.7 15.8

Introduction Second-generation biofuels Biodiesel: the next generations Hydroprocessing technology Perspectives of biomass-to-liquid fuels Renewable energy and biomass Bibliography References

713 719 724 742 756 772 775 776

16

Epilogue: outlook for biodiesel science and technology 783

16.1 16.2

Introduction State of the biodiesel industry

783 784

Contents

16.3

Challenges for the global biodiesel industry

Appendix Appendix Appendix Appendix Appendix Index

I Acronyms/abbreviations of techniques II (Bio)chemical nomenclature III Physical and mathematical symbols IV General abbreviations V Main websites

ix

789 799 801 810 814 820 822

x

xi

About the authors

Jan C. J. Bart (PhD Structural Chemistry, University of Amsterdam) is a senior scientist with a wide interest in materials characterisation, heterogeneous catalysis and product development who spent an industrial carrier in chemical R&D with Monsanto, Montedison and DSM Research in various countries. Dr Bart has held several teaching assignments in universities in the Netherlands and Italy, researched extensively in both industrial and academic areas, and authored over 250 scientific papers and chapters in books; he is also author of three recent monographs on polymer additive analytics. Dr Bart has acted as a Ramsay Memorial Fellow at the Universities of Leeds (Colour Chemistry) and Oxford (Material Science), a visiting scientist at the Institut de Recherches sur la Catalyse (CNRS, Villeurbanne), and a Meyerhoff Visiting Professor at the Weizmann Institute of Science (Rehovoth), and held an Invited Professorship at the University of Science and Technology of China (Hefei). He is currently a Full Professor of Industrial Chemistry at the University of Messina (Italy). Natale Palmeri (PhD Industrial Chemistry, University of Messina) has interest in heterogeneous catalysis and energy carriers. He acted as a guest junior researcher at the Nicola Giordano CNR-TAE Institute of Advanced Technologies for Energy (Messina) and at the Boreskov Institute of Catalysis (BIC) of Novosibirsk (with Prof. Vladimir Sobyanin). Dr Palmeri has authored several research papers and presently serves as a technologist at ISAB Srl’s Priolo refinery (Sicily). Stefano Cavallaro graduated with an honours degree in Chemistry from the University of Messina, where he now acts as an Associate Professor of Industrial Chemistry in the Department of Industrial Chemistry and Materials Engineering. His interests are applied industrial chemistry, in particular heterogeneous catalysis and transformation and storage of energy. Dr Cavallaro has a standing cooperation with the National Research Council Institute of Advanced Technologies for Energy (CNR-TAE) in Messina and is author of over 110 research papers.

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Woodhead Publishing Series in Energy

1 Generating power at high efficiency: Combined cycle technology for sustainable energy production Eric Jeffs 2 Advanced separation techniques for nuclear fuel reprocessing and radioactive waste treatment Edited by Kenneth L. Nash and Gregg J. Lumetta 3 Bioalcohol production: Biochemical conversion of lignocellulosic biomass Edited by K.W. Waldron 4 Understanding and mitigating ageing in nuclear power plants: Materials and operational aspects of plant life management (PLiM) Edited by Philip G. Tipping 5 Advanced power plant materials, design and technology Edited by Dermot Roddy 6 Stand-alone and hybrid wind energy systems: Technology, energy storage and applications Edited by J.K. Kaldellis 7 Biodiesel science and technology: From soil to oil Jan C.J. Bart, Natale Palmeri and Stefano Cavallaro 8 Developments and innovation in carbon dioxide (CO2) capture and storage technology Volume 1: Carbon dioxide (CO2) capture, transport and industrial applications Edited by M. Mercedes Maroto-Valer 9 Geologic repository systems for safe disposal of spent nuclear fuels and radioactive materials Edited by Joonhong Ahn and Mick Apted 10 Wind energy systems: Optimising design and construction for safe and reliable operation Edited by John Dalsgaard Sørensen and Jens Nørkær Sørensen

xiv

Woodhead Publishing Series in Energy

11 Solid oxide fuel cell technology: Principles, performance and operations Kevin Huang and John Bannister Goodenough 12 Handbook of advanced radioactive waste conditioning technologies Edited by Michael I. Ojovan 13 Nuclear reactor safety systems Edited by Dan Gabriel Cacuci 14 Materials for energy efficiency and thermal comfort in buildings Edited by Matthew R. Hall 15 Handbook of biofuels production: Processes and technology Edited by Rafael Luque, Juan Campelo and James Clark 16 Developments and innovation in carbon dioxide (CO2) capture and storage technology Volume 2: Carbon dioxide (CO2) storage and utilisation Edited by M. Mercedes Maroto-Valer 17 Oxy-fuel combustion for fossil-fuel power plants: Developments and applications for advanced CO2 capture Edited by Ligang Zheng

xv

Preface

Energy, climate change and biofuels have recently become among the hot ‘buzzwords’ and with good reason. Meeting future energy requirements with continued use of limited fossil fuels is now widely recognised as unsustainable because of depleting supplies and environmental degradation. Ideally, energy demands should be reduced. However, the world’s appetite for energy is expected to rise by another 60% in the next 25 years. Prognoses of worldwide petroleum reserves are uncertain but generally predict maximum production in or before the period 2010–20 with a decline to the 1960 level by the year 2050. The world can no longer afford to rely solely on fossil oil and oil-derived products. Finding a cure for mankind’s oil (and carbon) addiction is urgently needed. This requires energy efficiency awareness and changes in consumer behaviour. The best way to maintain energy reliability is through diversity in sources of energy, suppliers and supply routes. Sound public policy calls for measures to gradually out-compete imported crude oil. The world should prepare for a post-fossil oil future. The challenges of ensuring energy security and reducing carbon emissions are closely linked. Global warming is accelerating. The threat of anthropogenic climate change knows no national boundaries and means that rapid action is required to reduce the CO2 output (concentration of 280 ppm before the industrial revolution vs 385 ppm in 2008). Alongside the promotion of sustainability, it is time for alternative low-carbon emission energy sources. However, there is no single low-carbon solution to cover all our energy needs. Investment in technologies that improve energy efficiency for electricity, heating and transportation is vital. A portfolio of different technologies is needed. Society needs to reshape the global energy system in the coming decades. Chemical sciences are crucial in increasing the efficiency of fossil fuels, addressing climate change and developing sustainable and renewable energy sources and a low-carbon economy. Despite best efforts, liquid hydrocarbons, coal and gas will still dominate transport, heat and power for some considerable time to come. It will take decades before we see a real shift away from oil as the predominant

xvi

Preface

fuel source. The pace of changeover from oil will be driven by oil price, unpredictable geopolitical factors and investment in technological innovation and development with protection of the environment. Alternative fuels, energy conservation and management, energy efficiency and environmental protection are becoming all important. With concerns over rising petroleum prices, security of supply, climate change and needs for agricultural product diversity, the race is on to produce fuels from renewable sources. Quite likely, however, fossil fuel prices need to rise even further before more substantial and effective political support is given to exploration of real alternative fuel sources. Possible alternative transportation fuels are many: biogas, bioethanol, biomethanol, biobutanol, cellulosic ethanol, dimethylether, biodiesel, straight vegetable oils (SVO), hydrotreated vegetable oil (HVO), synthetic natural gas (SNG), FT-diesel and hydrogen. Some alternatives to petrol and other fossil fuels are already being used in a variety of forms of transport. Biodiesel derived from oil crops as a liquid energy carrier for transport is a potential renewable and carbon neutral alternative to petroleum fuels. In the medium to long term, switching to other forms of biomass as the raw material for biofuels (and materials) production is probably unavoidable, as fossil oil is a finite resource and food too precious for mankind. The urgency of responsible energy management and its timeframe are well illustrated by a manifold of ambitious (supra)national and industrial targets up to the year 2050. However, current biofuel policies have already caused unforeseen social and environmental problems (rising food prices, deforestation and soil degradation) and therefore require rethinking in terms of criteria for sustainability. Sustainable energy systems are achievable, but the problems are many and need urgent tackling. At present, supply and demand of oils and fats are not in healthy balance. Although mankind is very inefficient in exploiting the photosynthetic process, the energy landscape continues to move rapidly. The need to harness sustainable energy and reduce global warming has led to a search for alternative fuel sources. In contrast with solar energy, biofuels are unique in their impact on agriculture, food, transportation, energy and chemistry and may therefore serve different interests. EC president José Manuel Barroso has stated: ‘Biofuels figure prominently in the common energy policy of the European Union’. Although biofuels are not the most efficient way to harvest solar energy, being liquids they provide a most convenient method of distribution. As we run out of fossil fuels, the ‘green revolution’ may be just as radical as the previous industrial and digital revolutions. The bio-economic revolution aims at responsible industrial development in bioenergy (biofuels) and bioproducts. Biofuels mean a shift away from finite resources to almost infinite possibilities. Traditionally, the agricultural industry has provided

Preface

xvii

food, feed and fabrics. Now we need to add fuel. Use of plant matter as a feedstock for both energy and chemical products includes the development of fermentation-derived alcoholic biofuels, mainly bioethanol (from sugarcane in Brazil to wine in Europe) and more recently biobutanol (from corn grain, wheat, sugar beets, sugarcane and sorghum). Bioalcohols and biodiesel, made from sustainable agricultural crops, also produce valuable by-products in the process. Although first-generation biofuels are in direct competition with food (sugar, maize, vegetable oils), future energy chemistry developments can be expected for the use of woody biomass wastes and residues that are rich in cellulose (rather than in starch). Cellulosic biofuels may be based on lignocellulosic resources such as switchgrass, straw, corn stalks and other agricultural waste. Use of sustainable energy systems is as diversified as the geographical context, as illustrated for some leading countries. Germany already has produced over 2.9 Mt of biodiesel in 2007. The United States has installed 178 biodiesel plants with a total capacity of 10 Mt/yr (as of September 2008) but suffers from underdeveloped domestic use, in stark contrast to Europe. Sweden is a globally acknowledged world leader in biomass combustion (supplying 20% of its national energy needs). Iceland has successfully switched from a coal-based economy to one that uses renewable energy sources (hydroelectric and geothermal) for all heating and nearly all electricity; only transportation still depends on fossil fuels. With the favourable agricultural conditions and flexible processing infrastructure, the majority of Brazil’s road transport is powered economically with a fuel mix made up of 85% (cane-derived) bioethanol. Nevertheless, advanced biofuels based on adequate technological developments and edible energy crops cannot be expected to supply more than some 10–15% of global demand in an environmentally responsible manner without affecting food production. Biodiesel demand creates a fundamental new demand for agricultural commodities that was non-existent several years ago. Better prospects for farming biodiesel without undesirable side effects are based on the use of the non-edible oil of Jatropha, now being cultivated in large plantations around the globe, and on the development of biodiesel from algae, without competing for land area. These feedstock sources will not make a significant impact before 2015. Biodiesel is increasingly being used commercially with a view to decrease dependence on fossil fuel, reduce greenhouse gas emissions from the transport sector and support agriculture. Biodiesel stands as the only renewable energy source that is nowadays considered as a (partial) substitute for fossil diesel. Biodiesel has similar combustion properties as diesel and is considered a clean fuel. The growth rate of the rapidly changing and maturing biodiesel industry is without comparison in the chemical industry. The total installed capacity (mid 2008) has exceeded

xviii

Preface

some 30 Mt in a matter of only few years. Commercial processes for manufacturing biodiesel from a great variety of feedstocks (including urban wastes) almost invariably employ different catalysts. An analysis of state-of-the-art biodiesel technology is timely. Messina

1

Biodiesel as a renewable energy source

Abstract: Renewable fuels are bound to gradually replace fossil fuels. Development of biorefineries will mark the historic transition into a sustainable society in which biological feedstocks, processes and products constitute the main pillars of the economy. Energy policy facilitating the introduction of biofuels, including biodiesel, avails itself of taxation, subsidies and mandates, which are not always unquestioned. Transformation of vegetable oils to liquid fuels is achieved industrially by catalytic transesterification. Biodiesel manufacturing, as yet based mainly on rapeseed oil (Europe), soybean oil (US, Argentina, Brazil) and palm oil (SouthEast Asia), requires further feedstock development. Important actors in the biodiesel value chain are vegetable oil milling facilities and the crude oil industry. Key words: Renewable fuels, energy policy, transformation of biomass, global biodiesel development, biodiesel value chain.

1.1

Introduction

Our industrial civilisation greatly depends upon abundant, low-cost energy, which could be produced without political intervention and suppression. Despite recent new oil discoveries in areas such as the Gulf of Mexico, the Tupi and Guará fields off South-East Brazil, Sudan, the Caspian Sea, Sakhalin, and in the Arctic, fossil resources are limited and nowadays no longer constitute cheap and reliable raw materials. Moreover, many convenient industrial products and processes based on these resources seriously damage the environment. The Petrochemical Age has resulted in massive pollution of air, water and soil as well as in emissions of anthropogenic greenhouse gases (GHGs) thought to be at least partly responsible for the recent climate change [1]. Warming of the climate system is unequivocal and there is a high probability that it has taken place during the last five decades or so as a result of human actions. In order to tackle climate change it is deemed necessary to stabilise the atmospheric level of CO2 at about 450 ppm by the end of the century. This means an emission level of 2 t CO2/yr per person, corresponding to the present Indian average (the current European level is at 11–12 t). Meeting the target requires a variety of actions, including government regulation, energy efficiency in industry (in particular in chemical, cement and steel manufacturing) and elsewhere, production of biofuels in a zerocarbon cycle, development of GM crops, nuclear power and photovoltaics, 1

2

Biodiesel science and technology

and capturing and storage of CO2. It is uncertain, however, that global warming can be limited by implementing low-carbon energy technologies. This would anyhow require considerable R&D efforts (not foreseen by the Kyoto Protocol). There is also no unanimous short-term solution for reversing climate change. Moreover, the harmful climatic effects (‘human-caused global warming’) due to increased hydrocarbon use and CO2 emissions have also been questioned [2, 3]. About 40% of the heat trapped by GHGs is due to gases other than CO2, primarily methane [4]. In any case, water, oxygen and CO2 enable life. In a higher CO2 environment crop growth rates may be expected to increase to the benefit of agriculture. The search for alternatives to fossil fuels dates back to the petrol crisis of the early 1970s, but just more recently the looming dangers of a global climate change are driving renewed interest in biofuels. The world is awakening to the renewable fuels movement and the public clamours for alternatives to foreign petroleum. The last 25 years have witnessed a gradual but growing shift towards greater use of plant matter as a feedstock for both energy and chemical products. The combination of steeply increasing oil prices (in particular in the past few years), environmental awareness, relatively low cost of plant material (until recently), and the development of biorefineries prepare mankind for a historic transition into a sustainable society in which biological feedstocks, processes and products become the main pillars of the economy. This calls for further developing the necessary science and technology that enable this transition, while at the same time investing in infrastructure and defining economic and policy issues. The various biomass-based resources used so far for fuel generation have mostly been (expensive) food crops, but biomass also consists of (cheap) agricultural and forest residues (e.g. crop residues, rice husk, cotton stalk, pine sawdust, sugarcane, bagasse, etc.), urban and industrial residues. Renewable and sustainable resources, which can be used as an extender or a complete substitute of diesel fuel may play a significant role in agriculture, industrial and transport sectors in the energy crisis situation. Agricultural and transport sectors are highly diesel dependent. Various alternative fuel options for diesel are mainly biogas, producer gas, ethanol, methanol and vegetable oils. Development of new energy sources replacing fossil sources is the greatest challenge of the 21st century. Renewable resources are more evenly distributed than fossil resources and energy flows from renewable resources are more than three orders of magnitude higher than current global energy use.

1.2

Energy policy

The world economy depends on only two significant energy carriers, namely hydrocarbons (natural gas, gasoline and diesel fuel or heating oil) and electrical current. Whereas the primary energy supply differs greatly from

Biodiesel as a renewable energy source

3

nation to nation, hydrocarbons are our main means of storing energy. At present, the consumption of primary energy is globally highly dependent on fossil fuels, as shown in Table 1.1. US energy figures for 2006 are as follows: hydrocarbons, 84.9%; nuclear, 8.2%; hydropower, 2.9%; wood, 2.1%; biofuels, 0.8%; waste, 0.4%; geothermal, 0.3%; wind and solar, 0.3% (43% being used for electricity production). With France being the nuclear energy champion, Germany is a solar power leader (total PV capacity of 3063 MWp in 2006); by the end of 2007, the installed photovoltaic capacity in the EU amounted to 4700 MWp (globally: 9200 MWp). USA and Spain are actively developing large-scale concentrating solar power (CSP) plants. Large-scale hydropower provides virtually all of Norway’s electricity. Wind power accounts for at most 5% of primary energy generation in Europe, but up to 21% in Denmark. Important onshore wind farms are located also in USA, Portugal and Egypt; focus is nowadays on large offshore power stations (e.g. in Sweden, UK, Belgium and the Netherlands). In global energy supply fossil fuels amount to over 80%. Petroleum provides a significant fraction (~ 35%) of the world’s energy [5]. Currently, global production and world consumption are approximately 85 Mbd of conventional oil and 11 Mbd of natural gas (totalling 5600 Mt/yr); the predicted output of oil would stall at about 100 Mbd. Even the world’s largest oil fields (Ghawar, 80 billion barrels; offshore Safaniya, 25 billion barrels, and Cantavell, 20 billion barrels) are at the limits of their capacity and oil extraction is slowing down. Actually, it is even not so much the quantity of total reserves (which are still immense), which causes an impending oil shortage in the short term [6], but the flow and quality of the oil recovered. There exists insufficient refining capacity for heavy oils with higher molecular mass hydrocarbon composition and higher sulphur content. The era of cheap oil for our oiloholic society has definitely finished. According to some (Energy Watch Group), maximum petroleum production already occurred in 2006. More optimistic views foresee an irreversible decline in oil production by 2015–20 in the 20 oil-producing countries (rather concentrated areas of the globe). On the other hand, global demand for energy (and food) is predicted to double by 2050 [7, 8]. The International Table 1.1 Fuel shares of world total primary energy supply (%) Energy source

Developed countries

Developing countries

Biomass Natural gas Solid fuels Crude oila Hydropower Nuclear

3 24 26 35 6 6

35 7 28 23 6 1

a

Gasoline, diesel, aviaton fuel, marine bunker, middle distillates.

4

Biodiesel science and technology

Energy Agency (IEA) estimates an increase in energy consumption of 55% between 2005 and 2030 at an annual increase of 1.8%. Safe global fossil reserves, estimated as 1.3 trillion barrels (2000), will be exhausted in less than 40 years. While it is difficult to predict when the world is going to run out of petroleum, the reduction in the rate at which it can be extracted has set in before alternatives such as biofuels are cost effective. The IEA thus warns of a forthcoming energy crisis: the gap in supply and demand for oil worldwide is expected to occur by 2015, when there will be a shortage of at least 12.5 Mbd (or about 15% of global needs). Energy changes take time. Natural gas (NG) accounts today for over 20% of world primary energy production and represents the fastest growing primary energy source. Proven gas reserves are located mainly in the Middle East (43%) and Russia (33%). A peak in conventional gas production may occur between 2020 and 2050. Exploration of methane hydrates is still in its infancy [9]. Among the fossil energy carriers, coal has the longest projected range (155 years worldwide). Supply security means for many countries (such as Poland) that coal remains the cheapest and most readily available form of energy. Fossil fuels will still dominate the scene for some time to come (> 80% in 2030). Continuity of supply of fossil fuels, particularly crude oil, is increasingly being governed by geopolitical, economic and ecological factors. Political developments have an impact on fuel prices, while environmental concerns require a reduction in greenhouse gases and toxic emissions. There is an impelling need for energy diversification and containment of the negative environmental impact of indiscriminate use of mineral fuels. We clearly require an alternative fuel or strategy soon if we are to keep transportation going and the global economy running. Hydrogen is an environmentally friendly energy carrier rather than a primary fuel source. Moreover, the hydrogen era is still far over the horizon. With the hydrogen fuel economy dream fading, time is running short. Biofuels now account for over 1.5% of global transport fuels (around 34 Mtoe in 2007). In the future, an increasingly larger share of global consumption of liquid energy carriers must be filled with renewable resources (vegetable oils, wood, straw, waste). Investments in a low-carbon energy infrastucture are needed. Although transport is globally not the main consumer of energy (accounting for about 30% of total EU energy needs), it is almost fully (98%) dependent on oil-derived products and accounts for 67% of final oil demand in the EU. Transportation represents a key GHG and CO2 generating sector (especially in urban centres), responsible for 20% of total GHG and 26% of all CO2 emissions in the EU. Transport accounts for about 90% of the increase in CO2 emissions in the period 1990–2010 and is the main reason for not meeting the Kyoto objectives. Renewable resources such as biomass can be used for the production of chemicals and the supply of energy. Renewables accounted for 8% of

Biodiesel as a renewable energy source

5

the EU27’s energy consumption in 2006. Use of renewable resources can contribute towards the conservation of finite energy resources. Despite an expected increase of about 1.8% per year, in the short term the contribution of renewables to the global primary energy supply will remain at only approximately 14% [10]. Biomass and biofuels constitute a big share of the renewable energy sources (RES). Production of first-generation biofuels (Fig. 1.1) requires the use of 0.2 to 1.3 L fossil fuel per litre of biofuel [11]. Apart from biomass and hydropower, the impact of other potentially important renewable sources such as geothermal, solar (PV, CSP), wind, tidal/ wave/ocean is still negligible as primary energy sources (0.416%, 0.038%, 0.050% and 0.0005%, respectively). Hydroelectric energy (highly important to countries such as Norway and Iceland) may be expected to grow, in particular in currently less developed areas. The contribution of geothermal energy is expected to be limited (e.g. Iceland). The impact of solar energy could increase significantly with organic solar collectors which reduce the effective cost of photovoltaic cells by an order of magnitude [12]. The United Kingdom plans to hit its 2020 target of producing 15% of its energy from renewable resources by a 1000% increase over current renewable energy levels principally by vastly boosting wind power production. The country also utilises impressive coal (accessible via underground gasification), wave and tidal power resources. Oceanlinx Ltd (Sydney) is developing wave farms in Rhode Island waters.

Biomass (sugar)

Hydrolysis

Fermentation

Ethanol recovery

Bioethanol

Residue

Biomass (oleaginous)

Oil extraction

Transesterification

Ester recovery

Methanol or Ethanol

Glycerol

1.1 First-generation biofuels.

Biodiesel FAME or FAEE

6

Biodiesel science and technology

The success of biofuels is highly contingent on national governmental measures to encourage their use through positive contributions of agriculture, energy efficiency, environmental and energy security legislation and regulations, legal obligations and/or beneficial measures (mandates, production plant incentives, federal tax credits and forgiving sales tax), as well as petroleum prices. The EU25 are heavily dependent upon energy imports. The share of imports in their total energy consumption (47.1% in 2005) could easily reach 67.5% by 2030, which threatens the security of the EU oil supply. Figure 1.2 shows the road fuel demand in the EU, which is steadily shifting from gasoline to diesel. European refineries are characterised by a gasoline surplus and a diesel deficit. The European refinery system will not be able to meet the projected demand for diesel. Demand for diesel in the US is expected to increase by about 12% over the next 15 years while demand for petroleum-based gasoline is expected to decline by 7% over the same period. Before 2004 diesel was always less expensive than gasoline in the US. In the past year, diesel prices in the US have greatly increased relative to gasoline (with increases of US$1.81 and US$1.12, respectively) as a result of high global demand and insufficient diesel refining capacity.

200

Gasoline Diesel

Mt/yr

150

100

50

0 1995

2000

Year

2005

1.2 Gasoline and diesel demand in the EU.

2010

Biodiesel as a renewable energy source

7

Under the Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) most industrialised countries have committed themselves to limit or reduce their emissions of greenhouse gases (CO2, CH4, N2O, HFCs, PFCs, SF6) by 5.2% in relation to the base year 1990 or 1995. The contribution of H2O to global warming was not considered. Reductions in GHG emissions in the framework of the Kyoto Protocol (1997) are to be achieved by a combination of energy efficiency, reforestation, use of renewable energy sources, carbon capture and storage (CCS), and application of automatic meter reading (AMR technology). The Kyoto Protocol (141 signatories, US excluded) also provides for industrialised countries to implement project activities that reduce emissions in developing countries, in return for certified emission reductions (CERs). Biodiesel projects are actually not actively participating under the Kyoto Clean Development Mechanism (CDM) [13]. The EU is committed to cut its GHG emissions within 2008–12 by 8% from their 1990 level. Ambitious self-imposed climate change objectives were defined by most EU member states. The UK domestic carbon emission reduction target is 20% below 1990 levels by 2010 (and 80% by 2050). However, the likelihood of such domestic targets being met in 2010 is highly doubtful. In fact, both the Kyoto protocol and (inter)national targets on climate change are very ambitious, high cost and environmentally limited. Figure 1.3 illustrates the impact of CO2 in the case of use of fossil and renewable resources. Protocols are being developed to enable biodiesel producers to qualify for carbon credits.

1.2.1 Biodiesel strategy In 2001 the European Commission agreed on a strategy for sustainable development, including the use of biofuels. The EU aims at increasing the share of renewable energy from 5.4% in 1997 to 12% in 2010. EU Directive 2001/77/EC aims at increasing renewable electrical energy (biopower) in

Fuels, power and products

Biorefineries

Biomass/ Bio-organics

CO2

1–10 yrs Net CO2 reduction

Fossil resources (petroleum, natural gas)

> 106 yrs

Net CO2 gain

Biomass/ Bio-organics

1.3 Short- and long-term CO2 cycles.

Fuels, power and products

Production and refining

8

Biodiesel science and technology

the EU25 from 14% in 1997 to 21% in 2010. In May 2003, the EU outlined the Biofuels Directive (EU Directive 2003/30/EC) on the Promotion and Use of Biofuels and Other Renewable Fuels for Transport. Biodiesel should substantially reduce petroleum used and GHG generated compared with their petroleum-derived alternatives. The Biofuels Directive requires member states to increase the use of biofuels to a minimum of 2% of total liquid fuel consumption by 2005 (or 5.7 Mt) and to 5.75% by 2010 (or 16.5 Mt). If the target of 5.75% market share of biofuels in 2010 is met (current expectations: 4.2%), the EU27 will be short in feedstock to support the necessary biodiesel production (9.8 Mt/yr) (see Table 1.2). The EU requires 5.1 Mt/yr extra biodiesel capacity between 2006 and 2010. The agricultural surface needed for energy crops would then amount to 15–18 Mha (out of a total of 103.6 Mha EU cropland) or about 15–16% of the total agricultural area. Satisfying these objectives is an enormous challenge for each member state, especially if one considers that some 10% of total cultivated land dedicated to energy crops is generally considered to be the limit. Government policies are expressed through taxation, subsidies and mandates. Government subsidies substantially affect the commercial viability of biodiesel. Oilseed growers may benefit from subsidies. Subsidies to blenders may lead to increased demand for feedstocks. Tax credits for capital investments may benefit farmers. There is uncertainty about which producers or processors are able to take advantage of the particular programmes. In November 2003, the Energy Tax Directive 2003/96/EC was adopted concerning taxation of energy products, including detaxation of pure biodiesel (and blends containing up to 5% biodiesel) and biofuels to boost their production. Tax exemption (initially for six years) is limited to the biomass portion of the biofuel. This council directive is vital to achieve the targets in the Biofuels Directive. Without tax relief (operated by various EU member states) biofuels are at present not competitive with conventional fuels. Tax waivers have been responsible for the rapid growth of biodiesel Table 1.2 EU biofuel targetsa

   

Year

Target shareb

Biodiesel (Mt)c

Gasoline (Mt)d

Total (Mt)

2005 2006 2007 2008 2009 2010

2.00 2.75 3.50 4.25 5.00 5.75

3.4 4.7 5.9 7.2 8.5 9.8

2.3 3.2 4.1 5.0 5.9 6.7

5.7 7.9 10.0 12.2 14.4 16.5

a

Directive 2003/30/EC (8 May 2003). Percentage of total demand. c Based on EU consumption (170 Mt, 2005). d Based on EU consumption (117 Mt, 2005). b

Biodiesel as a renewable energy source

9

in Europe. Also in November 2003, the EU agreed on a Biodiesel Standard (EN 14214 CEN) for fatty acid methyl esters (FAME). Another development was adoption of a revised standard for petroleum diesel (EN 590) which specifies that blends up to 5% FAME are considered as conventional diesel in all respects. This modification simplifies marketing of biodiesel/diesel blends. A number of government programmes encourage oilseed production for biodiesel. These programmes alter the private profitability of oilseed production in direct and indirect ways. The main effect is to lower the costs for oilseed growers and biodiesel processors, while at the same time raising the costs borne by taxpayers. Oilseed growers can benefit directly from subsidies or tax credits related to their production or investments. They also can benefit indirectly by incentives paid to oilseed crushers or biofuel processors, because these incentives can alter the prices paid to producers in ways that effectively share the government subsidies among growers, processors and consumers. On 8 February 2006, the European Commission (EC) adopted an ambitious European Union (EU) Strategy for Biofuels to boost production from agricultural raw materials. The main objectives are as follows: ∑ ∑

to promote biofuels in both the EU and emerging countries; to prepare for large-scale use of biofuels by improving their cost competitiveness and increasing research into second-generation fuels; and ∑ to support developing countries where biofuels production could stimulate economic growth. Unfortunately, the document assumed (erroneously) that biofuel production would have very little impact on feedstock prices and land use. Secondgeneration biofuel feedstocks are expected to play an increasing role only after 2010. It was estimated that 27% of EU biofuel demand could be met domestically, but would also require increases in feedstock production and land use (up to 13% of available area). Rising demands for biofuels were considered to require accelerated imports of oilseeds (+ 19.9%) in the EU in the period 2006–12. A European strategy for the security of energy supply sets the objective of 25% substitution of conventional fuels by alternative fuels in the road transport sector by the year 2030. The EU claims it can meet the targets for bioenergy and biofuels for 2010, 2020 and 2030 with no damage to biodiversity, soil or water resources [14]. Some EU measures aiming at promotion of increased use of renewable resources comprise the policy of use of set-aside land for non-food crop purposes, and industrial oilseed subsidies. In fact, large tracts of land formerly used to cultivate annual crops had become barren. The Mid-Term Review Reform of the Common Agricultural Policy (CAP), which defines set-aside

10

Biodiesel science and technology

arrangements under which non-food crops for biodiesel production can be grown, has led to support for such energy crops in the form of a carbon credit of 745/ha. Table 2.2 lists subsidised hectarage for energy crops in Europe. In the US, farmers are being paid billions of dollars not to farm up to 36 million acres. National biofuels legislation and targets vary widely among the EU27 member states. Biofuels policies of the EU are (at least partly) aimed at GHG reduction (35% or more). There is some consensus about the GHG calculation methodology [15]. Some EU member states intend to provide incentives for biofuels with higher GHG reduction. Even though fossil fuels will still be available for several decades, producing supplementary fuels from biomass addresses various important societal concerns without requiring substantial modification of existing vehicles or of the fuel distribution infrastructure. Challenges to a nation’s energy security and diversity encompass: ∑ ∑ ∑ ∑ ∑ ∑

increasing the efficiency of all energy-intensive sectors through conservation and improved technologies; promoting diversity of energy supply; decreasing the dependence on foreign energy imports; improving national energy security; decreasing the environmental impact of energy-related activities (climate, GHG emissions, local pollution); and rural development (support for agriculture).

As the IEA claims, biofuel market developments are mainly influenced by agricultural policies, rather than security of energy supply issues [16]. In fact, supply security should not be overemphasised since the percentage of a country’s fuel supply that can be replaced with biofuels is small (some 10%), in particular taking into account the anticipated yearly growth of the global transport sector by 2.1%, with expected large national differences (cf. car density/1000 pp: USA, 500; Germany, 710; UK, 523; France, 633; India, 14; P.R. China, 13). An important biofuels policy goal is a sustainable production and use of bioenergy crops as part of a renewable energy mix in order to combat climate change. Drivers for increased use of biofuels are country specific, with emphasis on securing the economy and diversifying energy sources (e.g. in the US, UK, P.R. China, India, Taiwan, Indonesia), reducing reliance on imported energy products (EU, US, Thailand, Argentina, Brazil), readjustment of agricultural structure, regional development and improving farmers’ income (Brazil, Mexico, Philippines, P.R. China), added value to national economy (Singapore, Philippines, Malaysia, Argentina) or health and environmental protection/sustainability (EU, UK, Japan, South Korea, Malaysia). Colombia intends substituting all imports of diesel for domestic biodiesel by 2020.

Biodiesel as a renewable energy source

11

EU policy toward utilising renewable energy aims at: (i) combating climate change; (ii) reducing local environmental stress; (iii) creating jobs (regional development); and (iv) securing energy supply. Changing national energy systems requires much time and brings huge costs. Consumer acceptance of the drive to substitute or blend some of the mineral-based fuel with biomass fuel in gasoline and diesel is receiving increasing support. Climate change is low on the list of global priorities (Copenhagen Consensus). Several states have enacted legislation mandating the use of biodieselbased products, such as South Korea, B0.5 (current) to B3 (2012); Taiwan, B1 (current) to B2 (2010); Thailand, B2 (Apr. 2008); Philippines, B2 (2009); EU, B7 (2011); Norway, B5 (2009); Romania, B2 (2008); Canada (federal), B2 (2012); Brazil, B3 and B4 (2009) to B5 (2010); Argentina, B5 (2010); Colombia, B5 (2008) to B10 (2010) and B20 (2012); Peru, B2 (2009) to B5 (2011); where B# denotes the percentage of biodiesel in a biodiesel/diesel blend. Mandates set by many governments will probably not be achieved. Biodiesel blends are now also mandated in some US states (LA, MA, MN, NM, OR, PA and WA). The Minnesota Biodiesel Mandate (2002) requires that all diesel fuel for transportation use in Minnesota, among the top five soybean-producing states in the US, contains at least 2% biodiesel in 2005 (up to B5 by 2009 and B20 by 2015) [17]. Globally, public authorities promote the use of blends of biofuel and conventional fuel through directives and by setting ambitious goals (Table 1.3). EU targets comprise a 10% voluntary biodiesel inclusion by 2010, and 10% obligatory by 2020. The European Biodiesel Board (EBB) favours a biodiesel share of 15% in the medium to long term. A binding EU-wide target (RED), signed up in 2007, is to source 20% of the total EU energy needs from renewables by 2020 [18]. Long-term goals in UK energy policy are securing clean energy at affordable prices and tackling climate change by reducing CO2 emissions [19]. The UK’s Climate Change Bill (a world first) has set legally binding targets for cutting GHG emissions by 80% (based on 1990 levels) by 2050. Achieving this target requires de-carbonising electricity generation, by a combination of renewables, nuclear, and carbon capture and storage. In the UK the current options for biofuels are bioethanol from the fermentation of sugars in sugarbeet or cereal crops and biodiesel from oilseed rape and (imported) soybean. The UK Renewable Transport Fuels Obligation (RTFO) stipulates that from April 2008 biofuels must make up at least 2.5% of the sales of transport fuel suppliers, increasing to 5% by 2010 and 10% by 2015. To satisfy RTFO without significant biofuels imports, which would be counterproductive, requires technological advances (second-generation technologies), including conversion of agricultural and forestry lignocellulosic waste materials to bioethanol and thermal conversion processes (conversion of biomass into syngas). The UK government has also set a target that, by 2020, 20% of energy should be from renewable sources [20].

12

Biodiesel science and technology

Table 1.3 Some long-term (national) goals in energy policy   Challenger Target(s) World

Reduction in GHG emissions by 5.2% on 1990 levels throughout the 2008–12 perioda; halving CO2 emissions by 2050

EU25

10% market share for biomass-derived transport fuels by 2020b



Obligatory non-food set-aside rate of 10% for period 2000–06c



Reduction of energy consumption of 20% by 2020



Source 12% of total domestic energy consumption from renewables by 2010 (20% by 2020, 33% by 2030)



Reduction by 20% of imported gas/petrol by 2030



25% of transport fuel from biofuels by 2030



Reduction of GHG emissions below 1990 level (20% by 2020, 50% by 2050)

UK

Renewable transport fuels accounting for 5% in 2010 and 10% in 2015d



Renewable energy sources (including biofuels) accounting for 20% by 2020



Reduction in CO2 emissions by 26–32% (2020) to 80% (by 2050) against 1990 baselinee

Germany Biodiesel target of 10% by 2015

Reduction of GHG emissions by 40% by 2020 against 1990 levels

Portugal

Generation of 30% of power by new technologies by 2020

Iceland

Propulsion of fishing fleet and all vehicles with hydrogen produced with geothermal and hydropower by 2050

USA

Tripling use of bio-based products and bioenergy over 2001–10 period



Increasing use of bioethanol fuel up to 5% of gasoline consumption by 2010



Reduction by 30% of imported petroleum by the year 2010f



Minimum renewable diesel of 0.5 Bgy (2009) to 1 Bgy (as from 2012)g



Cost-competitive plant-derived ethanol by 2012



25% increase in energy efficiency by 2012h



Renewable fuels (largely bioethanol) industry volume of 7.5 Bgy by 2012h



Soy biodiesel share of 4% in 2016



Replacement of 15% of current gasoline consumption by 2017i



Minimum of 36 Bgy of alternative fuels by 2022g; 60 Bgy by 2030



Replacement of more than 75% of oil imports from Middle East by 2025



Biomass supplies 5% of nation’s power by 2030 (5.0 quad)j



Replacement of 12–18–25% of industrial organic chemicals with biomass-derived chemicals by 2010–20–30j



Biomass share of 20% (9.5 quad) for transportation fuels by 2030j



Subsidised agricultural commodities for bioenergy productionk

Biodiesel as a renewable energy source

13

Table 1.3 Continued Challenger Target(s)  Australia

1 Mgy biofuel target by 2012



Reduction of GHG emissions by 25% below 2000 level by 2020 and by 60% by 2050

P.R. China Share of 10% renewable energy by 2010, 15% by 2020 India

Share of 10% renewable energy by 2012

a

Kyoto Protocol (1997). EU Fuel Quality Directive (17 Dec. 2008). c MacSharry Common Agricultural Policy (CAP) Reforms (1992, 2000). d Renewable Transport Fuels Obligation (RTFO). e Climate Change Bill (26 Nov. 2008). f US Energy Policy Act (EPAct, 1992). g Energy Independence and Security Act 2007. h US Energy Policy Act 2005. i State of the Union 2007. j Biomass R&D Technical Advisory Committee (BTAC). k US Department of Agriculture’s Commodity Credit Corporation (CCC) program. b

Germany’s Renewable Energy Act is a support programme offering attractive feed-in tariffs to renewable energy suppliers. The production capacity of biodiesel requires at least doubling in order to meet the country’s biodiesel target of 10% by 2015. B10 is being rejected by German car companies who believe the higher blends lead to a dilution of the engine oil due to the different boiling point of biodiesel. Accelerated biofuel targets in France are as follows: 2% in 2007, 5.75% in 2008, 7% in 2010 (or 2.65 Mt biodiesel; requiring imports in view of limited acreage), and 10% in 2015. The United States relied on imported oil to meet 58.4% of its crude oil needs in 2004 (47% in 1990) at a cost of US$200 billion. The total consumption of petroleum in the US corresponds to about 7.5 billion barrels of oil equivalent each year (43 ¥ 1015 BTU), and almost 70% of this petroleum is consumed by the transportation sector. Low-carbon fuel standards (LCFS) are being developed at the state, federal and international levels. Less than 5% of America’s energy is renewable. In the US, biofuels are being driven by a variety of regulations, including the US Department of Agriculture’s Federal Biobased Products Preferred Procurement Program (FB4P). The primary objective of the US Energy Policy Act (EPAct, 1992), administered by the Department of Energy (DOE), is to reduce US reliance on foreign oil by the promotion of alternative fuels. While EPAct 1992 sets a replacement of 10% of petroleum-based transportation fuels with domestically produced alternative fuels by 2000 and 30% by 2010 (goals far-off), US Energy Policy Act 2003 requires the use of 3.15 Bgy of biofuel by 2005. The Renewable Fuels Standard (RFS) under EPAct 2005 mandates that a minimum of 4 Bgy of renewable fuel (largely bioethanol) must be used in the US in 2006,

14

Biodiesel science and technology

increasing to 7.5 Bgy in 2012 out of total gasoline use of 130 Bgy (2007: 143 Bgy). There is no compelling evidence that RFS (2005) has been a factor in the impact that high commodity prices have had on the economy. EPAct 2005 also demanded a 25% increase in energy efficiency by 2012. The Biofuels Initiative has called for an enhanced RFS of 35 Bgy by 2017. The US Energy Independence and Security Act (EISA) of 2007 includes a second stage of the renewable fuels standard (RFS2) that requires the domestic use of at least 500 Mgy of biomass-based diesel in the US in 2009 increasing to 1 Bgy as from 2012, and expands the minimum amount of biofuels that will be used in the US to 36 Bgy by 2022. The required total volume of renewables to be blended into the US fuel supply is 9 Bgy (2008) up to 11.1 Bgy (2009). Many questions remain as to how these volume mandates will materialise. Industry needs to expand beyond corn, which means using cellulosic biomass. RFS2 has also established three new renewable fuels categories: advanced biofuels, biomass-based diesel and cellulosic biofuels. In RFS2 terminology ‘biomass-based diesel’ is a specific title under ‘advanced biofuels’ and includes biodiesel, biomass-to-liquid diesel and renewable diesel, provided that oils and fats are not co-processed with petroleum diesel (see also Chapter 15). Up to now, and including 2009, the only commercially available biomass-based diesel available in the US in significant quantities is biodiesel. Expectations are that 500 Mgy of biodiesel for 2009 can easily be reached even if the current high volume of exports to Europe is cut back. The EPA has delayed RFS2 ruling until mid-2009. The current target set by the National Biodiesel Board (NBB) is 5% of the country’s on-road diesel fuel market by 2015, corresponding to about 9 Mt/yr of biodiesel. Analysts’ forecasts estimate a production of 15 Bgy bioethanol and 2 Bgy biodiesel in the US by 2015 (cf. 2007 figures of 6.9 Bgy and 0.45 Bgy, respectively) [21]. Bioethanol should be competitive by 2012. A US DOE goal is also to reduce the production cost of lignocellulosic ethanol from the present US$2.25/gal to US$0.82/gal by 2012 and to reduce feedstock logistics costs (harvesting, storage, preprocessing and transportation) to US$0.35/gal. The agency aims at making the fuel cost competitive to petroleum at a modelled cost of US$1.33/gal (2007 US$), thus dramatically increasing ethanol’s feedstock capacity. The DOE has also set the long-term goals of producing at least 10% of basic chemical building blocks from biomass by the year 2020 and to increase this share to 50% by 2050 [22]. The US Air Force aims at covering 50% of its fuel needs from domestic alternatives by 2016. Policy proposals for a viable US biodiesel industry comprise a tax credit as well as feedstock cost support through the Commodity Credit Corporation (CCC) Bioenergy Program; CCC is a US government entity created to stabilise farm income (Farm Bill 2002) and provides support for biodiesel and ethanol producers. The tax credit system being operated in the US is

Biodiesel as a renewable energy source

15

primarily geared to support US farmers. Despite enormous tax subsidies over the past 30 years, green sources still provide only a very small fraction of US energy. The US Food, Conservation and Energy Act of 2008 promotes advanced biofuels (cellulosic ethanol, biobutanol and biobased hydrocarbons) made from non-food crops and offers incentives to move away from corn ethanol production. The act institutes a production tax credit of up to US$1.01 per gallon of second-generation biofuels. The law encourages farmers to grow biomass crops in areas around biomass facilities, such as biorefineries, to reduce the environmental impacts of transporting fuel feedstocks. Subsidies for corn ethanol were trimmed from US$0.51 to US$0.45/gal. The US biodiesel-blender tax incentive (enacted in 2004) is presently in the form of a US$0.01 per FAME-% per gallon; this provision was to expire in 2008. For B99 biodiesel the agri-subsidy is equivalent to US$0.99/gal. This blenders’ credit makes biodiesel blends very cost competitive with conventional diesel. The US biodiesel tax credit, aimed at the producer, has not stimulated growth in consumer demand. Among the provisions of the recent Energy and Tax Extenders Act of 2008 (H.R. 6049) US House has extended the biodiesel tax credits through 31 Dec. 2009, qualifying all biodiesel produced in the US for a tax credit of US$1/gal, regardless of feedstock. A significant change to the biodiesel tax incentive is therefore the complete credit eligibility of producers using non-virgin feedstocks such as yellow grease. Previously, waste-grease biodiesel only qualified for a 50 cent per gallon tax credit. The law also shuts down the abusive ‘splash-anddash’ loophole that previously allowed foreign-produced fuel to enter the US, claim the biodiesel tax incentive, only to be shipped to a third country for end use. Fuel produced outside the US now no longer qualifies for the biodiesel tax incentive. The act also eliminates the requirement that renewable diesel be produced using a thermal depolymerisation process, and reduces the credit for biomass co-processed with a petroleum feedstock to 50 cents. The EPA established the RIN (Renewable Identification Number) system to track renewable fuel batches from the producer through various downstream entities. According to an ACS Public Policy Statement (9 Dec. 2007) the US should significantly raise its public and private sector investments in technologies to mitigate climate change through economically viable energy conservation, biomass fuel substitution for fossil fuels, carbon sequestrations and nonfossil fuel based energy sources. The Obama administration is expected to dramatically reduce the country’s carbon emissions. National biofuel programmes are operative in several other countries (e.g. Brazil, France, Sweden). The Netherlands is the only European country without a biofuels programme. Even developing countries nowadays have energy policies which include the use of locally available biofuels. For example,

16

Biodiesel science and technology

the regulatory framework for biodiesel production in Brazil is coordinated by Probiodiesel (Programa Brasileiro de Desenvolvimento Tecnológico de Biodiesel). Costa Rica intends to displace 25% of oil imports with renewable sources by 2010. According to the Philippine Energy Plan 2002–11, bioenergy is expected to supply roughly 25% of the nation’s energy needs (domestic and industrial heat generation, liquid biofuels for transport) by 2011 [23]. Asian energy policy is summarised in Table 1.4. It is important to notice that biodiesel has met all due regulatory and technical requirements, including health effect testing and creation of standards (ASTM, EN, national). Without these essential provisions in place it would not have been possible to commercialise the fuel. In this context, it is only to be remembered that circumventing the regulatory process was one of the reasons that has led to the fallout regarding methyl tert-butyl ether (MTBE).

1.2.2 Gain and pain Without initial governmental subsidies industrial production of biodiesel is not profitable because of heavy start-up costs. However, biodiesel has become more attractive recently because of its environmental benefits. The cost of biodiesel, however, is the main obstacle to its commercialisation. In Table 1.4 Asian energy policy (after ref. [24])  

Drivers

 

Regulatory

Mandates

P.R. China

Renewable Energy Legislation 2006

No

RE share 15% (2020)

India

Diversify energy sources

No

11.2 Mha jatropha (2012)

Japan

Kyoto Protocol, energy efficiency

No

6% CO2 reduction (2010)

South Korea Environmental

B0.5

B3 (2012)

Taiwan

Diversify energy sources

B1

B2 (2010); import

Thailand

Reduce imported energy products

No

B2 (2008)

Philippines

Increase farmers’ income

B2

B3 (2010)

 

Targets

Singapore National economy No

3 Mt/yr (2015); develop into major renewable diesel producer/exporter

Indonesia

9.2 Mt/yr (2025)

Diversify energy sources

No

Malaysia Environmental No

Develop into major biodiesel producer/ exporter

Biodiesel as a renewable energy source

17

the present, production and utilisation of biodiesel are generally facilitated through the agricultural policy of subsidising the cultivation of non-food crops and by tax exemptions. In the long term, however, policy decisions should just ensure a free market for biodiesel, without farm subsidies, regulations and other interventions. Several recent changes in governmental priorities should not go unnoticed. The European Union is moving towards sustainable energy and not renewable energy. Under the Bush Administration, the US has upgraded the 7.5 Bgy renewable fuels standard in 2012 to 36 Bgy by 2022 (mandatory requirement), whereas more recently, under the Obama Administration, the biofuels policy has changed focus from energy security to critical environmental issues. China changed from using food feedstocks to not using any food. Brazil started biodiesel production in 2005. In Europe, tax credits are in the form of reductions in the excise tax paid at fuel pumps, benefiting consumers rather than producers. This arrangement builds demand for biodiesel. In contrast, the US producer tax credit assists mainly in building up unnecessary production capacity. The introduction of graduated taxation of biodiesel in Germany has slumped biodiesel sales at public filling stations by a third in comparison to 2007. It would appear that a viable industry may only be so because of tax credit policy. Tax credits may have the best intentions, though the effects appear to be anything but. An energy policy is only as good as its execution. Realistic legislative targets have to be mandatory and governments need to ensure that they are met. Only Germany met the 2% 2005 target set by EU Directive 2003/30/ EC. Moreover, usage mandates do not guarantee sustainability or remedy for the feedstock crisis. Recently, the EU biofuels policy has been challenged (in particular the 10% target for the market share of transport fuels from biomass by 2020) as it had not foreseen causing social and environmental problems. Consequently, there might be a regulations rethink. It would also appear that other political intervention elsewhere has not altogether been based on entirely sound considerations. Replacing all the transport fuel consumed in the US with biodiesel will require 0.53 billion m3 of biodiesel annually at the current rate of consumption. As shown in Section 1.4.2, oil crops, waste cooking oil and animal fat cannot realistically satisfy this demand. Even the minimum renewable requirement in the US diesel pool from 0.5 Bgy in 2009 to 1 Bgy as from 2012 (according to EISA 2007) ignores the fact that acquisition of additional feedstocks beyond a biodiesel production level at 0.2–0.3 Bgy is very difficult and upsets regional markets [25]. A 0.5 Bgy US biodiesel industry, which would satisfy only 1.5% of US on-highway petrodiesel or < 1% of total fuel oil and kerosene use, would require all of the surplus vegetable oil (0.13 Bgy), half of the used oil (0.17 Bgy), and all of the oil that could be produced on 13.8 Mha of idle cropland (~ 0.3 Bgy), or the equivalent by displacing current crops. This is clearly unrealistic. The political requirement may then

18

Biodiesel science and technology

only be met by imports, which is not precisely in the best interest of a sound energy balance (see Section 14.2). Oil crops cannot significantly contribute to replacing petroleum-derived liquid fuels in the foreseeable future, unless microalgae are used to produce biodiesel. Between 1 and 3% of the total US cropping area would be sufficient for producing algal biomass that satisfies 50% of the transport fuel needs (see Section 5.7.2). An OECD recommendation [26] urges countries to end mandates for biofuel production and replace them with technologically neutral policies, such as carbon taxes that stimulate energy efficiency and a broad range of approaches to reduce GHG emissions (certification requirement). Indiscriminately increasing the amount of biofuels may not automatically lead to the best reductions in emissions. Recently, concerns have been expressed on large biofuel mandates on account of previously ignored increased greenhouse gases through emissions from land-use change [27]. Many governments are now revising biofuels policies. Ireland has lowered the 2010 biofuels target from 5.75% to 3%, citing price and emissions concerns. Also the UK’s Renewable Fuels Agency has recently recommended that the EU slows its advancement of biofuels and re-evaluates its policies, in particular taking into account the detrimental effect caused by an increase in food prices. Not surprisingly, food and consumer goods group Unilever backs recommendations to scrap mandatory biofuel targets and subsidies. Key non-technical issues that need to be addressed are creation of public awareness, biomass availability, ethical issues (use of food material for non-food; not relevant for waste oils), evaluation of environmental impacts through life cycle analysis (LCA), regulations, harmonisation of standards, taxation, etc. Biodiesel and bioethanol have already reached commercial markets, especially as blends with petrofuels. Biofuels may develop into a more locally available resource than fossil fuels, although economy of scale makes stringent requirements [28]. There is a need for long-term supply and consistency of the raw material(s) involved. The most remarkable feature of the biodiesel production market is its rapid growth (until 2007), probably unequalled in the chemicals sector. This has been driven largely by increasingly detailed political directives to achieve biodiesel substitution in petrodiesel fuel blends. More recently, however, the biodiesel industry has been victim of its own success as steep increases in feedstock prices have forced many operations (temporarily or permanently) out of the market. In March 2008 at least 20 US operations (totalling 220 MMgy capacity) were idle; in March 2009 the corresponding figures had increased to 32 operations with a total capacity of 507 MMgy. At least 15 past US biodiesel facilities (with a total capacity of exceeding 200 MMgy) are now defunct. At present, the biodiesel market is confronted with high uncertainty and volatility. Growth prospects are negatively influenced by the ongoing fuel vs. food debate, the public’s disillusion regarding biofuels, rising raw material

Biodiesel as a renewable energy source

19

prices, constantly changing regulatory environments, a slowing economy and the financial crisis restricting financing future projects. According to USDA high energy prices, increasing global demand, drought and other factors – not biofuels – are the primary drivers to higher food costs. Severe floods in the US Midwest in mid-june 2008, damaging crops, have caused a sharp rise in corn prices to a record high of more than US$7 per bushel. In the present market conditions (high vegetable oil prices) the 2010 biodiesel targets appear elusive. The end of the period of rapid growth in the biodiesel industry is creating both uncertainty and opportunities.

1.2.3 Biofuel research and development Bioproduct R&D is currently a hot topic worldwide [29], albeit with strong economic and political conditioning. Biofuel R&D has been driven by recent regulations to reduce dependence on mineral oil (US FB4P and EU Directive 2003/30/EC). The biofuels industry faces a more than 60 year R&D delay with respect to the petrochemical industry with its advanced standards of performance. However, synergies between the bioprocessing and petroleum industry might be realised. Since the end of 2003 mineral oil companies have been allowed to mix up to 5% of biodiesel with their conventional diesel. The present ratio is 2.7% (or 3.75% in Germany, 2005). Several major oil and chemical companies (e.g. BP [30], DuPont [31], Fina [32], IFP [33–38], Mizusawa [39], Petrobras [40], Petronas [41, 42], Petronic [43], Royal Dutch Shell [28, 44], Neste Oy [45–47], and others such as Chevron, ConocoPhillips, ExxonMobil, Grace Davison, Gulf Oil, HPLC, IOC, Mitsubishi, Petropar, Petroplus, PetroSun, PTT, Statoil, TotalFinaElf, UOP) are committed to alternative fuels (see Section 15.5). Whereas Total claims to be the world market leader for rape biodiesel, Grace Davison focuses on catalysts and adsorbents for purification to enhance biodiesel and bioethanol quality and is developing chromatography-based analytical and QC tools for the quality of the renewable fuels. DuPont advances biobutanol and cellulosic ethanol (corn-stover-derived). Chevron is committed to conversion of cellulosic biomass (forestry and agricultural waste) – rather than corn – into ethanol and renewable diesel and to bio-oil reforming (conversion into hydrogen). Statoil has a keen interest in marine biomass. Not surprisingly, the chemical and petrochemical industry is well aware of the concept of mineral oil as a limited resource and has taken action. After a variety of energy efficiency measures resulting in a 22% energy reduction in the past decade, Dow Chemical plans to reduce its global energy consumption by another 25% over the period 2005–15. DuPont intends to produce 25% of its products from renewable sources by the year 2010. The Dutch chemical industry aims at halving its dependence on fossil raw materials within the next 25 years (Nederlandse Regiegroep Chemie). Shell

20

Biodiesel science and technology

Oil intends providing 30% of the world’s chemical and energy needs by use of biomass by 2050.

1.3

Transformation of biomass

The term biomass means any (biodegradable) organic matter, available on a renewable or recurring basis (excluding old-growth timber), including dedicated energy crops and trees, agricultural food residues, aquatic plants, wood and wood residues, animal wastes and other (industrial and municipal) waste materials that can be used in place of fossil-fuel sources to develop value-added products such as power, heat, industrial chemicals and consumer goods [48]. Biomass, which has a complex composition, may be harvested for food, feed, energy or as a chemical feedstock (Fig. 1.4). Biomass reflects the synthesis performance of nature and has a different C:H:O:N ratio from (equally complex) petroleum. Biomass denotes a great variety of biomass types, arbitrarily divided into wet (>50%) and dry (<50%) biomass, roughly corresponding to agricultural and forestry crops. Elimination of water by evaporation greatly determines the processing costs and total energy balance. Biomass-based energy use differs greatly in various parts of the world. Zimbabwe covers 75% of its energy use with biomass (producing 40 ML bioethanol), followed by Finland, Sweden and Austria with 20, 19 and 11%, respectively. In Western countries, where land and labour are relatively expensive, the energy-crop harvest will not be as rapidly profitable Conversion Pyrolysis Gasification

Output

Combustion

Electricity

Agro products

Fermentation

Process steam

Waste products

Bio-gasification

Heat, cooling

Forestry products

Transesterification

Biofuel

Marine products

Hydrotreatment

Bioplastics

GTL

Proteins

Input

Steam/water cyclus Gas turbine

1.4 Benefits of an integrated system for conversion of combustible renewables.

Biodiesel as a renewable energy source

21

as elsewhere in the world. In any case, improved combustion, or preferably advanced gasification techniques should accompany the wider use of biomass. Processing of biomass is CO2 neutral [49]. The primary conversion processes of biomass are summarised in Table 1.5. Heating biomass (mainly wood) in the absence of oxygen at temperatures of 723–1073 K (thermolysis) up to 1773 K (pyrolysis) yields char and charcoal (at lower temperatures), an acid fuel oil, and a gas mixture, containing H 2, CO, acetylene (mainly at higher temperatures). Gasification differs from thermal conversion processes in that air and steam are used to give a product richer in oxygen (CO, CO2, H2, CH4). The product can be used for the generation of electricity or syngas. Interesting perspectives are offered by ‘biomass-to-liquid’ or BTL technology, which permits the transformation of biomass (cellulosics, wood, organic waste, etc.) into biofuels by hightemperature gasification followed by Fischer-Tropsch (see Section 15.5). Fuel production from the lignocellulosic component of biomass will be very important. Hydrothermolysis (Royal Dutch Shell) produces a low-oxygen content oil-like material (bio-crude). Anaerobic digestion evolves methane. Fermentation of glucose-based crops such as sugarcane (Saccharinum officinarum) and corn starch using Saccharomyces yeasts leads to ethanol. Most biomass technologies have not yet become competitive. A great variety of products are considered ‘biofuels’ (i.e. a liquid or gaseous fuel for transport produced from biomass), including bioethanol, biodiesel, pure vegetable oils, and others (see Section 2.2). Ethanol is by far the largest volume chemical made by bioprocessing. Biofuels often present an important advantage as compared to other alternative fuels such as LPG (liquefied petroleum gas) as no specific distribution system is needed. Direct use of unmodified vegetable oils and fats of renewable feedstocks, consisting of long-chain (mainly C12–C22) fatty acid triglycerides, as biofuel in existing engines has some disadvantages even in tropical climates (see Chapter 4). The greatest drawback of using pure vegetable oils as fuels is high viscosity, although this can be reduced by techniques such as dilution, micro-emulsification, pyrolysis and transesterification. Table 1.5 Biomass conversion processes Process

Major products

Combustion Thermolysis (723–1073 K) Pyrolysis (1773 K) Gasification (923–1473 K) Hydrothermolysis (523–873 K) Fermentation Anaerobic digestion Aerobic digestion Extraction

Heat, CO2, H2O Char, oil, gases Gases (C2H2), char CO, H2, CO2, CH4 Oil, char, gases (CO2) Ethanol, CO2 CH4, H2O CO2, H2O, heat Vegetable oil

22

Biodiesel science and technology

1.3.1 Transesterification to biodiesel Biodiesel (chemical name: fatty acid methyl esters (Fame), C14–C24 methyl esters; CAS No: 67784-80-9) is defined as a fuel comprised of monoalkyl esters of long-chain fatty acids derived from renewable lipid feedstocks, such as vegetable oils or animal fats, for use in compression-ignition (diesel) engines [50]. Biodiesel is not a single chemical entity. In 2003, US Congress proposed that, for tax purposes: ‘The term “biodiesel” means the monoalkyl esters of long-chain fatty acids derived from plant or animal matter which meet (a) the registration requirements for fuels and fuel additives established by the Environmental Protection Agency under section 211 of the Clean Air Act (42 U.S.C. 7545), and (b) the requirements of the American Society of Testing and Materials D 6751’. On this basis, biodiesel is not crude vegetable oils, oil/diesel or alcohol/diesel binary mixtures, microemulsions, biomass pyrolysates, vegetable oil pyrolysates (bio-oil), or alcohol/diesel/co-solvent ternary mixtures. A later EPAct05 biodiesel definition includes two types of biodiesel: traditional fatty acid methyl esters (bio-esters) and non-ester renewable diesel (NERD or bio-alkanes). In this text ‘biodiesel’ is used exclusively in the more restricted bio-ester sense. Biodiesel, which is a clear, amber-yellow liquid, is used pure (B100) or preferably as blends (B5, B20) with petrodiesel. Biodiesel is usually compared to petrodiesel No. 2 (DF2), which is characterised by a 453–613 K boiling range. Petrodiesel is a fraction boiling in the mid-range of cracking products, also termed ‘middle distillates’. As the viscosity of the biodiesel fuel (BDF) is approximately twice that of petrodiesel it has better lubricating properties. Biodiesel is commonly added to the petrodiesel sold at pumps today to increase the lubricity of pure ultra-low sulfur diesel (ULSD). Industrially, biodiesel (consisting of mixtures of medium- to long-chain fatty acid alkyl esters, mainly methyl esters: FAMEs) is produced by relatively complex (catalytic) alcoholysis (transesterification) of vegetable oils and animal fats. This process is more typical of the chemical industry than of the petrochemical industry. Simple fatty acid alkyl esters produced from renewable feedstocks such as oils and fats are being investigated in numerous settings as replacements for petroleum-derived materials, particularly diesel fuel. Requirements for economic exploitation are cheap raw materials and low process costs (low T, p, t, quantitative conversion); see Chapters 7–12. The transesterification yield is high: 1 t vegetable oil yields about 1 t biodiesel and 110 kg glycerol, but requires 110 kg methanol, catalysts and neutral reactants (see Fig. 5.2). However, the yield is less impressive if one considers the whole life cycle. Generation of 1 t biodiesel typically requires cultivation of about 1 ha, which yields 9 t product; of these 6.5 t are currently not valorised (stalks, roots, leaves) and only 2.5 t are oilseeds. Oil is extracted from the oilseeds by trituration, pressing and/or solvent

Biodiesel as a renewable energy source

23

extraction. For each ton of oil 1.5 t of solid residue is obtained which can be used as animal feed (see also Fig. 3.7 and Fig. 5.2). One of the first uses of transesterified vegetable oil was powering heavy-duty vehicles in South Africa before World War II.

1.3.2 Alternative diesel fuels Other processes can also be used to produce high-quality diesel fuel from vegetable oil or animal fat. Less appropriately, pyrolysis and hydrogenation products, diesel-vegetable oil blends, microemulsions of alcohols and water in vegetable oils and fermentation butanol are sometimes also referred to as biodiesel; in fact, they are just alternative (renewable) diesel fuels. For use as diesel fuels vegetable oils and animal fats with high viscosity and low volatility must be modified in order to gain sufficient engine compatibility. Viscosity values of vegetable oils typically vary between 27.2 and 53.6 mm2/s, whereas those of vegetable oil methyl esters are between 3.59 and 4.63 mm2/s. Apart from transesterification with low alcohols (MeOH, EtOH) various other processes exist to improve the fuel combustion characteristics of biomass (in particular vegetable oils and fats) by reduction of viscosity: ∑ blending (dilution) of vegetable oil with other fuels (diesel, alcohols); ∑ microemulsification with short-chain alcohols (MeOH, EtOH); ∑ thermal treatment (pyrolysis, gasification) producing alkanes, alkenes, carboxylic acids and aromatic compounds; ∑ catalytic cracking to (cyclo)alkanes; ∑ hydrotreating; and ∑ ozonation. Among these primary technologies only dilution, microemulsification and heating do not chemically alter the raw material. Co-solvent blending of vegetable oils with other fuels like alcohol may bring the viscosity to within specification. Microemulsions cannot generally be recommended for long-term use in diesel engines (see Section 4.3). The development of stable bio-crude oil (BCO)/diesel oil emulsions is under way [51, 52]. Pyrolysis is a thermochemical conversion process in conditions of significantly less oxygen than required for complete combustion, which offers a way to convert (solid) biomass into an easily stored and transported liquid or bio-oil for use in producing chemicals and fuels [53]. Torrefaction is a mild form of low-oxygen pyrolysis (573 K) producing biomass without moisture and volatiles. In pyrolysis, the feedstock is subjected to moderate-to-high temperatures in the absence of oxygen and degrades to a liquid (preferred product), gaseous and solid phase. The product distribution depends on biomass composition and pyrolysis conditions (T, ΔT, t). Table 1.6 shows

24

Biodiesel science and technology

Table 1.6 Pyrolysis modes         Method

Residence time (tr)

Temperature Heating rate Product(s) (K)

Torrefaction Carbonation Conventional Slow Fast Flash liquid Flash gas Hydropyrolysisb Ultrafast Vacuum pyrolysis

< 90 min Days 5–30 min > 1 s 0.5–5 s < 1 s < 1 s < 10 s < 0.5 s 2–30 s

473–573 673 873 773 923 773 > 973 <773 1273 673

a

Low Very low Low Low Medium High High High Very high Medium

Biomassa Charcoal Oil, gas, char C (30%) Bio-oil Bio-oil (80%) Gas Bio-oil Chemicals, gas Bio-oil

Without moisture and volatiles.       Pyrolysis with water.

b

various pyrolysis conditions and main products. Pyrolysis modes are flash or ultrafast (up to 1000 K/s with rapid condensation of vapour products), fast (300 K/min) and slow (30 K/min), all usually up to 773–873 K. Processes can be adjusted to favour charcoal, pyrolytic oil, gas or methanol production with a fuel-to-feed efficiency up to 95%. Slow heating rates tend to favour production of volatile gases, organic acids and aldehydes, mixed phenols and char. High heating rates tend to minimise char formation and liquid production and maximise gas production. Pyrolysis can be used for the production of bio-oil by various processes (e.g. flash pyrolysis) [53–56]. The yield of pyrolytic liquid, also known as bio-oil, depends on pyrolysis conditions, including relatively short residence times tr (0.5–2 sec.), moderate temperatures (673–873 K), and rapid quenching at the end of the process. The multi-component liquid is highly oxygenated, and contains up to 15–20% water. The elemental composition of bio-oil resembles that of biomass (cellulose, hemicellulose and lignin) rather than that of petroleum oils. Fast pyrolysis technologies for energy application have recently entered the stage of commercialisation (25 kt/yr; DynaMotive, West Lorne, Canada). Bio-crude oil (BCO) use for power and heat production represents a main goal in the biomass sector. BCOs have already been used in modified diesel engines (see Section 4.2). Their use in internal combustion engines offers several advantages in terms of logistics (compared to bio-energy from solid biomass) as well as in terms of power-to-heat ratio and efficiency. Direct use of pyrolysis oils requires significant adaptations of technology to fuel characteristics. Other problems with bio-oil include high corrosivity. The biomass pyrolysis-to-energy chain is not yet fully developed. The pyrolysis technology that is closest to commercialisation is the pyrolysis of high lignin-containing lignocelluloses. Ensyn (Canada)’s Rapid Thermal Processing (RTP) can use sawmill residuals and construction and demolition

Biodiesel as a renewable energy source

25

wood waste as well as fast-growing wood species such as willow and poplar, liquefying 75% of the original in a fast pyrolysis process to ‘bio-oil’. Pyrolysis and cracking of oils and fats produce compounds that are smaller than triglyceride molecules and are, therefore, more suitable as a fuel. In petroleum refining hydrocracking is widely used for converting various fractions to lighter and more valuable products, especially distillates such as jet fuels, diesel oils and heating oils. Ester-containing vegetable oils have been converted into hydrocarbons by pyrolysis at 573–973 K in the presence of a catalyst [57]. Pyrolysis or thermal catalytic cracking has been applied to various oilseed feedstocks, including soybean [58, 59], rapeseed [60, 61], tropical vegetable oils (babassu, piqui, palm, copra) [62, 63], tung oilseeds [64], soybean oil cake [65] and sunflower oil cake [66]. Pyrolysis and hydrocracking of SBO, hydrogenolysis of palm oil (PMO) and rapeseed oil (RSO), and hydrocracking of SBO and babassu oil were reviewed by Dunn [67]. Cracking of canola oil (used as a model compound for waste vegetable oils) to fuels and chemicals at 673–773 K using a variety of catalysts yields mainly C1–C5 hydrocarbon gases, liquid aromatics and aliphatics, and coke [68]. Da Rocha Filho et al. [69] studied catalytic hydrocracking of vegetable oils obtained from Passiflora edulis (maracuja), Astrocaryum vulgare (tucuma), Mauritia flexuosa (buriti), Orbignya martiana (babassu) and soybean. In catalytic cracking of triglycerides (TGs) using a variety of catalysts, including SiO2/Al2O3 [63], NiMo/g-Al2O3 [69], Ni/SiO2 [70], Al2O3 [71], MgO [71], zeolites [72-74], a gasoline-like fuel is more likely to be formed than a diesel-like fuel. Bio-oil was obtained in tubular reactor fixed-bed hydropyrolysis experiments from extracted Euphorbia rigida at a hydrogen pressure of 15 MPa at 823 K [75]. The main shortcoming of such biofuels lies in the economics of the process with the use of expensive vegetable oils as new raw materials. Pyrolysis of vegetable oilseeds avoids the complicated and expensive extraction step [60]. Some drawbacks of pyrolysis are: ∑ use of tremendous amounts of heat; ∑ production of a wide range of compounds due to low selectivity; ∑ removal of oxygen from substrate molecules (thus eliminating one of the benefits of oxygenated fuels); and ∑ creation of solid residues of ash and carbon, thus requiring additional separation steps. Vegetable oils and animal fats can be hydrogenated catalytically under formation of a product that can be used as a commercial fuel (see Section 15.4). Finnish Patent No. FI 100,248 to Aalto et al. (to Neste Oy) [76] describes a two-step process for producing middle distillate from vegetable oil by hydrogenating fatty acids of vegetable oil or triglycerides, to give n-paraffins, and then branched-chain paraffins by isomerising the n-paraffins.

26

Biodiesel science and technology

Neste Oy has recently commercialised a renewable diesel process based on hydrotreated vegetable oils (HVOs) and animal fats [45, 77] (see also Section 15.4.1). US Patent Appl. No. 2006/0207166 A1 to Herskowitz et al. [78] describes a one-step hydrodeoxygenating/hydroisomerising process for producing a low-sulphur diesel fuel composition (mixture of C14 to C18 (iso)paraffins) from vegetable and/or animal oil using a dual-functional Pt/ SAPO-11 catalyst at 643–683 K at 2–4 MPa. Hydrocracking was inhibited. Composition and fuel characteristics of the produced diesel may be adjusted by varying the vegetable and/or animal starting product, process conditions and catalyst used. Paraffinic diesel fuel compositions provide superior fuel properties, especially for low-temperature performance (e.g. density, viscosity, cetane number, lower heating value, cloud point and CFPP), to FAME biodiesel. US Patent No. 6,364,917 B1 to Matsumura and Murakami [79] discloses a method of converting virgin plant oils and/or waste vegetable oils into (diesel) fuel, by heating the oil, mixing the oil with water and/or ozone and agitating the mixture of oil and water dissipating the ozone. Ozonation (aeration with ozone-oxygen mixed gas) at close to normal temperature (313–353 K) involves no other chemicals aside from ozone (i.e. electrical power) and readily allows transformation of waste oils and requires low plant construction costs. The end product has lower average molecular weight than petrodiesel as a result of formation of ozonides (1,2,4-trioxolane rings) and bond rupture in the fatty acids composing the vegetable oil (i.e. aldehyde formation) [80]. Obviously, the chemistry of the resulting fuel differs totally from that of hydrotreating, pyrolysis or transesterification technology. As ozonation hardly produces any post-refining waste matter it thus shows remarkable efficacy as a recycling system.

1.4

Global biodiesel development

The usage of biodegradable fuels from renewable agricultural oils and fats represents only a small fraction of the market for industrial products in developed countries. Global production of biofuels has developed from about 15 Mt in 2000 (biodiesel 0.7 Mt; bioethanol 14.4 Mt) to 40.7 Mt in 2005 (biodiesel 3.7 Mt, bioethanol 37.0 Mt) (Table 1.7), compared with 1.2 Bt of gasoline. Main biofuel producers were US (14.0 Mt) and Brazil (14.1 Mt). US bioethanol production figures have recently increased steeply from about 8.9 Mt in 2001/02 and 16.6 Mt in 2006 to 23 Mt (or 0.45 Mbd) in 2007, putting the farm system into a high state of alarm by using 27% of the entire corn crop production [81]. Nevertheless, even this record level still replaced only about 5% of the US total gasoline consumption. IEA estimates foresee a 2008 world biofuel production of 1.35 Mbd (70 Mt/yr), which is expected to rise to 1.95 Mbd (100 Mt/yr) by 2013.

Biodiesel as a renewable energy source

27

Table 1.7 Biofuels production (2005) Country

Production (ML)

US Brazil P.R. China India EU Others Total

16 130 15 990 3800 1700 3100 5480 46 200

Brazil (191.8 M population) has one of the most advanced biofuels programmes in the world with over 30 000 filling stations offering pure hydrous ethanol as well as gasoline with a mandatory blend of E20 to E25. Brazilian bioethanol takes up half the country’s sugarcane crop. Brazil has been world leader in E95 (azeotropic bioethanol) and E25 for the last 25 years. ‘Flex-fuel’ vehicles (FFVs; Brazil, USA, Sweden) allow use of E85. In Brazil 60% of all new cars run on a fuel mix made up of 85% bioethanol. Brazil has recently started biodiesel production. EU25 is the main biodiesel producer but also generates small amounts of bioethanol (491 kt in 2004), mainly in Spain, France, Germany and Sweden from wheat (50%), barley (20%) and sugar beet (30%), with a forecast of 640 kt for 2008. Ethanol is generally used in gasoline as ethyl tertiary butyl ether (ETBE). Biofuels of minor production were neat vegetable oils (Austria, Germany) and biogas (Sweden). Diesel fuel is largely utilised in road, rail and sea transport, agriculture, and commercial, domestic and industrial sectors for the generation of power and mechanical energy. Today’s biodiesel industry is about 20 years old. In 2005, biodiesel contributed only about 1.8% of the EU diesel fuel consumption and just over 0.2% of that in the US. Although its potential has initially been held back by legislation, fiscal and duty structure, blending technology, learning curve and interested parties, today the industry is growing fast with an expected production of 11.1 Mt in 2008 [82]. This figure may be compared with a world production of about 130–135 Mt of vegetable oils (2007). In particular, the first-generation biodiesel markets in Europe and the US have reached impressive biodiesel capacity levels but are constrained by feedstock availability. Global biodiesel production in 2007 was mainly derived from RSO (4.6 Mt), SBO (2.1 Mt) and PMO and other vegetable oils and animal fats (<2.0 Mt), with the EU being the main biodiesel manufacturer (66%). Only five years ago, Europe was the dominant player in the biodiesel industry, accounting for more than 83% of the global installed capacity and 93% of world biodiesel production and consumption. By 2007 the European share had declined to about 46%, with North America and Asia accounting for 23% and 19% of world biodiesel capacity, respectively [83].

28

Biodiesel science and technology

Diesel fuel consumption and market share are expected to rise significantly in North America, as well as Eastern Europe and in developing Asia. International regulations promote biodiesel growth [84]. Biofuels have been successfully implemented only in those countries that have recognised the benefits and have undertaken appropriate policy actions to support biofuels. The extent to which biodiesel has entered the marketplace varies significantly by country. Biodiesel is usually blended with petroleum diesel to make biodiesel blends; B100 is pure FAME, while B20, B5 and B2 are fairly common blend levels. Low-level blending is the easiest and cheapest way for marketing biodiesel. The distribution of B5 requires negligible investments in distribution systems and no different pumps or labels. Most oil companies are therefore prepared to support low-level blends more than B100, which requires higher investments. Pure biodiesel (B100) requires entirely separate logistics and a dedicated car fleet. Some 400 000 cars in Germany, Austria and Sweden use B100. Biodiesel is sold in unblended form directly to freight forwarding companies, and to mineral oil dealers. The European diesel quality standard EN 590 does not allow using FAME blends exceeding 5% with diesel. The 5% biofuel blending cap only applies for consumer vehicles. Others, such as fleets, can come to individual agreements with their vehicle manufacturers. For example, in 2007 UK retailer Tesco was running its delivery fleet on B50 and UK’s McDonald on B100; Scania trucks allow for B100. Similary, Safeway (USA) uses B20 in its fleet of more than 1000 trucks. Also Eastman Chemical Co. is fueling its locomotive fleet, heavy-duty vehicles and equipment at Kingsport, TN, with B20. Low-level B5 blending is not sufficient to meet the 2010 targets for biofuels. This dilemma can be overcome by: alteration of the fuel standards for diesel to allow blending of B10, or promotion of the diffusion of high-level blends (requiring flexi-fuel vehicles). The escalation in crude oil prices since 2005 up to and beyond US$100/ barrel (Fig. 1.5) – doubling from US$69 in June 2007 to US$147 in June 2008 – and way up from the 1991 level of US$20 determines in principle a favourable marketing opportunity for biodiesel and other alternative energy sources. Commercial biodiesel is usually obtained by transesterification of crude or more expensive high-quality VO raw materials or blends of different types of VOs, in relation to (limited) market availability in order to achieve the final desired properties of the fuel (oxidation stability, iodine number). Apart from production costs, development of the biodiesel industry depends on several non-technological factors, including feedstock prices and market availability, crude oil prices, and taxation of energy products. The extremely high global energy prices have driven up feedstock costs for many products. For example, European RSO prices have increased from US$480/t (exchange rate 7/US$: 1.10) in 2003 to US$670/t (exchange rate 7/US$: 1.20) by the end of 2004, and even higher more recently (see Fig. 14.9). Consequently,

Biodiesel as a renewable energy source

29

95 90 85 80

US$/barrel

75 70 65 60 55 50 45 40 2005

2006

Year

2007

2008

1.5 Crude oil price per barrel.

the market cost of biodiesel remains higher than that of petroleum-based diesel despite the fact that between April 2007 and April 2008 the price of No. 2 diesel in the US increased by 35% (with an increase of 52% from Apr. 2005–08). Refined vegetable oils, especially RSO in Europe and SBO in the US are the most common feedstocks for biodiesel production. These raw materials are traditionally more expensive than palm oil (see Figs 5.1, 14.9 and Table 5.9). Favourable taxation in Europe has allowed biodiesel to achieve approximate cost parity with conventional diesel. Based on 7.7 lb of soybean oil (at US$0.22/lb; 2003 level) required for 1 gal, up to 91% of the product cost of biodiesel is accounted for by the feedstock. With processing costs ranging from US$0.15 to US$0.50 per pound, operating cost and capital cost represent about 3–4% and production cost some 5–6% [85]. As biodiesel made from refined SBO makes difficult competition with petroleum-derived diesel fuel, this calls for use of lower value lipids. For palm oil sourced biodiesel to be competitive with petrodiesel the price of crude palm oil should not exceed US$1.82/gal, assuming absence of tax on biodiesel. This price level has recently been exceeded. Transesterification of palm oil adds about US$0.53/gal to the price of the oil. Use of low-cost feedstocks, such as non-edible oils or waste frying oils,

30

Biodiesel science and technology

help make biodiesel competitive in price with petroleum diesel [86]; some industrial plants exploit recycled cooking oil as a feedstock (see Tables 1.8, 11.7 and 14.21). Prices (2003) per pound are lower for inedible tallow (US$0.14), mustard oil (US$0.10), yellow grease (US$0.09) and brown or trap grease (US$0.05). While fuel quality is not greatly affected, there are concerns that pour point could be increased by using such lower quality feedstocks. Moreover, a higher free fatty acid content makes processing more expensive. In case of use of waste materials, logistics of collection and availability are limiting factors, as always in recycling. Biodiesel production using the transesterification process is also being limited in several countries because of an excess supply of the by-product glycerol.

1.4.1 Rape biodiesel Biodiesel fuel was first commercially produced in a pilot plant in Silberberg (Austria) in 1985 [87]. Already in 1997 biodiesel development had been identified in 28 countries with a worldwide capacity of some 1.2 Mt/yr [88]. Meanwhile world biodiesel production is rapidly expanding from 2.7 Mt in 2003 (60% EU share) to 7.1 Mt in 2006 (69% EU share). Different countries adopt different solutions. Table 1.8 shows the status of biodiesel production in several countries. At the moment, 35–40% of Europeans drive diesel cars. Diesels reached a 53.3% share of new car registrations in Europe in 2007. On the other hand, only about 3% of US passenger vehicles now run on diesel although the US light-duty diesel market share is expected to increase to 6.9% by 2012 and 14.4% by 2017 [89]. Total diesel consumption in the EU (2005) amounted to 170 Mt, and continues to expand (see Fig. 1.2). There is a predicted shortage of EU mineral diesel refining capacity. The EU could be 20% short of its mineral diesel needs by 2015. The continuing trend of increasing diesel car ownership and increasing need for imported diesel while gasoline demand is decreasing (Fig. 1.2) ensure that biodiesel is an important contributor towards Europe’s energy security strategy. Biodiesel is being produced on an industrial scale in the EU primarily as rapeseed methyl ester (RME). Whereas in 2003 only nine member states produced biodiesel (with 89% being produced in Germany, France and Italy), in 2007 almost all member states are producers (see Table 14.31). The EU27 (as the world’s leading producer) reported a production of over 4.9 Mt/yr of biodiesel in 2006 in comparison with 3.2 Mt in 2005 (+54%), after a 65% record growth in 2005 over 2004 (Fig. 1.6). While production was beyond expectation (see Table 1.2), the biodiesel target (EU Directive 2003/30/EC) was not respected by all member states. In the past, total EU nameplate biodiesel capacity has not been used to its full extent (2.4 Mt vs. 1.8 Mt production in 2004). Although the EU biodiesel industry is in a good

Table 1.8 Status of biodiesel production in selected countries       Country Reference year

Number of production plants

Nameplate Feedstock Domestic crops production (cropland) capacity (kt/yr)  

a

70 400 1500–1800 1400 1400 570 – f

n.g. n.g. n.g.

n.g. n.g. n.g.

31

Assuming 1 t/ha for rapeseed. Production quota. c Under construction. d Expansion. e Including 1 310 kt/yr unconfirmed capacity. f 1.3 billion dry t/yr of biomass; vast surplus of capacity resources. g Total cropland area: 455 M acres. h Total cropland area: 150 Mha. b

RSO (70 kha) RSO (n.g.) RSO (1.2 Mha) RSO (1.4 Mha) RSO, import RSO (570 kha) – SBO (73.0 M acres) CRO (68.8 M acres) CSO (13.8 M acres)g CO (15.5 M acres) SBO (15 Mha), (SNO) SBO (23 Mha) CRO (14 Mha) CSO (0.2 Mha) PNO (0.1 Mha)h SBO (n.g.) Import PMO (3.75 Mha)

Biodiesel as a renewable energy source

Austria 2007 11 326 RSO, UCO, (SNO) Czech Republic 2007 17 203 RSO, UCO, (SNO, SBO) France 2007 8 1450 RSO, SNO, SBO Germany 2006 39 3603 RSO, PMO, SBO, UCO Italy 2006 11 857b RSO, SBO, SNO UK 2007 n.g. 657 UCO, TLW, RSO, SBO Netherlands 2008 8 571 RSO, SBO, PMO, SNO US Sept. 2008 165 (+12c+1d) 8840e (+1 160c) SBO, UCO, (RSO, CSO, TLW) Canada 2009 9 216 CO, TLW, UCO Argentina 2010 33 3697 SBO Brazil 2008 51 2058 SBO, CSO Australia 2008 n.g. 500 RSO, SNO, SBO, TLW, UCO P.R. China 2007 n.g. 200 RSO, PMO, CSO, UCO Malaysia 2008 12 1500 PMO

Maximum domestic oil potential (kt/yr)a

32

Biodiesel science and technology 6000

5000

Germany France Italy

4500

Total

5500

EU27

Others EU

EU27

4000

kt/yr

3500

EU25

3000 2500 EU15

2000 EU15

1500

EU15

1000 500

EU15 EU15

0 1998

2000

2002

2003

2004

2005

2006

2007

1.6 Biodiesel production in EU and member states (Source: European Biodiesel Board).

position to be able to fulfil the 2010 EU biofuel target in terms of capacity, expectations as to production are stagnating or may even decline as from 2007. Table 1.9 shows the growth in German biodiesel production capacity over the period 2000–07, which has recently increased considerably and accounts for about a third of the European capacity in 2008 (see Table 14.31). Today there are some 40 small to industrial-scale plants in Germany alone, using RSO as 90% of total feedstock. Since fuels in Germany are taxed according to carbon emissions, with biodiesel enjoying a healthy tax break, production has long been competitive with diesel fuel. In the recent past, almost 2000 filling stations throughout Germany offered biodiesel at their pumps. On the basis of fossil diesel road consumption (25.5 Mt in 2001; annual increase of 2%) and considering that 700 kha rapeseed cultivation yields 1 Mt biodiesel, Germany requires at least 450 kha of rapeseed oil cultivation for biodiesel production alone in 2005 and 1.3 Mha in 2010 in order to meet the EU targets (of 2% in 2005 and 5.75% in 2010). However, due to new legislation (the biofuels quota act and energy tax act), leading to loss of the tax credit, and the recent steep increase in vegetable oil prices, biodiesel growth in Germany has slowed down. With massive B99 exports

Biodiesel as a renewable energy source

33

Table 1.9 Biodiesel production capacity in Germany Yeara Number of producers    

Plant capacity range (kt/yr)

Total capacity (kt/yr)

Production (kt/yr)

2000 2001 2002 2003 2004 2005 2006 2007

2–100 2–120 2–120 2–120 2–120 2–180 2–425 n.d.

340 506 849 1105 1237 1973 3603 4361

265 450 550 700 1064 1669 2662 2890

6 11 17 25 27 30 39 n.d.

Source: Union zur Förderung von Oel- und Proteinpflanzen e.V. (UFOP). End of year.

a

from the US to the EU, about 75% of Germany’s biodiesel production capacity now lies virtually idle. In the UK sales of biodiesel amounts to 20 kt/yr (2005) compared to total diesel sales of approximately 22.4 Mt/yr. Biodiesel thus makes up less than 0.1% of total UK diesel sales and less than 0.04% of total combined petrol and diesel sales. Taking into account exported wheat and set-aside farm land, the UK could produce a maximum of 5% of its current (2007) transport fuel requirement. France has adopted more ambitious objectives than the European Commission for biofuel incorporation into conventional fuels. Expected French biodiesel production is 1.45 Mt by 2008, out of a projected French consumption of 35 Mt of diesel and 10 Mt of gasoline in 2008 [90]. One third of Italian territory (10 Mha, or almost the total agricultural area) would be needed for rapeseed cultivation to attain production equivalent to 10% of total domestic petroleum product consumption.

1.4.2 Soy biodiesel Only 6% of US energy (2006) comes from renewable sources (including hydropower and wood) with no more than 1% from wind, solar and biofuels. US consumption figures for 2007 are 143 Bgy of gasoline and 63 Bgy of diesel and distillate fuel. The high consumption of petroleum transportation fuels in the US (522 gal per capita in 2001), far in excess to that of other most developed countries (Germany 211 gal, Japan 196 gal), suggests an impelling need for more energy efficiency and massive conversion from gasoline-powered cars and light-duty trucks to cleaner-burning diesel vehicles. However, there is only limited support from the car industry for consumer diesels in the US. This might change following the 2008 financial crisis and the election of the Obama administration.

34

Biodiesel science and technology

Much of the early support for biodiesel in the US came from the American Soybean Association, which implemented a soybean checkoff programme in 1991 and funded biodiesel research. Biodiesel has been registered with the EPA as a fuel and a fuel additive under Section 211(b) of the Clean Air Act. Biodiesel is available only at around 1650 retail filling stations across the US (as at Oct. 2009). The Soyatech Biofuels Index monitors development of biofuels production capacity [91]. One of the driving forces behind the development of the biodiesel industry was a glut of virgin oils such as soybean and rapeseed (canola) oils on the market only five years ago. The main reason that biodiesel has not gained wider acceptance in the US in the past is the consistently much higher retail price of biodiesel relative to petrodiesel (see Fig. 1.7). In fact, the price of soybean oil, before esterification, was even higher than that of the final competing product, petrodiesel. In 2006, the on-highway petrodiesel price ranged between US$2.50 and US$3.00/gal, reaching US$4.00/gal in June 2008 (but averaging US$2.19/gal in Feb. 2009). This price includes taxes (20%), cost of crude oil (52%), refining expenses (19%), distribution and 3.0 Biodiesel (medium) Base diesel 2.5

1.5

1.0

0.5

3

2 l-0

pr -0 A

1 Ju

-0 ct

01

O

n-

0

Ja

9

pr -0

l-9

A

-9

8 Ju

ct

98

O

7

Ja

n-

6 l-9

pr -9 A

-9

5 Ju

ct O

n-

95

0.0 Ja

US$

2.0

1.7 Comparison of price per gallon (no tax) of diesel fuel vs. canola biodiesel (after ref. [92]).

Biodiesel as a renewable energy source

35

marketing (9%). Excluding taxes and distribution the average 2006 price for petrodiesel was therefore US$1.85/gal (crude oil 73%, refining 27%). Biodiesel blends are relatively competitive with a premium of 6.2 and 24.9 cents/lb for B5 and B20, respectively. High oil prices were once expected to trigger a major increase in soy biodiesel in the US. In the past, the corresponding demand for soybean oil could easily be accommodated in view of an existing soybean surplus situation and idle production capacity. The resulting expected economic impacts of biodiesel were estimated as an increase of US$0.10 to US$0.18 to the price of soybeans at a demand for 70 Mgal of soy biodiesel [93]. However, in practice the world market prices of vegetable oils are even more strongly influenced by the increasing need for foodstuff oils of developing countries (P.R. China, India). In recent years the price of virgin oils has been pushed up from about US$0.20/lb to US$0.60/lb and beyond (see Table 14.20). While the US still enjoys low fuel prices relative to Europe, US diesel sales have begun an upward trend. The US consumer diesels are expected to be on the verge of an increase in market share. As shown in Table 1.10, vegetable oil crops cannot realistically satisfy US (or indeed global) demand for fuel consumption. The combined vegetable oil, animal fat and grease production in the US of 21 Mt/yr (2006) could at most provide 6.0 Bgy of biodiesel. Consequently, biodiesel based on these resources can only ever replace a small fraction of the petroleum-based diesel fuel in the US. Although markets in key bioproduct areas (mainly bioethanol) are expected to expand considerably, biomass now accounts for no more than 3% of US energy needs [94]. Corn-derived bioethanol contributes about 3.6% to the total transportation fuels mix (2007). Bioethanol from corn is not a real solution to the US transportation fuel problem (see Section 1.4). Lately, the US government is actively encouraging production of biodiesel Table 1.10 Comparison of some sources of biodiesel (after ref. [95]) Crop  

Oil yield (L/ha)

Land area needed (Mha)a

Percent of existing US cropping areaa

Corn Soybean Canola Jatropha Coconut Oil palm Microalgaeb Microalgaec

172 446 1190 1892 2689 5950 136 900 58 700

1540 594 223 140 99 45 2 4.5

846 326 122 77 54 24 1.1 2.5

a

For meeting 50% of all transport fuel needs of the US. 70 wt% oil in biomass. c 30 wt% oil in biomass. b

36

Biodiesel science and technology

as an alternative to petroleum-based fuels by subsidies which stimulate production but not domestic consumption (see Section 1.2.1). US biodiesel production is rapidly gaining momentum (Fig. 1.8) and has grown from a mere 0.5 Mgy (1999), directed to niche markets, to 7 Mgy (2000) and to over 25 Mgy (2004). The 2004 production did not exceed 0.1% of total diesel consumption for transportation purposes (39.9 Bgy in 2003). US production in the period 1999–2004 was indeed a very small fraction of European production [96]. Meanwhile, biodiesel sales volumes developed from 250 Mgy in 2006 (with a 230% increase from 2005) to 450 Mgy (1.5 Mt) in 2007 [97], and beyond. The biodiesel-blender tax incentive (recently extended up to 31 Dec. 2009) has been instrumental in the rapid growth of the US biodiesel industry and has been responsible for exports to Europe (1 Mt in 2007). The Energy Independence and Security Act 2007 calls for more biodiesel usage, from 0.5 Bgy (2009) to 1 Bgy (2012). Biodiesel plants increased from 88 to 178 units from 2006 to Sept. 2008 (31 idle, 12 under construction, 1 under expansion; 21 unconfirmed). At least 113 US plants (with total nameplate capacity of 1853 MMgy) are continuing to produce biodiesel (24 Sept. 2008), but at below 40% production capacity [98]. Additional manufacturing plants

700

600

Mgal

500

400

300

200

100

0 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Year

1.8 US biodiesel production.

Biodiesel as a renewable energy source

37

are being built to accommodate further growth, now at a slower rate than expected in the past [99]. In the near future a combined production capacity of 3.0 Bgy is expected (see Table 14.36). While it was expected in 2002 that US production might be upgraded to at least 350 Mgy by as late as 2011, with incentives comparable to those provided for ethanol, US biodiesel sales could then actually easily reach 1 Bgy, all greatly depending on oil prices. This production volume would upset glycerol markets. US producers use mostly soy oil and recycled cooking oils. US options for additional feedstock supply are several: SBO (reducing exports), oil-rich oilseeds (e.g. canola), palm (imports), mustard, camelina, algae and jatropha (under development). Canola would be the lower cost feedstock of biodiesel production compared to soybean and sunflower. However, because of the value of its co-products (e.g. meal), soybean results in a lower production cost for biodiesel than canola. Consequently, soybean oil continues to dominate the US market as feedstock to biodiesel. In 2007, 12% of US soybean production (4% of global soybean production) was used by the US biodiesel industry to produce fuel, exceeding total US soy oil exports. In a tight market this is sufficient to raise prices. The US is currently characterised by high soybean prices and idle plants virtually next to fields of soybean that biodiesel producers cannot afford. Soy prices are likely to drop in 2009. Total consumption of soy oil for food use has decreased nearly 1 billion pounds over the last three years in the US. Argentina is another important soy biodiesel producer and exporter (see Section 14.6.4).

1.4.3 Tropical oil crop biodiesels Today only a few percent of global transportation fuels are derived from biomass and are produced either by fermentation of food-derived carbohydrates (e.g. sugar or cornstarch) to ethanol or by processing of plant oils to produce biodiesel. Except for Brazil, where favourable agricultural conditions and a flexible processing infrastructure allow the majority of the country’s road transport to be powered economically with cane-derived ethanol, without mandates or subsidies biomass derived fuels are not economically competitive with fossil fuels even at crude oil prices of US$150/barrel and at correspondingly high vegetable oil prices. Brazil needs some 534 M barrels/yr, or 85 Mt/yr. The Brazilian diesel oil consumption (2003) amounts to about 40 Mt. Estimated domestic biodiesel need in Brazil will be about 800 kt in 2008 (mandatory B2 blend) up to 2.5 Mt in 2013 (at B5 mandate). This requires 8–25 100 kt/yr plants. Installed capacity is increasing rapidly from 50 kt (2005) and 600 kt (2006) to 2 Mt (2007). Brazilian biodiesel production has just started, using mainly soybean oil, but many other options are being considered and implemented (SNO, CSO, PMO, jatropha, castor). Brazil’s initial involvement in biodiesel

38

Biodiesel science and technology

production (by ethanolysis of SBO) is clearly too restrictive. The regulation of biodiesel production in Brazil does not limit the use of vegetable oils [100]. Babassu palm (17 Mha) could produce at least 20 Mt oil/yr. The country could easily become a major renewable fuel supplier, both for bioethanol and biodiesel. Palm diesel has been established as a diesel substitute since 1996. Malaysia is the second largest producer of palm oil and operates a 500 kt/yr biodiesel plant (2003). Malaysia intends to utilise crude palm oil and RBD palm oil (olein) at 5–10% blend level directly, or as palm diesel, as industrial and transport fuels, also in order to achieve price stabilisation of the palm oil market during periods of high stock levels. Malaysian palm oil methyl ester was already used in 1987 as biodiesel in buses. With a limitation in the CFPP of 284 K, this type of biodiesel faces a major obstacle in colder climatic conditions, where it may be used in multi-feedstock mode. The use of coconut biodiesel is being tested by the Philippine Coconut Authority. In Thailand various mixes of CNO and PMO blended with diesel oil have been introduced without meeting the official standards for commercial use. P.R. China is one of the biggest diesel oil consumers worldwide (60–70 Mt) with a forecast growth of 6.4% from 1999 to 2020, thus increasing its share for world energy use for transportation to 9.1%. The country is highly import dependent and committed to non-food biodiesel feedstocks. Bioethanol development is much faster than that of biodiesel. Japan has interest in importation of coco-biodiesel. A recent overview of the Asian biodiesel industry can be found in Wahid [24]. See also Section 14.6.4.

1.5

Value chain of biodiesel

Actors in the biodiesel industry include the vegetable oil industry, biodiesel technology providers and producers, trade associations, oil companies, automobile manufacturers and regulatory agencies. The general public does not play any role in either supporting or blocking biodiesel (except perhaps in plebiscitian Switzerland). Along the biodiesel value chain, the main actors are the vegetable oil milling facilities and crude oil industry (i.e. the blending and distribution steps). Few companies have an integrated position along the whole biodiesel supply chain. Examples of vertical integration of vegetable oil and biodiesel producers are Diester Industrie (France; RSO/ RME), AGD and Vicentin (Argentina; SBO/SBME), Archer Daniels Midland Co. (USA; canola/RME), Oelmühle Leer Connemann (Germany; RSO/RME) and Argent Energy (Scotland; TLW, UCO/TME, UFOME). Cargill’s 37.5 MMgy biodiesel plant (Iowa Falls, IA) combines soybean crushing, biodiesel and USP grade glycerol production in a single site. Market development of a new product affects the whole value chain, which is divided into production, supply and consumption. The value chain of

Biodiesel as a renewable energy source

39

biodiesel production (Fig. 1.9) begins with large-scale plantation and growing of oil-bearing energy crops (e.g. EU’s set-aside land policy, India’s wasteland cultivation, P.R. China’s Planting Plan, and many physic nut plantations). This is followed by collection of oil-bearing seeds and extracting vegetable oil from the seeds/kernels in expeller units. Thereafter, the vegetable oil is put through a catalytic transesterification process for producing biodiesel. Biodiesel does not typically go straight from the processor to the fuel tank. It has to be distributed, blended in diesel for commercial use, and then redistributed to retailers before it is sold to consumers. Unlike ethanol, very little biodiesel is blended by refiners. Biodiesel is blended just before retail, either by a petroleum marketer or the biodiesel producers themselves. The supply step, including the blending and distribution process is usually the oligopoly of petrol companies. The value chain is easily interrupted, e.g. by an insufficient local infrastructure for blending. Biodiesel can use the transport, storage and retail systems of petrodiesel. In order to effectively ensure that biodiesel products meet all the specifications throughout the entire supply chain (from producer to blender, distributor, engine manufacturer, fleet manager, end-user and regulator) handheld field analysers have been developed (see Section 12.4.3). Critical issues as to a sustainable energy future in which biodiesel plays a role are the net energy balance, sustainable bioenergy crops, scale of production, consumer access and economics (cost-effective production). Increased vegetable oil production for biodiesel is not just a matter of (idle) cropland, but requires construction of crushing and esterification plants, distribution and storage facilities. In addition to the oil produced, also considerable amounts of biomass will be generated. Biodiesel may be directed to the transport sector or heating oil market. Collection

Processing

Distribution

Sourcing

Pre-processing

Storage

Securing

Merging

Storing

Production and monitoring

1.9 Biodiesel production cycle model.

Blending

Delivery

40

Biodiesel science and technology

B100 use is restricted and focused on eco-sensitive environments, such as waterways. Splash-blended 99.99% biodiesel is produced for tax credit allocation and export purposes. Blends of 20% to 2% are for fleet fueling and retail sale. B20 blends serve certain niches such as government and city fleets, whereas blends of less than 2% are used as fuel additives to prolong engine life. When introducing biofuels, fuel distributors need to take into account such issues as storage stability and water tolerance. Managing the transfers and tracking the blending are important to growing a viable biodiesel industry. The US trademarked Rinstar Renewable Fuel System (RFS) Registry provides companies throughout the industry, representing all facets of the supply chain (from producers and importers to marketers, refiners and blenders), with a cost-effective means to manage and validate their renewable fuel transfers while satisfying environmental obligations. This system has been in operation since 1 Sept. 2007 [101]. Biodiesel production is essentially transesterification catalysis. The present text describes the state-of-the-art of advanced processing technologies from both virgin oils and waste oils and fats to produce biodiesel on the basis of scientific and patent literature up to mid 2009 and gives some directions for the future. Methods to reduce the high cost of biodiesel focus on minimising the raw material cost and process (including catalyst) costs. In this respect the role of catalysis is an important one both technologically and economically.

1.6

Bibliography

K. Waldron (ed.), Bioalcohol Production: Biochemical Conversion of Lignocellulosic Biomass, Woodhead Publishing Ltd, Cambridge (2009). W. Thurmond, Biodiesel 2020: A Global Market Survey, Emerging Markets Online, Houston, TX (2008). A. Demirbaş, Biodiesel: A Realistic Fuel Alternative for Diesel Engines, Springer-Verlag, London (2008). National Biodiesel Board, Biodiesel. A Sustainable Choice, Jefferson City, MO (2008). Global Biofuels Center, Global Ethanol and Biodiesel Outlook, 2008–2015, Hart Energy Publishing, Houston, TX (2008). D.M. Mousdale, Biofuels. Biotechnology, Chemistry and Sustainable Development, CRC Press, Boca Raton, FL (2008). V. Smil, The Metrics of Energy, MIT Press, Cambridge, MA (2008). A. Züttel, A. Borgschulte and L. Schlapbach, Hydrogen as a Future Energy Carrier, Wiley-VCH, Weinheim (2008). D.A.J. Rand and R.M. Dell, Hydrogen Energy: Challenges and Prospects, RSC Publishing, Cambridge (2008).

Biodiesel as a renewable energy source

41

T. Volk, CO2 Rising: The World’s Greatest Environmental Challenge, MIT Press, Cambridge, MA (2008). Coordinating Group for Chemical Energy Research, Future Energy Supplies – The Contribution of Chemistry, GDCh, Frankfurt (2007); [email protected]. European Commission, Adapting to Climate Change in Europe: Options for EU Action, Brussels (2007) COM 354. S. Lee, J.G. Speight and S.K. Loyalka (eds), Handbook of Alternative Fuel Technologies, CRC Press, Boca Raton, FL (2007). Intergovernmental Panel on Climate Change, Summary for Policymakers, IPCC, Geneva (2007); www.ipcc.ch. European Renewable Energy Council and Greenpeace, Energy Revolution: A Sustainable World Outlook, Greenpeace International, Amsterdam (2007). D. Howell and C. Nakhle, Out of the Energy Labyrinth, I.B. Taurus, London (2007). E. Wilson and D. Gerard (eds), Carbon Capture and Sequestration: Integrating Technology, Monitoring and Regulation, Blackwell Publishing, Oxford (2007). European Commission, An Energy Policy for Europe, Brussels (2007); http:// eur-lex.europa.eu/LexUriServ/site/en/com/2007/com2007_0001en01. pdf. Organization of Petroleum Exporting Countries, World Oil Outlook 2007, OPEC, Vienna (2007). Commission of the European Communities, Biofuels Progress Report: Report on the Progress Made in the Use of Biofuels and Other Renewable Fuels in the Member States of the European Union, Brussels (2006), COM 845 final. European Commission, Green Paper on a European Strategy for Sustainable, Competitive and Secure Energy, Brussels (2006); http://eur-lex.europa. eu/LexUriServ/site/en/com/2006/com2006_0105en01.pdf. European Commission, Renewable Energies Roadmap, Brussels (2006); http://eur-lex.europa.eu/LexUriServ/site/en/com/2006/com2006_0848en01. pdf. European Commission, Action Plan for Energy Efficiency, Brussels (2006); http://eur-lex.europa.eu/LexUriServ/site/en/com/2006/com2006_0545en01. pdf. A. Gore and Melcher Media, An Inconvenient Truth: The Planetary Emergency of Global Warming and What We Can Do about It, Rodale Press, Emmaus, PA (2006). Copenhagen Consensus Group, A United Nations Perspective (30 Oct. 2006); http://www.copenhagen.consensus.com/Admin/Public/DWSDownload.as px?File=Files%2fFiler%2fCC+UNP%2fCC06_Outcome.pdf. European Commission, Directorate – General for Research, Directorate

42

Biodiesel science and technology

Energy, World Energy Technology Outlook – 2050, EUR 22038, Brussels (2006). Department of Trade and Industry, The Energy Challenge. Energy Review Report 2006, DTI, London (2006). Energy Information Administration, International Energy Outlook (DOE/ EIA-0484), U.S. Dept. of Energy, Washington, DC (2006). International Energy Agency (IEA), World Energy Outlook 2006, International Energy Agency Publications, Paris (2006). International Energy Agency (IEA), Energy Technology Perspectives 2006: Scenarios and Strategies to 2050, OECD/IEA, Paris (2006). International Energy Agency – Bioenergy Implementing Agreement (IEA/ BA). Task 39: Liquid Biofuels from Biomass (2004–2006), IEA, Paris (2006). Biofuels Research Advisory Council, Biofuels in the European Union: A Vision for 2030 and Beyond, EU Report, Brussels (2006). Associazione Italiana di Ingegneria Chimica (AIDIC), Aspetti Tecnicoeconomici della Produzione di Biocarburanti, AIDIC, Milan (2006). J. Tickell, Biodiesel America, Yorkshire Press, Ashland, OH (2006). G.A. Olah, A. Goeppert and G.K. Surya Prakash, Beyond Oil and Gas: The Methanol Economy, Wiley-VCH, Weinheim (2006). S. Minteer (ed.), Alcoholic Fuels, CRC Press, Boca Raton, FL (2006). G. Knothe, J. Van Gerpen and J. Krahl (eds), The Biodiesel Handbook, AOCS Press, Champaign, IL (2005). G. Knothe (ed.), Focus on Biodiesel (CD-ROM), AOCS Press, Urbana, IL (2005). B. Kamm, P.R. Gruber and M. Kamm (eds), Biorefineries – Industrial Processes and Products: Status Quo and Future Directions, Wiley-VCH, Weinheim (2005). R.S. White, Energy for the Public: The Case for Increased Nuclear Fission Energy, BookSurge Publishing, Santa Barbara, CA (2005). G. Phal, Biodiesel: Growing a New Energy Economy, Chelsea Green, White River Junction, VT (2005); 2nd edn (2008). R.D. Perlack, L.L. Wright, A.F. Turhollow, R.L. Graham, B.J. Stokes and D.C. Erbach, Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply, DOE/ USDA, Washington, DC (2005). Commission of the European Communities, Biomass Action Plan, Brussels (2005), COM 628. D. Bockey and W. Von Schenck, Status Report – Biodiesel Production and Marketing in Germany 2005, UFOP, Berlin (2005). D. Bockey (ed.), Biodiesel Flowerpower, UFOP, Berlin (2004). M. Mittelbach and C. Remschmidt, Biodiesel – The Comprehensive Handbook, Boersedruck Ges., Vienna (2004).

Biodiesel as a renewable energy source

43

D. Ryan, Biodiesel – A Primer, ATTRA Publication, National Center for Appropriate Technology, Butte, MT (2004). B. Elvers, Handbook of Fuels. Energy Sources for Transportation, WileyVCH, Weinheim (2004). B.T. Aranow (ed.), Winning the Oil Endgame: Innovation for Profits, Jobs and Security, Rocky Mountain Institute, Snowmass, CO (2004). International Energy Agency, Biofuels for Transport, IEA, Paris (2004). Union of Concerned Scientists, The Diesel Dilemma – Diesel’s Role in the Race for Clean Cars, UCS, Cambridge, MA (2004). G. Boyle (ed.), Renewable Energy, Oxford University Press, New York, NY (2004). Wissenschaftlicher Beirat der Bundesregierung, Globale Umweltveränderungen, Welt im Wandel: Energiewende zur Nachhaltichkeit, Springer-Verlag, Berlin (2003). S. Friedrich, A World-wide Review of the Commercial Production of Biodiesel, Institut für Technologie und nachhaltiges Produktmanagement, Wirtschaftsuniversität Wien, Schriftenreihe Umweltschutz und Ressourcenökonomie, Band 41, Vienna (2003). R.C. Brown, Biorenewable Resources, Iowa State University Press, Ames, IA (2003). E.J.S. Parente, Biodiesel: Uma Aventura Tecnológica num Pais Engraçado Ceará, Fortaleza (2003). World Energy Council, Survey of Energy Sources, WEC, New York, NY (2002). Biomass R&D Technical Advisory Committee, Roadmap for Biomass Technologies in the United States, Washington, DC (2002). Intergovernmental Panel on Climate Change (IPCC), Climate Change 2001 – Mitigation, Cambridge University Press, Cambridge (2001). National Renewable Energy Laboratory, Biodiesel – Clean, Green Diesel Fuel, Golden, CO (2001); DOE/GO-102001-1449; www.afdc.doc.gov/ pdfs/Bio_CleanGreen.pdf. B. Lomborg, The Skeptical Environmentalist, Cambridge University Press, Cambridge (2001). United Nations Development Program, World Energy Assessment: Energy and the Challenge of Sustainability, UNDP, New York, NY (2000). S. Howell and A. Weber, US Biodiesel Overview, National Biodiesel Board (ed.), Jefferson City, MO (2000). C. Song, C.S. Hsu and I. Moshida (eds), Chemistry of Diesel Fuels, Taylor & Francis, London (2000). J. Tickell, From the Fryer to the Fuel Tank: The Complete Guide to Using Vegetable Oil as an Alternative Fuel, Tickell Energy, Hollywood, CA (2000).

44

Biodiesel science and technology

T. Anema and M. Szuic-Krzyzanowski, World of Energy, De Verbeelding Publishers, Amsterdam (2000). D.L. Klass, Biomass for Renewable Energy, Fuels and Chemicals, Academic Press, San Diego, CA (1998). P.T. Anastas and J.C. Warner, Green Chemistry. Theory and Practice, Oxford University Press, New York, NY (1998). C.B. Prakash, A Critical Review of Biodiesel as a Transportation Fuel in Canada. A Technical Report, Global Change Strategies International, Inc., Ottawa (1998). N. Nakicenovic, A. Grübler and A. McDonald (eds), Global Energy Perspectives, Cambridge University Press, Cambridge (1998). UNFCCC, The Kyoto Protocol, United Nations Framework Convention on Climate Change, New York, NY (1997). C.E. Wyman, Handbook on Bioethanol: Production and Utilization, Taylor & Francis, New York, NY (1996). W.C. Holmberg and J.E. Peeples, Biodiesel: A Technology, Performance and Regulatory Overview, National SoyDiesel Board, Jefferson City, MO (1994). I.M. Campbell, Biomass, Catalysts and Liquid Fuels, Holt, Rinehart and Winston, London (1983). M. Grosser, Diesel: The Man and the Machine, Book Press, Brattleboro, VT (1978). W.R. Nitske and C.M. Wilson, Rudolf Diesel, Pioneer of the Age of Power, University of Oklahoma Press, Norman, OK (1965). R. Diesel, Die Entstehung des Dieselmotors, Julius Springer Verlag, Berlin (1913).

1.7

References

[1] Intergovernmental Panel on Climate Change, Fourth Assessment Report (AR4), UN, New York, NY (2007); adopted at IPCC Plenary XXVII, Valencia (12–17 Nov. 2007). [2] A.B. Robinson, N.E. Robinson and W. Soon, Environmental effects of increased atmospheric carbon dioxide, J. Am. Phys. Surg. 12 (2007) 79–90. [3] B. Lomborg, The Skeptical Environmentalist, Cambridge University Press, Cambridge (2001). [4] K.P. Shine and W.T. Sturges, CO2 is not the only gas, Science 315 (2007) 1804–5. [5] G. Alexander and G. Boyle, Introducing renewable energy, in Renewable Energy (G. Boyle, ed.), Oxford University Press, New York, NY (2004). [6] K.S. Deffeyes, Hubbert’s Peak: The Impending World Oil Shortage, Princeton University Press, Princeton, NJ (2001). [7] N.V. Fedoroff and J.E. Cohen, Plants and population: Is there time?, Proc. Natl. Acad. Sci. USA 96 (1999) 5903–7.

Biodiesel as a renewable energy source



45

[8] Energy Information Administration, International Energy Outlook (DOE/EIA0484), US Dept. of Energy, Washington, DC (2006). [9] C. Griggs, Gas hydrates. A curse to the world’s oil and gas industries or the energy source of the future?, Petro Ind. News 5(5) (2004) 45–6. [10] Renewables in Global Energy Supply, OECD/IEA, Paris (2006). [11] M. Katan, R. Rabbinge and W. Van Swaaij, Toekomst voor biodiesel is illusie, Financieel Dagblad (2006). [12] M.J. Currie, J.K. Mapel, T.D. Heidel, S. Goffri and M.A. Baldo, High-efficiency organic solar concentrators for photovoltaics, Science 321 (2008) 226–8. [13] C. Plöchl, Biodiesel projects under the Kyoto Clean Development Mechanism, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [14] European Environment Agency, How Much Biomass Can Europe Use Without Harming the Environment?, EEA Briefing 02 (2005); http://www.eea.eu.int/ [15] G. Bergsma, GHG calculation of biofuels in the international debate: bottlenecks and perspectives, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [16] International Energy Agency, Biofuels for Transport – An International Perspective, IEA, Paris (2004). [17] Minnesota State Legislature, The Minnesota Biodiesel Mandate, Minnesota Session Laws, Chapter 239 SF-1495 (15 March 2002). [18] Directive of the European Parliament and of the Council on the Promotion and Use of Energy from Renewable Sources (RED), Brussels, COM (2008) 30 final. [19] The Energy Challenge (report to DTI), http://www.dti.govuk/energy/review/page 31995.html (July 2006). [20] UK Dept. for Business, Enterprise and Regulatory Reform, Meeting the Energy Challenge. A White Paper on Energy, BERR, London (2007). [21] P. Hammond, Simmons & Co. International, Houston, TX (2007). [22] US Dept. of Energy (DOE), Plant/Crop-based Renewable Resources 2020 – A Vision to Enhance US Economic Security through Renewable Plant/Crop-based Resource Use, DOE/GO – 10098 – 3385, Washington, DC (Jan. 1998). [23] Philippine Department of Energy, Philippine Energy Plan 2002–2011, Manila (2002). [24] M.B. Wahid, Asian perspective: Overview of the biodiesel industry in Asia, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [25] C.L. Peterson, Potential production of biodiesel, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds.), AOCS Press, Urbana, IL (2005), pp. 231–8. [26] www.oecd.org/dataoecd/40/25/39266869.pdf. [27] T. Searchinger, R. Heimlich, R.A. Houghton, F. Dong, A. Elobeid, J. Fabiosa, S. Tokgoz, D. Hayes and T.-H. Yu, Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change, Science 319 (2008) 1238–40. [28] H.W. Lüke, BTL-Kraftstoffe: Eine vielversprechende Option für die Zukunft, Erdoel, Erdgas, Kohle 121 (2005) 3–14. [29] F. Ma and M.A. Hanna, Biodiesel production: a review, Bioresour. Technol. 70 (1999) 1–15. [30] C. Macve and C. Rowntree, Driving towards a cleaner future, Chem. Rev. 14 (2005) 10–13. [31] A.J. Kinney and T.E. Clemente, Modifying soybean oil for enhanced performance in biodiesel blends, Fuel Proc. Technol. 86 (2005) 1137–47.

46

Biodiesel science and technology

[32] C.R. Bayense, H. Hinnekens and J. Martens (to Engelhard/Fina Research), Esterification process, Eur. Pat. EP 0,623,581 A2 (4 May 1994). [33] R.G. Stern, G. Hillion, J.-J. Rouxel and S. Leporq (to IFP), Process for the production of esters from vegetable oils or animal oils and alcohols, US Pat. 5,908,946 (1 June 1999). [34] B. Delfort, G. Hillion and I. Durand (to IFP), Procédé de fabrication de biocarburants. Transformation de triglycerides en deux familles de biocarburants: monoesters d’acides gras et acetales solubles du glycerol, Fr. Pat. Appl. 2,866,654 (26 Aug. 2005). [35] G. Hillion, B. Delfort and I. Durand (to IFP), Procédé de fabrication de biocarburants. Transformation de triglycerides en deux familles de biocarburants: monoesters d’acides gras et ethers solubles du glycerol, Fr. Pat. Appl. 2,866,653 (26 Aug. 2005). [36] C. Baudouin, Biodiesel second-generation technology, Paper presented at WRA 2005 – 6th European Fuels Conference, Paris (14–16 March 2005). [37] Institut Français du Petrole (IFP), Procédé de fabrication d’esters à partir d’huiles végétales ou animales et d’alcools, Fr. Pat. 2,752,242 (13 Feb. 1998). [38] B. Delfort, I. Durand, A. Jaecker, T. Lacome, X. Montagne and F. Paille (to IFP), Compositions de carburants diesel contenant des acetals de glycerol, Fr. Pat. 2,833,607 (20 June 2003). [39] S. Kojima and E.Y. Park, Conversion of residual vegetable oil on waste activated bleaching earth to biodiesel fuel, Nendo Kagaku 44 (2005) 138–42. [40] C.N. Khalil and L.C.F. Leite (to Petrobras), Process for producing biodiesel, PCT Int. Publ. No. WO 2005/030911 (7 Apr. 2005). [41] Y.M. Choo, A.N. Ma and Y. Basiron, Production and evaluation of palm oil methyl esters as diesel substitute, Elaeis Special Issue (1995) 5–25. [42] S.H. Ong, Y.M. Choo, K.Y. Cheah and N. Abu Bakar (to Palm Oil Research and Development Board/Petronas), Production of alkyl esters from oils and fats, Austral. Pat. AU-B-43519/89 (18 Oct., 1989). [43] N. Foidl, G. Foidl, M.Sanchez, M. Mittelbach and S. Hackel, Jatropha curcas L. as a source for the production of biofuel in Nicaragua, Bioresour. Technol. 58 (1996) 77–82. [44] A. Mutsaars and H. Gosselink (Shell Global Solutions); confronta A. Duyndam, C2W103 (17 March 2007), pp. 16–17 (in Dutch). [45] L. Rantanen, R. Linnaila, P. Aakko and T. Harju, NExBTL – Biodiesel fuel of the second generation, SAE Tech. Paper 2005-01-3771 (2005). [46] D. Rothe, J. Lorenz, R. Lämmermann, E. Jacobi, L. Rantanen and R. Linnaila, New BTL diesel reduces effectively emissions of a modern heavy-duty engine, Kolloquium ‘Fuels’ der Technischen Akademie Esslingen (TAE), January 2005. [47] M. Koskinen, M. Sourander and M. Nurminen, Apply a comprehensive approach to biofuels, Hydrocarb. Proc. 85 (2006) 81–6. [48] B. Kamm and M. Kamm, Principles of biorefineries, Appl. Microbiol. Biotechnol. 64 (2004) 137–45. [49] D.L. Klass, Biomass for Renewable Energy, Fuels, and Chemicals, Academic Press, San Diego, CA (1998). [50] European Committee for Standardisation. Automotive Fuels. Fatty Acid Methyl Esters (FAME) for Diesel Engines. Requirements and Test Methods. European Standard EN 14214 (2003).

Biodiesel as a renewable energy source

47

[51] D. Chiaramonti, M. Bonini, E. Fratini, G. Tondi, K. Gartner, A.V. Bridgwater, H.P. Grimm, I. Soldaini, A. Webster and P. Baglioni, Development of emulsions from biomass pyrolysis liquid and diesel and their use in engines – Part 1: Emulsion production, Biomass Bioen. 25 (2003) 85–99. [52] D. Chiaramonti, M. Bonini, E. Fratini, G. Tondi, K. Gartner, A.V. Bridgwater, H.P. Grimm, I. Soldaini, A. Webster and P. Baglioni, Development of emulsions from biomass pyrolysis liquid and diesel and their use engines – Part 2: Tests in diesel engines, Biomass Bioen. 25 (2003) 101–11. [53] A.V. Bridgwater, Principles and practice of biomass fast pyrolysis processes for liquids, J. Anal. Appl. Pyrol. 51 (1999) 3–22. [54] A.V. Bridgwater, D. Meier and D. Radlein, An overview of fast pyrolysis of biomass, Org. Geochem. 30 (1999) 1479–93. [55] A.V. Bridgwater and G.V.C. Peacocke, Fast pyrolysis processes for biomass, Renew. Sust. En. Revs. 4 (2000) 1–73. [56] D. Meier and O. Faix, State of the art of applied fast pyrolysis of lignocellulosic materials – a review, Bioresour. Technol. 68 (1999) 71–7. [57] Indian Space Research Organisation, Production of hydrocarbons by thermolysis of vegetable oils, UK Pat. 1,524,781 (24 Jan. 1977). [58] R.A. Niehaus, C.E. Goering, L.D. Savage and S.C. Sorenson, Cracked soybean oil as a fuel for a diesel engine, Trans. ASAE 29 (1986) 683–9. [59] A.W. Schwab, G.J. Dykstra, E. Selke, S.C. Sorenson and E.H. Pryde, Diesel fuel from thermal decomposition of soybean oil, J. Am. Oil Chem. Soc. 65 (1988) 1781–6. [60] M. Predel and W. Kaminsky, Pyrolysis of rape-seed in a fluidised-bed reactor, Bioresour. Technol. 66 (1998) 113–17. [61] F. Billaud, V. Dominguez, P. Broutin and C. Busson, Production of hydrocarbons by pyrolysis of methyl esters from rapeseed oil, J. Am. Oil Chem. Soc. 72 (1995) 1149–54. [62] J.W. Alencar, P.B. Alves and A.A. Craveiro, Pyrolysis of tropical vegetable oils, J. Agric. Food Chem. 31 (1983) 1268–70. [63] D. Pioch, P. Lozano, M.C. Rasoanantoandro, J. Graille, P. Geneste and A. Guida, Biofuels from catalytic cracking of tropical vegetable oils, Oléagineux 48 (1993) 289–92. [64] C.-C. Chang and S.-W. Wan, China’s motor fuels from tung oil, J. Ind. Engng. Chem. 39 (1947) 1543–8. [65] S. Şensöz and I. Kaynar, Bio-oil production from soybean (Glycine max L.): fuel properties of bio-oil, Ind. Crops Prod. 23 (2006) 99–105. [66] S. Yorgun, S. Şensöz and Ö.M. Koçkar, Flash pyrolysis of sunflower oil cake for production of liquid fuels, J. Anal. Appl. Pyrol. 60 (2001) 1–12. [67] R.O. Dunn, Other alternative diesel fuels from vegetable oils, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 241–63. [68] S.P.R. Katikaneni, J.D. Adjaye, R.O. Idem and N.N. Bakhshi, Performance studies of various cracking catalysts in the conversion of canola oil to fuels and chemicals in a fluidized-bed reactor, J. Am. Oil Chem. Soc. 75 (1198) 381–91. [69] G.N. da Rocha Filho, D. Brodzki and G. Djéga-Mariadassou, Formation of alkanes, alkylcycloalkanes and alkylbenzenes during the catalytic hydrocracking of vegetable oils, Fuel 72 (1993) 543–9.

48

Biodiesel science and technology

[70] J. Gusmão, D. Brodzki, G. Djéga-Mariadassou and R. Frety, Utilization of vegetable oils as an alternative source for diesel-type fuel: hydrocracking on reduced Ni/ SO2 and sulphided Ni-Mo/g-Al2O3, Catal. Today 5 (1989) 533–44. [71] J.R.S. Dos Anjos, W. De Araujo Gonzalez, Y.L. Lam and R. Frety, Catalytic decomposition of vegetable oil, Appl. Catal. 5 (1983) 299–308. [72] F.A.A. Twaiq, A.R. Mohamad and S. Bhatia, Performance of composite catalysts in palm oil cracking for the production of liquid fuels and chemicals, Fuel Proc. Technol. 85 (2004) 1283–300. [73] F.A.A. Twaiq, N.A.M. Zabidi, A.R. Mohamad and S. Bhatia, Catalytic conversion of palm oil over mesoporous aluminosilicate MCM-41 for the production of liquid hydrocarbon fuels, Fuel Proc. Technol. 84 (2003) 105–20. [74] F.A.A. Twaiq, A.R. Mohamad and S. Bhatia, Liquid hydrocarbon fuels from palm oil by catalytic cracking over aluminosilicate mesoporous catalysts with various Si/Al ratios, Micropor. Mesopor. Mat. 64 (2003) 95–107. [75] H.F. Gerçel, A.E. Pütün and E. Pütün, Hydropyrolysis of extracted Euphorbia rigida in a well-swept fixed-bed tubular reactor, En. Sourc. 24A (2002) 423–30. [76] P. Aalto and O. Piirainen (to Neste Oy), Keskilisleen valmistus, Finnish Pat. FI 100,248 (6 Aug. 1997). [77] S. Mikkonen, Second-generation renewable diesel offers advantages, Hydrocarb. Proc. (Feb. 2008) 63–8. [78] M. Herskowitz, M. Landau, I. Reizner and M. Kaliya (to Ben Gurion University of the Negev Research and Development Authority), Production of diesel fuel from vegetable and animal oils, US Pat. Appl. 2006/0207166 A1 (21 Sept. 2006). [79] M. Matsumura and S. Murakami, Method and equipment of refining plant oil and waste vegetable oil into diesel engine fuel, US Pat. No. 6,364,917 B1 (2 Apr. 2002). [80] N.U. Soriano, V.P. Migo and M. Matsumura, Ozonation of sunflower oil: spectroscopic monitoring of the degree of unsaturation, J. Am. Oil Chem. Soc. 80 (2003) 997–1001. [81] M.R. Simmons, Can motor fuels be redesigned?, Hydrocarbon Proc. (Feb. 2008) 41–4. [82] W. Thurmond, Biodiesel 2020: A Global Market Survey, 2nd edn, Emerging Markets Online, Houston, TX (2008). [83] S. Blagoev, S. Bizzari, R. Gubler, C. Funada and Z. Yi, Biodiesel Report 2008, SRI Consulting, Stanford, CA (Sept. 2008). [84] Y. Basiron, Biofuel: an alternative fuel in the Malaysian scenario, Palm Oil Dev. 42 (June 2005) 1–2. [85] J. Duffield, H. Shapouri, M. Graboski, R. McCormick and R. Wilson, Biodiesel Development: New Markets for Conventional and Genetically Modified Agricultural Products, Economic Research Service Rept. No. 770, USDA, Washington, DC (1998). [86] Y. Zhang, M.A. Dubé, D.D. McLean and M. Kates, Biodiesel production from waste cooking oil: 2. Economic assessment and sensitivity analysis, Bioresour. Technol. 90 (2003) 229–40. [87] Austrian Biofuels Institute (ABI), World-wide trends in reduction and marketing of biodiesel. Presentation at ALTENER-Seminar New Markets for Biodiesel in Modern Common Rail Diesel Engines, University of Technology, Graz (22 May, 2000).

Biodiesel as a renewable energy source

49

[88] W. Körbitz, Review on Commercial Production of Biodiesel Worldwide 1997, Austrian Biofuels Institute, Vienna (1998). [89] A. Bedwell, Global diesel trends, Presentation at Renewable Diesel Conference, Houston, TX (15–16 Nov. 2007). [90] M.-C. Hénard, GAIN Report-FR6005, USDA Foreign Agricultural Service, Paris (2006). [91] Soyatech Biofuels Index, www.soyatech.com /store.htm. [92] C. Strong, C. Erickson and D. Shukla, Evaluation of Biodiesel Fuel: Literature Review, Report to Montana Department of Transportation, Helena, MT (Jan. 2004). [93] Biodiesel Economic Impacts, Minnesota Soybean Board webpage, http://www. mnsoybean.org/showpages.cfm?pageid=566. [94] Canadian Agri-Food Research Council, An Assessment of the Opportunities and Challenges of a Bio-Based Economy for Agriculture and Food Research in Canada, Ottawa, ON (2003). [95] Y. Chisti, Biodiesel from microalgae, Biotechnol. Adv. 25 (2007) 294–306. [96] European Biodiesel Board, Biodiesel Production Statistics, Brussels (2003); http:// www.ebb.eu.org/stats.php. [97] B. Prebo and A. Thurlo Pearson, Update on US biodiesel production, Hydrocarb. Proc. (Feb. 2008) 95–8. [98] C.A. Johnson, Biodiesel production trends survey 2008, Biodiesel Mag. 5(5) (2008) 38–42. [99] M. Bowman, D. Hilligoss, S. Rasmussen and R. Thomas, Biodiesel: A renewable and biodegradable fuel, Hydrocarb. Proc. 85(2) (2006) 103–6. [100] Brazilian National Agency for Petroleum, Natural Gas and Biofuels (ANP), Act No. 255 (15 Sept. 2003). [101] C. McMartin, The hidden costs of the renewable fuel standard, Biodiesel Mag. 5(2) (2008) 160–4.

2

Development of non-food agricultural industries for biofuel applications

Abstract: Quite recently, agriculture not only acts as a traditional source for food, feed and fibre, but is generating feedstock for vegetable oil-based renewable fuels. In particular, edible oils are increasingly finding industrial applications for energy purposes beyond their traditional oleochemical use. Higher pressure on globally limited vegetable oil commodities poses commercial and ethical threats which require an urgent solution. As biomass has a limited edible oil potential, development of a non-food agricultural industry for fuel applications has clear advantages. Biotechnology is vital in addressing the growing global demands for crops for food, fodder, fibre and fuel. Key words: Food security, energy needs, non-food crops, renewable energy sources, advanced agroenergy crops.

2.1

Introduction

Out of the 170–200 billion tons of annually produced biomass (any organic matter available on a renewable basis, including dedicated energy crops and trees, agricultural food and feed crop residues, aquatic plants, wood and wood residues, animal wastes, and other waste materials), 75% are carbohydrates (cellulose, starch, saccharose), 20% lignin, and only 5% other natural components such as oils and fats, proteins and other substances. Of the 3.5% biomass production currently used for human needs (or 6 Bty), 62% is used for human food, 33% for energy use, paper and construction needs, and 5% (or 300 Mt) for other technical (non-food) raw materials (clothing, detergents, chemicals) [1]. Agriculture has developed mainly as a source of food, feed and fibre. The economic added-value of plants (in approximate decreasing order) is related to flowers, flavours and fragrances, fine chemicals, feed, fodder and fuels (7F). Out of approximately 125 Mt of oils and fats produced worldwide in 2003, 81% was used in human foodstuffs (over 120 edible oils) and 5% in animal feed. For (oleo)chemical (or non-food) applications 17.4 Mt (14%) were available. Plant oils are widely used for food products such as shortenings, salad and cooking oils, and margarines. Industrial use of vegetable oils is specified in more detail in Section 3.4. Nowadays, some 7% of synthetic chemicals are produced from non-fossil biological sources or by means of biotechnology. Edible vegetable oils may 50

Development of non-food agricultural industries

51

also find useful applications for energy purposes. Table 2.1 shows the main market segments for oils and fats (pharmaceutical, chemical, food and fuel), with an indication of the allowable price levels for the raw materials. There is clearly competition between various applications. Some crops release high-value oils for use in the pharmaceutical and cosmetics industries (e.g. castor oil, jojoba wax oil, argan oil, almond oil, and others). Vegetable oils are a large renewable resource, now harvested at about 125 Mt/yr (2007/08). In recent years, particularly in the EU and US, there has been growing interest in the use of crops as biorenewable industrial feedstocks, for applications such as fuels, lubricants and bio-plastics. The agricultural industry would not be able to expand and create wealth on the current scale if not for biofuel demand; the industry is changing in providing material for first- and second-generation biofuels. Use of vegetable oils for biodiesel has put pressure on the nutritional use of the commodity and has triggered questions about the ethics of pulling edible oils from the food and feed supply chain to produce fuel. Food and energy are the number one drivers in the world. The challenge can be alleviated by exploration of new (non-food) crops and unexploited crops capable of producing oils and fats for the industry [2]; see also Chapter 6. Using waste plant material instead of food crops could circumvent political pressure and public controversy over using crops for fuel. The fact is, however, that even farmers do not make a choice between energy and food; they simply go for the highest profit. Citizens need both food and energy, while politicians avoid unpopular decisions concerning nuclear energy, coal, gentech and eventually just favour windmills as long as they are out of sight.

2.2

Biofuels

Production of liquid transportation fuels and industrial chemicals from biomass relies most heavily on utilisation of polysaccharide, lignocellulosic and triacylglyceride feedstocks. The following products are regarded as biofuels (an umbrella term covering all fuels derived from organic matter): Table 2.1 Market segments for oils and fats Market segment

Market characteristics



Relative potential

Product need (t/yr)

Commercial valuea

Pharmaceutical Chemicalb Food Energy

Very limited Moderate Great Infinite

< 105 2 x 107 108 > 108

> 2000 700–2000 450–700 < 450

a

Price level US$ (2003)/ton.     Including cosmetics.

b

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Biodiesel science and technology

bioethanol, biodiesel, biogas, biomethanol, biodimethylether, bio-methyl tert-butyl ether (MTBE), bio-ethyl tertiary butyl ether (ETBE), synthetic biofuels, biohydrogen and pure vegetable oil. The main types of biofuel are bioethanol, as a direct substitute for petrol (although most petrol engines cannot operate on bioethanol without modification) and biodiesel, as a fuel produced by catalytic processing of vegetable oils (and directly applicable in diesel engines without modification). Ethanol may be obtained from corn, which is a crop requiring much water and fertilisers. Alternatives are sugar beets, sugarcane, agricultural waste or fast-growing grasses. Cellulose ethanol has reached production in demonstration plants. Ethanol as a biofuel has several drawbacks: it acts as a poison to microorganisms, is water soluble and requires energy-intensive distillation. Ethanol cannot be pumped, and needs local production with transportation by tanks. Biodiesel fuel has been in commercial use in many countries for up to 20 years. Given the total vegetable oil/animal fat market of about 157 Mt in comparison with world use of crude mineral oil of 4.2 Bty (2006/07) it is apparent that the contribution of vegetable oils to replace mineral oils will ever only be minimal. It is expected, however, that the fundamental aspects of the biofuels industry will change dramatically by 2020.

2.3

Biomass potentials and limitations

Hundreds of crops have been domesticated and cultivated by humankind during the history of agriculture, utilised for food, forage, fibre and medicine. However, only a small number provide the bulk of raw material necessary for human survival. The limited diversity has increased the vulnerability of crops to adverse climatic conditions and fluctuating markets. Not every location on earth is suitable for energy-crop production. Water supply is indispensable for plant growth (a volume of thousands of litres of water is necessary for 1 kg of biomass) and agricultural productivity is limited by the availability of water. Judicious use of water is paramount. Non-food crops, though not edible, nevertheless compete with food crops for land and water supplies. Less than 1% of cultivated land is currently used for the production of transportation fuels. Non-food crops are an ambitious goal. Development of a ‘non-food’ agricultural industry, where non-food refers to all biological materials and processes used in the production of industrial chemicals, polymers and fibres, servicing diverse industrial outlets, is a recent phenomenon. From an agricultural point of view benefits of non-food uses of crops include reduction of food surpluses, creation of new market outlets for agricultural products, development of a new range of value-added products, environmental benefits and sustained employment for farmers and related industries. Moreover, if a non-food agricultural industry can be developed without the need for large

Development of non-food agricultural industries

53

processing units, such production facilities close to the source of the raw materials and end-users strengthen the economy of rural areas. Major technical bottlenecks limiting production and utilisation of industrial crops and products arise from the fact that the quality, quantity and price of agricultural raw materials are insufficient to supply industries with appropriate feedstocks for their processes [3]. More specifically: ∑ ∑ ∑ ∑ ∑ ∑

the batch-to-batch variable composition of biological raw materials is inconvenient for continuous industrial processing; continual supply of raw materials (except waste oils and fats) is difficult as agricultural production is essentially a seasonal activity (not applicable to the tropics); plant size is limited by biomass collection; the specific knowledge base of biological raw materials is limited as for decades industrial R&D has been focused on processing of fossil resources; traditional process technologies for biological materials do not fulfil current ecological requirements; and intensive use of fertilisers might even result in a net loss of energy.

While more than 1000 oil plants have been identified worldwide, existing global lipid production is not enough to meet future demands. Biodiesel production could lead to a shortage of oil. The EU’s ultimate goal of 5.75% market share for biomass-derived transport fuels by 2010 has a profound impact on agriculture, as it would need at least 9% of the EU agricultural area. To achieve the goal of having all petrol diluted by 10% ethanol would require turning 70% of all EU agricultural land into the production of corn. If one-third of the total Italian surface were dedicated to cultivation of rapeseed, this would yield a quantity of biodiesel sufficient to satisfy 40% of the total consumption of diesel for transportation in the country. Similarly, to replace 5% of the fuel consumed annually in the UK with bioethanol requires turning over around 6300 km2 of arable land for this purpose, or 10% of the total arable area of the UK, which would conflict with food production. Harvested cropland in the US is about 147.1 Mha. In the unrealistic scenario that the entire US cropland were planted with rapeseed, a maximum of 40 Bgy of biodiesel could be produced, which is equivalent to 121% of the annual consumption of petrodiesel for on-highway transportation. Soybean cultivation would yield 23 Bgy or 70% of annual consumption. Energy security and food security are no longer distinct problems and are subject to increasing political intervention (such as EU and US oilseed tax subsidies and regulations, bilateral fuel-for-food contracting, Chinese investments in foreign farming land and foodstuff export restrictions by some Asian countries) and financial speculation (hedge funds, futures). Energy needs may become so pressing that so much agricultural land is diverted to

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fuel crops that this results in a shortage in actual food production. Already in the last three years sugar and alcohol are fighting for sugarcane acres in the (sub)tropics; corn and soy are competing for food and fuel applications in the US. A strategy based on the use of agricultural areas for food production and development of robust (non-edible) energy crops (with high draught resistance, high photosynthesis capacity and possibilities for fixation of nitrogen and CO2) for marginal areas limits competition between food and energy/fuels/chemistry. Out of the total global usable land area, consisting of 1650 Mha farmland, 4700 Mha grassland and 5750 Mha forest, by 2000 already some 1550 Mha were considered as being degraded due to erosion, desertification and salination. The degradation process proceeds at 6–10 Mha/yr and is particularly pronounced in the last 30 years. The reform of the EU Common Agricultural Policy (CAP) includes set-aside regulations which allow for growing of new and traditional crops for non-food industrial end-uses (energy, pulp and paper, composites and chemicals) with full hectare premium (EC Directive 1870/95). For example, the EC is attempting to reinstate castor beans as a strategic oil crop to be grown in set-aside lands. In the same context non-wood fibrous plants such as flax, hemp, cotton, miscanthus, kenaf, esparto and cardoon are potential crops for the paper industry in different EU countries. However, although the regulation should have been most attractive for new non-food crops, in practice about 90% of the crops sown were rapeseed and sunflower seed with the main outlet being the biofuels sector. One hectare of agricultural land can annually yield around 1200 L of rape biodiesel (see Fig. 5.2). With the great variations in set-aside rate (in % of total acreage) in the EU (15% in 1992, 5% in 1997, 10% afterwards) calculated maximum domestic oil potentials have varied considerably over time. Table 2.2 lists subsidised hectarage for energy crops in Europe (out of 2.5 Mha). The United States is the largest single consumer of fossil fuels in the world with a consumption exceeding 140 Bgy of gasoline and 60 Bgy of diesel fuel. The amount of biomass grown annually in the US is sufficient to provide approximately 70% of the transportation sector, assuming that this biomass can be converted to clean-burning fuels having high energy densities, such as currently provided by petroleum. It is estimated that the combined forest and agriculture land resources of the US are capable of producing a sustainable supply of biomass (1.3 billion dry tons/yr) without major changes in agricultural practices. This amount of biomass corresponds to approximately 3.5 billion barrels of oil equivalent each year, sufficient to displace about 30% of the country’s present petroleum consumption and still continue to meet food, feed and export demands [4]. Biomass feedstock consumption (190 million dry tons in 2003) surpassed hydropower as the largest domestic source of renewable energy and currently provides over 3% of the total energy consumption in the US. Corn-to-ethanol

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Table 2.2 Subsidised areas (kha) for energy crops in Europe Country

2004

2005

Germany France UK Sweden Spain Denmark Finland Austria Italy Others Total

109.1 130.0 33.0 14.5 6.7 4.5 3.5 3.5 – 1.1 305.9

237.7 135.8 88.6 31.1 27.3 17.5 10.3 8.1 0.3 4.7 561.4

Source: EC–DG Agri.

distilleries are springing up all over the US and bioethanol production is forecast to double between 2005 and 2007, by which time bioethanol will be consuming 20% of the total US corn harvest. With the dawning realisation that oil-dependent economies may not be sustainable, the major crop source for producing biofuels, i.e. corn, has recently shown a spectacular rise in price. Biodiesel production in the USA, mainly from soybeans, increased from 12.5 Mgal in 2001 to 700 Mgal in 2008 (Fig. 1.8), partly as a result of an Environment Protection Agency (EPA) mandate to reduce sulphur in diesel fuel. Assuming that all soybeans not needed for food (at constant requirements), feed or export could be used for biodiesel, the maximum available amount of 297 Mbu (million bushels) could result in 415 Mgal of pure biodiesel [4]. The soybean equivalent of oil required for a 4% share of biodiesel in 2016 is projected to increase from 51 Mbu (1.39 Mt) in 2002 to 318 Mbu (8.65 Mt) by 2016. While soybeans are expected to remain the predominant feedstock, an increasing share of biodiesel production will come from other oils, including recycled soybean oil (SBO). Total vegetable oil consumption in the US is about 12 Mt/yr; the country produces some 5.2 Mt of animal derived fats and generates approximately 1.25 Mt/yr of waste recyclable restaurant grease. The US could produce some 3.75 Bgy of vegetable oil (rapeseed oil (RSO) or sunflower oil (SNO)) on its fallow croplands (37 million out of 455 million acres in 2002), but this potential could even double by using high-efficiency farming. Taking into account a share of used frying oil, the US could easily boost biodiesel to over 10% of its annual diesel fuel usage without interference with food production. Algae farming is another area of high potential (see Section 5.7). Chevron Technology Ventures is among proponents of using non-food plants to create transportation fuels.

56

Biodiesel science and technology

Between 1961 and 2001 world production of oil palm fruit grew from 14 Mt/yr to 128 Mt/yr; soybean production increased from 27 Mt/yr to 178 Mt/ yr over the same period. The global area used for soybean crop growth has increased from 24 Mha to 77 Mha, while the yield has doubled from 1.13 to 2.32 t/ha. The amount of global land used for production of oil palm has grown from 4 Mha to 11 Mha, while the worldwide yield of the crop has nearly quadrupled from 3.77 to 12.17 t/ha. In Malaysia, yields have grown even higher, increasing from 11.5 to 17.8 t/ha. High-yield seedlings might increase the crude palm oil (CPO) yield even further (up to 27–30 t/ha). Generally, it is considered that non-edible oils should be exploited as far as possible so that edible oils can be made available for human consumption. This is especially important in developing countries such as India where food supply poses a challenge. Agricultural productivity usually increases by about 1%/yr, but a three- to six-fold increase is needed.

2.4

Advanced agroenergy crops

Biomass production needs improvement as well as development of technologies to derive the maximum amount of usable energy from biomass at an acceptable price. Advances in plant sciences and genetics are required to develop agroenergy crops having increased yield and utility. Although many annual crops have been subjected to continuous domestication, this is much less the case for perennial species. Breeding technologies have traditionally aimed mainly at an improvement in the yield performance of useful plants. Breeding allows propagation of superior plant varieties which are vital to ensure the sustainability of food and energy supplies. The advent of agricultural biotechnology, including genetic engineering, has extended the range of tools by which this can be achieved. Gene technology is a universal approach for inducing new genetic variation. Although the oil processing industry is considered a mature one, biotechnology has implications for modifying nature’s traditional oil-bearing materials to produce herbicide-resistant plants, or ones with customised fatty acid content, as well as vastly speeding development of desirable commercial plant varieties. Biotechnologies are vital in addressing the growing demand for crops for food, feed, fibre and fuel, their primary production and processing. If the production of industrially important fatty acids in high-yielding oil crops can be developed successfully through genetic engineering approaches, there is a huge market volume available. Given the apparent worldwide limitation on land suitable for oilseed production, genetic enhancement of oilseed productivity may be the best means to achieve the quantity and quality of edible oils needed to accommodate both food markets and the potential demand for oleochemicals and biofuels. Recent steep increases in food prices will undoubtedly trigger further discussions about increasing agricultural

Development of non-food agricultural industries

57

production by plant biotechnology. Biotech crops bring considerable benefits to agriculture. Breeding and biotechnology are the primary methods used to increase crop yields. Yield gains are considerable and range from 10 bu/ac (1925) to 40 bu/ac (2005) for soybean and from 1500 kg/ha (1930) to 9500 kg/ ha (2005) for corn. As an illustrative example, soybean crop production in Argentina has steadily increased in the past, with a significant rise during the last decade, mainly because of the increase in land devoted to soy (53% of the farmland in 2007). Soy production has almost tripled in the last 15 years, increasing sharply after the introduction of genetically modified soy in the 1996–97 season (Fig. 2.1). At present, 100% of the country’s soy production (used for food/feed and for biodiesel export) is genetically modified. Few issues have proved as globally divisive as the ability to modify crops genetically. There are certain barriers to the realisation and use of gene technology because of poor acceptance by some end-users. However, there exists overwhelming scientific evidence and positive commercial experience of biotech crops around the world with no fewer than 125 Mha of land in 2008 in 22 countries (mainly US 62.5 Mha, Argentina 21 Mha, Brazil 15.8 Mha, Canada 7.6 Mha, India 7.6 Mha and China 3.8 Mha) producing genetically modified (GM) crops, in particular soy (58.6 Mha), corn (25.2 Mha), cotton 40

35

Soybean production (Mt)

30

25

20

15

10

5 1990

1992

1994

1996

1998 Year

2000

2002

2.1 Soybean production (Mt) in Argentina (after ref. [5]).

2004

2006

58

Biodiesel science and technology

(13.4 Mha) and rapeseed (4.8 Mha) (2006 data) [6]. While the US has a substantial list of authorised oil-bearing GM crops (soybean, rape, cottonseed, maize) which are being widely grown and mainly modified in view of the need for sturdier crops (resistance to pests, floods, drought) hardly any GM food crops are being grown in the EU (with France, Germany, Austria, Italy, Greece and Luxembourg expressing doubts about the value of GM crops). Spain is the only EU country with a significant hectarage of commercial biotech crops (Bt maize); also Romania is growing GM soybean. The EU is cautious with its regulatory regime (2001/18/EC, 2003/1829/ EC, 2003/1830/EC and 2003/1946/EC). Progress on crop growing and GM approvals in the EU is slow. Recently, the European Commission has been approving the release of some GM products, as in case of oilseed rapes Bayer MSSRF3 and Monsanto GT73. EU has recently also admitted the genetically modified maize Mon810 and T25, but is still blocking introduction of two other GM maize seedlings (Pioneer Hi-Bred 1507 and Syngenta Bt11). Moreover, gentech crops which are not (yet) legally permitted in the EU cannot be imported. Consequently, imported soybean oil suffers from GM limitations. The conditions for imports of rapeseed into Europe are that GM varieties must be approved. Because Canada grows genetically modified canola it cannot export to the EU. Curiously, Dubai imports and crushes Canadian canola and exports it to Europe for biodiesel manufacture. Generally, trading companies are not willing to bear the risk of guaranteeing absence of traces of genetically modified organisms (GMO) approved in some third countries but not yet in the EU. By 2007, there is a good chance that two varieties of GM rapeseed will be authorised for import from Canada, which would relieve the feedstock problem. The present strict EU zero-tolerance policy as to GMO is disproportionate, damages European competitiveness and will eventually lead to a complete halt of vital food/feed supplies from North and South America. Europe admits Argentinean GM soy biodiesel. The composition of soybean oil can be modified to improve the usefulness across the food and fuel chain. DuPont has developed a GM soybean plant that gives an oil containing 80% oleic acid. Major US seed companies (DuPont, Monsanto, Pioneer) are in the process of commercialising new soybean varieties that will increase oilseed yields by 9–12% on current acreage (‘virtual acres’ is a term for generating additional feedstock from the same acre). A yield increase of 10% corresponds to an additional 250 Mbu of soybeans, or almost 400 Mgal of biodiesel. These technologies are set to have an impact in 2010. The same benefit can be achieved by increasing soybean oil content. Current industry genetic programmes suggest 10% oil increases are achievable within the next few years, while further research is under way to increase the oil yield of soybean by more than 20% [7]. In this respect, the long-term future of the biodiesel industry looks positive. Recent developments in gene segment transfer and modification techniques

Development of non-food agricultural industries

59

suggest an alternative route for development of diesel fuel from plant sources. Major technology goals of genetic manipulation of energy crops for biodiesel are increased productivity and economic return while providing environmental sustainability (decreased greenhouse gas emissions), reduced agricultural inputs (nutrient requirements and pesticide reduction), tolerance of biotic and abiotic stresses, and control of chemical composition (oil concentration and profiles, introduction of new fatty acids) [8]. The great challenge is doubling biomass yields of energy crops with desirable physical and chemical traits. Development of novel energy crops may proceed in various directions, e.g. along ways to produce triacylglycerols in abundant non-seed tissues, or by improving the fuel characteristics of biodiesel by altering the fatty acid composition. Benefits sought by the biodiesel industry are improved oxidative stability and improved cold-flow properties. These properties are interconnected. Although applications of modern bio- and gene technology are quite likely to provide vegetable raw materials of improved quality and yield, industrial demand requires that these new materials of vegetable origin are made available in sufficient quantities at competitive prices. Plant triacylglycerols as feedstocks for the production of biofuels have recently been reviewed [9]. It has been argued that transgenics are imperative for biofuel crops [10].

2.5

Bibliography

J. Gressel, Genetic Glass Ceilings: Transgenics for Crop Biodiversity, Johns Hopkins University Press, Baltimore, MD (2008). B. Kamm, P.R. Gruber and M. Kamm (eds), Biorefineries – Industrial Processes and Products, Wiley-VCH, Weinheim (2006), 2 vols. Nexant, Inc. ChemSystems, Liquid Biofuels: Substituting for Petroleum (multiclient study), White Plains, NY (2006). J. Outlaw, K. Collins and J. Duffield (eds), Agriculture as a Producer and Consumer of Energy, CABI, Wallingford (2005). G. Boyle (ed.), Renewable Energy, Oxford University Press, New York, NY (2004). J.A. Duke, Handbook of Energy Crops, Purdue University Center for New Crops and Plant Products, West Lafayette, IN (2003); http://www.hort. purdue.edu/newcrop. V. Shiva, Protect or Plunder? Understanding Intellectual Property Rights, Zed Books, London and New York, NY (2001). Organisation for Economic Co-operation and Development (OECD), The Application of Biotechnology to Industrial Sustainability – A Primer, OECD Publishing, Paris (2001). H. Zoebelein (ed.), Dictionary of Renewable Resources, 2nd edn, WileyVCH, Weinheim (2001).

60

Biodiesel science and technology

National Agricultural Biotechnology Council, The Biobased Economy of the 21st Century: Agriculture Expanding into Health, Energy, Chemicals, and Materials, NABC Report 12, Ithaca, NY (2000). G.T.S. Mugnozza, E. Porceddu and M.A. Pagnotta (eds), Genetics and Breeding for Crop Quality and Resistance, Kluwer Academic Publishers, Dordrecht (1999). R.P. Overend and E. Chornet (ed.), Biomass: A Growth Opportunity in Green Energy and Value-Added Products, Pergamon Press, Oxford (1999). D.L. Klass, Biomass for Renewable Energy, Fuels, and Chemicals, Academic Press, San Diego, CA (1998). K. Miyamoto, Renewable Biological Systems for Alternative Sustainable Energy Production (FAO Agricultural Services Bulletin – 128), FAO, Rome (1997). H. Eierdanz (ed.), Perspektiven nachwachsender Rohstoffe in der Chemie, VCH, Weinheim (1996). D.J. Murphy (ed.), Designer Oil Crops, VCH, Weinheim (1994). B.S. Kamel and Y. Kakudo (eds), Technological Advances in Improved and Alternative Sources of Lipids, Chapman & Hall, London (1994). S.L. Mackenzie and D.C. Taylor (eds), Seed Oils for the Future, AOCS Press, Champaign, IL (1992). B.A. Stout, The Handbook of Energy for World Agriculture, Elsevier, Amsterdam (1990). O. Kitani and C.W. Hall, Biomass Handbook, Gordon & Breach, New York, NY (1989). G. Leach, Energy and Food Production, International Institute for Environment and Development, London (1975).

2.6

References

[1] H. Zoebelein (ed.), Dictionary of Renewable Resources, 2nd edn, Wiley-VCH, Weinheim (2001). [2] S.C. Gray, Oils and fats: An industrialist’s view, in New Crops for Temperate Regions (K.R.M. Anthony, J. Meadly and G. Röbbelen, eds), Chapman & Hall, London (1993), pp. 179–86. [3] B. Kerckow, C. Mangan and L. Breslin, Industrial crops and products and European Union research policy, Ind. Crops Prod. 6 (1997) 325–31. [4] R.D. Perlack, L.L. Wright, A. Turhollow, R.L. Graham, B.J. Stokes and D.C. Erbach, Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply, US Dept. of Energy, Oak Ridge National Laboratory, DOE/90-102005-2135 (2005), pp. 1–78. [5] P. Lamers, K. McCormick and J.A. Hilbert, The emerging liquid biofuel market in Argentina: implications for domestic demand and international trade, En. Policy 36 (2008) 1479–90. [6] International Service for the Acquisition of Agri-Biotech Applications, ISAAA, Manila/Nairobi/Ithaca (2006).

Development of non-food agricultural industries

61

[7] www.danforthcenter.org. [8] B.J. Calabotta and K. Burger, Application of molecular and genetic technologies to improve feedstock supplies for biodiesel production, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [9] T. Durrett, C. Benning and J. Ohlrogge, Plant triacylglycerols as feedstocks for the production of biofuels, Plant J. 54 (2008) 593–607. [10] J. Gressel, Transgenics are imperative for biofuel crops, Plant Sci. 174 (2008) 246–63.

3

Oleochemical sources: basic science, processing and applications of oils

Abstract: Natural lipid biosynthesis is regulated by enzymatic activity and leads to a broad variety of oils in seeds and fruits in which a restricted subset of fatty acid compositions predominates and accounts for the traditional use of oils and fats in food and oleochemical applications. Both genetic and environmental factors affect triacylglycerol (TAG) biochemistry. Manipulation of fatty acid and TAG synthesis for the purpose of usability for both nutritional and industrial applications by means of natural breeding methods and genetic engineering techniques rely on detailed knowledge of biochemical pathways. The features of various oil recovery and refining techniques are outlined and the applications of unusual fatty acids are described. Key words: Biosynthesis and biodegradative pathways, plant breeding, genetic engineering, vegetable oil processing techniques, unusual fatty acids.

3.1

Introduction

The primary components of oils and fats are esters of fatty acids (FAs) and glycerol that can be obtained from several natural sources (vegetable, animal and marine). The world production of plant oils amounted to 127 Mt in 2006 [1]. The annual production of animal fats (tallow, lard and butter) is approximately 22 Mt, while fish oils contribute about 1 Mt/yr. If a lipid is a solid at 298 K, it is classified as a fat; otherwise, it is an oil. Most triglycerides found in animals are fats, while those in plants tend to be oils. Irrespective of origin, these materials have identical chemical structures and very similar chemical compositions. In typical vegetable oils ‘only’ some 25–50 FAs are present at meaningful levels. In more complex animal fats or oils the number of FAs is easily as high as 100. The basic structure of a triacylglyceride is a three-carbon hydroxycarbon (dehydrated glycerol) with three short to (very) long-chain (C8 to C30) fatty acids attached. The use of the oil or fat is determined by the composition of fatty acids, and this is highly dependent on its natural origin. Animal sources are characterised by high concentrations of saturated fatty acids, whilst marine sources (fish oils) are rich in very long-chain polyunsaturated fatty acids (VLCPUFAs). The fatty acid composition of oils from vegetable sources varies depending on plant origin and sort. Plant oils consist almost entirely of triacylglycerol (TAG) esters containing three fatty acids with 62

Oleochemical sources

63

chain lengths of C8-C24, with C16 and C18 being the most common. None of the VLCPUFAs are normally produced by higher plants. A striking feature of naturally occurring fatty acids is that they almost entirely contain an even number of carbon atoms. Since one molecule of glycerol is combined with three molecules of fatty acid, either simple triglycerides (where all acyl groups are alike) or mixed triglycerides (consisting of two or three different acyl constituents) are possible. It is unusual to find any simple triglyceride in a vegetable oil unless a considerable excess of one fatty acid is prevalent. In the case of tung oil, which contains 75–85% eleostearic acid, the triglycerides of this acid can be separated. Table 3.1 indicates the nomenclature of the most common fatty acids. Shorthand fatty acid designations are based on the length of the acyl chain and the number and positions of double bonds. A frequently used fatty acid nomenclature is L:Dn – x, where L = chain length, D = number of double bonds and n – x = position of the ultimate double bond from the terminal methyl group. For example, soybean oil contains about 20.7% C18:1n – 9c (cisoleic acid) and 1.22% C18:1n – 9t (trans-oleic or elaidic acid) [2]. Similarly, Table 3.1 Fatty acid nomenclature   Structurea Fatty acid

Systematic name

Formula

C6:0 C8:0 C10:0 C12:0 C14:0 C16:0 C18:0 C20:0 C22:0 C24:0 C26:0 C16:1 C18:1 C18:1 C18:1 C18:1-OH C18:1>O C18:2 C18:3 C18:3 C20:1 C20:1-OH C20:4 C22:1

Hexanoic Octanoic Decanoic Dodecanoic Tetradecanoic Hexadecanoic Octadecanoic Eicosanoic Docosanoic Tetracosanoic Hexacosanoic 9-Hexadecenoic cis-9-Octadecenoic trans-9-Octadecenoic cis-6-Octadecenoic 12-Hydroxy-cis-9-octadecenoic 9,10-Epoxy-octadec-cis-12-enoic cis, cis-9,12-Octadecadienoic cis, cis, cis-9,12,15-Octadecatrienoic cis, trans, trans-9,11,13-Octadecatrienoic cis-9-Eicosenoic 14-Hydroxy-cis-11-eicosenoic 5,8,11,14-Eicosatetraenoic cis-13-Docosenoic

C6H12O2 C8H16O2 C10H20O2 C12H24O2 C14H28O2 C16H32O2 C18H36O2 C20H40O2 C22H44O2 C24H48O2 C26H52O2 C16H30O2 C18H34O2 C18H34O2 C18H34O2 C18H34O3 C18H32O3 C18H32O2 C18H30O2 C18H30O2 C20H38O2 C20H38O3 C20H32O2 C22H42O2

a

Caproic Caprylic Capric Lauric Myristic Palmitic Stearic Arachidic Behenic Lignoceric Cerotic Palmitoleic Oleic Elaidic Petroselenic Ricinoleic Coronaric Linoleic a-Linolenic Eleostearic Gadoleic Lesquerolic Arachidonic Erucic

xx:y indicates xx carbons in the fatty acid chain with y double bonds. Chemical names include isomeric variations.

64

Biodiesel science and technology

lard contains about 38% oleic acid and 2.35% elaidic acid. Alternatively, the position of the first carbon of a double bond counting from the carboxyl group is designated by delta (D), or the position of a double bond relative to the terminal methyl group is designated by omega (w). The double bonds in naturally occurring fatty acids are almost all in cis(Z)-configuration and, therefore, a designation is only used in case of a trans(E)-isomer. There are three main classes of triglycerides: saturated fats, unsaturated cis-fats and trans-fats. Most natural vegetable oils consist of cis-fats and are polyunsaturated. The cis nature prevents solidification of the fat; trans-fats solidify more readily and may increase blood cholesterol levels. Nutritionists distinguish various fatty acid diets (Table 3.2) and currently insist on reduced trans-isomer content of hardstocks despite lack of scientific justification for a causal relation between high cholesterol levels and heart disease [3].

3.2

Biochemistry of lipid metabolism

In many plants, lipids (insoluble in water) represent up to 80% of dry weight of storage tissues. Lipids are an essential constituent of all plant cells, are extremely diverse in structure and constitute the products of several distinct biosynthetic pathways. The most abundant types of lipids in most cells are those that derive from the fatty acid and glycerolipid biosynthetic pathways [4–8]. The fatty acid biosynthesis pathway is a primary metabolic pathway, because it is found in every cell of the plant and is essential to growth. In annual oil crops five main fatty acids, namely saturated palmitic (C16:0) and stearic (C18:0) acids, monounsaturated oleic acid (C18:1) and polyunsaturated linoleic (C18:2) and linolenic (C18:3) acids (and in some species also C16:1-transD3), make up over 90% of the acyl chains of structural (glycero)lipids of almost all plant membranes. However, many variations on the theme are possible. The ratio of the amounts of the two most common (adjacent) saturated fatty acids (C16:0 and C18:0) present in almost every vegetable oil remains fairly constant for the same oil and differs for other oils. Accordingly, the palmitate to stearate methyl ester (P/S) ratio can constitute an identifying feature of an oil. Literature values for average Table 3.2 Fatty acid diets   Diet

Exemplary nutritional component

Structurea

w-3 w-6 w-9 w-6/w-9 Saturated

Fish oil Sunflower oil Olive oil Argan oil Coconut oil

20:5, 22:5, 22:6 18:2 18:1 18:1, 18:2 £ 14:0

a

xx:y indicates xx carbons in the fatty acid chain with y double bonds.

Oleochemical sources

65

P/S ratio are typically about 1.5 for linseed oil, 2.5 for walnut oil, and 5.0 for poppyseed oil. Several hundred different fatty acid structures have been found to occur in oil seeds and oil fruits, indicating a broad biosynthetic flexibility with regard to both fatty acid and TAG synthesis [9]. Each plant has a typical fatty acid pattern that is determined by its enzyme configuration. Control mechanisms of fatty acid and TAG synthesis are complex and not yet completely understood. Plants differ fundamentally from other eukaryotes in the molecular organisation of the enzymes of fatty acid synthesis. Although fatty acids are major constituents of every membrane in a cell and are also found outside cells in the cuticular lipids, the individual enzymes of the fatty acid synthesis pathway in plants are dissociable soluble components located in the stroma of plastids. In this respect, lipid biosynthesis in plants is fundamentally different from that in animals, fungi and some bacteria, where all of these reactions are catalysed by a multifunctional peptide complex located mainly in the cytosol. The plastid localisation of fatty acid synthesis means that unlike animals and fungi, plants must have mechanisms to export fatty acids from the plastid to other sites in the cell.

3.2.1 De novo fatty acid biosynthesis The first stage of lipid metabolism, the fatty acid synthesis, is illustrated here in particular for the case of oil fruits such as olive, palm and avocado [10, 11]. It is possible to explain the oil composition of these species as a function of the biochemical parameters of the enzymes present in the fruit mesocarp tissues. Unlike seeds, the TAGs that constitute the fruit oil in these species are produced from both the photosynthates imported from the leaves as well as the CO2 fixed in the fruit itself. The biosynthesis of oil in the mesocarp of oil fruits has been well studied. In particular, avocado has been a very important oil fruit for understanding of lipid metabolism in higher plants. Fatty acid synthesis is a process that occurs in plant plastids and needs the concerted action of two enzymes, acetyl-CoA carboxylase (ACCase) and fatty acid synthase (FAS). In plants, animals, yeast and E. coli, ACCase is a regulatory enzyme that controls, at least in part, the rate of fatty acid synthesis (light/dark regulation). Two forms of ACCase occur in plants, termed prokaryotic and eukaryotic. Which type of ACCase structure is present depends on its subcellular localisation and the type of plant. The all-important precursor for de novo fatty acid biosynthesis is acetylCoA. A major unresolved question in plant metabolism is how acetyl-CoA in chloroplasts is generated. Plastid ACCase catalyses condensation of a molecule of bicarbonate with acetyl-CoA to produce malonyl-CoA (Fig. 3.1), which

66

Biodiesel science and technology

is the key intermediate and central carbon donor in fatty acid biosynthesis. However, before entering the fatty acid synthesis pathway, the malonyl group is transferred from CoA to a protein cofactor, acyl carrier protein (ACP), by malonyl-CoA: ACP transacylase. ACP is a small (9 kDa) acidic protein that contains a phosphopantethein prosthetic group to which the growing acyl chain is attached as a thioester. All the subsequent reactions of the fatty acid synthesis pathway involve ACP until a 16- or 18-carbon product is ready for transfer to glycerolipids or export from the plastid. Overall, to produce C16 or C18 fatty acids from acetyl-CoA and malonyl-CoA, at least 30 enzymatic reactions are required. Plant fatty acid synthesis is based on discrete enzyme components: various b-ketoacyl-ACP synthases (KAS), b-ketoacyl-ACP reductase, 3-hydroxyacylACP dehydrase and enoyl-ACP reductase. The condensing b-ketoacyl-ACP synthases differ in their substrate specificities: KAS I appears to be specific for elongating substrates ranging from C4 : 0- to C16: 0-ACP, and KAS II for elongating C16 : 0-ACP; KAS III is the enzyme of the FAS complex responsible for the first chain-lengthening step and catalyses the condensation of acetyl-CoA and malonyl-ACP; KAS IV directs its condensing activity towards medium-chain acyl-ACP substrates [12]. The cycle of elongation starts with condensation of malonyl-ACP with acetyl-CoA by the action of KAS III to produce acetoacetyl-ACP, which is subsequently reduced by b-ketoacyl-ACP reductase, dehydrated by 3-hydroxyacyl-ACP dehydrase and finally reduced by enoyl-ACP reductase (Fig. 3.1). The resulting four-carbon butyryl-ACP derivative can undergo further elongation. These condensations are catalysed by KAS I, which uses acyl-ACPs as substrates rather than acetyl-CoA, as for KAS III. The combined action of four reactions thus leads to lengthening of the precursor fatty acid by two carbons at a time while it is still attached to ACP as a thioester. The condensing enzyme KAS I is believed responsible for producing chain lengths from 6 to 16 carbons; the final product of these condensation cycles is palmitoyl-ACP (Fig. 3.1) [13]. This compound can be chain elongated to stearoyl-ACP involving participation of condensing enzyme KAS II. The latter step determines the C16/C18 ratio of the resulting mix of fatty acids. This ratio is also directly related to the degree of unsaturation of the final oil product, because palmitate is the most usual saturated fatty acid in vegetable oils whereas C18 acids are almost entirely unsaturated. The process of fatty acid synthesis de novo finishes, i.e. elongation of fatty acids in the plastids is terminated with the release of the acyl moieties from the ACP derivatives by the action of plastid thioesterases (TE) or their transfer into complex lipids by acyltransferases (see Fig. 3.2). In most cases, a specific acyl-ACP thioesterase hydrolyses the acyl-ACP and releases the free fatty acid. Thioesterases are indicated as important chain length determining enzymes and responsible, in combination with condensing enzymes, for the

O

O

HCO3–

O

O

ACP

Acetyl-CoA carboxylase

O

O

–

S-CoA

O

Acetyl-CoA

KAS III –

S-CoA

O

Acetyl-CoA

Malonyl-CoA : ACP transacylase

O

S-ACP

Malonyl-CoA

S-ACP

Malonyl-ACP

3-Ketobutyryl-ACP

+ H+ (1)

O

O

O

O + H+

Malonyl-ACP KAS I

S-ACP

S-ACP

3-Ketoacyl-ACP

OH

O

–H2O (2)

(3)

S-ACP

Butyryl-ACP

Butenoyl-ACP

S-ACP 3-Hydroxybutyryl-ACP

O Malonyl-ACP

S-ACP Palmitoyl-ACP

KAS II

O

O

O S-ACP

(1) (2) (3)

S-ACP

Oleochemical sources

KAS I Malonyl-ACP x5

Stearoyl-ACP

67

3.1 Biosynthesis of fatty acids (in oil fruits) by fatty acid synthase. Key: ACP, acyl carrier protein; KAS (I, II, III), b-ketoacyl-ACP synthases; (1) b-ketoacyl-ACP reductase; (2) 3-hydroxyacyl-ACP dehydrase; (3) enoyl-ACP reductase (after ref. [11]).

Cytoplasm

Biodiesel science and technology

3.2 Simplified scheme of fatty acid biosynthesis malonyl-CoA malonyl-CoA in plants. Fatty acids are first synthesised de FatA 22 : 1-CoA 18 : 1 18 : 1-CoA 20 : 1-CoA ACP novo as ACP thioesters 24 : 1-CoA KCS KCS in the plastid. Upon Glycerol-318 : 1-ACP hydrolysis (FatA, FatB), D9-DES phosphate G3PAT the resulting ‘free’ fatty ACS 18 : 0-ACP acids are able to cross Acyl–CoA LPA the plastidial membrane pool KAS II P R 16 : 0-ACP FatB into the cytoplasmic compartment, where R-CoA Free they are esterified LPAAT FatB 18 : 1-PC 14 : 0-ACP with CoA, catalysed D12-DES by acyl-CoA synthase 18 : 2-PC (ACS). Acyl-CoAs can PA 12 : 0-ACP FatB fatty be further processed by D15-DES R R P phospholipid-dependent FatB 18 : 3-PC desaturation and KAS I 10 : 0-ACP PAP other modifications, acids or elongated with 8 : 0-ACP FatB KAS IV b-ketoacyl-CoA DAG CPT synthase (KCS). Final R R 6 : 0-ACP TAG formation can be attained either by R-CoA stepwise acylation DAGAT R R PC 4 : 0-ACP along the glycerol-3KAS III PDAT Oil body phosphate (G3P) route or by several acyl-CoAR R R independent pathways, Acetyl-CoA Malonyl-ACP TAG involving CPT and PDAT De novo fatty acid biosynthesis Triacylglycerol biosynthesis (after ref. [14]).

68

Plastid

Oleochemical sources

69

chain length distribution of the products of fatty acid synthesis in plants, and especially in the oils of seed storage tissues [15, 16]. Most species, including oil fruits, dispose of thioesterases with high substrate specificity for C18-acyl-ACPs [17]. Acyl-ACP thioesterases are classified into the FatA type preferring oleoyl-ACP as substrate and the FatB enzymes that usually hydrolyse saturated acyl-ACP. High content of palmitate in palm oil is explained by low KAS II activity and an important C16 acyl-ACP thioesterase activity that releases C16 moieties in the mesocarp of oil palm fruit [11]. Alternatively, one of two highly selective acyltransferases (AT) in the plastid transfers the fatty acid from ACP to glycerol-3-phosphate (G3P) or to monoacylglycerol-3-phosphate (LPA) to initiate the synthesis of plastidial membrane lipids followed by further desaturations. The first of these acyltransferases is a soluble enzyme that prefers oleyl-ACP as a substrate. The second acyltransferase resides on the inner chloroplast envelope membrane and preferentially selects palmitoyl-ACP. Whether the fatty acid is released from ACP by a thioesterase or an acyltransferase determines whether it leaves the plastid. If a thioesterase acts on acyl-ACP, then the free fatty acid is able to leave the plastid for export to the acyl-CoA and acyl-lipid pools, presumably by simple diffusion across the envelope membrane. The products of the fatty acid biosynthesis pathway in oil fruits are thus mainly saturated C16 and C18 acyl chains. However, in most plant tissues, over 75% of the fatty acids are unsaturated species, like oleate or linoleate. Most plants dispose of the necessary mechanisms to introduce double bonds into specific positions of the acyl chains synthesised by the FAS reactions. The first double bond is introduced by the very active plastid-localised soluble enzyme D9-stearoyl-ACP-desaturase (D9-DES), which leads to oleate rather than stearate accumulation in most plant species [18]. This fatty acid desaturase is unique in the plant kingdom in that all other known desaturases are integral membrane proteins. In some plants, 16 : 0-ACP is further modified by a soluble enzyme (representing a diverged form of the soluble desaturase that is typically involved in conversion of 18:0-ACP to 18 : 1D9-ACP) that introduces a double bond at the D4 or D6 position. In plants, oleate is a central metabolite by virtue of its position in lipid biosynthesis [19]. It is the end product of the ‘ACP-track’ set of fatty acid biosynthetic reactions in the plastid using acyl carrier protein (ACP) as the acyl carrier, and at the same time the starting point for another set of modifying reactions localised elsewhere [20]. The enzymes stearoyl-ACP desaturase and acyl-ACP hydrolase guarantee termination of fatty acid synthesis at the 18:1(9) level in the chloroplast (leaf) or in the proplastid (seed) [21]. Much is known also about the biosynthesis of oleic acid in animal systems. Apart from the three standard fatty acids, palmitic (16 : 0), stearic (18 : 0) and oleic (D9-18 : 1), required for the biosynthesis of all cellular membrane

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lipids, plastids can produce a variety of other fatty acids varying in chain length (8 : 0 to 14 : 0) and location of a single double bond (D9-14 : 1, D616 : 1, D9-16 : 1, D6-18 : 1). These fatty acids, once exported to the cytosol, enter the acyl-CoA and acyl-lipid pools. Enzyme activities responsible for controlling the flux of fatty acids between phospholipid and acyl-CoA pools require further elucidation. Esterification with CoA is catalysed by acyl-CoA synthase (ACS) located in the extraplastidial membranes. Modifications of oleate, such as elongation to VLCFAs or reduction, take place outside the plastid, primarily on membrane systems in the cytosol. Elongation of oleic acid (18 : 1) to erucic acid (22 : 1) is a major malonylCoA-dependent pathway in some oilseeds, such as Brassica napus, which presumably depends on the cytosolic ACCase enzyme. When used for storage lipid synthesis, a large proportion of all fatty acids exported from plastids is incorporated into microsomal phospholipids (particularly phosphatidylcholine, PC) for various modifications (desaturation, hydroxylation, epoxidation, acetylation, conjugation, elongation, reduction) to produce polyunsaturated and unusual fatty acids (C18*); see also Fig. 3.6. Even fatty acids not subject to any modification may pass through PC for subsequent channeling into reserve lipids which mostly are triacylglycerols (TAGs). Although desaturation of oleate to produce polyunsaturated fatty acids can take place either in the plastid or in the endoplasmic reticulum via prokaryotic or eukaryotic pathways, respectively [16, 22], for many plants (including olive, palm and avocado) such desaturation involves transportation of oleate out of the plastid to the cytosol [23]. Oleic acid (18 : 1) incorporated into phosphatidylcholine (PC) in the ER is available for conversion to linoleic (18 : 2 D9, 12) and then a-linolenic (18 : 3 D9, 12, 15) acid by the sequential action of substrate-specific desaturases. Oleoyl desaturase is the enzyme responsible for conversion of oleic to linoleic acid, and linoleoyl desaturase is involved in the conversion of linoleic to a-linolenic acid. As biosynthesis of C18 : 2 and C18 : 3 acids utilises C18 : 1 acid as primary substrate, the concentration of the latter decreases as they are produced (see Fig. 3.3 for pecan oil). For biosynthesis of PUFAs in eukaryotic algae, see ref. [24].

3.2.2 Triacylglycerol biosynthesis Fatty acids in cells are almost never found as ‘free’ fatty acids. Instead, their carboxylic group is esterified or otherwise modified. A proportion of the fatty acid products formed is retained as structural components of cellular membranes (e.g. phospholipids of the ER and galactolipids of plastids) and the rest is transferred to TAG by a variety of potential routes. In membrane glycerolipids, fatty acids are attached to both the sn-1 and sn-2 positions of the glycerol backbone and a polar headgroup is attached to the sn-3 position. If

Oleochemical sources

71

3.2 [C18 : 2] = 76.475–0.805 · [C18  : 1]

34

[C18 : 3] = 5.929–0.057 · [C18 : 1]

3.0 2.8

30 28

2.6

26

2.4

24

2.2

22

2.0

20

Linolenic acid (% wt/wt, oil basis)

Linoleic acid (% wt/wt, oil basis)

32

1.8

18 1.6 54

56

58 60 62 64 66 68 70 72 Oleic acid (% wt/wt, oil basis)

74

76

3.3 Linear regression of oleic concentration on the concentration of linoleic and linolenic acids in pecan oil (after ref. [25]).

all three positions on glycerol are esterified with fatty acids, a TAG structure results that is not suitable for membranes but instead constitutes the major form of lipid storage in seeds. All the major steps in the biosynthetic pathway of TAG are now known. The 16:0 and 18:1 acyl chains produced in the plastid are to form the hydrophobic portion of glycerolipid molecules. Glycerolipid synthesis comprises acylation reactions that transfer fatty acids to glycerol-3-phosphate (G3P). Higher plants possess two distinct pathways for the synthesis of glycerolipids. The prokaryotic pathway occurs in the plastids, uses acyl-ACPs as substrates, and esterifies predominantly palmitate (16 : 0) at position 2 of glycerol. The eukaryotic pathway of assembling acyl chains to the glycerol backbone is extra-plastidial (primarily at the endoplasmic reticulum), uses acyl-CoAs as substrates, and positions 18-carbon fatty acids at position 2 of glycerol-3phosphate. The details of the synthetic routes that probably operate in higher plants have been reviewed [4]. In almost all plants, the chemical form in which oil is stored is as triacylglycerols, which are formed by an extension of the membranelipid biosynthetic pathway common to all plant tissues. In some species TAG biosynthesis has been proposed to take place by the comparatively straightforward Kennedy pathway, which essentially involves re-entry into the acyl-CoA pool and attachment to all three positions of TAG by consecutive

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reactions catalysed by various acyltransferases (G3PAT, LPAAT, PAP, DAGAT), which attach CoA-activated fatty acids to the glycerol backbone [26] (see Fig. 3.2). Fatty acids are sequentially transferred from CoA to positions 1 and 2 of glycerol-3-phosphate, resulting in the formation of phosphatidic acid (PA). Dephosphorylation of PA releases diacylglycerol (DAG). In the final step of TAG synthesis, a third fatty acid is transferred to the vacant position 3 of DAG. This step is catalysed by diacylglycerol acyltransferase (DAGAT), the only enzyme of the G3P pathway unique to storage lipid synthesis [27]. The specificity of the acyltransferases of the Kennedy pathway represents an important aspect of lipid metabolism because they broadly determine the fatty acid composition of the accumulating species. Assembly of free fatty acids into the glycerol backbone does not always proceed according to the Kennedy pathway as in many oilseeds most fatty acids produced in the plastid are not immediately available for TAG biosynthesis. Formation of TAG from DAG may occur in the absence of acyl-CoA without DAGAT activity. The acyl-CoA-independent pathway to TAG involves phosphatidylcholine (PC) with either direct transfer from phospholipids to diacylglycerol (DAG) by an enzyme called phospholipid:1,2-diacylglycerol acyltransferase (PDAT) or removal of the phospholipid headgroup to form DAG, which can subsequently be utilised by DAGAT or PDAT to form TAG [4]. Storage of TAGs synthesised in the endoplasmic reticulum (ER) in mature oil seeds involves formation of small spherical (about 1 mm diameter), and densely packed cytosolic oil bodies, surrounded by monolayer phospholipid membranes. Accumulation of oil then means an increase in the number of such lipid bodies. Unlike seeds, in oil fruits like olive most of the oil accumulates in larger and oleosin-free droplets formed in the fleshy pericarp [28]. It is estimated that plants contain thousands of fatty acid structures, many of which arise by the action of membrane-bound desaturases and desaturase-like enzymes. How plants exert control on which fatty acids are stored in triacylglycerol is unknown. This question is particularly relevant for storage of ‘unusual’ fatty acids. More than 300 different fatty acids are known to occur in seed TAG [29, 30]. The acyl groups of seed TAGs can vary in chain length (from 8 to 24). In addition, the position and number of double bonds may vary and unusual functional groups such as hydroxy, oxirane or acetylene may be added to the acyl group (see Section 3.5). The reason for this great diversity in plant storage oils is unknown. The observed divergence in seed oil acyl chains among different species is very high, in contrast to the narrow fatty acid composition of membrane lipids, which exclude unusual fatty acids. The details of ‘unusual’, e.g. hydroxyl or conjugated, fatty acid formation remain elusive, because these enzymes await structural characterisation. However, soluble plant acyl-ACP desaturases have been studied in far greater detail but typically only catalyse desaturation (dehydrogenation) reactions.

Oleochemical sources

73

A recent study has contributed detailed mechanistic insights into factors that govern the highly selective production of unusual fatty acids [31]. A mutant of the castor acyl-ACP desaturase converts (E)-9-18 : 1-ACP into two major products: (Z)-10-18 : 1-9-OH and the conjugated linoleic acid isomer (E)-9(Z)-11-18:2 (Fig. 3.4). In recent years, knowledge of the biochemical relationships of plant metabolism – in particular of the biosynthesis of the storage fats in commercial use – has increased considerably [27, 28, 32–34]. Voelker and Kinney [27] have reviewed variations in the biosynthesis of seed-storage lipids. Seed oils normally contain predominantly C18 unsaturated fatty acids; saturated fatty acids represent only a minor fraction [9]. The saturated acyl groups are normally found only in the sn-1 and sn-3 positions of triacylglycerols [35]. In fact, highly saturated oils from different plants fall into two classes with respect to the fatty acyl distribution in the TAG structure. On the one hand, in cocoa butter (containing 60 mol% SFA) the saturated fatty acids (predominantly 16 : 0 and 18 : 0) reside almost exclusively in the sn-1 and sn-3 positions of the (saturated-unsaturated-saturated) TAGs. Similarly, in highly saturated canola oil (BTE canola) with 48% C12 : 0 (total SFA: 60%) 12 : 0 is also located almost exclusively at sn-1 and sn-3 positions of triacylglycerols; with only 4% sn-2 laurate almost no trilaurin accumulates [36]. On the other hand, oils of medium-chain (C8-C14) producing species (including many palms, Lauraceae, Myristiacaceae, and Cuphea spp.) contain almost exclusively saturated fatty acids. For example, coconut (Cocos nucifera) oil contains 92% SFA, predominantly laurate, and most of its TAGs are trisaturated. Laurate is found enriched at sn-2, which indicates that a laurate-CoA-preferring LPA (lysophosphatidic acid) acyltransferase is active during endosperm maturation [37]. Positional isomerism is obviously of no concern to biodiesel production. 11

ra

se

9

de

sa

tu

OH

9

desaturase

de

t sa

ur

10

e

C~

as

~C

9

11 10

3.4 Enzymatic conversion of stearoyl-ACP by mutant desaturase into an allylic alcohol and linoleic acid isomer (after ref. [31]).

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Biodiesel science and technology

3.2.3 Biodegradative pathways Biodegradative pathways are strongly involved in vegetable oil quality. Lipolytic activities in the oil palm fruit mesocarp are important for the acidity of the final oil product. Oil palm fruit lipases are particularly important because they are responsible for the increase in oil acidity in certain conditions. While polyunsaturated fatty acids are not usually in a free state in plants, but mainly esterified to glycerol in the form of membrane or storage lipids, their prior release by the action of lipolytic acylhydrolases is necessary [11]. Hydrolysis of lipids by lipase is induced by fruit bruising and/or poor storage. Once the polyunsaturated fatty acids have been released, they can be oxidised by the action of lipoxygenase (LOX) [38]. The fact that olive LOX oxidises free unsaturated fatty acids at a much higher rate than esterified ones confirms that action of an acylhydrolase releasing C18:2 or C18:3 acids for the glycerolipid fraction is necessary prior to their oxygenation. Among the catabolic pathways related to lipids, the so-called lipoxygenase pathway is also particularly important in view of sensory quality (relevant for oil fruits, e.g. olive). Virgin oil aroma consists of a complex mixture of more than 100 compounds, mainly volatile saturated and unsaturated aldehydes, alcohols and esters [39]. These compounds are produced from polyunsaturated fatty acids through a cascade of reactions (lipoxygenase pathway). The LOX pathway involves oxidative degradation of polyunsaturated linoleic and a-linolenic acids, which are split into volatile C6 or C9 carbonyl fragments, which can further be modified by isomerisation, reduction and esterification (Fig. 3.5). In the case of olive oil, the lipoxygenase pathway is principally triggered during crushing of olive fruits and malaxation of the resulting pulp that takes place in the extraction process. The aroma of a given oil is a function of the activity levels and characteristics of the enzymes involved in that cascade of reactions. There exists a relationship between the activity level and the characteristics of the LOX pathway enzymes in olive pulp with the quality of the sensory components of the resulting olive oil [11]. The same phenomenon does not occur in other oil fruits (palm fruit, avocado). The extraction process of oil palm includes sterilisation (by heating) to inactivate enzymes such as endogenous lipases, which also cause inactivation of LOX pathway enzymes [40]. Aroma is not a quality parameter of palm oil.

3.2.4 Environmental factors As indicated in Table 3.3, lipid biosynthesis is also affected by environmental factors (light, temperature, water stress, soil and atmospheric constituents) and biotic factors such as physical damage and pest attack, which play an important quantitative and qualitative role in terms of oil yield and fatty acid profile. Ecological factors (and consequently some geographical areas) are

Oleochemical sources Polyunsaturated glycerolipids

Lipolytic acylhydrolase

75

Free polyunsaturated fatty acids

O2 LOX

Oxoacids Aldehydes + (non-volatile) (volatile)

HPL

Hydroxyperoxides

EI, ADH, AAT

Modified volatiles

3.5 Biosynthesis of volatiles from polyunsaturated fatty acids by the lipoxygenase pathway. Abbreviations: AAT, alcohol acyltransferase; ADH, alcohol dehydrogenase; EI, enal isomerase; HPL, hydroperoxide lyase; LOX, lipoxygenase. Table 3.3 Some factors affecting lipid biosynthesis ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Genetic variations Enzyme activity (synthetases, desaturases, acyl-tranferases, thioesterases, etc.) Ecological and environmental factors (climate conditions: light temperature; geographical area: soil and atmospheric constituents) Water management (water regime and water stress) Souring date Seasonal variations Seed development stage (maturity, post-maturity) Bioetic factors (physical damage, pest attack)

more favourable than others for the production of a given botanical species as an industrial oilseed crop. Oil content varies by region due to climatic and other environmental factors. For example, spring canola in Oregon has significantly lower oil content (32%) than that of North Dakota and Canada (43%). Also the fatty acid profile of sunflower oil is greatly affected by climatic conditions (N. Dakota: C18 : 1, 15%; C18 : 2, 75%; Texas: C18 : 1, 50%; C18 : 2, 35%). High irradiation may improve the oil content of a crop. Differences of oil content among olives located in different parts of the tree have been noticed [41]. Seasonal variations in vegetable oil yield and quality are observed. Temperature affects lipid metabolism. The effects of air temperature variations

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Biodiesel science and technology

on oil content and fatty acid composition of plants are well documented [9, 42–47], as shown for RSO, SNO, SFO, LSO, CAS and others, and generally show an increased synthesis of total cellular lipids and unsaturated fatty acids at lower temperature. The activity of diacylglycerol acyltransferase (DAGAT) is limited within the TAG production process in olives at T > 303 K [11], which agrees with the reported instability of this enzyme in Brassica napus at T > 313 K [48]. Temperature also has an effect on the catabolic pathways related to lipid metabolism. For example, lipolytic activity increases following exposure to chilling temperatures in oil palm and leads to increased free fatty acid levels [49]. HPL is rather unstable above 293 K. As most of the palm oil is synthesised in the last two weeks of fruit development, a correct judgement of ripeness is essential to ensure good yield. Over-ripeness leads to biodeterioration and poor quality oil and lower mill efficiency. During seed development, the fatty acid composition changes considerably with maturity or with air temperature, as observed for Lesquerella fendleri in relation to harvest date [50]. Triglyceride and fatty acid compositions in the mesocarp of avocado (Persea americana) during fruit development were reported [51]. In the period between harvesting and full maturation (post-harvest period), the oil content increases and change occurs in the oil composition [52]. Water management is another important factor in seed production. Water stress during peak flowering and seed development reduces yields. Changes in seed yield and fatty acid composition of oils of high oleic sunflower (Helianthus annuus L.) hybrids in relation to the sowing date and water regime were reported [53]. Water stress influences the C18 : 1/C18 : 2 ratio. The attack of pests causes an appreciable loss of yield in most oil fruits and causes a loss of quality of the final product due to the increase of acidity and appearance of off-flavours. The involvement of the LOX pathway in plant wound response mechanisms is well known [38]. In addition, the production of volatile aldehydes through the LOX pathway is also related to plant defence mechanisms.

3.3

Modification of vegetable oil quality

As the production of plant oils needs to be expanded, plant biology has to play a critical part in the large-scale development of biodiesel by addressing some of its major limitations. Durrett et al. [54] have outlined some speculative strategies for the design of new crops to produce biodiesel, including considerations on increasing plant oil production, and on oil (instead of carbohydrate) production in vegetative tissues, such as leaves or stems rather than seeds. Altering the fatty acid profile can improve fuel properties of biodiesel such as cold-temperature flow characteristics, oxidative stability and NOx emissions (see Sections 14.4.1–3).

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Each plant has a typical fatty acid pattern that is regulated by its enzyme configuration. An increase of the content of an existing or a new fatty acid in order to facilitate industrial processing of the raw material is one of the most important objectives of genetic engineering in oil crops. Current knowledge of the biosynthesis of TAGs is the basis for the future improvement of yield, quality or composition of oil produced from seeds and fruit. It follows from Section 3.2 that manipulation of both fatty acid and TAG synthesis may lead to developing seeds or fruits which produce the desired fatty acid in high rates and effectively incorporate it into each position of the triglyceride [55–57]. Already, an increased knowledge of how plants synthesise fatty acids has enabled successful engineering of the composition of plant oils, thereby providing a biodiesel with better fuel properties [58]. Many complex biochemical pathways have been manipulated genetically to produce fatty acid compositions having increased oleate level, decreased linoleate, linolenate, stearate, and/or palmitate levels, and a decreased overall level of saturates [59, 60]. A modification of typical fatty acid patterns may be derived by increasing or reducing enzyme activities (Fig. 3.2). Acyltransferases, especially 1-acylglycerol-3-phosphate (G3PAT), are important in determining oil quality and usability for industrial application [35]. Evidence has been provided that expression of acyltranferase genes in transgenic rapeseed plants can improve not only quality but also oil yield. The generation of transgenic soybean lines with high oleic acid content [61] is an example in which plant biotechnology has already contributed to the improvement of biodiesel. The diversity of fatty acids represents a major opportunity for the rational design of new seed oils in domesticated oil crops both for food and nonfood use. Natural breeding methods have been used for many years to try and increase the desired components in conventional industrial crops, and in recent times this method has been supplemented by direct mutagenesis and other genetic engineering techniques. In addition to improved crop yielding ability, the oil concentration and composition of the storage lipids may be enhanced through advanced genomics and biotechnology [62, 63]. Even drastic variations in the fatty acid pattern of seeds are tolerated by plants and seedlings. Systematic screening programmes for oil-producing crops from diverse plant species have been undertaken [64–67]. Classical plant breeding, combined with experimental mutagenesis (‘mutation breeding’) and modern in vitro cell- and tissue culture methods, has frequently proved to be successful in commercially exploited oil plants, such as soybean, rapeseed, sunflower, peanut or linseed, which now exhibit a considerable variation in their fatty acid pattern (see Tables 5.11–5.14). By using these techniques to produce variant strains of rapeseed, the erucic acid (C22 : 1) component in the fatty acids can be varied from 0% to over 50%, whilst the lauric acid (C12 : 0)

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Biodiesel science and technology

component can be varied from 0% to some 37%. With sunflower seeds the oleic acid (C18:1) content has been increased to over 92%, providing a highly valuable source of this material. Transferring a novel oil quality into a high yielding, agronomically adapted plant species by conventional methods is possible, though fraught with difficulty. Classic breeding programmes are lengthy processes, requiring at least 10–15 years. Gene technology is well suited to accelerate breeding progress. This grants the ability to implant a specific and desired quality property from distantly related plant species. Sustainable agriculture could benefit from gene mapping. Besides guiding selection of genes with high yield, the gene map could also be used to select genes that are necessary for trees to thrive in a changing climate. In addition to mutation breeding efforts on traditional crops, work is being carried out to domesticate alternative oil-rich plants that may yield new potentially useful fatty acids. The availability of modern biotechnological approaches has sped up the development of new oil types [68]. Using GM techniques to alter the activity of a plant enzyme can convert unsaturated oils in the seeds of a plant from a temperate zone to the more saturated type generally found in tropical plants like oil-producing palm. A special GM coconut variety with much less lauric acid is under development in the Philippines. Monsanto’s Vistive III soybeans are designed to have a similar oil profile to olive oil and are low in linolenic acid. Studies are also being conducted to genetically modify soybeans to produce oil resembling tung oil in composition. Careful breeding and genetic improvement of plants can help in meeting growing demand worldwide, especially in the energy sector. All possible needs cannot be met using a single plant. Hence, a careful selection of species with maximum potential for desirable oil producing qualities needs to be made which can be genetically improved for desired compounds using modern techniques. Genomic manipulation of saturated and unsaturated fatty acid composition has utility in enhanced ignition and flow properties of biofuels [58, 61]. Similarly, improved digestibility and metabolisable energy values for meal co-products sustain the economy of biodiesel. Implementation of the products of genetically enhanced oilseeds on an economic scale is necessary to secure the level of agricultural capacity desired in the future. Plant tissue culture has been used to produce elite varieties of oil palm and coconut. A recently developed new clonal oil palm increases oil yield by 20%. Increases in oil concentration from 40% to 60% of kernel weight of peanut have been achieved, thus resulting in a 50% increase in oil production per hectare. Pioneer intends introducing high-oil corn by 2013. Advanced plant breeding may result in other high-oil varieties (e.g. coriander, 23%). Also plant breeding efforts to domesticate wild plants, such as species of the genera Cuphea, Calendula, Euphorbia, Vernonia, Lesquerella, Crambe or

Oleochemical sources

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Limnanthes, have been reported in order to develop useful plants that may be more productive (see Section 6.4.6). Breeding programmes have focused on improving agronomic traits necessary for Cuphea domestication and commercial production [69, 70]. Knapp [71] has reported mutagenic work to extend the range of phenotypes in several Cuphea species. This resulted in the production of the mutant C. viscosissima VS-320 with an oil that has increased medium-chain triglyceride (SCT) content, as follows: C6 : 0, 4.19%; C8 : 0, 40.24%; C10 : 0, 36.90%; C12 :0, 4.81%; C14 : 0, 6.84%; C16 : 0, 3.33%; C18:0, 0.15%; C18 : 1, 1.37%; C18 : 2, 2.05%; C18 : 3, 0.13%. Oil of the mutant plant C. viscosissima VS-320 contains the highest reported levels of the SCTs tricaprin (C10 : 0) and tricaprylin (C8 : 0) in plant oils. In addition, this oil produces the triglyceride tricaproin (C6 : 0), which is normally not present in other plant-derived oils. The unique triglyceride composition makes this oil a natural, inexpensive source of SCTs for industrial application. The physical properties of C. viscosissima VS-320 oil were studied by Geller et al. [72]. Viscosity is an important factor in predicting the performance of potential alternative diesel fuel sources. Fuel performance of the oil produced by this Cuphea mutant shows a marked improvement compared to that of traditional vegetable oils, approaching that of methyl esters. The viscosity of the mutant Cuphea oil falls between that of diesel fuel and rapeseed oil. It may be possible to tailor Cuphae crops to produce selected fatty acids on demand under a variety of growing conditions [73]. Synthase genes can be used to alter fatty acid composition in such crop plants. Further genetic development of the plant genus Cuphea as a source of diesel fuel is warranted. Other developments are non-toxic GM cottonseed (containing 0.19 mg gossypol/kg seed) [74]. However, bringing such new products to market nowadays requires 8–10 years and US$100 Million investment. Transgenic oils were recently reviewed [75]. No transgenic oil fruits (olive, palm, avocado) are under exploitation at present on a large scale. Introduction of transgenic oil palm varieties with new traits such as lower content of palmitic acid or a low level of endogenous lipase is of interest. Consumer resistance may delay such developments. Ongoing efforts to obtain unconventional modified seed oils containing ‘pure’ triglycerides (e.g. trilaurin) in commercial crops all aim at obtaining important tailor-made feedstocks for the chemical industry. The increase in variability demands fast, cost-effective, and easy-to-handle methods to discriminate between different oil types. Near-infrared reflectance spectroscopy (NIRS) finds application as a non-destructive method in prescreening of seed quality traits (seed oil, crude protein and water content, fatty acid composition) in plant breeding projects [76–80]. The potential of quantitative and qualitative analysis based on NIRS spectra to discriminate between oils from different vegetable sources (canola, soybean, peanut, cottonseed) [81, 82] or from the same vegetable source (sunflower types with

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Biodiesel science and technology

high palmitic, stearic or oleic acid contents; see Table 5.13) [83] has been demonstrated. NIRS was also applied to determine the seed oil content and FA composition in sunflower through the analysis of intact seeds, husked seeds, meal and oil [79]. Similarly, the FA profile of whole soybeans was determined [84]. NIR calibration equations were developed for the major fatty acids (16 : 0, 18 : 0, 18 : 1, 18 : 2, 18 : 3, 20 : 1, 22 : 1) in intact-seed Ethiopian mustard (B. carinata L.) [85]. NIRS has also been used for non-destructive determination of linoleic and erucic acid contents in intact seed kernels and in a single seed of rape (B. napus L.) [86]. The fatty acid composition in canola, flax and solin (low-linolenic flax) for oleic, linoleic and linolenic acids, saturated fatty acids and iodine value were successfully determined by the same spectroscopic technique [87]. NIRS has also been used for palmitic, stearic, oleic and linoleic acid profiling of sesame seeds for breeding selection [88]. Similarly, the free fatty acid content in palm oil may rapidly be assessed by NIRS [89]. Breeding programmes of V. galamensis were sustained by NIRS analysis of seed weight, FA composition, oil and protein contents of intact seeds [90]. Also the non-destructive single-seed oil content determination of meadowfoam by near-infrared transmission spectroscopy (NITS) has been reported [91]. Meanwhile, patent protection of plants has led to considerable concern as to biodiversity conservation, violation of the basic principles of agriculture, undesired seed and food monopolies, biopiracy practices, and the future of farmers [92]. Sustainable farming is fundamentally not in favour of GMO crops. The mission of Sustainable Biodiesel Alliance, formed in December 2006 in the US, is to create a vision for the sustainable production of biodiesel and the means to certify sustainable biodiesel producers (see also Chapter 14). A basic principle of the Alliance is that GMO feedstocks should not be used unless proven safe.

3.4

Industrial use of vegetable oils

Oils and waxes are commonly found in many plant species. Oils are abundant in seeds, while waxes are normally abundant on the surface of leaves or stems. Oil yielding crop plants are very important for the economic growth of the agricultural sector. Oil volumes and values change widely. In the past, the world’s fat and oil outputs have been more than enough to satisfy the needs of human and animal nutrition (86% food/feed). Consequently, the oleochemical industry was assured of a reliable supply of raw materials (14% of oils and fats) for chemicals manufacture [93]. Fatty acids are used to make soaps, lubricants and greases, and chemical intermediates such as esters, ethoxylates and amides. These three important classes of intermediates are used in the manufacture of surfactants, emulsifiers, detergents, alkyd resins, polyamides, additives (plasticisers, stabilisers), high-performance

Oleochemical sources

81

coatings, paints and varnishes, dispersants, corrosion inhibitors, adhesives, paper, cosmetics, pharmaceuticals, water repellents and fuels. Surfactants are the most important oleochemical outlet for fatty acids. In Europe alone, 200 kt of vegetable oil methyl ester are produced annually as raw materials especially for surfactants. In the last eight years, food consumption has exceeded production, leading to historically low reserves. Higher demand for human nutrition from developing countries (China, India) and the development of biodiesel have determined a change in global use of vegetable oils in 2007, namely 84% foodstuffs, 10% oleochemical and 6% biodiesel (of which 4.6 Mt RSO, 2.1 Mt SBO and < 2.0 Mt PMO and other vegetable oils). Although there is a large genetic variation for the different quality traits of vegetable oil plants both in the seed and leaf, and while natural lipid biosynthesis leads to a broad variety of oils in seeds and fruits, a restricted subset of fatty acid compositions predominates. This has largely determined the value and use of oils and fats in food and oleochemical applications [34, 93]; see Table 3.4. On the other hand, biodiesel application sets different requirements to the oily feedstocks, both in terms of composition and of extraction/refining techniques. While for some chemical applications of triacylglycerides the intact TAG structure (fatty acid positional distribution; see Section 3.2.2) is crucial, for biodiesel application only the fatty acid profile (resulting from hydrolysis of TAGs) matters. Use of plant triacylglycerols as feedstocks for the production of biofuels has recently been reviewed [54]. Table 3.4 Fatty acid specificity and applications Fatty acid composition Industrial crop source Applicability Medium-chain fatty acids (C6 – C14)a

Coconut, palm kernel, Industrial (plasticisers, detergents, cuphea, babassu lubricants), medicinal, nutritional

Lauric acid (C12) Coconut, palm kernel, Detergents, soaps, defoaming (cuphea, babassu) agents, cosmetics, lubricants, food emulsifiers Epoxy fatty acids (C18) Euphorbia, Acacia arabicab

Plasticisers, additives, drying solvents, crosslinkers

Polyunsaturated fatty Linseed, tung acids (C18:3)

Drying oils (coatings, organic binders), varnishes

Hydroxy fatty acids Castor, Lesquerella (C18-OH, C20-OH)

Cosmetics, lubricity enhancers, heavy-duty detergents, inks, coatings

Long-chain fatty acids (C20 – C22)

Cosmetics, specialty lubricants, polymers

a

Meadowfoam, high-erucic rapeseed

Caproic, caprylic, capric, lauric, myristic.     Other sources of EFAs include epoxidised soybean oil, linseed oil (from oilseed flax) and processed petrochemicals. b

82

Biodiesel science and technology

Dyer et al. [34] have recently given an overview of several areas (food/feed, fuel/energy, industrial feedstocks, lubricants, inks, nutraceuticals) where plant oils can have a significant impact on the emerging bioeconomy. Many oilseeds find wide application for their nutritional and pharmaceutical values; various polyunsaturated fatty acids (PUFAs) show high nutritional properties and are essential to human health. Trans fatty acids are gradually being banned for cooking purposes [94]. Cosmetics oils, such as kukui nut (Aleurites moluccana), borage (Borago officinalis), blackcurrant (Ribes nigrum) and evening primrose (Œnothera biennis) oils are all highly polyunsaturated (50–80%) and therefore less suitable directly as biodiesel feedstocks, despite claims to that extent [95]. Many of the vegetable oils produced in agricultural systems are necessary for a variety of other oleochemical industrial uses, and more recently also for biodiesel. Various early methods of transformation of vegetable oils to yield fuels of varying nature have included tung oil [96], fish oils [97, 98], linseed oil [99], castor oil [100], palm oil [101], cottonseed oil [102] and olive oil [103]. Fatty acid composition determines the quality of oils and fats. Nature has generated an enormous variety of fatty acids, differing in chain length, number and position of double bonds and functional groups. While saturated fatty acids are less desired for nutritional applications, in the industrial sector (cosmetics, softeners, lubricants, and others) such fatty acids are valuable raw materials. For industrial non-food applications such as oleochemicals, high amounts of a single fatty acid content in vegetable oils is of considerable value because processing costs for homogeneous or nearly homogeneous starting material would be reduced. Coconut, palm kernel and Cuphea oils are natural sources of medium-chain fatty acids (C8-C14). Certain natural medium-chain fatty acid producers accumulate just one triglyceride. For example, Actinodaphne hookeri (tali; Lauraceae) seeds contain 95% trilaurin; nutmeg oil contains more than 80% tri-14:0. Some of the Brassicaceae, e.g. Crambe abyssinica, Brassica napus L. and a specially bred high-erucic rapeseed (HEAR) are rich sources (40–60%) of erucic acid (C22 : 1Δ13). Almost 40 kha of land is used to grow rapeseed for erucic acid production in Europe. The high level of erucic acid makes HEAR unsuitable for human consumption. Breeders have bred out erucic acid and lowered levels of glucosinolates (canola). The oleic/linoleic acid group comprises crops such as sunflower (> 85% C18 : 1 + C18 : 2), sesame (> 85%), corn (> 80%), safflower (> 90%), rice bran (>75%), sorghum (> 85%), high-oleic soybean (> 85%) and rapeseed oils (> 80%). Safflower is the highest commercial source of linoleic acid. Cottonseed typically contains about 15 wt% oleic acid; increased seed oleic acid content in transgenic cotton plants ranges from 21 to 30 wt% [104]. The increase in oleic acid content is at the expense of linoleic acid. Drying oils (Table 3.5) have the property of forming a solid, elastic substance when exposed to air in thin layers. The drying power is proportional to the

Oleochemical sources

83

Table 3.5 Classification of oils on the basis of the degree of saturation Saturated: non-drying oils (IV 100–80 g I2/hg)         Palm, peanut, olive, rape, castor, almond, jamba Moderately unsaturated: semi-drying oils (IV 120–100 g I2/hg) Cottonseed, sunflower, sesame, croton, corn, curcas, kapok Highly unsaturated: drying oils (IV 200–120 g I2/hg)   Linseed, tung, soybean, hempseed, walnut, candlenut, poppy, safflower, perilla

amount of unsaturated fatty acids present. Although the drying process for all drying oils is essentially the same, there are important differences in the oxidation rate. The IV of these oils ranges from about 200 to 120 g I2/hg, which is beyond the range of interest for biodiesel application (unless blending). Vegetable semi-drying oils (IV 120–100 g I2/hg) are characterised by forming a skin when exposed to air at somewhat elevated temperatures. Non-drying oils (Table 3.5), with IV ranges from 100–80 g I2/hg, thicken at elevated temperature but do not dry to a skin. The linolenic acid group has semi-drying properties and is widely used industrially in paints and varnishes. As all tend to oxidise readily, they are regarded as low-quality oils. Lallemantia iberica contains 68.0% of linolenic acid (C18:3), representing one of the highest contents of this unsaturated fatty acid in plant species known. Conventional cold-pressed flaxseed (linseed) oil is an excellent source of linolenic acid, containing approximately 50 wt% C18:3 [105–107]. Also the high linolenic acid contents in C. sativa (false flax, up to 39%) [108] is of interest. Also canola (7% C18 : 3), Lupinus albus (white lupin, 8.7%), perilla (59.6%), hempseed (22.4%) and wheat germ (6.2%) have significant quantities of linolenic acid, in addition to oleic and linoleic acid. Soybean oil from current commercial cultivars typically contains roughly 8% linolenic acid but breeding programmes have allowed the development of germplasm with lower than normal levels of C18 : 3, namely 3.3% [109, 110]. Little is known of the genetic mechanisms that govern C18 : 3 in wild soybean. The linolenic level is most vulnerable to environmental effects in soybean seed oil [111]. It has also been possible to select extremely low-linolenic acid mutants in linseed [107, 112]; see Tables 5.11 and 5.14. Various families are rich sources for g-linolenic acid (GLA: Z,Z,Z-6,9,12-octadecatrienoic acid, 18:3n-6): Onagracea, Saxiferagacea and Boraginacea. Three species gave birth to industrial developments: onagre (Œ. biennis), blackcurrant pip (R. nigrum) and borage (B. officinalis) with g-linolenic acid contents of 8–11%, 14–19% and 18–26%, respectively [113]. The Mediterranean borage crop contains 30–33% of an oil that is the most concentrated source of GLA. In oils containing conjugated fatty acids, such as tung oil (containing 80% of cis, trans, trans-9,11,13-octadecatrienoic acid or C18 : 3c, where ‘c’ stands for conjugation) and oiticica oil (containing 78% of licanic acid or 4-keto-9,11,13-octadecatrienoic acid), the position of double bonds favours

84

Biodiesel science and technology

oxidation and polymerisation. Tung oil is contained in the kernel of fruits (nuts) of the tung tree (Aleuritis fordii, A. cordata, A. verrucosa or A. montana). Major producers include China, Paraguay, Argentina and Brazil; estimated world production averages 50 kt/yr. Kekuna and candlenut or lumbang (A. moluccana) oils, which have similar compositions to Chinese tung oil (A. fordii), are from A. trisperma and A. triloba, respectively. The expensive non-edible tung oil contains about 90% PUFA, mainly as a-eleostearic acid with smaller amounts of oleic, linoleic and palmitic fatty acids [114]. Consequently, tung oil classifies as a conjugated polyunsaturated drying oil whereas linseed oil is of the non-conjugated type. Tung oil’s physical and chemical properties make it useful as a protective coating, solvent, and/or drying agent in various paints, varnishes, lacquers and resins. Its superior drying properties, faster than those of the linolenic acid group, allow it to be sold at a price premium (US$25–50/gal) compared to other vegetable drying oils such as linseed oil. Synthetic diesel from tung oil was once produced in China [96]. Castor oil (world production volume about 600 kt/yr, mainly originating from India and China), which is an inedible, inexpensive, non-volatile oil with good shelf-life, is rich in ricinoleic, or 12-hydroxy-9-cis-octadecenoic acid (85–95%), which is the only hydroxyl acid oil of commercial value. Enzymatic hydrolysis of castor oil with lipolase yields ricinoleic acid [115]. Castor oil (CAS) has too high a viscosity for use in diesel engines (see Table 4.1). CAS is classified as a non-drying oil with very low PUFA value (4.8%). Dehydration of castor oil leads to formation of the conjugated 9,11-octadecadienoic acid; dehydrated castor oil (DCAS) is a semi-drying or drying oil, which can replace tung oil. Castor oil cultivation for biodiesel production is being considered by various countries (see Section 5.9). Unlike vegetable oils and animal fats, oil from the specialty crop jojoba (Simmondsia chinensis) is not just a triglyceride but rather a mixture of long-chain fatty acid esters and fatty alcohols, and is more properly referred to as a wax (average molecular weight of C38-C42 wax esters of 606–610 Da). Many factors affect wax ester, fatty acid and fatty alcohol molecular weight [116]. The liquid wax esters extracted are used commercially in the lubricant and cosmetics industries. Jojoba seed production is quite limited (5 kt/yr) [117]. Krill oil, which contains phospholipids, omega-3 (>30% EPA and DHA), omega-6 (<2.0% C18 : 2) and omega-9 fatty acids (>10% C18 : 1) as well as astaxanthin, finds use in the nutraceutical and pharmaceutical industries. Krills (or euphausiids) are at the bottom of the animal food chain and are mainly used for aquaculture and aquarium feeds, but are also sold for human consumption, mainly in Japan. With the current regulatory catch quota of about 6 Mt/yr and a lipid content of only 3 wt%, the potential oil yield is 180 kt if all krill were dried and the oil extracted.

Oleochemical sources

3.5

85

Unusual fatty acids

Triglycerides are commonly classified as short-chain (SCT, C2-C5), mediumchain (MCT, C6-C14) and long-chain (LCT, > C16). Both SCT and MCT are mostly saturated and are found in dairy products as well as in some plant oils. Long-chain triglycerides may have points of unsaturation and are found in animal, food and fish products as well as in plant oils. Most liquid plant oils (soybean, canola, safflower, sunflower, etc.) are composed of predominantly 18-carbon fatty acids. Longer chain fatty acids, such as those found in camelina, mustard and meadowfoam, give these oils unique hydrating and stability properties. In plant oils generally only even-numbered chain lengths occur (see Section 3.2.1), whereas animal fats also contain unevenly-numbered fatty acids. Odd chain length long-chain fatty acids are frequently found in marine oils. Fish oils contain unusual odd-numbered triglycerides (0.1–0.5% of 17 : 0, 17 : 1, 19 : 0, 19 : 1, 21 : 0, 21 : 5) and/or branched-chain triacylglycerols (0.1–0.8% of C15, C17, C18, C19). These minor fatty acids are relatively insignificant in determining the characteristics of each fish oil. The structures of fatty acids esterified in triacylglycerols are remarkably diverse in the plant kingdom [30]. As shown in Section 3.2, lipid content can be affected by genotype within the same species and also by environment. As shown in Figs 3.2 and 3.6 for plants, oleic acid may be transferred into the PC fraction of the ER for conversion to linoleic acid by a membrane-bound oleate D12-desaturase. Many plants contain a divergent form of D12-DES capable of producing a variety of unusual fatty acids, such as hydroxy, epoxy, acetylenic or conjugated fatty acids. The transfer of unusual fatty acids from PC to TAG is significantly more complex than for the common fatty acids; details of the relevant enzyme activities are still largely unknown. The commercial production of seed oils containing unusual fatty acids is frequently hampered by the poor agronomic traits of the plants (e.g. small seeds, limited geographical growing areas), which significantly increase production costs [118]. The mix and concentration of the triacylglycerides present in many oils also raise other economic issues, since the desired component is often only present in relatively small amounts. Exotic fatty acids of commercial interest in oilseeds to be used for chemical or nutritional purposes were recently listed by Drexler et al. [28] and Dyer et al. [34]. For example, very few plants synthesise the triglycerides, tricaprylin (C8:0) and tricaprin (C10 : 0). MCTs may be derived from specific fractions of unhydrogenated, partially hydrogenated or fully hydrogenated dairy butterfat, coconut oil, palm kernel oil and the like. Plant sources of tricaproin are limited only to trace components in some tropical plants and are incapable of supplying sufficient volumes for industrial application. The diversity of structure and inherent functionality of vegetable oils make them prime candidates for use in polymers and resins. Chemistry

86

Biodiesel science and technology 18 : 1-CoA

18 : 1-PC

OH-18 : 1-PC

D12-DES

18 : 2-PC

Epoxy-18 : 1-PC Acetylenic-18 : 1-PC Conjugated-18 : 3-PC

D15-DES

18 : 3-PC

Triacylglycerols (oil)

3.6 Production of unusual fatty acids and oils in plants.

being considered to modify and functionalise vegetable oils includes transesterification, epoxidation, hydroformylation and metathesis. Unusual fatty acids are of particular interest for various industrial applications. Consequently, considerable efforts have been undertaken to alter the genome of traditional oilseed crops in such a way that they accumulate new economically valuable oils [119]. A genetically altered plant strain (Cuphea viscosissima VS-320) produces an oil with elevated levels (> 80%) of MCTs, in particular C10 : 0 and C8 : 0, and some C6 : 0 [72]. Such an oil may be appropriate for use as a natural substitute for diesel fuel without chemical conversion of component triglycerides to methyl esters (see Section 3.3). Modern DNA transfer technologies might afford the transfer of genes that control the synthesis of low molecular weight triglycerides from species such as Cuphea into other better established oilseed crops. Oil composition could then be genetically modified for the optimal desired biodiesel properties. The manipulation of oil synthesis in canola plants to produce specific, desired,

Oleochemical sources

87

chemically altered triglycerides has already been implemented on a large scale. For example, canola oil synthesis was altered to produce high levels of the medium-chain triglyceride C12 : 0 resulting in reduced levels of the long-chain triglycerides C16 : 0 and C18 : 0 [36]. Seed oils containing fatty acids with unusual structures are highly important in the chemical industry as raw materials for the production of a variety of oleochemicals (see Tables 3.4 and 3.5). The chemical structure of fatty acids in plant lipids is usually bound to a chain of 18 carbon atoms with double bonds occurring at D9, 12 and/or 15 positions. However, some plant species are able to produce unusual fatty acids with special characteristics, such as variations in chain length (mainly C12 and C14), conjugated double bonds or functional groups within the fatty acid molecule. An abundance of unusual fatty acids with various functionalities in the fatty acid chain can be found in plants from nature, like acetylenic, allenic, conjugated, epoxide, keto, hydroxy, furanoid, fluoro, cyclopropene and cyclopentenyl fatty acids [120]. In fact, over 300 different unusual fatty acids have been identified in seed oils from various plants [29, 30, 121–123]. Some of these unusual fatty acids can occur in very high amounts (up to 95%) in the seed oil of certain species. Of these plants only relatively few, e.g. castor bean, are used for significant commercial production. However, many other unusual fatty acids have considerable potential as renewable industrial feedstocks. Biochemical pathways involved in the synthesis of unusual monounsaturated fatty acids, such as petroselinic acid (C18 : 1), are complex [124]. The synthesis of these fatty acids likely involves enzyme complexes. Oxygenated fatty acids are mainly mono- and dihydroxy fatty acids, keto and epoxy fatty acids. Hydroxyl functionality is rare in plant oils. Castor (Ricinus communis) oil contains 88–90% of the main monohydroxy fatty acid, ricinoleic acid (C18 : 1-OH), and trace quantities of dihydroxystearic acid (~0.7%), which has two hydroxyl groups. Hydroxy fatty acids (HFAs) find application in the manufacture of polymers, paints, flavour and fragrance components. Ricinoleic acid is a much sought-after hydroxy fatty acid and is also found in Crotalaria striata (15.8%), Ochrocarpus africanus (20.0%) and Alternanthera triandra (22.1%). The uniquely high level of the ricinoleic acid in castor oil imparts increased lubricity to the oil esters as compared to normal vegetable oil esters with similar carbon chain length [125]. Similarly, the developing crop plant Lesquerella also produces HFAs. Lesquerella fendleri and L. gordonii are members of the genus Lesquerella of the Brassicaceae (mustard) family. The oils of L. fendleri and L. gordonii are attractive due to their high HFA content (see Table 6.7). The major hydroxy fatty acid (53%) is 14-hydroxy-cis-11-eicosenoic acid (lesquerolic acid), a homologue to ricinoleic acid. Lesquerella also contains densipolic acid (C18 : 2-OH), auricolic acid (C20 : 2-OH) and traces of ricinoleic acid (C18 : 1-OH). The hydroxyl group facilitates plasticisation and adhesion of

88

Biodiesel science and technology

the oil esters. The fatty acid profile imparts Lesquerella oil methyl esters with exceptional value as diesel fuel additives [126]. The seed oils from Dimorphoteca pluvialis (Cape marigold) contain the HFA dimorphecolic acid (C18 : 2-OH) [127]. The kernel oil Licania rigida (Oiticica) has obtained commercial status as it contains high amounts of the ketonic polyene-acid 4-ketoeleostearic (or licanic) acid, C18:3=O (drying agent) [128, 129]. Similarly, Mappia foetida contains 16.0% of 3-keto-octadec-cis-15-enoic acid [130]. Natural sources of epoxy oil (vernolic acid, C18:1>O) are Vernonia galamensis (> 74%), V. anthelmintica (67%) and Euphorbia lagascae (60%). The seeds from Acacia arabica (Leguminosae) varieties – Telia babul, Vediana and Cupressiformis – contain about 9% of the related epoxy derivative coronaric acid (9,10-epoxy-octadec-cis-12-enoic acid; C18 : 1>O), as well as the cyclopropene fatty acids malvalic acid (about 2.5%) and sterculic acid (about 2.1%) [131]. Similarly, Ficus benghalensis (banyan tree) oil contains normal fatty acids, along with an epoxy fatty acid (vernolic acid) and two cyclopropenoid fatty acids (malvalic and sterculic acid). Currently, no oilseed crop has been commercialised as a source of natural epoxidised oils. However, V. galamensis has potential for domestication as a new industrial oilseed source of natural epoxy fatty acids. Epoxidised oils, manufactured by chemical epoxidation of fats and vegetable oils such as soybean, are useful in reformulation of oil-based (alkyl-resin) paints, as plasticisers, and in cosmetic and pharmaceutical applications. The naturally occurring epoxidised oil of Vernonia and the chemically epoxidised soybean oil (ESO) and linseed oil are similar, but there is an important difference. Epoxidised soybean and linseed oil are highly viscous and are non-pourable below 273 K. Vernonia oil, however, has low viscosity and can be stored below 273 K. Whereas methyl vernoleate (containing an epoxy group) is very stable towards oxidation, methyl crepenynate (containing a triple bond) oxidises extremely rapidly [132]. Small amounts of furanoid fatty acids (C20 and C22) are contained in soybean oil [133]. Cyclopropenoid fatty acids occur most commonly in the seed oils of the order Malvales (Sterculiaceae, Malvaceae, Bombaceae and Tiliaceae). As shown in Table 3.6, the cyclopropenoid fatty acids malvalic acid (C18 : 1) and sterculic acid (C19 : 1) frequently occur together, as in the cases of F. benghalensis, A. arabica, C. striata, Triumfetta pilosa (Roth seed), Cassia marginata and O. africanus. Small amounts of cyclopropene fatty acids (malvalic and sterculic acids) are also present in crude cottonseed oil, and exert harmful biological effects when fed to animals [134]. The seed oils of many species of plants of the Flacourtiaceae family contain fatty acids with a terminal cyclopentenyl group. The cyclopentenyl fatty acids hydnocarpic acid (C16 : 1), chaulmoogric acid (C18 : 1) and gorlic acid (C18 : 2) constitute up to 90% of the total fatty acids of the seed oils of Hydnocarpus, a medicinal oil [135]. Momordica balsamina L. (balsam

Table 3.6 Composition of a selection of seed oils containing unusual fatty acids  

Oil SN content

a

200

CN C12:0 C14:0 C16:0 C18:0 C18:1 C18:1a C18:1>Ob C18:1>Oc C18:1–OH C18:1=Od C18:2 C18:3 C19:1e References

78 54 1.5

1.3

35.2

4.2

20.3

3.7

8.2

–

–

–

15.4

8.7

1.6

[136]

201 116 48 – 203 92 51 –

1.3 3.6

12.7 32.1

6.0 4.1

20.7 8.0

2.5 2.1

– –

9.0 –

– 15.8

– –

45.7 – 15.0 15.0

2.1 4.3

[131] [137]

200 85 55 – 200 102 50 –

– –

24.2 16.7

8.9 10.8

17.1 20.1

– 2.4

22.0 –

– –

– –

– –

27.8 43.4

– –

– 6.6

[138] [139]

201 110 47 –

–

17.3

4.5

14.2

3.5

8.5

–

–

–

49.4

–

2.6

[140]

200

1.3

28.2

27.4

–

6.0

12.0

–

20.0

–

–

–

4.0

[141]

203 102 54 –

3.9

16.9

5.9

26.0

–

–

–

22.1

–

25.2

–

–

[142]

201 196

99 38 – 35 66 –

– –

12.3 56.0

4.2 3.6

16.2 5.3

– 0.5

– –

– –

– –

16.0 –

11.6 39.7 5.6 –

188

61 62 –

–

27.0

3.7

5.6

6.7

–

–

–

–

35 65 1.1

6.3

–

Malvalic acid.                         Vernolic acid. c Coronaric acid. d 3-Keto-octadec-cis-15-enoic acid. e Sterculic acid. b

– 22.9

[130] [143, 144]

45.0

[143]

Oleochemical sources

Ficus 20 benghalensis Acacia arabica 7–9 Crotalaria   5 striata Rivea ornata 10 Triumfetta 12 pilosa Cassia   5 marginata Ochrocarpus 30 africanus Alternanthera   8 triandra Mappia foetida 35 Bombax – munguba Sterculia – foetida

IV

89

90

Biodiesel science and technology

apple) seed oil contains geometrical isomers of conjugated octadecatrienoic acids, namely punicic acid (50%) and a-eleostearic acid (13%) [145]. In the industrial field, there is competition between oleochemicals and petrochemicals (fuels). Being combustible, vegetable oils have great potential to be used as liquid fuel and some will combust in diesel engines. Requirements to the fatty acid profile of a vegetable oil, which makes it a good starting material for biodiesel production (at least from a chemical point of view), are complex but many different compositions qualify. The compositions of the seed oils with unusual fatty acids shown in Table 3.6 are mainly of interest for oleochemical production. For biodiesel applications the oil contents of most seeds are too low. Taking into account the linolenic acid content (< 12% for biodiesel applications), F. benghalensis and O. africanus deserve some further attention in this respect.

3.6

Oil processing techniques

The widely differing characteristics of fatty materials from diverse sources have given rise to various oil recovery processes, such as rendering (see Section 5.10.1), pressing and solvent extraction. The term ‘rendering’ is generally applied to treatment designed to remove all or most of the fatty animal tissue or other materials with a high ratio of fat to solid matter. Natural vegetable oils and animal fats are pressed or extracted to obtain crude oil or fat, and crude oils may be refined (see Section 3.6.5). The method used to extract vegetable oil depends on the type of raw material available. Raw materials may be grouped according to the part of the plant that contains oil or fat (seed, bean, nut or fruit). The main difference in raw materials is the moisture content. Raw materials with low moisture content include seeds and beans and some nuts, which are dried on harvest. Palm fruit, olive fruits and some coconuts are processed wet. Most oil (75%) comes from seeds. The use of fruits as an oil source (e.g. palm, olive, avocado) presents several advantages compared with seeds. Oil from fruits is easily extractable and can often be obtained by a few simple mechanical steps, which contrasts with seeds that often have to be submitted to several transformation steps before extraction of the oil with organic solvents. Moreover, oil fruits typically have an overall higher yield of oil per unit of growth area than oil seeds. The production of vegetable oils from oleaginous seeds employs technology which has been developed over many decades of commercial use. Seed crushing needs to consider the oil recovery rate and oil losses. Most commercial processing of common oilseeds is by mechanical expression (cold or hot), solvent extraction or mixed mechanical/solvent extraction [146]. The general principles of processing methods and preservation include:

Oleochemical sources

91

sterilisation by application of heat; elimination of as much water as possible from the oil to prevent microbial growth during storage; and proper packaging and storage of the extracted oil to slow down chemical deterioration (oxidation, rancidity). The objectives of sterilisation (‘cooking’) are loosening of fruit on the bunch, softening of fruit, conditioning of nuts, coagulation of proteins, and destruction of enzymes in the raw material and contaminating microorganisms that produce free fatty acids on processing. Vegetable oil processing from oilseeds or oil fruits may comprise various stages, including cleaning, dehulling, pre-treatment (cooking at 353–363 K; conditioning at 7–10% relative humidity; enzymatic hydrolysis; drying; flaking), cracking/grinding, extraction (mechanically, chemically or in combination), purification and refining. Obviously, any pre-treatment step of oleaginous seeds adds to the overall cost. There are, however, essentially three major steps in extraction of oil from seed: heating, crushing and further processing. First, the seeds may be heated or left cold before pressing through a mechanical crusher, i.e. hot pressed or cold pressed. Heat treatment applied to oilseeds prior to pressing is not generally necessary. Second, the seeds pass through some type of press which presses oil into a container and directs seed meal into another. Third, and optionally, a mechanical or chemical process may be used to increase oil yield. In a mechanical process, the remaining meal is prepared for recrushing by passing it through an extruder which heats the meal to the point that seed cell walls break, facilitating further oil removal. The preferred extraction depends on the nature of the oilseed/fruit, oil content and production capacity (Table 3.7). Only seeds, nuts and fruits that contain considerable amounts of edible oil are used for small-scale oil extraction. Edible oil content may also be too small for economic processing

Table 3.7 Extraction procedures of vegetable oils Process

Applicability

  Raw materials

Mechanical High oil content (> 35%) Small/medium capacitya (< 200 t/d)

Babassu Castor bean Peanut

Solvent Low oil content (< 25%) High capacitya (> 300 t/d)    

Soybean Rice bran Cottonseed

Mixed Medium/high oil content (> 25%) Medium/high capacitya (> 200 t/d)    

Coconut Castor bean Peanut Babassu Sunflower

a

Raw material.

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Biodiesel science and technology

on a small scale (e.g. maize). Palm fruit containing about 56% edible oil (or 25% on a fresh fruit bunch (FFB) basis) with no known toxins is suitable for small-scale processing. Oils containing toxins or having unpleasant flavours require careful processing and are generally not suitable for small-scale processing (e.g. castor oil). The oil content of vegetable oil seeds varies considerably, from very low (soybean ca. 20%) to high (euphorbs, ca. 50%) (see Table 3.8). Consequently, 1000 kg of canola seed yields about 420 kg of biodiesel from the oil fraction, as opposed to only 200 kg from 1000 kg of soybeans. With biodiesel application in mind, we notice the exceedingly low seed oil content (7–9%) of Acacia arabica, and therefore other use (in particular medicinal) is recommended here. The preferred extraction method also depends on the desired results. The choice of extraction method may have implications for uses and prices for both oil and meal. If one wishes to preserve the cake, then the oil press is Table 3.8 Oil content (wt%) of oil fruits and oil seeds Acacia arabica B. carinata Babassua Camelina Canola Cardoon Castor bean Coconut (copra) Coriander Corna Cottonseed Crambe Crotona Euphorbia Hazelnut Hempseed Jatropha c. Joyoba oil-wax Kapok seed Kenaf Lesquerella Linseed Lupin a

7–9 39–50 42–63 30–43 38–43 25 46–55 50–65 9–19 7–8 15–25 35b–46c 50–60 48–52 49–63 25–35 46–58a 25–40b 50–60 20 21–26 25 35–45 12–22

 

Mahua Meadowfoam Moringa oleifera Mustard Olive Oiticicaa Palm (E. guineensis) Palm (E. oleifera) Peanut Pennycress Perilla Pongamia pinnata Poppyseed Rapeseed Rice bran Rubber seeda Safflower Sesame Soybean Sunflower Tung Vernonia Wheat germ

  50 20–26 25–41 25–50d 20 60 40–65e, f 29–50e 35–54 36 38–48 24–33 40–50 36–50 16–32g 40–50 28–45 37–63 15–23 22–55 35 30–42 8–12

Kernels. Whole seed. c Dehulled seed. d Yellow mustard (27%), brown mustard (36%), some oriental mustards (50%). e Mesocarp. f 21–25% on FFB basis. g Depending on variety of rice and degree of milling. b

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used. The hexane crusher process extracts more than 90% of the oil from the seed, leaving very little in the meal. The cold-press extraction method, an ‘organic’ expeller process, leaves 8–13% of oil in the meal. The meal’s higher oil content, and in some cases its omega-3 fatty acid content, and the ‘organic’ process might generate a price premium, or the higher oil content might lead to a discount, because the oil is not good for ruminants. Vegetable oils should ideally be kept in dark containers in cool and dry locations, minimising contact with air and moisture. In colder climates, used vegetable oil can be stored indefinitely; in warm climates, microorganisms can grow rapidly in used vegetable oils. Quality control in the oil mill concentrates on optimising oil yield and minimising deterioration of the oil by hydrolysis and oxidation. Vegetable oil processing techniques were recently reviewed [147–149].

3.6.1 Mechanical pressing Several costly pre-treatments of the oleaginous seeds, such as drying, dehulling, flaking and cooking, may precede mechanical pressing, usually continuous single-screw (expeller) processing. A cold-press expeller process is often preferred and used by most small-scale crushers. First, an extruder can be many times more costly than a regular expeller, making it less feasible for smaller operations. Second, using a hot-press mechanism increases input costs (i.e. energy) to a degree not currently justified. Third, using hexane increases production costs and complicates the feasibility of small-scale, on-farm production. Recovery efficiencies of 80% are typical for smallscale, cold-press expeller crushing techniques. The expeller is less efficient on seeds with lower oil content. Other drawbacks of mechanical extraction are higher operating costs, the need for more material storage and handling, more maintenance and more operators. Olive, flaxseed and avocado are examples of cold pressing, which yields the better (edible) oil; palm kernel and babassu are hot pressed. The maximum temperature of ‘cold pressing’ is 300 K. Depending on the pressing procedures, temperatures of 333 K may be reached in olive oil extraction. Oilseeds yield their oil more readily to mechanical expression after cooking (e.g. in the case of cottonseed). Oil extraction of palm fruit bunches is a complex process, that may be carried out by large mills in plantations (up to 60 t fruit/h) or by small mills in rural villages (1 t oil in 8 h shift). In either case, oil extraction from fruit follows the same basic steps (Table 3.9). Palm oil production from fruit involves sterilisation, mechanical removal of fruit from the bunch, and mechanical breakdown of the fruit structure followed by expression of the oil in a screw press. Oil yield represents 25% of the fresh fruit bunch (FFB). Solvent extraction is rarely used.

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Action

1 2 3 4 5 6 7 8 9

Steam sterilisation of bunches Stripping fruit from bunches Crushing, digestion and heating of fruit Oil extraction from macerated fruit (hydraulic pressing) Palm oil clarificationa Separating fibre from endocarp Drying, grading, and cracking of endocarp Separating endocarp from kernel Kernel drying and packing

a

Product is termed crude palm oil.

A screw press makes it possible to have a continuous feeding of seeds. High-oil content seeds, such as copra, are difficult to express by a single pressing. The use of twin-screw extruders for oil extraction provides an alternative to traditional procedures which has received but little attention for rapeseeds [150] and oleic sunflower seeds [151]. Direct expression of oleic sunflower in a twin-screw extruder yields high-quality oil (acidity < 2 mg KOH/g).

3.6.2 Solvent extraction The screw press process is no longer the most common type of oil extraction. Vegetable oil producers are now more likely to use a closed-loop solvent extraction system that involves less mechanical force and produces vegetable oil at lower cost. Ordinary (high-pressure) mechanical expression results in considerably more oil (up to 10–15%) remaining in the seed cake compared to solvent extraction. The protein-rich seed cake for feed is important in determining profitability of oilseed cultivation. Solvent extraction constitutes the most efficient method for the recovery of oil from any oil-bearing material and is most advantageous for processing of low-oil seeds. Trichloroethene, ether, n-hexane and lower alkanes have been used. Chemicals present inherent dangers (health, explosions). Hexane is relatively inexpensive. Hexane solvent extraction can be used in isolation or along with the oil press/expeller method. Chemical extraction yields depend on the operating conditions, typically as follows: seed/solvent ratio, 1:18 w/w%; reaction temperature, 323 K; contact time, 2 h (rapeseed) or 1 h (sunflower). Contact mode depends on granulometry, with immersion for finely ground oilseeds and countercurrent percolation for larger particle sizes. Chemical extraction can be continuous (> 250–500 t/d) or batch. In optimal conditions commercial solvent extraction reduces the oil content of the dry solid residue to < 0.1%.

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Soybeans (which account for 32% of edible oils), cottonseed, and rice bran are all solvent (hexane) extracted. Also palm kernel is usually solvent extracted (5% on FFB basis). Substitution of solvent extraction for pressing methods increases the yield of oil from soybeans by 12.1%, from cottonseed by 11.5% and from flaxseed by only 5.3%. Solvent extraction of lipids from soybeans with acidic hexane (containing 5 vol% acetic acid) yielded roughly 6–10% more neutral oil than did hexane extractions [152]. High-quality oil and improved meal of canola are obtained by two-phase solvent extraction using 10% (w/w) NH3 in 95/5% (vol./vol.) CH3OH/H2O as a polar phase and hexane as a non-polar phase [153]. Castor oil, olive oil and wheat germ oil residuals from mechanical pressing are also solvent extracted. The most common solvents used for oil and fat extraction are light paraffinic petroleum fractions (C5-C8). However, EPA classifies hexane as a hazardous air pollutant and its release is regulated. The crushing facility must take steps to contain emissions and to ensure worker safety. Local legislation and authorities usually require permission for installation and operation of a solvent extraction plant. Because of the 1990 Clean Air Act and potential health risks, an alternative solvent or solvent system may eventually replace n-hexane as the extraction agent of vegetable oils. Kuk and Hron [154] reported a system of isohexane and either 5 to 25% ethanol or isopropyl alcohol to extract cottonseed oil. Less odorous cottonseed meals were obtained by extraction with mixtures of acetone and n-hexane [155]. Conventional wisdom holds that combining oil crushing and biodiesel production is too expensive for all but the largest producers. This puts biodiesel producers at the mercy of a volatile market. While solvent-based systems generally suffer from higher capital costs (about twice that of mechanical systems), recently solvent-based oil extraction systems have been designed which are cost competitive with mechanical oilseed crushers and give biodiesel producers more control over their feedstock costs [156]. A solvent extraction system can provide economical operation for biodiesel plants as small as 15 Mgy to 20 Mgy (50 to 67 kt). The solvent extraction developed by SRS Engineering Corp. (Murrieta, CA) cleans, cracks and cooks oilseeds with steam before flaking and drying [156]. Oil is extracted from the flaked seed with hexane. For biodiesel production the crude vegetable oil obtained needs degumming by adding phosphoric or citric acid, bleaching, filtration and deacidification. Both the obtained FFA- and water-free oil and FFA distillates can be used to produce biodiesel. No costly reworking of the biodiesel product is required. On the other hand, solvent extraction systems requiring caustic washing remove FFA from the oil and thereby lose 2–4% in overall yield.

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3.6.3 Mixed mechanical/solvent extraction Hexane solvent extraction can be used in isolation or along with the oil press/expeller method. After the oil has been extracted using an expeller, the remaining pulp can be further processed with (cyclo)hexane to extract the remaining oil content. The oil dissolves in the (cyclo-)hexane, and the pulp is filtered out from the solution. Oil and solvent are separated by distillation. The hexane process increases oil removal efficiency in a strictly cold-pressed process. Current procedures for the industrial extraction of sunflower seeds involve a two-step process of mechanical pressing followed by extraction with hexane. Prior to extraction of oil, sunflower seeds are frequently dehulled in order to improve the oil and meal quality and increase the capacity and efficiency of the extraction plant (see Fig. 3.7). Economical utilisation of the hull material is industrially important. Hulls are mainly used for heat production, as animal feed and fertiliser. Seventy-five percent of the oil of sunflower seeds can be extracted by crushing with rollers, and the fatty cake then contains about 15% of oil. The oil level of the cake can be reduced to less than 2% by solvent extraction. Also corn germ is pressed and then often solvent (hexane) extracted (See Section 5.5). Similarly, conventional commercial processing of babassu and rapeseed involves mechanical pressing and solvent extraction to separate oil and meal. Today’s oil market situation favours pre-pressing (PP) and solvent extraction (SE) over full-pressing (FP). Two-step full-pressing is applicable to most soft seeds; 65 to 75% of the oil is separated under moderate pre-pressing conditions. Light coloured oils are obtained with low non-hydratable and total phosphatide content. There are promising approaches to improve the oil yields of full-pressing operations to reduce the cost gap of FP to PP/SE.

Oilseed (100) Dehulling

Hulls (30–40)

Kernels (60–70) Pre-press solvent extraction

Meal (30–35)

Oil (30–35)

3.7 Materials balance (wt%) for sunflower seed (after ref. [157]).

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3.6.4 New processing techniques There is a need for the development of new processing techniques to facilitate vegetable oil extraction and refining while sustaining the nutritional components naturally present in edible oils and reducing the adverse impact of oil processing on the environment. It is well known that, during milling of oleaginous seeds, a high percentage of the antioxidants is lost in the mill’s wastewaters [158]. Supercritical CO2 (scCO2) extraction and fractionation techniques are alternative methods to obtain oil of high quality and purity [159]. Supercritical fluid extraction (SFE) is attracting a great deal of interest because the technique can reduce considerably sample extraction time, and oil recovery (almost 100%) is better than that of most classical extraction techniques for solid and semisolid samples [160]. However, the method needs special equipment for containment and pressure in supercritical CO 2 (scCO2) extraction. SFE is generally carried out in a mechanically stirring or rocking batch reactor at the solvent’s critical temperature and pressure (304.3 K and 7.29 Mha for CO2). For an overview on the solubility behaviour of lipid components in scCO2, see ref. [161]. Soybean oil has been deacidified using supercritical CO2 and membrane technology [162]. The American Oil Chemists’ Society has approved an official method to determine oil in oilseeds through supercritical fluid extraction (SFE) [163]. Quantitative supercritical-fluid-based extraction employing scCO2 is becoming increasingly popular, as reported for pecan oil [164], soy and corn soapstocks [165], walnut [166], flaxseed [167], dry macroalgae [168] and jojoba oils [169]. Similarly, SFE of oil from palm-pressed mesocarp fibre (E. guineensis) has been reported [170]. The technique can be used to determine the oil content in copra and its meal in less than 10 min. Rice bran was extracted by means of scCO2 and liquid propane and compared with accelerated solvent extraction (ASE) with hexane [171]. Neither process resulted in a positive rate of return on investment. Supercritical extraction is used industrially in the decaffeination of coffee beans [172], extraction of fragrances and essences from plant material [173], of fats in food [174], of fatty acids and hydrocarbons from algae [168], and of additives in polymers [160]. SFE technology has been used increasingly for the processing of nutraceuticals, including bioactive lipids, on a commercial level as it provides a solvent-free product. Supercritical technologies for oil processing have been reviewed [161]. Recently, some new approaches have been proposed for the extraction of oil from plant materials, such as three-phase partitioning (TPP) of SBO [175], enzyme-assisted three-phase partitioning (EATPP) of jatropha [176], and aqueous enzymatic oil extraction (AEOE) of rice bran [177] and peanut (using Protizyme™) [178]. Some oilseeds, such as soybean, are inefficiently

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Biodiesel science and technology

extracted by mechanical expression alone. In these cases preconditioning of the oilseeds by enzymatic hydrolysis is an option. Enzymatic hydrolysis results in higher oil yields, higher extraction rates and improved product characteristics. Enzymatic extraction of oil from the Chilean hazelnut (G. avellana) was compared with extraction in aqueous medium [179]. Extraction speeds may be enhanced by sonication [176]. At a laboratory level extraction techniques are even more numerous and range from conventional extraction technologies (reflux, Soxhlet, etc.) to ultrasonically assisted extraction and high-pressure solvent extraction methods (SFE, ASE, subcritical water extraction and microwave-assisted extraction). For characterising features of these techniques, see ref. [160]. Soxhlet extraction is notoriously slow. Soxhlet extraction for at least 2 h or ASE for 20 min are more reliable methods for the determination of FFA in cottonseed than the AOCS Official Method Aa 6-38 [180]. Matthäus and Brühl [181] have reported a comparison of different methods (SFE, ASE, MAE, Soxtherm and solid fluid vortex extraction) for the determination of the oil content in various oilseeds (rapeseed, sunflower and soybean). FA profiles of catfish liver oils were analysed using a microwave-assisted method [182].

3.6.5 Crude oil refining Physical and chemical properties of vegetable oils vary with the method of extraction. For example, cold-pressed castor oil has low acid value (3 mg/g), low iodine number (82–88 g I2/hg) and a slightly higher saponification value (179–185 mg KOH/g) than solvent-extracted oil (3 mg/g, 80–88 g I 2/hg, 177–182 mg KOH/g, respectively), and is lighter in colour [183]. Cooking and drying conditions for oilseeds preparatory to screw pressing influence the screw press performance. Cold-pressed whole flaxseeds are an excellent source of linolenic acid. Wan and Dowd [184] have compared the influence of various extraction techniques (hydraulic pressing, room temperature and Soxhlet solvent extraction) on the free fatty acid (FFA) concentration of cottonseed oil. Seed abuse prior to processing deteriorates the product. Low acidity oils can be obtained by shortening the time between collection of the mature crop and processing (at room temperature) in N2 atmosphere, as shown for olive oil [185]. Storing olives for protracted periods accounts for a rather high FFA content in the oil. Good palm plantation oil consistently runs lower than 5% in FFA, whereas native-produced oil may contain up to 50% FFA. Crude vegetable oils (VOs) and fats may contain other materials, notably fatty acids (typically 1–5%), water, saccharides, antioxidants, proteins, aminoacids, hydrocarbons, flavours, colorants, enzymes, alcohols, particulates, metal salts, and N-, S- and P-containing compounds. The sulphur content of

Crude oil

Liquid-liquid extraction

Centrifugation

Oil

Diluted soda

Aqueous

Centrifugation

Aqueous

Polar organics Degumming

Water/soap Caustic treatment

Clays/impurities

Wax crystals

Oil T279–281K Wax crystals

Dewaxing

Filtration Crystallisation

Oil

Oil + special clays

Bleaching

Refined oil

3.8 Main crude oil refining steps consisting of degumming, caustic treatment, bleaching and dewaxing.

Oleochemical sources

Filtration Oil 291 K

Oil

99

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Biodiesel science and technology

VOs is mainly due to glucosinolates and their breakdown products, while the phosphorous content is related to the presence of phospho- and glycolipids. It is preferable to remove most of such materials by a suitable method such as filtration, distillation, etc. prior to the transesterification reaction, when the other materials may interfere in the production process or affect the final product quality. Crude palm oil has a strong negative odour and oxidised coconut oil smells soapy. After isolation, crude oils are therefore given physical and chemical pretreatments for several reasons. The main aim of refining crude oils (Fig. 3.8) is to remove impurities and other undesirable constituents (gums or slimes) to give an oil impurity content of about 0.1%. Refining includes: oil degumming consisting in a liquid–liquid extraction process with aqueous phosphoric acid followed by centrifuging to selectively remove all of the leftover solid and colloidal plant matter and polar organics (e.g. phospholipids, lecithin); caustic treatment of the degummed oil to remove FFAs as soaps, followed by centrifuging; removing coloured matter by bleaching (with Fuller’s earth or activated charcoal); deodorising by steam treatment at high T and low p; and dewaxing or winterising by cooling the anhydrous oil to 279–281 K and removing unwanted waxes (esters of long-chain alcohols and fatty acids) that precipitate out. Dewaxed vegetable oil feedstocks improve pour and cloud points of the final biodiesel product. The application of degumming is essential with oil feedstocks. Oils with higher gum contents tend to exhibit more storage problems. On the other hand, refining usually also decreases oxidation stability as a result of loss of antioxidants (tocopherols). Liquid–liquid extraction is used to deacidify high-acidity oils. The method is based on the different solubilities of fatty acids and triglycerides in organic solvents such as methanol [186]. The free fatty acid content of seed oils can also be reduced by supercritical fractionation techniques. For example, supercritical fluid fractionation is a viable process to remove FFAs efficiently from both hexane- and scCO2-extracted wheat germ oil while retaining bioactive components in the final product [187]. Distillation methods include vacuum, steam, molecular and extraction distillation. Semirefined and refined (RBD) vegetable oils are the predominant feedstocks for the production of biodiesel. Partially refined products are obtained when one or more of the usual refining stages are omitted. Bleaching and deodorisation are often omitted in commercial partially refined fats and oils. However, neutralisation, bleaching and deodorisation of oils before biodiesel production contribute to the oxidative stability of the end product.

3.7

Bibliography

D.E. Vance and J.E. Vance (eds), Biochemistry of Lipids, Lipoproteins, and Membranes, 5th edn, Elsevier, Amsterdam (2008).

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F. Shahidi (ed.), Maximising the Value of Marine By-Products, Woodhead Publishing Ltd, Cambridge (2007). H. Breivik (ed.), Long-Chain Omega-3 Speciality Oils, The Oily Press, Bridgwater (2007). M.K. Gupta, Practical Guide to Vegetable Oil Processing, AOCS Press, Urbana, IL (2007). F. Shahidi, Nutraceutical and Specialty Lipids and their Co-Products, CRC Press, Boca Raton, FL (2006). K. Larsson, P. Quinn, K. Sato and F. Tiberg, Lipids: Structure, Physical Properties and Functionality, vol. 19, The Oily Press Lipid Library, Bridgwater (2006). F. Shahidi (ed.), Bailey’s Industrial Oils and Fat Products, 6th edn, 6 vols, Wiley-Interscience, Hoboken, NJ (2005). S. Erhan (ed.), Industrial Uses of Vegetable Oils, AOCS Press, Urbana, IL (2005). R.M. Goodman (ed.), Encyclopedia of Plant and Crop Science, Marcel Dekker, New York, NY (2004). D.L. Luthria (ed.), Oil Extraction and Analysis: Critical Issues and Comparative Studies, AOCS Press, Urbana, IL (2004). W.W. Christie, Lipid Analysis, Vol. 15, The Oily Press Lipid Library, Bridgwater (2003). J.A. Duke, Handbook of Energy Crops, Purdue University Center for New Crops and Plant Products, West Lafayette, IN (2003); http://www.hort. purdue.edu./newcrop T.M. Kuo and H.W. Gardner (eds), Lipid Technology, Marcel Dekker, New York, NY (2002). F.D. Gunstone and R.J. Hamilton (eds), Oleochemical Manufacture and Applications, Sheffield Academic Press and CRC, Sheffield/Boca Raton, FL (2001). H. Zoebelein (ed.), Dictionary of Renewable Resources, 2nd edn, WileyVCH, Weinheim (2001). R.D. O’Brien, W. Farr and P.J. Wan (eds), Introduction to Fats and Oils Technology, 2nd edn, AOCS Press, Urbana, IL (2000). W. Hamm and R.J. Hamilton, Edible Oil Processing, Sheffield Academic Press and CRC, Sheffield/Boca Raton, FL (1999). R.D. O’Brien, Fats and Oils: Formulating and Processing for Applications, Technomic Publ. Co., Lancaster, PA (1998). D.L. Klass, Biomass for Renewable Energy, Fuels and Chemicals, Academic Press, San Diego, CA (1998). J.L. Harwood (ed.), Plant Lipid Biosynthesis: Fundamentals and Agricultural Applications, Cambridge University Press, Cambridge (1998). J.L. Castner, S.L. Timme and J.A. Duke, A Field Guide to Medicinal and Useful Plants of the Upper Amazon, Feline Press, Gainsville, FL (1998).

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T. Clifford, Fundamentals of Supercritical Fluids, Oxford University Press, Oxford (1998). E.N. Frankel, Lipid Oxidation, The Oily Press, Dundee (1998). D.A. Fell, Understanding the Control of Metabolism, Portland Press, London (1997). J.P. Williams, M.U. Khan and N.W. Lem (eds), Physiology, Biochemistry and Molecular Biology of Plant Lipids, Kluwer Academic Publishers, Dordrecht (1997). M.S. Verrall (ed.), Supercritical Fluid Extraction and Chromatography, John Wiley & Sons, Ltd, Chichester (1996). M.A. McHugh and V.J. Krukonis, Supercritical Fluid Extraction – Principles and Practice, Butterworth-Heinemann, Boston, MA (1996). L.T. Taylor, Supercritical Fluid Extraction, John Wiley & Sons, Ltd, Chichester (1996). J.C. Kader and O. Mazliak (eds), Plant Lipid Metabolism, Kluwer Academic Publishers, Dordrecht (1995). D.S. Kimber and D.I. McGregor (eds), Brassica Oilseeds: Production and Utilization, CABI Publishing, Wallingford (1995). D.R. Erickson (ed.), Practical Handbook of Soybean Processing and Utilization, AOCS Press, Urbana, IL (1995). F.D. Gunstone, J.L. Harwood and F.B. Padley, The Lipid Handbook, 2nd edn, Chapman & Hall, London (1994). K.A. Larsson, Lipids: Molecular Organization, Physical Functions and Technical Applications, The Oily Press, Dundee (1994). H. Kigel and G. Galili (eds.), Seed Development and Germination, Marcel Dekker, New York, NY (1994). T.S. Moore Jr. (ed.), Lipid Metabolism in Plants, CRC Press, Boca Raton, FL (1993). F.C. Naughton (ed.), The Chemistry of Castor Oil and Its Derivatives and Their Applications, ICOA Technical Bulletin No. 2, ICOA, Westfield, NJ (1992). F.D. Gunstone and B.G. Herslöf, A Lipid Glossary, The Oily Press, Dundee (1992). A. Cherif, D.B. Miled-Daoud, B. Marzouk, A. Smaoui and M. Zarrouk (eds), Metabolism, Structure and Utilisation of Plant Lipids, Centre Pedagogique, Tunis (1992). T.J. Bruno and J.F. Ely (eds), Supercritical Fluid Technology: Reviews in Modern Theory and Applications, CRC Press, Boca Raton, FL (1991). P.J. Quinn and J.L. Harwood (eds), Plant Lipid Biochemistry, Structure and Utilization, Portland Press, London (1990). S. Facciola, Cornucopia – A Source Book of Edible Plants, Kampong Publications, Vista, CA (1990). B.A. Stout, The Handbook of Energy for World Agriculture, Elsevier, Amsterdam (1990).

Oleochemical sources

103

G.M. de Rougemont, A Field Guide to the Crops of Britain and Europe, Collins, London (1989). G. Röbbelen, R.K. Downey and A. Ashri (eds), Oil Crops of the World, McGraw-Hill, New York, NY (1989). P.A. Biacs, K. Gruiz and T. Kremmer (eds), Biological Role of Plant Lipids, Akadémiai Kiadó, Budapest and Plenum Publishing, New York, NY (1989). C. Ratledge and S.G. Wilkinson (eds), Microbial Lipids, Academic Press, San Diego, CA (1989). G. Hoffman, The Chemistry and Technology of Edible Oils and Fats and Their High Fat Products, Academic Press, London (1989). C.W.S. Hartely, The Oil Palm, Longman Publishers, London (1988). R. Mansfeld, Verzeichnis landwirtschaftlicher und gärtnerischer Kulturpflanzen, Springer-Verlag, Berlin (1986). E.S. Pattison (ed.), Fatty Acids and Their Industrial Application, Marcel Dekker, New York, NY (1986). J.M.L. Penninger, M. Radosz, M.A. McHugh and V.J. Krukonis (eds), Supercritical Fluid Technology, Elsevier, Amsterdam (1985). G. Kunkel, Plants for Human Consumption, Koeltz Scientific Book, Koenigstein (1984). P.A. Siegenthaler and W. Eichenberger (eds), Structure, Functions and Metabolism of Plant Lipids, Elsevier, Amsterdam (1984). P. Mazliak, P. Benveniste, C. Costes and R. Douce (eds), Biogenesis and Function of Plant Lipids, Elsevier/North-Holland, Amsterdam (1980). D.R. Erickson, E.H. Pryde, O.L. Brekke, T.L. Mounts and R.A. Falb, Handbook of Soy Oil Processing and Utilization, American Soybean Association and American Oil Chemistry Society, St. Louis, MO, and Champaign, IL (1980). J.D. Weete, Lipid Biochemistry of Fungi and Other Organisms, Plenum Press, New York, NY (1980). G. Usher, A Dictionary of Plants Used by Man, Constable & Co., London (1974). T.P. Hilditch and P.N. Williams, The Chemical Constitution of Natural Fats, Chapman & Hall, London (1964). J.C. Th. Uphof, Dictionary of Economic Plants, Hafner Publishing Co., New York, NY (1959).

3.8

References

[1] FAOSTAT, ProdStat: Crops, Food and Agriculture Organization of the United Nations, Rome (2007). [2] R.C. da Silva and L.A. Gioielli, Physical properties of structured lipids from lard and soybean oil, Rev. Bras. Ciênc. Farm. 42 (2006) 223–35 (in Portuguese). [3] U. Ravnskov, The Cholesterol Myth Exposing the Fallacy that Saturated Fat and Cholesterol Cause Heart Disease, New Trends Publishing, Inc., Washington, DC (2000).

104

Biodiesel science and technology

[4] J.B. Ohlrogge and J. Browse, Lipid biosynthesis, Plant Cell 7 (1995) 957–70. [5] J.B. Ohlrogge, J.G. Jaworski and D. Post-Beitenmiller, De novo fatty acid biosynthesis, in Lipid Metabolism in Plants (T.S. Moore Jr., ed.), CRC Press, Boca Raton, FL (1993), pp. 3–32. [6] A.J. Kinney, Genetic modification of the storage lipids of plants, Curr. Opin. Biotechnol. 5 (1994) 144–51. [7] M. Miquel and J. Browse, Lipid biosynthesis in developing seeds, in Seed Development and Germination (J. Kigel and G. Galili, eds), Marcel Dekker, New York, NY (1994), pp. 169–93. [8] R. Töpfer, N. Martini and J. Schell, Modification of plant lipid synthesis, Science 268 (1995) 681–6. [9] T.P. Hilditch and P.N. Williams, The Chemical Constitution of Natural Fats, Chapman & Hall, London (1964). [10] R. Sambanthamurthi, K.-C. Oo and A.S.H. Ong, Lipid metabolism in oil palm (Elaeis guineensis and Elaeis oleifera) protoplasts, Plant Sci. 51 (1987) 97–103. [11] J.J. Salas, J. Sánchez, U.S. Ramli, A.M. Manaf, M. Williams and J.L. Harwood, Biochemistry of lipid metabolism in olive and other oil fruits, Progr. Lipid Res. 39 (2000) 151–80. [12] K. Dehesh, P. Edwards, J. Fillatti, M. Slabaugh and J. Byrne, KAS IV: A 3-ketoacylACP synthase from Cuphea sp. is a medium chain specific condensing enzyme, Plant J. 15 (1998) 383–90. [13] S. Stymne and A.K. Stobart, Triacylglycerol biosynthesis, Biochem. Plants 9 (1987) 175–214. [14] C. Stoll, W. Lühs, M. K. Zarhloul and W. Friedt, Genetic modification of saturated fatty acids in oilseed rape (Brassica napus), Eur. J. Lipid Sci. Technol. 107 (2005) 244–8. [15] K. Dehesh, P. Edwards, T. Hayes, A.M. Cranmer and J. Fillatti, Two novel thioesterases are key determinants of the bimodal distribution of acyl chain length of Cuphea palustris seed oil, Plant Physiol. 110 (1996) 203–10. [16] T. Voelker, Plant acyl-ACP thioesterases: chain-length determining enzymes in plant fatty acid biosynthesis, Genet. Engng. 18 (1996) 111–33. [17] J.L. Harwood, Recent advances in the biosynthesis of plant fatty acids, Biochem. Biophys. Acta 1301 (1996) 7–56. [18] F.D. Gunstone, J.L. Harwood and F.B. Padley, The Lipid Handbook, 2nd edn, Chapman & Hall, London (1994). [19] P.K. Stumpf, D.N. Kuhn, D.J. Murphy, M.R. Pollard, T.A. McKeon and J.J. MacCarthy, Oleic acid, the central substrate, Developm. Plant Biol. 6 (1980) 3–10. [20] W.E. Shine, M. Mancha and P.K. Stumpf, Fat metabolism in higher plants. Function of acyl thioesterases in the metabolism of acyl-coenzymes A and acyl-acyl carrier proteins, Arch. Biochem. Biophys. 172 (1976) 110–16. [21] T.A. McKeon and P.K. Stumpf, Purification and characterization of stearoyl-ACP desaturase and the acyl-ACP thioesterase from maturing seeds of safflower, J. Biol. Chem. 257(20) (1982) 12141–7. [22] E. Heinz and P.G. Roughan, Similarities and differences in lipid metabolism of chloroplasts isolated from 18:3 and 16:3 plants, Plant Physiol. 72 (1983) 273–9. [23] I.K. Vijay and P.K. Stumpf, Fat metabolism in higher plants. XLVI. Nature of the substrate and product of oleyl coenzyme A desaturase from Carthamus tinctorius, J. Biol. Chem. 246 (1971) 2910–17.

Oleochemical sources

105

[24] J.L. Harwood and I.A. Gushina, The versatility of algae and their lipid metabolism, Biochem. 91 (2009) 679–84. [25] J.F. Toro-Vazquez, M.A. Charó-Alonso and F. Pérez-Briceño, Fatty acid composition and its relationship with physicochemical properties of pecan (Carya illinoensis) oil, J. Am. Oil Chem. Soc. 76 (1999) 957–65. [26] E.P. Kennedy, Biosynthesis of complex lipids, Fed. Proc. Am. Soc. Exp. Biol. 20 (1961) 934–40. [27] T. Voelker and A.J. Kinney, Variations in the biosynthesis of seed-storage lipids, Annu. Rev. Plant Physiol. Plant Mol. Biol. 52 (2001) 335–61. [28] H. Drexler, P. Spiekermann, A. Meyer, F. Domergue, T. Zank, P. Sperling, A. Abbadi and E. Heinz, Metabolic engineering of fatty acids for breeding of new oilseed crops: strategies, problems and first results, J. Plant Physiol. 160 (2003) 779–802. [29] J.L. Harwood, Plant acyl lipids: structure, distribution and analysis, in Biochemistry of Plants (P.K. Stumpf, ed.), Vol. 4, Academic Press, New York, NY (1980), pp. 2–58. [30] F.J. van de Loo, B.G. Fox and C. Somerville, Unusual fatty acids, in Lipid Metabolism in Plants (T.S. Moore Jr., ed.), CRC Press, Boca Raton, FL (1993), pp. 91–126. [31] E.J. Whittle, A.E. Tremblay, P.H. Buist and J. Shanklin, Revealing the catalytic potential of an acyl-ACP desaturase: tandem selective oxidation of saturated fatty acids, Proc. Natl. Acad. Sci. 105 (2008) 14738–43. [32] K.M. Schmid and J.B. Ohlrogge, Lipid metabolism in plants, in Biochemistry of Lipids, Lipoproteins and Membranes, 5th edn (D.E. Vance and J.E. Vance, eds), Elsevier, Amsterdam (2008), Ch. 4. [33] C. Hou and J.-F. Shaw (eds), Biocatalysis and Biotechnology for Functional Foods and Industrial Products, AOCS Press, Urbana, IL (2007). [34] J.M. Dyer, S. Stymne, A.G. Green and A.S. Carlsson, High-value oils from plants, Plant J. 54 (2008) 640–55. [35] M. Frentzen, Acyltransferases from basic science to modified seed oils, Fett/Lipid 100 (1998) 161–6. [36] T.A. Voelker, T.R. Hayes, A.M. Cranmer, J.C. Turner and H.M. Davies, Genetic engineering of a quantitative trait: metabolic and genetic parameters influencing the accumulation of laurate in rapeseed, Plant J. 9(2) (1996) 229–41. [37] F.B. Padley, F.D. Gunstone and J.L. Harwood, Occurrence and characteristics of oils and fats, in The Lipid Handbook (F.D. Gunstone, J.L. Harwood and F.B. Padley, eds), Chapman & Hall, London (1994), pp. 49–170. [38] J.N. Siedow, Plant lipoxygenase: structure and function, Annu. Rev. Plant Physiol. Plant Mol. Biol. 42 (1991), pp. 145–88. [39] M.T. Morales, R. Aparicio and J.J. Rios, Dynamic headspace gas chromatographic method for determining volatiles in virgin olive oil, J. Chromatogr. 668 (1994) 455–62. [40] K.G. Berger, Production of palm oil from fruit, J. Am. Oil Chem. Soc. 60 (1983) 206–10. [41] J.M. Ortega-Nieto, La Poda del Olivo, Ministerio de Agricultura, Madrid (1962). [42] R.R. Leathers and A.H. Scragg, The effect of different temperatures on the growth, lipid content and fatty acid composition of Theobroma cacao cell suspension cultures, Plant Sci. 62 (1989) 217–27.

106

Biodiesel science and technology

[43] D.T. Canvin, The effect of temperature on the oil content and fatty acid composition of the oils from several oil seed crops, Can. J. Bot. 43(1) (1965) 63–9. [44] C. Hitchcock and B.W. Nichols, Plant Lipid Biochemistry, Academic Press, London (1971), pp. 152–4. [45] S.G. Silver, C.P. Rochester, D.G. Bishop and H.C. Harris, Unsaturated fatty acid synthesis during the development of isolated sunflower (Helianthus annuus L.) seeds, J. Exp. Bot. 35(159) (1984) 1507–14. [46] H.C. Harris, J.R. McWilliam and W.K. Mason, Influence of temperature on oil content and composition of sunflower seed, Austr. J. Agric. Res. 29(6) (1978) 1203–12. [47] G.J. Seiler, Analysis of the relationships of environmental factors with seed oil and fatty acid concentrations of wild annual sunflower, Field Crops Res. 15 (1986) 57–72. [48] R.J. Weselake, D.C. Taylor, M.K. Pomeroy, S.L. Lawson and E.W. Underhill, Properties of diacylglycerol acyltransferase from microspore-derived embryos of Brassica napus, Phytochem. 30 (1991) 3533–8. [49] R. Sambanthamurthi, C.C. Let, O.K. Cheang, Y.K. Huat and P. Rajan, Chillinginduced lipid hydrolysis in the oil palm (Elaeis guineensis) mesocarp, J. Exp. Bot. 42 (1991) 1199–205. [50] K. Brahim, D.K. Stumpf, D.T. Ray and D.A. Dierig, Lesquerella fendleri seed oil content and composition: harvest date and plant population effects, Ind. Crops Prod. 5 (1996) 245–52. [51] E.M. Gaydou, Y. Lozano and J. Ratovohery, Triglyceride and fatty acid compositions in the mesocarp of Persea americana during fruit development, Phytochem. 26 (1987) 1595–7. [52] F. Ozdemir and A. Topuz, Changes in dry matter, oil content and fatty acids composition of avocado during harvesting time and post-harvesting ripening period, Food Chem. 86 (2004) 79–83. [53] Z. Flagella, T. Rotunno, E. Tarantino, R. Di Caterina and A. De Caro, Changes in seed yield and oil fatty acid composition of high oleic sunflower (Helianthus annuus L.) hybrids in relation to the sowing date and the water regime, Eur. J. Agron. 17 (2002) 221–30. [54] T. Durrett, C. Benning and J. Ohlrogge, Plant triacylglycerols as feedstocks for the production of biofuels, Plant J. 54 (2008) 593–607. [55] J.B. Ohlrogge, Design of new plant products: engineering of fatty acid metabolism, Plant Physiol. 104 (1994) 821–6. [56] D.J. Murphy, Engineering oil production in rapeseed and other oil crops, Trends Biotechnol. 14 (1996) 206–13. [57] A.J. Kinney, Genetic engineering of oilseeds for desired traits, in Genetic Engineering (J.K. Setlow, ed.), Vol. 19, Plenum Press, New York, NY (1997), pp. 149–64. [58] M.E. Tat, P.S. Wang, J.H. Van Gerpen and T.E. Clemente, Exhaust emissions from an engine fueled with biodiesel from high-oleic soybeans, J. Am. Oil Chem. Soc. 84 (2007) 865–9. [59] J.J. Fillatti, N.A. Bringe and K. Dehesh, Nucleic acid constructs and methods for producing altered seed oil compositions, US Pat. Appl. 2004/0107460 A1 (3 June 2004). [60] W.D. Hitz (E. I. du Pont de Nemours & Co.), Nucleotide sequences of canola and soybean palmitoyl-ACP thioesterase genes and their use in the regulation of

Oleochemical sources

107

fatty acid content of the oils of soybean and canola plants, US Pat. 5,955,650 (21 Sept. 1999). [61] T. Buhr, S. Sato, F. Ebrahim, A.Q. Xing, Y. Zhou, M. Mathiesen, B. Schweiger, A. Kinney, P. Staswick and T. Clemente, Ribozyme termination of RNA transcripts down-regulate seed fatty acid genes in transgenic soybean, Plant J. 30 (2002) 155–63. [62] F.D. Gunstone, Oil seed crops with modified fatty acid composition, J. Oleo Sci. 50 (2001) 269–79. [63] R.F. Wilson, Genetic enhancement of vegetable oil feedstock supply and quality for biofuel applications, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [64] L.H. Princen, Potential wealth in new crops: research and development, in Crop Resources (D.S. Seigler, ed.), Academic Press, New York, NY (1977), pp. 1–15. [65] M.M. Azam, A. Waris and N.M. Nahar, Prospects and potential of fatty acid methyl esters of some non-traditional seed oils for use as biodiesel in India, Biomass Bioen. 29 (2005) 293–302. [66] G.D.P.S. Augustus and G.J. Seiler, Promising oil producing seed species of Western Ghats (Tamil Nadu, India), Ind. Crops Prod. 13 (2001) 93–100. [67] Alternative Crops Research Program, Western Illinois University (http://www. wiu.edu/Alt/Crops/). [68] D.J. Murphy, The use of conventional and molecular genetics to produce new diversity in seed oil composition for the use of plant breeders – Progress, problems and future prospects, Euphytica 85 (1995) 433–40. [69] S.J. Knapp and J.M. Crane, Registration of high oil Cuphea germplasm VL186, Crop Sci. 40 (2000) 301. [70] S.J. Knapp and J.M. Crane, Registration of reduced seed shattering Cuphea germplasm PSR23, Crop Sci. 40 (2000) 299–300. [71] S.J. Knapp, Modifying the seed storage lipids of Cuphea: a source of mediumchain triglycerides, in Seed Oils for the Future (S.L. MacKenzie and D.C. Taylor, eds), AOCS Press, Champaign, IL (1992), pp. 142–54. [72] D.P. Geller, J.W. Goodrum and S.J. Knapp, Fuel properties of oil from genetically altered Cuphea viscosissima, Ind. Crops Prod. 9 (1999) 85–91. [73] S.A. Graham, Cuphea: a new plant source of medium-chain fatty acids, Crit. Revs. Food Sci. Nutr. 28 (1989) 139–73. [74] K.S. Rathore, G. Sunilkumar, L.M. Campbell, R.D. Stipanovic and L.S. Puckhaber, Enhancing the value of cottonseed as a source of feed and food by RNAi-mediated, selective and substantial reduction in seed-gossypol, Abstr. 236th ACS Natl. Mtg., Philadelphia, PA (17–21 Aug. 2008). [75] T.A. McKeon, Transgenic oils, in Bailey’s Industrial Oil and Fat Products, 6th edn (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), Vol. 3, pp. 154–74. [76] J.A. Robertson and F.E. Barton, Oil and water analysis of sunflower seed by nearinfrared reflectance spectroscopy, J. Am. Oil Chem. Soc. 61(3) (1984) 543–7. [77] A. Fassio and D. Cozzolino, Non-destructive prediction of chemical composition in sunflower seeds by near infrared spectroscopy, Ind. Crops Prod. 20 (2004) 321–9. [78] T. Sato, Y. Takahata, T. Noda, T. Yanagisawa, T. Morishita and S. Sakai, Nondestructive determination of fatty acid composition of husked sunflower (Helianthus

108

Biodiesel science and technology

annua L.) seeds by near-infrared spectroscopy, J. Am. Oil Chem. Soc. 72(10) (1992) 1177–83. [79] B. Pérez-Vich, L. Velasco and J.M. Fernández-Martínez, Determination of seed oil content and fatty acid composition in sunflower through the analysis of intact seeds, husked seeds, meal and oil by near-infrared reflectance spectroscopy, J. Am. Oil Chem. Soc. 75(5) (1998) 547–55. [80] L. Velasco, B. Pérez-Vich and J.M. Fernández-Martínez, Nondestructive screening for oleic and linoleic acid in single sunflower achenes by near-infrared reflectance spectroscopy, Crop Sci. 39 (1999) 219–22. [81] K.M. Bewig, A.D. Clarke, C. Roberts and N. Unklesbay, Discriminant analysis of vegetable oils by near-infrared reflectance spectroscopy, J. Am. Oil Chem. Soc. 71(2) (1994) 195–200. [82] T. Sato, Application of principle-component analysis of near-infrared spectroscopic data of vegetable oils for their classification, J. Am. Oil Chem. Soc. 71 (1994) 293–8. [83] L. Velasco, B. Pérez-Vich and J.M. Fernández-Martínez, A rapid and simple approach to identify different sunflower oil types by means of near-infrared spectroscopy, J. Am. Oil Chem. Soc. 75(12) (1998) 1883–8. [84] I.V. Kovalenko, G.R. Rippke and C.R. Hurburgh, Measurement of soybean fatty acids by near-infrared spectroscopy: linear and nonlinear calibration methods, J. Am. Oil Chem. Soc. 83(5) (2006) 421–7. [85] L.Velasco, J.M. Fernández-Martínez and A. De Haro, Determination of the fatty acid composition of the oil in intact-seed mustard by near-infrared reflectance spectroscopy, J. Am. Oil Chem. Soc. 74(12) (1997) 1595–602. [86] T. Sato, I. Uezono, T. Morishita and T. Tetsuka, Nondestructive estimation of fatty acid composition in seeds of Brassica napus L. by near-infrared spectroscopy, J. Am. Oil Chem. Soc. 75(12) (1998) 1877–81. [87] B.J. Siemens and J.K. Daun, Determination of the fatty acid composition of canola, flax, and solin by near-infrared spectroscopy, J. Am. Oil Chem. Soc. 82(3) (2005) 153–7. [88] T. Sato, A.A. Maw and M. Katsuta, NIR reflectance spectroscopic analysis of the FA composition in sesame (Sesamum indicum L.) seeds, J. Am. Oil Chem. Soc. 80(12) (2003) 1157–61. [89] Y.B. Che Man and M.H. Moh, Determination of free fatty acids in palm oil by near-infrared reflectance spectroscopy, J. Am. Oil Chem. Soc. 75(5) (1998) 557–62. [90] T. Baye and H.C. Becker, Analyzing seed weight, fatty acid composition, oil, and protein contents in Vernonia galamensis germplasm by near-infrared reflectance spectroscopy, J. Am. Oil Chem. Soc. 81(7) (2004) 641–5. [91] B.E. Patrick and G.D. Jolliff, Nondestructive single-seed oil determination of meadowfoam by near-infrared transmission spectroscopy, J. Am. Oil Chem. Soc. 74(3) (1997) 273–6. [92] V. Shiva, Protect or Plunder? Understanding Intellectual Property Rights, Zed Books, London and New York, NY (2002). [93] F. Shahidi (ed.), Bailey’s Industrial Oil and Fat Products, 6th edn, 6 vols, John Wiley & Sons, Inc., Hoboken, NJ (2005). [94] A.J. Dijkstra, Revisiting the formation of trans isomers during partial hydrogenation of triacylglycerol oils, Eur. J. Lipid Sci. Technol. 108 (2006) 249–64. [95] T. Wimmer (to Vogel & Noot Industrieanlagenbau GmbH), Process for the

Oleochemical sources

109

production of fatty acid esters of lower alcohols, US Pat. 5,399,731 (21 Mar. 1995). [96] C.-C. Chang and S.-W. Wan, China’s motor fuels from tung oil, I&EC 39 (1947) 1543–8. [97] K. Kobayashi, Formation of petroleum from fish oil. Origin of Japanese petroleum, J. Chem. Ind. (Japan) 24 (1921) 1–26. [98] K. Kobayashi and E. Yamaguchi, Artificial petroleum from fish oils, J. Chem. Ind. (Japan) 24 (1921) 1399–420. [99] A. Mailhe, Preparation of a petroleum from a vegetable oil, Compt. Rend. 173 (1921) 358–9. [100] B. Melis, Experiments on the transformation of vegetable oils and animal fats to light fuels, Atti Congr. Naz. Chim. Ind. (1924), pp. 238–40. [101] J.C. Morrell, G. Egloff and W.F. Faragher, Cracking of palm oil, J. Chem. Soc. Chem. Ind. 51 (1932) 133–4T. [102] G. Egloff and J.C. Morrell, The cracking of cottonseed oil, I&EC 24 (1932) 1426–7. [103] V. Gomez Aranda, A Spanish contribution to the artificial production of hydrocarbons, Ion 2 (1942) 197–205. [104] K.D. Chapman, S. Austin-Brown, S.A. Sparace, A.J. Kinney, K.G. Ripp, I.L. Pirtle and R.M. Pirtle, Transgenic cotton plants with increased seed oleic acid content, J. Am. Oil Chem. Soc. 78(9) (2001) 941–7. [105] R. Steiss, A. Schuster and W. Friedt, Development of linseed for industrial purposes via pedigree-selection and haploid-technique, Ind. Crops Prod. 7 (1998) 303–9. [106] A. Overeem, G.J.H. Buisman, J.T.P. Derksen, F.P. Cuperus, L. Molhoek, W. Grisnich and C. Goemans, Seed oils rich in linolenic acid as renewable feedstock for environment-friendly crosslinkers in powder coatings, Ind. Crops Prod. 10 (1999) 157–65. [107] C. Stenberg, M. Svensson and M. Johansson, A study of the drying of linseed oils with different fatty acid patterns using RTIR-spectroscopy and chemiluminescence (CL), Ind. Crops Prod. 21 (2005) 263–72. [108] A. Büchsenschütz-Nothdurft, A. Schuster and W. Friedt, Breeding for modified fatty acid composition via experimental mutagenesis in Camelina sativa (L.) Crtz, Ind. Crops Prod. 7 (1998) 291–5. [109] J.W. Burton, R.F. Wilson, C.A. Brim and R.W. Rinne, Registration of soybean germoplasm lines with modified fatty acid composition of seed oil, Crop Sci. 29 (1989) 1583. [110] R.C. Leffel, Registration of BARC-12, a low linolenic acid soybean germplasm line, Crop Sci. 34 (1994) 1426–7. [111] G. Hou, G.R. Ablett, K.P. Pauls and I. Rajcan, Environmental effects on fatty acid levels in soybean seed oil, J. Am. Oil Chem. Soc. 83(9) (2006) 759–63. [112] J.C.P. Dribnenki, A.G. Green and G.N. Atlin, Linola 989 low linolenic acid flax, Can. J. Plant Sci. 76 (1996) 329–32. [113] M. Schmitt-Rozières, G. Vanot, V. Deyris and L.-C. Comeau, Borago officinalis oil: fatty acid fractionation by immobilized Candida rugosa lipase, J. Am. Oil Chem. Soc. 76(5) (1999) 557–62. [114] A. Thomas, Fats and fatty oils, in Ullmann’s Encyclopedia of Industrial Chemistry, 7th edn (M. Bohnet et al., eds), Wiley-Verlag, Weinheim (2004), Vol. A10, pp. 173–243. [115] M.S. Puthli, V.K. Rathod and A.B. Pandit, Enzymatic hydrolysis of castor oil: process intensification studies, Biochem. Engng. J. 31 (2006) 31–41.

110

Biodiesel science and technology

[116] P. Cappillino, R. Kleiman and C. Botti, Composition of Chilean jojoba seeds, Ind. Crops Prod. 17 (2003) 177–82. [117] L. Canoira, R. Alcántara, M.J. García-Martínez and J. Carrasco, Biodiesel from jojoba oil-wax: transesterification with methanol and properties as a fuel, Biomass Bioen. 30 (2006) 76–81. [118] F.P. Cuperus, G. Boswinkel and J.T.P. Derksen, The processing of new oilseed crops: an economic evaluation, J. Am. Oil Chem. Soc. 73 (1996) 1635–40. [119] J.A. Napier, The production of unusual fatty acids in transgenic plants, Ann. Rev. Plant Biol. 58 (2007) 295–319. [120] V. Spitzer, Screening analysis of unknown seed oils, Fett/Lipid 101 (1999) 2–19. [121] C.R. Smith Jr., Occurrence of unusual fatty acids in plants, Progr. Chem. Fats Other Lipids 11 (1971) 137, 139–77. [122] R.C. Badami and K.B. Patil, Structure and occurrence of unusual fatty acids in minor seed oils, Prog. Lipid Res. 19 (1980) 119–53. [123] J. Jaworski and E.B. Cahoon, Industrial oils from transgenic plants, Curr. Opin. Plant Biol. 6 (2003) 178–84. [124] M.C. Suh, D.J. Schultz and J.B. Ohlrogge, What limits production of unusual monoenoic fatty acids in transgenic plants?, Planta 215 (2002) 584–95. [125] D.C. Drown, K. Harper and E. Frame, Screening vegetable oil alcohol esters as fuel lubricity enhancers, J. Am. Oil Chem. Soc. 78 (2001) 579–84. [126] J.W. Goodrum and D.P. Geller, Influence of fatty acid methyl esters from hydroxylated vegetable oils on diesel fuel lubricity. Bioresour. Technol. 96 (2005) 851–5. [127] C. Borch-Jensen, B. Jensen, K. Mathiasen and J. Mollerup, Analysis of seed oil from Ricinus communis and Dimorphoteca pluvialis by gas and supercritical fluid chromatography, J. Am. Oil Chem. Soc. 74(3) (1997) 277–84. [128] W.B. Brown and E.H. Farmer, Unsaturated acids of natural oils: highly unsaturated acids from oiticica oil Licania rigida, Biochem. J. 29(3) (1935) 631–9. [129] A.L. Markman, L.N. Andrianova, B.K. Kruptsov, I.U. Yusupova, L.M. Yakushina and M. E. Konchalovskaya, Triacylglycerols of oiticica oil, Khim. Prirodn. Soed. (3) (1980) 316–19; J. Nat. Compds. 16 (1980) 229–32. [130] K.M. Hosamani and R.S. Pattanashettar, Mappia foetida seed oil: A rich source of oil and moderate source of novel 3-keto-octadec-cis-15–enoic acid and its possible industrial utilization, Ind. Crops Prod. 22 (2005) 135–9. [131] K.M. Hosamani, A.S. Patil and R.S. Pattanashettar, Acacia arabica varieties – Telia babul, Vediana and Cupressiformis seed oils: a moderate source of coronaric and cyclopropene fatty acids, Ind. Crops Prod. 15 (2002) 131–7. [132] J. Samuelsson and M. Johansson, A study of fatty acid methyl esters with epoxy or alkyne functionalities, J. Am. Oil Chem. Soc. 78 (2001) 1191–6. [133] H. Guth and W. Grosch, Detection of furanoid fatty acids in soya-bean oil – cause for light-induced off-flavour, Fett Wissensch. Technol. 93(7) (1991) 249–55. [134] P.K. Raju and R. Reiser, Inhibition of fatty acyl desaturase by cyclopropene fatty acids, J. Biol. Chem. 242(3) (1967) 379–84. [135] P. Blaise, M. Farines and J Souliér, Identification of cyclopentenyl fatty acids by 1H and 13C nuclear magnetic resonance, J. Am. Oil Chem. Soc. 74(6) (1997) 727–30. [136] K.M. Hosamani and R.S. Pattanashettar, Occurrence of unusual fatty acids in Ficus benghalensis seed oil, Ind. Crops Prod. 18 (2003) 139–43.

Oleochemical sources

111

[137] K.M. Hosamani and H.S. Ramesh, Unusual fatty acids from Crotolaria striata Syn. Crotolaria mucronata seed oil, Ind. Crops Prod. 14 (2001) 223–7. [138] K.M. Hosamani and R.M. Sattigeri, Industrial utilization of Rivea ornata seed oil: a moderate source of vernolic acid, Ind. Crops Prod. 12 (2000) 93–6. [139] K.M. Hosamani and H.S. Ramesh, Industrial utilization of Triumfetta pilosa, Roth seed oil: a moderate source of oil and cyclopropenoid fatty acids, Ind. Crops Prod. 17 (2003) 53–6. [140] K.M. Hosamani and R.M. Sattigeri, Analysis of Cassia marginata and Cassia corymbosa seed oils: an approach for the industrial utilization, Ind. Crops Prod. 17 (2002) 57–60. [141] K.M. Hosamani and S.S. Ganjihal, Unique occurrence of unusual fatty acids in Ochrocarpus africanus seed oil, Ind. Crops Prod. 18 (2003) 111–16. [142] K.M. Hosamani, S.S. Ganjihal and D.V. Chavadi, Alternanthera triandra seed oil: a moderate source of ricinoleic acid and its possible industrial utilisation, Ind. Crops Prod. 19 (2004) 133–6. [143] E. Fehling, S. Schönwiese, E. Klein, K. D. Mukherjee and N. Weber, Preparation of malvalic and sterculic acid methyl esters from Bombax munguba and Sterculia foetida seed oils, J. Am. Oil Chem. Soc. 75 (1998) 1757–60. [144] R. Schuch, F. Ahmad and K.D. Mukherjee, Composition of triacylglycerols containing cyclopropene fatty acids in seed lipids of Munguba (Bombax munguba Mart.), J. Am. Oil Chem. Soc. 63 (1986) 778. [145] E.M. Gaydou, J. Miralles and V. Rasoazanakolona, Analysis of conjugated octadecatrienoic acids in Momordica balsamina seed oil by GLC and carbon-13 NMR spectroscopy, J. Am. Oil Chem. Soc. 64(6) (1987) 997–1000. [146] F. Norris, Extraction of fats and oils, in Bailey’s Industrial Oil and Fat Products, Vol. 2 (D. Swern, ed.), John Wiley & Sons, Inc., New York, NY (1982), pp. 175–251. [147] F. Shahidi (ed.), Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 5, John Wiley & Sons, Inc., Hoboken, NJ (2005). [148] T.G. Kemper, Oil extraction, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 5 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 57–98. [149] M.A. Williams, Recovery of oils and fats from oilseeds and fatty materials, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 5 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 99–189. [150] R. Guyomard, Study of the Use of a Twin-Screw Extruder in Pressing-Extrusion of Oleagineous Seeds, Ph.D. Thesis, Université Technologique de Compiègne (1994). [151] C. Dufaure, J. Leyris, L. Rigal and Z. Mouloungui, A twin-screw extruder for oil extraction. Part 1. Direct expression of oleic sunflower seeds, J. Am. Oil Chem. Soc. 76(9) (1999) 1073–9. [152] T.P. Hensarling and T.J. Jacks, Solvent extraction of lipids from soybeans with acidic hexane, J. Am. Oil Chem. Soc. 60 (1983) 783. [153] M. Thobani and L.L. Diosady, Two-phase solvent extraction of canola, J. Am. Oil Chem. Soc. 74(3) (1997) 207–14. [154] M.S. Kuk and R.J. Hron, Cottonseed extraction with a new solvent system: isohexane and alcohol mixture, J. Am. Oil Chem. Soc. 75(8) (1998) 927–30. [155] M.S. Kuk, R. Tetlow and M.K. Dowd, Cottonseed extraction with mixture of acetone and acetone and hexane, J. Am. Oil Chem. Soc. 82(8) (2005) 609–12.

112

Biodiesel science and technology

[156] J.W. Kram, Do-it-yourself oil extraction, Biodiesel Mag. 5(2) (2008) 112–17. [157] K.J. Harrington and C. D’Arcy-Evans, Transesterification in situ of sunflower seed oil, I&EC Prod. Res. Dev. 24 (1985) 314–18. [158] M. Roche, C. Dufour, N. Mora and O. Dangles, Antioxidant activity of olive phenols: mechanistic investigation and characterization of oxidation products by mass spectrometry, Org. Biomol. Chem. 3(3) (2005) 423–30. [159] S.S.H. Rizvi, A.L. Benado, J.A. Zollweg and J.A. Daniëls, Supercritical fluid extraction: fundamental principles and modeling methods, Food Technol. 40 (1986) 55–65. [160] J.C.J. Bart, Additives in Polymers. Industrial Analysis and Applications, John Wiley & Sons, Ltd, Chichester (2005), pp. 51–169. [161] F. Temelli and O. Gueclue-Uestuendag, Supercritical technologies for further processing of edible oils, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 5 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 397–432. [162] W.E. Artz, T. Kinyanjui and M. Cheryan, Deacidification of soybean oil using supercritical fluid and membrane technology, J. Am. Oil Chem. Soc. 82 (2005) 803–8. [163] D. Firestone (ed.), Official Methods and Recommended Practices of the American Oil Chemists’ Society, 4th edn, AOCS, Champaign (1990), Method Am 3–96. [164] N.O. Maness, D. Chrz, T. Pierce and G.H. Brusewitz, Quantitative extraction of pecan oil from small samples with supercritical carbon dioxide, J. Am. Oil Chem. Soc. 72(6) (1995) 665–9. [165] J.W. King, S.L. Taylor, J.M. Snyder and R.L. Holliday, Total fatty acid analysis of vegetable oil soap stocks by supercritical fluid extraction/reaction, J. Am. Oil Chem. Soc. 75(10) (1998) 1291–5. [166] R. Oliveira, M.F. Rodrigues and M.G. Bernardo-Gil, Characterization and supercritical carbon dioxide extraction of walnut oil, J. Am. Oil Chem. Soc. 79(3) (2002) 225–30. [167] B. Bozan and F. Temelli, Supercritical CO2 extraction of flaxseed, J. Am. Oil Chem. Soc. 79(3) (2002) 231–5. [168] M. Aresta, A. Dibenedetto, M. Carone, T. Colonna and C. Fragale, Production of biodiesel from macroalgae by supercritical CO2 extraction and thermochemical liquefaction, Environm. Chem. Lett. 3 (2005) 136–9. [169] U. Salgin, A. Çalimli and B.Z. Uysal, Supercritical fluid extraction of jojoba oil, J. Am. Oil Chem. Soc. 81(3) (2004) 293–6. [170] H.L.N. Lau, Y.M. Choo, A.N. Ma and C.H. Chuah, Quality of residual oil from palm-pressed mesocarp fiber (Elaeis guineensis) using supercritical CO2 with and without ethanol, J. Am. Oil Chem. Soc. 83(10) (2006) 893–8. [171] D. Sparks, R. Hernandez, M. Zappi, D. Blackwell and T. Fleming, Extraction of rice bran oil using supercritical carbon dioxide and propane, J. Am. Oil Chem. Soc. 83(10) (2006) 885–91. [172] P. Hubert and O. Vitzthum (to Hag A.-G.), Separation of caffeine from supercritical solutions, Germ. Offenl. DE 2,637,197 A1 (23 Feb. 1978). [173] P. Hubert and O. Vitzthum, Liquid extraction of hops, spices and tobacco with supercritical gases, Angew. Chem. Intl. Ed. 17 (1978) 710–15. [174] J.M. Levy, V. Danielson, R. Ravey and L. Dolata, Routine determination of fats in foods using supercritical fluid extraction, LC.GC 12(12) (1994) 920–3. [175] A. Sharma, S.K. Khare and M.N. Gupta, Three phase partitioning for extraction of oil from soybean, Bioresour. Technol. 85 (2002) 327–9.

Oleochemical sources

113

[176] S. Shah, A. Sharma and M.N. Gupta, Extraction of oil from Jatropha curcas L. seed kernels by enzyme assisted three phase partitioning, Ind. Crops Prod. 20 (2004) 275–9. [177] A. Sharma, S.K. Khare and M.N. Gupta, Enzyme-assisted aqueous extraction of rice bran oil, J. Am. Oil Chem. Soc. 78(9) (2001) 949–51. [178] A. Sharma, S.K. Khare and M.N. Gupta, Enzyme-assisted aqueous extraction of peanut oil, J. Am. Oil Chem. Soc. 79(3) (2002) 215–18. [179] R.I. Santamaría, C. Soto, M.E. Zúñiga, R. Chamy and A. López-Manguía, Enzymatic extraction of oil from Gevuina avellana, the Chilean hazelnut, J. Am. Oil Chem. Soc. 80(1) (2003) 33–6. [180] P.J. Wan, D.R. Pakarinen and P.J. Wakelyn, Concerns for the determination of free fatty acid in cottonseed, J. Am. Oil Chem. Soc. 75 (1998) 1321–4. [181] B. Matthäus and L. Brühl, Comparison of different methods for the determination of the oil content in oilseeds, J. Am. Oil Chem. Soc. 78 (2001) 95–102. [182] S. Sathivel, W. Prinyawiwatkul, J.M. King, C.C. Grimm and S. Lloyd, Microwaveassisted catfish liver oil extraction and FA analysis, J. Am. Oil Chem. Soc. 80 (2003) 15–20. [183] D.S. Ogunniyi, Castor oil: a vital industrial raw material, Bioresour. Technol. 97 (2006) 1086–91. [184] P.J. Wan and M.K. Dowd, Comparative study of the extraction and measurement of cottonseed free fatty acids, J. Am. Oil Chem. Soc. 77(1) (2000) 23–7. [185] Valderrama Aceite de Oliva Virgen Extra, http://www.valderrama.es/. [186] H. Gürbüz, S. Sirkecioğlu, N. Yavasoğlu, G. Ahunbay and S. Türkay, Design of deacidification process of high acidity biodiesel feedstocks with liquid-liquid methanol extraction, Proc. Intl. Congr. on Biodiesel, Vienna (5–7 Nov. 2007). [187] M. Eisenmenger, N.T. Dunford, F. Eller, S. Taylor and J. Martinez, Pilot-scale supercritical carbon dioxide extraction and fractionation of wheat germ oil, J. Am. Oil Chem. Soc. 83(10) (2006) 863–8.

4

Vegetable oil formulations for utilisation as biofuels

Abstract: Although direct use of high-viscosity straight vegetable oils in standard modern diesel engines has been reported, the practice of using such non-regulated fuels is generally not recommended as short- and long-term problems do result. Engine compatibility for vegetable oils and animal fats may be enhanced chemically (by derivatisation, pyrolysis/gasification, ozonation) or physically (by dilution, blending, microemulsification). Fuel properties of oils and fats are outlined. Key words: Fuel properties, straight vegetable oils, low-viscosity formulations, co-solvent blending, microemulsions.

4.1

Introduction

The term biodiesel (now in use to denote monoalkyl esters of long-chain fatty acids derived from renewable feedstocks) was originally coined to describe unmodified vegetable oils that could substitute for diesel fuel (DF). Industrial use of biofuels started in the 1880s. Rudolf Diesel designed a prototype of the diesel engine, received a German patent (28 Feb. 1892), and demonstrated a workable engine in 1897 [1]. The first public demonstration by the French Otto Company of a small diesel engine operated on straight peanut (Arachis hypogaea) oil was seen at the World Fair in Paris of 1900 [2]. At that time the inventor, Diesel, held the view that the future of his engine (in contrast to those operating on steam) would be connected to fuel use derived from biomass, in particular plant oils (such as peanut and castor oil) and animal fats. Diesel’s compression-ignition engine used large injectors to prevent clogging by viscous, heavy fuels, such as unrefined vegetable oil. Because of the size of the engines, large warships were among the first users of Diesel’s technology. In the 1920s, technological changes made possible much smaller diesel engines, which required lower viscosity fuels. At the same time, the advent of relatively cheap medium-weight diesel fuels from fossil origin produced by the upcoming petroleum industry temporarily put a halt to the commercial viability of biofuels. Since about 1930 the diesel engine has been fine-tuned to run on the diesel fraction of crude oil, which consists mainly of saturated hydrocarbons. As a result, modern diesel engines do not run satisfactorily on a pure vegetable oil feedstock because of problems of high viscosity, deposit formation in the injection system and poor cold-start 114

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problems. Pure rape oil can only be used in indirect injection (IDI) compression engines and very few diesel engines are now of this type. As petroleum has historically been in short supply, vegetable oils and their derivatives have been proposed as alternative diesel fuels during such emergency situations. The concept of using biomass-based fuels, specifically straight vegetable oils (SVOs) as diesel fuel alternatives, is particularly interesting and has been pursued on various occasions. Since 1930, the use of SVOs or their blends and derivatives, such as hydrocarbons obtained by thermal-catalytic cracking, and fatty acid esters (nowadays known as biodiesel) has been proposed. Edible refined soybean oil was used to power Japanese vessels in the Battle of Okinawa (1945). Coconut oil had also been used. During World War II various Indian vegetable fuel oils were also considered for diesel engines [3]. Pyrolysis of different triglycerides was also used for liquid fuel supply in different countries. For example, hydrocarbons were produced in China by a tung oil pyrolysis batch system and used as liquid fuels [4]; in another approach, vegetable oils were transesterified [5–7] and fatty acids were esterified [7]. Neat vegetable oils, such as babassu, coconut, castor seed and cottonseed were used in internal combustion engines in Brazil during the 1940s [8] or hydrocarbons produced by thermal-catalytic cracking [9]. Export of CSO, which was the main Brazilian vegetable oil at that time, was forbidden in order to force a drop in price and, thus, make possible its use as fuel in trains. Cottonseed oil was regarded as a strategic material as a substitute for imported diesel fuel [10]. Later, grapeseed oil was tested as a petroleum substitute. Quite recently, the Boungainville Revolutionary Army again used straight CNO. Since Diesel’s first experiments various other neat vegetable oils (mainly RSO, PMO, CNO) have been tested and used as diesel fuel alternatives [11–15]. All these fuels are non-toxic, renewable sources of energy, which do not contribute to the net global CO2 build-up. Direct use of renewable feedstocks, such as SVOs, in diesels may seem attractive (see Table 4.2), but there are risks. In fact, early tests already showed that using unmodified vegetable oils in diesel engines caused serious problems [16]. Vegetable oil sold for culinary purposes requires no stringent viscosity specification. Vehicles can be adapted to run on this sort of oil in unused or in waste form, though in the latter case filtration is necessary. Adaptations to make a modern diesel vehicle run reliably on SVO are fairly major. Vehicular use of SVO purchased for kitchen use is illegal in many countries, including the UK. Spent cooking oil from fast food outlets has been used to power vehicles with compression ignition engines. Some potential for serious usage of plant-derived waste cooking oils can be envisaged as the product is carbon neutral. R&D into the use of spent cooking oil as an automotive fuel is taking place in several countries (e.g. Greece and Spain).

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Fuel properties of oils and fats

Fuel-related properties of vegetable oils are listed in Table 4.1 [17]. The high kinematic viscosity (30–40 cSt at 311 K) is due to the high molecular mass (MW 600–900 Da), which greatly exceeds that of petrodiesel fuels. High viscosity is the main reason why neat vegetable oils have been largely abandoned as an alternative diesel oil. Viscosity increases with chain length (number of carbon atoms) and with increasing degree of saturation. Flash points are very high (above 473 K) and the volumetric heating values (39–40 MJ/kg) are low compared to diesel fuels (about 45 MJ/kg). Cetane numbers are also low whereas cloud and pour points are higher than those of diesel fuels. Vegetable oils can be used in diesel engines in a variety of forms. These comprise pure vegetable oil, blends with fossil diesel, methyl ester (FAME), FAME/petrodiesel blends and hydrotreated vegetable oil. Unfortunately, unmodified commercial vegetable oils are too viscous (10 to 20 times higher than No. 2 diesel fuels, up to 110 times for castor oil) to be compatible with modern direct-injection (DI) diesel fuel systems and engines. The injection, atomisation and combustion characteristics of vegetable oils as diesel fuels are significantly different from those of hydrocarbon-based diesel fuels. SVO-based fuel must be filtered to five microns and preheated to at least Table 4.1 Chemical and physical properties of vegetable oils and diesel Oil

Kinematic Cetane viscosity number at 310.8 K (mm2/s)

Babassu 30.3 Castora 297.0 Corn 34.9 Cottonseed 33.5 Crambe 53.6 Linseed 27.2 Palm 39.6 Peanut 39.6 Rapeseed 37.0 Safflower 31.3 H.O. Safflower 41.2 Sesame 35.5 Soybean 32.6 Sunflower 33.9 Tallowb 51.2 Diesel (No. 2 DF)a 2.7 a

38.0 – 37.6 41.8 44.6 34.6 42.0 41.8 37.6 41.3 49.1 40.2 37.9 37.1 – 47.0

Ref. [18]. Ref. [19]. Source: Ref. [17] unless otherwise stated. b

Heating value (MJ/kg)

Cloud point (K)

Pour Flash point (K) point (K)

– 39.5 39.5 39.5 40.5 39.3 – 39.8 39.7 39.5 39.5 39.3 39.6 39.6 40.0 45.3

293.0 – 271.9 274.7 283.0 274.7 304.0 285.8 269.1 291.3 261.8 269.1 269.1 280.2 – 258.0

– 241.3 233.0 258.0 261.8 258.0 – 266.3 241.3 266.3 252.4 263.6 260.8 258.0 – 240.0

423 533 550 507 547 514 540 544 519 533 566 536 527 547 474 325

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333 K before use in diesel engines. The engine technology required for this purpose is cost-effective only for large diesel aggregates used in ships or heavy lorries. For use in automobiles and smaller trucks, at present chemically altered vegetable oils are more economical. Ideally, seed oil that is minimally processed could be considered directly as a replacement for diesel without chemical modification, thereby significantly improving the economic status of this alternative fuel source. Many publications have discussed the performance of vegetable oils as fuels or fuel sources. Use of vegetable oils and their derivatives as fuels in compression ignition engines has been reviewed [20]. In general, it is not practical to substitute 100% vegetable oil (B100) for diesel fuel (DF), but blends of up to 20% VO and 80% DF are feasible to maintain total power without any alterations to the engine. Diesel engines for the agricultural and transport sector have been powered with fuel extenders based on sunflower oil (SNO) [21–24], soybean oil (SBO) [22, 25–27], canola oil (CO) [28], rapeseed oil (RSO) [11, 28], semirefined rapeseed oil (SRO) [29], cottonseed oil (CSO) [21, 26], palm oil (PMO) [30, 31], peanut oil (PNO) [26], Chinese tallow seed oil [32] and other vegetable oils [33, 34], including frying oil. Altin et al. [35] used preheated unprocessed SNO, CSO, CRO, SBO, RSO and opium poppy oil and concluded that, compared to mineral diesel fuel, little power loss occurred with the seed oils, but particulate emissions from vegetable oils were higher, and NO2 emissions were lower. Bernardo et al. [36] evaluated the stability of cold pressed and filtered Camelina sativa (cameline) seed oil as a fuel at typical diesel engine fuel operating temperatures. Cameline oil has been used as a bio-fuel in admixture with diesel oil without esterification [37]. Nut-sedge (Cyperus esculentus L.) tuber oil has a great potential as a biofuel. The oil is characterised by a very high phosphorus content (73 ppm) – far exceeding EN 14214 limits – and a very low peroxide value (6 meq/kg). Nut-sedge oil has lower cloud point and pour point temperatures than other vegetable oils. The calculated cetane number of nut-sedge oil (41.2) compares favourably with SBO (37.9), RSO (37.6) and SNO (37.1). A diesel engine using pure yellow nut-sedge tuber oil as fuel was operated near its rated power [38]. A mixture of nut-sedge oil and diesel fuel performed better than pure oil. Straight castor oil provides an economical source of a lubricity enhancing diesel fuel additive [39]. Various fractions obtained by refining crude oil obtained from Mesua ferrea L. seeds have been proposed as fuels for gasoline (fraction of the oil b. 310–473 K), for diesel engines (b. 473–573 K) and for steam and electric power generation (b. 573–618 K) [40]. Pongamia oil is being used in Karnataka (South India) to run generators for irrigation [41]. After residual decantation and filtration, pure Jatropha oil makes a suitable diesel substitute for various stationary engines (such as irrigation pumps, mills and generators) that are commonly used in African settings. The engines

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require only minor modifications. Jatropha oil also functions as a replacement for kerosene (for oil lamps and cooking stoves). Introduction of a sustainable and renewable Jatropha Energy System (JES) as a flexible, decentralised and localised energy option empowers rural African communities (Fig. 4.1) [42]. These efforts show that all the vegetable oils tested can be used as fuel with some reservations. The most detrimental properties of these oils are their high viscosity, low volatility, poor atomisation and autoxidation. Direct use of vegetable oils in diesel engines as an alternative renewable fuel competing with petroleum diesel has several advantages (Table 4.2). Full combustion of a fuel requires there to be sufficient stoichiometric oxygen. The combustion efficiency of vegetable oils is higher than that of diesel fuel because of the structural oxygen content. The main disadvantages of Jatropha village system

Nursery

Fertiliser

Services

Soap

Plantations

Seedcake

Seeds

Biocycle

Expeller

Raw oil

Services

Residuals

Filter

Extra oil

Electricity

Oil

Milling

Generator

Engine

Mill

Power area

Dispensary

Other services

4.1 Flow diagram of the Jatropha Energy System (after ref. [42]).

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Table 4.2 Main characteristics of straight vegetable oil as diesel fuel (after ref. [34]) Advantages: ∑ Liquid nature-portability ∑ Renewability ∑ High heat content ∑ Low sulphur content ∑ Low aromatic content ∑ Biodegradability Disadvantages: ∑ Higher viscosity (order of magnitude higher than petrofuel) ∑ Lower volatility ∑ Reactivity of unsaturated hydrocarbon chains ∑ Limited availability ∑ High cost (compared to petroleum-based diesel fuel) ∑ Non-regulated status

raw vegetable oils for diesel engines are higher viscosity, lower volatility, and reactivity of unsaturated hydrocarbon chains. Straight vegetable oils are non-tested and non-regulated fuels. Although diesel engines fueled with safflower oil were run for more than 700 h in Idaho, prolonged use of straight vegetable oils with their higher viscosity, lower cetane and volatility results in several short- and long-term problems with standard modern DI engines, including cold start, plugging of filters, knocking, poor fuel atomisation, excessive wear and lubricating oil thickening and gelling [43]. The build-up of carbon deposits is attributable to the large molecular size and resulting high viscosity of the medium- and long-chain triglycerides that constitute most commercial vegetable oils. Incomplete combustion, as evidenced by nozzle coking, engine deposits, ring sticking and contamination of crankcase lubricant may eventually result in significant decreases in engine performance, horse power and fuel economy, and may cause mechanical damage and increased exhaust emissions [44]. Use of unmodified oils or fats will also cause excessive fuel dilution of the engine oil (thus requiring frequent engine oil changes), which will eventually lead to a build-up of sludge in the engine oil and catastrophic engine failure [45]. Non-modified diesel engines can run for only up to a few hundred hours on plant oil without damage [46]. Using SVO as a fuel voids manufacturers’ warranties. Table 4.3 summarises the performance characteristics of vegetable oils as diesel fuels. The use of vegetable oil in diesel engines requires significant engine modification, including changing of piping and injector construction materials, otherwise engine running times are decreased, maintenance costs are increased due to higher wear, and the danger of engine failure is increased. Unlike biodiesel, in which the vegetable oil is adapted to the engine, the

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Table 4.3 Performance of vegetable oils as diesel fuels Fuel characteristics Consequence(s) Cetane number

Low cetane number implies long ignition delay Fuels with high autoignition temperatures are more likely to cause diesel knock

Distillation range

Presence of high-boiling components affects the degree of formation of solid combustion deposits Important to engine start- and warm-up

Combustion

Inefficient mixing of oil with air leads to incomplete combustion

Flash point

High flash point contributes to lower volatility characteristics

Viscosity

High viscosity interferes with injection process Poor fuel atomisation High viscosity/low volatility causes poor cold engine start-up and ignition delay

Cloud point, pour Fuel performance compromised under cold-temperature point, cold-filter conditions plugging point Carbon residue

Lower volatilisation characteristics lead to more deposit formation, carbonisation of injector strips, ring sticking and lubricating oil dilution and degradation

Oxidative stability Oxidative and thermal polymerisation cause deposition on injectors Long-term operation

Development of gumming, injector coking and ring sticking Serious engine deterioration

engine must be adapted to the fuel if pure vegetable oil is to be used. The use of native vegetable oils is only possible to a certain extent in conventional diesel engines. Only special engines or engines rebuilt for use with vegetable oil can use native vegetable oils in the long term without causing problems. Initially (until the 1940s) diesel engines were designed and developed to be dual-fuel engines, suitable for operation with vegetable oils. Diesel engines suitably modified according to the conditions of use and oil involved show a good performance when fueled with vegetable oils of different compositions and grades. In fact, cold pressed and filtered neat seed oils (in particular RSO) or even animal fats may be used in special or modified existing diesel engines [29, 47–50]. Their application as fuel substitutes for rugged indirect injection (IDI) diesel engines has been known since the first use of tractors [51], or for special engines like the Duotherm diesel engine designed by the German Elsbett Company [47]. The Elsbett engine is the only engine especially developed for successful use of vegetable oil. Engine conversion is recommended if using SVO. This conversion often includes installing a second fuel tank in order to be able to start and shut down on bio- or

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petrodiesel. Vegetable oil engines cannot usually comply with the increasingly strict exhaust gas regulations and have restricted winter capability. Diesel engines have also been modified to run on pure pyrolysis oil (BCOs) [52, 53]. The direct use of BCOs requires significant adaptations of technology to fuel characteristics and poses considerable challenges due to low pH, low cetane index, high ash content, viscosity, and operating temperature limitations compared with light fuel oil. BCO/diesel emulsions are expected to significantly reduce the need for these adaptations.

4.3

Low-viscosity formulations

Fats contain more saturated fatty acids and cannot be used as fuel in a diesel engine in their original form. Viscosity is an important factor in predicting the performance of potential alternative diesel fuel sources. Standard fuel specification ASTM D 975 for petrodiesel may be used to evaluate the suitability of fuel compositions for compression-ignition engines. The kinematic viscosity limits (at 313 K) of petrodiesel fuel, namely 1.9–4.1 mm2/s for DF2 (ASTM D 975) and 2.0–4.5 mm2/s for the European petrodiesel standard (EN 590), are lower than those of biodiesel. Direct use of vegetable oils and/or oil blends is generally considered to be unsatisfactory and impractical for both direct injection and indirect type diesel engines because of their relatively high kinematic viscosities and low volatilities. Various methods have been considered to gain sufficient engine compatibility for vegetable oil and animal fat-derived high-quality diesel fuels, including derivatisation (transesterification, hydrotreating, ozonation), pyrolysis/gasification, dilution, blending and microemulsification. It was not until vegetable oils were derivatised that low-viscosity biofuel became available. The process of transesterification (see Section 1.3.1 and Chapter 7) removes glycerol from the triglycerides and replaces it with an alcohol. The process decreases the viscosity but maintains the cetane number and heating value. By transesterification the viscosity of vegetable oils is reduced from about 10–15 times that of No. 2 diesel fuel to about twice that of No. 2 diesel for methyl esters, which is low enough to be used as diesel fuel. Other physical properties of FAME, such as cloud point and pour point, are considerably higher than No. 2 diesel fuel, which limits their use as an alternative to diesel fuel. However, up to 30 vol% of methyl esters in diesel fuel does not significantly change the cold-flow properties of the fuel [54]. Among the aforementioned primary technologies that may bring the viscosity to within specification for existing engines, only dilution, blending, microemulsification and heating do not chemically alter the feedstock. Blending of vegetable oils with other fuels may bring the viscosity to within a specification range. For blending purposes, intersolubility of the

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components is very important but pertinent data are rarely available [55, 56]. Dilution of oils with solvents and microemulsification of vegetable oils with immiscible liquids lowers the viscosity and mitigates some engine performance problems such as injector coking and carbon deposits. Dilution of vegetable oils can be accomplished with such materials as diesel fuels, a solvent or ethanol. By blending diesel fuel with plant oil up to 25%, the resulting viscosity is low enough to avoid special adaptations to the engine [57]. However, the problems of carbonisation and resulting engine troubles cannot be completely avoided. Mixing rape oil with diesel overcomes some of the problems connected to the viscosity and gumming properties of the vegetable oil in its use in direct injection engines. Although sunflower oil is completely miscible with diesel oil, the low CN value (30) creates cold-start problems. Blends of SNO or HOSFO with diesel fuels could not be recommended for long-term use. There have been reports on the use of unmodified oils in diesel engines (e.g. a CNO fuel blend [58]), although in one case the oils were just heated at 353 K to reduce the viscosity [35]. Also 40–50% of Jatropha oil can be substituted for diesel without the need for engine modification [59]. Results for various DF2 mixtures with CNO, J. curcas, PNO, RSO, SFO grades and SNO were recently reviewed by Dunn [60]. Vegetable oil/petrodiesel blends are generally not suitable for long-term fueling of direct injection diesel engines. Direct use of crude palm oil (CPO) is feasible in the Elsbett engine. A problem is clogging of the filter by impurities and hence the need to warm the fuel before combustion. However, the use of processed liquid palm oil (PLPO) directly or in blends, can overcome this problem, even in normal diesel engines. Palm oil in diesel changes the fuel’s physicochemical properties, including viscosity, cloud point, cetane number, heat value and boiling point. Blending of palm oil products (PLPO, RBDPO) with conventional diesel was evaluated at MPOB, Kuala Lumpur, as possible diesel substitutes for industrial and vehicle fuels. Several palm oil products can be used directly, without chemical modification, in conventional diesel engines as biofuel for industrial and transport purposes, notably CPO/MFO (1:1) (pour point 267 K), as well as refined, bleached and deodorised (RBD) palm oil and palm olein, RBDPO (as B5; pour point 282 K) and RBDPOo (as B10; pour point 288 K) as diesel extenders at tropical temperatures [61]. Palm oil or palm oil blended with diesel (50:50) or fuel oil have been successfully tested and used as fuel for power stations and diesel passenger cars. There is currently no biodiesel standard for vegetable oil/diesel blends. Both the European EN 14214 and US ASTM D 6751 standards on biodiesel are intended for methyl esters and, consequently, are not suitable for evaluation of PLPO/PD (petroleum diesel) blends. The Malaysian Standard for Diesel Fuel (MS 123:1993) has been applied as a close reference standard [62]. B2 and B5 of the PLPO/PD blends meet all the requirements of MS 123:1993.

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Various mixes of unesterified vegetable oil (CNO and PMO) blended with diesel oil or kerosene were introduced in recent years in Thailand under the name of ‘biodiesel’, even though most of them did not comply with the official standards for commercial use. Formulating hydrid diesel fuels by mixing with low molecular weight alcohols is another approach for reducing viscosity of vegetable oils. For that purpose the limited solubility of polar alcohols (except for scMeOH) in non-polar vegetable oils needs to be increased by addition of amphiphilic compounds. The formulation of hybrid diesel fuels by solubilisation (or equilibrium dispersion of an insoluble substance in a solvent under formation of a thermodynamically stable isotropic solution) of vegetable oil/shortchain alcohol mixtures through addition of amphiphilics is referred to as microemulsification [63]. Microemulsions (with droplet diameters ranging from 10 to 100 nm) can be made of vegetable oils with an ester and dispersant (co-solvent), or of vegetable oils, an alcohol and a surfactant, with or without diesel fuels, e.g. SBO, 95 wt% EtOH (E95) stabilised by n-BuOH [64] and 1.5 wt% H2O in triolein/2-octanol/MeOH [65]. Achievement of stable microemulsions at low temperature is difficult [66]. Dunn and Bagby [67] have described the low-temperature phase behaviour of solubilised SBO/ methanol mixtures. A microemulsion fuel of methanol with vegetable oils can perform nearly as well as diesel fuels. Blends can be formulated with cold-flow properties superior with respect to cloud point and comparable with respect to kinematic viscosity of methyl soyate (biodiesel). Similarly, various microemulsions of vegetable oils (e.g. SBO, SNO) with solvents such as lower alcohols (C1–C8) have been studied [68–72] as well as microemulsions of oil, diesel, water and a surfactant [73] to achieve better viscosities and spray patterns. Technology licensed to NGB (Baltimore, MD) enables production of a biofuel (diesel, heating oil) by emulsification of vegetable oils or animal fats, water and proprietary additives, with properties different from both biodiesel and SVO [74]. Scragg et al. [75] have proposed an emulsion of REE biodiesel/water/surfactant/microalgae (Chlorella vulgaris) (80:10:0.5:10) as a diesel fuel for industrial use despite the increased viscosity of the oil. However, not all engine performance problems could be solved using this fuel. The triglycerides present still lead to carbonisation. Hybrid diesel fuels may also be formulated by employing a co-solvent. Such formulations typically consist of vegetable oil/short-chain alcohol mixtures solubilised by a co-solvent. The co-solvent, consisting of a surfactant plus an amphiphilic compound, is added to solubilise otherwise nearly immiscible oil–alcohol mixtures into a single-layer (isotropic) solution. Co-solvent blending is a simple and flexible technology that reduces viscosity [64, 69]. Formulating vegetable oil/co-solvent blends requires no catalyst, consumes very little energy, and adapts readily to continuous processing. A problem

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is meeting the ASTM D 975 specification for minimum cetane number of 40. SBO/n-BuOH/E95 has a cetane number of only 25.1 [76]. Also the solubility of biodiesel fuel components in various fossil diesel fuel-alcohol-rapeseed oil alkyl ester systems was studied [56]. Whereas solubility of the pair RME-methanol is limited, solubility of fossil DF in RME and of RME in DF is not limited. Consequently, usage of DF-methanolRME mixtures for diesel fuels is not viable because of low solubility. Hybrid fuel formulations such as microemulsions or co-solvent blends are generally less expensive to prepare than biodiesel because of simple technology, merely consisting in mixing the components at room temperature. Several such formulations containing TGs in the absence of petrodiesel have been patented. Hybrid fuels formulated with TGs are susceptible to oxidative degradation. Hybrid diesel fuels formulated with short- or mediumchain alcohols also require special handling and storage considerations. The development of such alternative fuels from TGs is no longer actively being pursued. Most studies recommend against long-term use of vegetable oilbased hybrid diesel fuels [60]. If plant species were available that produce oil with high levels of shortand medium-chain triglycerides, transesterification before use as a diesel fuel substitute might be avoided. This would both lower the processing cost of the fuel and eliminate the production of the undesired glycerol by-product. Fuel properties (including heat capacity, viscosity, vapour pressure, surface tension and density) of tributyrin (C4:0), tricaproin (C6:0), tricaprylin (C8:0) and tricaprin (C10:0) indicate that these triglycerides are potential components in future diesel fuels derived from plant oils [77]. Because there are very few natural sources of these triglycerides, altering oil synthesis in plants may provide a method for increasing the SCT/MCT content. One problem with the direct use of such low molecular weight triacylglycerols is their poor cold-temperature flow properties. Cuphea oil tends to solidify. An interesting development is the genetic manipulation of Cuphea species (see Section 3.3). The viscosity of the mutant Cuphea oil falls between that of diesel fuel (DF2) and rapeseed oil. Fuel performance of the oil shows a marked improvement compared to that of unmodified commercial vegetable oils, approaching that of methyl esters [78]. Further work along these lines might result in development of a vegetable oil suitable as a neat biodiesel. Table 4.4 shows some of the considerable obstacles to straight vegetable oil biofuel technology. Future developments in engine construction may open new horizons for the use of native vegetable oils. However, because the market for users of SVO as a fuel is small (and limited anyway), there is no substantial economic incentive for engine manufacturers to pursue straight vegetable oils as a fuel. Use of SVO as a biofuel also requires setting of a standard for fuel quality and a quality assurance system in relation to product liability.

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Table 4.4 Future development of vegetable oil biofuel technology Advantages: ∑ No need for chemical transformation (transesterification, hydrotreatment, cracking) ∑ Renewable fuel source ∑ Green product ∑ No undesired by-products (glycerol) Requirements: ∑ Genetic manipulation of plant species ∑ Development of vegetable oil engines (viscosity, combustion properties, etc.) ∑ Development of standard for fuel quality ∑ Need for a quality assurance (product liability) ∑ Environmental friendliness (need for meeting increasingly strict exhaust gas emissions)

4.4

Bibliography

M.J.T. Reaney, P.B. Hertz and W.W. McCalley, Industrial and nonedible products from oils and fats, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 6 (F. Shahidi, ed.), Wiley-Interscience, Hoboken, NJ (2005), pp. 223–52. Union of Concerned Scientists, The Diesel Dilemma – Diesel’s Role in the Race for Clean Cars, Cambridge, MA (2004). C.R. Ferguson and A.T. Kirkpatrick, Internal Combustion Engines: Applied Thermosciences, John Wiley & Sons, Inc., New York, NY (2001). C. Song, C.S. Hsu and I. Mochida, Chemistry of Diesel Fuels, Taylor & Francis, New York, NY (2000). W.R. Nitske and C.M. Wilson, Rudolf Diesel, Pioneer of the Age of Power, University of Oklahoma Press, Norman, OK (1965).

4.5

References

[1] R. Diesel, Arbeitsverfahren und Ausführungsart für Verbrenn ungskraftmaschinen, Imp. germ. Pat. 67, 207 (28 Feb. 1892); see also Deutsches Museum, www.deutschesmuseum.de/ausstell/meister/e_diesel.htm. [2] W.R. Nitske and C.M. Wilson, Rudolf Diesel, Pioneer of the Age of Power, University of Oklahoma Press, Norman, OK (1965). [3] D.H. Chowhury, S.N. Mukerji, J.S. Aggarwal and L.C. Verman, Indian vegetable fuel oils for diesel engines, Gas Oil Power 37 (1942) 80–5. [4] C.C. Chang and S.W. Wan, China’s motor fuels from tung oil, I&EC Res. 39 (1947) 1543–8. [5] G. Chavanne, Procédé de transformation d’huiles végétales en vue de leur utilisation comme carburants, Belg. Pat. 422,877 (1937); C.A. 32:43132 (1938). [6] G. Chavanne, Sur un mode d’utilization possible d’huile de palme à la fabrication d’un carburant lourd, Bull. Agric. Congo Belge 10 (1942) 52–8; C.A. 38:21839 (1944).

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[7] G.I. Keim (to Colgate-Palmolive-Peet Co.), Treating fats and fatty oils, US Pat. 2,383,601 (28 Aug. 1945); C.A. 40:4617 (1946). [8] G.S.C. Barros, A.P Silva, L.A. Ponchio, L.R.A. Alves, M. Osaki and M. Cenamo, Custo de produção de biodiesel no Brasil, Rev. Polit. Agríc. 15(3) (2006) 36–50. [9] R.B. Otto, Gasolina derivada dos oleos vegetais, Bol. Div. Inst. Óleos 3 (1945) 91–9; C.A. 41:6690 f (1947). [10] Anon., Brazil uses vegetable oil for diesel fuel, Chem. Metall. Engng. 50 (1943) 225. [11] C.L. Peterson, D.L. Auld and R.A. Korus, Winter rape oil fuel for diesel engines: recovery and utilization, J. Am. Oil Chem. Soc. 60 (1983) 1579–87. [12] H. Masjuki, Rapid test to measure performance, emissions and wear of a diesel engine with palm oil diesel, J. Am. Oil Chem. Soc. 70 (1993) 1021–5. [13] T.W. Ryan III, L.G. Dodge and T.J. Callahan, The effects of vegetable oil properties on injection and combustion in two different diesel engines, J. Am. Oil Chem. Soc. 61 (1984) 1610–19. [14] H.T.C. Machacon, Y. Matsumoto, C. Ohkawara, S. Shiga, T. Karasawa and H. Nakamura, The effect of coconut oil and diesel fuel blends on diesel engine performance and exhaust emissions, J. SAE Rev. 22 (2001) 349–55. [15] A.W. Baker and R.L. Sweigert, Comparison of various vegetable oils as fuels for compression-ignition engines, Proceedings 19th Oil & Gas Power Mtg. of the ASME, Cleveland, OH (21–24 May 1947), pp. 40–8; Gas Oil Power, Ann. Tech. Rev. (1947), pp. 338–9. [16] J. Walton, Gas and Oil Power, Whitehall Press, London (1938). [17] A. Srivastava and R. Prasad, Triglycerides-based diesel fuels, Renew. Sustain. En. Revs. 4 (2000) 111–33. [18] C.E. Goering, A.W. Schwab, M.J. Daugherty, E.H. Pryde and A.J. Healkin, Fuel properties of eleven vegetable oils, Trans. ASAE 25 (1982) 1472–7. [19] Y. Ali, M.A. Hanna and S.L. Cuppett, Fuel properties of tallow and soybean oil esters, J. Am. Oil Chem. Soc. 72 (1995) 1557–64. [20] E.G. Shay, Diesel fuel from vegetable oils: status and opportunities, Biomass Bioen. 4 (1993) 227–42. [21] C.R. Engler and L.A. Johnson, Effects of processing and chemical characteristics of plant oils on performance of an indirect-injection diesel engine, J. Am. Oil Chem. Soc. 60 (1983) 1592–6. [22] M.L. Schlick, M.A. Hanna and J.L. Schinstock, Soybean and sunflower oil performances in a diesel engine, Trans. ASAE 31 (1988) 1345–9. [23] M. Ziejewski, H. Goettler and G.L. Pratt, Comparative analysis of the long-term performance of a diesel engine on vegetable oil based alternative fuels, SAE Tech. Paper Ser. 860301 (1986). [24] M. Ziejewski and K.R. Kaufman, Laboratory endurance test of a sunflower oil blend in a diesel engine, J. Am. Oil Chem. Soc. 60 (1983) 1567–73. [25] R.W. Pryor, M.A. Hanna, J.L. Schinstock and L.L. Bashford, Soybean oil fuel in a small diesel engine, Trans. ASAE 26 (1983) 333–7. [26] M.A. Mazed, J.D. Summer and D.G. Batchelder, Peanut, soybean, and cottonseed oil as diesel fuels, Trans. ASAE 28 (1985) 1375–7. [27] C. Adams, J.F. Peters, R.J. Rand, B.J. Schroer and M.C. Ziemke, Investigation of soybean oil as a diesel fuel extender: endurance tests II, J. Am. Oil Chem. Soc. 60 (1983) 1574–9. [28] R.C. Strayer, J.A. Blake and W.K. Craig, Canola and high erucic rapeseed oil

Vegetable oil formulations for utilisation as biofuels

127

as substitutes for diesel fuel: preliminary tests, J. Am. Oil Chem. Soc. 60 (1983) 1587–92. [29] K. McDonnell, S. Ward, J.J. Leahy and P. McNulty, Properties of rapeseed oil for use as a diesel fuel extender, J. Am. Oil Chem. Soc. 76 (1999) 539–43. [30] Y.M. Choo, A.N. Ma and Y. Basiron, Introduction and evaluation of palm oil methyl esters as diesel substitute, Elaeis Spec. Issue (1995), pp. 15–25. [31] A.J. Akor, W.J. Chanallor and N. Raubach, The potential of palm oil as motor fuel, Trans. ASAE 26 (1983) 23–8. [32] W.D. Samson, C.G. Vedrine and W.D. Robbins, Chinese tallow seed oil as a diesel fuel extender, Trans. ASAE 28 (1985) 1406–9. [33] C.L. Peterson, G.L. Wagner and D.L. Auld, Vegetable oil substitutes for diesel fuel, Trans. ASAE 26 (1983) 322–32. [34] E.H. Pryde, Vegetable oils as diesel fuels: overview, J. Am. Oil Chem. Soc. 60 (1983) 1557–8. [35] R. Altin, S. Çetinkaya and H.S. Yücesu, The potential of using vegetable oil fuels as fuel for diesel engines, En. Conv. Managm. 42 (2001) 529–38. [36] A. Bernardo, R. Howard-Hildige, A. O’Connell, R. Nichol, J. Ryan, B. Rice, E. Roche and J.J. Leahy, Camelina oil as a fuel for diesel transport engines, Ind. Crops Prod. 17 (2003) 191–7. [37] J. Zubr, Oil-seed crop: Camelina sativa, Ind. Crops Prod. 6 (1997) 113–19. [38] L. Nan, Z.C. Liang, R.X. Wan and J.X. Ma, Use of yellow nut-sedge oil as a substitute for diesel fuel, ASAE Paper No. MCR 84-108, St. Joseph, MI (1984). [39] D.P. Geller and J.W. Goodrum, Effects of specific fatty acid methyl esters on diesel fuel lubricity, Fuel 83 (2004) 2351–6. [40] D. Konwer and K. Baruah, Refining of the crude oil obtained from Mesua ferrea L. seeds, Chem. Ind. (London) (1984) 413–14. [41] U. Shrinivasa, A viable substitute for diesel in rural India, Curr. Sci. 80 (2001) 1483–4. [42] G. Venturini Del Greco and L. Rademakers, The Jatropha energy system: an integrated approach to decentralized and sustainable energy production at the village level; http://www.isf.lilik.it/files/jatropha/jes.pdf. [43] R.A. Korus, T.L. Mousetis and L. Lloyd, Polymerization of vegetable oils, in Proceedings Intl. Conf. Plant and Vegetable Oils as Fuels, ASAE Special Publ. SP 4-82 (1982), pp. 218–23. [44] H.J. Harwood, Oleochemicals as a fuel: mechanical and economic feasibility, J. Am. Oil Chem. Soc. 61 (1984) 315–24. [45] S. Howell, Working Position Paper by NBB in Non-Allowance of Unmodified Vegetable Oils or Animal Fats for Use in Diesel Engines, NBB, Jefferson City, MO (Feb. 2005). [46] G. Vellguth, Field test of DI-diesel tractor with methylester of rape oil as alternative fuel, in Proceedings Intl. Conf. Bioenergy (H. Egneus and A. Ellegard, eds), Elsevier, London (1984), Vol. IV: Bioenergy Utilisation, pp. 215–22. [47] K. Elsbett, L. Elsbett, G. Elsbett and M. Behrens, The duothermic combustion for direct injection diesel engines, SAE Tech. Paper Ser. 860310 (1986). [48] R. Howard-Hildige, S. Condon, J.J. Leahy and K.P. McDonnell, Emissions from two compression engined vehicles running on mineral and rapeseed oil based fuels, in Air Pollution III (H. Power, N. Moussiopoulos and C.A. Brebbia, eds), Computational Mechanics Publications, Southampton (1995), Vol. 2, pp. 381–5. [49] O.M.I. Nwafor and G. Rice, Performance of rapeseed oil blends in a diesel engine,

128

Biodiesel science and technology

Appl. En. 54 (1996) 345–54. [50] O.M.I. Nwafar, G. Rice and A.I. Ogbonna, Effect of advanced injection timing on the performance of rapeseed oil in diesel engines, Renew. En. 21 (2000) 433–44. [51] C. Meyer, R. Stern and J. C. Guibet, Esters from vegetable oils as substitutes for diesel fuels, in Proceedings VIII Intl. Symp. Alcohol Fuels, Tokyo (13–16 Nov. 1988), pp. 137–42. [52] S. Gros, Pyrolysis oil as diesel fuel, in Power Production from Biomass II, VTT Symposium 164, Espoo (1996), pp. 225–38. [53] Y. Iwamoto, K. Noma, O. Nakayama, T. Yamauchi and H. Ando, Development of gasoline direct injection engine, SAE Paper No. 970541 (1997). [54] R.O. Dunn and M.O. Bagby, Low-temperature properties of triglyceride-based diesel fuels: transesterified methyl esters and petroleum middle distillate/ester blends, J. Am. Oil Chem. Soc. 72 (1995) 895–904. [55] H. Zhou, H. Lu and B. Liang, Solubility of multicomponent systems in the biodiesel production by transesterification of Jatropha curcas L. oil with methanol, J. Chem. Engng. Data 51 (2006) 1130–5. [56] V. Makareviciene, E. Sendzikiene and P. Janulis, Solubility of multicomponent biodiesel fuel systems, Bioresour. Technol. 96 (2005) 611–16. [57] K.J. Leifert, Zukunftsperspektiven der Erzeugung und Verwendung von Pflanzenöl als Motortreibstoff in der EU, Verlag Lang, Frankfurt/M (1996). [58] H.T.C. Machacon, S. Shiga, T. Karasawa and H. Nakamura, Performance and emission characteristics of a diesel engine fueled with coconut oil-diesel fuel blend, Biomass Bioen. 20 (2001) 63–9. [59] K. Pramanik, Properties and use of Jatropha curcas oil and diesel fuel blends in compression ignition engine, Renew. En. 28 (2003) 239–48. [60] R.O. Dunn, Other alternative diesel fuels from vegetable oils, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 241–63. [61] A.A. Azhar, F.S. Mohd and M.A. Awang, Performance of palm oil-based biodiesel fuels in a single cylinder direct injection engine, Palm Oil Dev. 42 (June 2005) 15–27. [62] S.F. Cheng, Y.M. Choo, C.L. Yung, A.N. Ma and Y. Basiron, Palm biodiesel: gearing towards Malaysian biodiesel standards, Palm Oil Dev. 42 (June 2005) 28–34. [63] A.W. Schwab, M.O. Bagby and B. Freedman, Preparation and properties of diesel fuels from vegetable oils, Fuel 66 (1987) 1372–8. [64] A.W. Schwab, H.C. Nielson, D.D. Brooks and E.H. Pryde, Triglyceride/aqueous ethanol/1-butanol microemulsions, J. Disp. Sci. Technol. 4 (1983) 1–17. [65] A.W. Schwab and E.H. Pryde, Triglyceride-methanol microemulsions, J. Disp. Sci. Technol. 6 (1985) 563–74. [66] M. Mittelbach, Herstellung von Fettsäuremethylestern und deren Verwendung als Dieselkraftstoff, Österr. Chem. Ztschr. 90 (1989) 147–50. [67] R.O. Dunn and M.O. Bagby, Low-temperature phase behavior of vegetable oil/ co-solvent blends as alternative diesel fuel, J. Am. Oil Chem. Soc. 77 (2000) 1315–23. [68] C.E. Goering, R.N. Campion, A.W. Schwab and E.H. Pryde, Evaluation of soybean oil-aqueous ethanol microemulsions for diesel engines, in Proceedings Intl. Conf. Plant and Vegetable Oils as Fuels, ASAE Special Publ. SP 4–82 (1982), pp. 279–86. [69] C.E. Goering and B. Fry, Engine durability screening test of a diesel oil/soy oil/ alcohol microemulsion fuel, J. Am. Oil Chem. Soc. 61 (1984) 1627–32. [70] Z. Ji, Method for producing microemulsified fuel, Faming Zhuanli Shenqing Gongkai

Vegetable oil formulations for utilisation as biofuels

129

Shuomingshu (2005), C.A. 144:131591 (2005). [71] M. Ziejewski, K.R. Kaufman, A.W. Schwab and E.H. Pryde, Diesel engine evaluation of a nonionic sunflower oil-aqueous ethanol microemulsion, J. Am. Oil Chem. Soc. 61 (1984) 1620–6. [72] Z. Ji, Method for producing microemulsified fuel, Chin. Pat. 1,632,067 (29 June 2005). [73] T.N. de Castro Dantas, A.C. da Silva and A.A.D. Neto, New microemulsion systems using diesel and vegetable oils, Fuel 80 (2001) 75–81. [74] F. Petnucci and A. Festuccia, Biofuel composition and method of producing a biofuel, PCT Int. Publ. No. WO 2007/127059 A2 (8 Nov. 2007). [75] A.H. Scragg, J. Morrison and S.W. Shales, The use of a fuel containing Chlorella vulgaris in a diesel engine, Enzyme Microb. Technol. 33 (2003) 884–9. [76] C.E. Goering, A.W. Schwab, R.M. Campion and E.H. Pryde, Soyoil-ethanol microemulsions as diesel fuel, Trans. ASAE 26 (1983) 1602–4, 1607. [77] J.W. Goodrum and M.A. Eiteman, Physical properties of low molecular weight triglycerides for the development of biodiesel fuel models, Bioresour. Technol. 56 (1996) 55–60. [78] D.P. Geller, J.W. Goodrum and S.J. Knapp, Fuel properties of oil from genetically altered Cuphea viscosissima, Ind. Crops Prod. 9 (1999) 85–91.

5

Feedstocks for biodiesel production

Abstract: Globally dominating feedstocks for biodiesel production nowadays are mainly rapeseed, soybean, sunflower and palm oils; animal fats (tallow) and recycled frying oils are minor contributors. This chapter describes the main characteristics of the major and minor first-generation foodstocks for biodiesel production and the short- to medium-term prospects of secondgeneration, non-edible feedstocks (in particular Jatropha and algae) and various highly acidic, low-quality oils for the same purpose. Biodiesel outlooks are differing geographically as a result of the prevailing agronomic and climatic conditions. Important developments can be observed in various parts of the world. Key words: Biodiesel resources; main energy crops; first-generation foodstocks; non-edible oilseeds; second-generation feedstocks.

5.1

Introduction

Potential renewable raw materials for biodiesel production are edible and non-edible vegetable oils, animal fats and oils, recycled or waste oils, by-products of the edible oil and dairy industries, and other saturated and unsaturated fatty acids varying in carbon chain length and degree of unsaturation. Selection criteria of vegetable oils are: availability, cost, oil quality (composition) and product shelf-life. Unlike fossil reserves, different regions of the world have their own vegetable oil resources that could be exploited for biodiesel production. Oil crops dominating the early (1998) feedstock sources for biodiesel were rapeseed oil (RSO, 84%), sunflower seed oil (SNO, 13%), soybean oil (SBO, 1%), palm oil (PMO, 1%) and other oils (including Jatropha oil, beef tallow and recycled frying oils, 1%) [1, 2]. With increasing biodiesel production in the US, South America and Asia, the shares of SBO and PMO have increased rapidly. Table 5.1 shows the fatty acid profiles and other relevant chemical data in relation to biodiesel manufacture from common vegetable oil and animal fat raw materials. For fatty acid compositions of other (non)edible oils and fats, recycled and waste oils can be used as raw materials in biodiesel production (see also refs. [3, 4]). Quality indicators of raw materials comprise acid value, anisidine value, oil content, free fatty acid (FFA) content, moisture content, saponification value, unsaponifiable matter, P content, and the composition of fatty acids according to standard methods [5]. Unlike FFA content, which is a measure of free fatty acids present in a fat or oil, acid 130

Table 5.1 (a) Fatty acid profiles of common vegetable oils and animal fats (b) Other chemical properties of common vegetable oils and animal fats (a)

B. campestris B. carinataa Canola Cardoon Castorb Coconutc Coriander Corn (maize) Cottonseed Crambe Jatropha Karanja Kenaf Linseed Mahuad Olive African palm Palm kernele Palm oleine Palm stearin Peanut Poppy seed Pumpkin seed Rapeseed (LE)f

0.0

0.0

0.0

1.9–2.8

0.6–2.9 1.0–3.5

12.3–16.3 12.0–15.8 7.2–9.9

0.6–2.4 3.5–6.0 0.6–2.1 45.0–52.5 0.5–0.8

0.0

0.0 0.0 0.0 0.0 14.0–21.0 0.0 0.0

0.0 0.0 0.0 0.0 41.5–53.2 0.0 0.0

0.0 0.0 0.0 0.0 16.0–21.0 0.1 0.5–2.0

2.4–3.1 4.0–5.6 11.0–14.0 0.9–1.4 6.0–11.3 3.8–5.4 10.0–12.0

0.0 0.0 0.0 0.0 0.0 0.1 0.1–1.5

1.0–2.0 2.4 3.0–3.6 0.9–1.0 1.5–4.2 0.4 1.6–4.5

9.7–17.0 60.0–75.0 25.0–30.0 2.6–3.7 4.0–8.7 74.9–76.3l 20.0–32.5

16.8–25.0 12.0–23.4 54.0–60.0 4.1–4.9 0.8–2.6 16.6–18.6 52.0–62.0

10.0–16.6 3.2–9.1 < 1.0 0.3–0.4 0.0 0.2 0.5–1.7

0.7 0.5–1.3 0.5 0.2 0.1 0.1 0.2–1.0

5.0–8.2 < 0.5 0.0 0.0 0.0 0.1 0.2–0.6

0.0 0.0 0.8 2.1 0.0 0.1 0.1–0.5

33.0–46.5 < 2.0 < 1.0 0.0 0.0 0.1 0.1–0.3

0.0 0.0 0.0 0.0 0.0 0.1 0.1–0.5

<2.0 0.0 0.0 0.0 0.0 0.1 0.0

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.1–0.2 0.0 0.0 0.0 0.5 0.0 0.0 0.0 0.1–0.5

0.7–1.4 0.0 0.1–1.4 0.0 0.5 < 0.1 0.0 0.4–1.2 0.6–2.4

17.0–31.0 1.8–2.2 12.8–17.7 3.7–7.9 20.1 4.0–7.0 16.0–28.2 6.9–15.6 32.3–47.9

0.4–2.0 0.0 0.0–1.3 0.0 1.6 0.1 0.0 0.5–1.1 0.2–1.4

0.9–4.0 0.7–0.9 3.7–9.8 2.4–8.9 3.2 2.0–5.0 20.0–25.1 1.4–4.4 3.7–6.3

13.3–22.9 15.9–18.8 37.8–45.8 44.5–71.3 29.2 18.0–24.0 37.0–51.0 62.8–84.4 37.0–52.4

47.8–58.2 8.7–9.3 29.0–45.0 10.8–18.3 45.9 14.0–19.0 8.9–14.3 3.0–20.2 6.4–12.5

0.1–2.1 4.8–8.7 0.0–0.3 0.0 0.7 50.0–58.0 0.0 0.5–4.0 0.2–0.6

0.2–1.3 1.0–2.0 0.1–0.3 0.0 0.5 0.1 0.0–3.3 0.1–0.6 0.1–1.0

0.1–0.5 0.0–4.7 0.0 0.0 0.2 0.3–0.4 0.3–0.4 0.2–0.4 0.1–0.4

0.1–0.6 0.8–2.0 0.2 0.0 0.3 0.2 0.1–0.2 0.1–0.2 < 0.2

0.1–0.3 56.2–62.5 0.0 0.0 0.7 0.0 0.0 0.0 0.0

0.1 0.7–1.1 0.0 1.1–3.5 0.1 0.0 0.0 0.4 0.0

0.0 1.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.2

1.3–8.0

8.7–21.0

0.5–3.5

0.2

0.2

0.2

0.2

0.0

0.0

0.0

0.1–0.6 0.1–0.5

0.0–0.6 0.4 1.0 0.4

0.2 0.2

0.0 0.0

0.0 0.0

0.0 0.0

5.1–13.0 42.4–55.0 12.0–19.0 3.0–11.4 0.0 0.0

0.1–0.5 0.1–0.5

0.5–1.5 1.0–2.0

38.0–44.3 0.2–0.6 3.5–5.0 48.0–74.1 0.2 3.9–6.0

37.9–46.0 9.0–13.5 15.5–36.0 3.0–10.0

0.0 0.0 0.0

0.0 0.0 0.0

0.0 < 0.1 0.1

8.0–12.6 1.4 6.0–12.0 0.2 11.8–12.0 0.0

1.0–4.5 1.0–2.3 6.6–6.9

41.0–56.0 26.0–31.9 0.9 15.6–22.0 60.0–76.0 0.1–0.6 33.7 46.5 0.2–1.9

0.8–4.2 0.6–2.6 1.5–5.4 0.0 0.1 0.0 0.0 0.0 0.5 0.0 0.1 0.0

0.5–2.5 0.0 0.0

1.0 0.0 0.0

0.0

0.0

0.0–0.5

3.0–5.7

0.8–1.5

55.0–64.4 20.0–26.0 8.2–12.0

0.0

0.0

0.0

0.0

1.0–2.0 0.5

0.5–2.0

131

Fatty acid profilek, % by weight ——————————————————————————————————————————————————————————————————————— £ 10 12:0 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 22:0 22:1 24:0 24:1

Feedstocks for biodiesel production

Oil and fat source

Fatty acid profilek, % by weight ————————————————————————————————————————————————————————————————————————— £ 10 12:0 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 22:0 22:1 24:0 24:1

Rice bran 0.0 0.0 0.3–1.0 12.0–22.1 0.2–0.4 0.8–3.0 38.9–50.0 29.4–35.2 0.4–1.1 0.5–1.2 Safflower 0.0 0.0 0.0–0.1 5.2–9.0 0.0 1.0–3.0 10.0–16.2 76.3–82.0 0.1–0.4 0.0 Safflower 0.0 0.0 0.0 4.8 0.0 2.0 77.4–79.0 13.0–13.8 0.5 0.6 (HO)g Sesame 0.0 0.0 0.0 7.8–13.0 0.1 3.7–7.0 36.8–53.0 35.0–53.0 0.3 0.4–0.6 Soybean 0.0 0.1 0.1–0.4 7.0–12.7 0.1–1.0 1.4–5.9 11.5–27.2 51.5–63.1 2.9–12.1 0.3–4.0 Soybean 0.0 0.0 0.0 5.4 0.0 4.1 81.3 3.8 5.3 0.0 (HO) Soybean 0.0 0.0 0.0 4.3–11.1 0.0 3.5–5.0 43.7–55.0 24.0–35.5 < 3.1 0.6 (MO) Soybean 0.0 0.0 0.0 17.2 0.0 4.4 15.7 55.6 7.1 0.0 soapstock Sunflower 0.0 0.1 0.1–0.2 2.0–9.0 0.3 1.6–6.5 14.0–39.4 48.3–74.0 0.2–0.7 0.1–1.2 Sunflower 0.0 0.0 0.4–0.8 4.0–5.5 0.1 2.1–5.0 43.1–71.8 18.7–45.3 0.1–0.7 0.2–2.9 (MO)h Sunflower 0.0 0.0 0.1 2.6–5.9 0.1 2.8–6.2 75.0–90.7 2.1–17.0 0.1–0.3 0.2–0.5 (HO)i Tung 0.0 0.0 0.0 1.0–3.0 0.0 1.0–3.0 4.0–9.0 8.0–10.0 78.0 0.0 –89.0m Jojoba 0.0 0.0 0.0 1.1–1.9 0.1–0.3 < 0.1 10.1–12.2 0.2 0.1 0.1–0.4 oil–waxj Beef tallow 0.0 0.1–0.7 2.0–8.0 23.0–38.0 0.0–4.7 14.0–29.0 34.9–50.0 1.0–5.0 0.5 0.1 Brown 0.0 0.0 1.7 22.8 3.1 12.5 42.4 12.1 0.8 0.0 grease Lard 0.0 0.1 1.4–2.3 17.3–30.0 1.9–3.0 12.0–20.0 42.5–50.0 7.0–13.0 0.4–1.0 0.3 Poultry fat 0.0 0.0 0.0–0.5 22.2–23.0 8.4 5.1–5.4 42.3 17.0–19.3 1.0 0.0 White 0.0 0.0 0.0 23.3 3.5 11.0 47.1 11.0 1.0 0.0 grease Yellow 0.0 0.0 2.4 23.2 3.8 13.0 44.3 7.0 0.7 0.0 grease

0.0 0.0 0.0

< 1.0 0.0 0.0

0.0 0.0 0.0

0.4 0.0 0.0

<1.0 0.0 0.0

0.2 0.1 0.0 0.1–0.4 0.1–0.8 0.4 0.0 0.0 0.0

0.1 0.0 0.0

0.0 0.0 0.0

0.0

0.9

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.4 0.3–1.5 0.3 0.2–0.3 0.6–6.8 0.0

0.5 0.3–0.4

0.0 0.0

0.1–0.5 0.5–2.0 0.3

0.5

0.0

0.0

0.0

0.0

0.0

0.0

63.5– 0.5 12.7–18.9 0.0 73.9 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

0.9– 1.9 0.0 0.0

1.5 0.0 1.0–2.0 0.0 0.0 0.0

0.0 0.0 0.0

0.0 0.0 0.0

0.0 0.0 0.0

0.0

0.0

0.0

0.0

0.0

Biodiesel science and technology

Oil and fat source

132

Table 5.1 Continued

a

Ethiopian mustard. Contains 87–88% of ricinoleic acid. Contains < 4% FFAs. d Contains about 19% FFAs. e Fractionated product from palm oil. f Zero–zero. g High–oleic safflower. h Mid–oleic sunflower, NuSun. i High–oleic sunflower. j Contains about 59% of fatty acid esters and 41% of fatty alcohols. k Acids: Caproic, caprylic, capric (< 10); Lauric(12:0); Myristic (14:0); Palmitic (16:0); Palmitoleic (16:1); Stearic (18:0); Oleic (18:1); Linoleic (18:2); Linolenic (18:3); Arachidic (20:0); Gadoleic (20:1); Behenic (22:0); Erucic (22:1); Lignoceric (24:0); Methyl 15 – tetracosenoate (24:1). l Petroselinic acid (68.8%) + oleic acid (7.5%). m Linolenic acid (C18:3) 1–3 wt%; a-eleostearic acid (C18–3c) 77–86 wt%. b c

Feedstocks for biodiesel production 133

134

Biodiesel science and technology

Table 5.1 Continued (b) Phosl Peroxm Iodine ppm value number

SFAn %

MUFAn PUFAn % %

B. campestris 1052 0.8–0.98 92–130 B. carinataa Canola 883 0.15 18 100–127 Cardoon 879 118–125 921 < 2.0 82–88 Castorb 638 0.30 6–17 Coconutc Coriander Corn (maize) 871 0.11 7 18.4 109–140 Cottonseed 858 0.07 8 64.8 90–117 Crambe 0.36 12 26.5 85–93 Jatropha 0.1–0.35 < 10 92–110 Karanja Kenaf Linseed 873 170–211 55–70 Mahuad Olive 868 0.5–0.8 53.0 78–94 African palm 847 6.9 51–58 0.28 12–19.7 Palm kernele 50–52 Palm oleine Palm stearin < 48 Peanut 0.20 9 82.7 73–107 Poppy seed < 0.2 < 5.0 140–158 Pumpkin seed < 0.1 < 0.1 1–3 30.2 96–121 Rapeseed (LE)f Rice bran Safflower 126–150 80–100 Safflower (HO)g Sesame 82–120 Soybean 0.1 < 1 44.5 121–143 Soybean (HO) 90.0 Soybean (MO) 107.0 Soybean soapstock Sunflower 883 0.15–0.6 15 2.9–10.7 118–141 882 94–122 Sunflower (MO)h 78–90 Sunflower (HO)i Tung 160–175 0.32 0.4 81–89 Jojoba oil–waxj Beef tallow 15.4 35–48 Brown grease Lard 55–71 Poultry fat 3.7 75–85 White grease Yellow grease 8.0 2 90

8.0 5.0 7.0 16.0 2.7 92.0 5.5 15.0 29.0 6.5 22.0 15.8 24.5 10.0 44.5 14.0 47.0 84.5 45.0 68.0 19.0 11.0 19.4 5.5 20.0 8.0 7.0 15.0 16.0 9.5 17.5 21.6

70.0 20.0 69.0 26.0 92.5o 6.0 76.5 26.0 19.0 78.5 41.0 66.6 30.5 20.0 44.5 71.0 44.0 15.0 43.0 26.0 51.0 18.0 33.8 62.0 44.5 13.0 78.0 43.0 21.0 81.5 43.5 15.7

22.0 75.0 24.0 58.0 4.8 2.0 18.0 59.0 52.0 15.0 37.0 16.7 45.0 70.0 11.0 15.0 9.0 0.5 12.0 6.0 30.0 71.0 46.8 32.5 35.5 79.0 15.0 42.0 63.0 9.0 39.0 62.7

11.5 14.0 10.0 4.0 2.3 55.0 39.0 40.0 28.2 36.5 40.0

27.0 53.5 81.0 6.0 97.5 42.5 48.0 49.5 52.3 51.0 51.0

61.5 32.5 9.0 90.0 0.2 2.5 13.0 10.5 19.5 12.5 9.0

Oil and fat source

a–j

Mean MW (g/mol)

Acidk value

Cf. Table 5.1(a). Acid values are mg KOH necessary to neutralise FFA in 1 g of oil sample. l Phosphatide (gum) content varies in direct proportion to phosphorus value. m Peroxide values are meq. peroxide per 1000 g of oil sample, which oxidise KI under test conditions. n Average values. o Including ricinoleic acid (12-hydroxyoleic acid). k

Feedstocks for biodiesel production

135

value is a measure of total acidity of the lipid, involving contributions from all the constituent fatty acids that make up the glyceride molecule. The fatty acids are the most important constituents of the raw material and the acid profile largely determines the properties and uses of the oil. The fatty acid composition gives the degree of (un)saturation of the product. In palm and coconut oil and beef tallow the saturated fatty acid component accounts for some 50% or more of the total fatty acids.

5.2

Global oilseed and oil production

Worldwide, 1 billion tons of diesel fuel are consumed annually. The total feedstocks available for biodiesel production do not exceed some 12% of diesel fuel use [6], unless oil yields and oilseed production are increased. Worldwide oil crop production amounted to 662 Mt in 2005 (Table 5.2), with a European production of 31 Mt (Table 5.3) or 8.5 Mt of vegetable oil (corresponding to 7% of world production). Recent estimates (1 Aug. 2007) of the total global production of three major oilseed plants (soybean, rapeseed, sunflower; sum) amount to (235.0, 47.2, 29.8; 312.0 MMT), (221.0, 50.8, 29.4; 301.2 MMT) and (231.0, 52.1, 29.6; 312.7 MMT) for 2006/07, 2007/08 and 2008/09, respectively [7]. In 2008/09 worldwide consumption of the major oilseeds is expected to be just under the expected production. Soybeans, wheat and corn compete for acres: the US has recently witnessed extensive switching of plantings from soybeans to corn for ethanol production (sec Section 14.6.3). Oil fruits (such as palm, olive, argan and avocado) represent an alternative source of oil to oilseeds and, moreover, they have the advantages of a higher oil yield per hectare and lower oil extraction costs. Tables 5.4–5.6 show some global production and consumption figures of vegetable oils and fats with growth forecast until 2020. Estimated total production in 2020 is 194 Mt, 68% being on account of PMO, SBO, RSO and SNO. In the past five years (2002–07) the world vegetable oil production rose by 31 Mt, mainly on account of palm (+11 Mt), canola and sunflower (+7 Mt each) and soya (+ 6 Mt). With growth by about 5.2 Mt/yr since 1997 the global edible oil production is now estimated as 112.0 Mt for the major four oils (SBO, PMO, SNO, RSO) and 127.1 Mt (including also CSO, PNO, PKO, CNO) by 2007/08 [7]. World production of the main vegetable oils and animal fats (17 commodities) amounted to 153 Mt (2006/07). Production of palm oil is increasing most rapidly, from a modest 7.9% share in 1980 to 19.0% by 2000, with highest growth figures until 2020, thus classifying it as the main oil crop. Rapeseed oil is now available in greater quantities than sunflower oil. About 75% of edible vegetable oils is extracted from the endosperm of oilseeds, like soybean and oilseed rape, whereas the remaining 25% is produced from the pericarp of oil fruits, such as oil palm, olive and avocado. The global production of oilseeds is expanding with advances in

136

Biodiesel science and technology

Table 5.2 Worldwide crop production in 2005. Crops are listed in order of production volumes Oilcrop

World production (kton)

Top 3 producers (% of total)

Soybean Oil palm fruit Coconut Rape/mustard Cottonseed Groundnut Oil palm Sunflower Olive Palm kernel Sesame Linseed Oilseeds variousa Castor Tallow tree Safflower Sheanut Melon Tung nut Kapok fruit Poppy seed Hempseed Jojoba

209 532 173 261 55 037 46 572 41 132 36 492 32 814 30 674 14 512 8771 3321 2711 1892 1394 870 773 693 587 516 393 60 32 0.4

USA, Brazil, Argentina (81.8%) Malaysia, Indonesia, Nigeria (85.8%) Indonesia, Philippines, India (73.2%) China, Canada, Germany (53.1%) China, USA, India (63.6%) China, India, Nigeria (66.0%)

Total

662 039

Russia, Ukraine, Argentina (46.7%) Italy, Spain, Greece (69.1%) China, India, Myanmar (58.9%) Canada, China, USA (72.4%) India, China, Brazil (94.3%) China India (n.g.), USA, Mexico Nigera, Cameroon, Sudan (76.5%) China, Paraguay, Argentina (99.0%) Czech Republic, Turkey, France (82.3%) China, France, Chile (96.6%)

a

Includes: Beech nut, Fagus sylvatica; Candle nut, Aleurites moluccana; Crabwood, Carapa guineensis; Croton seed, Croton tiglium; Mowrah buttertree, Bassia latifolia; Nigerseed, Guizotia abyssinica; Oiticica, Licania rigida; Perilla seed, Perilla frutescens; Physic nut, Jatropha curcas; Sal fat, Shorea robusta; Karanja, Pongamia glabra; Black palm nut, Astrocaryum spp. Source: FAOSTAT data (2006).

technology and expansion in acreage. However, if RSO and SBO producing countries could achieve production levels similar to those using most advanced farming practices, some 23 Mt of additional vegetable oil could be generated without taking new acres into production. World demand for vegetable oils has been expanding at about 6 Mt/yr (4 Mt/yr for edible oils and 2 Mt/yr for biofuel), albeit most recently at a lower pace. About 80% of the whole range of oils and fats is now being used as human food, 6% for animal feed and 14% provides the basis of the oleochemical industry (in the widest sense: soaps, detergents, toiletries, cosmetics, surfactants, emulsifiers, perfumes, solvents and biofuels). At present the world’s largest sources of vegetable oils are palm oil (31.0%), soybean oil (29.2%), rapeseed oil/canola (14.6%) and sunflower oil (8.5%). There is not enough of such oils to supply the world’s total oil needs. Consequently, there is a limited availability of surplus oil and fat resources.

Feedstocks for biodiesel production

137

Table 5.3 Oil crops under cultivation in Europe 2005 Oil crop

EU25 (kton)

% World production

Rape/mustard Olive Sunflower Soybean Cottonseed Oilseeds variousa Linseed Poppy seed Melon Hempseed Groundnuts Sesame Safflower

15 019 10 354 3898 921 765 212 179 41 5 5 4 2 0.7

32.7% 71.4% 12.7% 0.4% 1.9% 11.2% 6.6% 68.0% 0.9% 15.1% 0.1% 0.1% 0.1%

Total

31 407

a

See Table 5.2. Source: FAOSTAT data (2006).

Table 5.4 Global production of vegetable oils (2006/07) Source Bio–oil Mt

Source Bio–oil

Mt

Palm Soybean Rapeseed Sunflower Peanut

Cottonseed Palm kernel Coconut Olive Total

4.70 4.48 3.26 2.85 120.53

37.37 35.19 17.64 10.18 4.86

Source: USDA.

5.3

Resources for biodiesel production

There are more than 350 oil-bearing plants identified (with thousands of sub-species) that could be used to grow a new crop of fuel every year. The productivity of perennials is higher, they avoid erosion and can also be cultivated in mountain areas. Some species can be harvested more than once a year. Many oleaginous plant species produce more oil in tropical climates and conditions. The fuel potentialities of many vegetable oils (including castor, grapeseed, maize, camelina, pumpkinseed, beechnut, rapeseed, lupin, pea, poppyseed, peanut, hemp, linseed, chestnut, sunflower seed, palm, olive, soybean, cottonseed, shea butter) were considered as early as 1939 [8]. A shift from annual energy crops, which need to be replanted and harvested every year, to perennial crops (e.g. palm, Jatropha) is observed. Raw materials for modern biodiesel production were outlined recently [9]. Table 5.7 shows a selection of suitable biodiesel feedstocks, at present mainly RSO, SNO, SBO and PMO. New sources are HOSNO, rapeseed varieties

138

Biodiesel science and technology

Table 5.5 Vegetable oil production, consumption and imports for top consuming markets (2003/04) Country Total oil productiona (kton)

Total oil Total oil consumption imports (kton) (kton)

Brazil 12 118 (SBO, CSO) 6886 244 P.R. China 11 959 (RSO, SBO, SFO, CSO, PNO) 18 964 7141 EU25 11 268 (RSO, SFO, OO) 15 474 5622 India 6835 (CNO, PNO, CSO, SBO, 11 258 4515 RSO, SFO) Indonesia 13 791 (PMO, CNO, PKO) 4861 82 Malaysia 15 118 (PMO, PKO) 3286 1101 Pakistan 643 (CSO) 1939 1347 Russian 1729 (SFO) 2254 654 Federation USA 8768 (SBO) 10 029 1910 World 101 696 100 337 37 268

(PMO, SBO) (PMO, SFO) (PMO, SBO)

(PMO, SBO) (PMO, SBO) (RSO, PMO) (PMO, SBO, SFO, RSO)

a

Production is oil processed from domestic and/or imported oilseeds. Animal fats are not included. Source: Official Statistics, USDA.

(HO, LL) and linola (LL). RSO(00) and HOSNO are currently considered to be the best candidates to substitute for conventional petrol-based lubricating oils. Promising non-food sources are Jatropha, algae, castor beans, camelina, karanja, acrocomia palm, babassu, buriti and dendê. The hope is that nonfood oils will be available in the future in sufficiently large, cost-effective volumes. Generally, factors such as geography, climate and economics determine which vegetable oil has the highest potential use in biodiesel fuel. Raw materials considered for biodiesel production are country/region specific, e.g. EU: RSO, SNO; US: SBO, CSO; Canada: CO; Nicaragua: Jatropha curcas, PMO; Japan: recycled VOs; India, P.R. China: Jatropha curcas; South-East Asia: PMO, RBO; Philippines: CNO. In fact, the specification of oil quality used for biodiesel varies between the US (soydiesel) and Europe (rapediesel) (see also Chapter 12). Whereas the US still concentrates on ‘soydiesel’ (from 90% of biodiesel virgin oil feedstock in 2001 to 45% soy, 39% multi-feedstock, 3% animal fats/soy, 3% animal fats, 4% canola and 6% other in 2007), US biodiesel production could be further diversified to include rapeseed, yellow mustard, corn, sunflower, peanut, coconut, Jatropha, cooking oil and yellow grease. The contribution of used frying oil to the total necessary biodiesel production is small (even in the US) and limited by the use of virgin oil for cooking. Waste vegetable oils (WVOs) discarded by Japanese restaurants, food manufacturing industries and general households amount to 400 kt/yr and constitute a valuable resource. Moreover,

Table 5.6 World oils and fats production (Mt) Year



1980

1990

2000

2010(f)

2020(f)

Palm Soybean Rapeseed Sunflower World

4.59 (7.9%) 13.42 (23.1%) 3.48 (6.0%) 4.98 (8.6%) 58.04

11.03 (13.7%) 16.14 (20.0%) 8.18 (10.1%) 7.80 (9.6%) 80.77

21.73 (19.0%) 25.48 (22.3%) 14.24 (12.4%) 9.63 (8.4%) 114.51

35.10 (22.9%) 37.50 (24.5%) 20.70 (13.5%) 10.98 (7.1%) 153.30

49.42 (25.4%) 41.39 (21.3%) 25.15 (12.9%) 17.49 (9.0%) 194.43

Source: Malaysian Palm Oil Board (2001). f = forecast.



% Growth 2000–20 4.1 2.4 2.8 3.0 2.7

Feedstocks for biodiesel production

Production

139

140

Biodiesel science and technology Table 5.7 Selection of suitable biodiesel feedstocks Vegetable oil crop Top ten oilseeds

Other oil crops New varieties

Soybean Cottonseed Groundnut Sunflower Rapeseed Sesame Oil palm Coconut Linseed Castor

Camelina HOa Sunflower Hemp HOa Rapeseed Olive LLb Rapeseed Jatropha HEAc Rapeseed Corn

Animal fats and used oils Tallow Lard Poultry fats Rendered fats Used frying oil

a

high oleic. low linolenic. c high erucic acid. b

Table 5.8 Global biodiesel market prospects (2010) Germany Europe USA

3.30 Mt 13.90 14.90

Sources: Eurostat/AUS Consultants/DOE/ETA.

environmental pollution due to WVOs such as oil used in cooking tempura is a social problem in Japan. The major bulk of biodiesel is currently made from rapeseed oil in Europe. Only a small fraction of the world’s oilseed resources (Table 5.2) would be expected to be available for industrial uses such as biodiesel. An estimated 10% of PMO could be allocated for the biofuel project without destabilising the international palm oil market. The present potential diesel engine fuel requirements far outstrip the ability of current vegetable oil production. This calls for cultivation of non-food crops for energy on set-aside land (EU agricultural policy). EU biodiesel production figures are shown in Fig. 1.6 and Table 14.31. Production in 2006 (4.9 Mt) increased by 54% as compared to 2005 (3.2 Mt), which followed a record growth of 65% over 2004. Installed EU27 production capacity (as of July 2007) exceeds 10.3 Mt, compared with 6.2 Mt in July 2006. European biodiesel production in 2006 required an acreage of 3.5 Mha (average yield/ha 1.4 t biodiesel). For biodiesel market prospects worldwide, see Table 5.8 and refs. [10, 11]. The availability and cost of all VOs are extremely critical for the industry. In fact, resources for biodiesel production strongly depend on pollination. While some commodity crops are wind-pollinated (e.g. corn and soybeans), most other biodiesel feedstocks (including oil palm, rapeseed/canola, sunflower

Feedstocks for biodiesel production

141

and cotton) are dependent on pollinators, mainly insects such as wild native bees or honeybees. In this context, it is not without concern that pollinators are currently endangered, for example, through colony collapse disorder (CCD) [12]. Foodstuff oils, such as soybean, sunflower and lauric oils, are traditionally quite expensive. Figure 5.1 shows price fluctuations of various vegetable oil commodities. Annual supplies of nine major vegetable oils (PMO, SBO, RSO, SNO, CSO, PNO, OO, CNO and PKO) have increased each year at a rate of 5–6 Mt (1998–2007) to 6.7 Mt more recently (2002–07). This rise has been used increasingly for non-food purposes, in particular during this period. However, as food demands increase by about 4 Mt/yr, whereas oleochemical use and use in animal feed grows at about 0.5 Mt/yr, severe price rises have resulted. Indonesia, Malaysia and other PMO producing countries (such as Nigeria) are categorised as high-yield low-cost producers, making PMO the world’s most cost-effective vegetable oil. Oil palm is also the highest oil-yielding crop among all VOs (see Table 6.1). As shown in Table 5.9, Indonesia is the world’s lowest cost producer of PMO with a production cost of US$165/t in 2003, with Argentina and Brazil the soybean oil champions (US$228/t). 800 Crude palm oil Soybean oil Sunflower oil Rapeseed oil

700

US$/t

600

500

400

300

200 1980

1985

1990 Year

1995

2000

5.1 Annual average prices of selected vegetable oils (North-west European market, 1980–2000) (Sources: Malaysian Palm Oil Board (2002); www.mpob.gov.my and Oil World (2002); www.oilworld.biz).

142

RSO

SBO

SNO

PMO

CNO

Australia Canadaa Poland Germany P.R. China UK France India

Argentina Brazil Paraguay USA P.R. China India Italy

Argentina Ukraine Russia France USA Spain

Indonesia Papua NG Malaysia Colombia Nigeria

Indonesia Philippines

a

Canola oil.

222.60 249.30 322.40 400.60 407.70 409.80 415.80 500.10

227.60 228.30 398.50 459.90 493.30 681.20 687.40

285.00 292.20 389.00 440.40 511.60 674.50

165.20 215.80 239.40 292.80 n.g.

328.10 430.20

Biodiesel science and technology

Table 5.9 Main world producers of vegetable oils and cost/t (US$, 2003) (after ref. 13)

Feedstocks for biodiesel production

143

Crops grown in tropical areas are cheaper than those grown in temperate areas. In general, Europe’s rapeseed industry is less competitive than all PMO producers and the aforementioned low-cost high-yield SBO suppliers. Nevertheless, with the incentives provided by their governments, it is still cheaper for Europe to produce its own RSO than to import it. For global and regional production figures of the main vegetable oils, see ref. [13]. Oleaginous crops used for industry are cheaper than those for human consumption (typical 2003 prices for rapeseed: non-food 7210–235/t; food 7225–257/t), some of which are in short supply, such as sesame (Sesamum indicum, Pedaliaceae) seed and safflower oils, and consequently highly priced. Production costs for biodiesel fuels may be reduced by using a variety of non-edible oils, such as cardoon or artichoke (Cynara cardunculus L.) oil [14], castor (Ricinus communis) oil [15], crambe (Crambe abyssinica) oil [16], physic nut (Jatropha curcas) oil [17, 18] and other vegetable oils of Indian origin [19, 20] (see Section 5.9). An upper-limit global biodiesel production potential of 45 Mt from 119 countries was estimated in October, 2007, of which 41.5 Mt could be produced profitably at today’s import prices [21]. The world’s top five palm and soybean oil producers (Malaysia, Indonesia, Argentina, USA and Brazil) are expected to account for 65% of global biodiesel production. Optimistic views foresee an upper-limit total potential biodiesel volume of 530 Mt through agricultural yield increases. This 12-fold increase is spread over many crops, but is mainly attributed to the tropical oilseeds palm and coconut, whose current yields are much below their well-managed yields. Even after a conservative increase in annual oil demand for food purposes of 165 Mt by 2015, some 365 Mt of biodiesel could then be produced [21]. However, agricultural intensification associated with boosting yields favours the practice of clear-cutting and can introduce additional problems including pressure on fresh water supplies from irrigation, nitrogen fertiliser run-off, and soil degradation. Plants transpire about 200 kg of water per kg of dry plant matter produced. Table 11.1 lists the critical success factors to ensure an industrially stable biodiesel feedstock.

5.4

Main biodiesel crops

5.4.1 Brassica oilseeds The Brassica oleracea family includes rapeseed, broccoli, Chinese cabbage, cauliflower, mustard, radish, kale, isis, camelina and turnip. Brassica oilseeds are one of the few edible oil crops that can be cultivated in the temperate zones of the world, at higher elevations and as winter crops. Both summer and winter species of brassicas are available, allowing cultivation in climatically different regions.

144

Biodiesel science and technology

Rapeseed (Brassica napus L. ssp. oleifera) oil with its high content of monounsaturated oleic acid (ca. 60%) and low levels of saturated (ca. 5.5%) and polyunsaturated acids (32.5%) is considered as being the ideal raw material for biodiesel (rapeseed methyl ether, RME) because of its combustion characteristics, oxidative stability and temperature. Rapeseed is the third most important source of vegetable oil in the world (Tables 5.4 and 5.10). Europe (EU25) is world’s key producer of rapeseed with a total rape planted area in 2007 of nearly 4.2 Mha, highly supported through the Common Agricultural Policy. Of the 11.42 Mt rapeseed grown in EU15 (1999–2000) 2.69 Mt came from set-aside land. Although the EU is a large producer of rapeseed (canola) oil, production (8.1 MMT forecast in 2008–09, up from 7.6 MMT in 2007–08 and 6.5 MMT in 2006–07) is not enough to cater for the growing demand (including biodiesel capacity growth). In 2004–05 already approximately one-third of the EU rapeseed crop was used by the non-food sector. Estimates of the amounts of oils and fats required to meet the EU goals (5.75% of biofuels by 2010) indicate that 85% of EU rapeseed crop would then be required for biodiesel production, necessitating imports. While alternative oils may be used, they give rise to some physical problems, such as poor flow (as in case of palm oil). A restriction of the potential quantities results from the requirement of crop rotation of the rapeseed plant. It can only be cultivated economically and for ecological reasons every third or fourth year. In contrast with grain or maize, rapeseed is not self-sustaining and monocultures are therefore impossible. Moreover, it should be remembered that it took some 50 years to triple the rapeseed oil crop yield. In 2006, rapeseed was grown on about 1.5 Mha of land in Germany, or 11% of the total agricultural land area; this is considered the maximum ecologically achievable cultivation potential. Approximately 7 Mha was used to grow crops for food. As Brassica species are strong emitters of ozone layer depleting alkane halides, oilseed rape cultivation can be questioned on environmental grounds [22]. The price of canola oil (Europe, pmt) has been rising steadily from a low Table 5.10 Geographic spread of rapeseed production (1999/2000) (after ref. [23]) Country

Crop (Mt)

Oil (Mt)

EU15 P.R. China Canada India Eastern Europe Australia Rest of the world World total

11.42 10.00 8.80 4.90 2.74 2.46 1.78 42.10

3.90 4.60 1.26 1.78 0.67 1.00 1.21 14.42

Feedstocks for biodiesel production

145

of US$359 in 1999–2000 to US$770 (2005–06 on average) and US$1577 more recently (June 2008). Several forms of plants included in the genus Brassica and Crambe are cultivated for the oil. Brassica oilseeds include such crops as B. napus L. (the most common rapeseed cultivated in continental Europe) and B. rapa L. or Rubsen oil (two primary species of rapeseed), B. carinata or Crambe abyssinica (Ethiopian mustard or colewart), and B. campestris (from rutabaga, or Swedish turnip) [24]. In fact, rutabagas are not oilseed plants (which produce oil in seeds) despite being in the same species as rapeseed and canola. Genetically modified rutabaga (preventing starch production, promoting oil biosynthesis) is being considered as a potential oil source [25]. Brassica juncea L. (mustard) is the common name for multiple species in the Brassica genus. Yellow mustard, referred to as white mustard (Sinapis alba L.) in Europe, is a spring-seeded crop that grows best in cool areas (< 302 K). As it is a different genus, it will not cross-pollinate with Brassicas. Yellow mustard seed is relatively small, about 100 000 seeds/lb. It does not have as high oil content as the other commonly known Indian mustard, referred to interchangeably in commerce as brown or oriental mustard. The oil is high in long-chain fatty acids, so biodiesel made from mustard would have properties different from biodiesel from most other oilseeds. High glucosinolate content renders yellow mustard unsuitable as food oil and animal feed. High-erucic rapeseed oils (HERO; erucic acid content > 45% detrimental to food quality) constitute the classic source of erucic acid and are important vegetable oils for oleochemical and lubricating purposes (e.g. slip oil in plastic bags) [26, 27]. Winter hardy rapeseed (B. napus L. and B. rapa L.) were characterised for oil, erucic acid and glucosinolate contents for use in breeding programmes to develop commercial production of rapeseed [28]. The erucic acid content was higher in rapa (32.6%) than the napus accessions (26.1%) with a small difference in the mean oil content in the seeds. Although rapeseed (colza oil or coleseed) used to contain high levels of erucic acid and glucosinolates, nowadays most rapeseed cultivars – developed by classical breeding methods – belong to the so-called ‘zero’ (0) and ‘double zero’ (00) varieties with reduced levels of both erucic acid (<2%) and glucosinolates (<30 mmol/g), also referred to as edible rapeseed or Canola (CANadian Oil Low Acid), in accordance with FDA standards. Canola (Brassica napus L.) is not a botanical term, but one used to describe compositional qualities. From an agronomic standpoint, canola offers the advantage of being both a spring and a winter crop. Canola rotates nicely with wheat. Whereas industrial rapeseed traditionally refers to any HERO variety, the low-erucic (LE) acid high-oleic varieties (with some 60% C18:1) are of interest to the food industry in view of their high nutritional qualities and a low level of saturated fat. In the US and Canada, canola and rapeseed

146

Biodiesel science and technology

are distinct crops, carefully kept apart with adequate buffer distances. Strict segregation of Brassica varieties is necessary in view of observed crosspollination between industrial rapeseed (now mainly localised in Eastern European countries) and canola. Since the break-up of the Eastern bloc, industrial rapeseed has yielded to canola because industrial rapeseed cannot be sold in EU countries for edible purposes. Erucic acid containing rapeseed varieties are now considered specialty crops in Europe and Canada. China, Russia and India, however, still use high-erucic acid rapeseed oil for human consumption. Since commodity low-erucic rapeseed is now widely available with supplies beyond that needed for food purposes, and the availability of HERO has greatly been diminished, low-erucic RSO (canola) is now the source of oil for some non-food applications and the primary component of biodiesel in Europe. Roughly 60% of rapeseed oil production finds non-food applications. With its low SFA and high MUFA contents biodiesel obtained from 00-rapeseed shows both good stability and winter operability. However, contrasting results have been reported concerning engine performance and carbon deposits of rapeseed diesel in comparison to fossil diesel [29]. Canola is a type of rapeseed that was first developed in the 1970s [30] Canadian plant breeders developed canola explicitly for the nutritional advantages compared to industrial rapeseed. Canola varieties of napus and juncea have similar compositional characteristics but different crop or agronomic qualities. Canola grows on most soil types but requires good drainage. Canola may be grown no more than two in every five years on the same plot of land. Canola is cultivated on some 15.5 M acres of Canadian farmland compared to 1 M acres in the US. Canadian farmers are expected to grow more than 14 MMT of canola by 2015 (as compared to 10 MMT in 2007) [31]. The yield increase is due to adoption of hybrids, better agronomic management and improved genetics. Canola yield could improve by as much as 35% by 2015 from the present level of about 30 bushels per acre. Higher-yielding canola varieties are increasing grower profits. Almost all the Canadian canola crop is used for human consumption, with less than 5% going to biodiesel. Despite a large canola oil output in Canada, the use of canola biodiesel as a total fuel replacement is not practical. To satisfy current highway transport diesel fuel requirements, it would require 11 times the acreage of all the canola grown in Canada to replace the diesel fuel used (5 Bgy). North Dakota and Minnesota are the main US canola producers. Canola’s share of the US biodiesel market was boosted in 2007 when ADM’s 85 MMgy biodiesel plant came on stream alongside its canola crushing facility at Velva, ND. ADM’s Velva facility crushed 1.3 MMt (1.4 Mt) of canola in 2006, which was twice the amount grown in the US in 2006. Imports from Canada were needed. Development of a high-fat content (25–40%), low cost (US$0.10/lb), non-food grade mustard seed is under way. The key development that makes

Feedstocks for biodiesel production

147

industrial mustard so promising is that the defatted meal (after the oil is removed) can be used as an organic pesticide without further processing. The inedible mustard can be grown in rotation with dry-land wheat production without irrigation. Blue Sun Biodiesel (Fort Collins, CO) has started development of an industrial mustard seed industry to support the biodiesel industry. The Ethiopian mustard (B. carinata) oilseed crop, which originated in Ethiopia, allows use of set-aside lands in (high heat and drought) environmental conditions (Spain, Italy, North Africa) unfavourable for the cultivation of B. napus. B. carinata provides greater grain yields than B. napus in conditions of low rainfall during the grain filling period and high temperature. Canola-quality B. carinata is a potential oilseed crop for the Canadian prairies. Recently, B. carinata cultivation has been promoted also in Sicily (55 ha in 2006–07; to be extended to about 3.5 kha). Limitations of B. carinata for biodiesel production are its high content of erucic acid and linolenic acid (exceeding the EN 14214 limit) with the risk of a correspondingly high iodine value (130 g I2/100 g) [32], and high allyl glucosinolate concentrations; however, a more recent pilot plant study reported 109.4 g I2/100 g [33]. B. carinata also has a high sulphur content (0.5% on a dry basis) as compared to most forms of biomass. This can create a problem of SO2 gas emissions above the normal levels found in the combustion of biomass. Tables 5.11 and 5.12 show some commercially available and extreme fatty acid variants in breeding material from important oilseeds. Rapeseed is highly accessible to biotechnological methods. The manipulation of oil synthesis in rapeseed to produce specific, desired, chemically altered triglycerides has already been implemented on a large scale [51]. The breeding of high oleic acid (>80%) or linolenic acid deficient (<3%) rapeseed forms has been achieved by induced mutation [44, 52] and genetically by inhibition of the inherent 12- or 15-desaturase genes [45] (Table 5.12). RS80 is an 80% oleic acid containing GM rapeseed oil obtained from B. campestris or B. napus (available from AC Humko, Memphis, TN). InVigor“ Health canola (Bayer CropScience/Cargill) is a high oleic acid hybrid for the food market. New rapeseed varieties (e.g. LZ 7632) are reaching high levels of up to 87% C18:1. Inhibition of the desaturation step in B. rapa yields high stearic acid seed oil [43]. Other special fatty acid variants (with high concentrations of C8-C14 chain lengths), which are of special interest for oleochemistry and which could be obtained previously only from tropical vegetable oils (CNO, PKO), were developed by gene technology [42]. Canola oil synthesis was altered by genetic engineering to produce high levels of C12 : 0 and reduced levels of C16 : 0 and C18 : 0 [51]. High lauric acid rapeseed (40–60% C12 : 0) is rich in sn-1,3-dilauroyl triglycerides and is commercially planted [37, 51]. Auld et al. [44] developed rapeseed lines with reduced levels of polyunsaturated fatty acids, e.g. linoleic acid. It should be mentioned that

148 SNa IVb CN 12:0 14:0 16:0 18:0 18:1 18:2 18:3 20:1 22:1 Othersc Reference(s)

Type

Variant

Origin

Rapeseed

high erucic acid 0 or 00 (canola) low linolenic acid high lauric acid (HLCO)

conventional 180 102 54 natural mutation 199 121 46 mutagenesis 199 115 48 gene 231 71 54 technology

Sunflower conventional high oleic acid (HO) mutagenesis

201 140 42 199 93 53

– – – 37

– – – 4

3 4 4 3

1 2 2 1

11 60 61 33

12 21 28 12

9 10 3 7

8 1 1 –

52 1 – –

4 1 1 3

[34] [34] [35] [36, 37]

– –

– –

7 3

5 4

19 83

68 10

– –

– –

– –

1 –

[34] [34]

Soybean

conventional

202 141 42

–

–

11

4

23

54

8

–

–

–

[34]

Linseed

conventional low linolenic mutagenesis acid (Linola)

202 201 28 201 154 39

– –

– –

6 6

4 3

18 15

14 73

58 3

– –

– –

– –

[34] [38]

Peanut

conventional 199 high oleic acid (HO) natural mutation 197

– –

– –

12 6

4 2

47 81

31 3

– –

– –

– –

6 8

[39] [39, 40]

a

mg KOH/g. g I2/hg. c wt%. b

99 51 78 56

Biodiesel science and technology

Table 5.11 Some commercially available fatty acid variants of important oilseeds (after ref. [41])

Table 5.12 Extreme fatty acid variants in breeding materials from important oilseeds (after ref. [41]) Variant

Method

14:0

16:0

18:0

18:1

18:2

18:3

20:1

22:1

Others

Source

Rapeseed

high myristic acid high stearin high oleic acid (HO) high oleic acid (HO) low linolen

gene technology gene technology mutagenesis gene technology gene technology

17.7 – – – –

23.1 4.0 4.2 4.3 3.8

2.4 29.0 2.2 1.4 1.5

33.7 15.0 80.2 84.1 68.5

14.8 19.0 4.5 5.2 22.1

3.8 22.0 5.2 2.9 1.2

– 1.0 1.8 0.9 1.1

– – – – –

4.5 10.0a 1.9 1.2 1.8

[42] [43] [44] [45] [45]

Sunflower high palmitin high stearin high oleic/low saturated fatty acids

mutagenesis mutagenesis mutagenesis

– – –

25.2 5.1 3.2

3.5 26.0 2.4

11.4 13.8 92.1

55.1 55.1 2.3

– – –

– – –

– – –

4.8b – –

[46] [46] [47]

Soybean

low linolenic acid low palmitic acid high palmitic acid high stearic acid high oleic acid (HO)

mutagenesis mutagenesis mutagenesis mutagenesis gene technology

– – – – –

10.5 3.7 17.3 8.4 6.6

4.6 3.7 2.9 28.1 3.6

23.2 24.1 16.8 19.8 84.9

59.6 58.9 54.5 35.5 0.6

2.0 8.9 8.3 6.6 1.9

– – – – –

– – – – –

– 0.7 0.2 1.6 2.4

[47] [48] [41] [41] [49]

Linseed

high palmitin

mutagenesis

–

27.8

1.8

17.5

6.0

42.0

–

–

4.8c

[50]

a

Includes 6 wt% C20:0, 2 wt% C22:0, 1 wt% C24:0. Includes 3.7 wt% C16:1. c C16:1. b

Feedstocks for biodiesel production

Type

149

150

Biodiesel science and technology

there are also new high-erucic varieties and varieties with modified fatty acid composition [53, 54]. GM high-erucic acid B. napus cultivars may even contain > 80 mol% erucic acid [55]. Similarly, recombinant genotypes with increased MUFA (C22 : 1 + C20 : 1 + C18 : 1) of up to 89% and decreased PUFA (<8%) and SFA content (<3.5%) have been described [56]. Rapeseed breeders have also succeeded in improving yield levels of up to 2.9 t/oil in North Germany using ‘precision farming’. Figure 5.2 illustrates rapeseed cultivation and processing.

5.4.2 Sunflower oilseeds Sunflower (Helianthus annuus L.) yields are lower than rapeseed yields (see Table 6.1), but SNO represents a choice for biodiesel production in countries with warm and dry climatic conditions and rich soil. Although seed oil of standard cultivated sunflower is considered to be of good quality for edible purposes, it has more limited use for fuel production in view of its high linoleic acid content, and high iodine value of the resulting sunflower oil methyl esters (SNMEs), exceeding the European biodiesel standard (EN 14214) value of 120 g I2/100 g. In this respect, mid- and high-oleic varieties with higher oxidative stability are of more interest [57]. Mid-range oleic NuSun has been developed for frying applications and is in direct competition with low-linolenic canola oil [58]. HO types were developed by mutagenesis (see Table 5.11) [59, 60], as well as varieties with increased proportions of saturated

1 ha rapeseed

3 Mt rapeseed

Crush

1.77 Mt rape meal

1.23 Mt crude oil

0.1 Mt methanol

Transesterification

1.22 Mt rapeseed methyl ester

5.2 Rapeseed cultivation and processing.

0.12 Mt glycerol

Feedstocks for biodiesel production

151

fatty acids (C16:0, C18:0) (see Tables 5.12 and 5.13) [46]. Sunyl 80 “ is a high genetically-modified sunflower oil (80% oleic acid), available from AC Humko, Memphis, TN. Industrial use of HO sunflower oils is favoured by a low SFA content [47]. In recent years, the development of cultivars with high oil content and high oleic acid concentration is an important breeding objective for this crop [61]. These are no transgenic sunflower varieties. Sunflower is the only major oil crop native to western North America. While the US is involved in the production of the nutritionally attractive NuSun, Argentina produces regular and high-oleic sunflower oils; Europe has focused on high-oleic sunflower. For a recent review, see ref. [62].

5.4.3 Soybean oilseeds World soybean production has increased from 125 Mt in 1995 to over 200 Mt in 2005 with an average annual increase of 4.6%. During the period 2002–2007 soya provided about 50% of the growth in world oilseed crush (about 31 Mt). The US soybean (Glycine max) production capacity (with a record of 86.8 Mt on 74 M acres in 2006) accounts for 40% of the world soybean output and for over 50% of the total available bio-based oil for industrial applications [63]. The soybean market has historically been driven by demand for meal, which is not a very storable product, as opposed to oil (making up 35–40% of soybean value). With the advent of biodiesel, this is now moving towards an oil-driven market with prices at top levels. The high value of soybean oil as a food product makes production of a cost-effective fuel very challenging. Soybean oil is a complex mixture of triglycerides with a high proportion of polyunsaturated fatty acids (PUFAs, 63.0%), a characteristic that renders SBO very susceptible to peroxidation with molecular oxygen. Similar to Table 5.13 Sunflower oil mutants according to their fatty acid composition (wt%), indicated by average, minimum, and maximum values (after ref. [64]) Class

C16:0

C16:1

C18:0

C18:1

C18:2

High C16:0

32.0 29.3–35.8

6.9 6.0–8.5

2.0 1.7–2.2

9.7 9.1–10.4

47.4 40.6–50.1

High C16:1/high C18:1 30.6 27.1–35.2

8.0 6.8–8.6

1.9 1.7–2.2

55.6 51.7–59.4

3.6 3.0–4.4

High C18:0

6.9 0.0 6.4–7.7

24.8 22.6–28.5

16.7 13.7–19.7

51.3 47.3–55.2

High C18:1

4.6 0.0 3.9–7.6

3.9 2.9–5.3

88.2 83.9–90.5

2.9 1.9–4.1

Standard

6.3 0.0 4.9–9.6

9.4 3.9–15.1

40.0 20.3–54.9

44.1 34.1–64.4

152

Biodiesel science and technology

sunflower oil, soybean oil is also excluded by EN 14214 in view of high iodine values of 121–143 g I2/100 g. There are several thousand sub-species of soybean. Prior soybean oils often lacked important food quality properties (oxidative stability, saturated fat content, flavour) or biodiesel properties (NOx emissions, cold flow). As a result of intensive quality breeding, the fatty acid pattern of soybean is now remarkably variable [65]. Soybean oil typically contains about 16–20 wt% SFA (13–16% C16:0 and 3.4% C18:0). Low-saturate oils contain between 3.6 and 8 wt% saturated fatty acids. A zero-saturate oil composition contains less than 3.6 wt% SFAs. Methods for producing such altered seed oil compositions have been outlined [66] and enable production of SBO containing 69–73 wt% C18 : 1, 21–24 wt% C18 : 2, 0.5–3 wt% C18 : 3 and 2–3 wt% SFA. Low-linolenic varieties (1.5–2.3% C18 : 3, IV 120 g I2/100g) – mainly for food applications – have improved oxidative stability [67]. The development of soybean cultivars with oil enriched in oleic acid, such as mid-oleic (43.7% C18:1, IV 107 g I2/100g) and high-oleic (81.3% C18 : 1, IV 90 g I2/100g), is an important breeding objective for the crop. These oils exhibit a higher degree of oxidative stability than oils low in oleic acid [68]. High-oleic (HO) soybeans have been produced by genetic engineering [49]. A transgenic soybean seed with an oil composition comprising high levels of oleic and linoleic acid, and low levels of linolenic acid and saturated fatty acids has been claimed [66]. Other varieties have modified proportions of individual saturated fatty acid (Table 5.12) [47, 48]. Plant breeding efforts are currently focused on developing low-palmitic, low-linolenic soybean [69]. Almost all of Argentina’s soy production is based on GM material. Although soybean oils have been modified by various breeding methods to create benefits for specific markets, a soybean oil that is broadly beneficial to major users in the food and industrial markets is not readily available. An optimised SBO composition for both food and fuel use is retained to contain about 24 wt% PUFA [70]. A target soybean oil composition (C16 : 0, 2.1%; C18 : 0, 1.0%; C18 : 1, 71.3%; C18 : 2, 21.4%; C18 : 3, 2.2%; other, 2.0 wt%) is characterised by CP, PP and CFPP values of 255, 252 and 252 K, respectively, which is comparable to or better than the corresponding values for petroleum diesel. The agronomic challenge is then to create soybean oil near the target composition without sacrificing soybean yield. Soybean oil prices (US, pmt) have varied considerably, from a low of US$507 in 2004–05, to US$684 (June 2007), US$1376 (June 2008) and to US$1120 in Aug. 2008 [71]. Global soy oil production is expected to increase to 38.4 MMT in 2008–09, compared with 37.9 MMT in 2007–08 [72]. The overall consumption of SBO is expected to increase to 37.9 MMT in 2008–09, compared with 37.2 MMT in 2007–08. It is anticipated that soybean oil prices will reach a record high in 2008–09, attributable to tight global inventories, growing demand and escalating production costs.

Feedstocks for biodiesel production

153

5.4.4 Palm oil products The palm family (palmae or Arecaceae) comprises over 4000 species. Analysis of oil palm genetic diversity has been reported [73]. The oil palm Elaeis guineensis, which grows in rainy climates, is the highest oil-yielding crop (see Table 6.1) and the major supplier of both edible oil and renewable industrial feedstocks since 2003. Palm oil production in some 42 countries worldwide has doubled since 1990 with an increase in cultivated area from about 4 Mha to 9.1 Mha in 2006 (exceeding 35 Mt of oil), mainly at the expense of tropical rainforests. Plantations incur high initial costs, with a first harvest after 5 years. The trees are most productive at 7–12 years of age. The practical production life of an oil palm tree in a plantation is about 25 years. Oil palm is regarded as the most cost-effective vegetable oil crop with typical yields of about 5.0 t/ha/yr. However, the average oil yield in Malaysian plantations is 19 t/ha/yr, and top producers even achieve 25 t/ ha/yr. Biotechnological efforts are directed towards production of palm oil with even higher oil yields, high IV and high monounsaturated fatty acid contents for edible purposes and industrial uses [74]. High yielding seedlings are expected to allow an increase in CPO yield to 27–30 t/ha. The crop that produces over 40 MMT of oil annually worldwide (43.2 MMT forecast 2008–09; 41.4 MMT in 2007–08) is hand harvested. Palm oil, a viscous semi-solid even at tropical ambients and a solid fat in temperate climates, is used mainly as edible oil; its non-food use (cosmetics, toiletries, biodiesel) is relatively small at about 20% [75]. Palm oil has to compete with 16 other oils and fats (total about 135 Mt/yr) for its market share. Fluctuations in the demand for palm oil are due largely to competition from soybean oil. Palm oil needs biodiesel demand [76]. The genus Elaeis contains two very closely related palms of high economic value: E. guineensis (African oil palm) and E. oleifera (American oil palm) with different proportions of the major fatty acids. While palmitic acid (C16:0) is the predominant fatty acid in E. guineensis, oleic acid (C18:1) predominates in E. oleifera. The considerably greater proportion of unsaturated fatty acids determines a higher iodine value and higher fluid fraction at room temperature (lower melting point) in the mesocarp oil of E. oleifera (80%) than in E. guineensis (50%). Hybrid plants might produce an even more desirable oil. Palms from Madagascar have high iodine value and unsaturated oil (C18:2) content [77]. In Africa, the natural habitat of oil palms is the forest fringe near rivers, where moisture is plentiful. Oil palms differ from most other oil crops in that both the fruit pulp and seed are used. Two totally different kinds of oil are produced from the oil palm: orange red palm oil (PMO) and colourless palm kernel oil (PKO). Palm oil (m.p. 298 to 323 K) is extracted from the outer reddish-yellow fleshy mesocarp of the fruit. Palm kernel oil is extracted from the white

154

Biodiesel science and technology

kernel (which is inside a hard shell) of endosperm. Similar to coconut oil, with high content of saturated acids, mainly lauric acid (C12 : 0), it is solid at room temperature. Both oils are quite different in their fatty acid profile and exhibit very poor compatibility with each other. The ratio of palm oil to palm kernel oil is about 5–10 : 1. Fractionation is used in the oils and fats industry to physically separate oils into high-melting ‘stearin’ fractions and lower-melting ‘olein’ fractions. Palm oil is most widely fractionated (see Fig. 5.3). The main triglycerides in palm oil can be grouped into: trisaturated triglycerides – typically PPP (palmitate-palmitate-palmitate); monounsaturated triglycerides – typically POP (palmitate-oleate-palmitate); and polyunsaturated triglycerides – typically POO (palmitate-oleate-oleate). These three groups also correspond roughly to the three main fractions produced from palm oil-stearin (PS), mid-fraction, and olein (POo). A common fractionation process is the separation of palm mid-fraction from palm olein. Palm olein (POo) is the liquid fraction derived from the fractionation of palm oil, and palm stearin (PS) the high-melting (hard) fraction. Palm stearin and palm kernel olein are both products of the palm oil industry that presently have limited use. Free fatty acids are released naturally in crude palm oil (CPO) and can be increased by the action of enzymes in the palm fruit and by microbial lipases. During storage, FFAs are produced by the reaction of oil with water. Standard specifications for the FFA content (as palmitic acid) are 5% maximum in CPO and 0.1% maximum in refined-bleached-deodorised (RBD) oils, respectively. Routine procedures to determine the FFA content in vegetable oils are AOCS Official Methods Aa 6-38 and Ca 5a-40, as well as FTIR analysis [78]. Crude oil or fat

Pre-treatment/refining Option 1

Option 2

Dry fractionation

Transesterification

Stearin

Olein

Food/feed

Transesterification

Dry fractionation

Olein FAME

Stearin FAME Oleochemical

Biodiesel

5.3 Fractionation of palm oil or crude animal fat.

Feedstocks for biodiesel production

155

Palm diesel consists of methyl esters of crude palm oil or crude palm stearin prepared from transesterification with methanol. Use of fatty acid alkyl esters, in particular ethyl esters of palm oil, as diesel fuel was first reported in 1937 by Chavanne [79]. Palm oil ethyl esters were already used as a biodiesel in the Belgian Congo before World War II [80]. High FFA contents in crude palm oil feedstock (up to 30%) necessitate deacidification or acid-catalysed pre-esterification. In the patented MPOB/ Petronas process, esterification of FFAs present in crude palm oil, crude palm stearin and crude palm kernel oil into methyl esters is carried out with a solid-acid catalyst; transesterification of neutral glycerides then proceeds in the presence of a base catalyst [81]. Biodiesel produced from palm oil has high cetane levels, which makes it prized as a fuel additive. The high content of saturated fatty acids in CPO (47.0%) confines operation on palm oil methyl esters (POMEs) (pour point 288 K) as a car fuel to tropical climates. Low pour point (258 K) fractionated palm diesel (without additives) has recently been developed, which is suitable to temperate climates [82]. Both types of palm diesel (normal and low pour point palm diesel) meet all the specifications in EN 14214 and ASTM D 6751. Figure 5.4 shows an integrated process for the production of palm diesel and palm phytonutrients. The co-production of high-value phytonutrients will make palm diesel more viable. A number of issues arise in the context of oil palm cultivation [83]. Oil palm plantations should be established exclusively on degraded land (tropical fallow). Malaysian palm oil, excluding land-use effects, can achieve a 60% net CO2 reduction when used as a feedstock for biodiesel. CO2 reductions for biodiesel oil palm from marginal degraded land are more conspicuous than Crude palm oil (CPO)

CPO methyl esters (palm diesel)

Distilled methyl esters (palm diesel)

Feedstocks for value-added oleochemicals

Phytonutrients concentrate

Carotenes, vitamin E, sterols, squalene, co-enzyme Q, phospholipids (lecithin)

5.4 Integrated process for production of palm diesel and palm phytonutrients.

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Biodiesel science and technology

from natural forest. On the other hand, biodiesel oil palm from plantations through cutting of tropical forest may well lead to a negative CO2 balance. Biodiesel from palm oil (as well as ethanol from sugarcane) must be discussed in the context of indiscriminate tropical rainforest clearance [84]. Accelerating demand for palm oil is contributing to the 1.5% annual rate of deforestation in South-East Asia [85]. A Roundtable on Sustainable Palm Oil (RSPO) was set up in 2004 to define, identify and promote ‘sustainable’ palm oil production. However, as long as the certification system of this branch organisation is not effective, the use of palm oil must still be regarded as unsustainable [86]. Palm oil prices (Malaysia, pmt) have developed from a low of US$235 (2000–01) to US$416 (2005–06 on average), US$1291 (March 2008) and US$879 (Aug. 2008).

5.4.5 Oilseed flax There are both fibre and oilseed varieties of flax (Linum usitatissimum L.). Oilseed flax can grow in a variety of climates but in cool climates has a higher oil content. With sufficient moisture, winter flax can yield 2000 to 3000 lb/acre of seed. Oilseed flax has both high- and low-linolenic varieties, called linseed and linola or solin, respectively. Solin varieties have been developed in Canada. Linseed oils with high C18:3 contents are preferred for non-food, technical purposes, although not for biodiesel application (unless as blends). The main non-food uses of linseed (flax) are in the production of dyes, coatings and linoleum. Drying oils such as linseed (Linum usitatissimum L.) oil, Canadian linseed oil and the oil of Iberian dragonhead (Lallemantia iberica L.) typically contain 54.1, 60.2 and 68% of linolenic acid (C18 : 3), respectively, and show high theoretical iodine values of 211, 226 and 236 g I2/hg and low cetane numbers [87]. The high reactivity of the polyene structure of linseed fatty acids results in high sensitivity toward autoxidation. Both linoleate and linolenate structures oxidise rapidly since they contain double allylic hydrogen atoms that are easily abstracted in the autoxidative process. Oils containing linolenic acid are widely used in oil-modified resins and varnishes in works of art. In oil painting, linseed oil remains the most popular oil for binding pigment, thinning paint, and varnishing finished paintings. Walnut oil and poppyseed oil are also favoured by painters. Poppyseed oil dries more slowly (5–7 days) than linseed oil (3–5 days). Flax oils are high in omega-3 fatty acids and have significant value in the food oil market. Modern crop development has resulted in linseed varieties with higher yields, controlled oil content and increased content of unsaturated fatty acids. Classical mutagenesis has been used to breed linseed varieties with less than 5% C18 : 3 (linola quality) [38, 88, 89] or with increased palmitic

Feedstocks for biodiesel production

157

Table 5.14 Fatty acid content (wt%) of linseed oils (after ref. 90) Oil

C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 C20:0 C20:1 SNa

IVb

CN

Edible linseed 6.0 oilc

0.1

3.3

13.0

74.2

2.7

0.1

0.4

200.4 154.2 38.8

Conventional linseed oil

0.1

3.5

13.4

16.8

60.4

0.1

0.4

201.1 166.4 36.0

5.1

a

mg KOH/g. g I2/hg. c PurolinTM. b

acid content in the oil [50] (see Tables 5.11 and 5.12). In the edible linseed crop (linola varieties; solin) the linolenic acid content has been reduced substantially from 50% to 2% through traditional breeding procedures. Genetic manipulation of the activity of desaturase enzymes blocks the conversion of double-unsaturated linoleic acid (C18 : 2) into triple-unsaturated linolenic acid (C18 : 3) in the developing seed. This creates low-linolenic mutants with very high levels of linoleic acid (65–76%). This reduction in unpalatable linolenic acid greatly increases the oxidative stability of the oil. In fatty acid composition, edible linola oil (SFA 10%, MUFA 17%, PUFA 73%) is similar to premium polyunsaturated oils such as SFO, SNO and CRO [91]. Although the risk of formation of rancidity products is removed, the iodine value is reduced and such oils are unsuitable in paints and coatings but qualify instead for biodiesel blending application. Drying of linseed oils with different fatty acid profiles with either high content of linoleic or linolenic acid (Table 5.14) has been studied. The oil high in C18 : 3 oxidises rapidly. Development of linseed with higher C18 : 3 contents for industrial purposes via pedigree-selection has been reported [92]. Flax oil and high a-linolenic oils (perilla, camelina and chia) were recently reviewed [93]. Use of linseed methyl esters with high di-, tri- and polyenoic fatty acid contents in biodiesel requires blending with RME [3].

5.4.6 Safflower oilseeds Safflower or False saffron (Carthamus tinctorius L., Asteraceae family) is an annual drought-resistant niche crop, which grows in the temperate zone where wheat and barley do well. India is the largest producer of safflower, which is grown exclusively for its food oil, which is high in essential unsaturated fatty acids. Around half of US acreage is in California. The cost of growing safflower runs just a little higher per hectare than barley. Traditional plant breeding and plant biotechnology play an important role in developing safflower, sunflower, soybean, rapeseed, linseed and peanut varieties with increased seed oil yields and fatty acid profiles that more closely

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Biodiesel science and technology

meet the requirements for food and non-food use, including drought-tolerant varieties that have low fertiliser and pesticide requirements [94]. Genetic engineering, which enables development of crops producing seed oils with tailored fatty acid compositions [64, 66], may uncover new horizons in biodiesel production. Most alterations in the oil quality of cultivated plants have concentrated on rapeseed (B. napus). High-oleic (HO) canola, safflower, and sunflower oils, as well as low-linolenic (LoLn) canola and soybean oils, have been developed. HO safflower with 77.4% C18:1 (SFA 7.0%, MUFA 78.0%, PUFA 15.0%) is characterised by a low iodine value (80–100 g I2/ hg) and high CN number (52.2). For further details, see ref. [95]. Turkish safflower seed oil conversion to methyl esters as a biodiesel has been described [96]. Safflower oil does not meet European EN 14214 biodiesel specifications due to high IV (126–150 g I2/hg) and low CN (30).

5.4.7 Coconut oil crops Different species of coconut (Cocos nucifera) live in adverse conditions. Coconut oil is a primary source of basic oleochemicals (soaps, lubricants, plasticisers, surfactants, detergents) [97]. Coconut oil is the main crop in the Philippines (1.25–1.75 Mt/yr), which intends developing coconut biodiesel (a pilot plant was already operational in 1995); see also Sections 14.3 and 14.3.1. Coconut and palm oil production in South-East Asia is frequently hit by weather-related problems, such as typhoons. Biodiesel from the two lauric oils, originating from coconut and palm fruit kernel (E. guineensis), which both contain high contents of C12:0 (approximately 50%) and saturated short-chain fatty acids (~85–90%), are characterised by an excellent cetane number but poor cold-temperature properties (relevant only to temperate climates) [98]. Coconut oil generates more glycerol (13.5%) than most other oils and fats (from 9 to 12%). The coconut biodiesel life cycle system is shown in Fig. 14.4.

5.4.8 Peanut cultivars Peanut (Arachis hypogaea) cultivars are characterised by a slightly lower oil yield per acre than rapeseed but much higher than soybean (see Table 6.1). Yields increase considerably (up to 3.3 t/ha) by irrigation. Peanuts are native to South America. Peanut oil has excellent stability, is extremely durable and less prone to oxidation than other vegetable oils in frying applications; the oil price is high. It is well known that the small diesel engine shown at the Paris exposition in 1900 by the French Otto Company ran on arachide (or peanut) oil [99]. Peanut oil has a low cetane number (41.8). High-oleic peanut cultivars, developed using conventional breeding procedures, contain up to 81% oleic acid (Table 5.11) [40] (see also ref. [100]). Such HO mutants

Feedstocks for biodiesel production

159

provide an oil with high oxidative stability and improved CN (58.3) [39, 101, 102]. In the US there are currently 24 peanut varieties being scrutinised for biodiesel application, including Georgianic. Promising varieties also include DP-1 and Georgia-048, a new high-oleic, Spanish-type peanut (ars.usda. gov). Production of these peanuts would be limited to the southern regions of the US where growing conditions are more suitable. Production and characterisation of biodiesel from groundnut oil have been reported [103]. Development of pure biodiesel from groundnut oil and its blends up to 10% is actively being pursued in Karnataka State, India [104].

5.5

Minor edible oil crops

Various alternative edible oils have suitable fatty acid compositions for use in biodiesel applications but are not expected to find large-scale application due to their high price and/or limited availability. Olive and corn oils are used as quality oils in human nutrition [105, 106]. Olive tree (Olea europaea L.) cultivation started in Syria in the prehistoric age. Olive oil production in Mediterranean basin countries now accounts for 97% of world production (2.81 Mt/yr). Use of olive oil for fuel use was critically considered many years ago [107]. Spent olive oil constitutes a biodiesel raw material resource for local and niche applications [108–110]. Olive residue (pomace) oil is obtained by treating pomace (the substance remaining from previous pressings) with solvents. Pomace oils are classified as crude olive-pomace oil, refined olive-pomace oil and olive-pomace oil. The latter is not recommended for human consumption. Argan oil from the oil fruit of Argania spinosa L. (Sapotaceae), an endemic tree located mainly in South-West Morocco, is well known for its cosmetic, pharmaceutical and nutritional virtues. The unique fatty acid composition (in %) of cold-pressed argan oil – available in quite limited quantities – is: C14 : 0, 0.4%; C16 : 0, 13.5%; C18 : 0, 5.4%; C18 : 1, 44.8%; C18 : 2, 35.7%; C18 : 3, 0.1%; C20 : 2-3, 0.6%; (SFA 20%, MUFA 45%, PUFA 35%, IV 109, CN 49.0, SN 200.9) [111]. Tigernut or yellow nut-sedge (Cyperus esculentus L.) is a fast growing root crop, commonly found wild and cultivated in Northern Nigeria, which yields oil (also called chufa oil) with high oleic acid content (68.8%) and low acidity (0.4 mg KOH/g). Its fatty acid composition (C14 : 0, 0.1%; C16 : 0, 13.2%; C16 : 1, 0.3%; C18 : 0, 4.3%; C18 : 1, 68.8%; C18 : 2, 11.7%; C18 : 3, 0.2%; C20 : 0, 0.6%; C20 : 1, 0.2%; C22 : 0, 0.1%; C24 : 0, 0.2%) is very similar to that of olive oil. C. esculentus oil was first used by Egyptians some 4000 years ago in preference to olive oil. Tigernut is more valuable for its chemical and nutritional properties than as a fuel. The biofuel characteristics of tigernut oil have been reported [112, 113]. Cottonseed oil (CSO) is a vegetable oil extracted from the seeds of the

160

Biodiesel science and technology

cotton plant (Gossypium herbaceum) after the cotton lint has been removed. It must be refined to remove the naturally occurring toxin gossypol (a polyphenol). Cottonseed oil is one of the few oils considered acceptable for reducing saturated fat intake. CSO is among the most unsaturated oils (PUFA, 52%); others include safflower (PUFA, 79%), corn (PUFA, 59%) and sunflower seed oils (PUFA, 61.5%). Cottonseed oil has many food applications (salad oil, cooking oil, shortenings or margarine, baking and frying fats) [114]. Only a small amount (18%) is used for other industrial purposes. Cottonseed oil was considered as a fuel for diesel engines as long ago as the early 1950s [115]. Cotton (oil) is also one of the main four (soy, corn, rapeseed/canola and cotton) genetically modified crops grown around the world. Oil contents and yields are low. Rice is a staple food for around half the world’s population, next to wheat. Worldwide, more than 415 Mt of rice was consumed in 2006–07. Over 90% of world rice production is concentrated in Asia. China will require 600 Mt by 2020. Rice bran oil (RBO) is an important derivative of rice [116]. Rice bran is a brown layer present between rice and the outer husk of the paddy. Rice bran oil ranks first among the non-conventional, inexpensive, lowgrade vegetable oils and is widely available. Depending on the variety of rice and degree of milling, the bran contains 16–32 wt% oil. Dark-coloured crude rice bran oil (CRBO) is difficult to refine because of its high content of free fatty acids (up to 60%), unsaponifiable matter and colour. RBO is not considered as an edible oil all over South-East Asia. Using RBO as a biodiesel with a transesterification process followed by removal of esters gives an unsaponifiable liquid fraction which contains highly concentrated and highly value-added nutraceutical and bio-active components (g-oryzanol, tocopherols, tocotrieniols, phytosterols and squalene). Utilisation of these compounds reduces the cost of rice bran biodiesel. Consequently, replacement of expensive edible oils with RBO as a raw material for biodiesel has economically attractive prospects. Although corn oil was considered as a fuel for biodiesel engines already in 1952 [117], historically it has not been a viable biodiesel feedstock due to its relatively high cost and high value as edible oil. Corn (maize) is a native grain crop of the Americas and is the third most important grain in the world after wheat and rice. Since only 7–8% of the grain is oil, corn oil is a bonus by-product. Processed corn oil is used extensively in the US as a fast food frying oil. Corn oil’s desirable properties include its mild nutty flavour, high levels of unsaturated fatty acids (MUFA, 26%; PUFA, 59%), low levels of saturated fatty acids (15%), very low levels of linolenic acid (0.5–1.7%), high levels of unsaponifiables (including phytosterols and tocopherols), and stability during frying. The food industry relies heavily on (hydrogenated) corn oils [106]. Processes for increasing throughput of corn for oil extraction are currently of great interest [118]. Corn oil production

Feedstocks for biodiesel production

161

may be increased by more efficient solvent extraction. In current dry grind processes, corn oil essentially passes through the process and remains in the resulting distillers dry grains with solubles (DDGS). Approximately 12 Mt/yr of DDGS are being produced in the US. Ethanol producers are investigating fractionating technology to remove corn germ (the portion of the corn kernel that contains oil) prior to the ethanol process. Some ethanol plants remove the remaining vegetable oil from dried distillers grains, a co-product of the ethanol process. Recovery of additional co-products, including corn oil, from the dry-grind process for ethanol takes advantage of membrane technology [119]. For instance, in PCT Int. Publ. No. WO 2008/039859 A2 Janes et al. (to VeraSun Energy Corp.) [120] describe a solvent extraction process from distillers dried grains with solubles to provide distillers meal (with high nutrient content for use as biodiesel supplement) and crude oil (for consumer use and biodiesel production), (see Fig. 5.5). Primafuel, Inc. (Signal Hall, CA) has recently launched its SMAART Oil corn extraction system. The profitability of both ethanol and biodiesel plants may be enhanced by extraction of industrial-grade crude corn oil from the ethanol process for use as an alternative feedstock for biodiesel plants [121, 122]. Ethanol producers may thus offer the biodiesel industry its nearest term opportunity for feedstock diversification. A 50 to 100 MMgy bioethanol plant can profitably be combined with a 1 to 3 MMgy modular biodiesel plant on extracted corn oil. The expected US production of bioethanol from corn of 15 Bgy in 2015 could generate almost 400 Mgy (non-edible) corn oil if only 0.5 lb of oil were extracted from each bushel

DDGS

Extractor

Desolventiser/ dryer

De-oiled DDGS

Evaporator Solvent Extraction system

Crude corn oil

Oil pre-treatment

Biodiesel production

Biodiesel

Biodiesel system Glycerin

5.5 Biodiesel production from distillers dried grains with solubles (DDGS).

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Biodiesel science and technology

of corn. In addition to the various extraction technologies, the quantity of corn oil could also be increased in the long term by producing more highoil corn varieties. While industrial-grade crude corn oil is not available on the spot market, it is offered at a price discount because of its composition. Compared with other vegetable and rendered oils, it is high in FFA content (12–17 wt%), as well as in waxes and other chemicals that make it unsuitable for human consumption. Consequently, for biodiesel application pre-treatment (acid esterification) is required. Corn oil does not give the cold-flow problems associated with the use of animal fat. Also combined corn ethanol-biodiesel production has been proposed [123]. Sesamum indicum L. (sesame) is a herbaceous oilseed crop of the Pedaliaceae family. The economically important crop is widely cultivated in many parts of the world (5 million acres), mainly in (sub)tropical areas (main producers: India, China, Myanmar) and has been adapted to semiarid regions. Sesame is currently being developed as a major oilseed crop in Turkey (South-eastern Anatolia Project). Global sesame production amounts to 3.3 Mt/yr. Sesame is widely used in food, and for nutraceutical and pharmaceutical purposes because of its high contents in oil (37–63%), protein (18–25%) and antioxidants (sesamin and sesaminol lignans) [124]. Fatty acid composition consists of C16 : 0 (11%), C18 : 0 (7%), C18 : 1 (43%) and C18 : 2 (35%). Sesame oil shows high oxidation stability. Although sesame oil methyl esters can successfully be used as biodiesel [125], sesame oil is in short supply and, consequently, highly priced. Moringa oleifera (Moringa, Murungai or drumstick tree) of the Moringaceae family and Moringa genus is an exceptionally nutritious vegetable tree growing rapidly in semi-arid (sub)tropical areas (India, Africa, Central and South America, Mexico, Malaysia, Philippines and Australia), which tolerates poor soil, drought, saline land and brackish water [126]. There are 48 varieties of Moringa, which is considered as one of the world’s most useful trees, as almost every part can be used for food. The crop yields 3 t seeds/ha. The seeds are relatively easy to crush using non-solvent based crushing techniques. Moringa seeds contain 38–40% oleic acid-rich oil. Its oil composition (C14 : 0, 0.1%; C16 : 0, 6.0%; C16 : 1, 1.5%; C18 : 0, 4.0–6.0%; C18 : 1, 71.2–74.0%; C18 : 2, 0.7%; C18 : 3, 0.2%; C20 : 0, 2.5–3.6%; C20 : 1, 2.2–2.5%; C22 : 0, 5.8–6.2%; C22 : 1, 0.1%; C26 : 0, 1.1%; SFA 22%, MUFA 77%, PUFA 1%; SN, 186 mg KOH/g; IV, 65.6 g I2/100 g) indicates an acceptable substitute for olive oil, although with a significantly higher FFA (as oleic acid) content (1.4%) [126, 127]. Moringa oil is considered to be a more sustainable biodiesel feedstock than jatropha oil by those who argue that sustainability is better served by feedstocks that can yield both food and fuel [128]. However, little research has been conducted on the tree’s potential as an oilseed crop. Moringa is more hardy compared with Jatropha

Feedstocks for biodiesel production

163

and its calorific value exceeds that of Jatropha. This little-known vegetable oil has the potential to be a next-generation agro-fuel feedstock, improving the food/fuel security. However, harvesting of difficult agro-fuel crops like Jatropha, castor bean and moringa needs to be addressed. Moringa could be grown initially as a feedstock for biodiesel production but has prospects as a food source. Moringa biodiesel has better oxidative stability than biodiesel from most other feedstocks, although the cloud point is similar to tallow and thus rather high. The tea plant (Camellia sinensis), cultivated mainly for its leaves, is a perennial, evergreen shrub, and produces large seeds which contain approximately 30% oil. The seeds of the other genera of Camellia, C. sasanqua or japonica, which are planted for their oils as well, have oil contents up to 60%. Tea seed oil is a by-product of the tea industry. Camellia or tea seed oil is a high-quality edible oil with a unique flavour and taste, and good storage stability. Being a high-oleic (59.0–61.3%), medium-linoleic (20.0–22.0%), and low-linolenic acid (0.25–0.35%) oil, and having a high antioxidant content, tea seed oil is a suitable feedstock for biodiesel production with low acid value (0.6–0.9 mg KOH/g), adequate IV (89.9 g I2/hg) and OSI (> 8.6 h) [129]. Solvent extraction of spent coffee grounds (15% oil; mainly C16 : 0, 51.4%; C18 : 0, 8.3%; C18 : 2, 40.3%; FFA 4–6%) yields a low-cost biodiesel feedstock with high antioxidant and sulphur levels [130]. 1.1 Mt/yr of good quality biodiesel (CP, 284 K) could eventually be produced from the waste coffee grounds around the world. Many other potential oils, e.g. from dikanut or oil bean seeds, walnut, poppyseed, cocoa butter (waste chocolate), etc., are unlikely to ever become serious feedstocks for biodiesels. Poppyseed (Papaver somniferum) oil is the edible oil obtained from the small, dark seeds of the opium poppy flower. The oil is similar in nature to soybean and hempseed oils and is highly valued (US$99/gal) for nutritional, medical and cosmetic applications. The oil composition of pumpkin seed (Cucurbitia maxima) is similar to that of cardoon. For the prospects of chokecherries, see Section 6.4.6.

5.6

Fish oils

Aquatic biomass comprises microorganisms (planktonic), macroalgae and fish. Annual world fish supplies amount to about 92 Mt/yr from capture fisheries (illegal fisheries not included and ocean stocks in decline) and 52.7 Mt/yr from marine and freshwater aquaculture production (mainly finfish and shellfish); 2008 data. Fish oils may be extracted from finfish such as anchovy, catfish, cod, dogfish, eel, hake, halibut, herring, mackerel, menhaden, pollock, sardine, shark, squid, trout and tuna. Such fish oils, farmed fish (salmon, tambaqui) oils, and marine mammal (dolphin, porpoise, whale) oils comprise

164

Biodiesel science and technology

some of the cheapest of oils [131, 132]. A disadvantage of aquatic biomass as compared to plant sources is frequently poor sensorial properties. Table 5.15 lists the main fish oils available in commercial quantities. Total world fish oil production is relatively small with approximately 1.1 Mt in 2002 (main producers: Chile, Peru, USA); some 100 kt/yr menhaden oil is being produced (at US$200 to US$650/t). The quantity of oil as a proportion of the body weight of the fish is significantly lower than those proportions found in oilseeds. Fish typically may contain 2–10% oil. Fish production is extremely seasonal. Fish oil is a by-product of the fish meal industry. In value terms, however, fish oil assumes much greater importance, in particular in its refined but unhydrogenated form. Crude fish oil prices in the US (2003) amounted to US$495/t. Worldwide uses for fish oil (2002) are as follows: aquafeed 56%, edible 30%, industrial 12%, and pharmaceutical 2%. Hydrogenation removes the highly unsaturated (n-3) fatty acids (EPA and DHA). Fish oil is a very complex mixture that contains high-boiling fatty acids, triglycerides, phospholipids, glycerol ethers, wax esters and fatty alcohols. Table 5.16 shows some total fish oil fatty acid compositions. For typical contents of principal fish oil fatty acids, see also ref. [133]. The compositions of fish oils vary not only with the type of fish, but also with factors including the season of the year (seawater temperature), the geographic location of the catch and the diet of the fish. These factors are interdependent. In spite of these variations, fish oils share important similarities in fatty acid composition which distinguish them from both vegetable oils and animal fats, namely, a wider range of chain lengths (C12-C26), higher degrees of unsaturation (D = 4–6) and low levels of odd-numbered and branched chain fatty acids [133], (see also Table 5.17). Fish oils may contain up to 40 components [134], as Table 5.15 Fish oils available in commercial quantities (after ref. [133]) Type

Main source(s)

Anchovy

Off South and South-West Africa, Chile, Peru and Mexico (Pacific Coast)

Capelin

Barents Sea, North Atlantic

Herring

North Atlantic, North Sea, Norwegian Sea, Pacific Ocean

Horse mackerel

South Africa, Pacific Coast of South America

Mackerel

North Atlantic, Pacific, North Sea

Menhaden

USA East Coast, Gulf of Mexico

Norway pout

North Sea, North Atlantic, Barents Sea

Sand eel

North Sea

Sardine/pilchard Off South Africa, Chile, Peru, Japan, Atlantic Coasts of Canada and USA Sprat

North Sea

Feedstocks for biodiesel production

165

compared to about 10 different fatty acids in the triacylglycerol structure of RSO and SBO. The significant contents of C14:0 (7–9%), C16:1 (5–12%) and C20:1 (usually 5–17%) differentiate fish oils from most vegetable oils and fats and from animal fats. Equally significant quantities of eicosapentaenoic acid C20:5 (EPA) and decosahexaenoic acid C22:6 (DHA) are unique to fish oils. The C22:1 fatty acid (n-11 isomer) is cetoleic acid (up to 20%), which differs from erucic acid (n-9 isomer). Fish oils are often characterised by very long-chain fatty acids (VLCFA). For instance, farmed tambaqui (Colossoma macropomum) fish oil contains C25/C26; in salmon oil PUFA (D ≥ 4) amounts to 28.5–41.7%, in sardine oil 22.0% has D ≥ 4. In the fish oil group, n-3 fatty acids (C20:5, C22:5, C22:6) are quite common. The high amounts of long-chain polyunsaturated fatty acids (up to 30%) in some fish oils (see Tables 5.16 and 5.17) cause high iodine values (>120 g I2/hg), low CN (30–40) and poor oxidation stability. The iodine values of menhaden fish oil (typically 160–180 g I2/hg) were directly calculated from fatty acid profiles by using reacting ratios between I2 and either the fatty acids bound to a triglyceride or the free fatty acids [135]. Satisfactory agreement with the traditional titration method was found. Table 5.16 allows two groups of oil types to be distinguished on the basis of their fatty acid profile: Group A oils, mainly from fish caught in seas in the southern hemisphere or southern part of the northern hemisphere, and Group B oils from fish of the northern part of the northern hemisphere [133]. In view of higher iodine value and polyunsaturate content, Group A fish oils are more susceptible to oxidation than Group B oils. Fish oils contain high levels of EPA (C20:5), DHA (C22:6) and omega-3 Table 5.16 Total fish oil fatty acid compositions (after ref. [133]) Type of fish

Degree of unsaturationa



SFA

MUFA

PUFAb

HUFAc

IVd

A:

33 29 30 33

24 28 32 29

17 20 15 18

8 9 10 9

150–200 141–212 158–193 178–200

19 26 19 20 24 18

57 54 47 42 47 47

8 6 7 8 7 10

6 6 9 13 8 9

94–164 95–160 125–147 140 136–167 144–173

Menhaden Sardine/pilchard Horse mackerel Anchovy

B: Capelin Herring Sprat Norway pout Mackerel Sand eel a

Calculated for total C14+C16+C18+C20+C22; wt%. Pentaunsaturated fatty acids. c Hexaunsaturated fatty acids. d g I2/hg. b

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fatty acids such as a-linolenic acid (C18:3) that are thought to have beneficial health effects. Omega-3 PUFAs may be extracted from zooplankton or krill [136], fish and other marine animals, or may be synthesised using microalgae (see Section 5.7). Euphasia superba oil is derived from Antarctic krill. EPA may also be sourced from both fish oil and microalgae [137]. The fatty acids found in crude catfish visceral oil are C14 : 0, 16 : 0-1, 18 : 0-3, 20 : 0-4 and 22 : 6, the predominant FAs being C18 : 1, 16 : 0, 18 : 2 and 18 : 0, with a total unsaturated FA in purified catfish oil of 67.7% [143]. The major fatty acids of visceral oil extracted from farmed Atlantic salmon (Salmo salar L.) are C16 : 0, 16 : 1n7, 18 : 1n9, 20 : 5n3 (EPA), 14 : 0 and 22 : 6n3 (DHA); SFA, MUFA and PUFA values are 31.7, 36.0 and 32.2%, respectively [144]. The FA profile of salmon visceral oil is similar to that of salmon filet and characterised by high EPA (1.64 g I2/100 g) and DHA (1.47 g I2/100 g) contents. Some marine oils find application for dietary purposes associated with cardiovascular/thrombotic diseases. Fish liver oils, such as cod liver oil (CLO) and hake (Merluccius hubbsi) liver oil, constitute a special class of oils, being used for medicinal purposes (source of vitamins A and D). CLO contains 7.5–9.0% C20:5 (EPA) and 10.0–12.0% C22:6 (DHA) (see Table 5.17). Cod Table 5.17 Fatty acid compositions (wt%) of some fish oils Fish oil

Composition

Cod liver

14:0(6.5), 16:0(16.0), 16:1(9.5), 18:1(26.5), 18:4(2.0), [138] 20:1(11.5), 20:5(10.0), 22:1(6.5), 22:5(1.0), 22:6(7.5) SFA 23.5, MUFA 55.0, PUFA 21.5; SN 193 mg KOH/g, IV 135 g I2/hg, CN 44.1

Menhadena

14:0(9.7), 15:0(1.4), 16:0(20.5), 16:1(12.6), 16:2(1.6), [139] 16:3(2.2), 16:4(1.7), 18:0(3.3), 18:1(11.1), 18:2(1.8), 18:3(1.6), 18:4(2.9), 20:0(0.4), 20:1(1.0), 20:4(2.1), 20:5(13.7), 22:1(0.8), 22:5(2.6), 22:6(9.2) SFA 35.1, MUFA 23.6, PUFA 39.1; SN 206 mg KOH/g, IV 176 g I2/hg, CN 33.2

Salmon

14:0(5.5–7.9), 16:0(15.3–22.3), 16:1(6.3–9.0), 17:0(0.3–1.0), 18:0(3.1–3.9), 18:1(10.4–17.8), 18:2(1.1–3.8), 18:3(0.6–1.1), 18:4(1.7–2.4), 20:0(0.2), 20:1(1.1–5.5), 20:2(0.2–0.4), 20:5(9.3–17.1), 22:1(0.4–5.9), 22:5(2.1–4.0), 22:6(11.3–20.1), 24:1(0.9) SFA 26.0, MUFA 38.0, PUFA 36.0; SN 191 mg KOH/g, IV 181 g I2/hg, CN 34.2

Sardine

14:0(8.1), 16:0(21.4), 16:1(8.9), 18:0(4.0), 18:1(18.5), [142] 18:2(16.0), 18:3(0.6), 20:2–4(1.0), 20:5(13.3), 22:4(0.9), 22:5(1.2), 22:6(5.9) SFA 33.5, MUFA 27.4, PUFA 39.1; SN 204 mg KOH/g, IV 148 g I2/hg, CN 39.6

a

Herring family.

Reference(s)

[140, 141]

Feedstocks for biodiesel production

167

liver oil is very expensive (and consequently often adulterated with rapeseed oil). Intracellularly synthesised eicosapentaenoic acid (EPA) is less expensive when obtained from Phaeodactylum tricornutum than from cod liver [145]. FTIR may be used for rapid analysis of FFAs in fish oil biodiesel feedstock covering the range of 0–6.5% FFA [146]. AOCS Method Ce 1i-07 analyses fatty acids in marine and other oils containing long-chain PUFAs by GC; see also ref. [134]. The primary potential source of biodiesel feedstock from the fisheries and seafood (aquaculture) processing sector is fish oil. Fish oil is currently being used or evaluated as feedstock for biodiesel blends in Norway, Alaska (US) and Nova Scotia (Canada). To be cost-effective, biodiesel has to be produced locally, or it will be just as expensive as imported diesel. Biodiesel production can utilise marine oils or crude unprocessed fish oil which is removed from waste materials (fish processing discards). Statoil Biodiesel produces yearly 4.5 ML biodiesel based on Norwegian fish oil from the waste of salmon farms (salmon methyl ester), which is probably used to blend 5 vol% rape biodiesel. Herring oil biodiesel is solid. The European Enerfish project (project leader: VTT, Finland) aims at demonstrating the commercial feasibility of transforming fish waste into biodiesel; pilot plants (120 t/d) are planned near pangasius (P. hypophthalmus) fish farms in Vietnam. In North America two significant projects successfully utilise fish oil as feedstock to biodiesel. Ocean Nutrition Canada Ltd./Wilson Fuels (Bedford, NS) produces 5 ML/yr biodiesel from the less desirable saturated waste fish oil residues. Unisea Fisheries (Dutch Harbor, AK) produced fish oil biodiesel for several years. In the framework of the Alaska Fish Oil Biodiesel Project, the Alaskan commercial fishery industry currently produces 8 Mgy of fish oil (market value US$0.75 to US$1.50/gal in 2003), but with the capacity to produce up to 21 Mgy using oil of the fish that are harvested (excess oils now being dumped) [147, 148]. The potential of fish processing discards as feedstock for biodiesel production via enzymatic transesterification was also evaluated [149] (see Tables 10.1 and 10.2). Rendering is the most common process to extract usable oils from fish wastes. Fish oil has valuable properties for animal feed, aquaculture, pharmaceutical and cosmetics, and is usually worth more than biodiesel. The economic potential of using fish oil as a feedstock for biodiesel production is enhanced in more remote areas that have a locally produced supply of crude fish oil. In British Columbia, fish oils are derived from the rendering and recovery of waste by-products resulting from value-added seafood processing. The tasks of collecting the raw wastes and of extracting usable oils from them are capitalintensive and complex operations. Consequently, in British Columbia it is unlikely that a potential biodiesel manufacturer would find it strategically or economically viable to invest in a purpose-built rendering/recovering facility for producing an in-house source of fish oil feedstock from raw waste.

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One of the factors to consider is the shelf-life of the fish oil supply. Because of the high level of long-chain omega-3 fatty acids, fish oils are readily oxidised [150]. Consequently, commercial additives are needed to improve the oxidative stability of fish oil biodiesel to meet standard quality specifications.

5.7

Algae mass culture systems

Photosynthetic organisms growing in aquatic environments include macroalgae (‘seaweed’), microalgae (microscopic organisms) and emergents (plants growing partially submerged in bogs and marshes). Macro- and microalgae are aquaculture products which can be found in both marine and freshwater environments. Microalgae growth covering 700 000 km2 (twice the size of Germany) has been observed in the Arctic Ocean [151].

5.7.1 Microalgae Microalgae comprise a vast group of photosynthetic, heterotrophic organisms which have an extraordinary potential for cultivation as energy crops. Photosynthetic algae are dominant producers in aquatic environments, account for a substantial proportion of global O2 production and CO2 fixation, are a component of feed for aquaculture and produce numerous valuable compounds such as fats, oils, sugars, pigments and other functional bio-active compounds. Microalgae represent an immense range of genetic diversity and can exist as unicells, colonies or extended filaments. They grow under the widest possible variety of conditions (from freshwater to extreme salinity, from moist earth to desert sands). Microalgae are microscopic aquatic plants that carry out the same process and mechanism of photosynthesis as higher plants in converting sunlight, water and carbon dioxide into biomass, lipids and oxygen. However, algae production does not require fresh water or arable land used for cultivation of food crops. Most microalgae are obligate photoautotrophs and their growth is strictly dependent on the generation of photosynthetically derived energy. The use of algae is of great interest for their higher photosynthetic activity compared with terrestrial plants. Certain algae (e.g. Chlamydomonas reinhardtii) are effective in the production of hydrogen and oxygen through the process of biophotolysis, while others produce starch (e.g. green algae), lipids (e.g. diatom algae) or long-chain hydrocarbons (e.g. Botryococcus braunii), suitable for direct use as highenergy liquid fuels. It should be remembered that the petroleum of today is derived from prehistoric biomass, including algae. For example, the deposits of oil pumped from the North Sea consist partly of decomposed haptophyte algae (Coccolithophorids). The challenge is now to grow and transform algae into biocrude within days rather than millenia.

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Algae are commonly categorised in nine divisions: the largest groups are diatoms (Bacillariophyceae), green algae (Chlorophyceae), blue-green algae (Cyanophyceae) and golden-brown algae (Chrysophyceae). Microalgae are unicellular and are the most primitive form of plants. While the mechanism of photosynthesis in microalgae is similar to that of higher plants, they are generally more efficient converters of solar energy because of their simple cellular structure. Algae can be 10% efficient at converting sunlight into fuel, as compared to the 1–2% efficiency for ethanol from maize. Moreover, because the cells grow in aqueous suspension, they have more efficient access to water, CO2 and other nutrients. Consequently, microalgae are capable of producing at least 30 times the amount of oil per unit area of land compared to terrestrial oilseed crops (see Table 6.1). Algae can be a promising feedstock as the fatty acid yield on a unit area basis is 15–20 times higher than for palm and over 200 times higher than soybean. Microalgae are sunlight-driven cell factories that convert CO2 to potential biofuels, foods, feeds and high-value bioactives. The approximate molecular formula of microalgal biomass is CO0.48H1.83N0.11P0.01. Microalgal biomass contains approximately 50% carbon by dry weight, which is typically all derived from carbon dioxide. Producing 100 t of algal biomass requires roughly 183 t of carbon dioxide. Algal biomass contains carbohydrates, proteins and natural oils. Cultivated microalgae are a minor source of food for humans and animals, and yield a wide range of chemical compounds, such as phycocolloids, used in industry, food technology and pharmaceuticals. Similar to fish oils and animal viscera, many cultured microalgae are potential sources of high-value nutraceuticals and pharmaceuticals such as polyunsaturated fatty acids (PUFAs) and other bioactive compounds with a product value of US$100–1000/gal, including health food. The majority of the commercial algal cultivation plants (3–500 t/yr) are located in Asia [152]. Total worldwide production is a few thousand tons of algal biomass per year. Most of the commercially produced algal biomass is marketed as health food or dietary food supplement (overproduction scenario). There are also algae cultivation ponds across the US (in Pennsylvania, Tennessee, Florida, Oregon, California and Arizona). The world’s largest algae farm (108 acres), operated by the Earthrise Nutritionals facility (CA), produces cyanobacterial biomass for food. Certain algae contain 30% omega fatty acids. Commercially-grown algae like Spirulina are high in protein and starch but low in fat. A few high-fat species of algae like Haematococcus are promising, but the fats (at prices of around US$1200/lb) are too expensive for fuel purposes. Algae can potentially provide different types of renewable biofuels, namely: photobiologically produced biohydrogen [153, 154]; methane from thermal gasification or anaerobic digestion [155]; bioethanol by subsequent fermentation [156]; bio-oil by pyrolysis [157]; and biodiesel by heterotrophic fermentation

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[158] or from microalgal oil by transesterification [156, 159–166]. Microalgae are very efficient in converting a waste (zero-energy) form of carbon (CO2) into a high-density liquid form of energy (natural oil). Biodiesel production applies exclusively to the natural oil fraction. Microalgae are among those species which produce more of the right kind of natural oils for biodiesel applications. Microalgae are an alternative source of lipids, which can be readily converted to biodiesel, but without competing for arable land. Only step-change solutions, such as efficient production from algae, will allow biodiesel production meeting much more than ~10% of the diesel market. Starting with algae production eliminates the trading and handling cost for the crude oil. Algal biomass may also be used for production of steam or electricity by direct combustion. The concept of algal biomass as a fuel extender in power plants is being pursued especially in Japan. Oil obtained from the marine microalga Dunaliella tertiolecta has a calorific value of 36 kJ/g (compared with 45 kJ/g for fossil fuel and 28 kJ/g for coal) [167]. Oil extraction from algae may be achieved by expeller/pressing (yielding 70–75% of oils out of dried algae), hexane solvent method (yielding 95% of total oil present in combination with cold press), or supercritical fluid extraction (100% oil recoverage). The algal oil quality and yield depend on the algae species and vary widely depending on ecological habitat. Within the US Biofuels Program the DOE-funded Aquatic Species Program Biodiesel from Algae (or ASP; operated between 1978 and 1996 in reaction to the 1973 oil crisis) has aimed at demonstrating the feasibility of producing biodiesel from high lipid content algae grown in open ponds, utilising fossil CO2 (flue gas) from coal-fired power plants [163]. Some 3000 highly oleaginous strains of algae were screened and isolated in an attempt to find high-oil producing algae that grow under severe conditions of T, pH and salinity. Many of the algal species can grow in brackish, non-potable water or in the open sea, i.e. water containing high salt levels. Some 300 species of high oil producing algae (originating mainly from native shallow, inland saline habitats in southwestern US), mostly green algae (especially in freshwater) and diatoms (in marine and fresh water), were selected and their capabilities were determined. Not all algal species that looked promising in laboratory tests were robust enough under field conditions. The best choice of microalgae is still an open question. No one single species seems to meet all the needs of the algal biodiesel technology. The strains most favoured by NREL were Bacillariophyceae and Chlorophyceae. Diatom algae need silicon in the water to grow; green algae require nitrogen. Whereas certain algae strains are very tolerant to temperature fluctuations, diatoms have a fairly narrow temperature range. The NREL programme was terminated in 1996, largely because at that time crude oil prices were far too low for algae to compete. Today’s higher oil prices

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171

make competition easier. Moreover, biotech advances and new genomic and proteomic techniques have enhanced our understanding of the mechanisms involved in algae oil production. While some types of algae can produce as much as 60 wt% of oil, in the necessary conditions of starvation for nutrients they lose their ability to grow and reproduce. By overcoming this problem oil production could be dramatically increased and drive down prices. The primary ingredients of algal life are sunlight, CO2 and water. Although it is common understanding that algae use CO2 for their photosynthesis process, it has recently appeared that some algae (e.g. the marine cyanobacterium Synechococcus WH 8102) use oxygen [168]. Unlike other crops, microalgae grow extremely rapidly and many are exceedingly rich in oil. Algae produce by cellular division. Algae grow in a wide variety of climates and conditions (including wastewater treatment facilities). Areas targeted for the highest production per hectare of algae are desert climates, which are largely unused and unsuitable for traditional crop cultivation. One of the great strengths of algae is the ability to grow robustly in brackish water. Table 5.18 summarises Table 5.18 Main characteristics of microscopic algae biomass for biodiesel production Advantages: ∑ Great variety in natural and GM algae strains ∑ Sustainable and carbon neutral technology (CO2 sequestor) ∑ Turns pollution into energy ∑ Very high energy potential ∑ Home-grown source of energy ∑ Contributes to energy security ∑ Avoids use of scarce fossil fuels ∑ Rapid reproduction ∑ Day-after-day harvesting ∑ High per-acre yield ∑ High oil contents ∑ No competition with food crops ∑ No competition for agricultural land use (wastelands, deserts) ∑ No competition for scarce sweet water ∑ Robust growth in brackish and marine waters ∑ No sulphur, non-toxic, highly biodegradable biofuel Disadvantages: ∑ No affordable processing method ∑ Danger of culture crashing (microbe contamination) ∑ Limited commercial availability ∑ High PUFA (D ≥ 4) contents Challenges: ∑ Scaling up of algae production methods ∑ Availability of concentrated CO2 ∑ Large–scale harvesting and dewatering ∑ Improved extraction methods

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Biodiesel science and technology Table 5.19 Oil content of some microalgae (adapted from ref. [169]) Microalga

Oil content (% dry wt)

Botryococcus braunii Chlorella sp. Crypthecodinium cohnii Cylindrotheca sp. Dunaliella primolecta Dunaliella tertiolecta Isochrysis sp. Monallanthus salina Nannochloris sp. Nannochloropsis sp. Neochloris oleoabundans Nitzschia sp. Phaeodactylum tricornutum Schizochytrium sp. Tetraselmis suecica

25–75 28–32 20 16–37 23 37 25–33 > 20 20–35 31–68 35–54 45–47 20–30 50–77 15–23

the main characteristics of microalgae as a biodiesel feedstock. Unlike other sources, such as soybean or rapeseed, algae can be harvested day after day. Advantages of microalgae are higher photosynthetic efficiency, higher biomass production and faster growth compared to other energy crops. Algae reproduce more rapidly and consume more CO2 than any other form of plant life. Microalgae commonly double their biomass within 24 h. Biotechnology has allowed development of modified algae strains with bio-yields three times higher than naturally. Lipid productivity of many microalgae greatly exceeds that of the best producing oil crops (see Table 1.10). Oil content in microalgae can exceed 80% by weight of dry biomass [155]. Oil levels of 20–50% are quite common (Table 5.19). Diatom algae typically contain approximately 50 wt% oil. Microalgae with high oil productivities are desired for producing biodiesel. Depending on the species, microalgae produce many different kinds of lipids (though simpler than fish oils), hydrocarbons and complex oils. Renaud et al. [170] described the fatty acid composition of 18 species of microalgae from tropical Australian marine and freshwater environments, which mostly contained lipid contents between 15 and 20 wt% of dry matter. Good quality oil (low P and neglible S content) was obtained by direct extraction from such microalgae. Table 5.20 shows that the highest PUFA percentages were found in cryptophytes (in the range of 65.8–75.2% of total fatty acids) and prasionophytes (52.2–61.6%). An overview of genomic and biomolecular techniques for enhancing lipid yield in tropical microalgae is available [171]. Marine algae cultivation in coastal waters (e.g. in Bretagne, Hawaii, Singapore) minimises the impact on agricultural land and freshwater supplies

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Table 5.20 Fatty acid compositiona of some tropical Australian microalgae (after ref. [170]) Species

SFA (%)

MUFA (%)

PUFA (%)

PUFA (D ≥ 4) %

Bacillariophyceae (diatoms) Cryptophyceae Prasinophyceae Prymnesiophyceae Rhodophyceae

25.8–33.0 14.4–22.6 21.7–24.7 25.9–30.3 33.9

23.2–41.4 6.0–11.0 12.7–16.5 11.3–20.5 18.7

26.1–47.2 65.8–75.2 52.2–61.6 48.4–56.4 43.6

13.5–29.9 35.9–49.5 27.6–38.4 28.9–43.9 10.7

a

Percent of total fatty acids (w/w).

Table 5.21 Some algae species under consideration as a mass oil producing crop Botryococcus braunii Dunaliella tertiolecta Euglena gracilis Isochrysis galbana Nannochloris sp. Nannochloropsis salina Neochloris oleoabundansa

Phaeodactylum tricornutumb Pleurochrysis carteraec Prymnesium parvumd Scenedesmus dimorphusa Spirulina sp. Tetraselmis chui e Tetraselmis suecica

a

Green alga (Chlorophyceae). Diatom. c Prymnesiophyceae. d Toxic. e Marine unicellular. b

and avoids the conversion of rainforest into vegetable oil plantations. Examples of salt-tolerant microscopic algae (plankton) are the diatom Phaeodactylum tricornutum (Bacillariophyceae), Botryococcus braunii and Dunaliella tertiolecta. Japan operates a national research project for mass cultivation of oil producing Botryococcus [172]. Locally isolated strains of tropical marine microalgae were screened in Singapore for cellular lipid content for the development of an indigenous biodiesel feedstock [170]. Table 5.21 lists various algae species which are being considered for oil production. Not all algal oils are equally suitable for making biodiesel, but suitable oils commonly occur. In view of the composition of many microalgal oils, most of them are unlikely to comply with the European biodiesel standards. A drawback of the algal oils in Table 5.20 is their invariably high PUFA (D ≥ 4) percentage. These oils might require partial catalytic hydrogenation to reduce the extent of unsaturation (see Section 15.3.2). Plant biotechnology is a field that is only recently coming into its own. Within this field, algae research is still largely unexplored. An important research topic is improving oil production in algal organisms and manufacturing the metabolism of algae. Although overall rates of oil production are lower

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Biodiesel science and technology

during periods of nutrient deficiency, no simple means appears to exist for increasing lipid production without a penalty in overall productivity due to a slowing down of cell growth. Possibly, a net increase in total oil productivity may be achieved by carefully controlling the timing of nutrient depletion and cell harvesting. High CO2 sequestration yields are required [173]. Finding key enzymes in the lipid synthesis pathway whose level of activity in the cell influences the rate at which oil forms is critical to understanding the mechanisms for controlling oil production. The enzyme acetyl CoA carboxylase (ACCase), isolated from a diatom, which catalyses a key metabolic step in the synthesis of oils in algae, is considered to be such an enzyme. Biochemistry and physiology of oil production in algae mass culture systems require further development on a fundamental level in order to improve the performance of existing organisms. Production of algal oils requires an ability to inexpensively produce large quantities of oil-rich microalgal biomass. Producing microalgal biomass is generally considered more expensive than growing crops. The challenges are several (Table 5.18) and lie in the growth, harvesting and oil extraction rather than in the chemistry of converting algal oil products to fuels. Many fundamental technological questions still need to be solved: where to grow algae; which strains to select; how to boost productivity while keeping a sensitive culture robust and stable; and how to design the most cost-effective culture ponds. Large-scale harvesting and dewatering are major issues. Centrifugal algae harvesting is an option [174]. The cost of harvesting can amount to some 30% of the total algal production cost. Extraction methods (‘milking the algae’) have also yet to be perfected. Origin Oil Inc. (Los Angeles, CA) has developed a one-step algae harvesting/oil extraction process. It may reasonably be expected that the various challenges may be overcome given the sheer diversity of algae species. With more than 35 000 species of algae described scientifically and as many as 100 000 presumed, finding the most suitable strain is not an easy task. There will not be just one magic strain. Different species are likely to be needed for every location to ensure that a consistent amount of oil is produced all year round, despite fluctuations in temperature and sunlight. The most suitable strains are most likely to be found close to proposed algae cultivation sites. In all likelihood, there is a species that can be optimised for a given algae production system.

5.7.2 Microalgae technology The useful energy capture of growing crops represents less than 1% of sunlight absorbed. However, growing algae to make biofuel presents potentially a different proposition. The much promoted energy re-evolution from fossil power to algae/solar power passes through engineering of high-volume microalgae production systems.

Feedstocks for biodiesel production

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Growth media are generally inexpensive and must provide the inorganic elements that constitute the algal cell (mainly N, P and sometimes Si). Photosynthetic growth requires (sun)light, CO2, water and inorganic salts. Carbon dioxide must be fed continuously during daylight hours. Temperature must remain generally within 293 to 303 K. Seawater supplemented with commercial nitrate and phosphate fertilisers and other micronutrients is commonly used for growing marine microalgae. Mixotrophic growth reduces the need for light and reduces the use of CO2, which is expensive in large-scale culture. Heterotrophic growth of microalgae could eliminate the requirements for light, and thus may offer the possibility of greatly increasing the algal cell concentration and productivity on a large scale. However, only a few industrial heterotrophic processes are known, possibly due to a limited number of available heterotrophic algal species. Algae technology is unique in its ability to produce a useful, highvolume product from waste CO2, e.g. as generated in power plants. There are significant barriers to the large-scale production of algae. These include maintaining mass culture stability, developing low-cost algae harvesting methods and optimising strains for energy yields. For technically feasible and practical cultivation of microalgae, algae farms commonly produce in various types of outdoor open ‘raceway’ ponds, enclosed open-ponds or photobioreactors (including plastic algal bags). Fermenters are preferred for heterotrophically growing algae (Table 5.22). For an overview of microalgae production systems, see ref. [175]. Fundamental operational issues of raceway production ponds, in which algae, water and nutrients circulate around a racetrack with paddlewheels providing the flow (Fig. 5.6), are the effects of fluid flow patterns, light intensity, dissolved oxygen levels, temperature, pH and algae harvesting methods. The open ponds are shallow to keep the algae exposed to sunlight. Open ponds require relatively low investment but are sensitive to rainfall and drought, temperature fluctuations, high evaporative losses and pollution (e.g. takeover by low oil strains); introduction of CO2 is somewhat problematic. The use of simple open ponds was favoured by the US Aquatic Species Program. The view was held that the factors that most influence cost are biological, and not engineering related, if low cost ponds are used. There is no one ideal algae culture system. Table 5.22 Microalgal biomass production modes Technology a

Open ponds , photobioreactors Fermentation tanks a

b

Including enclosed open-ponds. Including tubes and algal bags.

b

Growth mechanism

Energy supply

Photoautotrophic Heterotrophic

hn, CO2, nutrients Sugars

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Water nutrients

Motorised paddle

Algae

Waste CO2

5.6 Open raceway pond for algae production (after ref. [163]). Table 5.23 Main characteristics of open-pond cultivation of photosynthetic microalgae Advantages: ∑ Exploitation of natural sunlight ∑ Relatively low investment Disadvantages: ∑ Pollution ∑ Seasonal and diurnal variations in conditions (T, hn) ∑ High evaporative losses ∑ Difficult prediction of growth rates and culture densities ∑ Self-shading ∑ Low cell densities ∑ Inefficient harvesting ∑ Relatively low biomass productivity ∑ Applicable to few genera (e.g. some diatoms)

Culture conditions determining growth rate, biochemical and fatty acid composition comprise aeration rate and irradiance, culture temperature, cell and nutrient concentrations. For example, the effect of light intensity on the growth of two marine microalgae, the eustigmatophyte Nannochloropsis oculata and the chrysophyte Isochrysis sp. has been reported [176]. Commercialscale cultivation of photosynthetic microalgae in large, open outdoor ponds has a number of disadvantages, as listed in Table 5.23. Phototropic algae production is preferably located in areas with higher inolation. One of the challenges with algae systems is when the algae density is high, as light then only penetrates a few centimetres into the culture. Self-shading severely limits biomass production, and low cell densities prevent efficient harvesting. Large-scale cultivation of microalgae in open ponds is restricted to a small subset of genera that includes Spirulina and Dunaliella.

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Algae may be grown rapidly in ponds using fertilisers with subsequent transportation to nitrate-poor ponds to increase the oil production. Under mixotrophic conditions some microalgae are known to grow rapidly and to have a higher growth rate than under photoautotrophic conditions [177]. Suitable zones for algae production based on climate, land, water and fossil CO2 availability were identified in the southwestern USA, but are extendable to other geographical areas. Within ASP the concept of longterm, reliable large-scale production of algae in 1000 m2 outdoor open-pond systems in several US states (e.g. California, Hawaii and New Mexico) has been proven. Using native species of algae and careful control of pH and other physical conditions for introducing CO2 into the ponds allows very efficient (>  90%) utilisation of injected CO2 in large open ponds. Target levels of 50 g of algae/m2/day can be achieved under optimum conditions. Recently, most development work is focusing on photobioreactors (PBRs). Closed-loop or bioreactor systems grow algae in a controlled environment using a wide variety of production processes like plastic bags, tubes, or fermentation reactors. A tubular photobioreactor consists of an array of straight transparent tubes that are usually made of plastic or glass. Horizontal, parallel straight tubes are sometimes arranged like a fence. Also helical coil tubular photobioreactors have been described. Closed photoreactor systems, either flat panels (with higher, but more energy-intensive production) or tubular (l = 100–200 m, characterised by a relatively lower production), require a much smaller surface than open cultivation systems, and process control and optimisation of algal growth are improved. Closed-loop systems provide the advantage of additional control over seasonal temperature changes, evaporation losses and contamination by undesired algae strains. An advantage of such closed systems is that they protect the cultivation of a monoculture of algae. The University of Wageningen Research Centre (WUR) is developing algae for biofuel production using a variety of flat panel reactors. In a transparent tank or algal bag system algae are essentially exposed to light only in a few centimetres near the tank wall or surface where they react with CO2 and nutrients and photosynthesis occurs. Algae growth is limited in areas in which light cannot penetrate. However, the dark area allows more complex protein building to occur within the algae. Narrow diameter tubular reactors allow light to penetrate to the centre of the tube. The algae are constantly recirculated from the tube to a tank (for protein building). In tubular reactors, CO2 is supplied at entry. As photosynthesis generates oxygen, high concentrations of dissolved oxygen build up along the tubes. In combination with intense sunlight this may result in photooxidative damage to algal cells and consequently retarded algal growth. Degassing zones are needed as oxygen cannot be removed within a photobioreactor tube. Photobioreactors also suffer from internal wall growth of some algae. In order to reduce the problems of algae fouling and to avoid frequent tube

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cleaning, the flow rate through the tubing needs to be sufficient to induce turbulent flow. Nannochloropsis and Chlorella are species grown in tubular reactors to extremely good densities. Table 5.24 shows the benefits of a tubular reactor. Typically, the culture density of algae produced is 10–20 times greater than bag culture. Tubular reactors can be mounted vertically, horizontally, indoors or outdoors. Cultures are easily kept hygienically. Biomass recovery from photobioreactor-cultured broth costs only a fraction of the recovery cost for broth produced in raceways. Photobioreactors provide a controlled environment that can be tailored to the specific demands of highly productive microalgae to obtain a consistently high oil yield. Investment costs are higher than for open ponds. An energy balance model PBR-based algae system is needed. Dutch AlgaeLink NV is marketing industrial-scale closed algae photobioreactors as from the third quarter of 2007. The tubular systems (l = 36 m, F = 0.64 m), connected by a pumping system, are autocleaning with extensive monitoring and scalable for producing from 1 to 100 dry-weight tons of biomass per day. Demonstration plant produced algal oil costs only US 7 cents/L. Solix Biofuels (Colorado State University) has developed the Solix AGS photobioreactor production system; Varicon Aqua Solutions, Ltd. (Malvern, UK) and Scottish Bioenergy Cooperative Ventures (St. Cyrus, UK) are other technology providers. Culturing Solutions, Inc. (Pinellas Park, FL) operates a commercially available continuous algae production technology (BioFence) based on photoreactors. Large-scale commercial production of microalgae makes use of both raceway ponds (open culture systems) [163, 178] and tubular photobioreactors [179]. The largest raceway-based biomass production facility occupies a pond area of 440 000 m2 (108 acres) [155]. Raceways are perceived to be less expensive than photobioreactors, because they require a lower capital cost to build and operate. However, they have a considerably lower biomass productivity compared with photobioreactors. At a biomass production of 10 kt/yr, the production cost of one kg of microalgal biomass is about US$0.47 and US$0.60 for photobioreactors and raceways, respectively. At 30% oil content, the cost of biomass for providing a litre of microalgal oil would be US$1.40 and US$1.81 for photobioreactors and raceways, respectively. Oil Table 5.24 Key benefits of a tubular algae bioreactor ∑ ∑ ∑ ∑ ∑ ∑ ∑

Maximum light efficiency Space saving Reduced labour and handling problems Dramatically reduced fouling Reduced incidence of culture crashing Closed, controlled and automated systems Simple control of environmental parameters

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recovered from biomass produced in photobioreactors is estimated to cost US$2.80/L [169], compared with US$0.52/L for CPO (2006). Reduction of the production cost of algal oil from about US$2.80/L to US$0.48/L is a strategic objective. The level of cost reduction is substantial, but attainable. Recently (April 2008) the price of crude algae oil was quoted as US$3.85/ gal. For algal biodiesel production costs, see Section 9.5. Locating algae processing plants strategically adds to their efficiency. Microalgae can be used directly in carbon capture. Microalgae have the highest carbon fixing rates of any plant. Algae can be produced in large volumes in nutrient-rich waste streams such as at the settling ponds of standard effluent management systems (EMS). Already in 1976 a combined wastewater treatment facility/fuel production system based on microalgae growing in open ponds was evaluated at the University of California Berkeley’s Richmond Field Station. Since then, the DOE has shifted emphasis to dedicated algae farming using vast areas with continuously operated open ponds of raceway design into which some source of waste CO2 (e.g. from fossil fuel-fired power plants) could be efficiently bubbled and captured by algae (Fig. 5.7). Locating algae facilities next to flue gas producing power plants or to other manufacturing plants (e.g. breweries, natural gas purification units) could sequester CO2 emissions to help grow algae in their photosynthesis. Most carbon capture research focuses on removing CO2 gas from power plant waste streams, which contain around 10%. Power plant CO2 capture is inevitably cheaper than air capture. Biomass produced by algae can be used for fuel, creating a carbon neutral scheme. The concept of a coal-fired power plant adjacent to an algae farm provides excellent synergy to recycle CO2 from coal combustion into a usable liquid fuel. Integrated processing technologies involving photobioreactors may tie algae production with nutrient sources from wastewater treatment (from human, animal and agricultural streams) and power plant emissions (Fig. 5.8). Eni refinery (Gela, Sicily) has recently started up an experimental plant (both open ponds and photobioreactors) for biofixation of fossil CO2 in air and wastewater effluents by microalgae for biodiesel production. Dow Chemical/Algenol Biofuels intend using CO2 emissions at Dow Freeport, TX, to produce bioethanol in algae-filled bioreactors. Closed bioreactor designs for algae production have been investigated in Japan, the US, France, Germany and The Netherlands. A suitable profile for freshwater algae cultivation is to put the cheap plastic tube bioreactors over sunny non-productive land adjacent to ample carbon sources such as smokestacks, farm runoff and sewage close to where the fuel is needed. GreenFuel’s Emissions-to-Biofuels™ (E2B™) technology uses algae to recycle CO2 coming out of the smokestack of the Arizona Public Service Company (APS) Redhawk (Arlington, AZ) 1040 MW power plant [180]. CO2 emissions are trapped and transferred to special containers (proprietary

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CO2 recovery system

Algal/oil recovery system

Fuel production

5.7 Algae farm consisting of a waste CO2 source and open raceway algae ponds (after ref. [163]).

Wastewater treatment plant

Nutrients

Power plant

Photobioreactor

Algal biomass

Biohydrogen

Methane Algal biodiesel Bioethanol

Bio-oil

5.8 Integrated algal biomass processing technology within a biorefinery context.

photosynthesis algal bioreactor system) holding algae. After harvesting the algae, its starches are turned into ethanol, its lipids into high-quality biodiesel, and its proteins into high-grade feed and nutritional supplements for livestock, or else are returned to the algae farm as nutrients (Fig. 5.9).

Feedstocks for biodiesel production CO2

181

Nutrients

Algae

Harvesting

Starch

Lipids

Proteins

Bioethanol

Biodiesel

Feed

5.9 Integrated algae farm.

E2BTM technology allows power plants to significantly reduce CO2 and NOx emissions (by 45% and 90%, respectively) to generate carbon credits, and produce clean, renewable biofuels. In a similar approach, Valcent Products, Inc. (El Paso, TX) has recently developed a commercial-scale bioreactor for algae-to-biofuels, consisting of a series of closely spaced vertical photobioreactors constructed of thin film membranes allowing high levels of light penetration (up to 1–1.5 inch) [181]. This so-called Vertigro biofuel oil/CO2 sequestration technology is ideal for location adjacent to heavy producers of CO2, such as coal-fired power plants, refineries or manufacturing facilities (cement factories, steel mills, etc.), can be deployed on non-arable land and requires very little water (only the amount bound to algae) due to its closed circuit process which eliminates cross-contamination by other algae species. The dynamic, high surface area system produces much higher algae growth rates than conventional static systems. The continuously operated test bed facility yields 4000 barrels of oil per acre, per year, at a cost of US$20 per barrel. In other words, 1000 acres have the potential of producing 4 million barrels per year, with significant CO2 green credits and other commercial products. In this way, about onetenth of New Mexico would suffice for the total energy needs of the US. Lipids produced, e.g. for jet fuel or diesel fuel, can be tailored on the basis of the algae species. Algae ponds the size of Maryland, US (3.4 Mha) would be able to supply the global aviation fuel needs (some 85 Bgy) [182]. In 2006 LiveFuels/Sandia National Laboratory formed a US national alliance dedicated to transforming algae into biocrude by the year 2010. Hurdles to be overcome for commercialisation include breeding various strains of algae and driving down the cost of harvesting and extraction of fats and oils. Theoretically, algae can yield 1000 to 20 000 gallons of oil per acre. ConocoPhillips (in cooperation with C2B2 – Colorado Center for

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Biorefining and Biofuels) is actively involved in strain collection, cultivation and extraction technologies of algae. In order to improve production economics, biotech company Solazyme, Inc. (San Francisco, CA) is modifying algae to grow in the dark in fermentation tanks, sustained by sugar, rather than photosynthetically in the open. See also Section 9.5. PetroSun Biofuels’ (PetroSun Inc., Rio Hondo, TX) pilot algae farm in Opelika, AL, has reached algal oil production between 5000 and 8000 gal/acre/yr. After extraction, the residual algae biomass can be made into ethanol or other products. In early 2008 PetroSun Biofuels, Inc. started the first commercial scale open-pond algae farm operations (157 separate ponds on 1100 acres) in the US for the production of oil for biodiesel feedstock near South Padre Island (TX). The open-pond system uses salt water and native marine algae species. The potential biodiesel production will be 4.4 Mgy. With the expected production of 32.6 t/ha/yr of diesel and 116 t/ha/yr of other biomass this corresponds to a photosynthesis efficiency of 4.7%, which is better than crop-based fuel production by a factor of 10–20. Algae farms and oil extraction plants are also planned in Alabama, Louisiana, California, Sonora (Mexico), Brazil and Australia. A pilot-scale algae-oil production facility (10 ha raceway) is being built on Torrens Island (South Australia) by Algal Fuels Consortium’s Microalgal Research Alliance. The novel, efficient and low-cost hybrid-algae production system (HAPS) to continuously extract oil and cellulose sugars from oil-bearing microalgae, developed by Biotech Research, Inc. (Ensenada, Mexico), allows conversion into biodiesel and cellulosic ethanol. The method also eliminates the need to mechanically dry and press-extract the algae oil. Green Star Products, Inc. (Chula Vista, CA) has operated a 40 kL HAPS demo plant in Butte, MT, through 2007–08. The unit, which is basically a covered pond system that combines the controlled environment of a photoreactor with the lower costs of an open-pond system, was robust enough to grow a strain of algae (ZX-13) at an outdoor temperature of 255 K. A commercial-sized harvesting from a pilot-scale algae pond (12 000 gal of water) was reported by the Center of Excellence for Hazardous Materials Management in Carlsbad, NM. Expectations are here that algal oil can be produced for approximately US$80/barrel. This is far below estimates of the US Defense Department of the current production cost of algae oil (in excess of US$20/gal). Appropriate climate, land, water and CO2 resource availability could easily supply several quads (quadrillion BTUs, or 1015 BTUs of energy) of algal biodiesel, which is substantially more than existing oilseed crops can provide. (A quad is a unit of energy often used to describe the amounts of energy that a given technology might be able to displace.) Some 200 000 ha (less than 0.1% of climatically suitable crop land areas in the US) could

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produce one quad of fuel (approximately equivalent to 28 billion litres of oil). Microalgae appear to be the only source of biodiesel that has the potential of completely displacing fossil diesel. In one 1000 m2 pond yearly some 7600 L of algal oil can be produced, as compared to 190 L of oil from high-yield canola plants on an equivalent land area. Thus, while traditional crops have yields of around 50–150 gallons of biodiesel/acre/year, algae can yield 5000–20 000 gal/acre/year. According to Briggs [183], widescale biodiesel production from algae in 40 000 saltwater algae farms with a water surface of 250 acres each would ensure America’s diesel fuel independence. Between 2 and 6% of the total US cropping area (455 million acres) would be sufficient for producing algal biomass that satisfies all of the transport fuel needs. There is enough fossil CO2 available in the southwestern US states where climate conditions are suitable to support 2 to 7 quads of fuel production annually. The need for concentrated CO2 limits geographical location of algae ponds to locations next to power plants. Open ponds systems have been or are being developed also in Israel, Malaysia and Mozambique. The algae-biodiesel development company Aquaflow Bionomic Corp. Ltd, Marlborough (New Zealand), has produced B5 from wild microalgae harvested from local open-air sewage ponds and intends to produce 1 ML of ‘green-crude’ on a commercial scale in a 100acre facility as from 2007. Even in countries without abundant sunshine for the photosynthesis of algae, (unwanted) algal growth in ponds, pools and lakes is quite common. Therefore, manufacturing fuel from algae could also help such countries (e.g. in Western Europe) to meet their diesel fuel needs and carbon emission targets. UK’s Carbon Trust has recently launched an algal biofuels alternative. Braun [184] has described biodiesel derived from algal biomass grown under light and temperature conditions that prevail in The Netherlands. Microalgae cultivation allows wastewater treatment, abatement of fossil CO2, production of biodiesel from algal oil, and production of fertilisers. Algae technology offers the opportunity to utilise land and water resources that are unsuited for other use. Land is hardly a limitation. Microalgae systems also use far less water than traditional oilseed crops. Algal production is a closed loop process which allows water to be filtered and reused. Resource limitations are therefore not an argument against algal biodiesel technology. Algae production offers medium- to long-term prospects for the biodiesel industry. It is not the conversion of algae to biofuels that is difficult. The real challenge is producing adequate feedstock. Algae are unlikely to be a viable feedstock option for biodiesel, biocrude and bioethanol for at least 5 to 10 years. Commercial production of significant quantities of algae oil for energy is expected by the year 2015. Prospects of phototropic culture of algae for biodiesel are long term [185].

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Successful application of algae for biodiesel production requires: suitable fresh or salt water supplies, excess CO2 (preferably pond locations next to power plants), efficient and cost-effective oil extraction and high investment costs. Microalgae can be used to capture and reutilise concentrated fossil CO2 emitted by refineries. Before storage lipids of microalgae can be transformed, they must be extracted. Several processes for algal oil extraction have been developed, such as physical or chemical extraction, and thermochemical liquefaction (at high T, p) [186]. Algal oil extraction methods have achieved oil yields of 30–40%. Fermentation technology Growing conventional, photosynthetic algae in the open requires dealing with the variability of the environment, light limitations and contamination with microbes. Fermenters provide controlled, sterile growth conditions. Heterotrophic growth of algae in conventional microbial fermenters in the absence of light can improve the efficiency, maximise productivity, and reduce the cost of microalgal biomass production. In this case, glucose or other forms of organic carbon, rather than light, supply energy. However, as most microalgae are obligate photoautotrophs and unable to grow on fixed carbon compounds [187], the use of fermentation technology is limited. Table 5.25 lists the main characteristics of fermentation technology applied to microalgal biomass. Chlorella protothecoides is a green autotrophic alga that can be grown photoautotrophically or heterotrophically under different conditions. Heterotrophic growth of C. protothecoides results in the accumulation of high lipid contents (55%) in cells, which is several times that in autotrophic cells (14%) [158, 188, 189]. Large amounts of microalgal oil are efficiently extracted from these heterotrophic cells by using n-hexane. To increase the biomass and reduce the cost of microalgal oil production, corn powder hydrolysate instead of glucose can be used as an organic carbon source in the heterotrophic culture medium in fermenters. Table 5.25 Use of fermentation technology in microalgal biomass production Advantages: ∑ Use of conventional microbial fermenters ∑ High productivity, improved efficiency ∑ Reduced production cost ∑ Controlled, sterile growth conditions ∑ Eliminates contamination by microbes ∑ Absence of light Disadvantages: ∑ Applicability limited to few natural or GM algal strains

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Microalgal metabolism may also be genetically engineered for high rates of heterotrophic growth. This extends the applicability of fermentation technology. Focus on scale and production economics are the main drivers to modify algae to grow in the dark in fermentation tanks, sustained by sugar, rather than photosynthetically in the open. Recently, Martek Bioscience Corp. (Columbia, MD) first introduced a fundamental metabolic change in singlecelled algae so that it no longer requires light to grow [190]. The diatom Phaeodactylum tricornutum was genetically engineered to thrive exclusively on exogenous glucose in the absence of light through the introduction of a gene encoding a glucose transporter. This demonstrates that a fundamental change in the metabolism of an organism can be accomplished through the introduction of a single gene. This breakthrough is expected to allow for large-scale, high-density, cost-effective cultivation of algae using fermentation technology. Commercial exploitation of metabolically engineered microalgae requires high rates of exogenous glucose-dependent growth and the achievement of high cell densities. Fermentation-based systems can reduce production costs of microalgae by an order of magnitude relative to that incurred by photosynthesisbased production. The ability to grow microalgae heterotrophically increases the feasibility for developing a large range of new algal products.

5.7.3 Macroalgae Seaweeds are classified into three groups: brown, red and green. Seaweed is primarily grown in the Eastern hemisphere to produce fertiliser and food/ feed but holds potential also for other biomass applications. Farmed seaweed production amounts to 8 Mt/yr. In US Patent No. 7,135,308 B1 Bush and Hall [156] describe cellular decay of starch-accumulating, filament-forming or colony-forming macroalgae (Spirogyra, Cladophora or Oedogonium spp.) in an anaerobic environment followed by fermentation in the presence of a yeast (forming bioethanol) and recovering of the lipids/oils in the residual biomass for conversion into biodiesel. On the whole, the use of macroalgae for the production of biodiesel has found limited interest, which is related to their low oil content [191, 192]. Aresta et al. [191] used scCO2 extraction and thermochemical liquefaction to process a green macroalga from the Mediterranean (Chaetomorpha linum; Cladophorales, Chlorophyta). Thermochemical liquefaction (TL) of algae uses moderate T (523–668 K) and p (3 MPa) and can be applied on wet material. Algal oil composition varies with extraction methodology and TL temperature (see Table 5.26). Within the thermochemical technologies for biofuel production from algae, liquefaction requires lower energy input than pyrolysis [191]. Because of the low permeability and resistance of the cell membrane of the algae, the efficacy of scCO2 extraction depends on

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Table 5.26 Fatty acid composition of Chaetomorpha linum macroalgal oil (after ref. [191]) Procedurea

Composition (wt%)



14:0 16:0 16:1 18:0 18:1 18:2 20:0 20:4 20:6 24:0 Other FAsb

scCO2 extraction 9.8 TL @ 523 K 7.4 a

32.0 3.3 1.5 14.2 21.4 0.3 1.6 21.5 3.2 2.4 14.9 14.4 0.7 1.2

2.6 0.6 18.3 1.6 0.7 15.6

TL, thermochemical liquefaction. Other FAs identified: 15 : 0, 17 : 0, 14 : 1, 16 : 2, 16 : 3, 18 : 3, 18 : 4, 20 : 2, 22 : 5.

b

the pre-treatment (liquid N2 crashing of cells). This methodology does not allow direct use of fresh-wet biomass, but a soft preliminary dry treatment (using solar energy) is required. scCO2 extracts only 4.5 wt% oil from C. linum as opposed to 8 wt% by TL at 668 K. However, in the latter operating conditions decomposition of fatty acids may occur. Both processes also extract phytols. The lipid content (% dry weight) of four species of macroalgae, Ulva lactuca L. (Chlorophyta), Enteromorpha compressa L. Greville (Chlorophyta), Padina pavonica L. Thivy (Phaeophyta) and Laurencia obtusa (Hudson) Lamouroux (Rhodophyta), was reported in the range of 6.6% in E. compressa to 2.4% in L. obtusa [193]. Polyunsaturated fatty acids represented 50.1 to 68.1% of the total fatty acids, with SFAs accounting for 15.0–23.7% of total fatty acids and MFAs 9.0–18.7%. The biochemical composition of marine benthic algae, particularly members of Rhodophyta and Phaeophyta, has received limited attention. Oil from two other species of macroalgae (Gracilariopsis longissima (Rhodophyceae) and Chaetomorpha linum (Ulvophyceae)) were also evaluated for their biofuel potential [192]. Lipid concentrations were 1.87% in G. longissima and 2.40% (fresh mass) in C. linum. Large-scale seaweed cultivation has potential for bioenergy applications. With a 2% recoverable oil content on a dry-weight basis, 1000 L (264 gal) of oil/ha/yr can be obtained from seaweed [194]. From the point of view of natural resource exploitation and energy requirements, macroalgae oil extraction for biodiesel production is nowadays not profitable on the basis of the actual oil yield. Oil yields for biodiesel applications can eventually be increased by selecting and developing seaweed strains or by genetic manipulation methods. Once the oil is extracted, the seaweed biomass may then further be used for alcohol production. Ethanol yield is expected at about 40% of the biomass yield on a dry weight basis, i.e. 20 000 L of ethanol/ha/yr. After ethanol production, a considerable amount of residue is left, which can be burned to generate electricity. Seaweed farming could also be developed using domestic wastewater as a nutritional resource (Fig. 5.10).

Feedstocks for biodiesel production

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Biodiesel Domestic wastewater

Seaweed

Ethanol Electricity

5.10 Potential benefits of seaweed farming.

Spontaneous macroalgae are best considered as a residual biomass for energy uses other than biodiesel (bio-oil, biomethanol, methane for power generation). Europe is planning several algae power plants. The potential of biomass production at sea is still to be explored. Seaweed farming could develop on the Pacific coasts of North and South America, and in the Caribbean. Seaweeds grow well also at low temperatures. One of the most important issues with algae utilisation for energy purposes is their high water content (up to 80–90%).

5.8

Oleaginous microorganisms

Microorganisms are the single-celled entities at the bottom of the food chain. Microorganisms, especially oleaginous moulds, have the capacity to convert a number of raw materials into value-added products, such as oils and fats [195–197]. The oils thus produced are known as single-cell oils (SCO) and are a potential starting material for the production of biodiesel. The best producers with the highest oil contents (up to 70%) are various species of yeasts and fungi with several key algae that are also able to produce high levels of nutritionally important PUFA. Oleaginous microorganisms can accumulate lipids, rapidly, independently of seasons or climates, and grow well on nutritional agro-industrial residues. Although microorganisms have long been known as producers of edible oils, opportunities for their biotechnological exploitation may prove economical only for specialised high-value products (nutraceuticals) [198]. Oils from moulds contain medium-chain fatty acids (C8-C12) to long-chain fatty acids (C22-C24) [199]. Bacteria and fungi, as well as algae (see Section 5.7), often produce polyunsaturated fatty acids (PUFAs) of both the n-6 and n-3 series. Many microbial PUFA oils are characterised by the absence of other PUFAs. Polyunsaturated fatty acids, in particular oleic and linolenic acid, are usually present in abundance in fungal lipids. For the purpose of biodiesel production in Europe the C18:3 content is restricted (see Table 12.6). Carbohydrate-based microbial oils consist of similar fatty acids as plant oils, but no such cost-effective oils are yet available. The fatty acid profiles of fungal lipids obtained from oleaginous moulds on a Czapek-Dox (sucrosebased) medium indicate that single-cell oils harvested from Aspergillus sydowii, Fusarium oxysporum and F. equisetti are rich in oleic acid (46.0–62.9%), with similarity to groundnut and palm oil [200]. The composition of oil from A.

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nidulans is largely saturated fatty acids. The fatty acid profile of the fungus F. oxysporum grown on glucose medium has been found to resemble edible palm oil [201]. The same organisms, when grown on sucrose as a carbon source, showed interconversion between C16:0 and C18:0 acids. Fungal oils prepared from Mortierella alpina are very rich in arachidonic (C20:4n-6) acids (29.2–46.3%) [196, 202]. Biodiesel has been produced in a combined microbial/chemical process in which Cryptococcus curvatus in a sterile whey fraction produces an intracellular fatty acid-rich triglyceride single-cell oil [203]. After disruption of the cells, the oil is removed from the culture broth and cell fragments and is directly subjected to known chemical treatment to produce FAME. Oleaginous yeasts studied for biodiesel preparation include Trichosporon fermentans on waste molasses [204], Lipomyces starkeyi on sewage sludge [205], amongst others. A combination of bacteria, yeast and fungi oil for biodiesel production can be obtained from municipal wastewater plant microorganisms and seafood industry waste [206]. The process is based on the conversion of sugar from waste into fats that can be extracted. Potentially, instead of microalgae, oil producing heterotrophic microorganisms [198, 207] grown on a natural organic carbon source such as sugar, can be used to make biodiesel. However, heterotrophic production is not as efficient as using photosynthetic microalgae. This is because the renewable organic carbon sources required for growing heterotrophic microorganisms are produced ultimately by photosynthesis, usually in crop plants. The commercial outlook for the production of microbial lipids for edible and non-edible industrial purposes is still remote. In particular, the commercial reality of conversion of microbial lipids (yeast or fungal SCOs, algal oils) into biodiesel cannot at this point make a strong case [208].

5.9

Non-edible oilseeds

Alternative feedstocks for biodiesel and renewable diesel fuels are non-food crops and food crop residues. Non-food feedstocks are playing a vital role in the biodiesel market, both for economic and environmental reasons. Oils that contain toxic substances in their seeds and therefore do not conflict with food resources may eventually be good candidates for future worldwide production and supply of plant oils for the biodiesel industry. These include curcas oil (physic nut oil) from Jatropha curcas, and oils from the sandbox tree (Hura crepitans) and sea mango tree (Cerbera manghas). For these and other oils (e.g. Shorea robusta, Mallotus philippines, Hevea brasiliensis, Salvadora oleiodes, Mesua ferrea L., and Garcinia indica) an economical and sustainable system with an appropriate production method must be developed, from the collection of oils/fats as virgin or waste, and their supply

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to the market as the final products. Non-edible rubber (Hevea brasiliensis) seed oil (AV, 1 mg KOH/g; SN, 185.8 mg KOH/g; IV 142.6 g I2/100 g), of limited industrial use, has been transesterified by base-catalysis (NaOH) in 84% yield [209]. Moisture content of the oil is moderately high (3.7%) and may cause serious degradation of the fatty materials by hydrolysis, thus imposing the need for drying. Production of biodiesel using unrefined, highFFA rubber seed oil (C16 : 0, 10.2%; C18 : 0, 8.7%; C18 : 1, 24.6%; C18 : 2, 39.6%; C18 : 3, 16.3%; SFA, 19%; MUFA, 25%; PUFA, 56%; AV 34 mg KOH/g) requires a two-step transesterification process [210]. At present, the market is mainly investing in new, non-edible raw materials such as algae, Jatropha, camelina, mustard, seashore mallow and brown grease. One must remain realistic about the amount of time required to fully benefit from these investments. Moreover, large-scale cultivation of non-food oil crops is not even a panacea for biofuels, as large amounts of toxic meal are co-produced, for example using castor beans, jatropha, pongamia, undi, etc. [22]. Crambe (Crambe abyssinica) is a member of the Brassicaceae family. The herbaceous annual is also known as Ethiopian kale, Abyssinian mustard, Abyssinian kale, colewart and katran. Crambe, a drought-tolerant, low-input, industrial oilseed, has been grown and processed on a commercial scale in North Dakota (US) since 1990 [211]. Production area is limited (30 000 to 60 000 acres). Crambe has a higher concentration of erucic acid (> 55% C22:1) than most other species (see Table 5.1) and low FFA contents (< 0.5%). Crambe has been developed mainly as a source of erucic acid but shows promise of becoming a new industrial oil crop [212]. Crambe oil and HERO can be considered as the most important vegetable oils for lubricating purposes. Their high unsaturated fatty acid contents negatively influence the oxidative stability. The many advantages of cardoon or artichoke (Cynara cardunculus L.), namely low cost of production, capability of growing in harsh climatic conditions, and no competition with the food market or chemical industry, make it an ideal raw material for biodiesel production. Cultivation of cardoon as a non-food crop for energy (and as a suitable source of cellulose fibres) using abandoned croplands has been proposed [213]. Cardoon belongs to the Asteraceae family (Compositae), which also includes sunflower and safflower, and yields oil characterised by a fatty acid composition similar to (conventional) SNO (see Table 5.1). Cardoon oil contains about 1% FFA (as oleic acid). Biodiesel obtained from cynara oil has fairly suitable characteristics but for CN (48.6) and IV (118–125 g I2/hg), slightly beyond EN 14214 limits [14]. Cloud and pour points indicate potential difficult cold starts. In-situ transesterification of C. cardunculus seeds to obtain biodiesel has been evaluated [214]. Spanish research outfit Technatom is heading the BIOCARD programme to improve the exploitation of this energy

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Biodiesel science and technology

crop. Though cardoon is considered suitable for Mediterranean areas with problems of water sufficiency, early research programmes have not proved very successful so far. Castor beans (Ricinus communis) grow on marginal lands, require little rainfall (15–18 in./yr), and can withstand long periods of drought. Castor bean (Mamona) cultivation is low maintenance, but machine harvesting needs to be developed. The poisonous plant provides beans with a high oil content; the cake contains toxins. The enzymatic production of biodiesel from castor oil has been reported [15]. Castor bean oil is an option for fuel production because it does not compete with food crops for arable land space. Castor oil is considered as a most important feedstock for perennial crops for biodiesel in arid North-East Brazil. Jamaica has also selected castor beans as a biodiesel feedstock. Castor beans yield approximately 47–49% of oil. With an oilseed productivity of 700–1200 kg/ha, some 500 L biodiesel/ha can be generated. As pointed out elsewhere (Sections 3.4, 3.5 and 6.4.6), castor oil is valuable both as an oleochemical multipurpose resource (soaps, perfumes, paints, plastics industry) and for lubricity enhancing applications. Biodiesel obtained from castor oil has a lower cost compared to that obtained from other oils, as transesterification occurs at room temperature because of its unusual solubility in alcohols. It appears, however, that castor oil may not prove to be a good raw material for the production of biodiesel [215, 216]. Even if high yields of biodiesel are obtained, the viscosity of castor biodiesel (13.75 mm2/s, as compared to 3.2 mm2/s for mineral diesel) would cause a problem for most practical diesel engines. The fringe oilseed crop Camelina sativa L. (Brassicaceae), commonly known as gold-of-pleasure, false flax, or linseed dodder, is considered as a promising potential oil crop for non-food industrial applications [217, 218]. The under-exploited canola relative is a short-season crop (85 to 100 days) that is well suited for marginally productive soils and has low harvesting costs and a lower break-even cost than soybeans, wheat or canola. Camelina varieties have been developed which require little water or fertiliser. Camelina seeds are small (220 000 to 450 000 seeds/lb), and oil content is 29–41%, but 38–40% in some varieties. Its yields are impressive with 1200 to 1500 lbs/acre, up to 2400 lbs, compared with 1000 lbs for canola. The crop is of interest for its very low requirements for tillage and weed control. Camelina has been grown for millennia in parts of Europe, but is a relatively new crop to the US. Camelina is an annual or winter annual crop, fit for cool regions where canola production is difficult (e.g. northern US states). As camelina does not yet have GRAS status from federal US agencies, all of the oil is eventually going towards biodiesel production. The oil and meal by-product of camelina can be used in cosmetics, for protein enrichment in animal feeds, as a fuel additive, a barrier to prevent weed emergence, and for the biofuel and by-product industries. Limited research has been done

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to determine its full agronomic potential. NACTA is promoting camelina development. Sustainable Oils, Inc. (Bozeman, MT) is currently evaluating the agronomic characteristics, grain yield and oil quality attributes of more than 120 breeding populations on 40 trials across North America. Many different views exist in regard to Camelina’s oil composition: C18:1, 14–20%; C18:2, 15–25%; C18:3, 35–45%; C20:1, 15–20%; C22:1, 1–3%. C. sativa oil is considered a high-quality oil, low in saturated fatty acids and with exceptionally high levels (up to 45%) of omega-3 fatty acids, which is uncommon in vegetable sources. Camelina’s high percentage of PUFAs (> 50%) makes it more susceptible to oxidation (despite a substantial amount of natural antioxidants), thereby making it undesirable for biodiesel production. C. sativa is fast drying. So far, there is no commercial use for the oil. The viability of Camelina as a feedstock for biodiesel application remains to be seen [218]. Although camelina oil has been considered for biodiesel production [16, 217, 219, 220] its potential high value (due to the important nutritional components a-linolenic acid and g-tocopherol) may preclude its future use as a biofuel feedstock. The price of camelina biodiesel is currently about US$6/gal; the challenge is to make camelina biodiesel affordable. Further research is necessary to develop it into a strong potential biodiesel feedstock. It has been reported that camelina biodiesel meets the ASTM standards with good cold-flow properties (PP, 248 K; CP, 258 K; CFPP, 270 K), oxidative stability and low phosphorous [221]. Early 2009, Japan Airlines has carried out a demo flight fueled in part by camelina. In Europe, where camelina oil has been used in biodiesel for several years, extensive tests determined that fuel properties are within specifications with the exception of cold filter plug point (CFPP). The CFPP additive CP7134 has been approved in Ireland, making the camelina CFPP acceptable at winter temperatures. However, for commercial use of biodiesel it seems necessary to reduce the content of highly unsaturated fatty acids in C. sativa. The high C18:3 content (35–45%) – though not as high as in flax oil – is incompatible with EN 14214 specifications. Büchsenschütz-Nothdurft et al. [222] have described breeding for modified fatty acid composition via mutagenesis in Camelina sativa (L.) Crtz. Aloe vera (Asphodelaceae family) is used as a cosmetic and medicinal remedy. Aloe vera seed oil (AVSO) may be used for biodiesel production [223]. The oil content of AVSO is about 20–22 wt%; SFA amounts to 12%. The high unsaturated fatty acid content (87%) imparts the properties of low melting point and low viscosity. AVSO properties are quite similar to those of conventional SNO. Also tobacco and rubber seed oils have been considered as an alternative diesel fuel [209, 224]. The Indian and Chinese challenge is food or fuel. India accounts for about 10% of global oilseed production, in particular SBO, CNO, CSO, PNO, RSO

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Table 5.27 Chemical composition of some Indian vegetable oils (after ref. [225]) Vegetable

Fatty acid composition, wt.%

oil

14:0

16:0

18:0

20:0

24:0

18:1

18:2

Sal Mahua Neem Karanja Rice bran

– – 0.2–0.3 – 0.4–0.6

4.5–8.6 16.0–28.2 13.6–16.2 3.7–7.9 11.7–16.5

34.2–44.8 20.0–25.1 14.4–24.1 2.4–8.9 1.7–2.5

6.3–12.2 0.0–3.3 0.8–3.4 – 0.4–0.6

– – – 1.1–3.5 0.4–0.9

34.2–44.8 41.0–51.0 49.1–61.9 44.5–71.3 39.2–43.7

2.7 8.9–13.7 2.3–15.8 10.8–18.3 26.4–35.1

Table 5.28 Non-edible Indian oil sources (after ref. [225]) Oil

Botanical name

Potential (kt)

Utilised (kt)

Utilisation (%)

Rice bran Sal Neem Karanja

Oryza sativa Shorea robusta Azadirachta indica Pongamia pinnata

474 720 400 135

101 23 20 8

21 3 6 6

and SFO, though mainly for food applications. The country needs to develop new and more productive plant sources with high oil content seeds. As India is not self-sufficient in vegetable oil production, under Indian conditions only non-edible oil producing plants are considered as energy crops. Non-edible oils, such as neem, mahua, karanja and jatropha, are available in many parts of the world, including India, and are cheap compared to edible oils, except for neem (see Section 6.4.1). Table 5.27 shows the chemical composition of some of these vegetable oils. The potential availability of some non-edible oils in India is given in Table 5.28 [226]. There are various studies that report on non-edible oils which are produced in the wastelands from wild species, such as Jatropha curcas, Pongamia pinnata and Simarouba glauca. Despite the abundance of forest and treeborne non-edible oils available in India, use of their esters as biodiesel is still limited and has mainly concerned seed oils of jatropha (see Section 5.9.1), mahua (Madhuca indica) [227–231] and karanja (Pongamia pinnata) [229, 232–234], the latter with a fatty acid profile similar to canola. In (sub) tropical climates, such as in India, high pour points (279 K for mahua diesel with a high percentage of saturated fatty acids) may not pose any problem except in cold weather conditions. The flash point of mahua oil (511 K) is very high as compared to mahua diesel (320 K), indicating its low volatile nature. There also remain a number of other tree-borne oilseeds (TBO) like sal, nahor, neem and undi, all with a limited annual production [20, 225]. Croton (Croton tiglium or Oleum tiglium L.) (Euphorbiaceae) oil (main acids: C18:1, 37.0%; C18:2, 19.0%; IV, 104–110 g I2/hg; SV, 200–215 mg KOH/g) contains 3.4% toxic resins and is a powerful irritant (purgative). Croton oil, which has the highest specific gravity of all fatty oils (except for

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castor oil), is intermediate between drying and non-drying oils. Croton is being cultivated extensively in India, Sri Lanka and Europe. As seed yields are low (only 900 kg/ha) croton is not a promising energy species. Non-food crops are an ambitious goal. Identification of fatty materials having no impact on the food chain also suggests a re-qualification of nonedible oils such as fish oils, flax oil, and tall oil fatty acids by means of selective hydrogenation, which might make available important quantities of biodiesel production with reduced or no impact on the food chain.

5.9.1 Jatropha nut oil Jatropha curcas (physic nut, black vomit nut, bubble bush, Ratanjot, Wild Castor, Jangli Erandi), native to the Caribbean, Central and South America, is a typical example of a non-food crop now being developed solely for fuel. Jatropha (Euphorbiaceae family) is a genus comprising 70 species growing in tropical and subtropical countries, including Africa and Asia. Nine species of this groundnut are reported to occur in India. Jatropha is a weed, wildly growing in arid and semi-arid regions on degraded wastelands having low fertility and moisture. While jatropha is touted as being able to survive in poor soils with very little fertiliser and water, the fruit (and thus oil) yields increase significantly with increased soil fertility and water. This hardy scrub, which has a 35- to 40-year life cycle, has had very little scientific long-term study, because it is not part of the food chain. Jatropha is a multipurpose plant (Table 5.29), which is not grazed by animals because of its toxicity. A non-toxic variety is found only in Mexico. Jatropha represents a sustainable energy source for many rural areas in the developing world [235]. In India the cake of jatropha is being used for biogas (generating electricity) and Table 5.29 Multi-purpose uses of Jatropha curcas Whole plant ∑ Erosion control ∑ Rodent repeller ∑ Hedge ∑ CO2 sequestration ∑ Shelter/support for other plants ∑ Medicinal uses Bark, leaf, root and latex ∑ Anti-inflammatory agents ∑ Tannins

∑ Mulch ∑ Dyes

Fruit kernel ∑ Oil Seed cake ∑ Animal feed ∑ Organic fertiliser

∑ Rodent repellent ∑ Biogas (pyrolysis)

Fruit shell, husk ∑ Fuel

∑ Mulch

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biomethanation [236]: see also Fig. 4.1. The meal can also be used for production of cellulosic ethanol. Jatropha grown in marginal, non-agricultural areas, is not affected by rising food prices, requires little water for cultivation, and does not compete with existing agricultural resources. A benefit of jatropha is the long-term yield. At variance to plants such as soybeans, which need to be replanted and harvested every year, jatropha can be harvested almost continuously over a 30-year period. The plant produces oil-rich seeds nine months per year. Jatropha grows quickly and yields two harvests per year. A single jatropha tree can achieve yields of 3 kg seeds/tree/yr or approximately 0.75 L of biodiesel. The annual yield/ha is up to 8 t of jatropha seed (but may be as a low as 220 kg/ha on poor quality land), which overall contains 25–40% oil. If irrigated and fertilised, one hectare of jatropha can produce between 2.5 t of seed oil and about 3 t biodiesel, or about four times as much as soybeans. However, on average oil yields are more modest (about 500 kg/ ha). Jatropha has not yet been genetically modified, meaning the yields can only get better. Expectations are a three- to fourfold increase [237]. Despite its many promising features (Table 5.30), not everything is rosy for jatropha [238]. Jatropha is a cross-pollinated plant (meaning genetic uncertainty for farmers) which is very much in the beginning of domestication. Domestication of a wild plant carries risks. Jatropha is not the ideal biodiesel Table 5.30 Characteristics and challenges of Jatropha curcas as an energy crop Advantageous characteristics: ∑ Widespread in tropics ∑ Capable of growing and establishing in various biotic and abiotic stress conditions ∑ Grows on unfertile degraded soil (but with low seed yields) ∑ Draught and disease resistant (low seed production) ∑ Short gestation period (two years) ∑ Multi-purpose plant (see Table 5.29) ∑ Good hedge plant, prevents erosion ∑ Not browsed by cattle ∑ Superior over other non-edible oil plants ∑ High long-term annual yield/ha ∑ High oil content (25–40%) ∑ Yields high-quality biodiesel Challenges: ∑ Domestication in infancy ∑ Tree management ∑ Consistency of oil yields ∑ Increasing oil volumes ∑ More uniform fruit maturation rates ∑ Mechanical harvesting ∑ Co-product development

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crop due to its weedy characteristics and the nuts being poisonous to humans and animals; the crop is labour-intensive. Jatropha is banned as a weed in Australia’s northern regions. For this (overpromoted) crop some considerable challenges still lie ahead (Table 5.30). No long-term comprehensive research has been completed on the cultivation of large monoculture jatropha plots. Successful cultivation requires spotting the right location to grow the crop in terms of climate economics and politics. D1 Oils PLC aims at developing a jatropha hybrid featuring consistent yields, height, flowering and fruiting within the next 5–10 years. The economic viability of the crop could be enhanced by co-product development (high-quality seedcake). Jatropha oil can be extracted from the seeds with a simple expeller (as used for mustard seeds). Jatropha seeds can be separated into a fibre-rich hull fraction (40 wt% of the seed) and a kernel fraction in which almost all the oil is concentrated. The oil content of the seed kernel of this succulent is thus very high (40–60 wt%) [239]. Depending on the pressing technology, 60–80% of the oil content can be extracted. Crude Jatropha curcas oil (also called hell oil), which contains 2.5–5.5% FFA or even more, is colourless when fresh but yellows on standing (due to the high level of unsaturation). Good quality crude jatropha oil has a rather low phosphatide content (<0.25%) and a free fatty acid content comparable to that of crude palm oil. Jatropha oil is valued at US$320/t (2007). Jatropha oil finds many possible applications: biodiesel, lubricant, illumination, soaps, cosmetics, medicinal uses, biopesticides (phorbol esters). While the composition of the oil is similar to other oils that are used for edible purposes (see Table 5.1), the presence of some antinutritional factors such as toxic phorbol esters [18] renders this oil unsuitable for use in cooking. Thus, it is a good choice as the starting oil for sustainable production of biodiesel [240, 241]. In fact, the seed oil of Jatropha was already used as a diesel fuel substitute during World War II. Later, its blends with diesel fuel were tested [242]. Jatropha can be readily integrated into biodiesel production processes, but the plant is not yet available in abundance. Little is known about how to make it a successful crop. A dramatic expansion in large-scale jatropha plantations (over 1.75 Mha) has recently been announced worldwide, in particular in South-East Asia, Africa and Central and South America [243]. Jatropha projects in Asia are under way in India (>1 Mha; D1 Oil, BP Mission Biofuels, Mission NewEnergy Ltd., local projects), Cambodia (20 kha; Van der Horst), Malaysia (22 kha; Mission Biofuels) and Indonesia (220 kha; BP, BioEnergy, Renewable Fuel Corp. Inc.), and also in Saudi Arabia (D1 Oils) and the Philippines (1Mha; D1 Oils, NRG Chemical, Philippine National Oil Company). Myanmar cultivates approximately 800 kha of jatropha. JatOil Ltd. (Pyrmont, NSW) has jatropha field trials underway in Vietnam. The London-based biodiesel start-up D1 Oils PLC intends to create a

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world-leading business in J. curcas. It is establishing extensive sources of jatropha and has planted or obtained rights to 125 kha in India, South-East Asia and South Africa, and has started a joint venture for the production of jatrodiesel in Saudi Arabia. D1 Oils/BP Fuel Crops Ltd. estimates that 1 Mha of jatropha will be planted in India, South-East Asia and southern Africa over the period 2007–11, with an extra 300 kha/yr afterwards. Initial jatropha oil production for biodiesel is likely to take off in India in 2008 and will grow in greater volumes from 2010 and beyond (in Africa, South-East Asia, and Latin America), partly for exports. High estimate plans for India include jatropha cultivation of nearly 2 Mha by 2012. However, governments in south Asia and Africa have identified between 20 and 50 Mha of suitable land for jatropha cultivation. Jatropha is considered as one of the best among a large number of oil yielding species identified in India, due to its multiple benefits and wide adaptability (Table 5.29). Good returns to farmers are assured if the yield level is 5 t/ha with a seed price for jatropha of Rs 5/kg to Rs 8/ kg (both assumptions are on the high side) [244]. India alone has classified 60 Mha as agricultural wastelands that in principle are suitable for jatropha cultivation. Land by the side of Indian railway tracks are being planted with drought-resistant Jatropha shrub and trains run on jatrodiesel (B15–20). Also the planting area of Jatropha curcas in P.R. China is growing quickly (Planting Plan along the Yangzi river) and should eventually reach 13 Mha. Within the framework of the UK–China Partners in Science Programme, the Centre for Novel Agricultural Products (CNAP) in York and Sichuan University, Chongqing, are exploring jatropha biodiesel. Outside of India, Africa is now the second largest area of large-scale jatropha cultivation. Mozambique intends cultivating 300 kha of jatropha oilseed crops starting planting in 2008. Other large-scale African jatropha planting projects run in Ghana (Goldstar Farms Ltd., 2Mha), Malawi (55 kha), Madagascar (17 kha), South Africa (15 kha), Burkina Faso (25 kha), Mali, Sierra Leone and Nigeria. There are governmental programmes for cultivation of Jatropha also in other countries (e.g. Egypt, Tanzania). Royal Dutch Shell is promoting a small biodiesel project (1500 ha) in the fallow lands of Transkei, based on Jatropha and other indigeneous oil crops [245]. Jatropha is also at the top of the list as a primary source of feedstock for biodiesel production in Central America with 200 kha plantations in Haiti, 100 kha plantations in Guatemala, and others in Chile (Gold Star Biofuels, 1 Mha), Colombia, Peru, Honduras and Mexico [246]. Jatropha farming projects in Brazil comprise over 100 kha; see Section 6.4.4. Mission NewEnergy, Ltd. (Perth, Australia) is expanding jatropha plantation to 750 000 acres by June 2009. Jatropha projects serve three key roles: 1. as an energy crop for local and community projects;

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197

2. contributing to national petrol independence programmes of dedicated countries; and 3. meeting global biodiesel demands from Europe, the US and Asia on a commercial scale (export). The impact of large-scale production of Jatropha will require 8–10 years. Gressel [22] has recently severely criticised large-scale cultivation of toxic, wild-type jatropha. Jatropha’s water footprint is considerably greater than that of rapeseed, soy or sugar beet.

5.10

Low-quality feedstocks

The economics of biodiesel production may be improved through the use of low-value lipids as (extremely) low-cost feedstocks (see Table 5.31). Moreover, as no one raw material is in adequate supply to be used solely for biodiesel production, fats from the rendering industry are expected to play an increasingly important role as a highly desirable feedstock [246a]. Recently, a growing number of studies have reported use of cheap waste oils and fats (animal tallow) as a raw material [108, 210, 247–272]. By-products of the vegetable oil industry which also show promise as raw materials for alkyl ester production are rice bran oil [229, 273, 274] (see Section 5.5), palm-fruit pulp oil [275] and waste activated bleaching earth [276]. Biodiesel can be made out of 80% FFA oil. The environmental benefits of recycling a lower-value material into a high-value energy product are obvious. This biodiesel will leave the lowest carbon footprint, provide the highest energy balance and is food- and forestfriendly. As shown in Chapter 9, low-cost feedstocks must usually undergo some form of pre-treatment (filtration, bleaching, deodorisation, steam distillation, gravity separation, drying, pre-esterification) before they can be transesterified Table 5.31 Low-cost feedstocks Indicative FFA range Sources 0.5–7.0 wt%

Crude vegetable oils Prime, edible tallow Poultry fat Choice white grease Recovered cooking oil

10–20 wt%

‘A’ Tallow Yellow grease Low-grade crude vegetable oils

> 20 wt%

Brown grease Pure FFA and FFA raffinate Recovered soap

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Biodiesel science and technology

to biodiesel. Figure 5.3 shows the fractionation of crude animal fat. Some esterification methods applicable to vegetable oils are not indicated for animal fats or fried oils because of chemical property differences (high amounts of FFAs, water and oxidised components). Waste oils are particularly suitable for two-step catalytic esterification-transesterification or enzymatic catalysis. Lipase catalysis allows the simultaneous transesterification of triglycerides and esterification of FFAs in a one-step process, and many lipases work well in the presence of water. As conversion of low-value feedstocks with high levels of FFAs into biodiesel requires more heat and pressure, supercritical methods may also be considered. Accordingly, Babcock and Schulte [277] used such a one-step non-catalytic method to convert low-grade chicken fat (6% FFA) and crude tall oil at 598 K into biodiesel with 94% and 89% yields, respectively. Crude tall oil contains rosins and resin acids that do not combine with methanol to form biodiesel under the test conditions. In the case of rice bran oil, in-situ transesterification (a combined extraction and transesterification process, see Section 7.4) has been reported [273]. The same procedure is applicable to palm-fruit pulp [275]. An overview of biodiesel production for RSO (canola), SBO, WVO and animal fats is available [278]. Quality assurance of biodiesels based on lowcost feedstocks is obviously more problematic than in the case of refined starting materials.

5.10.1 Rendered oils and fats Rendering is the (dry or wet) extraction of fat or oil from animal tissues using heat. The rendering industry classifies used cooking oils (UCOs) and fats into different categories, but not in a uniform way worldwide. Grades of fat produced by the rendering industry are ranked according to different specifications including total fatty acids, free fatty acids, moisture, unsaponifiable and insoluble matter. Trade practice is to designate animal fats with titres (solidification point of fatty acids) of at least 313 K as tallow and below 313 K as grease. Greases are also referred to as recovered vegetable oils. Used cooking oils typically contain 2–7 wt% FFA and crude animal fats generally some 10 wt%, but occasionally much more. Tallow (TLW), a volatile commodity, is beef fat originating from slaughterhouses. Feedstocks with FFA levels in excess of ~4 wt% are American lower-quality animal fats (prime tallow, special tallow, ‘A’ tallow and poultry fat) [279] and British tallows no. 3–6 [280]. Lard is an edible grease. Choice white grease is a specific grade of mostly pork fat. Recycled grease products are referred to as waste grease. Greases are generally classified into two categories: yellow and brown grease. Yellow grease (typically containing some 7–20% FFA), sometimes referred to simply as waste oil, may be of vegetable or animal origin and is usually

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obtained from waste cooking oils, primarily from fast food restaurants and school cafeterias. Another source is from rendered animal (feed) fats (poorer pork and beef sources) that have been heated and used for cooking a wide variety of meat, fish or vegetable products. Various chemical and physical properties of oils and fats are affected by frying. FFA contents increase (due to hydrolysis and oxidation) and typically change from 0.04% in fresh SBO to 1.51% after 70 h of frying at 463 K [281]. Viscosity also increases (due to polymerisation), as well as AV, SV and specific gravity, but IV decreases. #2 Yellow grease cannot exceed 10 wt% FFA content, and #3 yellow grease can reach up to 20 wt%. The difference between yellow grease and raw used cooking oils is the amount of processing involved. Renderers remove solids and moisture until it meets industry specifications for yellow grease. To use waste cooking oils for biodiesel production, all that is required is filtering and dewatering. The spot price for yellow grease (max. 10 wt% FFA, tanks) on 1 March 2004 from Chemical Market Reporter was US$0.13/ lb. Meanwhile, fryer grease has become much more valuable: its value has increased to historic highs in recent months (US$0.40/lb by mid July 2008); see also Table 14.21. Not surprisingly, cooking oil theft has recently become a new phenomenon. In the US, yellow grease is required to have an FFA content below 15 wt%, otherwise it is classified as brown (or trap) grease [279]; the British classification system identifies one category of grease with FFA ≤ 20 wt% [280]. Trap grease refers to grease collected from traps installed in sewage facilities which separate water from oil and ‘black grease’ (sludge) in wastewater. Grease traps (interceptors) are installed in drain lines of restaurants and similar facilities. Trap grease is abundant in urban centres. Brown or trap grease is not suitable for animal feed due to its highly contaminated state. Brown grease generally has an FFA content of over 20 wt% and can reach levels as high as 50–100 wt%. Lipid content is minimal; brown grease is gelatinous at room temperature. Grease trap waste encompasses a highly variable mixture of organic fats, greases and vegetable oils, comprising a high free fatty acid and mono-, di- and triglyceride content, contaminated by detergents, water, soaps, inorganic and particulate matter. Typically, the grease trap waste is between 80 and 100 wt% free fatty acids and glycerides (MG, DG, TG). Major components of grease trap waste are octadecanoic acid and n-hexadecanoic acid [267]. The production of large quantities of waste vegetable oils (WVO) is common to almost all world cuisines. Though cheap, used frying oils are limited in their availability (mainly in urban areas) and require a recycling infrastructure involving citizens, companies and local administrations. Cooking oils may be blends (e.g. composed of SBO, RSO and CRO). Waste cooking oil offers some potential as an alternative low-cost biodiesel feedstock whose availability is not affected by land use policies. It is estimated that 0.7–1

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Biodiesel science and technology

Mt/yr could be collected within the EU. The first plant for the production of methyl esters from used frying oil was put into operation in Mureck (Austria) in 1994 [282]. Austria recycles over 1300 t/yr of used cooking oils into biodiesel. The UK transforms about 75 kt of waste vegetable oil each year (total potential: 100 kt/yr). As much of Asian food is fried, there is locally plenty of yellow grease available. Until 1999, in Japan 90% of the considerable amounts of used edible oils (700 kt SBO, 80 kt CNO, 50 kt CSO, and 700 kt RSO yearly) were dumped as refuse without collection; only 10% of the waste edible oil was recycled to be employed as a raw material for oleochemical purposes (soaps or the like). This has brought calls for promotional action for the effective utilisation of food resources and environmental protection [283]. In recent years, biodiesel has been produced from waste edible oils on a pilot scale in Kyoto City. Leung and Chen [251] have investigated biodiesel production technologies using waste cooking oils from Hong Kong restaurants. The US produces large amounts of used cooking oils and animal fats (about 13 billion lbs) [284], reflecting the dominance of fried restaurant foods in the country. The 13 700 McDonald’s restaurants in the US use more than 35 kt/yr of frying oil. A large fraction of low value (< US$1/gal) fats, oils and grease (FOGs) is used for soap, cattle feed and other products, whereas only a minor proportion of these available raw materials is used in biodiesel production. Biodiesel legislation under the 2004 America Jobs Creation Act offered fuel blenders up to US$0.50 of federal support for each gallon of biodiesel made from used cooking oil (‘from McDonald’s to McDiesel’); this has recently been extended to a full tax credit (US$1/gal). Yellow grease is readily available at low cost. Production costs, including collection and (pre)processing, are about US$2/gal. Yellow grease lends itself best to transesterification in small biodiesel facilities (up to 5 MMgy), located in urban centres [285]. Typically, a medium-sized US city (e.g. Philadelphia) generates about 1 Mgy of yellow grease. Tellurian and Golden State Foods have formed a partnership for use of UCO. In Nov. 2007 San Francisco launched the SFGreasecycle program to turn FOGs into 1.5 Mgy of fuel for its municipal fleets. Used cooking oils are collected free of charge from food-service establishments. The city also intends producing biodiesel from brown grease; a demo plant is under development (Tellurian Biodiesel Inc., Los Angeles, CA). More recently, a Renew Energy Resources (Tampa, FL) subsidiary (Legacy Oil LCC), partnering with the Doe Fund (New York), has announced production of 5 MMgy biodiesel from New York City waste cooking oil and trap grease. Used US cooking oil has also been shipped to The Netherlands for biodiesel production. The biodiesel industry classifies feedstocks by their FFA content: ∑

refined oils, such as canola or soybean oil (FFA < 1.5 wt%),

Feedstocks for biodiesel production

∑ ∑

201

low free fatty acid yellow greases and animal fats (FFA < 5 wt%); and high free fatty acid greases and animal fats (FFA ≥ 20 wt%).

Waste oils and fats generally constitute a very heterogeneous mixture, including particulate matter, organic impurities, oxidative degradation and polymerisation products, free fatty acids and water. As levels of FFAs in feedstocks from a rendering plant may vary typically from 0.7% to 42%, and moisture from 0.01% to 55%, consequently a very robust biodiesel process is needed for conversion of waste grease to biodiesel, which tolerates a wide range of feedstock properties. Because of the large amounts of water, FFAs and debris (sediments) in yellow grease, most biodiesel producers are unable to use this inconsistent raw material, which requires pre-processing. It is not possible to convert such feedstocks to biodiesel using a single-step process; a two-step process is needed [286] (see Chapter 9). After reduction of the acid value to less than 2 mg KOH/g with an acid-catalysed pre-treatment process, the reaction may then be completed with alkali-catalysed transesterification. Water formation is the primary mechanism limiting the completion of acidcatalysed esterification with FFAs. Vegetable oils as diesel fuel have been investigated more extensively than animal fats. Waste vegetable oil contains more FFAs than virgin oils. Free fatty acids raise the cloud point of the fuel, so biodiesel made from used cooking oil or animal fat will cloud at higher temperatures than biodiesel made from virgin vegetable oil feedstock; yellow grease clouds at intermediate values. Similar to waste cooking oils, animal fats are a cheap alternative feedstock source of limited availability only. Up to the year 2000, UCO and TLW went into animal feeds but this is no longer allowed according to EU rulings (Animal By-Products Regulation, EC 1774/2002), as a reaction to mad cow disease (bovine spongiform encephalopathy, BSE) in 2000–01. Rendered fats are now classified into three different risk categories: categories I and II can no longer be fed to animals, whereas category III is no-risk material. Import and export of rendered fats from category I and II material is nowadays limited by restrictive regulations and markets are country-specific. EU laws restrict import of tallow unless it is from Category III raw material (material that is edible); the import of used cooking oil for animal feedstocks is banned. EC Regulation 92/2005 has enabled use of Category I tallow in biodiesel production as long as the tallow is processed at 406 K and 0.3 MPa pressure for 20 min, a system referred to as ‘pressure cooking’. If the raw material is Category III, then pressure cooking is not required, but such fat can usually gain a premium in the marketplace, making it potentially uneconomic for biodiesel production. Prices vary considerably, from 740–150/t for risk material to 7230–270/t for no-risk material (Austria, 2005); cf. contemporary RSO price of 7550–650/t (UFOP, 2005). US tallow, which could be used

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for biodiesel production, often contains dead stock in the raw material blend, which defines the tallow as Category I under European legislation, thus requiring ‘pressure cooking’, a system not used in the US. Animal fat products, reviewed in ref. [287], are excellent sources for biodiesel due to their high cetane number (typically 56–62) and good stability. As a result of the BSE problem, which has created alarm for all products of animal origin, a significant amount of animal fat from so-called high-risk material (tallow, yellow grease, etc.), possibly contaminated with infectious prions, has now become available at an attractive price for industrial purposes such as biodiesel production. Exposure to the infectious prions responsible for BSE disease in cattle, through use of animal fats in biodiesel production, has been of potential concern. Analysis by EC [288], the FDA [289] and the WHO [290] has indicated that rendered animal fat is not an agent of transmission of BSE. A risk assessment for the biodiesel production from possibly BSE-contaminated fat has been published [291]. Animal fats have also been a main raw material for glycerol. In view of BSE, glycerol of vegetable origin is now being favoured for human contact. The BSE problem has also led to an increased EU biodiesel production based on used cooking oils. The supply of cooking oil and tallow in the EU is not able to provide all the necessary biodiesel feedstock required. While the quantities of waste feedstocks are not sufficient to supply a large market, they can be used as blending agents to lower the overall costs. Germany and Austria have the most practical experience with collection and processing of recycled vegetable oils and fats. The German rendering company Saria started processing rendered fats into biodiesel, which – although not fulfilling the European standard EN 14214 in all parameters – fueled Saria’s own truck fleet. Austria produces some 15 kt of rendered fat category I and 10 kt category III (2004). Biodiesel from Austrian animal fats (category I) would substitute only about 0.4% of the annual Austrian diesel consumption. The annual production of animal fats (tallow, lard and butter) is about 20–22 Mt/yr [292]. Animal fats used for alkyl ester production are mainly beef tallow [253, 259, 293–295] and lard [263], but also poultry fat [296] has been proposed. The very high content of saturated fatty acids of such feedstocks yield methyl esters with poor cold temperature properties, although the impact on B5 blends is only very slight. The cloud point of biodiesel from inedible tallow is 289 K, compared with 276 K for soy biodiesel and 270 K for canola. During the winter and transition period (1 Oct.–15 April), RME has to be added to keep yellow-grease-based European biodiesel fully fluid. Both CFPP and CN can be improved by alcoholysis of oils and fats with low unsaturation (< 20%) with branched alcohols (e.g. isopropanol) [297]. In the early years of the biodiesel industry, animal fat-based biodiesel

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has gained a poor reputation because quality standards were not always adhered to. Today, there are many high-quality (ASTM spec) animal fatbased biodiesel producers. Brown grease can be processed into biodiesel but at higher cost and lower biodiesel yield than yellow grease or tallow. Production of biodiesel from this low-cost urban lipid source is being considered. It is possible to produce biodiesel meeting all ASTM D 6751 specifications using a variety of different trap grease feedstocks [271]. Major chemical challenges are numerous: odour, heavy emulsification, solid contamination, cold flow, high water content, heterogeneity, etc. Processing brown grease into biodiesel requires several pre-treatment steps (filtering, deodorising, bleaching, vacuum distilling, etc.). FFAs and water must be removed from the grease (e.g. by solvent extraction) since these components serve as an inhibitor for biodiesel fuel production [298]. The technology requires further development (as at the aforementioned Tellurian’s demo plant in San Francisco). Brown grease biodiesel facilities should also be located in urban areas. Fry-o-Diesel’s pilot facility (now Black-Gold Biofuels) in Philadelphia, PA, has been producing biodiesel from brown grease at low volumes. Similarly, BioFuel BoxCorp. (San José, CA) is a 100% brown grease-based biodiesel producer. A resource assessment of edible and inedible beef tallow generations in the US has indicated more than 1.8 Mt/yr (for the period 1997–2001) in the 11 largest commercial cattle slaughtering states, which would at most equate to some 550 Mgy of biodiesel [299]. The potential of restaurant waste lipids as biodiesel feedstocks in the US was recently also evaluated by Canakci [272]. As shown in Table 5.32, there are large amounts of low-cost feedstocks, such as greases and rendered animal fat (11.6 billion lbs), which can be used in biodiesel production. Some estimates state that 2.3 billion lbs/yr of poultry fat may account for 300 MMgy of biodiesel, while 2.75 billion lbs/yr of yellow grease account for similar quantities. The inexpensive feedstocks, waste cooking oils, restaurant grease and animal fats, represent about one-third of the US total fats and oil production (about 35 billion lbs, Table 5.32 Total annual US production of fats, oils and grease (2001) (adapted from ref. [300]) Vegetable oil production (Bgy)

Animal fats (Bgy)

Soybean Peanut Sunflower Cottonseed Corn Others

2.44 0.03 0.13 0.13 0.32 0.09

Inedible tallow Lard and grease Yellow grease Poultry fat Edible tallow

0.51 0.17 0.35 0.30 0.21

Total vegetable oil

3.15

Total animal fat

1.55

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with SBO making up some 50%). If all of the US greases and animal fats were converted to biodiesel it would replace about 1.5 Bgy of diesel fuel. However, these materials are currently devoted to other industrial markets and animal feed. In practice, out of the 0.35 Bgy of yellow grease and 1.2 Bgy of other animal fats collected in the US (see Table 5.32) only 3–8% or 45–125 MMgy will eventually be available for biodiesel [301]. The US Census Bureau has recently begun tracking the use of animal fats and greases in biodiesel production. In 2007, 173.1 million lbs of animal fats and greases were used for US biodiesel production (or about 4% of total feedstock). The US biodiesel industry consumed approximately 2% of total US production of fats and greases in 2007. In June 2008 only 25 million lbs of yellow grease was used for biodiesel production. There is even more trap grease than yellow grease in the US. Compared with yellow grease, the brown grease industry is even more highly fragmented. Collection is problematic (with up to 95% consisting of water), as well as the transformation into biodiesel. With the new US blenders tax credit extension applicable to recycled vegetable oils, more waste vegetable oils will be converted. In a 300 kt/yr Tyson Foods, Inc./Syntroleum (USA) joint venture fat-to-liquids project, tallow will first be gasified to CO and H2 and then catalytically converted to alkanes (Fischer-Tropsch). Tyson Foods (USA) produces 1 Mt/yr animal fat. In Europe, Argent Energy operates one of the world’s largest biodiesel plants in Motherwell (Scotland), where it converts tallow from the meat industry and used cooking oil into biodiesel, which supplies 5% of Scotland’s diesel requirements. Ireland’s first commercial-scale 30 kt/yr biodiesel plant operated by Green Biofuels Ireland Ltd (Wexford County) uses inedible and waste oils. In Abu Dhabi, the 3 MMgy facility of Emirates Biodiesel LLC (Al Ain) will use waste cooking oil and other inedible oils as feedstocks. Although various oilseeds are grown in Australia and a multi-feedstock blend of oils (RSO, SNO, SBO) may be used for biodiesel, Australian production currently (2005) originates mainly from recycled frying oil and animal fats. A Transpacific Industries Group (TPI)/Australian Renewable Fuels (ARF) joint venture (50/50) intends producing 45 ML biodiesel in Brisbane using up to 50% of the feedstock through TPI’s used cooking oil collection business (2H 2007). BP will produce 100 ML of biofuels at its Bulwer Island refinery in Queensland; at least 50% will be derived from animal fat using new technology that uses hydrogen to convert tallow into biodiesel (see Section 15.4). Brazil’s Bertin Group, a leading cattle farmer in the beef industry, produces 100 kt/yr of bovine tallow diesel in the state of São Paulo (as from June 2006), or almost 14% of the biodiesel required to comply with the country’s B2 target effective January 2006. Brazil has a cattle herd of 190 million.

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205

5.10.2 Highly acidic feedstocks Soapstock (SS) is a co-product of the extraction of oilseeds to produce edible oils. Annual US soybean soapstock production exceeds 450 kt. Soapstock, consisting of an emulsion of water, acylglycerols, phosphoglycerols and free fatty acids, cannot be converted into FAME by conventional alkaline catalysis, but requires acid-catalysed esterification and transesterification. As the resulting ester product contains high amounts of unsaponifiable matter [302], the need for purification in order to meet the required industry standards easily leads to uneconomic operation. Also acid oils, by-products of alkali or physical refining of crude oils and fats, may be used as feedstock. Acid oil obtained by acidulation of soapstock contains free fatty acids, acylglycerols and other lipophilic compounds. Acid oils, which are cheaper than raw and refined oils, have been considered as an alternative source of biodiesel fuel [303, 304]. Transformation of soapstocks and acid oils into FAAEs is described in Sections 9.3.1 and 9.6. Among the industrial waste oils suitable for production of biofuel, mention should be made of tall oil colophony (a mixture of free fatty acids and rosin acids with varying degrees of purity). Tall oil finds a number of uses in industries for the production of lacquers, paints, hydrophobic coatings, inks, etc. [305]. Some 25% of all plant-derived fatty acids used in the coatings industry comes from tall oil. Tall oil (from Swedish ‘tallolja’ or pine oil), also called liquid rosin, is a viscous yellow-black odorous liquid obtained as a by-product of the Kraft (or sulphate) process of wood pulp manufacture. Manufacturing of paper using the Kraft Mill process generates liquids called black liquor and black liquor soap. Black liquor is the resulting caustic from that process and consists of an aqueous solution of lignin residues, hemicellulose and inorganic chemicals used in pulping. Canada has a large black liquor resource (24 Mt of dry matter). Black liquor soaps are mainly composed of fatty and rosin acid soaps and unsaponifiable matter and minor amounts of partially soluble inorganic salts, lignin, mercaptans and polysulphides. Through acidulation black liquor soaps are transformed into crude tall oil (CTO), consisting of 20–60% fatty acids (TOFA) and 20–65% resin acids (TORA), together with some fatty alcohols, sterols and other alkyl hydrocarbon derivatives. In turn, CTO (AV 100–175 mg KOH/g; SN 120–180 mg KOH/g; IV 140–170 g I2/hg) can be processed, e.g. using distillation, to produce different fractions of distilled tall oil [306]. Tall oil fatty acid (TOFA) is cheap, consists mostly of oleic acid, and is a source of volatile fatty acids. TOFA is a low-cost alternative to tallow fatty acids for production of soaps and lubricants but without much of a price advantage over other such biodiesel feedstocks. World production of tall oil is 1.2 Mt/ yr (60% from the US). Tall oil fatty acids are easily converted into their methyl esters by reaction with methanol, whereas the resin acids are virtually

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unesterified [277, 307]; see Section 9.7. Feng [308] described a tall oil-based cetane enhancer for diesel fuels.

5.11

Bibliography

W. Thurmond, Algae 2020: Next Generation Biofuels Markets and Commercialization Outlook, Emerging Markets Online, Houston, TX (2009). D. Ehrensing, Oilseed Crops: Flax, Oregon State University Extension Service, EM 8952-E (2008). D. Ehrensing, Oilseed Crops: Camelina, Oregon State University Extension Service, EM 8953-E (2008). C. Hou and J.-F. Shaw (eds), Biocatalysis and Biotechnology for Functional Foods and Industrial Products, AOCS Press, Urbana, IL (2007). Y. Basiron, B.S. Jalani and K.W. Chan (eds), Advances in Oil Palm Research, Malaysian Palm Oil Board, Kuala Lumpur (2007), 2 vols. WWF Deutschland (ed.), Rain Forest for Biodiesel? Ecological Effect of Using Palm Oil as a Source of Energy, WWF Deutschland, Frankfurt (2007). F. Shahidi (ed.), Maximising the Value of Marine By-products, Woodhead Publishing, Cambridge (2007). R.S. Kureel, C.B. Singh, A.K. Gupta and A. Pandey, Jatropha. An Alternate Source for Biodiesel, National Oilseeds and Vegetable Oils Development Board, Gurgaon (2007). R.K. Gupta and V.D. Pandey, Advances in Applied Phycology, Daya Publishing House, Delhi (2007). D. Boskou (ed.), Olive Oil: Chemistry and Technology, AOCS Press, Urbana, IL (2006). R.A. Della Porta (ed.), Edible Oils Manual, AOCS Press, Urbana, IL (2006). D. Firestone (ed.), Physical and Chemical Characteristics of Oils, Fats, and Waxes, AOCS Press, Urbana, IL (2006). M.M. Mossoba, J.K.G. Kramer, J.T. Brenna and R.E. McDonald (eds), Lipid Analysis and Lipidomics: New Techniques and Applications, AOCS Press, Urbana, IL (2006). W.C. Byrdwell (ed.), Modern Methods for Lipid Analysis by Liquid Chromatography/Mass Spectrometry and Related Techniques, AOCS Press, Urbana, IL (2005). R.A. Andersen (ed.), Algal Culturing Techniques, Elsevier Academic Press, Burlington, MA (2005). G. Pahl, Biodiesel: Growing a New Energy Economy, Chelsea Green Publishing Co., White River Junction, VT (2005). Z. Cohen and C. Ratledge (eds), Single Cell Oils, AOCS Press, Champaign, IL (2005).

Feedstocks for biodiesel production

207

A. Richmond (ed.), Handbook of Microalgal Culture: Biotechnology and Applied Phycology, Blackwell Science, Oxford (2004). J.A. Duke, Handbook of Energy Crops, Purdue University Center for New Crops and Plant Products, West Lafayette, IN (2003); http://www.hort. purdue.edu/newcrop. J.A. Kinast, Production of Biodiesel from Multiple Feedstocks and Properties of Biodiesels and Biodiesel/Diesel Blends, NREL, Golden, CO (2003). J. Krahl, Rapsölmethylester in dieselmotorischer Verbrennung – Emissionen, Umwelteffekte, Optimierungspotenziale, Landbauforschung Völkenrode, Sonderheft 233, Braunschweig (2002). A. Munack and J. Krahl (eds), Biodiesel. Potenziale, Umweltwirkungen, Praxiserfahrungen, Landbauforschung Völkenrode, Sonderheft 239, Braunschweig (2002). F.D. Gunstone (ed.), Vegetable Oils in Food Technology: Composition, Properties and Uses, CRC Press, Boca Raton, FL (2002). F. Chen and Y. Jiang (eds), Algae and their Biotechnological Potential, Kluwer Academic Publishers, Dordrecht (2001). K.S. Tyson, J. Brown and M. Moora, Industrial Mustard Crops for Biodiesel and Biopesticides, NREL, Golden, CO (2000). J.L. Harwood and R. Aparicio (eds), Handbook of Olive Oil, Aspen Publishers, Gaithersburg, MD (2000). K.F. Kiple and C.K. Ornelas-Kiple (eds), The Cambridge World History of Food, Cambridge University Press, New York, NY (2000). V. Moses, R.E. Cape and D.G. Springham (eds), Biotechnology: The Science and the Business, Harwood, New York, NY (1999). M.C. Flickinger and S.W. Drew (eds), Encyclopedia of Bioprocess Technology: Fermentation, Biocatalysis and Bioseparation, John Wiley & Sons, Inc., New York, NY (1999). Z. Cohen (ed.), Chemicals from Microalgae, Taylor & Francis, London (1999). S. Roller and S. Harlander (eds), Genetic Modification in the Food Industry, Blackie, London (1998). N. Martini and J. Schell (eds), Plant Oils as Fuels. Present State of Science and Future Developments, Springer-Verlag, Berlin (1998). M. Bockisch, Fats and Oils Handbook, AOCS Press, Urbana, IL (1998). J. Sheehan, T. Dunahay, J. Benemann and P. Roessler, A Look Back at the US Department of Energy’s Aquatic Species Program – Biodiesel from Algae, NREL/TP-580-24190, National Renewable Energy Laboratory, Golden, CO (1998). N. El Bassam, Energy Plant Species: Their Use and Impact on Environment and Development, Earthscan Ltd, London (1998). D. Barranco, D. Fernández-Escobar and L. Rallo (eds), El Cultivo del Olivo, Ediciones Mundi-Prensa, Madrid (1997).

208

Biodiesel science and technology

R.J. Hamilton and R.D. Rice (eds), Fish Oil: Technology, Nutrition and Marketing, The Oily Press, Bridgwater, UK (1995). C. Van den Hoek, D.G. Mann and H.M. Jahns, Algae: An Introduction to Phycology, Cambridge University Press, Cambridge (1995). D.S. Kimber and D.I. McGregor (eds), Brassica Oilseeds – Production and Utilization, CABI Publishing, Wallingford (1995). F.D. Gunstone, J.L. Harwood and F.B. Padley, The Lipid Handbook, 2nd edn, Chapman & Hall, London (1994). E.W. Becker, Microalgae. Biotechnology and Microbiology, Cambridge University Press, Cambridge (1994). K.R.M. Anthony, J. Meadly and G. Röbbelen (eds), New Crops for Temperate Regions, Chapman & Hall, London (1993). A. Guerrero, Nueva Olivicultura, Ediciones Mundi-Prensa, Madrid (1991). H. Niewiadomski, Rapeseed Chemistry and Technology, Elsevier, New York, NY (1990). G. Röbbelen, R.K. Downey and A. Ashri (eds), Oil Crops of the World, McGraw-Hill, New York, NY (1989). A. Kiritsakis, The Olive Oil, Agricultural Cooperative Editions, Thessaloniki (1988). C.W.C. Hartley, The Oil Palm (E. guineensis Jacq.), Longman Group Ltd, New York, NY (1988). T. Stadler, J. Morillon, M.C. Verdus, W. Karamanos, H. Morvan and D. Christiaen (eds), Algal Biotechnology, Elsevier Applied Science, London (1988). D.T. Plummer, An Introduction to Practical Biochemistry, McGraw-Hill, London (1987). A. Richmond (ed.), Handbook of Microalgal Mass Culture, CRC Press, Boca Raton, FL (1986). W.D.P. Stewart (ed.), Algal Physiology and Biochemistry, University of California Press, Berkeley, CA (1974). Soya & Oilseed Bluebook Directory, Soyatech Inc., Bar Harbour, ME (yearly).

5.12

References

[1] G. Knothe, R.O. Dunn and M.O. Bagby, Biodiesel: The Use of Vegetable Oils and Their Derivatives as Alternative Diesel Fuels, Oil Chemical Research, National Center for Agricultural Utilization Research, Agricultural Research Service, US Dept. of Agriculture. Available at: http://www.journeytoforever.org/biofuel_library/ VegetableOilsKnothe.pdf. [2] W. Körbitz, Review on commercial production of biodiesel world-wide. Fachtagung Biodiesel: Optimierungspotentiale und Umwelteffekte, Landbauforschung Völkenrode, Sonderheft 190, Braunschweig (1998) 3–10.

Feedstocks for biodiesel production

209

[3] M. Mittelbach and C. Remschmidt (eds), Biodiesel – The Comprehensive Handbook, Boersedruck, Vienna (2004). [4] D. Firestone (ed.), Physical and Chemical Characteristics of Oils, Fats and Waxes, AOCS Press, Urbana, IL (2006). [5] DGF-Standards. Deutsche Einheitsmethoden zur Untersuchung von Fetten, Fettprodukten, Tensiden und verwandte Stoffen. Deutsche Gesellschaft für. Fettwissenschaften e.V., Münster, Wissenschaftliche Verlagsgesellschaft GmbH, Stuttgart (1989). [6] M.A. Hanna, L. Isom and J. Campbell, Biodiesel: Current perspectives and future, J. Sci. Ind. Res. 64 (2005) 854–7. [7] The Economist’s Intelligence Unit, World Commodity Forecasts Foods, Feedstuffs and Beverages (1 Aug. 2007). [8] J. Walton, The fuel possibilities of vegetable oils, Gas Oil Power 33 (1938) 167–8. [9] M.J.T. Reaney, P.B. Hertz and W.W. McCalley, Vegetable oils as biodiesel, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 6 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 223–57. [10] Biofuel Market Worldwide, Bharat Book Bureau, Navi Mumbai (2006). [11] W. Thurmond, Biodiesel 2020. A Global Market Survey, Emerging Markets Online, Houston, TX (2008). [12] A.K. McElroy, Bees essential for biodiesel, Biodiesel Mag. 5(12) (2008) 76– 83. [13] M.A. Simeh, Comparative advantage of the European rapeseed industry vis-à-vis other oils and fats producers, Oil Palm Ind. Econ. J. 4 (2004) 14. [14] J.M. Encinar, J.F. González, E. Sabio and M.J. Ramiro, Preparation and properties of biodiesel from Cynara cardunculus L. oil, I&EC Res. 38 (1999) 2927–31. [15] D. De Oliveira, M. Di Luccio, C. Faccio, C. Dalla Rosa, J.P. Bender, N. Lipke, S. Menoncin, C. Amroginski and J.V. De Oliveira, Optimization of enzymatic production of biodiesel from castor oil in organic solvent medium, Appl. Biochem. Biotechnol. 113–116 (2004) 771–80. [16] G. Steinke, R. Kirchhoff and K.D. Mukherjee, Lipase-catalyzed alcoholysis of crambe oil and camelina oil for preparation of long-chain esters, J. Am. Oil Chem. Soc. 77(4) (2000) 361–6. [17] S. Shah, S. Sharma and M.N. Gupta, Biodiesel preparation by lipase-catalyzed transesterification of Jatropha oil, Energy Fuels 18 (2004) 154–9. [18] W. Haas, H. Sterk and M. Mittelbach, Novel 12-desoxy-16-hydroxyphorbol diesters isolated from the seed oil of Jatropha curcas, J. Nat. Prod. 65 (2002) 1434–40. [19] S. Kumar, A.K. Gupta and S.N. Naik, Conversion of non-edible oil into biodiesel, J. Sci. Ind. Res. 62 (2003) 124–32. [20] S. Kaul, A. Kumar, A.K. Bhatnagar, H.B. Goyal and A.K. Gupta, Biodiesel: a clean and sustainable fuel for the future. Scientific strategies for production of non-edible vegetable oils for use as biofuels, All India Seminar on National Policy on Non-edible Oils as Biofuels, SUTRA, I.I. Sc., Bangalore (2003). [21] M. Johnston and T. Holloway, A global comparison of national biodiesel production potentials, Environm. Sci. Technol. 41 (2007) 7967. [22] J. Gressel, Transgenics are imperative for biofuel crops, Plant Sci. 174 (2008) 246–63.

210

Biodiesel science and technology

[23] F.D. Gunstone, Production and consumption of rapeseed oil on a global scale, Eur. J. Lipid Sci. Technol. 103 (2001) 447–9. [24] G.C. Buzza, Plant breeding, in Brassica Oilseeds Production and Utilization (D. Kimber and D.I. McGregor, eds), CAB International, Wallingford (1995), pp. 153–77. [25] C. Benning, unpublished results (2008). [26] D.C. Taylor, V. Katavic, J. Zou, S.L. MacKenzie and W.A. Keller, Improvement of oil content, erucic acid content and seed yield in field-tested transgenic rapeseed, PBI Bulletin (2002), Issue 1. [27] C.E. Temple-Heald, Sourcing erucic acid for the industrial market, Lipid Technol. Newsl. 6 (2000) 59–63. [28] H.L. Bhardwaj and A.A. Hamama, Oil, erucic acid, and glucosinolate contents in winter hardy rapeseed germplasms, Ind. Crops Prod. 12 (2000) 33–8. [29] M. Wörgetter, H. Prankl, J. Rathbauer and D. Bacovsky, Local and Innovative Biodiesel, Final report, ALTENER project No. 4.1030/C/02-022. HBLFA Francisco Josephinum/BLT Biomass-Logistics-Technology, Wieselburg (2006). [30] R. Przybylski, T. Mag, N.A.M. Eskin and B.E. McDonald, Canola oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 61–121. [31] C. Anderson, Count on canola for your biodiesel, Biodiesel Mag. 5(2) (2008) 186–90. [32] M. Cardone, M. Mazzoncini, S. Menini, V. Rocco, A. Senatore, M. Seggiani and S. Vitolo, Brassica carinata as an alternative oil crop for the production of biodiesel in Italy: agronomic evaluation, fuel production by transesterification and characterization, Biomass Bioen. 25 (2003) 623–36. [33] A. Bouaid, Y. Diaz, M. Martínez and J. Aracil, Pilot plant studies of biodiesel production using Brassica carinata as raw material, Catal. Today 106 (2005) 193–6. [34] D.J. Murphy (ed.), Design Oil Crops: Breeding, Processing and Biotechnology, VCH-Verlag, Weinheim (1994). [35] R. Scarth, P.B.E. McVetty, S.R. Rimmer and J. Daun, Breeding of special oil quality in canola/rapeseed: The University of Manitoba program, in Seeds Oils Future (S.L. MacKenzie and D.C. Taylor, eds), AOCS Press, Champaign, IL (1992), pp. 171–6. [36] W. Friedt and W. Lühs, Recent developments and perspectives of industrial rapeseed breeding, Fett/Lipid 100 (1998) 219–26. [37] D.S. Knutzon, T.R. Hayes, A. Wyrick, H. Xiong, H.M. Davies and T.A. Voelker, Lysophosphatidic acid acyltransferase from coconut endosperm mediates the insertion of laurate at the sn-2 position of triacylglycerols in lauric rapeseed oil and can increase total laurate levels, Plant Physiol. 120 (1999) 739–46. [38] J.C.P. Dribnenki, A.G. Green and G.N. Atlin, Linola 989 low linolenic flax, Can. J. Plant Sci. 76(2) (1996) 329–32. [39] J.B. Mugendi, C.A. Sims, D.W. Gorbet and S.F. O’Keefe, Flavor stability of high-oleic peanuts stored at low humidity, J. Am. Oil Chem. Soc. 75(2) (1998) 21–5. [40] R.S. Jonnala, N.T. Dunford and K.E. Dashiell, New high-oleic peanut cultivars grown in the Southwestern United States, J. Am. Oil Chem. Soc. 82(2) (2005) 125–8. [41] U. Biermann, W. Friedt, S. Lang, W. Lühs, G. Machmüller, J.O. Metzger, M. Rüsch

Feedstocks for biodiesel production

[42]

[43]

[44]

[45]

[46]

[47] [48]

[49]

[50]

[51]

[52] [53] [54] [55]

[56]

211

gen. Klaas, H.J. Schäfer and M.P. Schneider, New synthesis with oils and fats as renewable raw materials for the chemical industry, in Biorefineries – Industrial Processes and Products, Vol. 2 (B. Kamm, R. P. Gruber and M. Kamm, eds), Wiley-VCH, Weinheim (2006) pp. 253–89. C. Stoll, W. Lühs, M.K. Zarhloul and W. Friedt, Genetic modification of saturated fatty acids in oilseed rape (Brassica napus), Eur. J. Lipid Sci. Technol. 107 (2005) 244–8. D.S. Knutzon, G.A. Thompson, S.E. Radke, W.B. Johnson, V.C. Knauf and J.C. Kridl, Modification of Brassica seed oil by antisense expression of a stearoylacyl carrier protein desaturase gene, Proc. Natl. Acad. Sci. U.S.A. 89(7) (1992) 2624–8. D.L. Auld, M.K. Heikkinen, D.A. Erickson, J.L. Sernyk and J.E. Romero, Rapeseed mutants with reduced levels of polyunsaturated fatty acids and increased levels of oleic acid, Crop Sci. 32 (1992) 657–62. W.D. Hitz, N.S. Yadav, R.S. Reiter, C.J. Mauvais and A.J. Kinney, Reducing polyunsaturation in oils of transgenic canola and soybean, in Plant Lipid Metabolism (J.-C. Kader and P. Mazliak, eds), Kluwer Academic Publishers, Dordrecht (1995), pp. 506–8. J. Osorio, J. Fernández-Martínez, M. Mancha and R. Garcés, Mutant sunflowers with high concentration of saturated fatty acids in the oil, Crop. Sci. 35 (1995) 739–42. G. Cole, G.S. Coughlan, N. Frey, J. Hazebroek and C. Jennings, New sunflower and soybean cultivars for novel vegetable oil types, Fett/Lipid 100 (1998) 177–81. X. Ndzana, W.R. Fehr, G.A. Welke, E.G. Hammond, D.N. Duvick and S.R. Cianzio, Influence of reduced palmitate content on agronomic and seed traits of soybean, Crop Sci. 34 (1994) 646–9. J.R. Booth Jr., R.M. Broglie, W.D. Hitz, A.J. Kinney, S. Knowlton and S.A. Sebastian (to E.I. Du Pont de Nemours & Co.), Novel gene combinations that alter the lipid profile of soybean oil, resulting in oils useful for margarine and other spreads, PCT Int. Publ. No. WO 99/58689 (18 Nov. 1999). C. Ntiamoah, G.G. Rowland and D.C. Taylor, Inheritance of elevated palmitic acid in flax and its relationship to the low linolenic acid, Crop Sci. 35 (1995) 148–52. T.A. Voelker, T.R. Hayes, A.M. Cranmer, J.C. Turner and H.M. Davies, Genetic engineering of a quantitative trait: metabolic and genetic parameters influencing the accumulation of laurate in rapeseed, Plant J. 9 (1996) 229–41. B. Rücker and G. Röbbelen, Impact of low linolenic acid content on seed yield of winter oilseed rape (Brassica napus), Plant Breed. 115 (1996) 226–30. F.D. Gunstone, Oilseed crops with modified fatty acid composition, J. Oleo Sci. 50 (2001) 269–79. K.C. Walker and E.J. Booth, Agricultural aspects of rape and other Brassica products, Eur. J. Lipid Sci. Technol. 103 (2001) 441–6. V. Katavic, W. Friesen, D.L. Barton, K.K. Gossen, E.M. Giblin, T. Luciw, J. An, J. Zou, S.L. MacKenzie, W.A. Keller, D. Males and D.C. Taylor, Utility of the Arabidopsis FAEI and yeast SLC-1 genes for improvements in erucic acid and oil content in rapeseed, Biotechnological Aspects: Fatty Acids, Proc. 14th Intl. Symp. on Plant Lipids, Cardiff (23–28 July 2000), p. 935; Crop. Sci. 41 (2001) 739–47. N.D. Sasongko and C. Möllers, Toward increasing erucic acid content in oilseed

212

[57]

[58] [59] [60]

[61]

[62]

[63] [64]

[65]

[66]

[67] [68] [69]

[70]

[71] [72] [73]

[74]

Biodiesel science and technology rape (Brassica napus L.) through the combination with genes for oleic acid, J. Am. Oil Chem. Soc. 82 (2005) 445–9. L.W. Kleingartner, NuSun sunflower oil: redirection of an industry, in Trends in New Crops and New Uses (J. Janick and A. Whipkey, eds), ASHS Press, Alexandria, VA (2002) 135–8. M.K. Gupta, NuSun oil – success and challenges, Inform 18(9) (2007) 639–41. W. Lühs and W. Friedt, Designer oil crops: breeding, processing and biotechnology, in Designer Oil Crops (D.J. Murphy, ed.). VCH, Weinheim (1994). J.M. Martínez-Rivas, P. Sperling, W. Lühs and E. Heinz, Spatial and temporal regulation of three different microsomal oleate desaturase genes (FAD2) from normal-type and high-oleic varieties of sunflower (Helianthus annuus L.), Mol. Breed. 8 (2001) 159–68. Z. Flagella, T. Rotunno, E. Tarantino, R. Di Caterina and A. De Caro, Changes in seed yield and oil fatty acid composition of high oleic sunflower (Helianthus annuus L.) hybrids in relation to the sowing date and the water regime, Eur. J. Agron. 17 (2002) 221–30. M.A. Grompone, Sunflower oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 655–730. A.J. Kinney and T.E. Clemente, Modifying soybean oil for enhanced performance in biodiesel blends, Fuel Proc. Technol. 86 (2005) 1137–47. L. Velasco, B. Pérez-Vich and J.M. Fernández-Martínez, A rapid and simple approach to identify different sunflower oil types by means of near-infrared reflectance spectroscopy, J. Am. Oil Chem. Soc. 75(12) (1998) 1883–8. E.G. Hammond, L.A. Johnson, C. Su, T. Wang and P.J. White, Soybean oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 577–653. J.J. Fillatti, N.A. Bringe and K. Dehesh (to Monsanto Technology LLC), Nucleic acid constructs and methods for producing altered seed oil compositions, US Pat. Appl. 2004/0107460 A1 (3 June 2004). C. Tompkins and E.G. Perkins, Frying performance of low-linolenic acid soybean oil, J. Am. Oil Chem. Soc. 77(3) (2000) 223–9. G. Fuller, M.J. Diamond and T.H. Applewhite, High-oleic safflower oil. Stability and chemical modification, J. Am. Oil Chem. Soc. 44 (1967) 264–6. C.M. Cherrak, V.R. Pantalone, E.J. Meyer, D.L. Ellis, S.L. Melton, D.R. West and J.R. Mount, Low-palmitic, low-linolenic soybean development, J. Am. Oil Chem. Soc. 80 (2003) 539–43. N.A. Bringe, Soybean oil composition for biodiesel, in The Biodiesel Handbook (G. Knothe, J.Van Gerpen and J. Krahl, eds) AOCS Press, Urbana, IL (2005), pp. 161–4. USDA Foreign Agricultural Service, Oilseeds: World Markets and Trade (Sept. 2008). USDA Economic Research Service, Oil Crops Outlook (Sept. 2008). I. Maizura, N. Rajanaidu, A.H. Zakri and S.C. Cheah, Assessment of genetic diversity in oil palm (Elaeis guineensis Jacq.) using Restriction Fragment Length Polymorphism (RFLP), Genetic Resourc. Crop Evol. 53 (2006) 187–95. B.S. Jalani, S.C. Cheah, N. Rajanaidu and A. Darus, Improvement of palm oil through breeding and biotechnology, J. Am. Oil Chem. Soc. 74 (1997) 1451–5.

Feedstocks for biodiesel production

213

[75] Y. Basiron, Palm oil, in Bailey’ s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 333–429. [76] D. Mistry, Why palm needs biofuel demand for its long term success, Paper presented at 2nd Intl. Palm Oil Trade Fair & Seminar 2008, Kuala Lumpur (24–26 Aug 2008). [77] A. Kushairi, N. Rajanaidu and B.S. Jalani, Genetic variation of iodine value, carotene and tocotrienols in palm oil and its application in pharmaceuticals, Malaysian Oil Sci. Technol. 1(2) (2002) 92–105. [78] Y.B. Che Man, M.H. Moh and F.R. Van de Voort, Determination of free fatty acids in crude palm oil and refined-bleached-deodorized palm olein using Fourier transform infrared spectroscopy, J. Am. Oil Chem. Soc. 76(14) (1999) 485–90. [79] G. Chavanne, Procédé de transformation d’huiles végétales en vue de leur utilisation comme carburants, Belg. Pat. 422,877 (31 Aug. 1937). [80] M. Van den Abeele, L’huile de palme. Matière première pour la préparation d’un carburant lourd utilisable dans les moteurs à combustion interne, Bull. Agr. Congo Belge 33 (1942) 3–90. [81] Y.M. Choo, A.N. Ma and Y. Basiron, Palm oil methyl esters as fuel: palm diesel, PORIM Techn. Note No. 17 (Oct. 1993). [82] Y.M. Choo, S.F. Cheng, C.L. Yung, H.L.N. Lau, A.N. Ma and Y. Basiron (to Malaysian Palm Oil Board), Palm diesel with low pour point, Malaysian Pat. SG 142118 A1 (28 May 2008). [83] N. Rettenmaier, Life-cycle assessment of palm oil biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [84] H. Helms, G.A. Reinhardt and N. Rettenmaier, Bioenergie aus Palmöl; Ökologische Chancen und Risiken, in Energiewirtsch. Tagesfragen Ztschr. f. Energiewirtsch., Recht, Techn. & Umwelt 56(11) (2006) 70–3. [85] A. Hooijer, M. Silvius, H. Wösten and S. Page, Peat-CO2: assessment of CO2 emissions from drained peatlands in SE Asia, Delft Hydraulics Techn. Rept. No. Q3943, Delft (2006). [86] J. Qiu, A sustainable generation?, Chem. World 8(6) (2008) 49–52. [87] O. Overeem, G.J.H. Buisman, J.T.P. Derksen, F.P. Cuperus, L. Molhoek, W. Grisnich and C. Goemans, Seed oils rich in linolenic acid as renewable feedstock for environment-friendly crosslinkers in powder coatings, Ind. Crops Prod. 10 (1999) 157–65. [88] A.G. Green, A mutant genotype of flax (Linum usitatissimum L.) containing very low levels of linolenic acid in its seed oil, Can. J. Plant Sci. 66 (1986) 499–503. [89] G.G. Rowland, An EMS-induced low-linolenic-acid mutant in McGregor flax (Linum usitatissimum L.), Can. J. Plant Sci. 71 (1991) 393–6. [90] C. Stenberg, M. Svensson and M. Johansson, A study of the drying of linseed oils with different fatty acid patterns using RTIR-spectroscopy and chemiluminescence (CL), Ind. Crops Prod. 21 (2005) 263–72. [91] A.G. Green and D.R. Marshall, Isolation of induced mutants in linseed (Linum usitatissimum) having reduced linolenic acid content, Euphytica 33 (1984) 321–8. [92] R. Steiss, A. Schuster and W. Friedt, Development of linseed for industrial purposes via pedigree-selection and haploid-technique, Ind. Crops Prod. 7 (1998) 303–9. [93] R. Przybylski, Flax oil and high linolenic oils, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 281–301.

214

Biodiesel science and technology

[94] Plant Biotechnology Institute (NRCC), Diversification of Canadian oilseeds. Part 1: Adding value to the oil, PBI Bulletin (2002), Issue 1. [95] J. Smith, Safflower oil, in Bailey’s Industrial Oil and Fat Products, 6th ed., Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 491–536. [96] A. Is˛ iğugür, F. Karaosmanoğlu and H.A. Aksoy, Methyl ester from safflower seed oil of Turkish origin as a biofuel for diesel engines, Appl. Biochem. Biotechnol. 45/46 (1994) 103–12. [97] E.C. Canapi, Y.T.V. Agustin, E.A. Moro, E. Pedroso Jr. and M.L.J. Bendano, Coconut oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 123–47. [98] R.D. Abigor, P.O. Uadia, T.A. Foglia, M.J. Haas, K.C. Jones, E. Okpefa, J.U. Obibuzor and M.E. Bafor, Lipase-catalysed production of biodiesel fuel from some Nigerian lauric oils, Biochem. Soc. Trans. 28 (2000) 979–81. [99] R. Diesel, The Diesel oil-engine, Engineering 93 (1912) 395–406. [100] H. E. Pattee, Peanut oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 431–63. [101] A.J. Norden, D.W. Gorbet, D.A. Knauft and C.T. Young, Variability in oil quality among peanut genotypes in the Florida breeding program, Peanut Sci. 14(1) (1987) 7–11. [102] T.G. Isleib, C.T. Young and D.A. Knauft, Fatty acid genotypes of five Virginiatype peanut cultivars, Crop Sci. 36(3) (1996) 556–8. [103] A. Mohammed, Production and characterization of biodiesel from groundnut oil, Proc. 7th Ann. Engng. Conference, Minna, Nigeria (2006). [104] S. Chandraju and B.K. Prathima, Biodiesel of groundnut oil: a safe alternative fuel in the transport sector, Asian J. Chem. 16 (2004) 1811–18. [105] D. Firestone, Olive oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 303–31. [106] R.A. Moreau, Corn oil, in Bailey’s Industrial Oil and Fat Products, 6th ed., Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 149–72. [107] S. Fachini, The problem of olive oils as fuels and lubricants, Chim. Ind. (Special Number) (1933), pp. 1078–9. [108] M.P. Dorado, E. Ballesteros, M. Mittelbach and F.J. López, Kinetic parameters affecting the alkali-catalyzed transesterification process of used olive oil, Energy Fuels 18 (2004) 1457–62. [109] A.J. Yuste and M.P. Dorado, A neural network approach to simulate biodiesel production from waste olive oil, Energy Fuels 20 (2006) 399–402. [110] H.A. Aksoy, I. Kahraman, F. Karaosmanoğlu and H. Civelekoğlu, Evaluation of Turkish sulphur olive oil as an alternative diesel fuel, J. Am. Oil Chem. Soc. 65(6) (1988) 936–8. [111] A. Benzaria, N. Meskini, M. Dubois, M. Croset, G. Némoz, M. Legarde and A.-F. Prigent, Effect of dietary argan oil on fatty acid composition, proliferation, and phospholipase D activity of rat thymocytes, Nutrition 22 (2006) 628–37. [112] J.T. Barminas, H.M. Maina, S. Tahir, D. Kubmarawa and K. Tsware, A preliminary investigation into the biofuels characteristics of tigernut (Cyperus esculentus) oil, Bioresour. Technol. 79 (2001) 87–9. [113] H.Y. Zhang, M.A. Hanna, Y. Ali and L. Nan, Yellow nut-sedge (Cyperus esculentus L.) tuber oil as a fuel, Ind. Crops Prod. 5 (1996) 177–81. [114] R.D. O’Brien, L.A. Jones, C.C. King, P.J. Wakelyn and P.J. Wan, Cottonseed oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2, (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 173–279.

Feedstocks for biodiesel production

215

[115] C.M. Hunguenard, Dual Fuel for Diesel Engines Using Cottonseed Oil, M. Sc. Thesis, The Ohio State University, Columbus, OH (1951). [116] F.T. Orthoefer, Rice bran oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2, (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 465–89. [117] R.F.-A. Lem, Dual Fuel for Diesel Engines Using Corn Oil with Variable Injection Timing, M.Sc. Thesis, The Ohio State University, Columbus, OH (1952). [118] M. Van Houten, M.J. Beaver, A.M. Eyal, E.J. Fox, J. Ingvalson, N.T. Jakel, D.C. Kotowski, P.J. McWilliams, A. Patist, M.J. Tupy and T.T. Lohrmann (to Cargill Inc. and Renessen LLC), Process for increasing throughput of corn for oil extraction, PCT Int. Publ. No. WO 2005/108533 A2 (17 Nov. 2005). [119] J. Kwiatkowski and M. Cheryan, Recovery of corn oil from ethanol extracts of ground corn using membrane technology, J. Am. Oil Chem. Soc. 82 (2005) 221–7. [120] M. Janes, K. Bruinsma, T. Cooper and D.L. Endres (to VeraSun Energy Corp.), Solvent extraction of oil from distillers dried grains and methods of using extraction products, PCT Int. Publ. No. WO 2008/039859 A2 (3 Apr. 2008). [121] M. Warren, Key considerations when using industrial-grade crude corn oil as a feedstock, Biodiesel Mag. 5(11) (2008) 92–5. [122] M.J. Haas, K.M. Scott, A. McAloon, W. Fee, F.T. Barrows and W.N. Marmer, Biodiesel production by the direct transesterification of the lipids resident in biological materials, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [123] D.E. Carter and J.S. Dordick, Biodiesel production in dedicated fuel alcohol plants, in Liquid Fuels, Lubricants and Additives from Biomass, Proc. Alternative Energy Conf., Kansas City, MO (16–17 June 1994) (B.E. Dale, ed.), ASAE, St. Joseph, MI (1994), pp. 127–33. [124] L.S. Hwang, Sesame oil, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 2 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 537–76. [125] A. Saydut, M.Z. Duz, C. Kaya, A.B. Kafadar and C. Hamanci, Transesterified sesame (Sesamum indicum L.) seed oil as a biodiesel fuel, Bioresour. Technol. 99 (2008) 6656–60. [126] J.F. Morton, The Horseradish tree, Moringa Pterigosperma (Moringaceae) – a boon to arid lands?, Econ. Bot. 45 (1991) 318–33. [127] S. Lalas and J. Tsaknis, Characterization of Moringa oleifera seed oil variety ‘Periyakulam 1’, J. Food Composit. Anal. 15 (2002) 65–77. [128] S.R. Schill, Multidimensional Moringa, Biodiesel Mag. 5(6) (2008) 38–44. [129] P. Ilhan and S. Türkay, Evaluation of tea seed oil for the production of biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [130] N. Kondamudi, S.K. Mohapatra and M. Misra, Spent coffee grounds as a versatile source of green energy, J. Agric. Food Chem. 56 (2008) 11757–60. [131] F. Shahidi and Y. Zhong, Marine mammal oils, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 3 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 259–78. [132] R.G. Ackman, Fish oils, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 3 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 279–317. [133] D.A. Allen, Fish oil compositions, in Fish Oil: Technology, Nutrition and Marketing (R.J. Hamilton and R.D. Rice, eds), P.J. Barnes & Associates, Bridgwater (1995), pp. 95–108.

216

Biodiesel science and technology

[134] A.K. Vickers, High-efficiency FAME analysis using capillary GC, LC·GC Europe Applications Book (Dec. 2007), p. 16. [135] B. Ham, R. Shelton, B. Butter and P. Thionville, Calculating the iodine value for marine oils from fatty acid profiles, J. Am. Oil Chem. Soc. 75 (1998) 1445–6. [136] C. Watkins, Krill oil: next generation source of omega-3s?, Inform 18(9) (2007) 588–92. [137] E.-H. Belarbi, E. Molina and Y. Chisti, A process for high yield and scaleable recovery of high purity eicosapentaenoic acid esters from microalgae and fish oil, Enzyme Microb. Technol. 26 (2000) 516–29. [138] H. Gunnlaugsdottir, M. Järemo and B. Sivik, Process parameters influencing ethanolysis of cod liver oil in supercritical carbon dioxide, J. Supercrit. Fluids 12 (1998) 85–93. [139] A.I. Mohamed, A.S. Hussein, S.J. Bhathena and Y.S. Hafez, The effect of dietary menhaden, olive, and coconut oil fed with three levels of vitamin E on plasma and liver lipids and plasma fatty acid composition in rats, J. Nutrit. Biochem. 13 (2002) 435–41. [140] M. Chautan, F. Chanussot, H. Portugal, A.-M. Pauli and H. Lafont, Effects of salmon oil and corn oil on plasma lipid level and hepato-biliary cholesterol metabolism in rats, Biochim. Biophys. Acta 1046 (1990) 40–5. [141] B. Liaset, K. Julshamn and M. Espe, Chemical composition and theoretical nutritional evaluation of the produced fractions from enzymic hydrolysis of salmon frames with ProtamexTM, Process Biochem. 38 (2003) 1747–59. [142] N. Gámez-Meza, I. Higuera-Ciapara, A.M. Calderon de la Barca, L. VázquezMoreno, J. Noriega-Rodríguez and O. Angulo-Guerrero, Seasonal variation in the fatty acid composition and quality of sardine oil from Sardinops sagax caeruleus of the Gulf of California, Lipids 34 (1999) 639. [143] S. Sathivel, W. Prinyawiwatkul, J.M. King, C.C. Grimm and S. Lloyd, Oil production from catfish viscera, J. Am. Oil Chem. Soc. 80 (2006) 377–82. [144] T. Sun, Z. Xu and W. Prinyawiwatkul, FA composition of the oil extracted from farmed Atlantic salmon (Salmo salar L.) viscera, J. Am. Oil Chem. Soc. 83 (2006) 615–19. [145] T. Lebeau and J.-M. Robert, Diatom cultivation and biotechnologically relevant products. Part II: Current and putative products, Appl. Microbiol. Biotechnol. 60 (2003) 624–32. [146] A.N.A. Aryee, F.R. van de Voort and B.K. Simpson, Application of Fourier transform infrared spectroscopy in the analysis of free fatty acids in fish oils for use as biodiesel feedstock, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [147] S. Sathivel, Fish Oils – Properties and Processing, Alaska Sea Grant College Program, AK-SG-03-01 (2003). [148] J.A. Steigers, G. Seshadri and P.M. Crimp, Demonstrating the use of Alaska fish oil as a feedstock for the commercial production of biodiesel, World Renewable Energy Congress VIII: Linking the World with Renewable Energy, 8th, Denver, CO (29 Aug.–3 Sept. 2004), pp. 189–93. [149] A.N.A. Aryee, F.R. van de Voort, M.O. Ngadi and B.K. Simpson, An inexpensive feedstock for biodiesel production from fishery processing discards and by-products, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [150] H. Vinter, Production of high quality fish oils, in Fish Oil: Technology, Nutrition and Marketing (R.J. Hamilton and R.D. Rice, eds), P.J. Barnes & Associates, Bridgwater (1995), pp. 27–34.

Feedstocks for biodiesel production

217

[151] U. Bathmann, Alfred-Wegener-Institut (AWI) für Polar und Meeresforschung, Polarstern Expedition (2007). [152] Y.-K. Lee, Commercial production of microalgae in the Asia Pacific rim, J. Appl. Phycology 9 (1997) 403–11. [153] M.L. Ghirardi, J.P. Zhang, J.W. Lee, T. Flynn, M. Seibert, E. Greenbaum and A. Melis, Microalgae, green source of renewable H2, Trends Biotechnol. 18 (2000) 506–11. [154] I. Berzin, Hydrogen production with photosynthetic organisms and from biomass derived therefrom, U.S. Pat. Appl. 2005/064577 A1 (24 Mar. 2005). [155] P. Spolaore, C. Jaonnis-Cassan, E. Duran and A. Isambert, Commercial applications of microalgae, J. Biosci. Bioengng. 101 (2006) 87–96. [156] R.A. Bush and K.M. Hall (to Propulsion Logic), Process for the production of ethanol from algae, US Pat. 7,135,308 B1 (14 Nov. 2006). [157] A. Demirbaş, Oily products from mosses and algae via pyrolysis, En. Sources A 28 (2006) 933–40. [158] Q. Wu, X. Li and X. Han, Heterotrophic fermentation of micro-algae for biodiesel production, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [159] P.G. Roessler, L.M. Brown, T.G. Dunahay, D.A. Heacox, E.E. Jarvis, J.C. Schneider, S.G. Talbot and K.G. Zeller, Genetic-engineering approaches for enhanced production of biodiesel fuel from microalgae, ACS Symp. Ser. 566 (1994) 255–70. [160] S. Sawayama, S. Inoue, Y. Dote and S.Y. Yokoyama, CO2 fixation and oil production through microalgae, En. Conv. Managm. 36 (1995) 729–31. [161] N. Nagle and P. Lemke, Production of methyl ester fuel from microalgae, Appl. Biochem. Biotechnol. 24–25 (1990) 355–61. [162] T.G. Dunahay, E.E. Jarvis, S.S. Dais and P.G. Roessler, Manipulation of microalgal lipid production using genetic engineering, Appl. Biochem. Biotechnol. 57/58 (1996) 223–31. [163] J. Sheehan, T. Dunahay, J. Benemann and P. Roessler, A Look Back at the US Department of Energy’s Aquatic Species Program – Biodiesel from Algae, Rept. NREL/TP-580-24190, National Renewable Energy Laboratory, Golden, CO (1998). [164] H. Xu, X. Miao and Q. Wu, High quality biodiesel production from Chlorella protothecoides by heterotrophic growth in fermenters, J. Biotechnol. 126 (2006) 495–507. [165] Q. Wu, X. Miao and H. Xu, Method for preparing biodiesel oil with high quality from microalgae fat by transesterification, Faming Zhuanli Shenqing Gongkai Shuomingshu (2005). [166] M. Gavrilescu and Y. Chisti, Biotechnology – a sustainable alternative for chemical industry, Biotechnol. Adv. 23 (2005) 471–99. [167] T. Minowa, S. Yokoyama, M. Kishimoto and T. Okakura, Oil production from algal cells of Dunaliella tertiolecta by direct thermochemical liquefaction, Fuel 74 (1995) 1735–8. [168] S. Bailey, A. Melis, K.R.M. Mackey, P. Cardol, G. Finazzi, G. van Dijken, G.M. Berg, K. Arrigo, J. Shrager and A. Grossman, Alternative photosynthetic electron flow to oxygen in marine Synechococcus, Biochim. Biophys. Acta 1777 (3) (2008) 269–76. [169] Y. Chisti, Biodiesel from microalgae, Biotechnol. Adv. 25 (2007) 294–306. [170] S.M. Renaud, L.-V. Thinh and D.L. Parry, The gross chemical composition and

218

[171]

[172]

[173]

[174]

[175]

[176]

[177] [178] [179]

[180] [ 181] [182] [183]

[184] [ 185] [186]

[187] [188] [189]

Biodiesel science and technology fatty acid composition of 18 species of tropical Australian microalgae for possible use in mariculture, Aquaculture 170 (1999) 147–59. J. Obbard, S. Balasubramanian, M. Montefrio and T.T. Doan, Screening of tropical microalgae for cellular lipids for use as a biodiesel feedstock, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). M. Shiho, National research project for mass cultivation of oil producing Botryococcus in Japan, Presentation at Intl. Algae Congress, Amsterdam (3–4 Dec. 2008). A. Eyal and C. Raz (to Eyal Research Consultants Ltd), A method for enhanced production of algal biomass, PCT Int. Publ. No. WO 2006/100667 A1 (28 Sept. 2006). T. Manelius, Harvesting algae – use the G-force, an insight in centrifugal algae harvesting, how and why it works!, Presentation at Intl. Algae Congress, Amsterdam (3–4 Dec. 2008). A.O. Alabi, M. Tampier and E. Bibeau, Microalgae Technologies and Processes for Biofuels/Bioenergy Production in British Columbia: Current Technology, Suitability and Barriers to Implementation, Final Rept. to British Columbia Innovation Council (14 Jan. 2009). S.M. Renaud, D.L. Parry, L.-V. Thinh, C. Kuo, A Padovan and N. Sammy, Effect of light intensity on the proximate biochemical and fatty acid composition of Isochrysis sp. and Nannochloropsis oculata for use in tropical aquaculture, J. Appl. Phycol. 3 (1991) 43–53. H. Samejina and J. Myers, On the heterotrophic growth of Chlorella pyrenoidosa, J. Gen. Microbiol. 18 (1958) 107–17. K.L. Terry and L.P. Raymond, System design for the autotrophic production of microalgae, Enzyme Microb. Technol. 7 (1985) 474–87. A.P. Carvalho, L.A. Meireles and F.X. Malcata, Microalgal reactors: a review of enclosed system designs and performances, Biotechnol. Progr. 22 (2006) 1490–506. GreenFuel News, GreenFuel Technologies Corporation, Cambridge, MA (2007). Vertigro Technology: http://www.valcent.net (2007). http://bit.ly/boeing M. Briggs, Widescale biodiesel production from algae, University of New Hampshire Biodiesel Group (Aug. 2004), http://www.unh.edu/p2/biodiesel/article_algae. html. A.R. Braun, Re-use and fixation of CO2 in chemistry, algal biomass and fuel substitutions in the traffic sector, En. Conv. Managm. 37 (1996) 1229–34. J.W. Kram, Algae interests align, Biodiesel Mag. 5 (11) (2008) 60–5. M. Satin, Microalgae, FAO Agriculture Support System Division, AgroIndustries and Post-Harvest Management Service; http://www.fao.org/ag/ags/ Agsi/MICROALG.htm. M.R. Droop, Heterotrophy of carbon, in Botanical Monographs (Oxford) 10 (1974) 530–59. X. Miao and Q. Wu, Biodiesel production from heterotrophic microalgal oil, Bioresour. Technol. 97 (2006) 841–6. W. Xiong, X. Li, J. Xiang and Q. Wu, High-density fermentation of microalga Chlorella protothecoides in bioreactor for microdiesel production, Appl. Microbiol. Biotechnol. 78(1) (2008) 29–36.

Feedstocks for biodiesel production

219

[190] L.A. Zaslavskaia, J.C. Lippmeier, C. Shih, D. Erhardt, A.R. Grossman and K.E. Apt, Trophic conversion of an obligate photoautotrophic organism through metabolic engineering, Science 292 (2001) 2073–5. [191] M. Aresta, A. Dibenedetta, M. Carone, T. Colonna and C. Fragale, Production of biodiesel from macroalgae by supercritical CO2 extraction and thermochemical liquefaction, Environm. Chem. Lett. 3 (2005) 136–9. [192] S. Bastianoni, F. Coppola, E. Tiezzi, A. Colacevich, F. Borghini and S. Focardi, Biofuel potential production from the Ortobello lagoon macroalgae: a comparison with sunflower feedstock, Biomass Bioen. 32 (2008) 619–28. [193] M.I. Wahbeh, Aminoacid and fatty acid profiles of four species of macroalgae from Aqaba and their suitability for use in fish diets, Aquaculture 159 (1997) 101–9. [194] A. Austin, Oceans of biomass, Biomass Mag. 2(9) (2008) 42–6. [195] K. Palaniyappan, Exploiting microorganisms for human needs, Indian Food Ind. 11 (1992) 25–7. [196] C. Hou and J.-F. Shaw (eds), Biocatalysis and Biotechnology for Functional Foods and Industrial Products, AOCS Press, Urbana, IL (2007). [197] J.P. Wynn and C. Ratledge, Oils from microorganisms, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 3 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 121–53. [198] C. Ratledge, Single cell oils – Have they a biotechnological future?, Trends Biotechnol. 11 (1993) 278–84. [199] C. Ratledge, Biotechnology of oils and fats, in Microbial Lipids (C. Ratledge and S.G. Wilkinson, eds), Academic Press, San Diego, CA (1989). [200] A. Azeem, Y.F. Neelagund and V. Rathod, Biotechnological production of oil: fatty acid composition of microbial oil, Plant Foods Hum. Nutr. 53 (1999) 381–6. [201] S. Joshi and J.M.S. Mathur, Biotechnological production of oils by the fungus Fusarium oxysporum, III: Effect of carbon source and content on chemical composition, Indian J. Microbiol. 25 (1985) 1–2. [202] J.-W. Liu, E.G. Bobik and Y.-S. Huang, In vitro hydrolysis of fungal oils: distribution of arachidonic acid-containing triacylglycerol molecular species, J. Am. Oil Chem. Soc. 75(4) (1998) 507–10. [203] C. Syldatk, M. Reuss, A. Daniel and R. Otto, Verfahren zur biotechnischen Herstellung von Fettsäuremethylestern (‘Biodiesel’) auf Molkebasis, Germ. Offenl. DE 19,838,011 A1 (20 May 1999). [204] L.Y. Zhu, M.H. Zong and H. Wu, Efficient lipid production with Trichosporon fermentans and its use for biodiesel production, Bioresour. Technol. 99 (2008) 7881–5. [205] C. Angerbauer, M. Siebendorfer, M. Mittelbach and G.M. Guebitz, Conversion of sewage sludge into lipids by Lipomyces starkeyi for biodiesel production, Bioresour. Technol. 99 (2008) 3051–6. [206] R. Hernandez and T. French, unpublished results (2008). [207] C. Ratledge and J.P. Wynn, The biochemistry and molecular biology of lipid accumulation in oleaginous microorganisms, Adv. Appl. Microbiol. 51 (2002) 1–51. [208] C. Ratledge and Z. Cohen, Microbial and algal lipids: do they have a future for biodiesel or as commodity oils?, Lipid Technol. 20 (2008) 155–60. [209] O.E. Ikwuagwa, I.C. Ononogbu and O.U. Njoku, Production of biodiesel using rubber [Hevea brasiliensis (Kunth. Muell.)] seed oil, Ind. Crops Prod. 12 (2000) 57–62.

220

Biodiesel science and technology

[210] A.S. Ramadhas, S. Jayaraj and C. Muraleedharan, Biodiesel production from high FFA rubber seed oil, Fuel 84 (2005) 335–40. [211] S.E. Knights, Crambe. A North Dakota Case Study, RIRDC Publ. No. WO2/005, Kingston (2002). [212] Y.P. Wang, J.S. Tang, C.Q. Chu and J. Tian, A preliminary study on the introduction and cultivation of Crambe abyssinica in China, an oil plant for industrial uses, Ind. Crops Prod. 12 (2000) 47–52. [213] J.M. Encinar, J.F. González, J.J. Rodríguez and A. Tejedor, Biodiesel fuels from vegetable oils: transesterification of Cynara cardunculus L. oils with ethanol, Energy Fuels 16 (2002) 443–50. [214] F. Avellaneda, J. Salvadó, J. Pasqualino and D. Navarlatz, In situ transesterification of Cynara cardunculus seeds to obtain biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [215] S.M.P. Meneghetti, M.R. Meneghetti, C.R. Wolf, E.C. Silva, G.E.S. Lima, M.A. Coimbra, J.I. Soletti and S.H.V. Carvalho, Ethanolysis of castor and cottonseed oil: a systematic study using chemical catalysts, J. Am. Oil Chem. Soc. 83 (2006) 819–22. [216] M.H. Chakrabarti and R. Ahmad, Transesterification studies on castor oil as a first step towards its use in biodiesel production, Pak. J. Bot. 40 (2008) 1153–7. [217] A.L. Pilgeram, D.C. Sands, D. Boss, N. Dale, D. Wichman, P. Lamb, C. Lu, R. Barrows, M. Kirkpatrick, B. Thompson and D.L. Johnson, Camelina sativa: a Montana omega-3 and fuel crop, in Issues in New Crops and New Uses (J. Janick and A. Whipkey, eds), ASHS Press, Alexandria, VA (2007), pp. 129–31. [218] K. Sawyer, Is there room for Camelina?, Biodiesel Mag. 5(7) (2008) 82–7. [219] A. Bernardo, R. Howard-Hildige, A. O’Connell, R. Nichol, J. Ryan and B. Rice, Camelina oil as a fuel for diesel transport engines, Ind. Crops Prod. 17 (2003) 191–7. [220] B. Rice, A. Frohlich and A. Leonard, Biodiesel Production from Camelina Oil, Waste Cooking Oil and Tallow, Crops Research Centre, Oak Park, Carlow (1998). [221] S.R. Schill, Oilseed comes of age, Biodiesel Mag. 5 (11) (2008) 44–9. [222] A. Büchsenschütz-Nothdurft, A. Schuster and W. Friedt, Breeding for modification fatty acid composition via experimental mutagenesis in Camelina sativa (L.) Crtz., Ind. Crops Prod. 7 (1998) 291–5. [223] P.S. Nagar, S. Desai, B. Patel and M. Daniel, Biodiesel from Aloe vera, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [224] P.N. Giannelos, F. Zannikos, S. Stournas, E. Lois and G. Anastopoulos, Tabacco seed oil as an alternative diesel fuel: physical and chemical properties, Ind. Crops Prod. 16 (2002) 1–9. [225] A. Srivastava and R. Prasad, Triglycerides-based diesel fuels, Renew. Sustain. En. Revs. 4 (2000) 111–33. [226] J.P. Kapur, S.D. Bhasin and K.C. Mathur, Oilseeds for food and industrial applications, Chem. Age India 33 (1982) 475–82. [227] Y.C. Bhatt, N.S. Murthy and R.K. Datta, Use of mahua oil (Madhuca indica) as a diesel fuel extender, IE (I) Journal-AG 85 (2004) 10–14. [228] S.V. Ghadge and H. Raheman, Process optimization for biodiesel production from mahua (Madhuca indica) oil using response surface methodology, Bioresour. Technol. 97 (2006) 379–84. [229] M. Sharma, R. Kumar, S.S. Ray, R. Sarin, R.K. Malhotra, R.P. Verma and N.R.

Feedstocks for biodiesel production

221

Raghunath, Process for producing biodiesel and the product thereof, US Pat. Appl. 2006/0094890 A1 (4 May 2006). [230] S. Puhan, N. Vedaraman, B.V.B. Ram, G. Sankarnarayanan and K. Jeychandran, Mahua oil (Madhuca indica oil seed) methyl ester as biodiesel – preparation and emission characteristics, Biomass Bioen. 28 (2004) 87–93. [231] S.V. Ghadge and H. Raheman, Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids, Biomass Bioen. 28 (2005) 601–5. [232] H. Raheman and A.G. Phadatare, Diesel engine emissions and performance from blends of karanja methyl ester and diesel, Biomass Bioen. 27 (2004) 393–7. [233] L.C. Meher, S. Naik and L.M. Das, Methanolysis of Pongamia pinnata (karanja) oil for production of biodiesel, J. Sci. Ind. Res. 63 (2004) 913–18. [234] S.K. Karmee and A. Chadha, Preparation of biodiesel from crude oil of Pongamia pinnata, Bioresour. Technol. 96 (2005) 1425–9. [235] G. Venturini Del Greco and L. Rademakers, The Jatropha Energy System: an integrated approach to decentralized and sustainable energy production at the village level, http://www.isf.lilik.it/files/jatropha/jes.pdf. [236] K.K. Meher, Biomethanation of jatropha de-oil seed cake, Presentation at Second Annual Monographic Conference on Jatropha curcas, Madrid (14–15 May 2008). [237] J. Fanning, The economic impact of Jatropha in rural communities and international trade, Presentation at Second Annual Monographic Conference on Jatropha curcas, Madrid (14–15 May 2008). [238] E. Voegele, The truth behind the claims, Biodiesel Mag. 5(11) (2008) 52–7. [239] H.P.S. Makkar, K. Becker, F. Sporer and M. Wink, Studies on nutritive potential and toxic constituents of different provenances of Jatropha curcas, J. Agric. Food Chem. 45 (1997) 3152–7. [240] N. Kumar and P.B. Sharma, Jatropha curcas – a sustainable source for production of biodiesel, J. Sci. Ind. Res. 64 (2005) 883–9. [241] K. Becker, Jatropha curcas: a potential source for tomorrow’s biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [242] K. Pramanik, Properties and use of Jatropha curcas oil and diesel fuel blends in compression ignition engine, Renew. En. 28 (2003) 239–48. [243] W. Thurmond, Feedstock trends: jatropha, Biofuels Int. 1(4) (2007) 62–3. [244] J. Parikh, Biodiesel development in India: appraisal and tasks, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [245] A. Mutsaars and H. Gosselink (Shell Global Solutions); confronta A. Duyndam, C2W 103 (17 March 2007), pp. 16–17 (in Dutch). [246] R. Lazos and E. García, Experiences in non-toxic Jatropha curcas production in State Michoacán, Mexico, Presentation at Second Annual Monographic Conference on Jatropha curcas, Madrid (14–15 May 2008). [246a] Pike Research LLC, Biofuels Markets and Technologies, Boulder, CO (2009). [247] M.J. Nye, T.W. Williamson, S. Deshpande, J.H. Schrader, W.H. Snively, T.P. Yunkewich and C.L. French, Conversion of used frying oil to diesel fuel by transesterification: preliminary tests, J. Am. Oil Chem. Soc. 60 (1983) 1598– 601. [248] M. Mittelbach and H. Enzelsberger, Transesterification of heated rapeseed oil for extending diesel fuel, J. Am. Oil Chem. Soc. 76(5) (1999) 545–50. [249] M.P. Dorado, E. Ballesteros, J.A. de Almeida, C. Schellert, H.P. Löhrlein and R. Krause, An alkali-catalyzed transesterification process for high free fatty acid waste oils, Trans. ASAE 45(3) (2002) 525–9.

222

Biodiesel science and technology

[250] M. Mittelbach, Erfahrungen mit Biodiesel aus gebrauchten Speiseölen in Österreich, in Biodiesel: Potenziale, Umweltwirkungen, Praxiserfahrungen (A. Munach and J. Krahl, eds); Proc. 2nd Intl. Conference, Bundesforschungsanstalt für Landwirtschaft, Braunschweig, (16–17 Sept. 2002), p. 47. [251] D.Y.C. Leung and G.Y. Chen, Biodiesel production using waste cooking oil from restaurants, in Proc. Symp. on Energy Engineering in the 21st Century, Hong Kong (9–13 Jan. 2000) (P. Cheng, ed.), Begell House Inc., New York, NY (2000), Vol. 4, pp. 1553–9. [252] M. Mittelbach and P. Tritthart, Diesel fuel derived from vegetable oil. III. Emission tests using methyl esters of used frying oil, J. Am. Oil Chem. Soc. 65 (1988) 1185–7. [253] T.A. Foglia, L.A. Nelson, R.O. Dunn and W.N. Marmer, Low-temperature properties of alkyl esters of tallow and grease, J. Am. Oil Chem. Soc. 74(8) (1997) 951–5. [254] A.A.A. Süß, Wiederverwertung von gebrauchten Speiseölen/-fetten im energetischtechnischen Bereich, Fortschr.-Ber. VDI. Reihe 15: Umwelttechnik, VDI Verlag, Düsseldorf (1999), Number 219. [255] W.H. Wu, T.A. Foglia, W.N. Marmer and J.G. Phillips, Optimizing production of ethyl esters of grease using 95% ethanol by response surface methodology, J. Am. Oil Chem. Soc. 76(4) (1999) 517–21. [256] R. Alcantara, J. Amores, L. Canoira, E. Fidalgo, M.J. Franco and A. Navarro, Catalytic production of biodiesel from soybean oil, used frying oil and tallow, Biomass Bioen. 18 (2000) 515–27. [257] M. Canakci and J. Van Gerpen, Biodiesel production from oils and fats with high free fatty acids, Trans. ASAE 44(6) (2001) 1429–36. [258] K. Hamasaki, H. Tajima, K. Takasaki, K. Satohira, M. Enomoto and H. Egawa, Utilization of waste vegetable oil methyl ester for diesel fuel, in State of Alternative Fuel Technologies 2001, SAE Spec. Publ. SP-1632 (2001), pp. 87–92. [259] A.-F. Hsu, K. Jones, W.N. Marmer and T.A. Foglia, Production of alkyl esters from tallow and grease using lipase immobilized in a phyllosilicate sol-gel, J. Am. Oil Chem. Soc. 78(6) (2001) 585–8. [260] Y. Watanabe, Y. Shimada, A. Sugihara and Y. Tominaga, Enzymatic conversion of waste edible oil to biodiesel fuel in a fixed-bed bioreactor, J. Am. Oil Chem. Soc. 78(7) (2001) 703–7. [261] M.I. Al-Widyan, G. Tashtoush, and M. Abu-Qudais, Utilization of ethyl ester of waste vegetable oils as fuel in diesel engines, Fuel Proc. Technol. 76 (2002) 91–103. [262] M.E. González-Gómez, R. Howard-Hildige, J.J. Leahy and B. Rice, Winterisation of waste cooking oil methyl ester to improve cold temperature fuel properties, Fuel 81 (2002) 33–9. [263] K.-T. Lee, T.A. Foglia and K.-S. Chang, Production of alkyl ester as biodiesel from fractionated lard and restaurant grease, J. Am. Oil Chem. Soc. 79(2) (2002) 191–5. [264] B. Supple, R. Howard-Hildige, E. González-Gómez and J.J. Leahy, The effect of steam treating waste cooking oil on the yield of methyl ester, J. Am. Oil Chem. Soc. 79(2) (2002) 175–8. [265] A.V. Tomasevic and S.S. Siler-Marinkovic, Methanolysis of used frying oil, Fuel Proc. Technol. 81 (2003) 1–6. [266] J. Cvengroš and Z. Cvengrošová, Used frying oils and fats and their utilization in

Feedstocks for biodiesel production

[267] [268]

[269] [270]

[271]

[272] [273] [274]

[275] [276]

[277] [278]

[279] [280] [281] [282] [283]

[ 284] [285] [286] [287]

223

the production of methyl esters of higher fatty acids, Biomass Bioen. 27 (2004) 173–81. R. Muskett and C.A. Anderson (to Biodiesel Australia), Method for production of alkyl esters, PCT Int. Publ. No. WO 2004/048311 (10 June 2004). J.M. Encinar, J.F. González and A. Rodríguez-Reinares, Biodiesel from used frying oil. Variables affecting the yields and characteristics of the biodiesel, I&EC Res. 44 (2005) 5491–9. M.G. Kulkarni and A.K. Dalai, Waste cooking oil – an economical source for biodiesel. A review, I&EC Res. 45 (2006) 2901–13. P. Felizardo, M.J. Correia, I. Raposo, J.F. Mendes, R. Berkemeier and J.M. Bordado, Production of biodiesel from waste frying oils, Waste Managm. 26 (2006) 487–94. E. Bockian Landsburg, W.W. Berry, E. Feldman, M.J. Haas, S. Kasprzyk, B. Ratigan, K.M. Scott and N. Adauwi, Production of biodiesel from trap grease, a plentiful and low-cost urban lipid source, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). M. Canakci, The potential of restaurant waste lipids as biodiesel feedstocks, Bioresour. Technol. 98 (2007) 183–90. S. Özgül-Yücel and S. Türkay, FA monoalkylesters from rice bran oil by in situ esterification, J. Am. Oil Chem. Soc. 80(1) (2003) 81–4. O. Rachmaniah, Y.-H. Ju, S.R. Vali, I. Tjondronegoro and A.S. Musfil, A study on acid-catalyzed transesterification of crude rice bran oil for biodiesel production, Paper presented at World Energy Congress, Sydney (2004). J.U. Obibuzor, R.D. Abigor and D.A. Okiy, Recovery of oil via acid-catalyzed transesterification, J. Am. Oil Chem. Soc. 80(1) (2003) 77–80. P.V. Lara and E.Y. Park, Potential application of waste activated bleaching earth on the production of fatty acid alkyl esters using Candida cylindracea lipase in organic solvent systems, Enzyme Microb. Technol. 34 (2004) 270–7. R.E. Babcock and B. Schulte, unpublished results (2008); see Biodiesel Mag. 5(2) (2008) 22. Levelton Engineering Ltd. and (S&T)2 Consulting Inc., Assessment of Biodiesel and Ethanol Diesel Blends. Greenhouse Gas Emissions, Exhaust Emissions, and Policy Issues, Rept. to Natural Resources Canada, Ottawa, ON (2002). Anon, Specifications for Commercial Grades of Tallows, Animal Fats and Greases, American Fats & Oils Association, Columbus, SC (2004). British Standard 3919, Specification for Technical Tallow and Animal Grease, BSI British Standards, London (1987). V.K. Tyagi and A.K. Vasishtha, Changes in the characteristics and composition of oils during deep-fat frying, J. Am. Oil Chem. Soc. 73 (1996) 499–506. M. Mittelbach, The high flexibility of small scale biodiesel plants, Proc. 2nd Eur. Motor Biofuels Forum, Graz (1996), pp. 183–7. S. Hayafuji, T. Shimidzu, S. Oh and H. Zaima (to Lonford Development Ltd.), Method and apparatus for producing diesel fuel oil from waste edible oil, US Pat 5,972,057 (26 Oct. 1999). R. Kotrba, The skinny on fats, Biodiesel Mag. 5 (11) (2008) 68–73. K. Bevill, A greasy alternative, Biodiesel Mag. 5(11) (2008) 76–81. M. Canakci and J. Van Gerpen, A pilot plant to produce biodiesel from high free fatty acid feedstocks, Trans. ASAE 46 (2003) 945–54. M.J. Haas, Animal fats, in Bailey’s Industrial Oil and Fat Products, 6th edn,

224

[288]

[289]

[290]

[291]

[292] [293] [294] [295] [296] [297]

[298]

[299]

[300] [301]

[302]

[303] [304]

[305]

Biodiesel science and technology Vol. 1 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, N.J. (2005), pp. 161–212. European Commission, Preliminary Report on Quantitative Risk Assessment on the Use of the Vertebral Column for the Production of Gelatine and Tallow, Submitted to the Scientific Steering Committee, Brussels (13–14 Apr. 2000). Department of Health and Human Service, US Food and Drug Administration, 21 CFR Part 589, Substances Prohibited from Use in Animal Food or Feed, US Fed. Regist. 62, 30935–78. World Health Organization, Report of a WHO Consultation on Medicinal and Other Products in Relation to Human and Animal Transmissible Spongiform Encephalopaties; Inform 12 (2001) 588. M. Mittelbach, B. Pokits, H. Müller, M. Müller and D. Riesner, Risk assessment for the biodiesel production from possibly BSE contaminated fat, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). F.D. Gunstone, What else besides commodity oils and fats?, Fett/Lipid 101 (1999) 124–31. L.A. Nelson, T.A. Foglia and W.N. Marmer, Lipase-catalyzed production of biodiesel, J. Am. Oil Chem. Soc. 73(9) (1996) 1191–5. D. Zheng and M.A. Hanna, Preparation and properties of methyl esters of beef tallow, Bioresour. Technol. 57 (1996) 137–42. M.A. Hanna and Y. Ali, Fuel properties of methyl esters of beef tallow, Recent Res. Dev. Oil Chem. 1 (1997) 309–20. J.H. Lee (to Rigel Technology Co.), One-stage process for feed and biodiesel and lubricant oil, US Pat. Appl. 2004/0022929 A1 (5 Feb. 2004). K. Rethmann (to Recyclat Tierischer Rohstoffe GmbH), Verfahren zur Herstellung von Biodiesel mit verbesserter Kältestabilität, Germ. Pat. DE 10,245,758 A1 (1 Oct. 2002). H. Kuramochi, K.-I. Choi, M. Osaka, K. Maeda, K. Nakamura and S.-I. Sakai, A new pretreatment method for biodiesel fuel production from trap grease, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). R. Nelson, Energetic and economic feasibility associated with the production, processing and conversion of beef tallow to a substitute diesel fuel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). G.G. Pearl, Animal fat potential for bioenergy use, Proc. Bioenergy 2002, 10th Biennial Bioenergy Conference, Boise, ID (22–26 Sept. 2002). C.L. Peterson, Potential production of biodiesel, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 231–8. M.J. Haas, K.M. Scott, P.J. Michalski and S. Runyon (to US Secretary of Agriculture), Lipid rich compositions, production of lipid rich compositions, production of fatty acid alkyl esters from heterogeneous lipid mixtures, PCT Int. Publ. No. WO 03/059847 A2 (24 July 2003). S. Ghosh, D.K. Bhattacharya and P. Dey, Acid oils as raw materials for biodiesel, J. Oil Technol. Assoc. India 30 (1998) 8–9. M.J. Haas, Improving the economics of biodiesel production through the use of low value lipids as feedstocks: vegetable oil soapstock, Fuel Proc. Technol. 86 (2005) 1087–96. R. Coll, S. Udas, and W.A. Jacoby, Conversion of the rosin acid fraction of crude tall oil into fuels and chemicals, Energy Fuels 15 (2001) 1166–72.

Feedstocks for biodiesel production

225

[306] A.M. Rojas, A.M. Schersl and M.A.F. Diaz, Process of refinement of crude tall oil using short path distillation, US Pat. Appl. 2005/0203279 (15 Sept. 2005). [307] A. Demirbaş, Fatty and resin acids recovered from spruce wood by supercritical acetone extraction, Holzforsch. 45 (1991) 337–9. [308] Y. Feng, Chemical composition of tall oil-based cetane enhancer for diesel fuels, Proc. First Biomass Conf. of the Americas: Energy, Environment, Agriculture, and Industry, Burlington, VT (30 Aug.–2 Sept. 1993), Vol. II, pp. 863–75.

6

Emerging new energy crops for biodiesel production

Abstract: Selection criteria for potential energy crops for biodiesel application include chemical structure and quality parameters of the oil and factors related to genotype, ecology, cultivation, maturation, oil extraction performance, etc., of the plant species. Target compositions should ensure desirable cold flow, ignition, oxidative stability and emission characteristics of biodiesel. The agronomic challenge is to create such affordable oils, preferably complying with food applications and creating value across the food and fuel chains. New feedstock opportunities vary significantly as to their potential impact in the market in terms of volume and timing to commercialisation. A limited number of developments will add to the global feedstock supply for biodiesel. Key words: Oilseed crop selection criteria, structure indexes, underexploited oilseed crops, agronomic challenges, potential feedstock developments.

6.1

Introduction

The fatty acid profile largely determines properties and uses of a vegetable oil (see Table 3.4). Optimum applicability requires tailored fatty acid profiles. High erucic acid contents are detrimental for food quality. On the other hand, oils with high oleic acid content, such as olive (64.6–84.4%), canola (60.0–75.0%) and NuSun (43.1–71.8%) oils [1], are highly valued for their nutritional qualities. Foodstuff oils are quite expensive. Rapeseed oil (B. napus) with its high content of oleic acid (60%), low saturated fatty acid (SFA) level (5.5%) and sufficiently low polyunsaturated fatty acid (PUFA) level (32.5%) is currently considered as the raw material of preference for biodiesel applications in terms of oxidative stability and combustion characteristics (see Fig. 14.6). New varieties are entering the market and may produce fatty acid methyl ester (FAME) with improved properties. Naturally, at present their availability is very low. Some alternative plant oils have already been tested for biodiesel application, notably physic nut (Jatropha curcas) oil (India, Nicaragua), coconut oil (Philippines), cottonseed oil (Greece), oils from sal (Shorea robusta), mahua (Madhuca indica), karanja (Pongamia pinnata) and neem (Azadirachta indica) in India. There are many more plants that naturally produce valuable and interesting compounds with potential industrial uses. The major families important as sources of oleaginous plants are Palmae, Compositeae, Euphorbiaceae, 226

Emerging new energy crops for biodiesel production

227

Linaceae, Papaveraceae, Sapindaceae, Simaroubaceae and Leguminoseae. As petrochemical supplies dwindle, prices rise, and the importance of seed oils as sources of industrial chemicals and fuels increases, it is of interest to examine potential energy crops, even though long-term developments might be needed. Screening analysis of common seed oils for biodiesel applications is a useful exercise, especially if we consider that transesterification does not alter the acid profile [2]. Consequently, selection criteria for biodiesel application may be based on original feedstock composition. Figure 6.1 shows the application of cluster analysis to the characterisation of edible oils by fatty acids. On this basis a subdivision may be made into groups constituted by cereals (rice, oats, rye, sesame, maize, barley, wheat and amaranth), oils characterised by high C18 : 2 content (cottonseed, soybean, sunflower, safflower, tobacco), oils with high C12 : 0 content (coconut and palm kernel) and oils with a high C18 : 1 content (groundnut, tonka, lupin, palm, olive, hazelnut) [3].

6.2

Crop selection criteria for biodiesel application

Although there is currently a lack of understanding of plant biochemistry and inadequate genomic and metabolic information about many crops, a number of new varieties of food crops have been tested for biodiesel application (see Table 5.7). In order to broaden the feedstock basis, suitable (edible and non-edible) oils need to be defined. Although no unique, ideal fatty acid profile for biodiesel application can be defined, some vegetable oils are more desirable than others, both in terms of composition and from the agronomic point of view. In fact, while chemical composition data are important in relation to biodiesel potential, other considerations are equally essential. There are a series of characteristics that a wild plant must have if it is to ever make the transit from a botanical curiosity into a viable crop at sustainable cost for biodiesel production. These include agricultural, industrial and marketing characteristics [4]. The US Department of Energy (DOE) has outlined 14 important criteria for introduction of a new crop into the US market as a source of biodiesel production (see Table 6.13). These include: ∑ ∑ ∑ ∑ ∑ ∑

genotype (seed yield, seed weight, oil content, oil/ha, oil properties) ecology (climatological tolerance for poor soil, drought and frost; seed deterioration time) cultivation (growth conditions, crop season, fertiliser need, ease of machine harvesting) biotic factors (resistance to pests and diseases) maturation (harvesting date, storage) oil extraction performance (temperature, time).

228 Biodiesel science and technology

350 300

Linkage distance

250 200 150 100

1st level 2nd level

50

Amaranth

Wheat

Barley

Maize

Sesame

Rye

Oats

Rice

Cottonseed

Soybean

Sunflower

Safflower

Tobacco

Coconut

Palm kernel

Groundnut

Tonka

Lupin

Palm

Olive

Hazelnut

0

6.1 Characterisation of edible oils by fatty acids. Results of applying cluster analysis with Manhattan distance and Ward’s linkage algorithm (after ref. [3]).

Emerging new energy crops for biodiesel production

229

Amongst these, genotype is most important for biodiesel production. Mustard meets all the criteria for a successful crop [5]. Important aspects of a field crop include crop physiology (crop development, growth and yield), agronomy, weeds and their control, diseases, insect pests, plant breeding, biotechnology and impact of production on the surrounding environment. Plant species need to be selected and identified capable of giving oil-bearing seeds to produce biodiesel, which can thrive on any type of soil, need minimum input and post-plantation management, and have low moisture demand. ‘Wet’ annual crops (e.g. rice) require irrigation. Cultivation of drought-tolerant perennial plants with the ability of using rainfall as the sole source of water and without the need for artificial support such as chemical fertilisers (e.g. Jatropha curcas) stabilise the environment and provide food (fruits, seeds and leaves), shade and other resources. A successful oilseed crop for biodiesel should be easy to propagate, precocious, rustic, productive, be easy to harvest, and fit into current farm practice. Getting both food and fuel from a single crop is equally most desirable. The crop should also have high supply potential and low oil costs. The oil content of potential energy crops needs to be quite high (about 25–30%). In this respect, it makes good sense to consider the prospects of biodiesel feedstocks based on the top ten oilseeds and on top oil yields/ha. Oil yield per acre depends on three factors: ∑

seed yield per acre (which is affected by harvest and transportation losses); ∑ oil content of the seed; and ∑ efficiency of the extraction method. Table 6.1, which shows plant species with the highest oil yields per acre, reflects that biomass productivity is highest in a tropical environment. Although oil yields will differ in different agroclimatic zones, it is noticed that some commodity crops for biodiesel (RSO, SBO, SNO) are not amongst the oil yield champions. Oil palm (E. guineensis) is the most productive oilseed crop but presents several problems concerning the properties of the correspondent biodiesel (see Section 5.4.4). The product must be easy to transport and store. In terms of utilisation, the main considerations are processing the seed and oil, seed chemistry and analysis, oil properties in human nutrition and industrial use (IV of sunflower oils, cold properties of palm oil, etc.), meal and by-product utilisation in animal nutrition. The product should be able to enter established markets at a competitive price or should be so attractive that a new market can be easily created. Also, new biodiesel oilseed feedstock requires a market for the postcrush meal. This presents a limitation for castor beans, jatropha, karanja, undi and other potential candidate feedstocks. Desirable crop technology change includes yield increases, more efficient harvest technology, and changes in tillage practice.

230

Table 6.1 Oilcrop productivities (adapted from ref. [6]) US Gal kg Oil/ha Plant Latin Name Oil/acre

US Gal Oil/acre

kg Oil/ha

Oil palm (dendê) Macaúba palm Pequi Buriti palm Oiticica Coconut Avocado Brazil nut Macadamian nut Physic nut Babassu palm Jojoba Pecan nut Bacuri Castor bean Gopher plant Piassava Olive tree Rapeseed Opium poppy Peanut Cocoa Sunflower Tung oil tree

610 461 383 335 307 276 270 245 230 194 188 186 183 146 145 137 136 124 122 119 109 105 98 96

85 81 80 72 71 60 59 55 55 54 49 49 47 46 37 33 31 28 26 24 23 22 18 18

696 665 653 589 585 490 481 450 449 440 405 402 386 374 304 273 256 230 217 195 189 183 148 143

Elaeis guineensis Acrocomia sclerocarpa Caryocar brasiliensis Mauritia flexuosa Licania rigida Cocos nucifera Persea americana Bertholletia excelsa Macadamia terniflora Jatropha curcas Orbignya martiana Simmondsia chinensis Carya illinoensis Platonia insignis Ricinus communis Euphorbia lathyris Attalea funifera Olea europaea Brassica napus Papaver somniferum Arachis hypogaea Theobroma cacao Helianthus annuus Aleurites fordii

5000 3775 3142 2743 2520 2260 2217 2010 1887 1588 1541 1528 1505 1197 1188 1119 1112 1019 999 978 887 863 801 790

Rice Buffalo gourd Safflower Crambe Sesame Camelina Mustard Coriander Pumpkin seed Euphorbia Hazelnut Linseed Coffee Soybean Hemp Cotton Calendula Kenaf Rubber seed Lupin Palm Oat Cashew nut Corn (Maize)

Figures are international averages. Harvests vary with region and sub-species.

Oriza sativa Cucurbita foetidissima Carthamus tinctorius Crambe abyssinica Sesamum indicum Camelina sativa Brassica alba Coriandrum sativum Cucurbita pepo Euphorbia lagascae Corylus avellana Linum usitatissimum Coffea arabica Glycine max Cannabis sativa Gossypium hirsutum Calendula officinalis Hibiscus cannabinus Hevea brasiliensis Lupinus albus Erythea salvadorensis Avena sativa Anacardium occidentale Zea mays

Biodiesel science and technology

Plant Latin Name

Emerging new energy crops for biodiesel production

231

In fact, the DOE criteria mentioned above also ignore some important criteria related to the biodiesel production process as well as fuel-inherent properties. For example, when solubility of glycerol in the vegetable oil is very high, phase separation is very difficult. This important technical limitation needs to be overcome in order to produce biodiesel.

6.3

Structure and quality parameters for evaluating alternative feedstocks

Screening additional and alternative feedstocks for biodiesel application needs to consider various chemical and physical restrictions (e.g. stability of oil, winter operability and Conradson carbon residue). Analytical methods in fatty acid (FA) chemistry are categorised in terms of structure and quality parameters. Common structure indexes such as iodine value (IV), cetane number (CN), oil stability index (OSI), saponification value (SV) or saponification number (SN), and hydroxyl value (HV), are widely used despite the fact that modern analytical methods yield more reliable information. Quality parameters describe components in oils and fats arising from processing, storage and naturally occurring, non-fatty materials (see Chapter 12). Quality indexes are the free fatty acid (FFA), peroxide, anisidine, phosphorus, and other similar values. Quality indexes were formerly termed processing-related parameters. In order to produce a biodiesel with optimised properties, the following fatty acid profiles are desirable: ∑

lowest possible SFA levels (such as C16 : 0 and C18 : 0) for improved winter operability; ∑ highest possible MUFA levels (such as C18 : 1) for good stability and winter operability; and ∑ lowest possible PUFA levels (such as C18 : 3) for increased oxidation stability. Such energy crops are already available (high-oleic rapeseed and sunflower, low-linolenic rapeseed), see Table 5.12, and represent interesting but limited foodstock sources for biodiesel. Potential crop selection criteria may be based on the limits set in international biodiesel standards (e.g. EN 14214 and ASTM D 6751) for various parameters such as iodine value (IV), cetane number (CN), concentration of linolenic acid and polyunsaturated (≥ 4 double bonds) acids, chain length, distillation temperature, etc. Of course, if one considers the possibility to produce FAME by blending of different raw materials then a suitable single feedstock is not obliged to meet any such standards. Starting from the fatty acid composition, SN, IV and CN of FAMEs can be calculated, as follows [7, 8]:

SN = ∑(560 ¥ Ai)/MWi

6.1

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IV = ∑(254 ¥ D ¥ Ai)/MWi

6.2

where Ai is the percentage, D is the number of double bonds and MWi is the molecular mass of each component.

CN = 46.3 + 5458/SN – 0.225 ¥ IV

6.3

This equation expresses the high correlation between iodine value and cetane number.

6.3.1 Iodine value The iodine value, expressed as grams of I2 absorbed/100 g sample under standard conditions, is a measure of the unsaturation of oils and fats and their fatty acid derivatives, and can be determined in many different ways. IV is used for the determination of the quality of diesel fuel derived from vegetable oils [9]. Several alternative calculation procedures to determine IV of oils directly from their FAME composition have been proposed [10, 11], including the American Oil Chemists’ Society (AOCS) method Cd 1d92 [10]. According to EN 14214 (Annex B) for determination of the iodine number the mass percentage of the fatty acid methyl esters is multiplied by an assigned weighting factor. Table 6.2 shows the iodine value for a typical rapeseed oil calculated according to this procedure. Whereas the fatty acid molecular weights do affect the determination of IV, the relative amounts of the different acids and their number of double bonds are more crucial for the determination of IV. The iodine value therefore depends mainly on the percentage concentration of unsaturated fatty acid components and the number of double bond(s) D present in the structure. Determination of iodine value gives a reasonable quantification of unsaturation if the double bonds are not conjugated with each other or with carbonyl oxygen [12]. Theoretical iodine values calculated from the total number of double bonds using the fatty acid composition tend to be slightly higher (5–10%) than the iodine values determined by titration, due to the presence of unsaponifiables in the Table 6.2 Calculation of iodine value (IV) of a typical biodiesel samplea (after ref. [13]) Component

wt%

Factor iodine valuea

C16 : 1 C18 : 1 C18 : 2 C18 : 3 C20 : 1 C22 : 1

0.20 64.1 18.7 7.55 1.32 0.40

0.95 0.86 1.732 2.616 0.785 0.723

Calculated IV a





In accordance with DIN EN 14214 Annex B.

g I2/100 g 0.2 55.1 32.4 19.8 1.0 0.3 108.8

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233

crude oils. Biodiesel fuels with low iodine values show lower NOx emission (see Section 14.4.3). The iodine value stands in some relation to oxidative stability and reflects both the propensity of an oil or fat to oxidise and to polymerise and form engine deposits. However, many fatty acid profiles and different fatty acid structures can yield the same IV [14]. Also, no relation between IV and oxidative stability was observed in an investigation of biodiesel with a wide IV range [15]. Moreover, as engine performance tests with a mixture of vegetable oils of different IV did not yield results that would have justified a low IV [16], it is not entirely suprising that IV is not included in all national biodiesel standards (e.g. in the US and Australia). As the (old-fashioned) IV index does not take into account the positions of the double bonds, it is considered an unsatisfactory structure index and not necessarily the best indicator of a fuel’s oxidation stability. Several new structural indexes have been proposed which are probably more suitable than IV. In particular, the alternative parameters allylic position equivalent (APE) and bis-allylic position equivalent (BAPE) better relate structure and amount of common component fatty acids in vegetable oils (VOs) to observed properties [14]. The APE and BAPE indexes are based on the number of reactive positions in oxidation. To an extent, unsaturated fatty acid components are required as it restricts FAMEs from solidification. On the other hand, high unsaturation values are undesirable for biodiesel in view of peroxidation, cross-linking and polymerisation. Reported average IV values range from 200+ (LSO, highly unsaturated) to about 10–20 g I2/hg (CNO and PKO, highly saturated). EN 14214 sets a maximum IV of 120 g I2/hg (formerly 115 g I2/hg). In this respect, SNO with high PUFA levels registers higher IV than some other raw materials (e.g. RSO) with a lower content of unsaturated fatty acids. Consequently, sunflower oil (IV > 120 g I2/hg) does not meet EU and German specifications. The iodine value specified in the EU actually reflects RSO; the absence of an iodine specification value in the American ASTM D 675108 standard allows for the use of SBO in the US, which features a similar unsaturation level as SNO. Soy-oil may be used as a multi-feedstock blending component to comply with European standards. The EU biodiesel standard needs to be amended in relation to the iodine value in order to allow for raw materials other than rapeseed. For potential energy crop selection, the IV criterion is only applicable in connection to the EN 14214 standard, as IV is not included in the US biodiesel standard.

6.3.2 Saponification number The saponification value or number (SV or SN) pertains to all fatty acids present in the sample (free and esterified) and is usually determined according

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Biodiesel science and technology

to ref. [17] or AOCS Official Methods Cd 3c-91 and Cd 3b-76. To determine SV, the sample is completely saponified with an excess of alkali, which excess is then determined by titration (in mg KOH/g) (see Table 6.3). The saponification number depends on the molecular weight and the percentage concentration of fatty acid components present in FAMEs of oil. The SV is effectively used to determine the average relative molecular mass of oils and fats. Lauric oils, with a higher percentage of ester bonds than longer chain oils, have a higher SV (240–250 mg KOH/g for CNO compared to 190–195 mg KOH/g for SBO). The distinction is quite relevant for biodiesel production in that oils with a high SV require more methanol, and produce more glycerol but less biodiesel than longer chain oils. Oils with high SN impart high foamability (e.g. palm kernel, coconut and babassu oils).

6.3.3 Cetane number The cetane number (similar to the octane number for gasoline) is a widely used dimensionless prime diesel fuel quality index related to the ignition delay (ID) time (and combustion quality) of a fuel upon injection into the combustion chamber. A cetane number is determined by a complex and expensive engine test (ASTM D 613 and ISO 5165) using two reference fuel blends with known cetane number. The cetane scale (100 for hexadecane – also known as cetane – and 15 for 2,2,4,4,6,8,8-heptamethylnonane or HMN, both C16H34 compounds) is arbitrary. The CN of the test fuel is the percentage in volume of cetane in a blend of n-cetane (100 CN) and heptamethylnonane (15 CN) having the same ignition quality when tested in the same engine under the Table 6.3 Saponification number of vegetable oils (mg KOH/g) (after ref. [18]) Oil

SN

Oil

SN

Babassu Camelina Canola Cardoon Cashew nut Castor Coconut Corn Cottonseed Indian mustard Jatropha Jojoba Karanja Linseed Mahua Microalgal

241–253 185–194 170–190 194 168 176–187 242–263 187–196 190–207 171 188–198 92–95 189 180–196 187–197 189

Mustard Nahor Olive Palm Palm kernel Peanut Poppy seed Rapeseed Rubber seed Safflower Sesame Soybean Sulfur olive Sunflower Tigernut

170–178 191 187–196 200–205 240–257 184–196 189–197 166–198 186–198 186–203 188–193 189–195 193 186–194 190–194

Emerging new energy crops for biodiesel production

235

same test conditions. Cetane numbers determined using a constant-volume combustion apparatus (CVCA) [19, 20] are measured more rapidly, with greater experimental ease, better reproducibility and reduced use of fuel than according to ASTM Method D 613. The Ignition Quality Tester™ (IQT™) [21] is a further, automated development of CVCA. The cetane number can also be estimated from TGA data, using ASTM D 976. For portable cetane number analyser methods, see Section 12.5.2. Although the cetane number is a measure of ignition quality of petroleum fuels, the significance of this value for vegetable oils has not been established [22]. Generally, fatty acids have CN values above that of conventional diesel fuel (petrodiesel). The standard ASTM D 975 for conventional DF requires a minimum CN of 40 while the standards for biodiesel prescribe a minimum of 47 (ASTM D 6751) or 51 (EN 14214). A higher cetane number indicates shorter ignition time delay characteristics. However, with increase of CN, IV (or the degree of unsaturation) decreases (see Eqn 6.3). As this might eventually lead to solidification of FAMEs the upper limit of CN is 65 (ASTM PS 121-99). The cetane number is most strongly affected by the saturation level of the fatty acids but other properties equally play a role. Generally, CN, heat of combustion, melting point, and viscosity of neat fatty compounds increase with increasing chain length (i.e. uninterrupted CH2 moieties) and decrease with increasing unsaturation (see Table 6.4). Saturated fatty acids have a positive effect on cetane number and oxidation stability (as for CNO, PKO, TLW and UCO). High CNs are observed for esters of saturated fatty acids, such as palmitic (C16 : 0) and stearic (C18 : 0) acids. Besides increasing number of double bonds (and their position in the chain), which cause lower CNs, branching in the chain also lowers CN. As shown in Table 6.5, the cetane number of biodiesel is not only dependent on the nature of the fatty acid but also on the ester component. Also Ali et al. [23] reported that the CN Table 6.4 Cetane number and standard deviation (in parentheses) of fatty esters determined with an Ignition Quality TesterTM (after ref. [21]) Ester Methyl Ethyl Propyl Butyl iso-Propyl iso-Butyl 2-Butyl 2-Ethylhexyl

Acid Palmitic

Stearic

Oleic

Linoleic

85.9 93.1 85.0 91.9 82.6 83.6 84.8 98.2

101.0 97.7 90.9 92.5 96.5 99.3 97.5 115.5

59.3 67.8 58.8 61.6 86.6 59.6 71.9 88.2

38.2 39.6 44.0 53.5 nd nd nd nd

nd = not determined.

(2.34) (3.09) (2.29) (4.44) (1.87) (2.41) (1.96) (6.49)

(3.35) (3.30) (2.72) (3.03) (3.52) (3.20) (5.59) (3.26)

(1.30) (1.72) (1.18) (1.36) (3.55) (1.56) (1.75) (4.83)

(0.85) (0.89) (1.19) (2.95)

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Biodiesel science and technology

of oils and fats increases with esterification. Table 6.4 shows that the CNs of fatty compounds are not negatively affected by branching in the alcohol moiety. Equation 6.3 may be used to predict the cetane number of FAMEs of unusual oils, at least in case of correspondence of calculated and experimental IV values. Other expressions for the calculated cetane number based on fuel properties and oil chemistry are in common use, such as

CN = 18.53 + 1.371 WACL – 1.738 WADB2

6.4

where WACL = weighted average number of carbon atoms in the fatty acid chains and WADB = weighted average number of double bonds in fatty acids [24]. For conventional diesel fuel, higher CNs have been correlated with reduced NOx exhaust emissions [25]. Despite the inherently relatively high CNs of fatty compounds, NOx exhaust emissions usually increase slightly when operating a diesel engine on biodiesel. CN of biodiesel fuels may be improved by cetane improvers [26]. The complex matter of cetane numbers and cetane number testing of biodiesel is described elsewhere in more detail [27, 28]. The iodine value, a measure of unsaturation, was used in cetane number correlation by Krisnangkura [8]. Equation 6.3 indicates that each unit of IV lowers CN by 0.225. Nevertheless, this does not explain the observed large variations in reported CNs for samples of biodiesel from the same feedstock oil. Clearly, other factors play a role. In fact, reported CN values for different types of biodiesel vary considerably, and beyond experimental error according to the standard ASTM D 613 engine test, namely SBME, 45.0–67.0; SBEE, 48.2–52.7; and RME, 48.0–65.0 [28]. The observed spread in CN values can be explained by: geographical and seasonal effects, considerable uncertainties in engine test values, oxidation and precombustion effects. Some of the CN variation may be attributed to variations in feedstock, as differences in climatic conditions can cause fatty acid composition changes in vegetable Table 6.5 Cetane number and energy content of biodiesel fuels (after ref. [29]) Type of biodiesel

Heat of combustion (MJ/kg)

CN

Methyl soybean Ethyl soybean Butyl soybean Methyl sunflower Methyl peanut Methyl rapeseed Ethyl rapeseed

39.8 40.0 40.7 39.8 39.9 40.1 41.4

46.2 48.2 51.7 47.0 54.0 47.9–56.0 64.9–67.4

Emerging new energy crops for biodiesel production

237

oils. Also the effects and use of oil processing technology need to be considered. Changing the oxidation level of biodiesel has an impact on CN since peroxide compounds are well known to act as cetane improvers [30]. The influence of various oxygenated compounds on the cetane numbers of fatty acids and esters was investigated by Knothe et al. [31]. Hydroperoxides formed during oxidation of fatty acid esters are held responsible for the CN enhancement [28]. The extent of oxidation can be characterised by the peroxide value (PV). Four analytical methods for the determination of PV in SBO were compared [32]. Figure 6.2 exemplifies the influence of increasing peroxide value on CN value for the case of methyl soyate. Knothe et al. [33] have forwarded a possible explanation for differing and comparatively low cetane values of unsaturated esters, namely the effect of compounds formed in the phase of fuel injection into the combustion chamber prior to ignition (precombustion).

6.3.4 Oxidation stability Stability depends on the fatty acid profile, presence of naturally occurring stabilisers (tocopherols) and metal contaminants. Oxidation leads to formation 55.0

52.5

Cetane number

50.0

47.5

45.0 y = 6E–6x3 – 0.0017x2 + 0.1857x + 46.17 R2 = 0.8446 42.5

40.0 0

20

40 60 80 Peroxide value (meq/kg)

100

120

6.2 The effect of peroxide value on cetane number of methyl soyate. (after ref. [28]).

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Biodiesel science and technology

of volatile small-chain fatty acids, which can cause damage through corrosion to the engine. At the same time, polymers are formed, which precipitate as ‘gums’ and which may lead to deposits and residues in the engine. Such damage can be avoided by stabilisation with antioxidants. Oxidation stability covers both storage and thermal stability. The oxidation stability of biodiesel varies significantly depending on the source of oil/fat from which the biodiesel is derived, processing conditions, contaminants (particularly trace metals, water, radicals and peroxides) and storage conditions. Oxidation processes begin immediately after production. Storage stability can be influenced by, e.g., humidity, sunlight, microorganisms, temperature and oxygen. Thermal stability additionally generates gum and solid deposits. Group IV transition metals (Zn, Cu, Ni, Co, Fe, Cr, Mn, V) in various concentrations (0.02–100 ppm) reduce the oxidation stability induction period of B20 and B100 [34]. Biodiesel is often blended with ultra-low sulphur diesel (ULSD), which may contain these transition metals. Less than 1 ppm of metals such as copper and iron is sufficient to have a significant effect on stability. Such low levels of metal contamination are difficult to control through the biodiesel supply chain. In particular, biodiesel based on yellow grease (used vegetable oil) already contains metal contaminants. Biodiesel oxidation is a very complex process. Not surprisingly, different test methods are used to get a global view of the oxidative stability of an oil-derived product, such as the Schal oven test, oxygen bomb, pressurised differential scanning calorimetry (PDSC) and Oil Stability Index (OSI). The oxidative stability index, which determines the oxidative stability of an oil by passing air through a sample under stringent temperature control, is an accepted method for evaluating the stability of vegetable oils [35]. Other analytical techniques and determinations, such as UV absorbance photochemi luminescence, yellowness index (YI), wet chemical methods (acid value, peroxide value), gel permeation chromatography (GPC) and gas chromatography-mass/spectrometry (GC-MS), provide additional insight to the oxidative process. The method for assessing oxidative stability included in the European biodiesel standards EN 14213 and EN 14214 utilises a Rancimat apparatus; the method is very similar to the OSI method [36]. See Section 12.5.3. Factors influencing the OSI time of lipids are the inherent antioxidant content, degree of polyunsaturation and the presence of D5 double bond chemical entities [37]. Natural antioxidants increase the oxidative stability of biodiesel. The content of the natural antioxidant Vitamin E in freshly produced rape biodiesel (Rancimat value of 7 h) is most insufficient to ensure that the oxidation stability level specified in the EU standard (6 h) can be maintained at the filling station for much longer than 5 days, which often means before delivery to the end-user. Refined vegetable oils with reduced

Emerging new energy crops for biodiesel production

239

Table 6.6 OSI values of vegetable oils (after ref. [38]) Vegetable oil

OSI at 383 K

Crude meadowfoam oil (CMFO) Refined meadowfoam oil (RMFO) Cold pressed jojoba oil (PJO) Refined high oleic sunflower oil (HOSNO) Refined castor oil (RCAS) Crude jojoba oil (CJO) Refined jojoba oil (RJO) Deodorised jojoba oil (DJO) Refined soybean oil (RSBO) Reagent grade triolein High erucic acid rapeseed oil (HERO) Triolein 99+% Triolein 95%

246.9 67.3 55.9 49.8 56.1 34.5 31.4 23.5 19.9 8.5 8.1 2.7 1.8

tocopherol content result in lower oxidative stability (see Table 6.6). Linear relationships of the ratio of total tocopherol/iodine value vs. OSI time at 383 K are generally reported [35, 39]. In terms of oxidation stability, oils are frequently divided into three classes: (a) SBO and classic SNO with low oxidative stability; (b) high-oleic oils with very good stability, which is related to their oleic acid content; and (c) high-erucic oils with an oxidative stability a little lower than class (b). OSI values of various vegetable oils determined at 383 K were compared (Table 6.6) [35]; minimum EN 14214 requirement is 6 h. Meadowfoam oil (Limnantes alba) is the most stable oil with an OSI time of 67.3 h for refined oil and 246.9 h for crude oil. Other oils with good oxidative stabilities are refined high-oleic sunflower oil (HOSNO) and crude jojoba oil (CJO) with OSI times of 49.8 and 34.5 h, respectively. Several new crop oils such as jojoba have superior oxidative stability compared to traditional vegetable oils. A large degree of polyunsaturates (e.g. in SBO) significantly diminishes the stability. For US producers who export soy-based biodiesel to European customers, storage stability is a major concern. Autoxidation of unsaturated fatty compounds proceeds at different rates depending on the number and position of double bonds [40]. A study of oxidative stability with respect to olefinic position of monoenoic fatty methyl esters shows that the D5 double bond is the most stable by more than an order of magnitude as compared to D6, D9 and D13 fatty acids. Meadowfoam oil is unique in that the triacylglycerol mixture consists of > 95% of fatty acids with carbon chain lengths greater than 18. The high contribution of cis D5 fatty acids (ª 66%) determines an

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exceptionally high OSI value [35]. The positions allylic to double bonds are especially susceptible to oxidation. Bis-allylic positions in polyunsaturated fatty acids (at C11 in linoleic acid and at C11 and C14 in linolenic acid) are even more prone to autoxidation than allylic positions. Relative rates of oxidation are: oleates : linoleates : linolenates = 1 : 41 : 98 [40]. Chu and Kung [41] have related the effect of fatty acid composition (FAC) on the oxidative stability of vegetable oils (oil stability index OSI according to AOCS method Cd 12b-92), as follows:

OSI(h) = 7.5123 + %C16 : 0 ¥ (0.2733) + %C18 : 0 ¥ (0.0797)



+ %C18 : 1 ¥ (0.0159) + %C18 : 2 ¥ (–0.1141)



+ %C18 : 3 ¥ (–0.3962), R2 = 0.911

6.5

The order of positive influence of fatty acid on OSI was palmitic acid, followed by stearic and oleic acid. The most negative influence on OSI for unsaturated fatty acids is linolenic acid, followed by linoleic and oleic acid. OSI is inversely related to PUFA content (see Table 5.1), as shown, e.g., for SBO (63%) and corn oil (59%) with low OSI, and for peanut (30%), high-oleic safflower (15%) and olive oils (15%) with high OSI. Equation 6.5 explains the observed order of oxidative stability of various biodiesel feedstocks, namely tallow (beef) > palm > chicken fat > rapeseed > jatropha > cottonseed > soybean. An inherent oxidation stability is important for longer oil life, improved filter life and lower maintenance costs. The issue of oxidative stability affects biodiesel primarily during extended storage. Vegetable oils such as SBO and SNO with elevated levels of linoleic (and consequently a high iodine number) may impair the oxidation stability of biodiesel fuels. In order to avoid oxidation, special precautions are advised during storage of biodiesel from VOs with high PUFA contents, which are rather unstable. Canola oil with fairly low contents of double or triple unsaturated fatty acids (high oleic varieties) is less likely to be unstable (autoxidise) in the presence of air during long storage. As a result of the increased tendency to oxidation, higher amounts of PUFAs also reduce colour stability of the product. Use of RSO, as compared to other feedstocks such as SBO and SNO, has the advantage of higher MUFA content (62%) and lower levels of PUFA and saturates, which makes it easier to process and gives a more stable fuel with better low-temperature properties. CNO has the lowest percentage of unsaturated fatty acids (oleic, linoleic and linolenic). Because of this low unsaturation, it is resistant to oxidative rancidity and hence, CNO-containing products have a long shelf-life. Oxidative stability of polyunsaturated fatty acids also needs to take into account the degree of conjugation. This is not adequately expressed by Eqn 6.5. Figure 6.3 shows that a-eleostearic acid (in tung oil) with conjugated double bond systems (C18 : 3c) degrades more rapidly than the corresponding

Emerging new energy crops for biodiesel production

241

12 18 : 3 18 : 3c

Relative peak area

10

18 : 3ci

8

6

4

2

0 0

10

20

30 40 50 Time (hours)

60

70

80

6.3 Change in relative peak areas of linolenic acid (C18:3) in linseed oil, and a-eleostearic acid (C18:3c) and isomeric eleostearic acid (C18:3ci) in tung oil, as a function of exposure time to UV light. The peak heights are related to that of stearic acid in the respective oil. (after ref. [42]).

linolenic acid (in linseed oil), with isolated double bonds (C18 : 3). Several studies deal with the photochemical and thermal ageing behaviour of drying oils [42–46]. Processes taking place here at the expense of the highly unsaturated, conjugated and non-conjugated fatty acids comprise polymerisation of the fatty acid chains, resulting in a 3D network and solidification of the oil, and oxidative degradation at the double bonds to the methyl esters of shorter-chain dicarboxylic acids, octanedioic and nonanedioic acid. In fact, the degradation of tung oil follows a different reaction scheme compared with linseed oil as the process is accompanied by isomerisation of a-eleostearic acid to b-eleostearic acid (trans, trans, trans-9,11,13-octadecatrienoic acid). Also isomerisation of other conjugated octadecatrienoic acids of a different oil, Momordica balsamina (balsam apple) oil, has been reported [47]. It would appear that composition and properties of the drying oils are not exactly ideal for a biodiesel raw material, which is at variance to suggestions of their potential use made elsewhere [48–50]. Biodiesel stabilisation can be affected by feedstock source, manufacturing process, metal contamination and ageing through storage and shipment. For biodiesel storage conditions, see Section 14.4.2. Synthetic antioxidants (AOs) may be added to biodiesel to prevent premature oxidation of unsaturated

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fatty acid esters. Early use of antioxidants is imperative to preserve quality. When choosing a stabiliser many factors need to be considered, in particular robustness, acceptance, handling and cost [51]. Baynox® (Lanxess) synthetic antioxidants have been developed for biodiesel based on RSO, PMO, UCO and TLW [52]; Baynox® Plus is recommended for more easily perishable (unsaturated) oils such as SBO, SNO and the non-edible oil from the Jatropha nut. Other stabilisers developed to meet the ASTM D 6571 and EN 14214 standards for oxidative stability of biodiesel are Irgastab® BD10 (Ciba), Ethanox 4760E (Albemarle Corp.), BioSINEOXTM 100 (AAFC), AdestaTM (Novus Intl., Inc.) and Eastman’s BioExtend 30 and 30HP antioxidants. Ethanox 4760E (blend of synergistic AOs plus metal chelator) shows a very powerful response in yellow grease and poultry fat [53]. International Fuel Technology Inc. (IFT)’s DieseLift BD-3 oxidation stability additive, which has been tested for various feedstocks, including camelina, soybeans and a camelina/coconut blend, improves the biodiesel oxidation stability by 2–10 times. Other biodiesel stabilisers have been developed by Kemin Industries Inc. (Des Moines, IA) and Primrose Oil Company (Dallas, TX). For oxidative stability testing, see Section 12.5.3.

6.3.5 Additional screening parameters The acid value (AV) is a measure of the free fatty acid level and is determined by titrating FFA (e.g. according to ASTM 664, ASTM 974 or AOCS Official Method Cd 3d-63). For feedstocks with a very high acid number (e.g. palm oil, waste oils) acid-catalysed pre-esterification of the free fatty acids is commonly applied using mineral acids, sulphonic acids or cationexchange resins [54]. The maximum acid value of biodiesel (‘mg’ of KOH necessary to neutralise the free fatty acids in 1 g of sample) is specified in the international biodiesel standards as 0.50 mg KOH/g, corresponding to an FFA content of 0.25 wt%, if expressed as oleic acid. The difference between saponification value and acid value (SV–AV) is referred to as the ester value (EV, mg KOH/g) and is indicative of the number of ester bonds in the sample. The hydroxyl value (HV, mg KOH/g) was originally used to determine the hydroxyl acid content, but in oils without such acids it can be used to determine the partial glyceride content. Determination is according to AOCS Official Method Cd 13–60. Chain length is another selection criterion and should be comprised between C12-C22 FAMEs (according to ASTM PS 121–99). Nevertheless, both coconut oil and palm kernel oils with short-chain fatty acids find (limited) application as biodiesel. Long-chain saturated fatty acid methyl esters increase the viscosity and display particularly unfavourable coldtemperature behaviour whereas fatty acids with two or more double bonds

Emerging new energy crops for biodiesel production

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show excellent cold-flow properties. This means that high IV results in favourable winter performance. In addition to ignition quality as expressed by the cetane scale, several other properties are important for determining the suitability of biodiesel as a fuel (see Section 14.4). Heat of combustion, pour point, cloud point, (kinematic) viscosity, oxidative stability, and lubricity are among the most important of these properties. There exists no direct correlation between FAME chain length and lubricity enhancing properties [55]. As unsaturation increases, lubricity enhancement increases. High melting points, cloud points and cold filter plugging points (CFPP) may denote that FAME is not suitable for use as biodiesel in cold weather conditions. CFPPs in hot climates are less important. Branched esters improve low-temperature properties. High saturate levels in biodiesel (e.g. 47.0% in PMO, and beyond for CNO and PKO) increase its cloud point and, while this is not a problem in warmer climates, it is unacceptable in colder winter climates. On the other hand, oils with a high proportion of PUFAs are stable in cold weather but vulnerable to oxidation (e.g. FOs). The 90–95% boiling point limit of 633 K (ASTM D 6751) is most difficult to respect for compositions with very long fatty acids (e.g. Ximenia americana, 29.8% C26). Acceptable biodiesel must meet various criteria relating to the extent of total unsaturation of the oil. The European Standard EN 14214 regulates the maximum content of linolenic acid methyl ester in biodiesel for vehicle use to 12 wt% and polyunsaturated fatty acid methyl esters (i.e. compounds with four or more double bonds, D ≥ 4) to 1 mol%. These limits are not undisputed. The existing Italian standards for composition and properties (UNI 10946) allow the use of biodiesel with C18 : 3 > 12% only for heating plants. Since quite a high C18 : 3 level improves the cold-flow behaviour of biodiesel, the use of B. carinata oil for automotive traction appears interesting provided that it is suitably blended with oils having lower linolenic acid levels in order to meet the specifications. Similarly, conventional LSO (60.4% C18 : 3) may be used as biodiesel in RSO blends. Without blending, EN 14214 rules out the use of various non-edible seed oils from plants on the Indian subcontinent with exceedingly high C18 : 3 contents, such as Aleurites moluccana (28.5%), Aphanamixis polystachya (13.6%), Cannabis sativa (22.4%), Euphorbia helioscopia (42.7%), Mappia foetida (36.8%), Perilla frutescens (36.2%), Saturega hortensis (62.0%) and Swietenia mahagonia (16.1%) [56–58], but also of the euphorb Mecurialis annua (70%), the Southeast Asian perah (Elateriospermum tapos) (17.2%) [59], and of highly unsaturated fish oils (see Table 5.17; 20–32% D ≥ 4). Other seed oils containing exceedingly high linolenic acid contents are blackcurrant (14–19%), gooseberry (19–20%) and redcurrant (29–31%) [60]. Although tung oil qualifies for EN 14214 as to the low linolenic acid content (1–3 wt%), which is quite opposed to

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conventional linseed oil (50–60 wt%), its exceedingly high C18 : 3c contents (77–86 wt% of a-eleostearic acid) determines a poor product shelf-life. It would appear more reasonable to set a total C18 : 3 limit for biodiesel rather than a linolenic acid limit. It should be pointed out also that the linolenic acid criterion for selection of an oleaginous crop as a potential biodiesel feedstock should be relaxed when blending in certain proportions, such as RME and linseed methyl esters [18]. Of course, this usually makes common practical sense mostly for oil crops that are found in the same geographical area, such as e.g. RSO and LSO in Northern and Central Europe. High levels of polyunsaturates can result in partial polymerisation of the fuel and when traces of such fuels seep from the cylinder into the engine oil during operation, sludge formation occurs, which can affect engine performance. There is, in fact, no direct relation between the unsaturation level in biodiesel and diesel engine malfunctioning. However, the level of unsaturation is directly linked with the oxidation tendency. The p-anisidine value [61] is a measurement of aldehyde content in an oil, principally 2,4-dienals and 2-alkenals. Aldehydes are secondary oxidation products produced during the oxidation of lipids, and many are flavour significant. The anisidine value is used to indicate whether oil colour is susceptible to darkening when subjected to heating. The Biodiesel Cost Optimizer model [62] relates FAME composition to cetane number, viscosity, iodine value, oxidation stability and density of a blend (see Section 14.4.4).

6.4

Agronomic potential of underexploited oil crops by region

Table 5.6 lists the annual global production of oils and fats. Additional raw material supplies for biodiesel may derive from: ∑

greater yields of oil per acre (‘virtual acres’), e.g. winter canola, soybean; ∑ production of oilseeds on new acres, e.g. camelina, winter canola and B. juncea; ∑ underutilised oil fruits and perennials; and ∑ investment in new, non-edible raw materials, e.g. algae, Jatropha, mustard, seashore mallow, brown grease, etc. There exists a wide variety of underutilised oil fruits, especially in tropical countries. Berger [63] mentions at least 15 species producing fruits with an oil-rich mesocarp. Preference should be given to non-edible oil sources. Camelina and corn oil are considered as near-term biodiesel feedstocks, whereas algae and jatropha qualify for the medium to long term. Nontraditional crops such as winter canola and rapeseed are also expected to

Emerging new energy crops for biodiesel production

245

make short-term contributions to the biodiesel feedstock supply. Mustard may become more significant by 2013. Mustard meal is being registered as an organic pesticide, and up to 15 M acres could be raised for biopesticides, with up to 70 gal oil/acre being produced as a co-product. Categories of suitable agricultural products for biodiesel production include seeds, nuts, fruits, leaves, stems, roots and tubers and tapped exudates. Root and tuber crops have considerable underrealised potential as new products for human, animal and industrial use. The properties of some vegetable oils, which have been considered for use as fuel, are described in Stout [64]. Self-seeding perennials require little or no tilling, minimal nitrogen and no fertiliser. The initial cost to establish these energy crops is estimated at US$100–250/acre but they live 10 years and yield 12–15 t/acre. Any new oilseed crop introduced to farmers will have to compete for acres. Those crops will either have to have a significant financial or agronomic benefit (as compared to corn and wheat) or grow on land unsuitable for conventional agricultural production. In fact, the world still has many convertible acres: up to 120 Mha in Brazil alone, and perhaps as much as 2.8 Mha worldwide, in particular in BRIC countries (Brazil, Russia, India, China) [65]. Countries without domestic petroleum resources are intensely investigating biodiesel opportunities. Depending on the climate and soil conditions, different types of vegetable oils as substitutes for diesel fuels are being considered. Use of marginal lands with soils too poor for food crops is to be encouraged to cultivate species like jatropha and camelina.

6.4.1 Indian subcontinent India consumed 40.3 Mt diesel in 2000–01, or 43.2% of the total consumption of petroleum products (two-thirds imported). The country stands in sixth place in the world in energy need and overall demand for crude oil, which is expected to rise annually by 5.6% up to 2011. Being a tropical country, India has rich and abundant forest resources with a wide range of plants and oilseeds of sufficient volume potential. The country has enormous potential of oilseeds of tree origin (TBOs) like cheura (Diploknema butyracea), jatropha (Jatropha curcas), jojoba (Simmondsia chinensis), karanja (Pongamia pinnata), kokum (Garcinia indica), mahua (Madhuca indica), neem (Azadirachta indica), simarouba (Simarouba glauca), tung (Aleurites spp.), wild apricot (Prunus armeniaca) and Chinese tallow (Triadica sebifera), which can be grown and established in wasteland and varied agroclimatic conditions. These have domestic and industrial utility in agriculture, cosmetics, pharmaceutics, cocoa-butter substitute and as diesel substitute. Most of these tree-borne oilseeds are scattered in forest and nonforest areas and scarcely 20% of the existing potential is being crushed and utilised. Indian oil and fat sources are still largely underutilised [66]. The

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Biodiesel science and technology

estimated Indian annual production capacity of various non-edible treeborne oilseeds exceeds 20 Mt [67]. The production of these oilseeds can be stepped up many fold if the government takes the decision to use them for producing diesel fuels. The Indian policy is largely to favour non-edible oils and fats for biodiesel purposes. The prohibitive cost of edible oils prevents their use in biodiesel application, at variance to non-edible oils. Simarouba (60–75% oil, 1000–1500 kg oil/ha; 36% SFA : C16 : 0 + C18 : 0) would need cracking in cold climates; oil and pulp are edible, at variance to many other species. Various vegetable oils from India (peanut, karanja, punnal, polang, castor, kapok, mahua, cottonseed, rapeseed, coconut and sesame) were investigated more than 60 years ago as fuel oils for diesel engines [68]. While castor bean is nowadays grown on a large scale on marginal and wasteland in South Asia, it appears that castor oil methyl ester would cause problems for most practical diesel engines because of its high viscosity (13.75 mm2/s compared to 3.2 mm2/s for mineral diesel) [69]. India’s biofuels industry is still in its infancy [70]. Initiatives are mainly at R&D level and demonstration plants with few small commercial units. India operates a 100 kt/yr crude palm oil/PFAD biodiesel plant. The prospects of biodiesel production from vegetable oils in India were recently described by Barnwal and Sharma [71]. Pongamia [72–77], Jatropha [78–82], and mahua [83, 84] have already shown their potential for biodiesel use. A method and system to produce ethanol and biodiesel from a combination of corn (maize) and other agro feedstocks (simarouba, mahua, rice, pongamia, etc.) has been described [85]. Jatropha is considered to be one of the best alternative non-edible oilseed crops for biodiesel production in India (and elsewhere), though with low power produced per unit area, and is now increasingly being used in reforestation programmes in tropical countries. India has up to 65 Mha of non-arable land available to produce jatropha, and intends to replace 20% of diesel fuels with jatro biodiesel. Numerous jatropha plantation projects are under way (see Section 5.9.1). Genetic improvement of energy crops such as Jatropha has barely begun. The estimated production potential of mahua oil is 181 kt/yr. India also grows 80 000 acres of its native Moringa oleifera (Moringa, Zogale). The tree oil crop moringa has multiple food uses (leaves, meal, seed). Moringa yields 3 t seeds/ha, producing 38–40% oil that contains 65% oleic acid, not unlike olive oil (see also Section 5.5). India also produces 5 kt/yr of highly acidic (17% FFA, unrefined), non-edible rubber (Hevea brasiliensis) seed oil, which requires a two-step transesterification for biodiesel production [86]. The overall potential of sal (Shorea robusta) seeds, which contain 18.5% of hard fat, is about 5.5 Mt/yr. Azam et al. [56] examined the fatty acid profiles of seed oils of 75 Indian plant species having 30% or more fixed oil in their seed/kernel. Fatty acid

Emerging new energy crops for biodiesel production

247

compositions, experimental or calculated values of SN, IV and CN were used to predict the quality of the corresponding FAME for use as biodiesel. Some 26 species, including Azadirachta indica (neem), Calophyllum inophyllum L. (undi), Jatropha curcas (physic nut), Pongamia pinnata (karanja) and Ziziphus mauritiana (Indian jujube or Chinese apple) (Table 6.7), did meet the major (inter)national biodiesel specifications; another 11 species conformed to the more permissive US standard only. The fatty acid composition of C. elatum (Guttiferae family) [87] is similar to that of C. inophyllum [56]. Cultivation of these plants on (part of) the Indian wastelands (totalling 94 Mha [88]) would satisfy the energy needs of India, currently on imports for 70% dependent (87.5 Mt imported petroleum/yr). Neem oil is being used as lamp oil in India. Neem and pongamia are also being used as a source of safe and renewable natural pesticides (not unlike mustard seed). However, as a result of W.R. Grace’s patent claims, the price of neem seeds has skyrocketed. The other qualifying non-traditional crops with seed oils for potential use as biodiesel deserve to be evaluated and could be developed and expanded for other regions of the world with different climatic and environmental conditions. For example, Mesua ferrea L. (nahor), also belonging to the Guttiferae plant family and rated positively by Azam et al. [56], contains a viscous crude oil which was already proposed as a diesel fuel raw material (fraction distilling between 473 K and 573 K) more than 20 years ago [89]. More recently, both karanja (CN 56.2) and nahor (CN 54.6) were evaluated positively as cheap raw materials for biodiesel fuel [90]. South-East Asian pili nut (Canarium ovatum) oil (Table 6.7) has poor nutritional value due to its low polyunsaturated fatty acid content (10.5%; compared with SFA and MUFA values of 44.5 and 45.0%, respectively) [91] and is a potential biodiesel raw material candidate. Kenaf (Hibiscus cannabinus L.) from the Malvaceae family is a valuable fibre plant native to India. Although kenaf is used mainly for its fibre, mass production of (edible) oil as a by-product could significantly increase the economic value of this crop [103]. A similar situation is encountered in Europe for cardoon. Because kenaf oil has lower linoleic and linolenic content (45.9% and 0.7%, respectively) and higher oleic acid (29.2%) than soybean oil (53.0%, 7.5% and 24.5%, respectively) it is expected to be more stable. Kenaf is related to cotton and okra; the kenaf oil composition is similar to cottonseed oil. Kenaf oil is characterised by a higher total phospholipid content (about 6.0%) than major oil seeds such as soybean (1.5 to 3.0%) and cottonseed (< 2.0%). Salicornia brachiata is a halophyte (salt-tolerant plant), used as a vegetable by mangrove-dependent village people. Potential industrial use of the saltwater irrigated crop (Chenopodiaceae family) oil has been prospected [107]. Quite different fatty acid profiles for salicornia oil are found in the literature (see Table 6.7), with a reported high 10-undecenoic acid (C11 : 1) content

Oil content SN (%)

IV

CN

Azadirachta indica 44a 201.1 69.3 57.8 Calophyllum inophyllum 65a 201.4 71.5 57.3 Jatropha curcas 40b 202.6 93.0 52.3 Pongamia pinnata 33b 196.7 80.9 55.8 Ziziphus mauritiana 33b 198.6 81.8 55.4 Vernonia cinerea 38a 205.2 68.5 67.5 Vernonia galamensis 35–42b 199.3 96.5 52.0 Lesquerella fendleri 30b 182.2 111.6 51.2 Cuphea epilobiifolia 10–40b 285.1 0 65.5 Cuphea viscosissimac n.d. 341.5 5.2 61.1 Euphorbia lagascae 42–52b 191.2 90.1 54.6 Coriandrum sativum 13–23.0b 199.2 101.8 50.8 Limnanthes alba 28 173.9 91.0 57.2 Limnanthes douglasii 27b 167.4 83.0 60.2 Madia sativa 31b 167.6 123.5 51.1 Hibiscus cannabinus 24b 210.5 113.8 46.6 Mesua ferrea 68.5a 201.0 81.3 55.1 Ficus benghalensis 20b 200.0 78.0 56.0

Fatty acid composition (wt%)

Reference(s)

16:0(14.9), 18:0(14.4), 18:1(61.9), 18:2(7.5), 20:0(1.3) 16:0(17.9), 16:1(2.5), 18:0(18.5), 18:1(42.7), 18:2(13.7), 18:3(2.1), 24:0(2.6) 14:0(1.4), 16:0(15.6), 18:0(9.7), 18:1(40.8), 18:2(32.1), 20:0(0.4) 16:0(10.6), 18:0(6.8), 18:1(49.4), 18:2(19.0), 20:0(4.1), 20:1(2.4), 22:0(5.3), 24:0(2.4) 16:0(10.4), 18:0(5.5), 18:1(64.4), 18:2(12.4), 20:0(1.8), 20:1(2.6), 22:0(1.2), 22:1(2.7) 14:0(8.0), 16:0(23.0), 18:0(8.0), 18:1(32.0), 18:2(22.0), 20:0(3.0), 22:0(4.0) 16:0(3.0), 18:0(3.0), 18:1(4.0), 18:1>O (67.2), 18:2(21.0), 18:3(0.1), 20:0(0.3) 16:0(1.0), 16:1(0.6), 18:0(1.7), 18:1(16.7), 18:1-OH(0.5), 18:2(6.8), 18:3(11.4), 20:0(0.8), 20:1-OH(56.3), 20:2-OH(3.5) 8:0(0.3), 10:0(19.6), 12:0(67.9), 14:0(12:2) 6:0(4.2), 8:0 (40.2), 10:0(36.9), 12:0(4.8), 14:0(6.8), 16:0(3.3), 18:0(0.2), 18:1(1.4), 18:2(2.0), 18:3(0.1) 16:0(4.3), 18:0(1.8), 18:1(22.3), 18:1>O(57.5), 18:2(9.6), 18:3(0.3) 14:0(0.1), 16:0(5.4), 18:0(0.4), 18:1(74.9), 18:2(18.6), 18:3(0.2) 16:0(0.3), 18:1(1.7), 20:0(0.5), 20:1(62.2), 22:1(16.4), 22:2(16.9), 24:1 (0.7) 20:1(65.0), 22:1(20.0), 22:2(10.0) 18:1(31.6), 18:2(52.4) 12:0(0.5), 14:0(0.4), 16:0(20.1), 16:1(1.6), 18:0(3.2), 18:1(29.2), 18:2(45.9), 18:3(0.7), 20:0(0.5), 20:1(0.2), 22:0(0.3), 22:1(0.7), 24:0(0.1) 14:0(0.9), 16:0(10.8), 18:0(12.4), 18:1(60.0), 18:2(15.0), 20:0(0.9) 12:0(1.5), 14:0(1.3), 16:0(35.2), 18:0(4.2), 18:1(32.2), 18:2(15.4), 18:3(8.7), 19:1(1.6)

[56] [56] [56] [56] [56] [56] [92, 93] [94, 95] [96] [97, 98] [99] [100] [101] [102, 103] [100] [104]

[56] [105]

Biodiesel science and technology

Species

248

Table 6.7 Emerging new energy crops

a

Oil content Oil content c Genetically d Oil content b

from kernel. from seed. altered plant strain VS-320. from tubers.

16:0(15.0), 18:0(2.6), 18:1(69.3), 18:2(13.1) 10-14:0(2.5), 16:0(6.7), 18:0(3.5), 18:1(35.0), 18:2(53.0) 16:0(8.9), 18:0(6.6), 18:1(34.7), 18:2(41.0), 18:3(1.7) 11:1(37.9), 14:0(12.9), 16:0(16.5), 18:1(32.8) 16:0(9.6), 18:0(3.0), 18:1(25.6), 18:2(61.0), 18:3(6.0) 16:0(1.8), 18:0(1.5), 18:1(16.5), 18:2(12.4), 18:2-OH(53.6), 18:3(0.6), 20:0(0.9), 20:1(1.1) 16:0(27.6), 18:0(5.2), 18:1(24.7), 18:2(36.9), 18:3(1.6) 14:0(0.1), 16:0(33.3), 16:1(0.3), 18:0(10.9), 18:1(44.7), 18:2(10.1), 18:3(0.5), 20:0(0.2)

[24] [106] [107] [108] [109] [110] [111] [91]

Emerging new energy crops for biodiesel production

Cyperus esculentus 20–36d 201.8 86.2 54.0 Guizotia abyssinica 30–50b 203.2 127.7 44.4 Silybum marianum n.d. 186.8 110.3 50.7 Salicornia brachiata 22b 248.3 81.9 49.9 Salicornia brachiata 28–33b 192.0 127.0 38.3 Dimorphoteca pluvialis n.d. 170.7 131.9 48.6 Pachyrhizus spp. 20–28b 196.7 93.6 53.0 Canarium ovatum n.d. 205.6 60.3 59.3

249

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Biodiesel science and technology

(37.9%) being suspect. S. brachiata oil is highly unsaturated and very rich in linoleic acid (61.0%). Similary, S. europaea oil also contains an appreciable C18 : 2 content [112]. Saponification number is high, as in the case of S. bigelovii [113]. The high content of saponins in the seeds of Salicornia makes the oil unsuitable for edible purposes. Cassia marginata and C. corymbosa (Leguminoseae family) oilseeds (Table 3.6) are characterised by very low oil contents and unacceptably low CN values [114]. On the other hand, as Ficus benghalensis (banyan tree) oil contains only small amounts of various unusual (epoxy, cyclopropenoid) fatty acids (Table 3.6), its potential use as a biodiesel feedstock might be envisaged.

6.4.2 South-East Asia The most significant palm oil producers (out of some 20 worldwide) are Malaysia, Indonesia and Nigeria (80% of production). An increasing demand for palm oil has fueled a 1.5% annual rate of destruction of rainforests in Indonesia and Malaysia, which together account for 86% of global palm oil production [115]. Malaysia doubled its palm plantations between 1990 and 2005 up to 3.75 Mha (or 60% of agricultural land); in the same period Indonesia increased palm plantations by 270% up to 4.1 Mha. Recent WWF estimates indicate 20 Mha of idle non-rainforest land suitable for sustainable palm oil production in South-East Asia, compared with 9 Mha of plantations in the region. Palm oil production estimates for 2008 of Indonesia and Malaysia amount to 18.7 and 17.7 MMT, respectively, up from 16.7 and 15.3 MMT, respectively, in the previous year. Palm oil production can expand by more than 5 MMT/yr, and even higher than expansion in food demand during certain years. Thus, an additional demand outlet (biofuels demand) is needed to preserve remunerative prices [116]. Malaysia is the world’s largest exporter of palm oil, currently accounting for 62% of world exports, mainly to P.R. China, the EU, India, Pakistan, the US and Egypt, with strong annual variations. Palm oil certified by the Roundtable on Sustainable Palm Oil (RSPO) is now available. Malaysia and Indonesia, which currently produce palm diesel for their domestic markets, could well develop considerable export potential, quite similar to Brazil. In particular, Malaysia aims at being the world’s biggest producer of biodiesel in a scenario in which the worldwide demand for this product is expected to increase significantly. The benefits of palm biodiesel for Malaysia are several: ∑ alternative to (expensive) petroleum-based fuel; ∑ chemical feedstock for biodegradable detergents and other chemicals; ∑ quality enhancement of palm oil by utilising palm oil products of low quality; and ∑ safety net in time of glut in the palm oil market.

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Carotech Ltd. (Ipoh, Malaysia) is a palm biodiesel producer which developed an integrated process that extracts and concentrates natural phytonutrients from CPO while producing biodiesel (CaroDiesel™) and glycerol. IndoFood (Indonesia) is diverting palm oil for food to biodiesel applications. Velva (ND) plans a two-million barrels per year canola biodiesel facility on Jurong Island, Singapore. Jurong Island is the scene of massive conventional oil and gas activities, including the construction of a 800 kt/yr NExBTL plant for palm oil hydrotreating (see Section 15.4.1). Thailand’s Chumporn Palm Oil Industry (producer of 20% of the country’s crude palm oil) is considering a 100 kt/yr biodiesel facility. ‘Super-biodiesel’ (biodiesel from recycled cooking oil) is in the testing phase. South Korea operates a 100 kt/ yr soy-based biodiesel plant. Japan is the largest soybean importer from the US. The country uses a considerable volume of soy biodiesel for heating oil. The world’s first cogeneration turbine fueled by biodiesel was installed in Matto-Ishikawa Central Hospital, Matto City, Japan, in 2002. Indonesia and the Philippines are major global players for coconut oil (Table 5.2). Mean annual production of coconut oil in the Philippines through the 1990s was 1.31 Mt based on data from the FAO [117]. In 2001, the Philippine Coconut Authority launched a nationwide programme to develop the use of coconut oil biodiesel as an alternative fuel. Since that time there have been efforts to commercialise coconut biodiesel (methyl ester) for use in vehicles and for off-grid power generation in small Philippine islands [118, 119]. A Philippine mandate for 1 vol% coconut methyl ester diesel blend is effective as from 1 March 2004. Installed coco biodiesel capacity in the country amounts to about 144 kt/yr (with 94 kt/yr more planned), including continuous processing. Production of 1 kg of coco biodiesel requires 1.667 kg of copra (dry coconut) and 0.143 kg of methanol. The process generates 0.667 kg of copra cake and 0.143 kg of glycerol as by-products [120]. The saturated medium-carbon chain of CCNO gives coconut methyl ester (CNME) a unique solvency quality and high cetane number of 70; the sub-273 K pour point of coco biodiesel makes it suitable for colder climates (e.g. Japan). Coconut biodiesel utilisation in the Philippine automotive transport sector benefits from net CO2 emission reductions which markedly exceed those of other vegetable oils (Table 6.8). This difference can be attributed both to the large amount of potential fuel in the residual biomass and the low-energy inputs in traditional coconut farming techniques (little mechanisation or utilisation of fertilisers and pesticides) as compared to the highly energyintensive agricultural practices for soybean, canola and rapeseed oils [120]. This results in a high energy ratio [121]. The coconut biodiesel life cycle system is shown in Fig. 14.4. Utilisation of all available coconut resources for biodiesel is sufficient to displace only 8% of the Philippines’ diesel fuel requirement in 2010. Increased production of biodiesel will require significant improvements in agricultural

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Table 6.8 Net CO2 emission reductionsa Net CO2 reduction (%)

Biodiesel

80.8–109.3 78 55 57–66 66

Coconut methyl ester with Philippines cogeneration using residual biomass Soybean oil methyl ester USA Soybean oil methyl ester USA Australia Canola oil ethyl esterb Rapeseed oil methyl ester Europe

a

Conditions

Reference [120] [122] [123] [124] [125]

Relative to petrodiesel. Ethanol for biodiesel production assumed to be derived from biomass.

b

productivity, or conversion of more land into coconut plantations. More productive (and energy-intensive) coconut production practices will not be beneficial to total CO2 emissions. The current price (2007) of CPO (more than US$625/t) is not conducive to making biodiesel. Domestic biodiesel production based on Jatropha curcas (tuba tuba) is to be established on plantations on idle lands in Quezon and Mindanao (Abudant Biofuels Corp.). South-East Asian nations (Malaysia, Indonesia, Philippines) are developing large-scale jatropha plantations. Indonesia has identified nearly 23 Mha of jatropha land potential. Other minor oilcrops in this tropical area may equally be of considerable interest. For example, low acid pumpkin seed (Cucurbita pepo L; Cucurbitaceae) oil (C16 : 0, 7.0–12.0%; C18 : 0, 6.0–7.0%; C18 : 1, 24.0–41.0%; C18 : 2, 46.0–57.0%; C18 : 3, 0.3–0.9%; IV 123 g I2/100 g, SN 132 mg KOH/g) is already commercially extracted. With its high oil content (48%) and oil yield (Table 6.1), pumpkin seed is a promising energy crop in a wide geographic area (India, South-East Asia, South America, Africa). Fruits of the Bornea tallow or illipe nuts (Shorea spp; Dipterocarpaceae family), growing in tropical rainforests of South-East Asia, contain edible oil bearing kernels with a typical fat content of 45–70% (composition: C16 : 0, 18.0%; C18 : 0; 43.3%; C18 : 1, 37.4%; C18 : 2, 0.2%; C20 : 0, 1.1%) [126].

6.4.3 P.R. China China’s total consumption of fossil diesel has increased from 51.4 Mt/yr in 1996 to 95.5 Mt in 2004, with about half of the share consumed by road and farm vehicles. The country has become the world’s third largest consumer of transportation fuels (after the US and Japan). China aims at limiting oil demand in 2020 to about 420 Mt with coal liquefaction (CTL) being the main domestic alternative under development; imports will amount to 100 Mt/yr. China’s oilseed imports (especially soya) have increased from 4.6 Mt/yr to 31.6 Mt/yr over the period 1997–2007. Crushing of oilseeds has risen from

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253

30 Mt/yr to 66 Mt/yr; the country has developed into the largest crusher of oilseeds in total, accounting for over 20% of global demand. Oil consumption has doubled from 14 Mt/yr (1997) to 28 Mt/yr (2007). Given the available agricultural potential of the country (122 Mha or 0.081 ha/inhabitant), which is far below the US potential (0.49 ha/inhabitant), China is unlikely to be able to grow energy crops to any large extent, unlike in Germany, for example. China is expected to need another 20 Mt of imported oilseeds in the next ten years. Major oil crops grown in P.R. China are sunflower (1.85 Mt), rapeseed (11.3 Mt), cottonseed (16.3 Mt), soybean (16.9 Mt), linseed (0.47 Mt), groundnut (14.6 Mt), castor bean (0.3 Mt), sesame seed (0.7 Mt) and tung nut (0.4 Mt) (production figures for 2005). Northeastern China grows the majority of soybean crop. Trial biodiesel production was based on RSO, CSO and UCO. The first (small) commercial biodiesel producer (Gushan, 10 kt/yr) (2001) used animal fat. The 2004 production of biodiesel amounted to a mere 38–60 kt. Gradual extension to about 100 kt/yr was expected for the following years. A 50 kt/ yr MFT biodiesel facility in Hainan province (Southern China) operates with imported palm oil and domestic jatropha oil (from 6.5 kha) as raw materials. The market for biodiesel is still limited to local distribution, direct sale and purchase, due to the low output and because it does not yet have unlimited market access to the main distribution network of the three leading Chinese petrol companies Sinopec, Petrochina and CNOOC. Economically feasible biodiesel production could be achieved for feedstock purchase cost not exceeding 7350/t (Table 6.9). In Sept. 2005 biodiesel was sold at 7400–425/t. At present, there are no subsidies from the Chinese government for biodiesel production. China is expected to increase biodiesel output to 200 kt by 2010 and to 5 Mt/yr by 2020 and has identified rapeseed as the most likely raw material in the short term. China is raising oil-bearing trees on some 4 Mha of land with a fruit Table 6.9 Cost comparison of biodiesel from different raw materialsa Feedstock Average consumptionb

Average feedstock purchase costc (7/t)

Average processing cost (7/t)

Average biodiesel cost (7/t)

Jatropha curcas L. 2 Pistacia chinensis Bunge 5 Xanthoceras sorbifolia Bunge 4 Cornus wilsoniana 5

115 60 80 65

85 85 85 85

315 385 405 410

a

Chinese conditions (end 2004). t feedstock/t diesel produced. c Incl. feedstock transport. b

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Biodiesel science and technology

output of about 4 Mt/yr and plans to cultivate 13 Mha of high-grade bioenergy forest by 2020, which will yield 6 Mt diesel. Raising biofuel forests in uninhabited mountain areas will save farmland. More oil-bearing trees could be planted on 57 Mha of underdeveloped wilderness. While China has banned the use of grain for bioethanol production (and focuses instead on yams, cassava and sugarcane), the country has recently set aside an area the size of England to produce non-food plants for biodiesel. In 2006 the Chinese State Forestry Administration (SFA) designated seven regions (Anhui, Hebei, Hunan, Inner Mongolia, Shanxi, Sichuan, Yunnan) to develop 400 kha of biodiesel forests by 2010, based on the main perennial shrubs and trees of Jatropha curcas L., Pistacia chinensis Bunge, Cornus wilsoniana and Xanthoceras sorbifolia. Integration into governmental programmes stimulates energy crop production on marginalised land. Breeding of high-quality seeds, such as Jatropha curcas L. and Pistacia chinensis Bunge, is rapidly advancing in China. Jatropha is still a relatively low profile crop in a country which has recently launched a massive Jatropha c. project. Conditions for Jatropha curcas L. plantation are most favourable in Guizhou and Sichuan provinces. Yunnan province has announced 650 kha of jatropha plantations. Hebei intends developing 870 kha of saplings of various kinds of biodiesel trees in its vast mountain areas to provide 5.5 Mt of seeds for extraction and refining by 2050. Guizhou province (South-West China) is also developing tung oil (13 kha plantations) for bioenergy. China is cultivating several food oils for large-scale biodiesel application, such as Chinese pistachio and yellowhorn. The current distribution of the Chinese pistachio tree (Pistacia chinensis Bunge; Anacardiaceae family), which yields an edible oil (40% content) also used to produce soaps and lubricants, covers at present some 67 kha (Hebei, Henan, Anhui and Shanxi provinces) but plantation is planned for 300 kha. Current production is fragmentary. While the oil has not yet been used as a feedstock for biodiesel, it offers good potential for this purpose. Similarly, the naturally widely distributed yellowhorn (Xanthoceras sorbifolia Bunge; Sapindaceae family), native to China, is currently mainly used for food oil but is now being developed into a biodiesel crop on a large scale. China is also a major producer of hempseed (Cannabis sativa L.) (Table 5.2). Hemp, which grows well in temperate climates with a lower agrochemical requirement than conventional oilseed crops, contains 25–35% oil and is well balanced in regard to the ratio (2.8 : 1) of the two essential PUFAs (C18 : 2 and C18 : 3) for human nutrition. The high amounts of a-linolenic acid (19%) of hempseed oil makes it especially prone to oxidation, but it may have favourable nutritional implications and beneficial physiological effects in the prevention of coronary heart disease and cancer. The hemp plant also provides a range of co-products that have significant commercial value for fibre and pharmaceutical products. The inexpensive but (in Europe) unused

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255

feedstock hempseed oil has been turned into biodiesel [127]. However, the fatty acid profile of highly polyunsaturated C. sativa oil (typically C16 : 0, 5.7–8.3%; C18 : 0, 2.2–2.8%; C18 : 1, 10.0–14.0%; C18 : 2, 54.3–60.5%; C18 : 3, 17.5–22.6%; C20 : 0, 0.9%; C20 : 2, 1.3%; C22:0, 0.3%; SFA 11%, MUFA 10%, PUFA 79%) [128] with high C18 : 3 (n-3/n-6) contents (> 12%, EN 14214 limits) and high IV (154–165 g I2/hg) [129] is not in favour for use as unblended biodiesel. Hemp biodiesel has a higher IV than rape biodiesel and comparable oxidative stability. Addition of 0.1–0.2% butylated hydroxytoluene (BHT) or mono-t-butyl hydroquinone (TBHQ) to hemp biodiesel is enough to fulfil the EN 14214 oxidative stability requirements. Mixtures of hemp oil with more saturated oils (e.g. waste palm oil) can be utilised for biodiesel synthesis. The Chinese tallow tree (T. sebifera) is a plant native to central China. The tree is most favourably grown in warm climates with well-drained soils, with the fruit being harvested in early winter after the leaves have fallen off. T. sebifera is shade, sun, drought, flood, freeze and salt tolerant. The Chinese tallow tree contains 20% oil and 24% tallow. The oil needs no refining. In plantations (400 trees/ha) T. sebifera would yield 14 t seed/ha, containing 2.6 t oil. Some reports mention 4000 to 10 000 kg/ha, and cite estimates of 25 barrels of oil per year as a sustainable energy yield. With some tolerance to salt, the tallow tree could be investigated as energy crops for saline situations. The country is moving towards the use of non-food crops that can grow under saline conditions, on hillsides and on other poor quality land. A wide variety of alternative material sources (including seed oil of Cerasus humilis, Wilson dogwood, candle berry tree, white Saunders, Sloanea sinensis, Daphniphyllum calycinum) is being tested in P.R. China for biodiesel synthesis. P.R. China also cultivates yellow nut-sedge (Cyperus esculentus L.) in various provinces. After refinement, yellow nut-sedge tuber oil can be used as a food oil as well as for industrial purposes. The potential fuel value of nut-sedge tuber oil was evaluated by Zhang et al. [24]. The oil is characterised by very high phosphorus content (73 ppm) – far exceeding EN 14214 limits – and very low peroxide value (6 meq/kg). Nut-sedge oil has lower cloud point and pour point temperatures than other vegetable oils. The oil has a great potential as a biodiesel fuel. A diesel engine using pure yellow nut-sedge tuber oil as fuel operated near its rated power [130]. A mixture of nut-sedge oil and diesel fuel performed better than pure oil. Microbial conversion of agricultural waste into biodiesel is another option under consideration.

6.4.4 Latin America South America (especially Brazil and Argentina) is a major oil crop producer, in particular for soybean (88 Mt/yr), oil palm (7.6 Mt/yr), coconut (4.0 Mt/yr),

256

Biodiesel science and technology

sunflower (4.6 Mt/yr) and castor bean (0.2 Mt/yr) (production figures 2005), but the potential is much higher given the large availability of farming land (150 Mha in Brazil). Consequently, there is also an enormous potential for biodiesel production, partly for export. Brazil, Argentina, Paraguay and Bolivia are the main producers of soybean in South America, contributing some 60% of world production. Brazil alone produces around one third of the world’s soybeans, with a 2007 harvest of 58.9 Mt across 20 Mha, 30% of which is grown in the State of Mato Grosso. While soy is the top cash crop in Brazil it is also a leading cause of deforestation in the Amazon. The Amazon lost 6950 square miles of rainforest in 2003–04, while some 4633 square miles of soybeans were planted during that time. Brazil is a global leader in bioethanol production with a production volume of about 5 Bgy (2006). Brazilian law stipulates that 20% of fuels at the pumps must be blended with bioethanol. Brazil runs half of its vehicle fleet on pure ethanol, made by fermenting sugarcane extracts. However, this approach relies on high-quality biomass, which is produced at a cost and could just as well serve as food for humans or livestock. The country is active in developing cellulosic bioethanol. As a result of domestic ethanol and petroleum production, Brazil is no longer import dependent. Similarly, already during World War II cottonseed oil was considered a strategic material by Brazil as a substitute for imported diesel fuel [131]. In 2002, the Probiodiesel (Programa Brasileiro de Desenvolvimento Tecnológico de Biodiesel) programme was formulated, aiming at setting up the regulatory framework for biodiesel development and production. Brazil has introduced mandatory blends of 2% by 2008 (800 ML/yr) and 5% by 2013 (2 BL/yr) with a goal of 20% by 2020, as well as numerous tax incentives for biodiesel producers that source their feedstock from local communities. Today, soybeans are the only oil-bearing material that supports the Brazilian biodiesel demand to any great extent but many other options are being considered such as sunflower (3 Mha), cottonseeds, peanuts, Jatropha, canola, palm, castor (4 Mha), among others. In addition to the production of soy methyl ester (SME), Brazil is considering development of soy ethyl ester (SEE). Both SME and SEE will be used as B5 blends in fossil diesel. Brazil has made an assessment of raw materials available regionally (Table 6.10) and of their suitability for biodiesel production. Moreover, Brazil disposes of 120 Mha non-cultivated arable land. In the framework of Brazil’s national biodiesel strategy, soy production is to be increased and planting of mamona (castor bean) is being promoted. Jamaica also intends producing castor biodiesel. Neat castor biodiesel would have a high viscosity. Other available resources consist of animal fat (total production of about 700 kt/yr from 40 million animals slaughtered in Brazil each year; additional 350 kt/ yr can be produced in Argentina, Uruguay and Paraguay) and fish wastes. Brazil, and especially the Amazon region, is an extremely rich source

Emerging new energy crops for biodiesel production

257

Table 6.10 Brazilian biodiesel feedstock options Region

Potential energy crops

North

Babassu, soybean, castor bean, palma, dendê, Jatropha

North-East

Babassu, soybean, castor bean, palma, cottonseed, coconut, Jatropha, peanut, fish wastes

Central-West

Soybean, castor bean, cottonseed, sunflower, palma

South-East

Soybean, castor bean, sunflower, cottonseed, peanut, fish wastes

South

Soybean, canola, sunflower, cottonseed, peanut, fish wastes

All

Industrial and municipal waste oils/fats, animal fatsb, soybean soapstock

a

Including palm soapstock. Except Central-West.

b

of plant germplasm. This vast country offers a wide variety of climatic conditions with excellent agricultural potential for exploration of highly diversified biomass resources for chemical, food and energy applications. Brazil aims at becoming a net exporter of biodiesel. Apart from waste oils and fats, biodiesel from Brazil may be based on short cycle oleaginous crops such as soybean, sunflower and rapeseed, medium cycle oleaginous crops such as Jatropha curcas and castor bean, and long cycle (permanent) oleaginous crops such as babassu, dendê (African palm), macaúba, peanut, coconut and many other native Amazon palms. High humidity in Amazonia is less suitable for temporary cultures. The pre-Amazonian region has excellent prospects for cultivation of oleaginous food and energy crops, including babassu, peanut, sunflower and castor bean. Babassu palms occupy 17 Mha in North-East Brazil (State of Maranhão). Babassu nuts have a reputation for being the hardest nuts on earth. Flour, animal feed, cosmetics, medicines and beverages can all be produced from the fruit, while the seeds contain a lauric oil (with similar properties to CNO and PKO) for cooking and fuel. Babassu has a production capacity of 17 Mt/yr oil, or 20 Mt/yr biodiesel. This crop alone could thus cover 50% of actual (2003) Brazilian diesel consumption. Semi-arid North-East Brazil could develop into a resource for castor bean (yielding up to 1000 kg/ha/ yr), coconut and sunflower. Other areas are important producers of soybean, sunflower and peanut (Table 6.10). Peanut is employed as a rotation crop in Brazil in association with sugarcane. The State of São Paulo is a main producer of peanut oil. Considerable investment in relevant research is needed to develop the most promising plants into commercially viable crops. Brazil, Mexico (Mexicali area) and Peru (San Martin province) have announced multiple Jatropha projects (> 100 kha). BioDiesel Technologies GmbH (BDT) has recently installed a commercial 40 kt/yr multi-feedstock plant in the State of Tocantins (North Brazil) with feedstock agreements with local cooperatives with 48 kha of Jatropha plantations and animal fat

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Biodiesel science and technology

from the state’s 6 million herd of cattle. Other Jatropha biodiesel projects are under way in the State of Goiás. Various South American oil palms show high oil yields (Table 6.1). Balick [132] has described 25 Amazon palm species with high oil content in their (edible) fruits. Many of these palms have great potential as economic crops. With the exception of Orbignya species (babassu), Acrocomia species (macaúba, mbocaya), E. oleifera (caire), Astrocaryum species (tucuma, murumura) and Bactris gasipaes (pejibaye), most species are not (yet) commercially exploited. In particular, macaúba palm (Acrocomia sclerocarpa) with low water requirement and very high yield (6 t/ha) may serve as an energy source [133]. Also tucuma palm (Astrocaryum aculeatum) or black palm is characterised by a high oil content (> 30%). Successful selection of commercially grown (Costa Rica) pejibaye or peach palm with 62% oil content could make this crop as important as coconut in the wet tropics [134]. Costa Rican Compania Nacional Bio Combustibles (CNBC) plans a 66 kt/yr biodiesel plant based on imported palm oil and domestic waste vegetable oil in Port Caldera, mainly for exportation. CNBC is also cultivating 6300 acres of jatropha, and castor bean will also be grown. Colombia produces palm biodiesel. The Paraguayan and Uruguayan biodiesel industries utilise animal fats. Amazon vegetable oils include caire, buriti, bacaba, copaiba, pequi and babassu oils. Babassu oil and many other Brazilian vegetable oils were considered as a fuel feedstock long ago [135]. Use of some of these oils has been investigated by Da Rocha Filho et al. [136]. Several other native Brazilian species and regular crops were evaluated in relation to biodiesel production, including macaúba, Jatropha curcas, indaiá-rasteiro (Attalea borgesiana) and pequi (Caryocar brasiliensis) oil [137]. The fruit of the pequi or Caryocar spp. (Caryocar brasiliense; Caryocaraceae family) tree found in the Amazon basin of central Brazil bears kernels yielding an edible oil that is highly prized by the indigenous population. Both kernel and mesocarp oils contain mainly glyceride esters of palmitic and oleic acids; compositions are as follows: mesocarp oil (C14 : 0, 1.5%; C16 : 0, 41.2%; C18 : 0, 0.8%; C18 : 1, 53.9%; C18 : 2, 2.6%) and kernel oil (C14 : 0, 1.4%; C16 : 0, 48.4%; C18 : 0, 0.9%; C18 : 1, 46.0%; C18 : 2, 3.3%) [138]. Pequi oil methanolysis at 318 K with 3% NaOH yields 97.7% methyl ester in 5 min. Brazil nut tree (Bertholletia excelsa; Lecythidaceae family) is one of the largest in the Amazon basin. High value edible Brazil nuts are used in baking trades. Only surplus or damaged nuts are used for processing into Brazil nut oil as a secondary product. Ripe kernels contain 65% oil (composition: C14 : 0, 0.6%; C16 : 0, 15.4%; C18 : 0, 6.2%; C18 : 1, 48.0%; C18 : 2, 29.8%) [139]. Among the 14 new crops from Brazil, described by Arkcoll [140], several species are of interest in relation to biodiesel potential. As babassu (81% SFA, mainly as lauric acid) grows in the same areas as sugarcane, its adoption

Emerging new energy crops for biodiesel production

259

as an alternative biomass-based energy system is of considerable interest to Brazil. Kernel oil compositions of the Amazon palm species A. lasiospatha, A. vulgare (tucuma), B. gasipaes (peach palm), E. oleifera and Maximiliana maripa were reported [141]. With the possible exception of oiticica (Ligania rigida) kernel oil, which contains a high amount of octadeca-9,11,13-trienoic acid [142], Amazon palm oils qualify for biodiesel application on the basis of SN, IV and CN values and linolenic acid content (Table 6.11). The FA profile of pecan (Carya illinoensis) kernel oil denotes a considerable source of monounsaturated fatty acids (SFA 8%, MUFA 65%, PUFA 27%), fairly similar to that of canola [143]. Other possible South American biodiesel sources are andiroba (Carapa guianensis) and cumaru (Dipteryx odorata) [144]. Buffalo gourd or wild gourd (Cucurbita foetidissima) and related species grow in desert wastelands (Mexico, USA) as a perennial vine. The crop is recognised as a potential commercial crop and is still being examined for its agricultural and economic potential. With its high oil yields (see Table 6.1) and oil content (34%), it is thought that the plant can match the performance of groundnuts and sunflowers as an oil producer. The polyunsaturated oil with composition similar to cardoon oil (see Table 6.11) is suitable for food and industrial use. The chemotaxonomy of 11 seed lipids of Cucurbitaceae species grown in Argentina was reported by Carreras et al. [145]. Alternative strategies for producing biodiesel include use of plant oil in leaves or tubers. The neotropical genus Pachyrhizus spp. (yam bean), with ecogeographical origin in Central and South America (Mexico, Peru), is a close relative to the soybean and phaseolus bean. Yam bean is a tuber crop with high seed and tuber yield (600 and 7000 to 10 000 kg/ha). The seeds of P. erosus contain one of the highest oil contents for cultivated legume species, second only to groundnut (A. hypogaea, 38–50% seed weight) [111]. In comparison with other members within the Leguminoseae family (e.g. soybean, groundnut, Acacia spp.), the seed oil content of yam bean is relatively high (20–28%) in combination with a high SFA content (34%). In addition, yam bean oil has the additional advantage of possessing a considerably lower linolenic (C18 : 3) acid concentration than mutants of soybean (4–8%) and flax (2.7–60.4%). Currently, yam beans are grown exclusively on a small scale for tuber production and the seeds remain as crop residuals on the field. However, these seeds could be used by farmers for small-scale oil processing. Yam bean is nowadays a popular crop in many Asian countries, as well as West Africa. Biodiesel application might suit recycling of post-maturation avocados for which economic outlets are sought (Dominican Republic). The fatty acid composition of avocado (Persea americana) oil (C16 : 0, 9–13%; C16 : 1, 2.8–4.0%; C18 : 0, 0.4–1.0%; C18 : 1, 69–74%; C18 : 2, 10–14%; C18 : 3, 1–2%; C20 : 0, <0.1%) is similar to olive oil. On the other hand, the chances

Fatty acid composition (wt%)

260

Table 6.11 Chemical properties of some edible high-oil producing crops Oil SN content (%)

IV

CN

Reference(s)

Macaúba palma

53–65

247.4

20.4

63.8 8:0(2.1), 10:0(3.7), 12:0(38.9), 14:0(11.0), 16:0(17.3), 18:0(4.3), 18:1(22.6) [146]

Pequi

60

207.5

51.8

60.9 16:0(44.3), 18:0(2.6), 18:1(48.7), 18:2(4.4)

[147, 148]

Buriti palm n.d. 205.8 80.2 54.8 14:0(0.1), 16:0(17.3-19.2), 18:0(2.0), 18:1(73.3-78.7), 18:2(2.4-3.9), 18:3(2.2)

[149]

Avocado 8–30 177–199 71–95 56.7 16:0(12.0-23.3), 16:1(4.2-11.2), 18:0(0.1-0.4), 18:1(47.2-73.0), 18:2(10.3-16.1), 18:3(0-0.4), 20:0(0.2-1.0)

[150]

Macadamian nutg 65–80 203.2 83.3 54.4 12:0(0.6), 14:0(0.8), 16:0(6.2), 16:1(19.1), 18:0(1.6), 18:1(67.1), 18:2(1.3), [151] 20:0(1.0), 20:1(1.7) Australian nutb 69–78 205.1 81.6 54.5 14:0(1.0-1.8), 16:0(8.4-11.1), 16:1(16.7-33.8), 18:0(1.5-2.8), 18:1(43.2-62.6), [152] 18:2(2.6-4.5), 18:3(0.2), 20:0(1.3-2.1), 20:1(1.4-2.6), 22:0(0.4-0.5), 22:1(0.1-0.2), 24:0(0.1-0.2) Babassu palm 63–70 237–286 20.3 61.4 8:0(2.6-7.3), 10:0(1.2-7.6), 12:0(40.0-55.0), 14:0(11.0-27.0), 16:0(5.2-11.0), [147] 18:0(1.8-7.4), 18:1(9.0-20.0), 18:2(1.4-6.6) 66 190–202 111–122 49.0 14:0(0.1), 16:0(7.2), 16:1(0.5), 18:0(2.1), 18:1(47.0), 18:2(41.0), 18:3(1.9), [153] Pecane 20:0(0.2), 20:1(0.4), 22:0(0.1) Pecanf

65–75

198.9

108.7

49.3 16:0(5.1-5.4), 18:0(2.5-2.9), 18:1(60.6-67.5), 18:2(22.1-27.5), 18:3(2.1-2.3)

Bacuri n.d. 204.2 72.9 56.6 8:0(1.0), 12:0(6.2), 14:0(3.2), 16:0(17.1), 16:1(0.4), 18:0(1.6), 18:1(53.8), 18:2(11.8), 18:3(0.9), 20:0(0.3), 20:1(0.2), 22:0(0.1), 24:0(0.2)

[143] [154]

Cocoa n.d. 207.2 96.3 51.0 12:0(0.9), 14:0(1.0), 16:0(33.6), 18:0(4.4), 18:1(3.3), 18:2(46.4), 18:3(9.5), [155] 20:0(1.1) Buffalo gourd

34

200.8

135.9

42.9 16:0(7.8), 18:0(3.6), 18:1(27.0), 18:2(61.5)

[156]

Biodiesel science and technology

Species

Bottle gourd n.d. 202.1 127.5 44.6 14:0(0.1), 16:0(13.8), 16:1(0.1), 18:0(6.6), 18:1(17.4), 18:2(61.4), 18:3(0.1), – 20:0(0.4), 20:1(0.1) Hazelnutc 40–48 197.4 89.3 53.9 16:0(1.9), 16:1(22.7), 18:0(0.5), 18:1(45.6), 18:2(5.6), 18:3(0.1), 20:0(1.4), [157] 20:1(9.7), 22:0(2.2), 22:1(9.5), 24:0(0.5)

Oat

n.d.

202.0

Cashew

44

185–205 80–86

a

107.6

49.1 16:0(13.8-16.0), 18:0(2.2-2.7), 18:1(44.1-50.2), 18:2(32.4-36.7), 18:3(0.8-1.0) [158] 53–57 16:0(10.7), 18:0(9.3), 18:1(61.2), 18:2(16.9), 18:3(0.3)

Acrocomia sclerocarpa M., endocarp fatty acid composition. New Zealand (Macadamia integrifolia, M. tetraphylla). c Chilean hazelnut (Gevuina avellana). d Hazelnut (Corylus avellana). e Origin: Southwestern United States. f Origin: Central Mexico. g Southern California. b

[159, 160]

Emerging new energy crops for biodiesel production

Hazelnutd 54–63 197.8 93.9 52.8 16:0(4.1-6.7), 16:1(0.1-0.7), 18:0(1.6-2.8), 18:1(72.8-83.5), 18:2(7.6-16.6), [3] 18:3(0.1-0.6), 20:0(0.1-0.2), 20:1(0.1-0.3)

261

262

Biodiesel science and technology Table 6.12 Motivation for biodiesel in South America (after ref. [165]) ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Availability of a large variety of renewable lipid sources Large availability of farming land Economy largely dependent on diesel Diesel partially imported Oil refining facilities near to limit High energy demand (electricity) in remote areas Decreasing air quality in highly populated urban areas Need for increasing job availability in the countryside Well-established agro-industrial activities Export markets

of employing other high-oil producing crops (Table 6.1), including popular oil fruits like avocado (leading producer: Mexico), prime edible nuts, such as brazil nut (B. excelsa), egg nut (Couepia longipendula), macadamia nut (Macadamia terniflora), hazelnut (Corylus avellana), Chilean hazelnut (Gevuina avellana), cashew nut (Anacardium occidentale), almond (Prunus amygdalus) and cocoa (Theobroma cacao) for biodiesel purposes are remote. Avocado oil finds application in cosmetics. The chemical composition of hazelnut oils depends on geographical origin, hazelnut variety and extraction process. The composition of the expensive hazelnut (Corylus avellana L.) oil is similar to olive oil. Walnut kernels (Juglans regia L.) contain 52–70% oil with major fatty acids C18 : 1 (13.3–21.3%), C18 : 2 (57.1–62.5%) and C18 : 3 (10.7–16.2%) [161, 162]. In view of the high commercial value of whole walnuts and cold-pressed walnut oil and high linolenic acid fraction, potential biodiesel application is negligible. Some of the less commercial oils, like hazelnut and almond, contain high amounts of monounsaturated fatty acids (80–81% and 60–80%, respectively). Macadamia (or Austrialian) nut oil (SFA 13.2–17.8%, MUFA 80.0%, PUFA 2.8–4.7%) is among the most highly monounsaturated oils available, containing higher levels than OO, HOSFO and RSO; the increased MUFA level in macadamia oil is mainly on account of significant amounts of palmitoleic acid (17–34%) [152]. Similarly, Chilean hazelnut (G. avellana) oil (SFA 6.5%, MUFA 87.5%, PUFA 6%), highly appreciated in the cosmetic and pharmaceutical industries, contains substantial amounts of unusual positional isomers of monounsaturated fatty acids (n-5 family), with 22.7% palmitoleic acid (C16 : 1). These nuts are the only ones to contain significant amounts of palmitoleic acid. Tree nut oils were recently reviewed [163]. The Peruvian Amazon perennial Plukenetia volubilis L. (Sacha inchi, Inca-peanut), in the Euphorbiaceae family, is a promising oilseed crop, rich in oil (35–60%) [164]. Its oil composition (see Table 15.13) lends itself to biodiesel production upon selective hydrogenation. However, Sacha inchi presents more desirable health benefits, being one of the largest plant sources of omega fatty acids (w3, 48%; w6, 36%; w9, 9%; see Table 3.2) and is

Emerging new energy crops for biodiesel production

263

therefore considered as a precious specialty food commodity and raw material for the nutraceutical industry. Ramos [165] has recently given an overview of biodiesel in South America. Table 6.12 summarises South Amerian motivation for biodiesel development.

6.4.5 Africa The African continent offers some important native energy crops for biofuel farming, such as the West African oil palm (E. guineensis), Ethiopian mustard (B. carinata) and crambe (Crambe abyssinica). The main vegetable oil crops in Africa are oil palm fruit (Nigeria, Ivory Coast, Cameroon, Congo, Ghana, Guinea; 14.4 Mt in 2005), groundnut (Nigeria, 2.9 Mt), olive (Morocco, 0.5 Mt), melonseed (Citrullus vulgaris) (West and Central Africa, 0.5 Mt), coconut (Ghana, 0.3 Mt) and sesame seed (Sudan, 0.3 Mt). Nigeria’s 1.4 Mt/yr vegetable oil production (2006) includes 815 kt palm oil. Oil palm is being planted specifically for biodiesel in Ivory Coast. Other typical West African oilseeds comprise castor bean, dikanut or African mango (Irvingia gabonensis; Simarubaceae) and African oil bean (Pentaclethra macrophylla) seeds [166]. The seeds of many members of the Cucurbitaceae family, which includes cucumbers, gourds, melons, pumpkins and squashes, have been noted for their oil-bearing properties. The fatty acid composition of bottle gourd or calabash (Lagenaria siceraria) (Table 6.11) is comparable to semi-drying oils such as SNO with 61.4% C18 : 2 (as in buffalo gourd). Younis et al. [167] have described the variability in fatty acid composition of seed oil of African pumpkin (Cucurbito pepo L.). West African edible fluted pumpkin (Telfairia occidentales; Cucurbitaceae) contains 13% oil. A related species (T. pedata) is grown commercially for its oil-rich seeds in East Africa. Information on oil composition is scarce. In Nigeria, a fast growing crop whose root could be utilised for biofuel production is tigernut (Cyperus esculentus L.), which at the moment is traditionally more valuable for its chemical and nutritional properties than as a fuel. Transesterification of tigernut oil leads to methyl and ethyl esters with fuel properties similar to common biofuels [168, 169]. Hence, tigernut can be utilised as an alternative renewable energy source. Seed oil of vernonia is produced on semi-commercial scale in Ethiopia. Nigerseed or noog (Guizotia abyssinica), also belonging to the Asteraceae family, is an important edible crop in Ethiopia. World production (Ethiopia and South India) of the slow-drying edible niger oil amounts to 200–300 kt/yr. As oil yields are modest (235 kg/ha), utilisation of niger as a diesel substitute is limited without further marked development [170]. Desert plants are Jatropha and Balanites aegyptiaca. Jatropha cultivation projects for biodiesel production in Africa are found in Burkina Faso (25 kha;

264

Biodiesel science and technology

D1 Oils), Ghana (2 Mha; Gold Star Farms Ltd., BDI Group), Madagascar (17 kha; D1 Oils), Malawi (55 kha; D1 Oils), Mozambique (300 kha; ESV, BioAfrica, Duelco, Energem Resources), South Africa (15 kha; Duelco), Tanzania (n.g.; Sun Biofuels), as well as in Egypt and Zimbabwe. ESV Bio-Africa aims at establishing over 100 kha of oilseed crops (biodiesel farms) in sub-Saharian Africa over the next decade. Balanites aegyptiaca L. (balanites) fruits are composed of edible mesocarp and kernels, the latter containing 40–46% edible oil (composition: SFA, 24.0%, mainly C16 : 0 and C18 : 0; C18 : 1, 31%; C18 : 2, 12–14%), called Zachun oil [171, 172]. Some 14 kt of oil could be extracted from existing balanites resources in the Sudan. Desert date or lolab tree (Zygophyllaceae family) is a very droughttolerant all-purpose tree or shrub suited to all arid regions and is particularly widespread in African savannah areas, the Arabian Peninsula as well as in the drier parts of India and Pakistan. In colonial times, the French government was particularly interested in the diesel engine for use in African countries with access to considerable quantities of groundnuts (peanuts, cashews and Jatropha). South African feeds of interest include soybean and jatropha oils. The country plans for 90 algal oil units producing 33 kt/yr each, i.e. 3 Mt/yr. Biodiesel could replace 20% of imported diesel. While Africa is rich in biodiesel projects, it needs translation into industrial realisation (Petrobas is planning a production unit). Domestic fertiliser production is seen as the key to boost the present low agricultural yields in various sub-Saharan countries (in particular in Senegal, Burkina Faso, Malawi, Kenya and Tanzania) [173]. A large African agricultural sector would not only help production of more food but could also be the source of supply of crops with important industrial outlets. Oilseeds and starch-rich tubers have considerable potential for manufacturing sectors, comprising oleochemicals and other renewables-derived products (e.g. biofuels). Energetic agriculture and chemicals sourced from agriculture hold promise for sub-Saharan industrial development. Africa is estimated to dispose of about 25% of the world’s combustible bioenergy resources. Rwanda (MFT facility) and Mozambique (Ecomoz project, CNME) are active producers.

6.4.6 Temperate agroclimatic areas Green plants in the US collect some 50 ¥ 1015 Btu of sunlight energy per year, whereas the US population consumes more than twice that amount of energy from fossil fuels. Historically, soybean oil has provided up to 80% of the feedstock used to produce US biodiesel. As the industry continues to grow, new feedstock sources are being developed, which include animal fats, restaurant grease, and ongoing research on other energy crops. Seven VO crops that are common to the North American continent have

Emerging new energy crops for biodiesel production

265

most potential as biodiesel feedstocks, namely soybean, rapeseed and canola, mustard, sunflower, corn/maize, peanut and camelina. In the US canola is grown almost exclusively as a spring crop. Expansion of winter canola acres in the Great Plains and mid-South would add to the vegetable oil supply. The US DOE mustard project (2000–2002) has developed industrial mustard crops for biodiesel, in conformity to the requirements of Table 6.13 [5]. The key development that makes mustard so promising is that the defatted meal can be used as a pesticide without further processing. In fact, there has been great faith in mustard seed for over 2000 years [174]. Montana’s newest, non-native, oilseed crop is camelina (dodderseed); see Section 5.9. Camelina crop acreage in Montana has increased from 20 000 acres in 2006 to 50 000 acres in 2008 (actually below expectations). Great Plains Oil and Exploration – The Camelina Co. (Bigfork, MT)/INEOS Enterprises (UK) have established a goal of growing 1 million acres of camelina for the production of 100 Mgy of camelina biodiesel by 2012. Sustainable Oils Co. (Bozeman, MT), a partnership between Targeted Growth, Inc. (Seattle, WA) and Green Earth Fuels, LLC (Houston, TX) has set a similar nearterm goal of 1 million acres. Camelina is considered to be the nearest-term next feedstock for biodiesel and close to being commercialised (City Farm Biofuel Ltd., Delta, BC; 10 MMLy). Hawaii is producing biodiesel from yellow grease, and intends using locally grown sustainable feedstocks and imported palm oil (RSPO standards). Moreover, Hawaii has finalised a policy (HECO/NRDC) which aims at developing a local agricultural energy industry by planting palm, jatropha, coconut and kukui nuts as oil feedstocks on 140 000 acres that are now fallow due to the decline of pineapple and sugar production. Jatropha pilot projects are also starting up elsewhere in the US (5 kha; Xenerga). US biodiesel Table 6.13 Selection criteria for introduction of new energy crops to US market ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Crop in early commercial production stage Crop yield/acre comparable to other commercial crops High oil yield (25–40%) Availability of suitable production and crushing technology Suitability for large-scale production Low input, significant environmental benefits (e.g. rotation) Ability to supply 6–12 billion gal. feedstock oil MUFA > 90% Inedible (humans and lifestock); no high value for industrial use Profitable for farmers and crushers Low oilseed crushing costs (< US$0.10/lb, 2001) High market value of meal (> US$0.12/lb, 2001) High market demand for meal (billions lb) Expanding market prospects for meal

Source: US DOE.

266

Biodiesel science and technology

industry investment and interest is growing also in other non-edible raw materials such as algae (see Sections 5.7 and 9.5), field pennycress, seashore mallow and brown grease. Field pennycress (Thlaspi arvense L.) is a winter annual weed of the mustard family, which is off season from corn and soybeans, has high seed yield (2000 lbs/acre) and oil content (36%), comparable to or better than canola. Pennycress oil (with high SFA) meets all the parameters required for biodiesel. The cloud point and oxidative stability are better than soy-based biodiesel. The agronomic potential of the weed is high: it is a low-input crop requiring very little fertilisation, can be harvested easily with existing equipment and does not present shattering problems. Pennycress (also known as stinkweed or frenchweed) could become a winter crop for biodiesel without competing for corn or soybean acres [175]. Field trials are under way in Newark, NJ (for the 40 MMgy Innovation Fuels Inc. plant) and in Illinois. Seashore mallow (Kosteletzkya virginica) or sweat weed is a perennial herb of the Malvaceae family found in marshes along the eastern seashore of the US and is considered as a potential new biodiesel feedstock. This flowering plant of the order Malvales is a halophyte or salt-tolerant plant. With an oil content of approximately 18%, this crop can be grown on saline land and produce vegetable oil on underutilised or non-arable land. Seashore mallow has a productive life of about a decade and the oil composition is very similar to cottonseed oil. Breeding efforts have been almost non-existent. Consequently, yields of seashore mallow are low compared to other oilseeds. Various ways are envisioned to improve the agronomic performance of seashore mallow: growth on salinised farmland, growth on dry farmland with brackish water wells, growth on sandy coastal desert or growth on farmland or aquatic ecosystems in transition. Milkweed (Asclepias syriaca) is an underutilised perennial plant, native to Northeast and North Central United States; seeds contain 20–25 wt% (dry basis) oil (C16 : 0, 5.9%; C16 : 1, 6.8%; C18 : 0, 2.3%; C18 : 1, 34.8%; C18 : 2, 48.7%; C18 : 3, 1.2%; C20 : 0, 0.2%; SFA 8.4%, MUFA 41.6%, PUFA 49.9%) with potential for technical applications, including biodiesel [176]. Developers and farmers are also paving the way for hemp as a biomass crop in the US. The crop is legally grown in Canada. Large-scale agricultural feedstocks in Canada include cereals (barley, wheat and oat) and oilseeds (canola, linseed, soybean, mustard, sunflower and safflower) with production of the latter being second to that of cereals. Projected canola production, now grown on more than 15.5 million acres of Canadian farmland (17 million acres by 2015), is expected to rise from about 11 Mt (2007) to 16.5 Mt (2015) [177]. If canola were to meet the Canadian 2012 biofuels mandate of 2% for heating oil, which is unlikely, 1.8 Mt of canola would be needed. B. carinata is a potential oilseed crop for dry areas of the Western Canadian

Emerging new energy crops for biodiesel production

267

prairies, but this requires development of canola-quality traits [178]. The oleic acid content of zero-erucic acid B. carinata is low (28.3%) compared to B. napus (62.0%), while linoleic and linolenic acid contents are higher. C. sativa (see Section 5.9) could sustain a small biodiesel market in West Canada (Camelina Canada, Lethbridge, AB). Chokecherry (Prunus virginiana), a small tree native to North America and the official fruit of the State of North Dakota, is still at a very early stage of development as an industrial crop. Chokecherries, a common wild fruit producing shrub on the Canadian prairies and very high in antioxidants (anthocyanins), contain surprisingly high levels of edible seed oil. With a seed yield of 2250 kg and based on a 30% oil content, the oil yield of this hardy northern perennial species is 675 kg/ha. For comparison, a typical canola crop (1300 kg/ha) yields 546 kg oil/ha. Moreover, Canada has vast resources of tall oil and black liquor, whereas British Columbia presents opportunities for biodiesel production from recycled bio-oils and rendered animal fats (see Section 14.6.3), fish oils and seafood wastes. Much of the planned expansion of the EU biodiesel industry is still dependent on several factors, including tax incentives, legislative changes and feedstock availability. Rapeseed oil is well suited for fatty acid esters in North-West Europe, being domestically produced and thus favoured. The maximum area for rapeseed cultivation in Germany is estimated to be 1.3 Mha, which means about 1.5–1.8 Mt/yr biodiesel. A diesel fuel share of 10–15% in Europe seems to be achievable. Although other vegetable oils are suitable for fuel use, most of them are agronomically unsuitable for the UK Raw materials are a recognised scarcity in Southern Europe; these countries rely largely on imports (SBO, SNO). The European biodiesel feedstock will eventually be augmented by PMO, TLW or UCO. The physical and chemical characteristics of palm oil limit its potential as a biodiesel feedstock in Northern Europe and the UK. As regards Italy, development of 40–80 kha of bioenergetic crop production is expected for 2007–08, with forecasts for 2010 in the range of 200 kha (mainly sunflower and corn). The European Technology Platform (ETP) ‘Plants for the Future’ is working towards a European knowledge-based bioeconomy [179]. Table 6.14 lists the main emerging oilseed crops in temperature agroclimatic areas, which are at various stages of industrial development. As already mentioned in Section 5.9, cardoon (Cynara cardunculus) qualifies as a suitable biodiesel raw material for the Mediterranean area; crop development programmes are under way. Similarly, the potential of hemp (Cannabis sativa L.) as a biodiesel feedstock crop (see Section 6.4.3) is being explored in the UK from an economic perspective [180]. Plant breeding efforts to domesticate wild plants such as species of the genera Cuphea, Calendula, Euphorbia, Vernonia, Lesquerella, Crambe, or Limnanthes, in order to develop useful plants that may be more productive,

268

Biodiesel science and technology Table 6.14 Emerging oilseed crops in temperate agroclimatic areas Oilseed crop

Area

Bay laurel (Lauris nobilis) Camelina (Camelina sativa) Cardoon (C. cardunculus) Castor bean (R. communis) Chokecherry (P. virginiana) Crambe (C. abyssinica) Cuphea (Cuphea) Eruca (E. sativa) Ethiopian mustard (B. carinata) Field pennycress (T. arvense) Hemp (Cannabis sativa) Holy thistle (S. marianum) Isis (Brassica oilseed) Lesquerella (L. fendleri/L. angustifolia) Meadowfoam (Limnanthes) Mustard (B. juncea) Pot marigold (C. officinalis) Rain daisy (D. pluvialis) Safflower (C. tinctorius) Seashore mallow (K. virginica) Tarweed (Madia sativa) Vernin spurge (E. lagascae) Vernonia (V. galamensis)

Turkey USA, Canada Mediterrenean Various Canada Various Various Northern Italy West Canada, Mediterrenean USA UK Various Ukrainea Central Italy Various USA Central Italy, Netherlands Netherlands Sicily USA Central Italy Various Central Italy

a

Landkom Intl. PLC/Sunfuel Ukraine LLC co-development.

are numerous [181–183]. Among the underexploited temperate climate industrial crops with potential new oilseeds, meadowfoam (Limnanthes ssp.) has already gained active crop status, whereas Lesquerella, Cuphea, Euphorbia and Vernonia, which have the capacity to produce oils containing high proportions of unusual components, such as medium-chain fatty acids, petroselinic and vernolic acids, require further breeding, agronomy or processing research [184]. Meadowfoam is a rich source of unique unsaturated long-chain fatty acids (LCFAs), in particular cis-5 unsaturated fatty acids (20 : 1D5, 22 : 1D5 and 22 : 2D5D13). Meadowfoam seed oil thus contains some 95% of fatty acids with chain lengths of 20 carbon atoms or longer (C20 and C22 monoenes and dienes) [103]. The unique chemistry of meadowfoam (SFA 1.0%, MUFA 82.0%, PUFA 17.0%) has stimulated its development as an industrial oilseed crop [100]. Most of the crop development work of meadowfoam has concentrated on L. alba because of the excellent seed-retaining characteristics of this species. L. douglasii, the only other Limnanthes species with commercial promise has a serious seed-shattering problem. Being mainly composed of monoenoic fatty acids, meadowfoam oil has many interesting physical properties such as an unusually high oxidative stability index compared with other vegetable oils (Table 6.6). The

Emerging new energy crops for biodiesel production

269

oil chemistry of meadowfoam results in commercial oil values exceeding those of soybean oil; initial target markets are therefore primarily high-value personal care products, rather than fuel applications. The uniquely high level of the hydroxyl fatty acid (HFA) ricinoleic acid (C18 : 1-OH) in castor (Ricinus communis) oil (88%) imparts increased lubricity to the oil and its derivatives as compared to other vegetable oils. For a similar reason, the developing oilseed Lesquerella also increases diesel lubricity [93]. The primary fatty acid in the non-commercial crop Lesquerella fendleri (lesquerella, Fendler’s bladderpod), a species in the mustard family and perennial in nature but cultivated as a winter annual, is lesquerolic acid, a hydroxy-eicosenoic acid (C20 : 1-OH, 55–69%); also small amounts of auricolic acid (C20 : 2-OH) are present. Hydroxyl functionality is rare in plant oils. HFAs are classified as strategic materials by the US government. Special properties of HFAs compared to other fatty acids include higher viscosity and reactivity, caused by the presence of the hydroxyl group. Lesquerella oil applications are most likely to be targeted at high-value products such as additives, cosmetics, coatings and lubricants. An obstacle is its reddish-brown colour. As the C18 : 3 (linolenic acid) content of L. fendleri is quite variable, usually almost 15% but occasionally as high as 36% [185], application as biodiesel raw material might not be without problems. However, the observed increase in lubricity make castor and Lesquerella oil esters prime candidates as additives for ULSD fuel at concentrations of about 0.25% [94]. Intensive research efforts currently aim at successful introduction of L. fendleri into agriculture. At present the crop shows slow germination and seedling development, lack of seed retention and low seed yield. Whereas L. fendleri is a good candidate for domestication in arid areas, being native to southwestern USA and northern Mexico, L. angustifolia performs better in high-latitude environments with very cold winters (e.g. Patagonia) [186]. The genus Cuphea spp. (Lythraceae) comprises several hundreds species with very diverse compositions emphasising medium-chain triglycerides (C8-C14), in particular high C8 : 0–C14 : 0 levels. The specific dominant fatty acid varies with the species, e.g. C8 : 0 in C. painteri (73.0%), C10 : 0 in the monoacid seed oil C. koehneana (95.3%) and C12 : 0 in C. epilobiifolia (67.9%) (see Table 6.15); other unique compositions of seed oils with up to 80% lauric acid have been found [187, 188]. Markets for medium-chain triglycerides (MCTs, C8-C10) have considerable commercial potential, especially as lubricants and nutritionally desirable and medically useful oils. MCT demand is currently met mainly by coconut and palm oil, both of which also contain fairly high levels of lauric acid (C12 : 0, ca. 50%). Reasonable expectations for cuphea biodiesel are low viscosity and iodine number, good cetane number, colour and oxidation stability, high cloud point, but poor flash point and cold-temperature properties. The high saponification number (see Table 6.7) is likely to impart high foamability.

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Biodiesel science and technology

Table 6.15 Diversity in fatty acid composition in Cuphea germplasm (% of total fatty acids) (after refs [96, 98]) Species

C8:0

C10:0

C12:0

C14:0

Others

C. C. C. C. C.

5.3 0.3 0.2 73.0 18.5

81.4 19.6 95.3 20.4 71.0

4.7 67.9 1.0 0.2 2.0

8.6 12.2 0.3 0.3 1.0

0.0 0.0 3.2 6.1 7.5

carthagenensis epilobiifolia koehneana painteri viscosissima

In analogy to the case of meadowfoam, the presence of unusual fatty acids (caprylic, capric and myristic), in addition to the more common lauric acid, could add more value to the oil when used in new applications. Current breeding programmes focus on improving agronomic traits necessary for Cuphea domestication and commercial production. Among the euphorbs, the non-commercial Euphorbia lagascae (vernin spurge) is unique in that the oil contains high levels (60–65%) of vernolic (12,13-epoxy-cis-9-octadecenoic) acid, a natural epoxy fatty acid (EFA). Similarly, seed oil of vernonia (Vernonia galamensis; Asteraceae), which is produced in some parts of the world (Ethiopia) on a semi-commercial scale, contains large amounts (up to 80%) of vernolic acid. For variation in V. galamensis flowering characteristics, seed oil and vernolic acid content, see ref. [189]. Oil from Euphorbia has good oxidative and thermal stability characteristics, and has better oxidative stability than RSO, which assists industrial utilisation and its ability to compete with mineral oils. Moreover, as epoxidation of simple vegetable oils (e.g. SBO and LSO) is an expensive process, euphorbia and vernonia oils would be more expensive than soybean oil. Costs for producing methyl vernolate are of the same order of magnitude for production of RMEs (almost 70.28/kg), but this is still half the total cost of methyl vernolate production (70.51/kg at a production of 120 t/d). Currently, processing costs for new oil crops are higher than those for conventional oil crops. At present, this limits their potential use to markets with high added-value. The fatty acid composition of coriander (Coriandrum sativum), grown primarily as a spice crop with low world market tonnage (200 t/yr), is of scientific interest because of the high level of petroselinic acid (6-octadecenoic acid, or a C18 : 1 isomer) (Table 6.7). However, further research is needed before coriander becomes a viable industrial (non-food) crop [190]. Oil content of this herb is low (typically 13–18 wt%), but plant breeding could result in high-oil varieties (23%). The agronomic potential of the underexploited oilseed crops Calendula officinalis (pot marigold), Camelina sativa (cameline, linseed dodder or false flax), Lepidium sativum (garden cress), C. sativum (coriander), Madia sativa (tarweed), E. lagascae, V. galamensis and L. fendleri has recently been

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examined by Angelini et al. [100] for application in Central Italy. Some of these species produce high levels (>50%) of a single fatty acid in their seeds, notably C. sativum (petroselinic acid), M. sativa (linoleic acid), L. fendleri (lesquerolic acid), V. galamensis and E. lagascae (vernolic acid). Although this finding may favour specific industrial use by minimising downstream processing costs, it is not particularly relevant to biodiesel applications. L. sativum and Camelina sativa do not appear to qualify as energy crops in view of their high linolenic acid contents, namely 20.4–29.5% and up to 39%, respectively. Due to its high content of unsaturated fatty acids (PUFA 54%, MUFA 35.5%, SFA 10.5%), the oil of Camelina sativa (Brassicaceae) (C16 : 0, 5.4%; C18 : 0, 2.6%; C18 : 1, 14.3%; C18 : 2, 14.3%; C18 : 3, 38.4%; C20 : 0, 0.25%; C20 : 1, 16.8%; C22 : 0, 1.4%; C22 : 1, 2.9%) is fast drying [191–193]. Therefore, it can be used in industrial production of colours, varnishes and soaps [194]. Exploitation of cameline oil in the food and nonfood industries would open large marketing possibilities [193]. Nevertheless, non-food exploitation of cameline oil has been proposed as a biofuel (see also Section 5.9). The oil has also been used as biofuel in a mixture with diesel oil without transesterification [195]. In spite of a high iodine number (about 160 g I2/100 g) successful experiments on a pilot scale were carried out with conversion of the oil into methyl ester [196]. High FFA levels (3.1%) reduce methyl ester yield in single-stage esterification of cameline oil using KOH [191]. Cameline methyl ester presents various problems for biodiesel application: IV, 152–157 g I2/100 g, exceeding the limits of all (inter)national standards; high C18 : 3 contents, 38.4%; and low-temperature running problems in cold climates (CFPP 266–270 K) [191]. The latter problem could eventually be overcome by the use of suitable pour-point depressants or by blending with diesel oil or with RME (as for linseed oil methyl esters). For a more appropriate use as a biodiesel raw material, it would be necessary to reduce the content of highly unsaturated fatty acids. In mutation experiments the C18 : 3 content was lowered to 19.1% [192]. (See also Section 5.9.) The Mediterranean crop eruca or rocket (Eruca sativa spp. oleifera), newly developed for industrial use (non-food oil) in the Po Valley pedoclimatic conditions within the framework of the European Common Agricultural Policy, contains 29% oil. The fatty acid composition (Nemat: C16 : 0, 5.1%; C18 : 0, 1.3%; C18 : 1, 15.1%; C18 : 2, 8.3%; C18 : 3, 14.7%; C20 : 1, 8.7%; C22 : 1, 45.3%) with a high level (53–55%) of long-chain fatty acids [197] is not quite favourable for biodiesel application. Eruca seed oil is mainly used in industries as a lubricant and detergent, in printing inks and for production of polymer slip additives (erucamide). Lupin (Lupinus mutablis variety), grown on poor, leached soils in Italy and Peru, yields 17–22% oil. White sweed or Mediterranean lupin (Lupinus albus L.; Fabaceae family) is a neglected food legume which contains 10.7% oil with composition (C16 : 0, 7.6%;

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C18 : 0, 1.5%; C18 : 1, 47.6%; C18 : 2, 20.3%; C18 : 3, 9.2%) resembling that of groundnut and erucic-acid free canola [198]. The oil content needs to be improved. C. officinalis seeds contain some 37% or more of the conjugated polyunsaturated calendic acid (trans, trans, cis-8,10,12-octadecatrienoic acid, C18 : 3c), which probably determines poor shelf-life in biodiesel applications, not unlike tung oil. Consequently, of the various oilseed species with good agronomic traits such as tolerance to drought and high temperature, and suitable for cultivation and further breeding in Central Italy [100], only E. lagascae, V. galamensis, C. sativum, L. fendlerii and M. sativa qualify as potential energy crops. The latter tolerates arid conditions. The recent development of seed-retaining mutants has increased the commercial promise of E. lagascae [199]. V. galamensis is characterised by poor seed yield. Among the several (potential) energy crops of the Asteraceae family (comprising sunflower, safflower, cardoon, niger) cardo mariano or holy thistle (Silybum marianum) should be mentioned [107]. The better adaptability and productivity of B. carinata in semi-arid climates, with respect to B. napus, make B. carinata a promising oil crop for energetic purposes in environments where B. napus cannot show its productivity, such as Mediterranean climate marginal areas and coastal areas of Central and Southern Italy. B. carinata was indicated as an alternative domestic crop for production of biodiesel in Italy [200]. Pilot plant studies of biodiesel production using B. carinata as raw material were also undertaken in Spain [201]. Crop development for biodiesel applications in Italy is likely to concentrate mostly on rapeseed (Northern Italy), B. carinata and cardoon (Southern Italy); safflower is considered to be less suitable in view of its high water requirements. Four arable oilseed crops, namely E. lagascae, Crambe abyssinica, Dimorphotheca pluvialis (rain daisy) and C. officinalis were investigated within the framework of a Dutch National Oilseeds Programme (NOP) [202]. D. pluvialis (L.) Moench (Asteraceae family) is an annual endemic to southern Africa, its seed oil (Table 6.7) is probably best used in relation to its high hydroxyl fatty acid (C18 : 2-OH) content. The economic feasibility of using oat as an oilseed crop (see Table 6.1) depends on the availability of oat cultivars with groat (caryopsis) oil contents in the range of 17% with acceptable agronomic performance. Oat (Avena sativa L.) groat (caryopsis) oil content is highest of all the cereal grains [158]. High-oil oat with oil concentrations of 6.9–18.1% have been reported [203, 204]. Amaranth (Amaranthus) with a fatty acid profile of the cereals groups (see Fig. 6.1) is not a typical oilseed crop. The lipid content of Amaranthus seed is usually only 6–9%, but up to 19.3% for some species such as A. spinosus and A. tenuifolius. The fatty acid compositions of cottonseed oil and amaranth oil (C14 : 0, 0.2; C16 : 0, 22.9; C16 : 1, 0.1; C18 : 0, 3.6; C18 : 1,

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26.2; C18 : 2, 45.0; C18 : 3, 0.8; C20 : 0, 0.7; C20 : 1, 0.2; C22 : 0, 0.2; SFA, 27.6, MUFA, 26.5, PUFA, 45.8; all in wt%) are similar [205].

6.5

Bibliography

W. Thurmond, Biodiesel 2020. A Global Market Survey, Emerging Markets Online, Houston, TX (2008). E.N. Frankel, Antioxidants in Food and Biology: Fats and Fiction, The Oily Press Lipid Library, Vol. 20, Bridgwater (2007). J. Janick and A. Whipkey (eds), Issues in New Crops and New Uses, ASHS Press, Alexandria, VA (2007). A. Dalby, Food in the Ancient World from A to Z, Routledge, London (2003). H. Zoebelein (ed.), Dictionary of Renewable Resources, 2nd edn, WileyVCH, Weinheim (2001). D. Zohary and M. Hopf, Domestication of Plants in the Old World, Oxford University Press, Oxford (2000). N. El Bassam, Energy Plant Species: Their Use and Impact on Environment and Development, Earthscan Ltd, London (1998). J. Smartt and N. Haq (eds), Domestication, Production and Utilization of New Crops, Colorline Printers, Dhaka (1997). J. Janick (ed.), Progress in New Crops, ASHS Press, Alexandria, VA (1996). K. Warner and N.A.M. Eskin (eds), Methods to Assess Quality and Stability of Oils and Fat-containing Foods, AOCS Press, Champaign, IL (1995). S.L. Mackenzie and D.C. Taylor (eds), Seed Oils for the Future, AOCS Press, Champaign, IL (1993). J. Janick and J.E. Simon (eds), New Crops, John Wiley & Sons, Inc., New York, NY (1993). B.A. Stout, The Handbook of Energy for World Agriculture, Elsevier, Amsterdam (1990). H. Brucher, Useful Plants of Neotropical Origin and their Wild Relatives, Springer-Verlag, Berlin (1989). N.V. Bringi, Non-traditional Oil Seed and Oils of India, Oxford/IBH, New Dehli (1987). F.W. Martin (ed.), CRC Handbook of Tropical Food Crops, CRC Press, Boca Raton, FL (1984). F. Rosengarten, The Book of Edible Nuts, Walker & Co., New York, NY (1984). M. Baumer, Notes on Trees and Shrubs in Arid and Semi-Arid Regions, FAO/UNEP programme ‘Ecological Management of Arid and SemiArid Rangelands in Africa, Near and Middle East’ (EMASAP Phase II), Rome (1983).

274

Biodiesel science and technology

E.A. Weiss, Oilseed Crops, Longman Inc., New York, NY (1983). C.N. Williams, W.Y. Chew and J.H. Rajaratnam, Trees and Field Crops of the Wetter Regions of the Tropics, Longman, London (1980). C. Paquot, Standard Methods for the Analysis of Oils, Fats, and Derivatives, IUPAC Commission on Oils, Fats and Derivatives, Pergamon Press, London (1979). J.G. Vaughan, The Structure and Utilisation of Oil Seeds, Chapman & Hall, London (1976).

6.6

References

[1] L.W. Kleingartner, NuSun sunflower oil: redirection of an industry, in Trends in New Crops and New Uses (J. Janick and A. Whipkey, eds), ASHS Press, Alexandria, VA (2002), pp. 135–8. [2] V. Spitzer, Screening analysis of unknown seed oils, Fett/Lipid 101 (1999) 2–19. [3] P.L. Benitez-Sánchez, M. Léon-Camacho and R. Aparicio, A comprehensive study of hazelnut oil composition with comparisons to other vegetable oils, particulary olive oil, Eur. Food Res. Technol. 218 (2003) 13–19. [4] D.B. Arkcoll and C.R. Clement, Potential new food crops from the Amazon, in New Crops for Food and Industry (G. Wickens, N. Haq and P. Day, eds), Chapman & Hall, London (1989), pp. 150–65. [5] K.S. Tyson, J. Brown and M. Moora, Industrial mustard crops for biodiesel and biopesticides, Proceedings 5th Intl. Biomass Conf. of the Americas, Orlando, FL (17–21 Sept. 2001). [6] J. Tickell, From the Fryer to the Fuel Tank: The Complete Guide to Using Vegetable Oil as an Alternative Fuel, Tickell Energy, Hollywood, CA (2000). [7] P. Kalayasiri, N. Jeyashoke and K. Krisnangkura, Survey of seed oils for use as diesel fuels, J. Am. Oil Chem. Soc. 73 (1996) 471–4. [8] K. Krisnangkura, A simple method for estimation of cetane index of vegetable oil methyl esters, J. Am. Oil Chem. Soc. 63 (1986) 552–3. [9] M. Mittelbach, Diesel fuel derived from vegetable oils. VI: Specifications and quality control of biodiesel, Bioresour. Technol. 56 (1996) 7–11. [10] Official Methods and Recommended Practices of the American Oil Chemists’ Society, AOCS Press, Champaign, IL (1999), Method Cd 1d-92. [11] N.B. Kyriakidis and T. Katsiloulis, Calculation of iodine value from measurements of fatty acid methyl esters of some oils: comparison with the relevant American Oil Chemists Society method, J. Am. Oil Chem. Soc. 77 (2000) 1235–8. [12] R.R. Allen, Determination of unsaturation, J. Am. Oil Chem. Soc. 32 (1955) 671–4. [13] M. Geissler, Biodiesel patterns reflect quality, LC.GC Europe. The Applications Book (July 2008), pp. 44–5. [14] G. Knothe, Structure indices in FA chemistry. How relevant is the iodine value? J. Am. Oil Chem. Soc. 79 (2002) 847–54. [15] P. Bondioli and L. Folegatti, Evaluating the oxidation stability of biodiesel. An experimental contribution, Riv. Ital. Sostanze Grasse 73 (1996) 349–53. [16] H. Prankl, M. Wörgetter and J. Rathbauer, Technical performance of vegetable

Emerging new energy crops for biodiesel production

[17]

[18] [19]

[20]

[21]

[22]

[23] [24] [25] [26]

[27] [28]

[29] [30] [31]

[32]

[33]

[34]

275

oil methyl esters with a high iodine number, Proceedings 4th Intl. Biomass Conf. of the Americas, Oakland, CA (1999), pp. 805–10. C. Paquot, Standard Methods for the Analysis of Oils, Fats and Derivatives, IUPAC Commission on Oils, Fats and Derivatives, Pergamon Press, London (1979), p. 52. M. Mittelbach and C. Remschmidt, Biodiesel – The Comprehensive Handbook, Boersedruck Ges., Vienna (2004). T.W. Ryan III and B. Stapper, Diesel fuel ignition quality as determined in a constant-volume combustion bomb, SAE Technical Paper Series 870586, SAE, Warrendale, PA (1987). A.A. Aradi and T.W. Ryan III, Cetane effect on diesel ignition delay times measured in a constant-volume combustion apparatus, SAE Technical Paper Series 952352; also in Emission Processes and Control Technologies in Diesel Engines, SAE Spec. Publ. SP-1119, SAE, Warrendale, PA (1995), p. 43. G. Knothe, A.C. Matheaus and T.W. Ryan III, Cetane numbers of branched and straight-chain fatty esters determined in an Ignition Quality Tester, Fuel 82 (2003) 971–5. C.E. Goering, A.W. Schwab, M.J. Daugherty, E.H. Pryde and A.J. Reakin, Fuel properties of eleven vegetable oils, Proc. 1981 ASAE Winter Mtg. (Chicago, IL), ASAE, St. Joseph, MI (1981). Y. Ali, M.A. Hanna and S.L. Cuppett, Fuel properties of tallow and soybean oil esters, J. Am. Oil Chem. Soc. 72 (1995) 1557–64. H.Y. Zhang, M.A. Hanna, Y. Ali and L. Nan, Yellow nut-sedge (Cyperus esculentus L.) tuber oil as a fuel, Ind. Crops Prod. 5 (1996) 177–81. N. Ladommatos, M. Parsi and A. Knowles, The effect of fuel cetane improver on diesel pollutant emissions, Fuel 75 (1996) 8–14. G. Knothe, M.O. Bagby and T.W. Ryan III, Cetane numbers of fatty compounds: influence of compound structure and of various potential cetane improvers, SAE Technical Paper Series 971681; also in State of Alternative Fuel Technologies, SAE Publ. SP-1274, SAE, Warrendale, PA (1997), pp. 127–32. G. Knothe, Cetane numbers, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 76–80. J. Van Gerpen, Cetane number testing in biodiesel, in Lipid Fuel and Industrial Products from Renewable Resources (J.S. Cundiff, ed.), Proceedings 3rd Liquid Fuel Conference, Nashville, TN (15–17 Sept. 1996), pp. 197–206. http://www.me.iastate.edu/biodiesel F.J. Liotta Jr, A peroxide based cetane improvement additive with favourable blending properties, SAE Paper No. 932767 (1993). G. Knothe, M.O. Bagby and W. Thomas III, The influence of various oxygenated compounds on the cetane numbers of fatty acids and esters, in Liquid Fuel and Industrial Products from Renewable Resources (J.S. Cundiff, ed.), Proceedings 3rd Liquid Fuel Conference, Nashville, TN (15–17 Sept. 1996), pp. 54–8. G. Yildiz, R.L. Wehling and S.L. Cuppett, Comparison of four analytical methods for the determination of peroxide value in oxidized soybean oils, J. Am. Oil Chem. Soc. 80 (2003) 103–7. G. Knothe, M.O. Bagby and T.W. Ryan III, Precombustion of fatty acids and esters of biodiesel. A possible explanation for differing cetane numbers, J. Am. Oil Chem. Soc. 75 (1998) 1007–13. B. Clark, A. Wang, J. Wilson, S.O. Salley and K.Y.S. Ng, Catalytic effects

276

[35]

[36]

[37]

[38] [39]

[40] [41] [42]

[43] [44] [45] [46]

[47]

[48]

[49]

[50]

[51] [52]

Biodiesel science and technology of transition metals on the oxidative stability of various biodiesels, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). D. Firestone (ed.), Official Methods and Recommended Practices of the American Oil Chemists’ Society, 4th edn, AOCS Press, Champaign, IL (1992), Oxidative stability index (OSI), Method Cd 12b-92. M. Roche, C. Dufour, N. Mora and O. Dangles, Antioxidant activity of olive phenols: mechanistic investigation of oxidation products by mass spectroscopy, Org. Biomol. Chem. 3 (2005) 423–30. K.M. Schaich, Lipid oxidation: theoretical aspects, in: Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 1 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 269–355. T.A. Isbell, T.P. Abbott and K.D. Carlson, Oxidation stability index of vegetable oils in binary mixtures with meadowfoam oil, Ind. Crops Prod. 9 (1999) 115–23. B.W. Matthäus, Determination of the oxidative stability of vegetable oils by Rancimat and conductivity and chemiluminescence measurements, J. Am. Oil Chem. Soc. 73 (1996) 1039–43. E.N. Frankel, Lipid Oxidation, The Oily Press, Dundee (1998). Y.-H. Chu and Y.-L. Kung, A study on vegetable oil blends, Food Chem. 62(2) (1998) 191–5. A. Schönemann, W. Frenzel, A. Unger and E. Kenndler, An investigation of the fatty acid composition of new and aged tung oil, Stud. Conserv. 51 (2006) 99–110. R.L. Feller, Accelerated Ageing: Photochemical and Thermal Aspects, The Getty Conservation Institute, Marina del Rey, CA (1994). J.D.J. van den Berg, Analytical Chemical Studies on Traditional Linseed Oil Paints, Ph.D. Thesis, University of Amsterdam (2002). M. Lazzari and O. Chiantore, Drying and oxidative degradation of linseed oil, Polym. Degr. Stabil. 65 (1999) 303–13. J.D.J. van den Berg, K.J. van den Berg and J.J. Boon, Identification of non-crosslinked components in methanolic extracts of cured and aged linseed oil-based paint films using gas chromatography-mass spectrometry, J. Chromatogr. A950 (2002) 195–211. E. Gaydou, J. Miralles and M. Rasoazanakolona, Analysis on conjugated octadecatrienoic acids in Momordica balsamina seed oil by GLC and 13C NMR spectroscopy, J. Am. Oil Chem. Soc. 64(7) (1987) 997–1000. D.G.B. Boocock, Single-phase process for production of fatty acid methyl esters from mixtures of triglycerides and fatty acids, PCT Int. Publ. No. WO 2001/012581 (22 Feb. 2001). A. Center, E. Johnson, A. Nady, C. Wood and C.A. Fleisher (to Cornell Research Foundation Inc.), Continuous transesterification process, PCT Int. Publ. No. WO 2003/087279 A2 (23 Oct. 2003). M.J. Haas, K.M. Scott, P.J. Michalski and S. Runyon (to USDA/Runyon Industries), Lipid rich compositions, production of lipid rich compositions, production of fatty acid alkyl esters from heterogeneous lipid mixtures, PCT Int. Publ. No. WO 2003/0598847 (24 July 2003). E. Schneller and V. Gatto, Improving the quality of biodiesel through the use of antioxidants and metal chelators, Biodiesel Mag. 5(2) (2008) 180–4. A. Ingendoh, Improvement in storage stability of biodiesel with Baynox® antioxidants, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007).

Emerging new energy crops for biodiesel production

277

[53] E. Schneller and V. Gatto, Stabilizing biodiesel blends from multiple feedstocks, Biodiesel Mag. 5(4) (2008) 128–32. [54] L. Jeromin, E. Peukert and G. Wollmann (to Henkel), Verfahren zur Vorveresterung freier Fettsäuren in Rohfetten und/oder -ölen, Germ. Pat. DE 3,501,761 A1 (21 Jan. 1985). [55] D.P. Geller and J.W. Goodrum, Effects of specific fatty acid methyl esters on diesel fuel lubricity, Fuel 83 (2004) 2351–6. [56] M.M. Azam, A. Waris and N.M. Nahar, Prospects and potential of fatty acid methyl esters of some non-traditional seed oils for use as biodiesel in India, Biomass Bioen. 29 (2005) 293–302. [57] H. Ako, N. Kong and A. Brown, Fatty acid profiles of kukui nut oils over time and from different sources, Ind. Crops Prod. 22 (2005) 169–74. [58] K.M. Hosamani and R.S. Pattanashettar, Mappia foetida seed oil: a rich source of oil and moderate source of novel 3-keto-octadec-cis-15-enoic acid and its possible industrial utilization, Ind. Crops Prod. 22 (2005) 135–9. [59] O.Y. Yong and J. Salimon, Characteristics of Elateriospermum tapos seed oil as a new source of oilseed, Ind. Crops Prod. 24 (2006) 146–51. [60] H. Traitler, H.J. Wille and A. Studer, Fractionation of blackcurrant seed oil, J. Am. Oil Chem. Soc. 65(5) (1988) 755–60. [61] D. Firestone, ed., Official Methods and Recommended Practices of the American Oil Chemists Society, 4th edn, AOCS Press, Champaign, IL (1992), Additions and Revisions, Method Cd 18–90. [62] I. Debruyne, Biodiesel blends based on an optimal choice of raw materials. Matching costs with high quality standards, 8th AOCS Practical Short Course on Biodiesel Processing, Chemistry and Production, Vienna (4–5 Nov. 2007). [63] K.G. Berger, Oils from underutilised palms and forest products, in Technological Advances in Improved and Alternative Sources of Lipids (B.S. Kamel and Y. Kakuda, eds), Chapman & Hall, London (1994), pp. 209–33. [64] B.A. Stout, The Handbook of Energy for World Agriculture, Elsevier, Amsterdam (1990). [65] J. Bruinsma (ed.), World Agriculture Toward 2015/30, an FAO Perspective, FAO (UN), Rome (2003). [66] J.P. Kapur, S.D. Bhasin and K.C. Mathur, Oilseeds for food and industrial applications, Chem. Age India 33 (1982) 475–82. [67] S. Kaul, A. Kumar, A.K. Bhatnagar, H.B. Goyal and A.K. Gupta, Biodiesel a clean and sustainable fuel for the future. Scientific strategies for production of non-edible vegetable oils for use as biofuels, All India Seminar on National Policy on Non-edible Oils as Biofuels, SUTRA, IISc, Bangalore (2003). [68] D.H. Chowhury, S.N. Mukerji, J.S. Aggarwal and L.C. Verman, Indian vegetable fuel oils for diesel engines, Gas Oil Power 37 (1942) 80–5. [69] M.H. Chakrabarti and R. Ahmad, Transesterification studies on castor oil as a first step towards its use in biodiesel production, Pak. J. Bot. 40 (2008) 1153–7. [70] J. Parikh, Biodiesel development in India: appraisal and tasks, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [71] B.K. Barnwal and M.P. Sharma, Prospects of biodiesel production from vegetable oils in India, Renew. Sustain. En. Rev. 9 (2005) 363–78. [72] S.K. Karmee and A. Chadha, Preparation of biodiesel from crude oil of Pongamia pinnata, Bioresour. Technol. 96 (2005) 1425–9. [73] S.K. Karmee, P. Mahesh, R. Ravi and A. Chadha, Kinetic study of the base-

278

[74]

[75] [76] [77]

[78] [79]

[80] [81] [82]

[83] [84]

[85] [86] [87] [88] [89] [90] [91]

[92]

[93]

Biodiesel science and technology catalyzed transesterification of monoglycerides from Pongamia oil, J. Am. Oil Chem. Soc. 81 (2004) 425–30. S.K. Karmee, D. Chandna, R. Ravi and A. Chadha, Kinetics of base-catalyzed transesterification of triglycerides from Pongamia oil, J. Am. Oil Chem. Soc. 83 (2006) 873–7. V. Vivek and A.K. Gupta, Biodiesel production from Karanja oil, J. Sci. Ind. Res. 63 (2004) 39–47. H. Raheman and A.G. Phadatare, Diesel engine emissions and performance from blends of karanja methyl ester and diesel, Biomass Bioen. 27 (2004) 393–7. P. Mahanta, S.C. Mishra and Y.S. Kushwah, An experimental study of Pongamia pinnata L. oil as a diesel substitute, Proc. Inst. Mech. Engng. Part A. J. Power Energy 220 (2006) 803–8. K. Pramanik, Properties and use of Jatropha curcas oil and diesel fuel blends in compression ignition engine, Renew. En. 28 (2003) 239–48. M. Senthil Kumar, A. Ramesh and B. Nagalingam, An experimental comparison of methods to use methanol and Jatropha oil in a compression ignition engine, Biomass Bioen. 25 (2003) 309–18. K. Becker and G. Francis, Biodiesel from Jatropha Plantations on Degraded Land. A Brief Technical Report, University of Hohenheim, Stuttgart (2002). S. Shah, S. Sharma and M.N. Gupta, Biodiesel preparation by lipase-catalyzed transesterification of Jatropha oil, Energy Fuels 18 (2004) 154–9. J.-D. Choi, J.-Y. Park, S.-C. Park and J.-S. Lee, Production and characterization of biodiesel made from Jatropha oil, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). S.V. Ghadge and H. Raheman, Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids, Biomass Bioen. 28 (2005) 601–5. S.V. Ghadge and H. Raheman, Process optimization for biodiesel production from mahua (Madhuca indica) oil using response surface methodology, Bioresour. Technol. 97 (2006) 379–84. P.R. Aare, Production of biodiesel from combination of corn (maize) and other feedstocks, U.S. Pat. Appl. 2007/099278 A1 (3 May 2007). A.S. Ramadhas, S. Jayaraj and C. Muraleedharan, Biodiesel production from high FFA rubber seed oil, Fuel 84 (2005) 335–40. G.D.P.S. Augustus and G.J. Seiler, Promising oil producing seed species of Western Ghats (Tamil Nadu, India), Ind. Crops Prod. 13 (2001) 93–100. D.R. Bhumbla and A. Khare, Estimate of Wasteland in India, Society for Promotion of Wastelands Development, New Delhi (1984). D. Konwer and K. Barauah, Refining of the crude oil obtained from Mesua ferrea L. seeds, Chem. Ind. (1984) 413–14. B.K. De and D.K. Bhattacharyya, Biodiesel from minor vegetable oils like karanja oil and nahor oil, Fett/Lipid 101 (1999) 404–6. Y. Kakuda, F. Jahaniaval, M.F. Marcone, L. Montevirgen, Q. Montevirgen and J. Umali, Characterization of pili nut (Canarium ovatum) oil: fatty acid and triacylglycerol composition and physicochemical properties, J. Am. Oil Chem. Soc. 77 (2000) 991–6. K.D. Carlson and S.P. Chang, Chemical epoxidation of a natural unsaturated epoxy seed oil from Vernonia galamensis and a look at epoxy oil markets, J. Am. Oil Chem. Soc. 62 (1985) 934–9. T. Baye, H.C. Becker, S. von Witzke-Ehbrecht, Vernonia galamensis, a natural

Emerging new energy crops for biodiesel production

[94]

[95]

[96] [97]

[98] [99]

[100]

[101] [102] [103]

[104] [105] [106] [107]

[108] [109] [110]

[111]

[112]

279

source of epoxy oil: variation in fatty acid composition of seed and leaf lipids, Ind. Crops Prod. 21 (2005) 257–61. J.W. Goodrum and D.P. Geller, Influence of fatty acid methyl esters from hydroxylated vegetable oils on diesel fuel lubricity, Bioresour. Technol. 96 (2005) 851–5. S.C. Cermak, K.B. Brandon and T.A. Isbell, Synthesis and physical properties of estolides from lesquerella and castor fatty acid esters, Ind. Crops Prod. 23 (2006) 54–64. S.A. Graham, Cuphea: a new plant source of medium-chain fatty acids, Crit. Rev. Food Sci. Nutr. 28 (1989) 139–73. S.J. Knapp, Modifying the seed storage lipids of Cuphea: a source of mediumchain triglycerides, in: Seed Oils for the Future (S.L. MacKenzie and D.C. Taylor, eds), AOCS Press, Champaign, IL (1992), pp. 142–54. D.P. Geller, J.W. Goodrum and S.J. Knapp, Fuel properties of oil from genetically altered Cuphea viscosissima, Ind. Crops Prod. 9 (1999) 85–91. R. Kleiman, C.R. Smith, S.G. Yates and Q. Jones, Search for new industrial oils. XII. Fifty-eight Euphorbiaceae oils, including one rich in vernolic acid, J. Am. Oil Chem. Soc. 43 (1965) 169–72. L.G. Angelini, E. Moscheni, G. Colonna, P. Belloni and E. Bonari, Variation in agronomic characteristics and seed oil composition of new oilseed crops in central Italy, Ind. Crops Prod. 6 (1997) 313–23. S.J. Knapp and J.M. Crane, Fatty acid diversity of Section Inflexae Limnanthes (meadowfoam), Ind. Crops Prod. 4 (1995) 219–27. C.R. Smith, M.O. Bagby, T.K. Miwa, R.L. Lohmar and I.A. Wolff, Unique fatty acids from Limnanthes douglasii seed oil, J. Org. Chem. 25 (1960) 1770–4. M.O. Bagby, C.R. Smith, T.K. Miwa, R.L. Lohmar and I.A. Wolff, A unique fatty acid from Limnanthes douglasii seed oil: the C-22 diene, J. Org. Chem. 26 (1961) 1261–5. A. Mohamed, H. Bhardwaj, A. Hamama and C. Webber III, Chemical composition of kenaf (Hibiscus cannabinus L.) seed oil, Ind. Crops Prod. 4 (1995) 157–65. K.M. Hosamani and R.S. Pattanashettar, Occurrence of unusual fatty acids in Ficus benghalensis seed oil, Ind. Crops Prod. 18 (2003) 139–43. Council of Scientific and Industrial Research, The Wealth of India, CSIR, New Dehli (1948–76), 11 vols. R. Morrone, B. Fallico, S. Campisi and E. Maccarone, Prodotti di interesse alimentare e farmaceutico dai semi di Silybum marianum (Cardo mariano), in Proc. 2nd Congress Naz. Chim. Alimenti, Giardini-Naxos (1995), pp. 1211–18. P. Eganathan, H.M. SR Subramanian, R. Latha and C. Srinivasa Rao, Oil analysis in seeds of Salicornia brachiata, Ind. Crops Prod. 23 (2006) 177–9. P.D. Desai, A.M. Dave and S. Devi, Alcoholysis of Salicornia oil using free and covalently bound lipase onto chitosan beads, Food Chem. 95 (2006) 193–9. C. Borch-Jensen, B. Jensen, K. Mathiasen and J. Mollerup, Analysis of seed oil from Ricinus communis and Dimorphoteca pluvialis by gas and supercritical fluid chromatography, J. Am. Oil Chem. Soc. 74 (1997) 277–84. W.J. Grüneberg, F.D. Goffman and L. Velasco, Characterization of yam bean (Pachyrhizus spp.) seeds as potential sources of high palmitic acid oil, J. Am. Oil Chem. Soc. 76 (1999) 1309–12. F.A. Austenfeld, Nutrient reserves of Salicornia europaea seeds, Physiol. Plant. 68 (1986) 446–50.

280

Biodiesel science and technology

[113] E.P. Glenn, J.J. Brown and J.W. O’Leary, Irrigating crops with seawater, Sci. Am. 279 (1998) 76–81. [114] K.M. Hosamani and R.M. Sattigeri, Analysis of Cassia marginata and Cassia corymbosa seed oils: an approach for the industrial utilization, Ind. Crops Prod. 17 (2002) 57–60. [115] Y. Basiron, Palm oil production through sustainable plantations, Eur. J. Lipid Sci. Technol. 109 (2007) 289–95. [116] D. Mistry, Why palm needs biofuel demand for its long term success, Paper presented at 2nd Intl. Palm Oil Trade Fair & Seminar, Kuala Lumpur (24–26 Aug. 2008). [117] Available at: http://www.fao.org/waicent/portal/statistics_en.asp [118] Philippine Department of Energy, Philippine Energy Plan 2002–2011, Manila (2002). [119] Philippine Department of Environment and Natural Resources, Implementing Rules and Regulations of RA8749 – Clean Air Act of 1999, Manila (2000). [120] R.R. Tan, A.B. Culaba and M.R.I. Purvis, Carbon balance implications of coconut biodiesel utilization in the Philippine automotive transport sector, Biomass Bioen. 26 (2004) 579–85. [121] R. Tan, A.B. Culaba and M.R.I. Purvis, Application of possibility theory in the life-cycle inventory assessment of biofuels, Int. J. En. Res. 26 (2002) 737–45. [122] J. Sheehan, V. Camobreco, J. Duffield, M. Graboski and H. Shapouri, Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus, Final report NREL/SR-580-24089, NREL, Golden, CO (1998). [123] M.Q. Wang, GREET 1.-5 – Transportation Fuel-Cycle Model, Final report ANL/ ESD-39, Argonne National Laboratory, Argonne, IL (1999). [124] T. Beer, T. Grant, D. Williams and H. Watson, Fuel-cycle greenhouse gas emissions from alternative fuels in Australian heavy vehicles, Atm. Environm. 36 (2002) 753–63. [125] M. Kaltschmitt, G.A. Reinhardt and T. Stelzer, Life cycle analysis of biofuels under different environmental aspects, Biomass Bioen. 12 (1997) 121–34. [126] J.G. Vaughan, The Structure and Utilisation of Oil Seeds, Chapman & Hall, London (1976). [127] M. Jure, I. Mierina, R. Serzane, M. Strele, I. Vanaga and T. Paeglis, Synthesis and properties of biodiesel and its additives from hempseed oil, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [128] B.D. Oomah, M. Busson, D.V. Godfrey and J.C.G. Drover, Characteristics of hemp (Cannabis sativa L.) seed oil, Food Chem. 76 (2002) 33–43. [129] F. Anwar, S. Latif and M. Ashraf, Analytical characterization of hemp (Cannabis sativa) seed oil from different agro-ecological zones in Pakistan, J. Am. Oil Chem. Soc. 83 (2006) 323–9. [130] L. Nan, Z.C. Liang, R.X. Wan and J.X. Ma, Use of yellow nut-sedge oil as a substitute for diesel fuel, ASAE Paper No. MCR 84-108, St. Joseph, MI (1984). [131] Anon., Brazil uses vegetable oil for diesel fuel, Chem. Metall. Engng. 50 (1943) 225. [132] M.J. Balick, Amazonian oil palms of promise: a survey, Econ. Bot. 33 (1979) 11–28. [133] F.A. Wandeck and P.G. Justo, Macauba, fonte energetica e insumo industrial, Vida Industrial (São Paulo) (Oct. 1982), pp. 33–7.

Emerging new energy crops for biodiesel production

281

[134] D.B. Arkcoll and J.P.L. Aguiar, Peach palm (Bactris gasipaes H.B.K.), a new source of vegetable oil from the wet tropics, J. Sci. Food Agric. 35 (1984) 520–6. [135] G. Pacheco Borges, Use of Brazilian vegetable oils as fuel, Anais Assoc. Quím. Brasil 3 (1944) 206–9. [136] G.N. Da Rocha Filho, D. Brodzki and G. Djéga-Mariadassou, Formation of alkanes, alkylcycloalkanes and alkylbenzenes during the catalytic hydrocracking of vegetable oils, Fuel 72 (1993) 543–9. [137] Fundação Centro Tecnológico de Minas Gerais (CETEC Foundation), R&D in Biodiesel Production: Past and Present, Technical Report (2005). [138] Anon., Piquia – potential source of vegetable oil for an oil-starving world, Ec. Botany 11(3) (1957) 187–207. [139] C.N. Williams, W.Y. Chew and J.H. Rajaratram, Trees and Field Crops of the Wetter Regions of the Tropics, Longman, New York, NY (1979). [140] D. Arkcoll, New crops from Brazil, in Advances in New Crops (J. Janick and J.E. Simon, eds), Timber Press, Portland, OR (1990), pp. 367–71. [141] D. Bereau, B. Benjelloun-Mlayah, J. Banoub and R. Bravo, FA and unsaponifiable composition of five Amazonian palm kernel oils, J. Am. Oil Chem. Soc. 80 (2003) 49–53. [142] A.L. Markman, L.N. Andrianova, B.K. Kruptsov, I.U. Yusupova, L.M. Yukushina and M.E. Konchalovskaya, Triacylglycerols of oiticica oil, Khim. Prirodn. Soedin. (3) (1980) 316–19; J. Nat. Compds. 16 (1980) 229–32. [143] J.F. Toro-Vazquez, M.A. Charó-Alonso, and F. Pérez-Briceño, Fatty acid composition and its relationship with physiochemical properties of pecan (Carya illinoensis) oil, J. Am. Oil Chem. Soc. 76 (1999) 957–65. [144] A.C. Pinto, L.L.N. Guarieiro, M.J.C. Rezende, N.M. Ribeiro, E.A. Torres, W.A. Lopes, P.A.P. Pereira and J.B. Andrade, Biodiesel: an overview, J. Braz. Chem. Soc. 16 (2005) 1313–30. [145] M.E. Carreras, E. Fuentes and C.A. Guzman, Chemotaxonomy of seed lipids of Cucurbitaceae grown in Argentina, Biochem. System. Ecol. 17 (1989) 287–91. [146] I.C.P. Fortes and P.J. Baugh, Study of analytical on-line pyrolysis of oils from Macauba fruit (Acrocomia sclerocarpa M.) via GC-MS, J. Braz. Chem. Soc. 10 (1999) 469–77. [147] F.R. Abreu, D.G. Lima, E.H. Hamú, C. Wolf and P.A.Z. Suarez, Utilization of metal complexes as catalysts in the transesterification of Brazilian vegetable oils with different alcohols, J. Mol. Catal. A: Chem. 209 (2004) 29–33. [148] S.D. Segall, W.E. Artz, D.S. Raslan, V.P. Ferraz and J.A. Takahashi, Triacylglycerol analysis of pequi (Caryocar brasiliensis Camb.) oil by electrospray and tandem mass spectrometry, J. Sci. Food Agric. 86 (2006) 445–52. [149] M.L.S. Albuquerque, I. Guedes, P. Alcantara, S.G.C. Moreira, N.M. Barbosa Neto, D.S. Correa and S.C. Zilio, Characterization of buriti (Mauritia flexuosa L.) oil by absorption and emission spectroscopies, J. Braz. Chem. Soc. 16 (2005) 1113–17. [150] F. Ozdemir and A. Topuz, Changes in dry matter, oil content and fatty acids composition of avocado during harvesting time and post-harvesting ripening period, Food Chem. 86 (2004) 79–83. [151] C.G. Cavaletto, 1983 Yearbook of the California Macadamia Society, California Macadamia Society, Fallbrook, CA (1983). [152] A. Kaijser, P. Dutta and G. Savage, Oxidative stability and lipid composition of macadamia nuts grown in New Zealand, Food Chem. 71 (2000) 67–70.

282

Biodiesel science and technology

[ 153] Liberty Vegetable Oil Company, Santa Fé Springs, CA. [154] P.A. Hiane, D. Bogo, M.I.L. Ramos and M.M. Ramos Filho, Provitamin A carotenoids and fatty acid composition of the fruit and flour of bacuri (Scheelea phalerata Mart.), Cienc. Tecnol. Aliment. (Campinas) 23 (2003) 206–9. [155] R.R. Laethers and A.H. Scragg, The effect of different temperatures on the growth, lipid content and fatty acid composition of Theobroma cacao cell suspension cultures, Plant Sci. 62 (1989) 217–27. [156] A.C. Gathman and W.P. Bernis, Heritability of fatty acid composition of buffalo gourd seed oil, J. Heredity 74 (1983) 199–200. [157] C. Bertoli, L.B. Fay, M. Stancanelli, D. Gumy and P. Lambelet, Characterization of Chilean hazelnut (Gevuina avellana Mol) seed oil, J. Am. Oil Chem. Soc. 75 (1998) 1037–40. [158] P.B. Price and J.G. Parsons, Lipids of seven cereal grains, J. Am. Oil Chem. Soc. 52 (1975) 490–3. [159] M. Venkatachalam and S.K. Sathe, Chemical composition of selected edible nut seeds, J. Agric. Food Chem. 54 (2006) 4705–14. [160] E.W. Ecky and L.P. Lawrence, Vegetable Fats and Oils, Reinhold Publ. Corp., New York, NY (1954). [161] G.P. Savage, P.C. Dutta and D.L. McNeil, Fatty acid and tocopherol contents and oxidative contents and oxidative stability of walnut oils, J. Am. Oil Chem. Soc. 76 (1999) 1059–63. [162] R. Oliveira, M. Rodriguez and M.G. Bernardo-Gil, Characterization and supercritical carbon dioxide extraction of walnut oil, J. Am. Oil Chem. Soc. 79 (2002) 225–30. [163] F. Shahidi and H. Miraliakbari, Tree nut oils, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 3 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 175–93. [164] M.D. Guillén, A. Ruiz, N. Cabo, R. Chirinos and G. Pascual, Characterization of Sacha inchi (Plukenetia volubilis L.) oil by FTIR spectroscopy and 1H NMR. Comparison with linseed oil, J. Am. Oil Chem. Soc. 80 (2003) 755–62. [165] L.P. Ramos, Biodiesel in South America, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [166] E.N. Onyeike and G.N. Acheru, Chemical composition of selected Nigerian oil seeds and physicochemical properties of the oil extracts, Food Chem. 77 (2002) 431–7. [167] Y.M.H. Younis, S. Ghirmay and S.S. Al-Shihry, African Cucurbita pepo L.: properties of seed and variability in fatty acid composition of seed oil, Phytochem. 54 (2000) 71–5. [168] J.T. Barminas, H.M. Maina, S. Tahir, D. Kubmarawa and K. Tsware, A preliminary investigation into the biofuel characteristics of tigernut (Cyperus esculentus) oil, Bioresour. Technol. 79 (2001) 87–9. [169] B.I. Ugheoke, D.O. Patrick, H.M. Kefas and E.O. Onche, Determination of optimal catalyst concentration for maximum biodiesel yield from Tigernut (Cyperus esculentus) oil, Leonardo J. Sci. (10) (2007) 131–6. [170] J.A. Duke, Handbook of Energy Crops, Purdue University Center for New Crops and Plant Products, West Lafayette, IN (2003); http://www.hort.purdue.edu/ newcrop. [171] A.M. Nour, R. Ahmed and A. Abdel-Gayoum, A chemical study of Balanites aegyptiaca L. (Lalob) fruits grown in Sudan, J. Sci. Food Agric. 36 (2006) 1254–8.

Emerging new energy crops for biodiesel production

283

[172] E.A. Abdel-Rahim, S.S. El-Saadany and M.M. Wasif, Chemical and physical studies on Balanites aegyptiaca oil, Grases y Aceites 37(2) (1986) 81–5. [173] B. Chinsinga, Reclaiming policy space: lessons from Malawi’s fertiliser programme, future agricultures, Institute of Development Studies, Brighton (2007). [174] Matthew 17:20, … if ye have faith as a grain of mustard seed … nothing shall be impossible unto you. [175] S.R. Schill, Making pennycress pay off, Biodiesel Mag. 5(2) (2008) 77–82. [176] R.A. Holser and R.H. O’Kuru, Transesterified milkweed (Asclepias) seed oil as a biodiesel fuel, Fuel 85 (2006) 2106–10. [177] C. Anderson, Count on canola for your biodiesel, Biodiesel Mag. 5(2) (2008) 186–90. [178] G. Rakow and A. Getinet, Brassica carinata: an oilseed crop for Canada, in Proc. ISHS Acta Horticulturae 459 (G. Thomas and A.A. Monteiro, eds), Intl. Symp. Brassica 97, Xth Crucifer Genetics Workshop, Rennes (1998). [179] European Technology Platform, Plants for the Future (2025: A European Vision for Plant Genomics and Biotechnology), European Commission, Brussels (2005). [180] S.J. O’Mahony and N.K. Tovey, A life cycle assessment of potential biodiesel crops in the UK, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [181] F. Hirsinger, Oilseed Crops: Present Situation and Future Developments for Oleochemical Application, Comm. Eur. Communities, Brussels (1990), EUR 11583. [182] J. Janick (ed.), Progress in New Crops, Proc. 3rd Nat. Symp. New Crops, ASHS Press, Alexandria, VA (1996). [183] J. Smartt and N. Haq (eds), Domestication, Production and Utilization of New Crops, Centre for Underutilized Crops, Southampton University (1997). [184] R.J. Roseberg, Underexploited temperate, industrial and fiber crops, in Progress in New Crops (J. Janick, ed.), ASHS Press, Alexandria, VA (1996), pp. 60–84. [185] K. Brahim, D.K. Stumpf, D.T. Ray and D.A. Dierig, Lesquerella fendleri seed oil content and composition: harvest date and plant population effects, Ind. Crops Prod. 5 (1996) 245–52. [186] E.L. Ploschuk, G. Cerdeiras, L. Windauer, D.A. Dierig and D.A. Ravetta, Development of alternative Lesquerella species in Patagonia (Argentina): potential of Lesquerella angustifolia, Ind. Crops Prod. 18 (2003) 1–6. [187] S.A. Graham, F. Hirsinger and G. Röbbelen, Fatty acids of Cuphea (Lythraceae) seed lipids and their systematic significance, Amer. J. Bot. 68 (1981) 908–17. [188] S.A. Graham and R. Kleiman, Fatty acid composition in Cuphea seed oils from Brazil and Nicaragua, J. Am. Oil Chem. Soc. 62 (1985) 81–2. [189] A.E. Thompson, D.A. Dierig and R. Kleiman, Variation in Vernonia galamensis flowering characteristics, seed oil and vernolic acid contents, Ind. Crops Prod. 3 (1994) 175–83. [190] IENICA Summary Report for the European Union (2000). [191] A. Fröhlich and B. Rice, Evaluation of Camelina sativa oil as a feedstock for biodiesel production, Ind. Crops Prod. 21 (2005) 25–31. [192] A. Büchsenschütz-Nothdurft, A. Schuster and W. Friedt, Breeding for modified fatty acid composition via experimental mutagenesis in Camelina sativa (L.) Crtz., Ind. Crops Prod. 7 (1998) 291–5. [193] J. Zubr, Oil-seed crop: Camelina sativa, Ind. Crops Prod. 6 (1997) 113–19. [194] R. Mansfeld, Verzeichnis landwirtschaftlicher und gärtnerischer Kulturpflanzen, Springer-Verlag, Berlin (1986), pp. 281–4.

284

Biodiesel science and technology

[195] A. Bernardo, R. Howard-Hildige, A. O’Connell, R. Nichol, J. Ryan, B. Rice, E. Roche and J.J. Leahy, Camelina oil as a fuel for diesel transport engines, Ind. Crops Prod. 17 (2003) 191–7. [196] B. Rice, Promotion of the Use of Vegetable Oil as a Diesel Engine Fuel Extender/ Replacement in Ireland. Altener Contract No. XVII/4, 1030/93-12 (1995). [197] L. Lazzeri, M. Errani, O. Leoni and G. Venturi, Eruca sativa spp. oleifera: a new non-food crop, Ind. Crops Prod. 20 (2004) 67–73. [198] B. Uzun, C. Arslan, M. Karhan and C. Toker, Fat and fatty acids of white lupin (Lupinus albus L.) in comparison to sesame (Sesamum indicam L.), Food Chem. 102 (2007) 45–9. [199] M.J. Pascual-Villalobos, G. Röbbelen and E. Correal, Production and evaluation of indehiscent mutant genotypes in Euphorbiae lagascae, Ind. Crops Prod. 3 (1994) 129–43. [200] M. Cardone, M. Mazzoncini, S. Menini, V. Rocco, A. Senatore, M. Seggiani and S. Vitolo, Brassica carinata as an alternative crop for the production of biodiesel in Italy: agronomic evaluation, fuel production by transesterification and characterization, Biomass Bioen. 25 (2003) 623–36. [201] A. Bouaid, Y. Diaz, M. Martínez and J. Aracil, Pilot plant studies of biodiesel production using Brassica carinata as raw material, Catal. Today 106 (2005) 193–6. [202] H.G. Breemhaar and A. Bouman, Harvesting and cleaning Euphorbia lagascae, a new arable oilseed crop for industrial application, Ind. Crops Prod. 4 (1995) 173–8. [203] D.M. Peterson and D.F. Wood, Composition and structure of high-oil oat, J. Cereal Sci. 26 (1997) 121–8. [204] J.B. Holland, K.J. Frey and E.G. Hammond, Correlated responses of fatty acid composition grain quality and agronomic traits to nine cycles of recurrent selection for increased oil content in oat, Euphytica 122 (2001) 69–79. [205] F. Jahaniaval, Y. Kakuda and M.F. Marcone, Fatty acid and triacylglycerol compositions of seed oils of five Amaranthus accessions and their comparison to other oils, J. Am. Oil Chem. Soc. 77 (2000) 847–52.

7

Transesterification processes for biodiesel production from oils and fats

Abstract: Fatty acid alkyl esters may be manufactured by transesterification of triglycerides, which is essentially an equilibrium reaction of various consecutive, reversible reactions. Process variables of (catalytic) transesterification of triglycerides with alcohols, such as reaction temperature, nature of the alcohol, molar ratio of alcohol to oil, catalyst type and concentration, purity of reactants, and mixing intensity are critically evaluated in relation to product yield. Various process intensification methods are described, which take advantage of microwaves, ultrasonics, supercritical fluids, dynamic turbulence or co-solvents. The benefits of insitu transesterification are also considered. Production of alkyl esters from vegetable oils via non-catalytic reactions also has been evaluated. Key words: Transesterification, vegetable oils and animal fats, process variables, process intensification, in-situ transesterification.

7.1

Introduction

Ester formation constitutes one of the most important classes of reactions in value-added processing of animal fats and vegetable oils. Typical schemes for ester formation include:

ROH + R¢COOH Æ R¢COOR + H2O  



ROH + R¢COOR≤ Æ R¢COOR + R≤OH  

esterification

7.1

alcoholysis

7.2

RCOOR¢ + R≤COOR≤¢ Æ RCOOR≤¢ + R≤COOR¢ transesterification 7.3

RCOOR¢ + R≤COOH Æ RCOOH + R≤COOR¢  acidolysis

7.4

Commercially, fatty acid alkyl esters (FAAEs) are manufactured either by direct esterification of fatty acids or by alcoholysis (also called transesterification) of triglycerides (TGs). Esterification is carried out batchwise at 473–573 K under pressure; water of reaction has to be removed continuously in order to obtain high yields. Esterification can also be carried out continuously in a countercurrent reaction column using a superheated alcohol [1]. However, the predominant process for the manufacture of FAAEs is transesterification of TGs with alcohol at reflux temperature and atmospheric pressure in the presence of a catalyst. 285

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Transesterification of vegetable oils and animal fats is an equilibrium reaction consisting of a number of consecutive, reversible reactions in which a triglyceride is converted stepwise to diglyceride (DG), monoglyceride (MG) and finally glycerol (GL), as follows: Triglyceride (TG) + ROH ´ Diglyceride (DG) + R¢COOR

7.5

Diglyceride (DG) + ROH ´ Monoglyceride (MG) + R≤COOR 7.6 Monoglyceride (MG) + ROH ´ Glycerol (GL) + R≤¢COOR

7.7

The overall reaction is therefore: R ¢COOCH 2 CH 2 OH | | ææ ææ Æ CHOH + R ¢¢C COOCH + 3 ROH ¨ | | R ¢¢¢COOCH 2 CH 2 OH TG

GL

R ¢C COOR R ¢¢C COOR

7.8

R ¢¢¢C COOR

Alkyl esters (Biodiesel)

Generally speaking, there are two methods of transesterification reaction, namely with or without a catalyst. After (catalytic) transesterification of triglycerides, the products are a mixture of esters, alcohol, (catalyst), tri-, diand monoglycerides, glycerol (by-product) and salts. Transesterification does not alter the fatty acid composition of the feedstocks. Consequently, biodiesel reflects the composition of the vegetable oil under study, specifically the fatty acid profile. Intensification between oils can provide a means of varying the fatty acid structure of the base vegetable oil. For example, a broader spectrum of possible biodiesels has been produced by interesterification/ transesterification between coconut/canola and peanut/canola oil mixes [2]. Traditionally, thermal transesterification of triglycerides requires a multiple step process with one or more batch reactors. Initially, TG and alcohol form two immiscible liquid phases. As the reaction proceeds, two separate liquid phases form, one containing the newly formed FAAEs and the other glycerol, with the excess alcohol, catalyst and feed oil being dispersed into both phases. Even the most efficient of the traditional processes requires several hours to process each batch of feed. Additionally, serious problems arise in the separation steps. Significant quantities of glycerol left in the alkyl esters diminish the quality of the diesel fuel and likewise contaminated glycerol also loses much of its value compared to pure uncontaminated glycerol. It should be stressed that the methyl esters derived from methanolysis are not biodiesel until the proper specifications are met. Excess alcohol must be recycled and the unused catalyst typically must be neutralised. Traditionally, the separation procedures necessary to adequately clean the two product streams produce large quantities of wastewater thereby creating additional process complexity and cost. Alternatively, particulate and/or adsorbent

Transesterification processes for biodiesel production

287

filtration may be used to remove insoluble and soluble impurities (soaps, free and bound glycerol, and other polar materials). Transesterification can be carried out as a batch process, as a continuous or semicontinuous process. Depending on the process conditions and type of process chosen, a heterogeneous catalyst can be slurried in the reaction mixture or can be used in a fixed bed. Chapter 11 describes transesterification process technology for biodiesel in more detail. Research demands for alcoholysis include: ∑ ∑ ∑ ∑ ∑ ∑ ∑

optimisation of current technology; use of alternative, non-edible raw materials; new catalyst development; design of reliable small-scale production units; valorisation of glycerol; improvement of biodiesel oxidation stability; and development of cold-flow property improvers.

7.2

Process variables

Transesterification transforms triglyceride molecules (90–98% of the oil), which are long and branched, into smaller esters whose size and physical properties are similar to those of diesel oils. The main factors affecting the transesterification reaction time and conversion and purity of the product esters are the molar ratio of alcohol to triglycerides, kind of alcohol, catalyst type and concentration, reaction conditions (temperature, pressure, mixing intensity, co-solvent) and degree of refinement of the vegetable oil (including FFA and water contents) [3]. There is also an effect of the nature of the glyceride. In fact, methyl esterification of linolenic acid is faster than that of linoleic and oleic acids [4]. Although crude oils can be transesterified, ester yields are reduced because of gums and extraneous material present.

7.2.1 Reaction temperature The reaction conditions generally involve a trade-off between reaction time and temperature as reaction completeness is the most critical fuel quality parameter. The rate of reaction is strongly influenced by the reaction temperature. Given enough time, in the presence of an alkaline catalyst the reaction will proceed to near completion even at room temperature. Depending on the oil used, transesterification can occur at different temperatures, e.g. 293–308 K for castor oil [5], and 305–333 K for SBO [6]. To decrease costs, transesterification should preferably be carried out at ambient temperature. However, the reaction is generally conducted close to the boiling point of methanol at atmospheric pressure. Reaction temperatures above 333 K are to

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be avoided because they tend to accelerate saponification of the glycerides by the alkaline catalyst before completion of the alcoholysis, which is an undesirable result in view of the negative effect on the conversion [7]. Mild reaction conditions require removal of free acids from the oil by refining (degumming) or pre-esterification (deacidification) of the feedstock. Pretreatment is not required if the reaction is carried out in drastic reaction conditions of high temperature (> 512 K) and pressure (> 9 MPa) [8]. Under these conditions simultaneous esterification and transesterification take place. Catalyst-free transesterification with supercritical methanol proceeds appropriately at about 623 K [8].

7.2.2 Nature of the alcohol Selection of the alcohol is based on cost and performance considerations. Optimisation of transesterification reaction conditions of RSO with lower aliphatic alcohols (C1-C4), varying molar ratio of alcohol to oil, catalyst and catalyst quantity, reaction temperature and time, and aiming at high ester yields of biodiesel fuel quality with a minimum of time and material expenditures, has indicated that KOH is most useful for the preparation of methyl and ethyl esters [9]. As shown in Table 7.1, an increased temperature was necessary for the preparation of rapeseed oil ethyl ester. Propyl and butyl esters were obtained only under acid catalysis conditions. The reaction catalysed by H2SO4 was successfully accelerated using slightly higher catalyst concentrations at the boiling points of the alcohols used. Branched-chain alcohols react more slowly than their linear homologues, while t-butanol does not react at all. Occasionally also the use of glycerols (EG, DEG, GL) as transesterifying alcohols has been considered [10]. Methanol is the most commonly employed alcohol in view of its low price, high reactivity and minimisation of hydrolysis and soap formation. Table 7.1 Transesterification of rapeseed oil using C1-C4 alcohols (after ref. [9])   Alcohol Molar Catalyst ratioa

Catalyst quantityb (%)

Reaction Reaction temperature time (h) (K)

Degree of transesterification (%)

MeOH EtOH n-PrOH n-PrOH i-PrOH n-BuOH n-BuOH i-BuOH

1.0 1.5 2.0 1.5 1.5 2.0 1.5 1.5

298 338 370 363 357 390 390 372

98.6 98.5 64.4 98.6 97.6 15.4 97.5 96.7

a

6:1 6:1 9:1 9:1 9:1 6:1 9:1 9:1

KOH KOH KOH H2SO4 H2SO4 KOH H2SO4 H2SO4

3 3 5 3 4 5 3 4–5

Molar ratio of alcohol to oil. Percentage of the catalyst used calculated on the basis of the weight of oil used.

b

Transesterification processes for biodiesel production

289

However, methanol is hydroscopic and toxic. Due to the hydroscopic nature of methanol, contaminants such as the humidity or moisture in the air can decrease the effectiveness of the catalyst, creating the potential for yield loss and foaming in biodiesel production. Methanolysis occurs only in the methanol phase. Methyl-esterified biodiesel fuel has a disadvantage in that the pour point is high as compared with light oil (which is petroleum-based fuel) for diesel engines. While the pour point of commercially available light oil is 258 K, the pour point of methyl-esterified fuel is about 271 K. For this reason, methyl-esterified fuel is less suitable for use in cold regions. Therefore, in many countries, biodiesel blended with petrodiesel is commonly used. The prospects for using ethanol for transesterification are rather attractive since this environmentally friendly alcohol with low toxicity can be of a renewable origin and the final product would then be produced from 100% renewable sources. Furthermore, the use of ethanol in the transesterification reaction will enhance the possibility of performing the oil extraction from the seeds and the transesterification reaction simultaneously. Using ethanol as the extraction solvent will result in a number of assets in environmental and financial terms [11, 12]. Technical advantages of the use of ethanol include lower cloud and pour points than methyl esters, favouring cold starts, and higher heat content and cetane number. The use of ethanol as a reactant usually implies that it is in anhydrous state and that the oils are neutral (i.e. refined). Drying of ethyl alcohol requires sophisticated equipment, and production costs of absolute alcohol are high. The effect of the water content on the reaction extent is considered as a major problem associated with ethyl ester production [13]. The (negative) effect of water on the transesterification kinetics of cottonseed oil with ethanol has been quantified [14]. Use of hydrated ethyl alcohol in the manufacture of fatty acid esters is of considerable interest [15]. Table 7.2 compares methylation to ethylation. From a technical and economic point of view transesterification with methanol is much more advantageous than with ethanol: Table 7.2 Comparison of methylation and ethylation of vegetable oils and fats Process parameters

Methylation

Ethylation

Alcohol consumption (kg) per 1000 L biodiesel Alcohol costs (US Cts/gal)a Required excess alcohol (%)c Recommended reaction temperature (K) Reaction time (min)

90 103 100 333 45

130 310b 650 358 90

a

US contract price (FOB) (5 May 2006). Industrial (99%). c Recoverable by distillation after the reaction. b

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∑

Methanol consumption in transesterification is some 40% less than that of anhydrous ethanol. ∑ The reaction time for methanolysis is about 50% that of ethanolysis, for the same yield. ∑ Usually higher alcohol-to-oil stoichiometric ratios are necessary in order to achieve acceptable yields from transesterification when using ethanol. ∑ For the same biodiesel production, vapour consumption in methanolysis is 20% less than for ethanolysis and electricity consumption is about half. ∑ Process equipment for methanolysis is about 25% of the size of that of ethanolysis. The processing costs of fatty acid methyl ester (FAME) are about 50% of that of FAEE. Finally, with absolute alcohol, the glycerol that is formed does not settle spontaneously and the alcohol excess must be evaporated or water added. With the high process costs and more difficult separation of the ethyl ester and glycerol phases, bioethanol diesel fuels are economically less competitive than FAME. Only Brazil produces biodiesel via conventional ethanolysis (see Fig. 11.17). Industrial-scale production of fatty ester ethyl esters (FAAEs) is limited. In fact, studies of ethanolysis of vegetable oils (VOs) are equally limited [6, 9, 11–33] compared to methanolysis and have concerned various substrates, such as CSO [14, 32], RSO and canola oil [9, 12, 13, 17, 29–31, 34, 35], SBO [20, 33], SNO [6, 21, 25, 26, 29], castor oil [32], grapeseed oil [28] and soapstock [27]. Knothe [36] has described how ethyl esters were proposed as diesel fuel substitutes in the former Belgian Congo as early as 1937. Recently, microbial FAEE biosynthesis from glucose and oleic acid has been described [37] (see Section 15.3.3). Despite considerable cold-flow properties of the esters of higher or secondary alcohols, their economic production as biodiesel fuels is unfavourable (high alcohol price, more intensive energy input during ester production, requirement of more costly acid or enzymatic catalysis) compared with the methyl esters. Use of branched alcohols leads to improved CFPP and cetane numbers [38]. Isopropyl esters have better fuel properties than methyl esters [39]. Propyl and ethyl esters are, however, valuable compounds for a variety of other purposes, such as in lubricants [40] or in drying compositions used in the agricultural industry [41]. As pure esters they are also widely used in the cosmetics industry. ‘Bioethanol’ may also be considered as a raw material for biodiesel production. The ‘bioethanol’ solution often reported in the literature is a mixture of ethanol and water, whereas the real composition of bioethanol obtained by fermentation and simple distillation actually consists of water, methanol, ethanol and so-called fusel oil (containing n-propyl, n-butyl, secbutyl, isobutyl, n-amyl and isoamyl alcohols) [42, 43].

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7.2.3 Molar ratio of alcohol to oil The molar ratio of alcohol to oil is one of the most important variables affecting the yield of alkyl esters. Stoichiometrically, three moles of alcohol are required per mole of triglyceride, but in practice a (large) excess of alcohol is employed in order to displace the equilibrium to greater ester production. Yield is a most important factor affecting commercial profitability. It is therefore crucial to achieve a near 100% transesterification of TGs and FFAs. Conversions lower than 90% are not of commercial interest. Figure 7.1 shows the effect of alcohol-to-oil ratio on product composition for transesterification [6]. Typically, the optimal ratios for methanolysis of Cynara oil are between 4.05 : 1 and 5.67 : 1 [44]. Below 4.05 : 1 the reaction is reported to be incomplete, whereas above 5.67 : 1 it becomes difficult to separate glycerol from methanol as a by-product. The optimum molar ratio between alcohol and oil ensuring highest reaction rate depends on the type of catalyst used:

100

Triglyceride

Sunflower methyl esters

Product composition (wt%)

80

Reaction conditions 60 g sunflower oil (edible grade) 333 K, 1h, 0.5 wt% NaOCH3 (catalyst)

60

40 Diglyceride Monoglyceride

20

0 0

1

2 3 4 Molar ratio MeOH/sunflower oil

5

6

–100

–66

–33 0 33 Excess MeOH (wt%)

66

100

7.1 Effect of alcohol-to-oil ratio on product composition for transesterification (after ref. [6]).

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typically 6 : 1 for alkali-catalysed transesterifications [45, 46] and up to 30 : 1 for acid-catalysed alcoholysis [6]. Even higher molar ratios (up to 45 : 1) may be necessary when the oil contains a large amount of free fatty acids [6]. In industrial processes a methyl ester yield of over 98% is normally achieved for 100% excess of methanol. Experiments conducted with molar ratios of 8 : 1 and 6 : 1 for mixing speeds of 0–3600 rpm and a catalyst (NaOH) concentration of 0.1 wt% have shown considerably higher conversions of SBO at the molar ratio of 8 : 1 for all mixing levels [47]. Increasing the molar ratio of alcohol-to-TG increases alcohol recovery and product separation costs. Higher molar ratios also interfere in the separation of glycerol. Transesterification of RSO in supercritical methanol requires a molar ratio of 42 : 1 to achieve a yield of 95% of methyl esters [8]. One-phase methanolysis of SBO in the presence of a co-solvent benefits from an alcohol-to-oil ratio of 27 : 1 (Fig. 7.2). The transesterification reaction is also shifted to the right by removal of one of the products from the reaction mixture. This is a much preferred option to drive the reaction to completion.

Methyl ester content (wt%)

100

90

80

70 T = 296 K, THF co-solvent 60

MeOH/SBO oil (6 : 1), 1.0 wt% NaOH MeOH/SBO oil (6 : 1), 1.3 wt% NaOH MeOH/SBO oil (27 : 1), 1.0 wt% NaOH

50 0

5

10 Time (min)

15

20

7.2 Effect of alcohol/vegetable oil ratio for one-phase methanolysis of soybean oil at 296 K (replotted from data in ref. [48]).

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293

7.2.4 Catalyst type and concentration The catalyst employed has a direct impact on the purity of the feedstock required, the kinetics of the reaction, and the extent of post-reaction processing necessary. Use of a solid catalyst simplifies downstream purification of biodiesel. The search for improved catalysts is being pursued intensely. Sodium alkoxides are among the most efficient catalysts for transesterification, although KOH and NaOH can also be used. Transesterifications occur considerably faster in the presence of equivalent amounts of alkaline rather than (even more corrosive) homogeneous acidic catalysts. Suitable alkaline catalyst concentrations achieving high yields (>95%) are in the range of 0.5 to 1.0 wt%. Increase in catalyst concentration adds extra costs to the removal from the reaction medium at the end. Sodium methylate, used at approximately 0.5 wt% concentration for most transesterification processes, is estimated to represent 70% of the global biodiesel catalyst market. Sodium methylate is usually supplied as 25–30% solution in anhydrous methanol. Humidity can decrease the effectiveness of the catalyst. Although higher conversions are achieved at higher catalyst concentrations under otherwise identical flow and stoichiometric conditions, there are drawbacks to the excessive use of alkaline catalyst in the transesterification reaction. Higher catalyst concentrations increase the solubility of methyl esters in the glycerol phase of the final product. As a result, a significant amount of methyl esters remains in the glycerol phase after the phase separation [47]. (See also Chapter 8 for biodiesel catalysis). The difficulty of reproducing reaction kinetics results for transesterification of vegetable oils has been partly attributed to catalytic effects at the surfaces of the reaction vessels [49]. The effects are greatest at higher temperatures and may cause scaling-up problems in plant design. It has also been shown that lipases are able to catalyse the alcoholysis of triglycerides in both aqueous and non-aqueous systems (see Chapter 10). The possibility of applying this procedure to the synthesis of biodiesel from low-value materials such as soapstock has been suggested [50].

7.2.5 Purity of reactants The reagents and their proportions affect the process in terms of conversion efficiency, which differs according to the vegetable oil [6]. Impurities in the oil affect conversion rates. Under the same conditions, 67–84% conversion using crude VOs can be obtained, compared with 94–97% when using refined oils [6]. Much of the process complexity originates from contaminants in the feedstock, such as water and free fatty acids, or impurities in the final product, such as methanol, free glycerol, and soap [51]. Mild transesterification conditions require an oil neutralised by means of alkali refining, steam

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distillation or pre-esterification of free fatty acids. FFAs in the original oils interfere with alkaline catalysts. Conventionally, a transesterification reaction is carried out by eliminating water as much as possible. Pre-treatment and/ or esterification as optimal process steps are only required if the feedstock quality does not meet minimum specifications: typically FFA content < 0.5%, H2O content < 0.1%, unsaponifiables < 0.8%, and phosphorus content < 10 ppm.

7.2.6 Mixing intensity Depending on the nature of the alcohol (e.g. BuOH vs. MeOH), the reactants in the transesterification process may form either a single- or two-phase liquid. Poor diffusion between the phases results in a slow reaction rate when the reaction is diffusion controlled. The effect of mixing intensity on the continuous transesterification reaction was investigated by Noureddini et al. [47, 52]. Higher mixing intensities have a favourable effect on the overall conversion. There is an upper limit to the mixing intensity. The mixing effect is most significant during the slow rate region of the transesterification reaction. For a SBO/MeOH system at 343 K and high mixing speeds (600 rpm), mass transfer limitations are almost non-existent [52]. In the case of methanolysis, once methyl esters are formed they act as a mutual solvent for the reactants and a single-phase system is formed. Consequently, the effect of mixing then becomes insignificant. Understanding of the mixing effects on the kinetics of the transesterification process is of considerable value in process design and scale-up.

7.2.7 Product yield Biodiesel and by-product yields are feedstock dependent. FAME yield, methanol consumption and glycerol/water production can be calculated for a given feedstock [53]. Basic quality parameters are acid value (AV), saponification value (SV), ester value (EV) and hydroxyl value (HV) (see Section 6.3). EV denotes how many hydroxyl groups are esterified and HV how many such groups are free. Their sum therefore denotes the total number of hydroxyl groups. Any raw material used for biodiesel production can be evaluated on the basis of the AV, SV, EV and HV parameters. It has been shown that the FAME yield can be calculated as:

FAME (kg) =

W (3000 K + 4SV + 38AV – 92HV) 3000 K

7.9

where W is sample weight (kg) and K is the relative molecular mass of KOH (K = 56.11). Equation 7.9 shows that FAME yield is proportional to

Transesterification processes for biodiesel production

295

the raw material weight, is positively affected by the presence of FFAs (as expressed by AV) and negatively influenced by partial glycerides in the feedstock (as expressed by HV). HV can be used in conjunction with EV to calculate the theoretical glycerol yield from a given sample [53]. Table 7.3 shows the theoretical amount of FAME, glycerol and water produced and methanol consumed for various raw materials (soft oils, hard fats and high FFA oils/fats). (Trans)esterification of high FFA samples will result in lower glycerol, but higher water production. Another approach for the calculation of the theoretical FAME yield uses the effective concentrations of FFA, TG and partial glycerides (DG and MG) present in the raw material [53]. The amount of glycerol produced can be calculated as follows: Glycerol(kg) =

W ¥ 92.09 ¥ Ê TG + DG + MG ˆ ÁË 3M + 38 2M + 56 M + 74˜¯ 100 K 7.10

where M is the average relative molecular mass of the fatty acids.

7.3

Transesterification kinetics

Given the many process variables, it is not surprising to notice some difficulty of reproducing reaction kinetics results for transesterification of vegetable oils and animal fats. Table 7.3 Effect of feedstock composition on product yield (after refs [53, 54]) SBO

RSO

PMO

TLW

UCO

P-FADa

Feedstock composition (%) FFA TG DG MG AV (mg KOH/g) SV (mg KOH/g) HV (mg KOH/g) EV (mg KOH/g) <M>b

0.5 98.6 0.8 0.1 1.0 191.6 1.0 190.6 280

1.5 96.0 2.0 0.5 3.0 188.9 3.0 185.9 284

5.1 87.0 6.0 2.0 10.2 197.8 10.2 187.6 270

10.0 74.0 12.0 4.0 20.2 194.4 20.2 174.2 274

15.2 62.0 16.0 7.0 30.4 193.1 30.4 162.7 275

88.3 8.0 5.0 2.0 176.6 205.6 7.1 29.0 270

Methanolc

109.4

107.9

113.0

111.0

110.3

117.5

1004.2 104.9 0.3

1003.3 103.6 1.0

1000.4 109.1 3.3

996.1 108.1 6.6

991.1 108.9 9.8

1038.6 21.8 56.7

Product yield FAME GL Water a

c

FAD: Fatty acid distillate. Average relative molecular mass of fatty acids. c kg/t feedstock. b

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Biodiesel science and technology

The kinetics of the three-step catalytic transesterification reaction mechanism æ Æ DG ¨ æ Æ MG ¨ æ Æ GL), which is very complicated and involves (TG ¨ æ æ æ at least twelve equilibrium reactions [55], has been studied extensively for a variety of VOs: CSO, PNO, SBO and SNO (catalysts: NaOH and NaOMe) [6], SBO (catalysts: NaOMe and NaOBu, H2SO4) [45], SBO and CNO (catalysts: NaOH, NaOMe and NaOBu) [56, 57], SNO (catalyst: KOH) [58], SNO (catalyst: KOH) [59], PMO (catalyst: KOH) [60], RSO (catalyst: KOH) [61], SBO (non-catalytic) [49, 62], RSO (non-catalytic) in supercritical methanol [8], Pongamia oil (catalyst: KOH) [63, 64] and waste frying oil (catalyst: H2SO4) [65]. Also the effect of water on the transesterification kinetics of cottonseed oil with ethanol was reported [14]. The first reaction step of methanol and triglyceride forming diglyceride and one mole of methyl ester is rate limiting; the other steps occur much faster [58]. Transesterification kinetics are generally considered to be pseudo second-order for the first stages of the reaction followed by first order or zero order in the final stages of the reaction. The kinetics of catalyst-free transesterification of RSO in supercritical methanol was assumed to be first order [8]. The order of reaction changes with the reaction conditions. It is to be noticed that the reaction mixture is not homogeneous throughout the course of methanolysis. Freedman et al. [45] have reported a kinetic study of base-catalysed transmethylations of SBO using 0.5 wt% NaOMe and 1 wt% NaOBu. Whereas butanolysis (in a single liquid phase mixture) follows second-order kinetics, methanolysis (in a two-phase mixture) does not. The two-phase reaction proceeds as follows [57]. At the start of the reaction the concentration of the oil in methanol is very low. As the concentration increases, the reaction rate increases. The slow build-up of the oil concentration accounts for a lag time (Fig. 7.3). The concentrations of diglycerides and monoglycerides, formed in the methanol phase, do not build up to those predicted by second-order kinetics. The reaction is slow compared to butanolysis because, although the methanol concentration is high in the predominantly methanol phase, the oil concentration is very low. The reaction rate remains fairly constant before a sudden deceleration, which is consistent with the rate being mass transfer limited. Eventually, the reaction passes through an emulsion phase, and under circumstances which favour high conversion, a glycerol layer separates. In alkali-catalysed transesterification of vegetable oils (e.g. SBO, CNO) with MeOH and n-BuOH, essentially three regimes thus categorise the overall reaction process with the rate-limiting reaction step changing over time according to the observed reaction rate [45, 52]. Initially, the multiphase methanolysis reaction is diffusion limited because of the low miscibility of reagents (oil/methanol/catalyst), slowing down the reaction. The difference in initial reaction rates for the methanol and butanol systems can be traced back to the higher solubility of oil in the butanol-catalyst phase. Successively, the

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297

Ester groups transesterified (%)

60

40

20

0 0

2

4

6

8 10 Time (min)

12

14

16

7.3 Change in groups esterified with time for a molar ratio of: (∑) MeOH/SBO (6 : 1), 0.5 wt% NaOMe, 313 K; (®) BuOH/SBO (6 : 1), 1 wt% NaOBu, 303 K (after ref. [45]).

ester products formed act as emulsifying agents and determine a kinetically controlled second rate regime characterised by acceleration in product formation. The distribution of methanol and catalysts between biodiesel and glycerol phases has been examined [66]. The final stages of the reaction are characterised again by a slower reaction rate. At large excess of alcohol (ROH/TG molar ratio 30 : 1) a pseudo first-order reaction was found for both MeOH and n-BuOH. At low excess alcohol (6 : 1), both methanolysis and butanolysis are second-order reactions assuming that no diffusion limitations exist [56]. Activation energies for the base-catalysed methanolysis reaction are in the range of 6–20 kcal/mol [52, 60]. The problem of the mass transfer limitation in methanolysis may be addressed by the use of non-reactive co-solvents to form a single phase. The use of a co-solvent speeds up methanolysis considerably. One-phase methanolysis and butanolysis initially exhibit rapid ester formation, but then slow drastically (Fig. 7.4). This is caused by a drop in polarity resulting from the mixing of the non-polar oil with methanol. This lowers the effectiveness of both hydroxide and alkoxide catalysts. Increasing the MeOH/oil molar ratio to 27 in the one-phase system raises the polarity such that the methyl ester content of the product exceeds 99.4 wt% in 7 min (Fig. 7.2) [57]. This affects the size of methyl ester plants.

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Methyl ester content (wt%)

100

90

80

70

60

50 0

4

8 12 Time (min)

16

20

7.4 One-phase methanolysis at 296 K of: (∑) CNO with 1 wt% NaOH; (o) SBO with 1 wt% NaOH; (®) SBO with 1.3 wt% NaOH. Each experiment was conducted using 6 : 1 MeOH/oil molar ratio and THF as co-solvent (after ref. [57]).

7.3.1 Intersolubility of the reaction components The physical properties and intersolubility of the reaction components are very important for biodiesel production. The reactants (oil and methanol) and the products (FAME and GL) are partially mutually soluble in the reaction process. Intersolubility of the reaction components therefore constitutes essential data for the production design and process operation. The intersolubility changes with the oil resources and is known only for some oils, such as Jatropha curcas L. oil [67] and RSO [68]. The solubility is rather temperature insensitive in the temperature range of the transesterification reaction. On the whole, methanol is completely soluble in both FAME and glycerol but not soluble in oils or fats. Consequently, methanolysis benefits from thorough mixing. As the alkali catalyst exists in the methanol phase it is here that the transesterification reaction takes place [56], and therefore the reaction rate greatly depends on the solubility of oil in methanol. With an increase in the mass fraction of FAME, the solubility of methanol in the oil + FAME phase increases. Due to the initial heterogeneous phase distribution, methanolysis of SNO [58], SBO [56, 57], PMO [60] and RSO [61] is significantly mass transfer limited and exhibits an induction period of several minutes before significant amounts of methyl ester appear. When

Transesterification processes for biodiesel production

299

the FAME content increases (to 70% in case of Jatropha oil), the oil + methanol + FAME mixture becomes a homogeneous phase. The reaction then proceeds quite quickly, following second-order kinetics, and subsequently slows down drastically after some 10 min., when glycerol (partly together with catalyst and methanol) is removed from the reaction zone. Formation of glycerol and FAME may change the distribution of reaction components in different phases. Removal of glycerol from the reaction mixture enables high conversions. As glycerol has a low solubility in both oil and FAME, an advantage of methanolysis as compared to transesterification with higher alcohols is that these hardly miscible main products (FAME and GL) thus form a two-phase system consisting of an upper ester phase and a lower glycerol phase once a significant amount of glycerol has been formed. Therefore, glycerol can easily be separated from biodiesel by settling. The solubility of glycerol in FAME also directly influences the subsequent purification of biodiesel. In fact, glycerol can be extracted from biodiesel using cheap ionic liquids (e.g. choline chloride) [69]. The intersolubility is also essential data for the methanol recovery. Unreacted methanol is distributed in both FAME and glycerol phases. The solubility of COME (curcas oil methyl esters) in methanol is much higher than that of RME in methanol [68].

7.3.2 Transesterification process intensification Under atmospheric conditions, the transesterification reaction can require many hours to complete. Reaction time is influenced by the degree of dispersion of catalyst and alcohol in the vegetable oil phase and is lower at higher dispersion. The problem of process acceleration by increasing mass transfer rates can be faced in various ways. Processes of transesterification, as well as esterification and esterification-transesterification (both one- and two-step) for producing biodiesel may be enhanced by one or more of the following: ∑ applying microwave or RF energy (1000 m to 10–4 m wavelength); ∑ sonication; ∑ producing dynamic turbulence or high-shear conditions; ∑ emulsifying reactants with a homogeneous catalyst (droplet diameter from 0.001 to 1000 mm); ∑ use of co-solvents; ∑ creation of a sub- or supercritical reaction medium; or ∑ maintaining the reaction at a pressure at or above autogeneous pressure (i.e. at the sum of all reactant and product equilibrium partial pressures at a given temperature) [70]. Enhanced processes using one or more of these steps can result in higher process rates, higher conversion levels, or both [70, 71].

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Zhao [72] reported addition of a catalyst promoter with emulsifying capacity and weak acidity (such as alkyl benzene sulphonic acid, sodium dodecylsulphate and alkyl carboxylic acid) during the later stage of esterification of waste animal and vegetable oils with high acid value. Hooker [73] has described apparatus and method for the production of FAAE biodiesel fuel from vegetable oils and animal fats with an alkaline solution of a monoalkyl alcohol in which the reaction mixture is emulsified. Microwave-enhanced transesterification Microwaves and RF energy are more effective than traditional heating in activating transesterification as well as esterification and esterificationtransesterification reactions by means of homogeneous or heterogeneous catalysts. Microwave energy can be controlled by continuous wave or modulation methods. Continuous wave involves the application of microwave energy at a constant amplitude. Modulation techniques may include amplitude, frequency, pulse width or duty type modulation. By control of modulation, such as the microwave power’s duty cycle, the catalyst can be differentially heated and cooled. With a porous catalyst, this can result in enhanced diffusion of the reactants and products as the catalyst is heated and cooled, favouring higher reaction rates at lower bulk operating temperatures. There may also be a minimised or zero net temperature increase from the microwave or RF energy into the catalyst. Using microwave or RF energy may activate the catalyst site, enhance diffusion and removal of products from the catalytic site, and promote rapid separation and elimination of emulsions. The frequency of the microwave or RF energy may be selected to achieve high conversion of the reactants. Very high power microwave sources, at 915 MHz and 2.45 GHz, are commercially available. Conversion rates are relatively independent of microwave frequency. Lower frequencies have longer wavelengths and therefore have greater penetration depth into the catalyst and reactants, which allows the design of physically larger reactors. Lower frequencies, such as 915 MHz, are more suitable for larger, higher power reactors. The increased reaction rates, achieved by emulsification and microwave energy, allow for the use of lower catalyst concentrations. This determines lower catalyst and neutralisation costs, including the economical use of ion-exchange systems used in continuous process flow systems. When using a homogeneous catalyst, the reaction can be enhanced by emulsifying the feed oil with a solution comprised of the alcohol and the dissolved catalyst. The microwave energy further enhances the reaction through selective heating. Given an emulsion of alcohol, dissolved catalyst and triglycerides, the microwave will be preferentially absorbed by the alcohol phase raising its temperature, thereby increasing the catalyst rate. Homogeneous acid catalysts such as H2SO4, HNO3, H3PO4 and HCl are

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excellent microwave absorbers, the activity of which is greatly enhanced by microwaves. Methanolysis of commercial seed oils under microwave irradiation in the presence of various homogeneous base and acid catalysts requires very short reaction times (minutes) [74]. Microwave-enhanced reactions are usually optimised by trial and error. Proper control and use of the dielectric loss tangent in the heterogeneous catalyst support leads to the efficient use of microwave energy. Amorphous and crystalline supports may have differing dielectric loss tangents (or dissipation factors). Figure 7.5 shows the microwave effect on SBO methylation over a heterogeneous base catalyst [70]. In PCT Int. Publ. No. WO 03/014272 A2 Breccia Fratadocchi [75] describes methods using microwave radiation (900 MHz, 2.45 GHz) and radiofrequencies for hydrolysis of natural triglycerides (PNO, RSO) followed by methanol esterification of the resulting fatty acids using a variety of catalysts (sodium methylate, basic montmorillonite, neutral and acid aluminas, tungsten boride). The reactivity of the triglycerides and of oleic acid has been enhanced, reducing the conventional industrial process time from 90 to 30 min and simultaneously minimising the quantity of methanol to just over the stoichiometric ratio [75]. Microwave heating in conjunction with heterogeneous barium, alumina, silica, KSF montmorillonite, zinc aluminate and zirconium-based catalysts has also been reported [70, 76, 100

SBO conversion (%)

80

60

40

20 Test 1, 0 W/cm3 Test 2, 1 W/cm3 0 0

10

20

30 Time (min)

40

50

60

7.5 Microwave effect with heterogeneous base catalyst at 0.052 m/s and molar MeOH/SBO ratio 4 : 1 (after ref. [70]).

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Biodiesel science and technology

77]. Microwave-enhanced transesterification is fast and safe, but expensive. Microwave technology has been used in continuous-flow production [78]. However, microwaves are limited in large-scale organic synthesis. Microwaveassisted reactions suffer from a scale-up problem, or a ‘penetration depth’ problem, as microwaves are absorbed after passing through a few centimetres of liquid. Ways of overcoming the problem are stirring or use of a customdesigned reactor, for example one in which reagents flow past microwaves in thin pipes so that the electromagnetic fields can penetrate the whole sample. Only a few papers have reported work on microwave extraction. Ultrasonic processing Similary, ultrasonication (US) can improve the commercial conversion processing (transesterification) of vegetable oils or animal fats to biodiesel by improved mixing (emulsification of immiscible liquids) and enhanced chemical activity avoiding the use of large volumes of solvents. Transesterification (at or near atmospheric pressure) occurs when the natural boundary surfaces of the immiscible mixture are enlarged by ultrasonic cavitation in the reaction section [79]. Ultrasound allows for in-line commercial processing. Ultrasonication can achieve a biodiesel yield in excess of 99% and may reduce the processing time from the conventional 1–5 h batch processing to less than 5 min. Ultrasonication can reduce the separation time from 5 –10 h (using conventional agitation) to less than 30 min. Ultrasound does also helps to decrease the amount of catalyst required by 50–60% due to the increased chemical activity in the presence of cavitation. Another benefit is the increase in purity of the glycerol. Most commonly, sonication is performed at elevated pressure (0.1–0.3 MPa) using a feed pump and an adjustable back-pressure valve. Ultrasonic processing costs comprise mainly the investment for US devices, utility costs and maintenance. Required power ranges from 1 kW for flow rates of 150–250 L/h to 992 kW for flow rates of 150–250 m3/h. The resulting costs for ultrasonication vary between 0.2 ct and 1.5 ct (US$) per litre when used on a commercial scale [80]. It has been observed that the reaction time of base-catalysed transesterification of VOs is considerably shorter (10–20 min) by low-frequency US (40 kHz) than for mechanical stirring at a several times lower quantity of required catalyst [55, 81]. In another instance, alkaline catalysed conversion to FAME exceeded 99.4% after 15 min of ultrasonic agitation at 313 K and a 6 : 1 MeOH/SBO molar ratio [82]. In this case, reaction rate constants were three to five times higher than those reported in the literature for mechanical agitation. The observed mass transfer and kinetic rate enhancements are ascribed to an increase in interfacial area and activity of the microscopic and macroscopic bubbles formed when US waves of 20 kHz are applied to a two-phase system. In other cases, cavitation was achieved by permitting

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air to enter the transesterification flow system through an adjustable air inlet valve [83]. Gryglewicz [84] has reported heterogeneous base-catalysed methanolysis of refined LE-RSO over Ba(OH)2, Ca(OCH3)2, CaO and NaOH using ultrasound and THF to accelerate the process. However, the reaction rate decreased in the case of CaO. It is a fact that ultrasonic waves result in an increase of reaction rate if the catalyst is soluble or well dispersed in the liquid phase of the reagents. In the considered cases, NaOH and Ba(OH)2 are well soluble in methanol, and Ca(OCH3)2 forms a colloidal suspension. On the other hand, CaO is a typical heterogeneous catalyst, where adsorption of reagents on its surface plays a vital role. In this case, ultrasound probably prevents the adsorption process on the catalyst surface. Also continuous acid-catalysed esterification using ultrasound, as a pretreatment step of FFA-rich (> 5%) triglycerides, has been described [85] (see Section 11.2.2). Hielscher Ultrasonics GmbH (Teltow, Germany) earned the Frost & Sullivan’s 2007 European Technology Innovation of the Year Award in Biodiesel Processing Technologies. The Hielscher ultrasound technology [80] reduces the reaction time from several hours to less than 1 h with 99% yield in a typical batch process. Dynamic turbulence Stirring in tube reactors has been used to provide adequate turbulent and laminar flows [86]. An Energea base-catalysed variable pressure process for biodiesel production [87], which operates under conditions of powerful dynamic turbulence, as a result of the presence of mono- or polydisperse beads in the reactor, cavitation emulgation or ultrasounds, is illustrated in Fig. 11.5. In US Patent No. 6,392,062 B1 to Haas (to Degussa AG) [88] discontinuous or continuous homogeneously catalysed reactions such as (trans)esterifications are enhanced through contacting the reaction partners with a stationary or moving bed consisting of porous non-catalytic particles with a pore volume of 0.1–3 mL/g. The liquid-phase reaction is preferably conducted in a trickle bed operation over a stationary fixed bed. The homogeneously catalysed reaction can be accelerated by more than a factor of 10. The porous particles act primarily by their texture. Solids with a high number of mesopores (pore diameter of 2–50 nm) and micropores (pore diameter of less than 2 nm) are most advantageous (e.g. activated carbons, TiO2, Al2O3, SiO2, zeolites, etc.). Apart from the increase in the acceleration of the homogeneously catalysed reaction, there is the possibility of achieving greater selectivity as well. The ShockWave PowerTM reactor (SPR) has been described as a nextgeneration reactor for the biodiesel industry, applicable for both continuous and batch processing. As a liquid passes through the reactor it is subjected to controlled hydrodynamics cavitation producing microscopic bubbles,

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Biodiesel science and technology

and as they collapse, shockwaves are given off the liquid [89, 90]. This increases the surface contact area between the reactants. The process intensity drives the reaction further to completion than with conventional reactors in a fraction of the time. SPR technology (Hydro Dynamics, Inc., Rome, GA) harnesses cavitation to transesterify vegetable oils or animal fats in seconds. The technology is used in various industrial plants (e.g. Berkshire Biodiesel, Pittsfield, MA; Connecticut Biodiesel, Suffield, CT). Cavitation Technologies, Inc. (Los Angeles, CA) is another hydrodynamic cavitation technology provider. In biodiesel manufacturing essentially two chemical reactions are competing, namely transesterification (desired, fast) and saponification (undesired, slow); the latter reaction is more affected by a decreasing reaction temperature. Innovative spinning tube-in-tube (STT) technology, developed by Kreido Biofuels (Camarillo, CA) – now Four Rivers Bioenergy, Inc. (Calvert City, KY) –, is a unique reactor design allowing fast reaction times (seconds), thereby rendering saponification quite insignificant [91]. STT technology, which is based on Couette flow dynamics (i.e. a steady laminar flow of a viscous fluid between two surfaces with constant shear), leads to higher utilisation of raw materials, lower by-products and no need for water washings. When a heterogeneous catalyst is subjected to the reactant’s high-shear fluid flow conditions, the catalytic reaction is enhanced. High-shear flow conditions (i.e. high tangential fluid velocity) of reactants over or at a catalyst surface improve the reaction time and reactant conversion. Consequently, a lower molar ratio of alcohol-to-vegetable oil and/or higher FFA/TG process rates, LHSV or WHSV, may be used. High-shear conditions occur when the reactants are brought into contact with a heterogeneous catalyst at a velocity exceeding about 0.001 m/s, but less than 0.5 m/s. In such high-shear conditions with a heterogeneous catalyst, 100% conversion of triglycerides may be achieved in a shorter period of time, purification steps can be reduced, and acid neutralisation steps may be eliminated. High-shear conditions shift the equilibrium of the reversible transesterification reaction to the product side by providing short catalyst contact time with the reactants and products. High-shear mixers are about eight times faster than using traditional agitation and accelerate batch conversions. Transesterification of vegetable oils to form biodiesel is a ‘long’ reaction, usually performed in batch. Conversion to continuous processing should improve the economics of the process, as the improved mixing should generate a better product (rendering the downstream separation processes easier), at lower residence time (reduction in reactor volume). These improvements can decrease the production costs of biodiesel. Transesterification of rapeseed oil with methanol and NaOH as the catalyst was recently performed in a pilotscale plant equipped with an oscillatory flow reactor [92]; see also Section 11.2.4.

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Co-solvent transesterification As mentioned before, mass transfer limitations in methanolysis may also be addressed by the use of non-reactive co-solvents to form a single phase. Onephase methanolysis of VOs was first reported by Kurz [93], using an excess of methanol (MeOH/oil molar ratio 6 : 1), and more recently by Boocock et al. [29, 56, 57, 94] and others [10, 95–97] using co-solvents (e.g. THF, DMSO, MTBE, oxolane, hexane, toluene). Boocock [48] has described basecatalysed transesterification using a single-phase solution of TGs in methanol or ethanol (alcohol/TG = 15–35 : 1). Transesterification of glycerides or esterification of free fatty acids in a single critical phase medium increases reaction rates, decreases loss of catalyst or catalyst activity and improves the overall yield. Indeed, one-phase methanolysis occurs considerably faster than in the two-phase liquid system (VO and catalyst/alcohol), 95 wt% methyl ester being formed in 20 min (Fig. 7.2). Boocock’s technique [48, 57] for accelerating the transesterification reaction rate (with substantial completion within a few minutes for a high alcohol/VO ratio) by addition of co-solvent to create a single phase is also applicable for acid-catalysed pre-treatment of high FFA feedstocks. In another instance, biodiesel was prepared from crude oil of Pongamia pinnata and methanol by alkaline catalysis (KOH) and solid-acid catalysis (Hb-zeolite, montmorillonite or ZnO) using THF as a co-solvent [96]. Palm oil was transmethylated in an organic solvent (toluene) with NaOMe at 343 K [98]. The effect of methyl tert-butyl ether (MTBE) as a co-solvent on transesterification of SNO has been described [97]. A hydrophobic solvent was used in CaCO3-catalysed transesterification [99]. The primary concern with the co-solvent method is the additional complexity of recovery (energy intensive preparations) and recycling the co-solvent, although this can be simplified by choosing a co-solvent with a boiling point near that of the alcohol being used. Additional concerns relate to the hazard level associated with some of the co-solvents proposed such as THF and MTBE. Process intensification could eventually also take advantage of a reaction medium comprising a designer solvent, such as an ionic liquid (low melting point salt composed of anions and cations of greatly differing size), eventually in combination with supercritical CO2. The main drawback is price. Sub/supercritical fluids reaction media Homogenisation of the reaction medium can also be achieved by dissolving the reactants in a subcritical or supercritical fluid (under pressure). Japanese scientists first reported the use of supercritical methanol (scMeOH) for the conversion of RSO to RME [100] and of waste SBO [101] in 2001. Use of the alcohol reactant in a sub- or supercritical state was later also reported

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Biodiesel science and technology

by others [4, 102–110]. Critical temperatures of alcohols are as follows: MeOH 512.4 K; EtOH 516 K; n-PrOH 537 K; i-PrOH 509 K; n-BuOH 560 K; i-BuOH 548 K; and t-BuOH 506 K. In the common commercial catalytic production of methyl esters, which typically requires several hours at 333 K, the reaction is initially slow because of the two-phase nature of the methanol/oil system. However, in the supercritical state of methanol (critical T, p of 512.4 K and 8.09 MPa) the solubility parameter of MeOH (about 26 (MPa)1/2) tends to decrease to be closer to that of the oil (e.g. 18 (MPa)1/2 for RSO). The lower dielectric constant of liquid methanol favours the solubility of oil in methanol to form a (supposedly) single MeOH/oil phase. Additionally, the solubility of triglycerides in MeOH increases by about 2–3 wt% per 10 K increase in reaction temperature [111]. A kinetic study has confirmed that the reaction rate constant in supercritical transesterification is greatly increased [8]. Consequently, the reaction can be completed in a very short time. Saka and Kusdiana [4] have reported catalyst-free supercritical methylation of RSO with high conversion (>95%) at 45 MPa and 623 K for a molar ratio MeOH/RSO = 42 : 1 in 240 sec. Moreover, in the absence of a catalyst the product purification procedure is simplified and less energy is needed for this environmentally friendly manufacturing process. The non-catalytic biodiesel production route with supercritical methanol allows a simple process and high yield because of simultaneous transesterification of triglycerides and methyl esterification of fatty acids. The supercritical method also deals with the free fatty acid problem. Because it dissolves the feed material and eliminates the need for a base catalyst, there are no problems with soap formation and loss of yield. The supercritical method actually prefers FFA-rich feedstocks. The presence of water does not negatively affect formation of methyl esters in the supercritical methanol method [103, 109]. Supercritical transesterification can tolerate feedstocks with very high contents of FFAs (up to 36 wt%) and water (up to 30 wt%) [112]. The conventional supercritical methanol method requires a large excess of methanol. Using propane as a co-solvent allows a decrease in Tc from 593 K to 553 K, in pc from 40 to 12.8 MPa, and in the molar MeOH/SBO ratio from 42:1 to 24 : 1 [113]. As supercritical methanolysis is more expensive than conventional transesterification (see Section 14.5.2), the method is not used for the conversion of expensive refined oils and is best reserved for cheap unrefined oils. Table 7.4 lists the main features of supercritical methanolysis, while Table 7.5 summarises the superiority of the non-catalytic supercritical methanol process over the common catalytic transesterification. Supercritical methanol treatment is a very robust process able to convert high-FFA containing feedstocks in good yield. scMeOH allows economic conversion of low-quality feedstocks like chicken fat (12% FFA) and (refined crude) tall oil fatty acids (TOFAs) with yields exceeding 89% and

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Table 7.4 Supercritical methanolysis Advantages: ∑ Treats FFAs and triglycerides (simultaneous esterification/transesterification) ∑ No catalyst required ∑ Not inhibited by water ∑ Short reaction times ∑ Simple product separation ∑ Simple process scheme Disadvantages: ∑ High T, p without co-solvent ∑ Large excess of methanol (MeOH/VO ~ 40) without co-solvent ∑ Cost    Table 7.5 Comparison between common methanolysis and supercritical methanolysis for biodiesel production (after ref. [4])     

Common method

Reaction time 1–8 h Reaction conditions 0.1 MPa, 303–338 K Catalyst Acid or alkali Free fatty acids Saponified products Yield (wt%) 96 Removal for purification Methanol, catalyst,     glycerol, soaps Process Complicated

scMeOH method 120–240 s > 8.09 MPa, > 512.4 K None Methyl esters, water 98 Methanol Simple

94%, respectively [114]. US Patent No. 6,887,283 to Ginosar and Fox [115] describes a process in which glycerides or FFAs in animal fats, vegetable oils, rendered fats and restaurant grease, mixed with an alcohol or water stream and dissolved in a critical fluid medium, were reacted over either a solid or liquid acidic or basic catalyst (see Section 9.3.1). Figure 9.2 shows a block flow-diagram of a continuous process for transesterification in a critical fluid medium. Wang et al. [105] have produced biodiesel oil by reacting animal and plant oil, waste food oil, seed oil, etc., with a low-carbon alcohol in supercritical state, both in the absence and presence of a solid catalyst. It is clearly an objective of advanced production technology of biodiesel to obtain high yields without using a catalyst. Supercritical transesterification for continuous biodiesel production from waste cooking oil can be scaled up from 8 kt/yr to 125 kt/yr resulting in high purity methyl esters (99.8%) and glycerol (96.4%) [109]. Saka and Fukuzono [116] have described a process for production of biodiesel fuel fatty acid ester compositions characterised by a first step of reacting fats and oils containing fatty acid glycerides with sub- or supercritical water (hydrolysis) to form fatty acids, removal of water from the reaction mixture, and a second step of adding an alcohol to the residue

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of the dehydration step and reaction in a sub- or supercritical state to form fatty acid esters. This procedure allows conversion of any oil to biodiesel without the use of a catalyst. Saka’s hydrolysis-(trans)esterification process [117] for producing FAAEs from FFA and water-containing (waste) oils and fats by reaction at 523–573 K and 15–25 MPa for 15–25 min in the presence of an alcohol and/or water eliminates several problems of the conventional alkali catalyst method, such as catalyst separation/recovery and excess catalyst consumption by the free fatty acid. Figure 7.6 compares esterification of FFA and transesterification of TG at 573 K and 30 MPa [117]. Saka and Isayama [118] have also described biodiesel production without glycerol formation from oils and fats using supercritical carboxylate esters (methylacetate and formate).

7.4

In-situ transesterification

In-situ transesterification of lipids in oilseeds and other biological materials may be carried out in the presence of an extraction solvent or in solvent-free mode. Whereas in the former procedure extraction of oleaginous seeds and transesterification of the extracted oil take place in an integrated process [119], the latter procedure eliminates the air-polluting chemical hexane from

100

Esterification

Yield (wt%)

80

Transesterification

60

40

20

0 0

2

4 6 Reaction time (min)

8

10

7.6 Comparison of esterification of fatty acid and transesterification of fatty acid glyceride in supercritical alcohol treatments at 573 K and 30 MPa (after ref. [117]).

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309

the process by simply skipping the oil extraction step. Differences between conventional and in-situ transesterification are shown in Fig. 7.7. Stern et al. [15] have described in-situ transesterification by using an extraction solvent and a reactant (aqueous EtOH) in contact with cottonseeds. Acid-catalysed in-situ transesterification has been reported for rice bran oil, a highly acidic oil obtained from the waste material produced during rice-dehulling [120, 121]. The lipid contents of the hull contribute to the overall yield of esters from the seed and lipid losses due to hull-kernel separation are avoided. In the esterification with methanol, all free fatty acids dissolved in methanol were interesterified within 15 min. Similarly, acid-catalysed in-situ transesterification of soybean [122] and sunflower seeds [123] was reported. The same procedure is applicable to palm-fruit pulp [124]. In in-situ alcoholysis with a variety of alcohols, ethyl, n-propyl and n-butyl esters of soybean fatty acids could be obtained in high yields, at variance to methyl esters, as methanol is a poor solvent for soybean oil [122]. Reactive extraction of biodiesel from rapeseed using methanol, ethanol and methanol/ethanol mixtures was reported [125]. Also in-situ transesterification of Cynara cardunculus seeds was described, with a biodiesel yield of 36% and 75% FAME content [126]. Similarly, an integrated process has been reported for producing biodiesel from castor bean seeds, comprising alkaline-catalysed ethanolysis (using anhydrous EtOH) [18]. Whereas the resulting FAEEs are used as biodiesel, the solid fractions may be used as fertilisers, for feeding cattle and as a raw material for producing ethyl alcohol. The efficiency of production of FAME from Whole seeds Hexane extraction

Oil

Transesterification

Transesterification Pure esters

Crude product

Distillation Crude product

Pure esters

7.7 Conventional and in-situ transesterification processes (after ref. [123]).

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materials not used so far for this purpose, such as seed cakes, has been improved by the application of ultrasound [127]. In in-situ derivatisation assisted by ultrasounds (ultrasonically assisted extraction transesterification, USAET) for biodiesel production, the TGs contained in solid material are extracted and immediately transesterified in a methanolic solution of 1 M NaOH in an ultrasonic field, thereby greatly increasing the total yield in most instances: from 46% to 85.5% for CSO, from 67.2% to 93% for SNO, and from 43.2% to 83.5% for SEO [127]. Overall advantages of the proposed methodology include the elimination of saponification, low reaction time, milder reaction conditions, and higher FAME yields. Solvent extraction of sunflower seeds leads to higher yields (44–45%) than pressure extraction (38%) [128]; whole sunflower seeds contain some 5.5% of water. In-situ transesterification of sunflower seeds with acidified methanol produces FAME in yields significantly higher than with the conventional procedure with pre-extracted oilseed [123, 129–131]. Moisture in the seeds reduces the methyl ester yields. By drying oilseed flakes before starting the biodiesel synthesis, the required methanol volume can be greatly reduced [132]. Acidified hexane extracts 11% more total lipids from soybean than hexane alone [133]. Acidic conditions of the in-situ reaction apparently have a similar effect. The lipid fraction of whole oleic sunflower seeds has been transformed in-situ into fatty alkyl esters used as lubricants in a thermomechanico-chemical twin-screw system [134]. High levels of transesterification of lipids resident in biological materials can be achieved under mild temperatures and ambient pressures with relatively short incubation times in alkaline alcohol solutions [135]. The approach, which eliminates the need for lipid isolation by solvent extraction or expelling, and the use of extracting solvents, reduces process steps, and expands potential biodiesel production by allowing the use of lipid-bearing materials not currently used as such (e.g. distillers dried grains, meat and bone meal). Nevertheless, the cost of biodiesel produced through in-situ transesterification is higher than that made using the traditional route (typically US$1.02/gal and US$0.38/gal, respectively for soy diesel) [132]. Finally, reactive extraction of triglycerides and FAME formation was reported using fungal (Aspergillus flavus) resting cells and oilseeds at moderate temperature, either with solvents or in a solvent-free system [136].

7.5

Non-catalytic fatty acid alkyl ester production

In a catalytic reaction to produce biodiesel through transesterification, several processes, such as purification of the esters, separation and recovery of unreacted reactants and catalysts, are involved. These processes render production of biodiesel through a conventional catalytic transesterification system complicated, thus giving a reason to investigate the production of

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alkyl esters from vegetable oils via non-catalytic reactions. The absence of a catalyst simplifies a series of industrial process steps, and the production costs can be reduced. In addition, by-products such as fatty acid salts or free fatty acids are not formed, and thus fatty acid esters can be prepared at a high yield. It is sometimes difficult to distinguish between a catalytic and a thermal effect (no catalyst). If transesterification is carried out in the absence of a catalyst it is possible to obtain, at certain temperatures, conversions exceeding 80%, but at very low oil volume/catalyst volume/h and with very long residence times. In many cases reported reaction conditions for presumed heterogeneous alkali transesterification catalysts, such as CaCO3 [137], Ca/ Ba-acetate [138] and Cs-laurate [139] are so drastic that one might indeed wonder about a catalytic effect at all. Suitable experiments without catalyst for comparison are often lacking. On the other hand, much work that was considered to be non-catalytic may have been catalysed by the metallic reactor surfaces [49]. Reaction kinetics for non-catalytic alcoholysis (MeOH, EtOH, i-PrOH) of SBO, conducted in glass capillary tubes at 393 to 453 K, has shown that the reactivity of the alcohols increases with decreasing carbon number [49]. Due to the limited solubility of the alcohols in soybean oil, higher alcohol stoichiometries did not significantly increase reaction rates. At less than 20% conversion, the solubility of the alcohols in SBO increases continuously; at higher conversions the reaction systems become homogeneous until a glycerol phase is formed at high conversions. Although transesterification of triglycerides with lower alcohols proceeds in the absence of a catalyst, drastic reaction conditions (high T, p and alcohol/ VO molar ratio) are usually required. Several non-catalytic transesterification studies have been carried out at high T, p in order to increase the reaction rates to acceptable levels [4, 8, 49, 62]. For example, non-catalytic methanolysis of SBO takes place at 508 K and 6.2 MPa in 10 h with 85% yield [62]. Therefore, although high-purity esters and soap-free glycerol are produced, the process is still uneconomical. It is of great interest to develop advanced and practical biodiesel fuel technology producing high yields without use of a catalyst. Biodiesel production from animal fats and oils, waste edible oils, seed oils, etc. using non-catalytic (and catalytic) supercritical low-alcohol transesterification has been reported with increased reaction rate and with TG conversion rates of 80–100% [62, 100, 103, 105–107, 140–145]; see pages 305–308. This is not surprising as the supercritical state of methanol (Tc = 512.4 K, pc = 8.09 MPa) leads to a single oil/methanol phase. As shown in Fig. 7.8, the catalyst-free supercritical methanol (scMeOH) method is much simpler than conventional catalytic transesterification as only removal of methanol is required. Product purification is greatly simplified. Free fatty acids, which are converted to saponified products by the alkaline catalyst in the

312

Biodiesel science and technology Vegetable oil scMeOH Methyl (trans)esterification

<Standing separation> (30 min)

[Upper]

[Lower]

Evaporation of MeOH

Evaporation of MeOH

(363 K, 20 min) Methyl esters

Glycerol

7.8 Schematic process of biodiesel fuel production by supercritical methanol (adapted from ref. [4]).

conventional transesterification procedure, are converted to methyl esters through the dehydration reaction during supercritical methanol treatment [8]. However, even using scMeOH the reaction conditions remain rather drastic, as shown for rapeseed oil [100]. Optimum conversion rate (over 95%) was obtained in 120–240 sec at 623 K and 45 MPa for a molar ratio of MeOH/RSO = 42 : 1 [4, 8]. This is significantly faster than conventional non-catalytic methyl esterification of SBO (85% yield at 508 K in 10 h) [62] or in-situ transesterification of SNO using an acid (H2SO4) catalyst (91.3% yield at 337.5 K in 3 h) [123]. For efficient progress of transesterification a large excess amount of alcohol is required. Non-catalytic transesterification of chicken fat (6% FFA) at 598 K with supercritical methanol in 94% yield was reported for a molar ratio 1 : 40; under the same processing conditions crude tall oil (CTO) was converted in 89% yield for a molar ratio of 1 : 10 [146]. In US Patent No. 6,187,939 B1 to Sasaki et al. (to Sumitomo Chemical Company Ltd.) [101] catalyst-free transesterification of oils and fats in a supercritical state has been indicated as very advantageous from the point of view of environmental pollution, and recovering and recycling of resources. High conversions after 30 min were reported for waste SBO under conditions of high T (523–573 K), high p (6.5–10 MPa) and high molar ratio of methanol-to-glyceride (10–400). Despite the fact that the catalyst-free supercritical methanol transesterification method is potentially low cost with simple technology, industrialisation has

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not yet taken place. Iijima et al. [147] have proposed a non-catalytic process under supercritical conditions (reaction parameters: T = 643–773 K; p = 20–60 MPa; tr = 4–12 min) for producing an unconventional biodiesel fuel (mainly FAME, mono- and diacylglycerol) without yielding glycerol as a by-product. An alternative, long known method for producing fatty esters from fatty acid glycerides consists of hydrolysis with conversion into a fatty acid followed by esterification (dehydration) with alcohol in anhydrous conditions, i.e.: CH 2 -OOCR1 CH 2 OH | | hydrolysi hydr hydrolys olysiiss CH-OOCR 2 + 3H 2 O æææ Æ 3R iCOOH + CH-OH | | CH 2 OH CH 2 -OOCR 3 esterification

RCOOH + R ¢OH ææææ Æ RCOOR ¢ + H 2 O

7.11

7.12

This is a scarcely used production method due to a low reaction rate. However, several recent patents [116, 117] describe biodiesel production from (rendered) oils and fats based on hydrolysis-(trans)esterification in the absence of a catalyst. Saka and Fukuzono [116] and Saka [117] have pointed out the benefits of hydrolysis-(trans)esterification by conducting the reaction under specific conditions of co-existence of alcohol and/or water with raw material fats and oils. Glycerides are then hydrolysed and/or transesterified and fatty acids contained in the fats and/or produced by (partial) hydrolysis are converted into FAAEs by esterification, formally: TG, FFA, H 2 O H O O,, ROH ROH æææææ hydrolysis hydrolys is, Æ [FA, FFA, FAAE, GL, H 2 O, ROH] Feedstock 2

(t ns) esterification (tra

ROH, R ROH OH,, H O æ ææ æ Æ esterification este esteri rifi ficatio cation n 2

FAAE, GL, H 2 O End pr produc pro ooduc duct

7.13

Water may be considered here as an acid catalyst for the hydrolysis and esterification reaction. The process may be conducted in one step, typically at 473 to 573 K and 15 to 25 MPa. These reaction conditions are milder than those of the conventional supercritical methanol process. The method, which allows producing FAAEs in high yield even in reaction systems containing free fatty acids and water (waste edible oils, dark oils), takes advantages of the fact that the reaction rate of esterification exceeds that of transesterification (Fig 7.6) at given reaction conditions. According to this process, RSO (TG = 97.5%, FFA = 2.5%) is readily converted into RME in 15 min with 98% yield at 573 K and 20 MPa using molar ratios of MeOH/RSO = 42 : 1 and H2O/RSO = 200 : 1 [117]. The method solves several problems: ∑

There is no need for separation and recovery of catalysts as in the conventional process currently in use.

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∑

There is no excess catalyst consumption due to free fatty acids in the feedstocks. ∑ There is no need for a pre-treatment process for FFA removal. ∑ It avoids the negative effects of water on the transesterification rate. ∑ It lowers the excess amount of alcohol in comparison to the conventional supercritical methanol method. The energy and total cost balance of the proposed method deserves detailed comparison to existing commercial routes for transforming similar cheap raw materials into biodiesel.

7.6

References

[1] U.R. Kreutzer (to Henkel KGaA), Manufacture of fatty alcohols based on natural fats and oils, J. Am. Oil Chem. Soc. 61(2) (1984) 343–8. [2] C.A.W. Allen, K.C. Watts and R.G. Ackmann, Properties of methyl esters of interesterified triacylglycerols, in Liquid Fuel and Industrial Products from Renewable Resources (J.S. Cundiff, ed.), Proc. 3rd Liquid Fuel Conference, Nashville, TN (15–17 Sept. 1996), pp. 73–82. [3] L.C. Meher, D.V. Sagar and S.N. Naik, Technical aspects of biodiesel production by transesterification – a review, Renew. Sustain. Energy Revs. 10 (2006) 248–68. [4] S. Saka and D. Kusdiana, Biodiesel fuel from rapeseed oil as prepared in supercritical methanol, Fuel 80 (2001) 225–31. [5] M.K. Smith (to The Baker Castor Oil Co.), Process of producing esters, US Pat. 2,486,444 (1 Nov. 1999). [6] B. Freedman, E.H. Pryde and T.L. Mounts, Variables affecting the yields of fatty esters from transesterified vegetable oils, J. Am. Oil Chem. Soc. 61 (1984) 1638–43. [7] W.R. Trent (to Colgate-Palmolive-Peet Co.), Process of treating fatty glycerides, US Pat. 2,383,632 (28 Aug. 1945). [8] D. Kusdiana and S. Saka, Kinetics of transesterification in rapeseed oil to biodiesel fuel as treated in supercritical methanol, Fuel 80 (2001) 693–8. [9] D. Nimcevic, R. Puntigam, M. Wörgetter and J.R. Gapes, Preparation of rapeseed oil esters of lower aliphatic alcohols, J. Am. Oil Chem. Soc. 77(3) (2000) 275–80. [10] M. Canakci and J. Van Gerpen, Biodiesel production via acid catalysis, Trans. ASAE 42 (1999) 1203–10. [11] R.C.A. Lago, R.R. Szpiz, F.H. Jablonka, D.A. Pereira and L. Hartman, Extraction and transesterification of vegetable oils with ethanol, Oléagineux 40 (1985) 147–54. [12] P. Erdmann, Investigations of production of rape oil ethyl esters from extracted vegetable oils by ethanol, in Biomass for Energy, Environment, Agriculture and Industry (P. Chartier, A.A.C. M. Beenackers and G. Grassi, eds), Proc. 8th European Biomass Conference, Vienna (3–5 Oct. 1994), Vol. 2, pp. 1165–73. [13] C.L. Peterson, D.L. Reece, R. Cruz and J. Thompson, A comparison of ethyl and methyl esters of vegetable oils as diesel fuel substitutes, in Proc. Alternative Energy Conference, Liquid Fuels from Renewable Resources, Nashville, TN (14–15 Dec. 1992), pp. 99–110.

Transesterification processes for biodiesel production

315

[14] E. Bikou, A. Louloudi and N. Papayannakos, The effect of water on the transesterification kinetics of cotton seed oil with ethanol, Chem. Engng. Technol. 22 (1999) 70–5. [15] R. Stern, G. Hillion, P. Gateau and J.-C. Guibet (to IFP), Process for manufacturing a composition of fatty acid esters useful as gas oil substitute motor fuel with hydrated ethyl alcohol and the resultant esters composition, US Pat. 4,695,411 (22 Sept. 1987). [16] J.M. Encinar, J.F. González, J.J. Rodriguez and A. Tejedor, Biodiesel fuels from vegetable oils: transesterification of Cynara cardunculus L. oils with ethanol, Energy Fuels 16 (2002) 443–50. [17] R.A. Korus, D.S. Hoffman, N. Bam, C.L. Peterson and D.C. Drown, Transesterification process to manufacture ethyl ester of rape oil, in Proc. 1st Biomass Conf. of the Americas: Energy, Environment, Agriculture and Industry, NREL, Golden, CO (30 Aug.–2 Sept. 1993), Vol II, pp. 815–26. [18] C.N. Khalil and L.C.F. Leite (to Petrobras), Process for producing biodiesel, PCT Int. Appl. No. WO 2005/030911 A2 (7 Apr. 2005). [19] M.I. Al-Widyan and A.O. Al-Shyoukh, Experimental evaluation of the transesterification of waste palm oil into biodiesel, Bioresour. Technol. 85 (2002) 253–6. [20] G. Kildiran, S.Ö. Yücel and S. Türkay, In-situ alcoholysis of soybean oil, J. Am. Oil Chem. Soc. 73(2) (1996) 225–8. [21] B. Selmi and D. Thomas, Immobilized lipase-catalyzed ethanolysis of sunflower oil in a solvent-free medium, J. Am. Oil Chem. Soc. 75 (1998) 691–5. [22] H. Gunnlaugsdottir, K. Wannerberger and B. Sivik, Alcoholysis and glyceride synthesis with immobilized lipase on controlled-pore glass of varying hydrophobicity in supercritical carbon dioxide, Enzyme Microb. Technol. 22 (1998) 360–7. [23] H. Gunnlaugsdottir, M. Järemo and B. Sivik, Process parameters influencing ethanolysis of cod liver oil in supercritical carbon dioxide, J. Supercrit. Fluids 12(1) (1998) 85–93. [24] M.I. Al-Widyan, G. Tashtoush and M. Abu-Qudais, Utilization of ethyl ester of waste vegetable oils as fuel in diesel engines, Fuel Proc. Technol. 76 (2002) 91–103. [25] A.W. Schwab, M.O. Bagby and B. Freedman, Preparation and properties of diesel fuels from vegetable oils, Fuel 66 (1987) 1372–8. [26] L.M. Du Plessis, J.B.M. De Villiers and W.H. Van der Walt, Stability studies on methyl and ethyl fatty acid esters of sunflowerseed oil, J. Am. Oil Chem. Soc. 62 (1985) 748–52. [27] R. Stern, G. Hillion, P. Gateau and J.-C. Guibet, Preparation of methyl and ethyl esters from crude vegetable oils and soapstock, Proc. World Conf. Emerging Technol. Fats Oils Ind., Cannes (4–10 Nov. 1985), pp. 420–2. [28] H.A. Aksoy, I. Beceric, F. Karaosmanoğlu, H.C. Yatmaz and H. Civelekoğlu, Utilization prospects of Turkish raisin seed oil as an alternative engine fuel, Fuel 69 (1990) 600–3. [29] W. Zhou, S.K. Konar and D.G.B. Boocock, Ethyl esters from the single-phase base-catalyzed ethanolysis of vegetable oils, J. Am. Oil Chem. Soc. 80 (2003) 367–71. [30] N. Bam, Process Development of Rapeseed Oil Ethyl Ester as a Diesel Fuel Substitute, M.Sc. Thesis, University of Idaho, Moscow, ID (1991). [31] N. Bam, D.C. Drown, R. Korus, D.S. Hoffman, T.G. Johnson and J.M. Washam

316

[32]

[33] [34]

[35]

[36] [37] [38]

[39] [40] [41] [42]

[43]

[44] [45] [46] [47]

[48]

[49] [50]

Biodiesel science and technology (to Idaho Research Foundation), Method for purifying alcohol esters, US Pat. 5,424,467 (13 June 1995). S.M. Plentz Meneghetti, M.R. Meneghetti, C.R. Wolf, E.C. Silva, G.E.S. Lima, M. de A. Coimbra, J.I. Soletti and S.H.V. Carvalho, Ethanolysis of castor and cottonseed oil: a systematic study using classical catalysts, J. Am. Oil Chem. Soc. 83 (2006) 819–22. G.F. Zagonel, P. Peralta-Zamora and L.P. Ramos, Multivariate monitoring of soybean oil ethanolysis by FTIR, Talanta 63 (2004) 1021–5. M.J. Nye and P.H. Southwell, Esters from rapeseed oil as diesel fuel, Proc. Vegetable Oil as Diesel Fuel Seminar III, Northern Agricultural Energy Center, Peoria, IL (1983), pp. 77–83. A. Isler, M. Tuter and F. Karaosmanoğlu, Ethyl ester obtained from Turkish originated canola oil and fuel ethanol as an alternative diesel fuel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). G. Knothe, Historical perspectives on vegetable-oil based diesel fuels, Inform 12 (2001) 1103–7. R. Kalscheuer, T. Stölting and A. Steinbüchel, Microdiesel: Escherichia coli engineered for fuel production, Microbiol. 152 (2006) 2529–36. K. Rethmann (to Recyclat Tierischer Rohstoffe GmbH), Verfahren zur Herstellung von Biodiesel mit verbesserter Kältestabilität, Germ. Pat. DE 10,245,758 (1 Oct. 2002). G. Knothe, Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters, Fuel Proc. Technol. 86 (2005) 1059–70. W.B. Wheeler, Refrigerant system lubricant and method, US Pat. 5,750,046 (12 May 1998). R.W. Killick (to Victorian Chemical Co.), Corn drying compositions, US Pat. 5,049,192 (17 Sept. 1991). N. Kosaric and F. Vardar-Sukan, Potential source of energy and chemical products, in The Biotechnology of Ethanol Classical and Future Applications (M. Roehr, ed.), Wiley-VCH, Weinheim (2001), p. 182. A. Salis, M. Pinna, M. Monduzzi and V. Solinas, Biodiesel production from triolein and short chain alcohols through biocatalysis, J. Biotechnol. 119 (2005) 291–9. J.M. Encinar, J.F. González, E. Sabio and M.J. Ramiro, Preparation and properties of biodiesel from Cynara cardunculus L. oil, I&EC Res. 38 (1999) 2927–31. B. Freedman, R.O. Butterfield and E.H. Pryde, Transesterification kinetics of soybean oil, J. Am. Oil Chem. Soc. 63 (1986) 1375–80. A. Srivastava and R. Prassad, Triglycerides-based diesel fuels, Renew. Sustain. Energy Revs. 4 (2000) 111–33. H. Noureddini, D. Harkey and V. Medikonduru, A continuous process for the conversion of vegetable oils into methyl esters of fatty acids, J. Am. Oil Chem. Soc. 75 (12) (1998) 1775–83. D.G.B. Boocock, Single-phase process for production of fatty acid methyl esters from mixtures of triglycerides and fatty acids, PCT Int. Appl. No. WO 2001/012581 (22 Feb. 2001). M.A. Dasari, M.J. Goff and G.J. Suppes, Noncatalytic alcoholysis kinetics of soybean oil, J. Am. Oil Chem. Soc. 80 (2003) 189–92. M.J. Haas and K.M. Scott, Diesel fuel as a solvent for the lipase-catalyzed alcoholysis of triglycerides and phosphatidylcholine, J. Am. Oil Chem. Soc. 73 (1996) 1497–504.

Transesterification processes for biodiesel production

317

[51] J. Van Gerpen, Biodiesel processing and production, Fuel Proc. Technol. 86 (2005) 1097–107. [52] H. Noureddini and D. Zhu, Kinetics of transesterification of soybean oil, J. Am. Oil Chem. Soc. 74 (1997) 1457–63. [53] W. De Greyt, A.J. Dijkstra and M. Kellens, Effect of feedstock composition on the biodiesel and glycerol yield and methanol consumption: a theoretical approach, Building Biodiesel, Biorenewable Resources No. 2 (2007) 9–12. [54] W. De Greyt, J. Maes, F. Soragna and M. Kellens, Processing pathways to an improved yield and quality of biodiesel from vegetable oils and animal fats, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [55] C. Stavarache, M. Vinatoru, R. Nishimura and Y. Maeda, Fatty acids methyl esters from vegetable oil by means of ultrasound energy, Ultrason. Sonochem. 12 (2005) 367–72. [56] D.G.B. Boocock, S.K. Konar, V. Mao and H. Sidi, Fast one-phase oil-rich processes for the preparation of vegetable oil methyl esters, Biomass Bioen. 11 (1996) 43–50. [57] D.G.B. Boocock, S.K. Konar, V. Mao, C. Lee and S. Buligan, Fast formation of high-purity methyl esters from vegetable oils, J. Am. Oil Chem. Soc. 75 (1998) 1167–72. [58] M. Mittelbach and B. Trathnigg, Kinetics of alkaline catalysed methanolysis of sunflower oil, Fat Sci. Technol. 92 (1990) 145–8. [59] G. Vicente, M. Martínez, J. Aracil and A. Esteban, Kinetics of sunflower oil methanolysis, I&EC Res. 44 (2005) 5447–54. [60] D. Darnoko and M. Cheryan, Kinetics of palm oil transesterification in a batch reactor, J. Am. Oil Chem. Soc. 77 (2000) 1263–7. [61] K. Komers, F. Skopal, R. Stloukal and J. Machek, Kinetics and mechanism of KOH-catalyzed methanolysis of rapeseed oil for biodiesel production, Eur. J. Lipid Sci. Technol. 104 (2002) 728–37. [62] M. Diasakou, M. Louloudi and N. Papayannakos, Kinetics of the non-catalytic transesterification of soybean oil, Fuel 77 (1998) 1297–302. [63] S.K. Karmee, P. Mahesh, R. Ravi and A. Chadha, Kinetics study of base-catalyzed transesterification of monoglycerides from Pongamia oil, J. Am. Oil Chem. Soc. 81 (2004) 425–30. [64] S.K. Karmee, D. Chandna, R. Ravi and A. Chadha, Kinetics of base-catalyzed transesterification of triglycerides from Pongamia oil, J. Am. Oil Chem. Soc. 83 (2006) 873–7. [65] S. Zheng, M. Kates, M.A. Dubé and D.D. McLean, Acid-catalyzed production of biodiesel from waste frying oil, Biomass Bioenergy 30 (2006) 267–72. [66] C.-W. Chiu, M.J. Goff and G.J. Suppes, Distribution of methanol and catalysts between biodiesel and glycerine phases, AIChE J. 51 (2005) 1274–8. [67] H. Zhou, H. Lu and B. Liang, Solubility of multicomponent systems in the biodiesel production by transesterification of Jatropha curcas L. oil with methanol, J. Chem. Engng. Data 51 (2006) 1130–5. [68] V. Makareviciene, E. Sendzikiene and P. Janulis, Solubility of multi-component biodiesel fuel systems, Bioresour. Technol. 96 (2005) 611–16. [69] A. Abbott, unpublished results (2008). [70] M.A. Portnoff, D.A. Purta, M.A. Nasta, J. Zhang and F. Pourarian (to Carnegie Mellon University), Methods for producing biodiesel, US Pat. Appl. 2005/0274065 A1 (15 Dec. 2005).

318

Biodiesel science and technology

[71] J. Lifka and B. Ondruschka, Einfluss des Stofftransportes auf die Herstellung von Biodiesel, Chem. Ing. Techn. 76 (2004) 168–71. [72] Z. Zhao, Method for producing biologic diesel oil through use of tailings of animal and vegetable oils in high acid number, Chin. Pat. 1,760,336 (19 Apr. 2006). [73] J.D. Hooker, Apparatus and method for the production of fatty acid alkyl ester, US Pat. Appl. 2005/027137 A1 (3 Feb. 2005). [74] A. Breccia, B. Esposito, G. Breccia Fratadocchi and A. Fini, Reaction between methanol and commercial seed oils under microwave irradiation, J. Microwave Power Electromagn. Energy 34 (1999) 3–8. [75] A. Breccia Fratadocchi (to Ipctisa Srl), Processes and device for improving the reactivity of natural triglycerides with microwave radiation, PCT Int. Publ. No. WO 2003/014272 A2 (20 Feb. 2003). [76] L. Bournay, D. Casanave, B. Delfort, G. Hillion and J.A. Chodorge, New heterogeneous process for biodiesel production: a way to improve the quality and the value of the crude glycerin produced by biodiesel plants, Catal. Today 106 (2005) 190–2. [77] C. Mazzocchia, G. Modica, A. Kaddouri and R. Nannicini, Fatty acid methyl esters synthesis from triglycerides over heterogeneous catalysts in the presence of microwaves, C.R. Chimie 7 (2004) 601–5. [78] T.M. Bernard and N.E. Leadbeater, Microwave technology and continuous-flow production, Biodiesel Mag. 4(10) (2007) 94–100. [79] M. Nishikawa, Y. Maeda, J. Takahashi and T. Miyamura (to Microaqua Y.K.), Preparation of high purity biodiesel fuel using electron and cavitation effect with low cost, Jpn. Kokai Tokkyo Koho 2006/104428 (20 Apr. 2006). [80] Hielscher Ultrasound Technology, http://www.ultrasonic-systems.com. [81] C. Stavarache, M. Vinatoru, R. Nishimura and Y. Maeda, Conversion of vegetable oil to biodiesel using ultrasonic irradiation, Chem. Lett. 32 (2003) 716–17. [82] J.A. Colucci, E.E. Borrero and F. Alape, Biodiesel from an alkaline transesterification reaction of soybean oil using ultrasonic mixing, J. Am. Oil Chem. Soc. 82 (2005) 525–30. [83] M.F. Pelly, Method and apparatus for refining biodiesel, PCT Int. Publ. No. WO 2004/085579 A2 (7 Oct. 2004). [84] S. Gryglewicz, Rapeseed oil methyl esters preparation using heterogeneous catalysts, Bioresour. Technol. 70 (1999) 249–53. [85] N. Ergün and P. Panning (to Energea Umwelttechnologie), Method and system for the esterification of fatty acids, PCT Int. Publ. No. WO 2003/087278 A1 (23 Oct. 2003). [86] M. Kleber and W. Heitzer (to Biodiesel Plants), Verfahren zur kontinuierlichen Herstellung eines als Kraft- und/oder Brennstoff geeigneten Fettsäurealkylestergemisches sowie Verwendung des Fettsäurealkylesters als Kraft- bzw. Brennstoff, Germ. Offenl. DE 10,043,575 A1 (28 March 2002). [87] N. Ergün and P. Panning (to Energea Handels GmbH), Method for producing fatty acid methyl ester and equipment for realising the same, PCT Int. Publ. No. WO 99/26913 (3 June 1999). [88] T. Haas (to Degussa AG), Method for carrying out homogeneously catalyzed reactions, US Pat. 6,392,062 B1 (21 May 2002). [89] J.L. Griggs (to Hydrodynamics, Inc.), Apparatus for heating fluids, US Pat. 5,188,090 (23 Feb. 1993). [90] K. Hudson and B. Kazem (to Hydrodynamics, Inc.), Verfahren zum Mischen

Transesterification processes for biodiesel production

[91] [92]

[93] [94] [95]

[96] [97]

[98] [99] [100] [101]

[102] [103]

[104] [105]

[106] [107] [ 108] [109]

[110] [111]

319

unterschiedlicher Fluiden unter Verwendung mechanisch erzeugter Kavitation, Germ. Pat. DE 60,121,584 T2 (26 July 2007). R. Kotrba, Putting the squeeze on convention, Biodiesel Mag. 5(2) (2008) 67–72. A.P. Harvey, M.R. Mackley and T. Seliger, Process intensification of biodiesel production using a continuous oscillatory flow reactor, J. Chem. Technol. Biotechnol. 78 (2003) 338–41. H. Kurz, The catalytic alcoholysis of fatty oils with alcoholic potash, Fette u. Seifen (1937) 144–5. S. Mahajan, S.K. Konar and D.G.B. Boocock, Standard biodiesel from soybean oil by a single chemical reaction, J. Am. Oil Chem. Soc. 83 (2006) 641–4. H.-J. Kim, B.-S. Kang, M.-J. Kim, Y.M. Park, D.-K. Kim, J.-S. Lee and K.-Y. Lee, Transesterification of vegetable oil to biodiesel using heterogeneous base catalyst, Catal. Today 93–95 (2004) 315–20. S.K. Karmee and A. Chadha, Preparation of biodiesel from crude oil of Pongamia pinnata, Bioresour. Technol. 96 (2005) 1425–9. L. Rodríguez, Á. Pérez, M.J. Ramos, A. Casas and C.M. Fernández, Effect of MTBE as a co-solvent on transesterification of sunflower oil, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). K. Krisnangkura and R. Simamaharnnop, Continuous transmethylation of palm oil in an organic solvent, J. Am. Oil Chem. Soc. 69 (1992) 166–9. G. Suppes, Carbonate catalyzed alcoholysis of triglycerides, US Pat. Appl. 2003/0149289 A1 (7 Aug. 2003). D. Kusdiana and S. Saka, Methyl esterification of free fatty acids of rapeseed oil as treated in supercritical methanol, J. Chem. Engng. Japan 34 (2001) 383–7. T. Sasaki, T. Suzuki and F. Okada (to Sumitomo Chemical Company Ltd), Method for preparing fatty acid esters and fuel comprising fatty acid esters, US Pat. 6,187,939 B1 (13 Feb. 2001). C.A. Fleisher (to Biodiesel Technologies, Inc.), Continuous transesterification process, U.S. Pat. Appl. 2003/0229238 A1 (11 Dec. 2003). A. Demirbaş, Biodiesel production from vegetable oils via catalytic and non-catalytic supercritical methanol transesterification methods, Progr. Energy Combust. Sci. 31(5–6) (2005) 466–87. T. Tateno and T. Sasaki, Process for producing fatty acid esters and fuels comprising fatty acid ester, Eur. Pat. Appl. EP 1,126,011 A2 (15 Feb. 2001). C. Wang, J. Xiao and Y. Wu (to Wuhan Institute of Technology), Process for supercritical preparation of biologic diesel oil, Chin. Pat. 1,594,504 (16 Mar. 2005). S. Saka (to Asahi Chemical Ind.), Ester composition and its production, JP 2000/204392 (25 July 2000). G. Madras, C. Kolluru and R. Kumar, Synthesis of biodiesel in supercritical fluids, Fuel 83 (2004) 2029–33. E. Min, unpublished results. J.M.N. van Kasteren and A.P. Nisworo, A process model to estimate the cost of industrial scale biodiesel production from waste cooking oil by supercritical transesterification, Resour. Conserv. Recycl. 50 (2007) 442–58. Y. Warabi, D. Kusdiana and S. Saka, Reactivity of triglycerides and fatty acids of rapeseed oil in supercritical alcohols, Bioresour. Technol. 91 (2004) 283–7. F. Ma, L.D. Clements and M.A. Hanna, Biodiesel fuel from animal fat. Ancillary studies on transesterification of beef tallow, I&EC Res. 37 (1998) 3768–71.

320

Biodiesel science and technology

[112] D. Kusdiana and S. Saka, Effects of water on biodiesel fuel production by supercritical methanol treatment, Bioresour. Technol. 91 (2004) 289–95. [113] W. Cao, H. Han and J. Zhang, Preparation of biodiesel from soybean oil using supercritical methanol and co-solvent, Fuel 84 (2005) 347–51. [114] J. Ebert, Supercritical methanol for biodiesel production, Biodiesel Mag. 5(4) (2008) 81–5. [115] D.M. Ginosar and R.V. Fox (to Bechtel BWXT Idaho), Process for producing biodiesel, lubricants, and fuel and lubricant additives in a critical fluid medium, US Pat. 6,887,283 (3 May 2005). [116] S. Saka and T. Fukuzono (to Asahi Chemical Ind.), Process for production of fatty acid ester compositions, PCT Int. Publ. No. WO 2004/108873 (16 Dec. 2004). [117] S. Saka (to Kyoto Lonford Development Ltd), Process for producing fatty acid alkyl ester composition, PCT Int. Publ. No. WO 2003/106604 (24 Dec. 2003); US Pat. Appl. 2006/0025620 A1 (2 Feb. 2006). [118] S. Saka and Y. Isayama, Biodiesel production without producing glycerol from oils/fats with using supercritical carboxylate esters, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [119] A.I. Carrapiso and C. García, Development in lipid analysis: some new extraction methods and in situ transesterification, Lipids 35 (2000) 1167–77. [120] S. Özgül and S. Türkay, In situ esterification of rice bran oil with methanol and ethanol, J. Am. Oil Chem. Soc. 70 (1993) 145–7. [121] S. Özgül and S. Türkay, FA monoalkylesters from rice bran oil by in situ esterification, J. Am. Oil Chem. Soc. 80 (2003) 81–4. [122] S. Kildiran, S.Ö. Yücel and S. Türkay, In situ alcoholysis of soybean oil, J. Am. Oil Chem. Soc. 73 (1996) 225–8. [123] S. Siler-Marinkovic and A. Tomasevic, Transesterification of sunflower oil in situ, Fuel 77 (1998) 1389–91. [124] J.U. Obibuzor, R.D. Abigor and D.A. Okiy, Recovery of oil via acid-catalyzed transesterification, J. Am. Oil Chem. Soc. 80 (2003) 77–80. [125] A.P. Harvey, J.G.M. Lee and R. Zakaria, Reaction extraction of biodiesel from rapeseed using methanol, ethanol and methanol/ethanol mixtures, Proc. Int. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [126] F. Avellanedo, J. Salvadó, J. Pasqualino and D. Navarlatz, In-situ transesterification of Cynara cardunculus seeds to obtain biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [127] N.G. Siatis, A.C. Kimbaris, C.S. Pappas, P.A. Tarantilis and M.G. Polissiou, Improvement of biodiesel production based on the application of ultrasound: monitoring of the procedure by FTIR spectroscopy, J. Am. Oil Chem. Soc. 83 (2006) 53–7. [128] R. Andrisano, Grassi, cere, glycerina, saponi e detersivi, in Trattato di Chimica Industriale (M. Giua, ed.), USES, Florence (1976), Vol. 7, pp. 627–959. [129] S.L. Dmytryshyn, A.K. Dalai, S.T. Chaudhari, H.K. Mishra and M.J. Reaney, Synthesis and characterization of vegetable oil derived esters: evaluation for their diesel additive properties, Bioresour. Technol. 92 (2004) 55–64. [130] K.J. Harrington and C. D’Arcy-Evans, Transesterification in situ of sunflower seed oil, I&EC Prod. Res. Dev. 24 (1985) 314–18. [131] K.J. Harrington and C. D’Arcy-Evans, A comparison of conventional and in situ methods of transesterification of seed oil from a series of sunflower cultivars, J. Am. Oil Chem. Soc. 62 (1985) 1009–13.

Transesterification processes for biodiesel production

321

[132] J. Core, New method simplifies biodiesel production, Agric. Res. 53(4) (2005) 13. [133] T.P. Hensarling and T.J. Jacks, Solvent extraction of lipids from soybeans with acidic hexane, J. Am. Oil Chem. Soc. 60 (1983) 783–4. [134] C. Lacaze, Z. Mouloungui, J. Leyris, L.J. Rigal, A. Gaset and F. Silvestre, Method and device for making fatty acid esters from oil-containing seeds, PCT Int. Publ. No. WO 97/38069 (16 Oct. 1997). [135] M.J. Haas, K.M. Scott, A. McAloon, W. Fee, F.T. Barrows and W.N. Marmer, Biodiesel production by the direct transesterification of the lipids resident in biological materials, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [136] M. Torres, V. Loscos, V. Sanahuja and R. Canela, Reactive extraction of acyglycerides using Aspergillus flavus resting cells, J. Am. Oil Chem. Soc. 80 (2003) 347–51. [137] G.J. Suppes, K. Buchwinkel, S. Lucas, J.B. Botts, M.H. Mason and J.A. Heppert, Calcium carbonate catalysed alcoholysis of fats and oils, J. Am. Oil Chem. Soc. 78 (2001) 139–45. [138] H.N. Basu and M.E. Norris (to Agricultural Utilization Research Institute), Process for production of esters for use as a diesel fuel substitute using a non-alkaline catalyst, US Pat. 5,525,126 (31 Oct. 1994). [139] S. Billenstein, B. Kukla and H. Stühler (to Hoechst AG), Verfahren zur Herstellung von Fettsäureestern kurzkettiger Alkohole, Germ. Pat. DE 3421217 A1 (7 June 1984). [140] H. Yoshikawa, T. Sotani, Y. Tanaka and S. Matsuo, Production of biodiesel fuel from vegetable oil by using supercritical methanol, Koatsuryoku no Kagaku to Gijutsu 11 (2001) 109. [141] S. Saka, Biodiesel fuel from vegetable oil, Zairyo 49 (2006) 829–30. [142] K. Bunyakiat, S. Makmee, R. Sawangkeaw and S. Ngamprasertsith, Continuous production of biodiesel via transesterification from vegetable oils in supercritical methanol, Energy Fuels 20 (2006) 812–17. [143] S.-Y. Sun, H.-Y. He, L.-Y. Wang and J.-C. Yang, Production of biodiesel in supercritical methanol, Jingxi Huagong 22 (2005) 916–19. [144] S. Saka, Development of supercritical methanol process for high-quality biodiesel production, Kagaku Kogyo 56 (2005) 897–901. [145] M. Balat, Biodiesel from vegetable oils via transesterification in supercritical ethanol, En. Educ. Sci. Technol. 16 (2005–6) 45–52. [146] R.E. Babcock and B. Schulte, unpublished results (2008); cf. Biodiesel Mag. 5(2) (2008) 22. [147] W. Iijima, Y. Kobayashi and K. Taniwaki, Process for non-catalytically producing biodiesel fuel without yielding by-product, PCT Int. Publ. No. WO 2005/017075 A1 (24 Feb. 2005); U.S. Pat. Appl. 2006/288636 A1 (28 Dec. 2006).

8

Biodiesel catalysis

Abstract: This chapter considers the various aspects of homogeneous and heterogeneous alkaline and acid catalysis of high-quality, low free fatty acids (FFAs) containing feedstocks for transformation of vegetable oils and animal fats into fatty acid alkyl esters (biodiesel). The influence of the most important operating variables affecting fatty acid ester yield are considered. In particular, the effects of FFAs and water on alcoholysis have been investigated. Mechanisms of alkali- and acid-catalysed reactions are described. Acid catalysis is indicated as being essential for transesterification of notoriously difficult triglyceride feedstocks with high FFA and water contents. Key words: Homogeneous biodiesel catalysis, heterogeneous biodiesel catalysis, alkaline biodiesel catalysis, acid biodiesel catalysis, metal biodiesel catalysts.

8.1

Introduction

Unlike petrochemical processes, processes using biomass usually present both low thermal stability and a high degree of functionality, being typically hydrophilic in nature. In this way, those processes need very specific reaction conditions. The compositional characteristics of the feedstock in terms of fatty acid, phosphorus and water content, are quite essential in transesterification reactions. High-quality feedstocks, which are refined and bleached (RB) vegetable oils with ~0.1% free fatty acids (FFA), ~5 ppm phosphorus and ~0.05% moisture, show considerable advantages (Table 8.1). The cost of removal of impurities before transesterification is less than that of removal afterwards, i.e. from the biodiesel and glycerol phases. In order to achieve high ester yields in transesterification of vegetable oils in mild reaction conditions generally a catalyst is needed. Most commonly applied catalysts are alkaline or acidic materials. Typical liquid-phase catalysts used are NaOH, KOH, HCl, H2SO4 and HNO3. Most heterogeneous catalysts may be grouped in five general categories: metallic (metals, transition metal compounds, organometallics and anchored metal complexes), solid bases and acids (including inorganic oxides such as Al2O3, SiO2, SiO2·Al2O3, zeolites, ion-exchange resins, boria, phosphorus oxide, TiO2, ZrO2, chromia, ZnO, MgO, CaO, SnOx), natural catalysts such as coconut or palm ash [1], and enzymes (see Chapter 10). Much research concerning the application of heterogeneous catalysts for biodiesel synthesis has focused on solid-base and enzyme catalysts. 322

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323

Table 8.1 Advantages of high-quality feedstocks in transesterification   Removal of fatty acids:           ∑ FFAs form soaps instead of biodiesel ∑ Soap recovery/disposal increases processing costs ∑ Soaps form a third layer and slow down reaction ∑ Soaps may form an emulsion that must be broken ∑ Greater use of catalyst increases costs ∑ Greater formation of salts and water due to higher amounts of catalyst and acids Removal of phosphorus: ∑ Phosphorus reacts with catalyst, acid and water forming gums ∑ Higher processing costs due to gum recovery/disposal ∑ Higher processing costs due to greater use of catalyst and acids ∑ Gums form a third layer that slows down reaction ∑ Gums may form an emulsion that must be broken Removal of water: ∑ Generates FFAs from TGs and FAME by hydrolysis ∑ Decreased yield ∑ Increased MG/DG in glycerol        

The most important operating variables affecting the fatty acid ester yield are the molar ratio of the reactants (VO : alcohol : catalyst, eventually cosolvent), reaction temperature, pressure and time. As an example, consider the optimisation of sunflower biodiesel production over different types of catalysts (acid and base, homogeneous and heterogeneous) [2]. Table 8.2 shows the experimental conversions to methyl esters in standard reaction conditions (molar ratio MeOH/SNO = 6 : 1, 1 wt% catalyst; 333 K, 0.1 MPa, stirring speed 600 rpm) after 8 h. Optimum values for the variables affecting the process were determined for NaOH by application of factorial design of experiments and response surface methodology. Largest conversions to sunflower oil methyl ester (SNME) were finally obtained at mild temperatures (293–323 K) and high catalyst concentrations (1.3 wt%). A variety of transesterification process intensification efforts has been reported (see Section 7.3.2). Homogeneous alkaline transesterification catalysis of triglycerides is most commonly used, essentially for the reasons given in Table 8.3. An important characteristic of a good alcoholysis catalyst is reduced susceptibility of the catalyst to the composition of the feedstock, which allows the use of less purified (cheaper) feedstocks. Alkali-catalysed alcoholysis works best only for low-acid number feedstock material (so-called refined – and therefore expensive – raw materials). The starting materials used for conventional alkali-catalysed alcoholysis of fats and oils must meet certain specifications [3]. The alkali-catalysed, atmospheric transesterification process may be carried out as long as all starting materials are substantially dry (preferably < 0.06 wt% H2O, including anhydrous alcohol) and free of FFA (below

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Table 8.2 Experimental conversions of SNO to methyl esters for different catalysts (after ref. [2]) Catalyst

Catalyst type

Conversion (%)

NaOH Amberlyst®A26 Amberlyst®A27 Amberlyst®15 MELCat XZO682/01 MELCat XZO645/01 TIS TILCOM STC SnCl2 MgO USY-292 Novozym 435®a

Strongly basic Anion-exchange resin Anion-exchange resin Cation-exchange resin Sulphate doped zirconium hydroxide Silica doped zirconium hydroxide Titanium silicate Titanium chelate Lewis acid Metallic oxide Zeolite Immobilised lipase

100.0 0.1 0.4 0.7 0.0 0.0 0.6 0.5 3.0 11.0 0.2 0.0

a

Candida antarctica.

Table 8.3 Characteristics of homogeneous alkaline transesterification catalysis Advantages: ∑ Proven technology ∑ Low-cost catalysts ∑ High FAME yields at mild reaction conditions (T, p) ∑ High reaction rates (min) ∑ Low alcohol-to-oil ratio ∑ Relatively low investment costs Disadvantages: ∑ Requires expensive, refined vegetable oils or pre-treated fats ∑ Demanding feedstock specifications (FFA < 0.5 wt%; anhydrous reactants) ∑ Catalyst neutralisation/recovery (no catalyst reuse) ∑ High purification costs (need for removal of catalyst residues from ester product) ∑ Need for stainless steel equipment    

0.5 wt%, corresponding to an acid number of the triglyceride of about 1 mg KOH/g). The ester yields are significantly reduced if the reactants do not meet these requirements. The presence of minor amounts of FFA and moisture in the reaction mixture produces soap (Fig. 8.1), which lowers the yield of esters and renders the separation of ester and glycerol as well as water washing difficult. Moreover, FFA consumes catalyst and reduces the catalyst efficiency [4]. Therefore, base-catalysed transesterification requires highly refined oils or pre-treated fats in order to get efficient conversion and is not directly suitable for inexpensive feedstocks containing high levels of FFAs (such as most waste frying oils or grease recovered from waste and wastewater treatment traps). Production of biodiesel from low-acid number used cooking oils (0.42–2.07 mg KOH/g) is feasible by base-catalysed

Biodiesel catalysis O

O + NaOH (or NaOMe)

C

(a) R

325

C

OH

O–

R

Na+

+ H2O (or MeOH)

Soap

O (b)

O

C R

OMe

+ H 2O

Base catalyst

+ MeoH

C R

OH

8.1 (a) Base-catalyst reaction with FFAs to produce soap and water, both undesirable by-products. (b) Water promotes the formation of FFAs. These, in turn, can deactivate the catalyst and produce soap, as in (a) (after ref. [5]).

transesterification [6]. The effects of FFAs and water on the methanolysis of beef tallow over NaOH and NaOCH3 were investigated [7]. Basic (alkali) catalysts are equally not suitable for alcoholysis of microalgal oil, probably also because of the high acid value of the oil (8.97 mg KOH/g) [8]. Parameters influencing the ester conversion by acid-catalysed transesterification are the alcohol/VO molar ratio, amount of catalyst and reaction conditions (T, p, t). Optimal conditions for the acid-catalysed reaction were not recommended. In general, the alcohol/VO molar ratio is associated with the type of catalyst used. Acid-catalysed transesterifications need a higher molar ratio of methanol to oil (30–150 : 1) than base-catalysed systems (typically 6–15 : 1). Acid-catalysed transesterification is also much slower than the base-catalysed reaction and requires more drastic T, p conditions, e.g. 69 h to obtain 90% oil conversion to methyl esters at 338 K and a molar ratio MeOH/SBO = 30 : 1 [9]. With acid catalysts, reaction times up to 240 h are not exceptional. As detailed elsewhere, the mechanisms of alkali- and acid-catalysed reactions are different. The alkali-catalysed reactions are based on an addition-elimination reaction, while the acid-catalysed transesterification reactions can be described by two consecutive substitutions. The alkalicatalysed reactions are of higher rate, while the acid-catalysed reactions can be significantly accelerated by increasing temperature. Because of its low reaction rate acid-catalysed transesterification has largely been ignored commercially. Acid-catalysed transesterification is preferably carried out in the absence of water to avoid formation of carboxylic acids, which reduces the alkyl ester yield. There are also several clear advantages in using an acid catalyst instead of an alkaline catalyst (Table 8.4). Soap formation is avoided and acids catalyse FFA esterification to produce fatty acid alkyl esters (FAAEs), increasing the biodiesel yield. Whereas alkaline catalysts would be destroyed in VOs with FFA > 1%, acid catalysts remain effective. Strong liquid-acid catalysts can

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Table 8.4 Main characteristics of acid-catalysed (trans)esterification Advantages: ∑ Allowance for use of low-cost, highly acidic feedstocks ∑ Simultaneous esterification/transesterification ∑ Short reaction times with FFA ∑ Allows formation of long- or branched-chain esters ∑ No soap formation Disadvantages: ∑ Relatively slow reaction rates ∑ Unfavourable reaction conditions with TG (high T, p, t, alcohol/VO molar ratios) ∑ Formation of secondary products ∑ Inhibited by water ∑ Corrosion-resistant materials required (liquid acids) ∑ Catalyst neutralisation/recovery ∑ Elaborate process engineering

simultaneously conduct esterification and transesterification. Consequently, acid-catalysed processes may produce biodiesel from low-cost feedstocks, lowering production costs. When solid-acid catalysts replace liquid acids, corrosion and environmental problems associated with the latter can be avoided and product purification protocols reduced, significantly simplifying biodiesel production and reducing cost. Approaches for improving the processing of high FFA oils are deacidification or pre-esterification of the free fatty acids to alkyl esters in the presence of a (heterogeneous) acidic catalyst [10]. The pre-treated oils with lowered FFA content (< 0.5 wt%) can then be processed under standard alkali-catalysed reaction conditions [11] (see also Chapter 9). Although acid catalysis is essential for transesterification of the notoriously difficult triglyceride feedstocks with high FFA and water contents [9, 12–15] reaction times are very long (48–96 h), even at the boiling point of the alcohol and with a high alcohol-to-oil molar ratio. The one-step acid-catalysed process is more economical than the alkali-catalysed process, which requires an extra step to convert FFAs to methyl esters, thus avoiding soap formation [13, 16]. Technologically, the large methanol requirement translates into larger transesterification reactors and a larger methanol distillation column. Nevertheless, the acid-catalysed continuous process to produce biodiesel from waste cooking oil is a competitive alternative to the alkaline-based process using virgin vegetable oil both from a technological and economical viewpoint [16, 17]. Recently there has been considerable emphasis on the development of heterogeneous (two-phase) catalysts to produce fatty acid methyl ester (FAME), because their utilisation in the transesterification reaction greatly simplifies downstream operations of the products (separation, purification). Moreover, heterogeneous catalysts do not produce soaps through free fatty

Biodiesel catalysis

327

acid neutralisation and triglyceride saponification. General characteristics of this type of catalyst are slow reaction rates and low product yields. Biodiesel catalysis has been reviewed extensively [5, 18–20].

8.2

Homogeneous alkaline catalysis in biodiesel synthesis

Most commercial biodiesel plants operate with homogeneous alkaline catalysts. Table 8.5 shows a selection of alcoholysis (mainly methanolysis) catalysts for vegetable oils and animal fats. Homogeneous alkaline catalysts used for transesterification of lipids include alkali metals (in alcoholic solution), alkali metal (Na, K) compounds, mainly hydroxides, alkoxides (C1 to C4) and carbonates, as well as the corresponding amides and hydrides [2, 3, 9, 21–33]. Although alkali metal alkoxides are the most effective catalysts [9, 27], alkali hydroxides are often preferred because of lower cost and handling. Another group of homogeneous catalysts is based on transition metal compounds with alkoxy or acyl groups, such as Ti(IV) alkoxides [34]. The application of strong organic bases, in particular alkylguanidines, in transesterification is quite limited [35–38]. These homogeneous catalysts yield high conversion under mild reaction conditions without causing formation of soaps or emulsions. The catalytic activity of substituted alkylguanidines (both cyclic and acyclic) in transesterification of RSO with methanol depends mainly on their intrinsic base strength [36]. The most active non-ionic base catalyst described was commercial 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) which, when used at 1 mol% and with a MeOH/RSO molar ratio of 6.86 : 1, produces 90% rapeseed oil methyl ester (RME) with 1 h of reaction time at 343 K. There is considerable doubt and discussion on the real (homogeneous?) nature of some supposedly heterogeneous transesterification catalytic reactions (see Section 8.4.2). In the three-step reversible base-catalysed alcoholysis of triglycerides (TG), a biodiesel mixture (FAAEs) is obtained by successive attack of an alkoxide species, being the actual catalytic species, on tri-, di- and monoglyceride molecules. Alkoxide anions may be obtained by: dissociation of an alkali alcoholate by dissolution in alcohol; reaction of alkali metal (M = Li, Na, K) and alcohol; or adding an alkali hydroxide or carbonate to an alcohol, as follows:

ROM ´ RO– + M+



M + ROH ´ RO– + M+ + ½ H2(g)

8.1 –

+

8.2



MOH + ROH ´ RO + M + H2O

8.3



M2CO3 + ROH ´ RO– + M+ + HMCO3

8.4

Alcohol

B. carinata oil B. carinata oil B. carinata (HEBC) oil BTW BTW BTWb CNO CNO, PMO, PNO, SBOc CNO, RSO CNO, SBO CO, GCO, PGOd,e, UPGOe CO, LSO, RSO, SNO CSO CSO, PNO, SBO, SNO Cynara oil LSO, OO, SEO, TOf GSO Jatropha curcas oil JO LSO, RSO Mahua oil PMO PMO PNO RBO RSO RSO RSO RSO

MeOH MeOH MeOH MeOH MeOH MeOH MeOH, MeOH MeOH MeOH MeOH MeOH, EtOH MeOH, MeOH, – EtOH MeOH MeOH MeOH MeOH MeOH MeOH EtOH MeOH, EtOH MeOH, MeOH EtOH

Catalyst

KOH KOH KOH NaOH NaOH NaOH, NaOMe EtOH NaOH LiOH, NaOH, KOH NaOH, NaOMe NaOH, NaOMe KOH EtOH, i-PrOH n-BuOH Na, KOH, NaOMe KOH EtOH, BuOH NaOH, NaOMe EtOH NaOH, KOH KOH NaOH NaOH NaOMe KOH KOH NaOH, NaOMe KOH NaOH EtOH, BuOH NaOH, KOH, NaOMe KOH, NaOMe EtOH NaOH, KOH Alkylguanidines (TBD) NaOEt

Oil/Alcohola

Temperature (K) Reference(s)

1 : 2.5 1 : 6 – 1 : 6–1 : 7.5 1 : 11 1 : 6 1 : 7 1 : 24 1 : 3–1 : 6.9 1 : 6–1 : 27 1 : 6 1 : 6 1 : 4–1 : 9 1 : 3–1 : 6 1 : 1.35–1 : 15 1 : 86 1 : 6 1 : 3–1 : 9 1 : 7.5 1 : 3–1 : 8 1 : 6 1 : 5.8–1 : 17 1 : 6 – 1 : 3–1 : 7 1 : 4.2–1 : 5.2 1 : 6 1 : 6.9 1 : 6

303–313 298 298 333 333 335–360 383i 353–453i 348 296 298 298–378 351 >333 298–348 293 351 303–333 338 333–338 333 333 333 323 303–333 ≥ 293 298 343 353

[39] [40] [41] [42, 43] [44] [45–47] [48] [49] [50] [4] [51] [52] [53] [9] [54, 55] [56] [57] [58] [59] [60, 61] [62] [63] [64] [22] [29] [65, 66] [67] [36] [68]

Biodiesel science and technology

Raw material

328

Table 8.5 Homogeneous base-catalysed transesterification of vegetable oils and animal fats        

RSO RSO SBO SBO SBO SEO SNO SNO SNO VOs, WVOs VOs, WVOsg WFO WOOh WOO, WPO (W)CO, VO

MeOH MeOH MeOH, MeOH, MeOH MeOH MeOH MeOH MeOH MeOH MeOH, MeOH MeOH, MeOH MeOH

BuOH BuOH

EtOH (90%) EtOH

KOH 1 : 6 NaOH 1 : 0.95–1 : 3.5 NaOH, NaOMe 1 : 6–1 : 30 NaOH, NaOMe, NaOBu 1 : 6 Alkylguanidines 1 : 7 NaOH 1 : 6 KOH 1 : 3 NaOH, KOH 1 : 1.7 NaOH, KOH, NaOMe, KOMe 1 : 6 KOH, KOMe 1 : 3 aq. NaOH, KOH 1 : 3–1 : 9 KOH 1 : 4.8 NaOH, KOH 1 : 3.5 KOH 1 : 1 NaOH 1 : 6

313 343 293–333 293–313 343 333 343 323–343 338 293 293 338 298 313–333 333

[69] [28] [12] [27] [70] [71] [72] [73] [74] [75] [76] [5] [77] [78] [17]

a

Molar ratio. FFA contents :  0.27%. c Plug flow reactor. d Processed waste fryer grease containing citric acid. e High FFA contents. f Tung oil. g Up to 20% FFA. h FFA contents :  2.76% and 4.33%. i Under pressure. b

Biodiesel catalysis 329

330

Biodiesel science and technology

The latter system actually yields a heterogeneous catalyst. The accepted mechanistic route for alkali-catalysed transesterification (Fig. 8.2) then consists of the following sequence of steps: generation of the catalytically active species, RO–, according to Eqns 8.1–8.4; ∑ nucleophilic attack of the alkoxide ion on a carbonyl carbon in TG; ∑ splitting of the intermediate anion formed into a fatty acid alkyl ester (FAAE) and a diglyceride (DG) anion; and ∑ regeneration of the catalytically active species RO– by proton transfer to the diglyceride ion.

∑

In a similar way, DG is converted first to a monoglyceride (MG) intermediate and finally to glycerol [38]. Alcoholysis of vegetable oils can take place without catalysts at high pressures (up to 9 MPa) and temperatures (up to 533 K) or, alternatively, at low pressure (0.1–1 MPa) and temperatures (< 373 K) using an alkaline catalyst. Typical process conditions for homogeneous base catalysis are moderate: stoichiometric alcohol/oil molar ratio (or slightly higher), reaction at alcohol reflux temperature, atmospheric pressure or small overpressure, low reaction times (typically 1 h) and low catalyst concentration (see Table 8.6). Such reaction conditions may be derived from various optimisation studies [2, 77], which concern mainly catalyst type and concentration (0–2 wt%), nature of alcohol and alcohol/VO molar ratio (3 : 1–9 : 1), reaction temperature (298–338 K), and pressure (atmospheric), reaction time (< 2 h) and stirring time (0–60 sec). A typical optimisation process may be carried out following the order and values of Fig. 8.3. Knothe et al. [79] reported the optimal conditions for base-catalysed alcoholysis of high-purity O–

O + RO–

C R1

R1

C

OR¢

OR

TG O– R1

C

OR¢

O OR¢

OR R¢O– + ROH DG anion

+ R¢O–

C R1

FAAE

OR

R¢OH + RO– DG

R = alkyl group of the alcohol, R¢ = fatty acid residue, R1 = fatty acid alkyl group

8.2 Mechanism of alkali-catalysed transesterification of triglycerides.

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331

Table 8.6 Typical reaction conditions for biodiesel synthesis using homogeneous base catalysts Feedstocks Refined triglycerides (FFA < 0.5 wt%; H2O < 0.06 wt%) Anhydrous short-chain alcohols (generally methanol) Oil/alcohol molar ratio 1 : 3–1 : 9 (usually 1 : 6) VO/co-solvent molar ratio 0.2–0.4 Temperature 293–348 K (usually 333–338 K) Pressure 0.14–0.41 MPa Catalyst NaOH (most common) Catalyst concentration 0.25–2 wt%   (oil basis) Stirring speed 300–600 rpm   Reaction time 1–4 h (usually 1 h) for > 98% conversiona a

0.1 h in presence of co-solvents.

Catalyst amount (%) (0 … 1.9)

Distilled water amount (mL) (0 … 20; 1-2 steps)

Alcohol amount (%) (0 … 18)

Reaction temperature (K) (273 … 343)

Pour off time (h) (0 … 168)

Reaction time (min) (0 … 60)

8.3 Optimisation process for specification of homogeneous alkaline transesterification reaction conditions.

feedstocks with 97.7% conversion in 18 min as 1 wt% KOH at 342 K and an alcohol-to-oil molar ratio of 7 : 1. Optimised experimental conditions for alkali-catalysed biodiesel production of Jatropha curcas oil have also been reported [58]. The primary advantage of higher temperature is shorter reaction times. Table 8.7 shows the results of continuous plug-flow transesterification of various triglycerides with a single-pass residence time as low as 45 sec and conversion to methyl ester product of at least 90% at T = 353–453 K and p ≤ 3 MPa. However, reaction temperatures above 333 K are generally to be avoided because they tend to accelerate the saponification of glycerides by the alkaline catalyst before completion of the alcoholysis, which is undesirable [77, 80]. In fact, to decrease costs, transesterification should preferably be carried out at ambient temperature and atmospheric pressure. Alcohol optimisation concerns both the condition and alcohol/oil molar ratio. An example of alkali-catalysed methanolysis is a 6 : 1 molar ratio MeOH/PMO, 0.5–1 wt% NaOH (based on oil), 333 K (methanol reflux temperature) and 0.4 MPa, leading to 94–99% vegetable oil ester yield [63]. Alcohol amounts close to stoichiometry, such as alcohol/oil molar ratio of 6 : 1, maintain the advantage of the natural separation of the glycerol by-

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Table 8.7 Continuous plug-flow transesterificationa of vegetable oils using alkali hydroxide catalysis (after ref. [81]) Triglyceride

Catalyst

T (K)

p (MPa)

Conversion (%)b

OO CRO LSO RSO PMO CNO SBO CSO PNO SFO CAS

LiOH NaOH NaOH KOH NaOH NaOH KOH LiOH NaOH KOH LiOH

353 363 373 383 393 403 413 423 433 443 453

0.4 0.5 0.6 0.7 0.9 1.1 1.3 1.6 2.0 2.4 2.9

>99 >99 >99 >99 >99 >99 >90 >90 >95 >95 >95

a

0.5 inch diameter, 30 foot length coiled copper tube plug-flow reactor with 0.2 MPa overpressure imposed upon reactants and products. b Methyl esters.

product at the bottom of the reactor, whereas for a larger excess of alcohol the glycerol either does not separate or moves into an alcohol-rich upper phase. The result is a decreased ester yield and impaired product quality. Base-catalysed procedures generally do not require a high excess of alcohol, are simple and only relatively time consuming. Although increased homogeneous catalyst concentrations accelerate the overall reaction rate, excessive catalyst amounts may result in smaller ester yields due to presence of soaps, avoiding ester separation. Lower homogeneous catalyst loadings reduce catalyst costs and waste generation. In addition, homogeneous catalysts tend to be more robust because a fresh charge of catalyst is used each time, thus avoiding deactivation problems possible with reused heterogeneous catalysts. When heterogeneous and homogeneous catalysts allow similar batch times, the homogeneous catalyst can avoid the often high costs of the heterogeneous catalysts. Base-catalysed processes are also strongly affected by mixing of the reactants and/or by efficient heating that produces tiny droplets, thus increasing the reaction area [31, 43]. The reaction time remarkably increases without stirring reagents and oil (homogenisation). Mixing/heating is the process of choice used in industrial application in over 85 biodiesel plants worldwide (data from 2000). The reaction rate can also be enhanced by the use of a non-reactive anhydrous co-solvent, which changes the two-phase nature of the (methanolysis) process into one-phase. Yet, there are several problems associated with alkaline catalysis. Traditional biodiesel ‘catalysts’ (NaOH, KOH) are better described as chemical reactants rather than catalysts, because they are consumed during the production process and must be washed out of the biodiesel crude. Alkaline-catalysed

Biodiesel catalysis

333

transesterification is incompatible with the presence of free fatty acids (FFA < 0.5 wt%) and water (H2O < 0.06 wt%) (see also Fig. 8.1). For example, these specifications were necessary for effective base-catalysed transesterification of beef tallow [6]. Anhydrous reaction conditions are ideal. Transesterifications should therefore be carried out with substantially anhydrous alcohols, which is particularly problematic for ethanol. The presence of water causes a partial reaction change to saponification, which produces soap. Soap may be created in biodiesel production even when starting with refined vegetable oil, resulting in significant yield loss. In fact, some catalysts, notably alkali hydroxides, especially when added in amounts higher than 1.4–1.5%, form some water by reaction with the alcohol (see Eqn 8.3) [27]. While some formation of soap is beneficial as it acts as a phase transfer catalyst, thus assisting mixing of the reactants, soap consumes the catalyst and reduces catalyst activity, causing a decrease in overall yield and an increase in viscosity, gel formation and difficulty in separation of glycerol. Care should be taken to avoid reaction of the ester with the partially dissolved glycerol, which would lead to the undesired formation of monoglycerides. The resulting raw glycerol from the base-catalysed esterification process is contaminated with alcohol, base (NaOH), inorganic salts and unreacted organic materials, which dramatically degrades its commercial value. Besides interference of water and FFAs with the reaction, conventional alkali-based processes have several other drawbacks: they are energy intensive, recovery of glycerol is difficult, the catalyst has to be removed from the product, and lots of alkaline wastewater is produced which requires treatment. The overall process thus includes transesterification reaction, recovery of unreacted alcohol, purification of fatty acid alkyl esters from catalyst, and neutralisation and concentration to recover glycerol as a co-product. Figure 11.4 shows a simplified block flow diagram for a typical base-catalysed process for the production of biodiesel from refined vegetable oil. In order to achieve the specifications that are desired for glycerol and the ester, it is necessary to resort to many work-up stages that are economically viable only for large scale operations. These problems are largely overcome by heterogeneous spinel-type catalysts [82]. Although use of strong organic bases has also been reported, production of low-cost biodiesel by homogeneous alkaline transesterification processes at atmospheric pressure is confined mainly to the use of alkali catalysts (especially hydroxides), because the reaction times are relatively short, the reaction conditions are gentle, and the prices of catalysts used are low. Alcoholates and alkali metals enable high conversions but are less attractive industrially in view of relatively high costs, inconvenience and safety risks involved in using (sodium) metal to produce alcoholates. Basic alkoxides only contain OH– as an impurity and therefore do not produce soap through triglyceride saponification. Figure 7.1 shows that the degree of transesterification of sunflower oil (SNO) with methanol using a NaOCH3 catalyst depends on

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Biodiesel science and technology

the alcohol-to-oil ratio [9]. Significant amounts of partially reacted MGs and DGs will be present at low MeOH/SNO ratios. Mono- and diglycerides of saturated fatty acids crystallise easily from biodiesel fuel and can cause fuel filter plugging. The figure shows that a molar ratio MeOH/SNO = 6 : 1 is required for a complete single-step reaction. Alkali hydroxides are cheap (NaOH being less expensive than KOH), readily available and easy-to-handle alternatives [3, 24, 83], which form alkoxide ions in an equilibrium reaction with the hydroxide ions. The Brönsted bases like NaOH and KOH are widely used for alcoholysis. Metal hydroxide solutions in methanol are used mainly as catalysts in small production units (up to 5 kt/yr). Metal alkoxides, though more costly than metal hydroxides, offer advantages in terms of handling and safety and yield purer glycerol by-product. They are considered the catalyst of choice in larger commercial plants (> 5kt/yr) [84]. Vertellus Specialties Inc. (Indianapolis, IN) and InChem Corp. (Rock Hill, SC) are North American producers of Na- and K-methylate. DuPont’s sodium methylate solution capacity in three US plants has tripled since May 2007. At least two more production facilities are planned for 2008. Evonik Degussa Corp. operates the largest Na- and K- methylate solution plant (60 kt/yr) outside of Germany in Mobile (AL) for the American markets. BASF has recently set up a 60 kt/yr facility in Guaratinguetá (Brazil) for the South American biodiesel market. NaOH as a base catalyst is corrosive to equipment (though less than acid catalysts). In accordance with Eqn 8.3, when using hydroxides, small amounts of soap are expected to be produced due to the formation of water in the initial stages of the reaction (formation of RO– species). Consequently, there are yield losses of alkyl esters due to triglyceride saponification and methyl ester dissolution in the lower glycerol phase, which typically amounts to 3 and 6 mol% after KOH- and NaOH-catalysed methanolysis of SNO, respectively [74]. Formation of soap translates into catalyst deactivation and loss of productivity. As for a typical solution (e.g. 0.1 mol NaOH in 99% EtOH), 96% of the total base is present in the form of the alkoxide ion [85], undesirable alkali-catalysed hydrolysis and irreversible soap formation according to

RCOOR¢ + NaOH Æ RCOONa + R¢OH

8.5

plays only a minor role in a water-free medium consisting of vegetable oil and alcohol. KOH has been described as being a superior catalyst in the production of biodiesel. KOH is rarely used in the US industry but is a more popular catalyst than NaOH in Europe [84]. The decreased tendency for soap formation observed with KOH instead of NaOH reduces the amount of methyl esters dissolved in the glycerol phase and thus counters ester losses [83]. The waste stream of KOH has economic value as a fertiliser. With this

Biodiesel catalysis

335

catalyst the end product can be neutralised with phosphoric acid to produce potassium phosphate. In a typical case, optimised conditions for methanolysis of high-erucic B. carinata (HEBC) oil were reported as 298 K and 1.2–1.5 wt% KOH [41]. In waste olive oil (WOO) alcoholysis, better results were obtained using KOH/MeOH instead of NaOH/EtOH [77]. Maximum methyl ester yield was achieved already after 1 min of reaction. Results contradict those obtained by Du Plessis et al. [86] who found no (ethyl) ester production after 1 min of reaction of SNO, but needed at least 4 h to achieve 87% ester production. Using different catalyst systems other workers reported maximum conversions between 5 min and 48 h [15, 87, 88]. Alcoholysis of WOO with KOH proceeded more slowly with ethanol than using methanol [77]. Also Du Plessis et al. [86] reported better performance of MeOH than EtOH in the alcoholysis of SNO. Potassium hydroxide-catalysed alcoholysis of crambe and camelina oils with long-chain alcohols (oleylalcohol, n-octanol) yields wax esters for cosmetic use as a low-cost substitute for jojoba (Simmondsia chinensis) wax esters [89]. Vicente et al. [74] have compared different homogeneous catalyst systems (NaOH, KOH, NaOCH3, KOCH3) for sunflower diesel production. In the purification process soaps were removed as well as catalyst and methanol traces, and free glycerol present in the ester phase. The biodiesel purity was near 100 wt% for all catalysts. Near 100 wt% biodiesel yields were obtained only with the methoxide catalysts because of negligible yield losses due to triglyceride saponification and methyl ester dissolution in glycerol [74]. However, methoxide catalysts are more expensive than hydroxides and more difficult to manipulate since they are very hygroscopic. The reactions using NaOH were the fastest. Potassium methoxide works better with animal fats than sodium methoxide as it keeps the soap in glycerol in liquid form, achieves better phase separation and promotes better reaction. US Patent No. 5,399,731 to Wimmer [90] discloses that alcoholysis of various triglycerides can be performed using C1-C5 monoalcohols in the presence of basic catalysts at 278–313 K. The preferred catalysts are NaOH or KOH or the corresponding alcoholates. Base catalysis (NaOH, KOH) has also been used for the production of biodiesel by reacting a branched monohydric alcohol with a fat having a low unsaturated fatty acid content [91]. Whereas KOH and NaOCH3 were equally capable as base catalysts for methyl ester synthesis from various vegetable oils (CO, LSO, RSO, SNO) even at ambient temperatures, only NaOCH3 was effective in the production of ethyl, 2-propyl and butyl esters, because of weaker acidity of the relevant alkanols in comparison to water (cf. the pKa values for methanol, water and ethanol of 15.5, 15.7 and 15.9, respectively) [52]. Branched-chain alcohol such as 2-propanol is even less acidic. Therefore, while the reaction of KOH with methanol favours formation of the methoxide ion, the reactivity

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Biodiesel science and technology

between KOH and other alcohols, such as 2-propanol, to form the respective alkoxide anion, is very low. In other words, whereas KOH is an excellent base catalyst for methyl esters, it becomes less effective for ethyl, 2-propyl and butyl esters. 2-Propyl and butyl esters of CO and LSO were prepared using sodium metal as a catalyst [52]. In some cases high alcohol-to-oil ratios (66 : 1) have been reported for the preparation of 2-propyl and 2-butyl esters [92]. Alkaline carbonates reduce the impact of soap formation by forming bicarbonates instead of water by interaction with the alcohol (Eqn 8.4). However, the carbonate anion is a weaker base, which determines lower concentrations of RO- species as well as lower reaction rates, and thus requires higher amounts of carbonate catalyst (2–3 wt%) to achieve yields comparable to those obtained with alkoxide or hydroxide catalysts. To account for catalyst deactivation the FFA and water contents of the feedstock have to be determined before transesterification [93]. The reactant purity requirement limits the use of waste cooking oils (usually having FFAs > 2 wt%) in alkali-based catalysis. This problem may be overcome by deacidification or an acid-catalyst pre-treatment (esterification) step to obtain the required low levels of free fatty acids (< 0.5 wt%) [9]. This obviously adds to the overall process cost. It is also important to keep the water content of used cooking oils as low as possible [93]. Whereas typical optimum concentrations of homogeneous alkali catalysts are 0.5–1.0 wt% (oil basis) [9], higher concentrations are needed in the case of high amounts of free fatty acids in the feedstock [93, 94]. However, this determines a significant amount of methyl esters in the glycerol phase after separation [31]. Transesterification with methanol of several VOs with FFA content of up to 2.8% has been observed to proceed very rapidly using strongly basic homogeneous catalysts [30]. Nye et al. [25] described transesterification of used frying oils with excess of a variety of alcohols under both acidic and basic conditions. The best result was obtained using KOH/methanol. Dorado et al. [77, 78] described an alkali-catalysed transesterification process for high-FFA waste oils (palm and olive oils, hydrogenated fats). The process was carried out in two steps, using a stoichiometric amount of methanol and the necessary amount of KOH, supplemented with the exact amount of KOH to neutralise acidity. Both reactions were completed in 30 min at 313 to 333 K. To carry the reaction to completion, FFA < 3% is needed. Both excess as well as insufficient amount of catalyst may cause soap production. The two-step transesterification process (without any costly purification step) is an economic method for biofuel production using waste vegetable oils. Dmytryshyn et al. [51] described use of base catalysts in the conversion of canola oil, greenseed canola oil (GCO) from heat-damaged seeds, acid-rich processed waste fryer grease (PGO) and unprocessed waste fryer grease (UPGO) with KOH, merely as an evaluation of biodiesel additive properties.

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337

Artificial neural network (ANN) modelling was successfully applied to the optimisation of biodiesel yield of waste olive oil/methanol varying oil : methanol : KOH catalyst amounts, reaction time and temperature [95]. ANN is a valid alternative to extensive laboratory testing. The kinetics of the alkali-catalysed transesterification of soybean oil has been studied [12, 96]. The reaction rate constants for the alkali-catalysed reaction are much higher than those for the acid-catalysed reaction; rate constants increase with catalyst amount [12]. Sodium alkoxides, KOH and NaOH, are the most efficient catalysts used for this purpose. They require only short times (30 min) to complete the reaction even at room temperature, while acid catalysts, such as H2SO4, require higher temperatures (373 K) and longer reaction times (3–4 h) [9, 97, 98]. With homogeneous alkaline catalysts, values near final conversion are reached already in the first 10 min [54]. Subsequently, further displacement of the equilibrium toward the formation of esters is very slow, even in the presence of an excess of alcohol. Ways of improving the process are to withdraw the glycerol from the reaction medium as soon as it is formed, and to carry out successive transesterifications until reaching complete conversion to the esters. A multi-stage transesterification process allows lower alcohol/oil molar ratios. This principle is the basis of a Henkel industrial process for methyl ester production, which is carried out in a two-stage reaction with separation of glycerol after each stage [50]. As vegetable oil and methanol are immiscible, these reactants initially form a multi-phase oil/methanol/catalyst system. Accordingly, the transesterification reaction is diffusion-controlled with poor diffusion between the phases resulting in a slow rate. In the homogeneous catalyst system, NaOH acts as a solvent mixing the reactants. Transesterification takes place on the interface of the reactants. In the classical methoxide base-catalysed transesterification of SBO at 313 K, methanolysis occurs only in the methanol phase [27]; low oil concentration in methanol causes initially a slow reaction rate. In such cases, addition of an appropriate co-solvent (THF, DMSO or hexane [4, 27]) to minimise mass transfer resistance changes an immiscible two-phase system into a homogeneous oil-dominant one-phase emulsion state in which methanolysis speeds up considerably. Reaction time replaces the effect of mixing when two reactants (VO and NaOH/MeOH) become homogeneous in a very short time. In conventional homogeneous base-catalysed processes a single phase between the heavy alcohols, ester and glycerol is formed after the reaction, so that it is not possible to easily decant the glycerol and thus to obtain good conversion in a single stage. In that case, the process is complex. Not only is it necessary to ensure an intermediate decanting of glycerol with evaporation of the alcohol, but also to purify the ester and the final glycerol. Less steps are generally required by using heterogeneous zinc catalysts [82]. Table 8.3 summarises the main characteristics of homogeneous alkali-

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catalysed alcoholysis of triacylglycerides. Base-catalysed transesterification is basically terminated within 1 h and less corrosive to process equipment than acid-catalysed processes, which makes it more applicable to industrial use. However, the use of an alkaline catalyst involves several drawbacks: ∑

An alkaline catalyst is still sufficiently corrosive (pH 8–10) to require stainless steel equipment. ∑ An additional neutralisation step of free fatty acids is required together with separation of soap formed. ∑ An additional step for refining the glycerol containing water and for separating the salt is also necessary. ∑ The recuperation efficiencies of the excess methanol and of glycerol are low.

Alkaline catalysts, including those based upon transition metals, are not resistant against the presence of water in the feed; they lead to unacceptable coloration of the product and pose environmental problems. Use of commercial catalysts such as NaOCH3 has the disadvantage that the products become contaminated with sodium. In the conventional transesterification process of triglyceride to methyl esters using NaOH or KOH dissolved in methanol, removal of these catalysts is technically difficult and a large amount of wastewater is produced to separate and clean the catalyst and neutralise the reaction product [51, 54, 72]. As pointed out already, utilisation of NaOH or KOH as catalysts produces soaps. A further limitation of the alkali-catalysed process is its sensitivity to the purity of the reactants (typically FFA < 0.5 wt%; anhydrous feedstock and reactants). In order to avoid undesired by-products in basecatalysed transesterification extensively pre-treated or refined vegetable oils are used. Also purification of the product for catalyst and saponified products is necessary. Processing alternatives like the acid-base integrated process (see Chapter 9) allow for the use of low-cost, low-quality feedstocks (inedible animal fats, waste cooking oils, brown grease), but these technologies still require additional catalyst, processing steps and time, thereby eliminating the advantages obtained by the use of lower cost feedstocks.

8.2.1 Liquid-phase metal catalysts PCT Int. Publ. No. WO 2007/012097 A1 and US Patent Appl. No. 2008/0227994 A1 to BDI-Biodiesel International AG (Grambach/Graz) [99, 100] describe liquid-phase metal catalysts of the class of earth alkali metal salts of a carboxylic acid (C10-C24, preferably Mg stearate or oleate) for the continuous or discontinuous production of carboxylate alkyl esters by (trans) esterification. The catalysts allow conversion of low-value feedstocks (high FFA, water containing) in >90% yield. The catalyst may be recovered by ion-exchange or distillation. Typical catalyst costs for Mg soaps are only

Table 8.8 Metal salts of fatty acids as (trans)esterification catalysts       Catalyst(s)

Raw material(s) Alcohol(s)

Zn-, Mn-palmitates, VO, VO   stearates Metal soapsb

a

VO, WVOa

Alkaline earth   metal saltsd

VO, WVO

a

Reaction conditions

Ester yield (%) Reference(s)

MeOH

423–523 K, 0.5–15 MPa, ROH/VO = 1.5–2.5 >92

[103]

MeOH, EtOH, i-PrOHc

513 K, 0.1–0.5 MPa, ROH/VO = 20–50

<97.8

[104, 105]

MeOH

423–473 K, <2 MPa, 0.5 h, ROH/VO > 6

98.2

[99, 100]

a

High FFA contents. Na, K, Zn, Cs laurates, palmitates, stearates, oleates. c Gaseous alcohols. d C10-C24 carboxylates. b

Biodiesel catalysis 339

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about 71/t vegetable oil, compared with 77–9/t for KOH catalysts. The glycerol by-product needs further purification. Table 8.8 lists other metal soaps active in (trans)esterification. Metal complexes have not been studied extensively in vegetable oil alcoholysis. Metal compounds of the type M(Hpy)2(H2O)2 (M=Sn, Zn, Pb, Hg; Hpy = 3-hydroxy-2-methyl-4-pyrone) are active for soybean oil (SBO) methanolysis under homogeneous conditions [101]. The catalytic activity decreases in the order Sn2+ >> Zn2+ > Pb2+ ≈ Hg2+. Sn and Zn complexes achieved a reaction yield of up to 90% and 40%, respectively, in 3 h at 333 K using a molar ratio of 400 : 100 : 1 (MeOH : oil : catalyst), with no emulsion formation. These activities exceed those using traditional NaOH and H2SO4 catalysts under similar reaction conditions. Abreu et al. [102] also reported the use of these metal complexes in the methanolysis of native Brazilian vegetable oils, such as andiroba (Carapa guianensis), babassu (Orbignya sp.), cumaru (Dipteryx odorata), palm tree (Elaeis sp.), piqui (Caryocar sp.) and soybean oil as well as in the alcoholysis of SBO with several alcohols (EtOH, PrOH, i-PrOH, n-BuOH, t-BuOH and cyclohexanol), all at 333 K.

8.3

Liquid-phase acid catalysis

An alternative way of processing vegetable oils for biodiesel production is to use an acid catalyst. Acid-catalysed production of biodiesel can economically compete with base-catalysed processes using virgin oils, especially when the former uses low-cost feedstocks [16, 17]. The accepted chemical mechanism for homogeneous acid-catalysed transesterification (Fig. 8.4) consists of: (i) protonation of the TG carbonyl group by the acid catalyst (key interaction); (ii) nucleophilic attack by an alcohol molecule on the protonated carbonyl (electrophilic species); (iii) solvent-assisted proton migration; (iv) cleavage of the intermediate hemiacetal species; (v) formation of a protonated alkyl monoester and diglyceride DG; and (vi) proton transfer to regenerate the acid catalyst [38]. The sequence is repeated twice to yield three alkyl monoesters and glycerol. Comparison of Figs 8.2 and 8.4 thus shows that acid catalysis is characterised by formation of a more electrophilic species and base catalysis by that of a stronger nucleophile. This crucial distinction is responsible for the observed differences in activity. The acid strength requirements of an organic reaction are strongly influenced by the presence of electron donor or withdrawing substituents on the functional group undergoing chemical transformation. Fewer studies have dealt with acid-catalysed transesterification of lipid feedstocks than base-catalysed synthesis of biodiesel. In homogeneous acid transesterification of SBO with BuOH three reaction regimes were observed, as for base-catalysed reactions [12]. Transesterification followed pseudo-first-order kinetics. Acid-catalysed transesterification kinetics of

Biodiesel catalysis +

O

H+

C R1

OR¢

OH

OH

C

C

R1

OR¢

341

+

R1

OR¢

TG OH

OH C R1

+

+ ROH

R1

OR¢

O

R

C

H

+

O

H O+

C R1

R¢

OR

OR

+ R¢OH DG

H

+

O

O A–

C R1

C OR¢

OH R1

H +

OR

R = alkyl group of the alcohol, R¢ = fatty acid residue,

+ HA

C R1

OR

R1 = fatty acid alkyl group, HA = acid

8.4 Mechanism of acid-catalysed transesterification of triglycerides.

SBO [12] and waste frying oil [106] have been reported. The rate of acidcatalysed methanolysis of pure FA (from saponified SBO or crude rice bran oil (CRBO)) is faster (99% conversion in 1 h at 338 K) than methanolysis of 60% FFA containing CRBO (> 90% conversion in 6 h) or CRBO + 5% H2O (2% after 3 h) [107]. This is most probably due to differences in the mechanism of esterification and transesterification. Methanolysis of FFAs proceeds via simple esterification while transesterification of TGs consists in a number of consecutive, reversible reactions in which a mole of FA ester is liberated at each step. Ester conversion by homogeneous acid-catalysed transesterification is influenced by a variety of parameters, including: catalyst nature and amount; nature of the alcohol; alcohol-to-oil molar ratio; reaction temperature; and feedstock composition (in particular presence of FFAs and water). Studies on the use of the preferred homogeneous catalysts (commonly Brønsted acids such as HCl, H 2SO 4, H 3PO 4, p-toluene and benzene sulphonic acids) in (trans)esterification reactions are limited. In the presence of solid p-toluenesulphonic acid monohydrate (pTSA), the (trans)esterification takes place in a pseudohomogeneous phase [113]. Table 8.9 reports some typical liquid-phase acid-catalysed transesterifications of vegetable oils and animal fats over mineral acids and sulphonic acids. Sulphuric acid is mostly used in the 1–5 wt% range. In acid-catalysed alcoholysis of SBO (molar ratio

Raw material(s)

Catalyst(s)

Alcohol(s)

Reaction conditions

Ester yield (%) Reference(s) 85.0 92.5 82.0 97.0 > 90 > 90.0

[108] [109] [110] [111] [107] [9]

99.8

[108, 112]

63–68

[7]

75–90 48–83

[113] [114]

n.g. > 99.0 98.4

[12] [115] [15]

97.9 >40.7 13.0 97.0

[116] [98, 117] [43] [118]

– 99.0 90.5

[119] [12] [120]

–

[121]

Biodiesel science and technology

Acid oil (59.3% FFA) H2SO4 MeOH 338 K, 0.1 MPa, 26 h, ROH/VOa = 15 Acid oil (56% FFA) H2SO4 MeOH 403–423 K, 1.7 MPa, 4.5 h, ROH/VO = 1.5–3 CAS HCl EtOH 353 K, 0.1 MPa, 2 h, ROH/VO = 4.1 CPO H2SO4 BuOH 368 K, 0.1 MPa, 9 h, ROH/VO = 40 CRBO (60% FFA) HCl MeOH 343 K, 0.1 MPa, 6 h, ROH/VO = 20 CSO, PNO, H2SO4 MeOH, 338 K, 0.1 MPa, 69 h, ROH/VO = 30   SBO, SNO   (EtOH, BuOH) HA-acid oil H2SO4 MeOH 338 K, 0.1 MPa, 14 h, ROH/VO = 1.8   (96.2% FFA) Microalgal oil H2SO4 MeOH 303–323 K, 0.1 MPa, 7 h, ROH/VO = 45–56   (4.5% FFA) Oleic acidb pTSA MeOH 313 K, 13–19 MPa, 2–4 h, ROH/VO = 15 PMO, RSO, UPGO pTSA, XSA MeOHc 348–358 K, 0.1 MPa, RO/VO = 12   (< 85% FFA) SBO H2SO4 BuOH 350–390 K, 0.1 MPa, 3-20 h, ROH/VO = 6 SBOd H2SO4 MeOH 393 K, 0.35 MPa, 24 h, ROH/VO = 9 SBOe H2SO4 MeOH, EtOH, Reflux T, ROH/VO = 30   i-PrOH, n-BuOH H2SO4 MeOH 338 K, 0.1 MPa, 1 h, ROH/VO = 300 SNOf SNOf H2SO4 MeOH, EtOH 338 K, 0.1 MPa, 3–4 h, ROH/VO = 600 TLW (3.4% FFA) H2SO4 MeOH 333 K, 0.1 MPa, 48 h, ROH/VO = 7.5 VO (<8% FFA) MSA, C10-C12 MeOHg 323–373 K, < 0.5 MPa, ROH/VO = 3.5–7.5   alkyl BSA, pTSA VOd (4.6% FFA) H2SO4, H3PO4 MeOH 473–523 K, 5–8 MPa, 27 h, ROH/VO = 20 VOd H2SO4 MeOH, (BuOH) 338 K, 50 h, ROH/VO = 30c VOd pTSA, XSA, BSAh aq. EtOH 353–403 K, >0.1 MPa, 24–0.5 h,   ROH/VO = 3–7.5 WVO H2SO4 MeOH 338 K, 0.1 MPa, 1–3 h, ROH/VO = 2–5

342

Table 8.9 Liquid-phase acid-catalysed (trans)esterification of vegetable oils and animal fats over mineral acids and sulphonic acids

WVO H2SO4 MeOH, EtOH,   n-PrOH, n-BuOH WCO (6% FFA) H2SO4 MeOH WCO (6% FFA) H2SO4 MeOH WPMO HCl, H2SO4 EtOH (10–15% FFA)

reflux T

–

[122]

343 K, 0.3 MPa, 4 h, ROH/VO = 245 353 K, 0.17–0.4 MPa, 4 h, ROH/VO = 50–245 363 K, 0.1 MPa, 3 h, ROH/VO = 38

99.0 97.0–99.4 –

[106] [17, 106] [123]

a

Molar ratio.       Supercritical CO2 esterification. c Esterification-transesterification. d High FFA content. e Food-grade soybean oil. f In-situ. g Esterification. h BSA, benzene sulphonic acid; MSA, methane sulphonic acid; pTSA, p-toluene sulphonic acid; XSA, xylene sulphonic acid. b

Biodiesel catalysis 343

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Biodiesel science and technology

MeOH/SBO = 9 : 1) using 0.1 to 1.0 wt% HCl, H2SO4, HNO3, HCOOH and CH3COOH (pKa values of –6.1, –3.0, –1.38, 3.8 and 4.8, respectively) at 373–393 K, only sulphuric acid was effective (99% conversion in 8 h) [115]. Apparently, the pKa value is not a good indication of the catalytic ability of an acid for alcoholysis. Reaction rates in acid-catalysed processes are enhanced by the use of greater amounts of catalyst. For example, the methyl ester yield in transesterification of grease increased from 72.7% to 95.0% for H2SO4 concentrations varying from 1–5 wt% [15]. Possible complications of high acid concentrations are greater waste formation and increased costs of the catalyst neutralisation process and promotion of ether formation by alcohol dehydration [124]. Although organosulphonic acids are good catalysts they present difficulty of removal due to their lower vapour pressures and formation of soluble salts. Typical reaction conditions in liquid-phase acid-catalysed transesterification are given in Table 8.10. The elevated boiling points of higher alcohols enable the liquid reaction system to be operated at higher temperatures while maintaining moderate pressures. This is important for acid-catalysed transesterification since higher reaction temperatures are often required here to achieve faster reaction conditions. Nye et al. [122] compared C1-C4 linear alcohols for the acid-catalysed (0.1% H2SO4) transesterification of waste frying oil at reflux temperatures. Reaction rates varied as follows: BuOH > n-PrOH > EtOH > MeOH. The reverse was true for the base-catalysed process. Apparently, the initial reagent phase miscibility is more critical in acid catalysis than in base catalysis. Acid-catalysed transesterification achieves greater and faster conversion at high alcohol concentrations. Higher methanol/oil molar ratios are necessary to drive the transesterification reaction to completion [13, 15]. A high molar ratio of alcohol to oil (30–150 : 1) is often required to obtain good product yields in practical reaction times; large amounts of catalyst (typically > 10 wt%) are frequently necessary in such transesterifications. Complete transmethylation of CPO was found between MeOH/CPO = 35–45 : 1 [111]. Table 8.10 Typical reaction conditions in acid-catalysed transesterification of a vegetable oila (after ref. [17]) Feedstock

TG mixture with high FFA contents; alcohol

Alcohol-to-oil molar ratio Temperature Pressure Catalyst Catalyst load Conversion

50 : 1 353 K 0.4 MPa H2SO4 1.3 : 1 (molar ratio H2SO4/oil) 97% after 4 h

a

Methanolysis of waste cooking oil (4 wt% FFA).

Biodiesel catalysis

345

In acid-catalysed transesterification of SBO the yield of FAME increased with higher MeOH/SBO molar ratio, temperature and catalyst amount [15]. Methyl ester conversions sharply increased from 77% at MeOH/SBO = 3.3 : 1 to 87.8% at 6 : 1 and 98.4% (maximum value) at 30 : 1. Transesterification was inhibited by the presence of water in the oil phase. As shown in Table 8.9, 99% waste cooking oil conversion to FAME was obtained after 4 h for a 245 : 1 MeOH/VO molar ratio at 353 K and 0.3 MPa [106]. Such a high excess of methanol would obviously result in a very large excess in reactor size, with a considerable negative economic impact. Temperature plays an important role in acid-catalysed synthesis of biodiesel. Acid-catalysed methanolysis of TG at the methanol reflux temperature (338 K) may require reaction times on the order of days to achieve satisfactory conversions. Higher temperatures at moderate-to-low pressures enhance oil-methanol solubility (i.e. decrease phase separation) and reaction kinetics (increased rate constants resulting from the effects of temperature and improved miscibility), leading to substantially shorter reaction times. Higher temperatures minimise the initial mass transfer controlled regime in transesterification. Pressure vessel requirements are the primary disadvantage of acid catalysts at higher temperatures. At 373 K, the vapour pressure of methanol is 0.35 MPa. Goff et al. [115] have investigated the acid-catalysed methanolysis of SBO at higher temperatures (373–393 K) and increased pressures in order to enhance reaction rates and provide alternatives over base catalysts. In (atmospheric pressure) butanolysis of SBO comparable conversions at 350 and 390 K (reflux temperature) required 20 and 3 h, respectively [12]. The temperature effect is especially quite pronounced at high T, p (513 K, 7 MPa), with ester conversions exceeding 90% in only 15 min using 1.7 wt% H2SO4 [125]. For optimisation of reaction parameters of acid-catalysed transesterifications, see refs. [116, 123]. Table 8.4 shows the main features of acid transesterification catalysis of triglycerides. Acid catalysis is more tolerant of high FFA levels and moisture in the starting feedstock than base catalysis. In fact, acid catalysts can simultaneously catalyse both esterification and transesterification reactions, the former according to

RCOOH + R¢OH P RCOOR¢ + H2O.

8.6

Given the versatility of acid catalysts to deal also with high FFA contents and some water in the starting feedstock, their use is considered as an economically viable alternative to base catalysts for the production of biodiesel from low-cost, low-grade materials such as yellow grease, but even palm oil and coconut oil qualify. Palm oil can contain up to 30% FFAs. Efficient transesterification of low-value, high-FFA raw materials, such as sulphur olive oil [126], CRBO (60% FFA) [107], heterotrophic microalgal oil (acid value = 8.97 mg KOH/g) [7], acidulated soapstocks (acid value = 112.2 mg

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KOH/g) [109] and high-acid acid oils from soapstocks (up to 98% FFA) [112], has been reported. Free fatty acids are not converted to salts when using acid catalysts, as occurs during reaction using alkali catalysts; therefore, the ester yield is higher and the purification steps are easier. It should be realised, however, that acid-catalysed conversion of low-cost feedstocks leads to formation of significant quantities of water according to Eqn 8.6, which has a negative effect on biodiesel production since water can hydrolyse the ester products, leading (again) to FFAs. Consequently, highly acidic raw materials yield moderate conversions even in acid-catalysed alcoholysis reactions. In harsh reaction conditions (high T, p), high-FFA feedstocks can easily be transformed by acid catalysis with continuous water removal. However, in these circumstances side reactions, such as alcohol etherification, may take place. Acid-catalysed transesterifications are seldom used as the sole reactions in industrial biodiesel production. They usually serve as preliminary steps for deacidification of fatty materials by pre-esterification of FFAs to acidity levels suitable for successive conventional alkaline transesterification catalysis (see also Section 9.3). Sulphonic acids have been used as catalysts in the preesterification of highly acidic feedstocks (acid values up to 60 mg KOH/g), preceding base-catalysed transesterification of TGs [118, 120], as well as in simultaneous esterification–transesterification processes (without the need for any auxiliary selective solvent) [114]. In the two-step sulphuric acid-catalysed pre-esterification of FFAs in used cooking oil to reduce FFA levels to below 1 wt% prior to proceeding to alkaline-catalysed transesterification of TGs, the pre-treatment step was both preceded and followed by a slow but economic water removal process (by gravity separation in settling tanks) [127]. Acid-catalysed transesterification is sensitive to water concentration. Water in the reaction mixture is detrimental for acid catalysis, as is evident from the reaction mechanism (Fig. 8.4), which involves formation of a carbocation intermediate. In the presence of water, carbocations may form carboxylic acids at the expense of the alkyl ester yield [38]. The sensitivity of ester forming reactions to water and FFA levels in acid-catalysed transesterification of SBO has been investigated [15, 115]. Table 8.11 shows that higher water concentrations in SBO methanolysis result in significantly lower FAME yields, probably due to the water inducing a second phase (at higher conversions, methanol alone would not induce this phase) that extracted methanol and catalyst from the oil [115]. As little as 0.1 wt% water in the reaction mixture already affects the ester yield; the reaction is almost completely inhibited at 5 wt% water concentration [15]. In fact, the H2SO4-catalysed SBO/MeOH ester conversion of 95% is reduced to <90% and 5.6% upon addition of 0.5% and 5% water, respectively. It is advised to keep the water content below 0.5 wt% to achieve higher than 90% ester yield under typical reaction conditions (see Table 8.10). In methanolysis of RSO the water

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Table 8.11 Effect of water on the conversion of soybean oil in acid-catalysed methanolysisa (after ref. [115]) Catalyst

Water concentration

 

<0.1 wt%

1 wt%

0.1 wt% H2SO4 0.5 wt% H2SO4

40% >90%

21% 66%

a

After 2 h of reaction.

concentration was found to be more critical in acid-catalysed (3 wt% H2SO4) transesterification than in base catalysis (1.5 wt% NaOH) [128]. For 5 wt% water in the starting material acid-catalysed ester conversion amounted to only 6%, as opposed to 70% for the base-catalysed reaction. The cause for the observed difference in transesterification sensitivity to water using acid or base catalysts has scarcely been addressed [15, 128]. It is clear from Fig. 8.4 (read HOH instead of ROH) that water favours formation of carboxylic acid, which reduces the alkyl ester yield. Some catalyst deactivation can take place by hydration. Increased water concentration affects transesterification more than esterification [128]. Acid-catalysed esterification of FFAs shows greater tolerance to water. The polar carboxylic groups in FFAs and their capacity to easily interact with water molecules through hydrogen bonds facilitate the FFA-catalyst interaction, and consequently, esterification. Acid catalysts have some other severe drawbacks (Table 8.4). While H2SO4 catalysis in the homogeneous phase lacks chemoselectivity, it is often considered a more serious problem that transesterification by homogeneous acid catalysts is much slower than that by alkaline catalysts [122, 127, 129]. Homogeneous acidic catalytic esterification or transesterification of oils and fats takes place at a substantially slower rate (about 3 orders of magnitude) than in case of an alkali metal catalyst for comparable amounts of catalyst, and generally requires temperatures above 373 K [130]. Long reaction times of 48–96 h are not exceptional, unless reactions are conducted at high T, p [48]. Best results are obtained at the boiling point of the alcohol [131]. Acid-catalysed alcoholysis reactions occasionally affect product quality. In typical reaction conditions (T = 373 K, p = 0.5 MPa [118]), increased formation of unwanted secondary products, such as dialkylethers and glycerol ethers is observed [132]. Darkly coloured products may be the result of air oxidation [115], formation of sulphones from sulphuric acid [133], or use of high temperatures (> 523 K) [82]. The use of homogeneous acid catalysts, such as sulphuric and sulphonic acids, generally results in sulphur contamination of the final product. The disadvantage of the need for higher reaction temperatures and pressures is that more expensive materials must be used in construction. A further disadvantage of H2SO4 is its corrosive action on stainless steel

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equipment at elevated temperatures. The corrosiveness of strong liquid acids and environmental threat are strong deterrents to their use. Process engineering is also generally much more elaborate. Batch esterification catalysed by homogeneous sulphuric acid requires a water removal step (by distillation, adsorption or scavenging), recycling of excess alcohol and ester purification. The problem with this process is the discontinuous operation mode that also involves a costly separation of homogeneous catalyst. Moreover, the alcohol-to-acid ratio inside an industrial reactive distillation unit may vary over several orders of magnitude. Especially for stages where an excess of alcohol is present, the use of an acid catalyst may lead to side reactions such as ether formation or alcohol dehydration.

8.4

Heterogeneous catalysis in biodiesel synthesis

Although the basis of the chemical and petrochemical industry is catalysis, few biorefining processes use heterogeneous catalysts. Use of heterogeneous catalysts in transesterification reactions overcomes some of the aforementioned drawbacks of homogeneous catalysts (see Tables 8.3 and 8.4). In the conventional homogeneous transesterification method of vegetable oils, removal of the base catalysts after reaction is technically difficult, and large amounts of wastewater are produced to separate and clean the products. Therefore, replacement by heterogeneous catalysts is desirable in view of the ease of separation of the post-reaction mixture, minimisation of washing steps and lower downstream processing costs, thus reducing total production costs (Table 8.12). In principle, catalysts can be recycled and reused for prolonged periods of time and no catalyst losses occur. A solid catalyst can be separated by physical methods such as a hydrocyclone in the case where Table 8.12 Main characteristics of heterogeneous transesterification catalysts Advantages: ∑ Simplified separation of the post-reaction mixture ∑ No catalyst losses ∑ No product contamination ∑ Fewer restrictions on feedstock quality (FFAs and water); catalyst dependent ∑ No corrosion ∑ No/reduced foaming ∑ Application of fixed bed processes Disadvantages: ∑ Tedious catalyst preparation ∑ Cost ∑ Lower reaction rates than for homogeneous catalysts ∑ Need for high T, p reaction conditions ∑ Requirement for high alcohol/oil molar ratio ∑ Confinement of the utility to certain types of esters only ∑ Diffusivity of TG molecules        

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a multi-phase (e.g. slurry) reactor is used. Alternatively, a fixed bed reactor would eliminate the catalyst removal step entirely. Moreover, products of higher purity are obtained. There are also fewer restrictions on raw material specifications. In the alcoholysis reaction, free fatty acids eventually present in the feed are also esterified during the process, which is not the case with the commercially used NaOCH3 catalyst and no, or less, foaming occurs. Processes using heterogeneous catalysts need higher temperatures than homogeneous catalysts to be effective in a reasonable time. For efficiency reasons, solid catalysts should ideally work at temperatures below 423 K. Because of the presence of heterogeneous catalysts, the reaction mixture constitutes a three-phase system, oil-alcohol-catalyst, which affects the reaction rate for diffusion reasons. The reaction rate can be enhanced by ultrasound [134] as well as by introducing a co-solvent [134, 135]. No heterogeneous catalysts are commercially viable in the 318–338 K range. Some may be operative at 373–423 K; however, reactor residence times are often in excess of 4 h, requiring large amounts of catalysts. Above 373–423 K, the high pressures needed to keep the methanol in the liquid phase significantly increase equipment costs. Although heterogeneous catalysts are typically preferred over homogeneous catalysts operating at the same temperatures and pressures, a homogeneous catalyst may be preferred if it is equally effective at lower loadings. It is possible to distinguish three main groups of heterogeneous catalysts: metal, base and acid catalysts. Among the various heterogeneous alkaline alcoholysis catalyst classes proposed (Tables 8.13 and 8.15) alkali/alkaline earth metal carbonates and inorganic oxides are most frequently used, such as CaO, MgO, Al2O3, silicates, SiO2·Al2O3, boria, oxides of P, Ti, Zr, Sn, Cr, Zn and Fe, as well as salts. Silicates such as Na2O·SiO2 and K2O·SiO2 show poor transesterification catalysis (2% yield for 1 wt% catalyst at 338 K) [136]. Several Zn/Ti/Sn silicates and aluminates convert VOs and WVOs in high yields (>92%) at 493–523 K, 4–10 MPa and ROH/VO molar ratio of 9 to 54 [137]. Group IV B silicates, i.e. titanium and zirconium compounds, possess very good catalytic properties in transesterification reactions [138, 139]. For transesterification catalysis by silicates and zeolites, see also Tables 8.13 and 8.18. Also metals (e.g. Sn, Ge or Pb) supported on various materials such as ZnO, MgO, TiO2, activated carbon or graphite, have been tested as well as natural clays, zeolites and strong organic bases heterogenised on organic polymers. Among the many different heterogeneous catalysts – in principle insoluble in the reaction mixture – which have been developed to catalyse the transesterification of VOs at the laboratory scale, such as phosphates (of Na, K, Al, Ga, or Fe) [136, 140], hydrotalcites [141–143], modified zeolites ETS-4 [138, 144, 145], Li/CaO [146], Na/NaOH/g-Al2O3 [147] and CaCO3 [135], some are quite expensive or complicated to prepare, e.g. anionic

350

Table 8.13 Transesterification of vegetable oils and animal fats by solid bases   Raw Alcohol(s) Reaction conditions material(s)

Ester yield (%)

Reference(s)

CNOa

338–343 K, ROH / VO = 5.5–14

–

[148]

–

> 90–95

[149]

Alkali/alkaline earth Mixture of oxides/ WVOc MeOH 338–348 K, >0.1 MPa, 5 min,   alcoholates   alcoholates (1–2 wt%)   ROH/VO = 4

98

[150]

Alkaline earth metal CaCO3 SBO EtOH 473–523 K, 3–20 MPa, 0.3 h,   carbonates   RO/VO = 19

< 5, > 95d [135]

Alkaline earth CaO, SrO, BaO CNO, LSO, MeOH 338 K, 8 h   metal oxides   TLW CaO·MgO RSO MeOH 333 K, 0.1 MPa, 12 h, ROH/VO = 6 KI/CaO CSO, SBO, MeOH –, 2 h, ROH/VO = 6   SNO MgO RSO MeOH 338 K, 0.1 MPa, 1–22 h,   ROH/VO = 6–75 MgO SBO MeOH 373 K, n.g., 2 h, ROH/VO = 6 MgO SBO MeOH 453 K, n.g., 1 h, ROH/VO = 12 35% K2O/Al2O3 (calcined) SBO MeOH 338 K, 0.1 MPa, 7 h, ROH/VO = 15 Na/NaOH/g-Al2O3 SBO MeOH 333 K, 0.1 MPa, 2 h, ROH/VO = 9e

–

[151]

>95 93

[152] [153]

69

[154]

35 70–90 87 75

[155] [155] [156] [147]

81

[154]

99

[157]

Alkali metal (hydrogen) Na2CO3, K2CO3, NaHCO3,   carbonates   KHCO3



MeOH

Alkali metal oxides K2O (oil crop waste ashes) CNO, PMO MeOH,   EtOHb

Alkaline earth metal   hydroxides

Ba(OH)2

RSO

MeOH

338 K, 0.1 MPa, 1 h, ROH/VO = 6

Phosphates, Zr(O3POK)2 RSO, VOf MeOH, 423–453 K, 1–7 MPa, 1 h,   organophosphorates   EtOH   ROH/VO = 10–20

Biodiesel science and technology

Catalyst class Catalyst(s)

(Modified) zeolites Cs-NaX RSO MeOH 338 K, 0.1 MPa, 22 h, ROH/VO = 275 ETS-10, K-ETS-10, SBO MeOH 333–423 K, 2.4 MPa, 24 h,   Cs-ETS-10, (Cs,K)-ETS-10   ROH/VO = 6 NaX, KX, CsX, (Cs, K)X, SBO MeOH 333–423 K, 2.4 MPa, 24 h,   (NaOx, NaX), NaY   ROH/VO = 6 ETS-4, ETS-10 TLW MeOH 493 K, 2.1 MPa, 1.5 h, ROH/VO = 4.2 ETS-4, ETS-10 SBO MeOH 493 K, 2.1 MPa, 1.5 h, ROH/VO = 4.2 Anionic clays

Mg-Al Mg-Al Mg-Al Mg-Al

hydrotalcites hydrotalcites hydrotalcites hydrotalcites

(calcined) (calcined) (calcined) (calcined)

Anion-exchange resins Amberlyst-A 26/27(OH) a

SBO GTBg SBO SBO

MeOH MeOH MeOH MeOH

338 333 373 453

K, K, K, K,

SNO

MeOH

333 K, 0.1 MPa, 8 h, ROH/VO = 6

55 95

[154] [145]

31

[145]

19–30 81–87

[138] [139]

0.1 MPa, 7 h, ROH/VO = 7 – 21 65 0.1 MPa, 3 h, ROH/VO = 30 74.8 n.g., 3 h, ROH/VO = 6 75 n.g., 1 h, ROH/VO = 12 92

Acid value < 1.   Absolute. c High water content. d With SBME as a solvent. e Co-solvent: hexane. f Up to AV = 10 mg KOH/g. g Glyceryl tributyrate.

[143] [158] [155] [155]

0.1–0.4  

[2]  

b

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clays (hydrotalcite-like) or zeolites (such as ETS-4); others are sensitive to water and acids, which limits industrial application. Many proposed catalytic systems require rather drastic reaction conditions (T, p, alcohol volumes), which even casts doubt on the presumed catalytic effect at all, and anyhow is likely to prevent commercial exploitation. Heterogeneous catalysts also include enzymes, which are examined in more detail in Chapter 10. In general, it seems difficult to obtain the ester and glycerol economically in heterogeneously catalysed processes (see refs. [102, 159]). Commercially, solid bases are scarcely used for transesterification compared to homogeneous catalysts. In addition to transesterification reactions, solid catalysts, such as simple oxides and zeolites, have been used to carry out esterifications of fatty acids [160]. Application of heterogeneous catalysts for the commercial production of biodiesel by a continuous process is still in its infancy [157, 161, 162]. Fixed-bed heterogeneous catalysis leads to ideal products, but issues to be considered are cost, operating conditions, restricted purchase of catalyst, and licensing/royalties (see also Section 15.3.1). Heterogeneous catalysts for biodiesel production have been reviewed recently [163].

8.4.1 Metal-based catalysis Heterogeneous catalysis by metals, (transition) metal compounds, organometallics and supported metal complexes has been used for transesterification reactions. Suppes et al. [145] have reported on the catalytic activity of various metals (Ni, Pd) and alloys (cast iron and stainless steel) for methanolysis of soybean oil. The metal catalysts were evaluated primarily to determine whether metal reactor surfaces catalyse the alcoholysis reaction. Nickel shows particularly high transesterification activity (Table 8.14) and could be an effective catalyst for alcoholysis if dispersed on high surface area supports. Some metal alloys of industrial reactors behave as effective transesterification catalysts [145]. Obviously, studies conducted with reactor vessels with exposed metallic surfaces may lead to misleading interpretations about catalytic reactivity, as possibly in case of alcoholysis over ZnO/Al2O3 at high T, p [82]. Other selected metals (Pb, Zn, Fe, Cu, Ni, Sn, Al) were screened for their catalytic activity in SBO/MeOH transesterification [164]; Pb showed the highest activity, giving a conversion of 55% (reaction conditions: molar ratio MeOH/SBO = 42 : 1, 5 wt% catalyst, 338 K, without co-solvent). PCT Int. Patent Appl. No. WO 03/087279 to Center et al. [81] has claimed a large variety of metal catalysts (including Sn, Pb, Cd, Zn, Ti, Zr, Hf, Al, Sb, Ca, Bi, Mg, U) for transesterification in a continuous plug-flow reactor, albeit without citing conversions.

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Table 8.14 Conversions of soybean oil over various powdered catalysts and zeolite catalysts (without calcination)a (after ref. [145]) Catalyst

Methyl ester (wt%)

No catalyst CaCO3 ZnCO3 Nickel Palladium ZnO Cast iron Stainless steel KX CsX (Cs,K)X Cs-ETS-10 K-ETS-10 (Cs, K)-ETS-10

0.13 1.7 9.3 53 29 80 3.1 3.9 11 8 9 18.2 11.5 15

a

Reactions were carried out at 393 K for 24 h.

US Patent No. 5,525,126 to Basu and Norris [11] discloses non-alkaline metal compound catalysts consisting of a mixture of Ca/Ba acetates (3 : 1 wt/wt) for the production of FAAEs for use as diesel fuel from anhydrous oils and fats with high FFA content without a pre-esterification step, but in rather drastic reaction conditions (T > 473 K). Organometallic catalysts such as tri-n-butyltin methoxide and ethoxide can act as transesterification catalysts in fairly low yields (20–72%). Although bis(tri-n-butyltin) oxide shows good catalytic results in ethylene glycol (EG) and diethylene glycol (DEG) alcoholysis of soybean oil and tallow, these components are very soluble in fatty acid esters, which complicates their separation. Alkyltin oxide catalysts (0.01–3 wt%) were also claimed in the single-step esterification/transesterification of vegetable oils and animal fats at 423–473 K and 0.1–3.0 MPa with alcohol/oil molar ratio of 3 : 1 to 30 : 1 [165]. Organotin oxides as alcoholysis catalysts were also proposed [166]. Abreu et al. [167] have attempted vegetable oil transesterification over multi-phase catalytic systems based on anchoring Sn(Hpy)2(H2O)2 (see Section 8.2.1) to ionic liquids such as BMI(PF6) (BMI = 1-butyl-3methylimidazole) or supporting the complex on an acid ion-exchange resin (Dowex®50 WX8-100). While it was not possible to obtain a recyclable multi-phase system based on this immobilised metal complex, SnO is active for SBO methanolysis in a heterogeneous system (conversion of 93% in 3 h at 333 K for SBO/MeOH molar ratio 4.15 : 1). VO(acac)2 is a homogeneous and VO(acac)2/celadonite a heterogeneous system for transesterification of soybean oil [168]. US Patent No. 5,532,392 to Gheorghiu [169] describes organotitanate

354

Catalyst class Catalyst(s) Raw material(s) Alcohol(s) Reaction conditions

Ester Reference(s) yield (%)

VO, VOa MeOH 483–553 K, 15 MPa, ROH/VO = 6–30 > 97 Transition metal Fe2O3/Al2O3   oxides, hydroxides, FexOy, ZrO2 WVOb MeOH 328–338 K, 1 h, ROH/VO = 3–5.5 > 30   salts NiOx, NiCO3 VO,WVO MeOHc 533–673 K, ROH/VO = 39 > 95 ZnAl2O4. xZnO. VO, WVO, TLW MeOH, 443–523 K, 1–6 MPa, 2 h, 60–96 yAl2O3d   EtOH   ROH/VO = 7–50 ZnO RSO MeOH 498 K, 4.4 MPa, 6 h, ROH/VO = 27.4 93 KF/ZnO SBO MeOH 338 K, 0.1 MPa, 9 h, ROH/VO = 3–20 87 Zn silicate CNO, TLW MeOH 523 K, >10 MPa, ROH/VO = 10 > 85 Transition metal salts Zn-, Cd-arginate POb MeOH 338 K, 3 h, ROH/VO = 6 69   of amino acids Zn-arginate/SiO2 SNO MeOH 398 K, 0.5 MPa, 20 min, ROH/VO = 6 80 Transition metal salts Zn-, Mn-palmitates, VO, VOa MeOH 423–523 K, 0.5–15 MPa, > 92   of fatty acids   stearates   ROH/VO = 1.5–2.5 Transition metal salts Dodecylbenzene VO, TLW MeOH 513 K, 0.5 MPa, 5.75 h, ROH/VO = 40 96   of sulphonic acids   sulphonates (Zn, Ti, Cr, Co, Cd) a

High FFA contents. Deacidified. c Supercritical. d 0 ≤ x, y ≤ 2.   b

[159] [170] [171] [172, 173] [172, 173] [174] [175] [176] [176] [101] [102, 103]

Biodiesel science and technology

Table 8.15 Transition metal catalysts for transesterification

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and titanium (organo)carboxylate-based catalysts, in particular tetrabutyl orthotitanate (promoted by 3 wt% zinc acetylacetonate) for the preparation of FAME from natural oils (such as PMO, PKO, RSO) or fats by transesterification at 498 K and 5 MPa for 2–3 h at an alcohol/VO molar ratio of 3 : 1 to 9 : 1. As organotitanate-based catalysts require oils or fats with low water and phosphorus content, a two-step pre-treatment of the feedstock (acid degumming to P content below 50 ppm and combined drying/filtration over active bleaching earth to obtain H2O < 0.01% and P < 15 ppm) is needed. Surprisingly, no fatty acid elimination step (by alkaline neutralisation or steam distillation) is needed for FFA contents below 5%. The simultaneous esterification of fatty acids according to Eqn 8.6 and transesterification in anhydrous conditions do seem to be conflicting. The results rather suggest acid-catalysed transesterification. As the catalyst is neither alkaline nor corrosive, and no corrosive by-products are formed, the equipment can be constructed in soft steel. Table 8.15 lists some transition metal compounds active in transesterification. Zinc oxide-based catalysts are effective in transesterification of oils with heavier alcohols than methanol (e.g. EtOH, i-PrOH, n-BuOH), which is advantageous as to the pour point of the biodiesel fuel so obtained [172]. No deactivation of a ZnO catalyst for methanolysis of RSO was observed in the presence of 2.5 wt% H2O [172]. However, the propensity of ZnO (and ZnCO3) to go into solution, especially in the presence of high concentrations of free fatty acids, diminishes the catalytic potential. Xie and Huang [174] have shown that the catalytic activity of a comparatively low-cost KF/ZnO heterogeneous base catalyst in the conversion of SBO is superior to that of KOH/ZnO and K2CO3/ZnO. US Patent No. 5,908,946 to Stern et al. (to IFP) [172] has reported use of a supported ZnO/Al2O3 catalyst in the production of alkyl esters by alcoholysis of oils at high temperatures (> 473 K) and pressures; high conversions (> 80%) were observed after 2 h in batch and continuous flow packed-bed reactors. As the yield was about 60% in the absence of the catalyst the metallic surface of the reactor used may have contributed to the result. It is also important to eliminate alkaline salts before calcination because otherwise the real catalyst might be an alkaline impurity, which would dissolve slowly in the medium, and the catalytic activity would gradually decrease. ZnO/ Al2O3 promotes alcoholysis reactions of alcohols higher than methanol [172]. Transesterification of glycerides to biodiesel fuel in one or more stages was also carried out over a related spinel-type zinc aluminate, consisting of ZnAl2O4◊xZnO◊yAl2O3 (x, y = 0–2) [177, 178]. The IFP process based on the spinel-type catalyst represents a considerable improvement in heterogeneous catalysis. By using this process, final purification is reduced to a minimum and the two products (FAAE and glycerol) are obtained with a high degree of purity under conditions of T = 443–523 K and p = 1.0–6.0 MPa [162,

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172]. The (commercial) process is suitable for refined oils, used frying oils, animal oils and fats; more than 10 K in pour point can be gained with the esters that are formed with higher alcohols. In the recent PCT Int. Publ. No. WO 2008/135665 to Lecocq et al. [157], IFP has disclosed improved (basic) heterogeneous catalysts of the phosphate type (such as Zr(O3POK)2) and organophosphorated compounds of Group IV metals (Zr, Hf, or Ti) (see Section 15.3.1). Benefuel Inc. (Mt. Prospect, IL) uses a new, dual metal catalytic (DMC) process for transesterification of triglycerides (ENSELTM ; NCL technology), which may be combined with another cost effective process for converting glycerol into glyceryl polyethers, thus overcoming the glycerol glut [179]. Also supported metal complexes are active in transesterification reactions of simple esters and triglycerides [180, 181]. Titanate complexes, both in solution and in supported form, catalyse the transesterification through a Lewis acid mechanism where the reactant ester and metal form a Lewis complex activating the carbonyl groups for a nucleophilic attack by the reactant alcohol. The intermediate breaks down into the product alcohol and an ester-metal Lewis complex. After desorption of the product ester from the Lewis site the cycle is repeated [180]. In general, titanates are very sensitive to moisture. Strong Lewis acids such as Ti(OR)4 can provide an effective alternative to traditional Brønsted base catalysts [182]. Immobilised, polymer-supported titanium catalysts (Ti(Oi-Pr)4 grafted onto porous poly(p-hydroxystyrene) resins with different cross-linking levels) were used to promote transesterification of methylmethacrylate (MMA) with 2-ethylhexanol [181]. Highly dispersed TiO2/SiO2 catalysts for biodiesel production were obtained by grafting Ti(OiPr)4 on silica [183]. Many of the metal catalysts exhibit high toxicity, requiring very efficient catalyst removal procedures. In order to enhance their applicability, they should be appropriately anchored on suitable solid supports. However, supported (fixed) organometallic species are often less active than in solution.

8.4.2 Catalysis by solid bases The most extensively tested solids for transesterification of triglycerides are catalysts containing Lewis or Brønsted base sites. In particular, a variety of hydroxides, (mixed) oxides, carbonates and silicates of Group I and II metals, as well as zeolites are effective catalysts for certain ester formation reactions [184] (see Table 8.13). KNO3/Al2O3, calcined at 773 K, forms basic sites (K2O or Al-O-K entities), which are active in transesterification [156]. Gryglewicz [134] has described heterogeneous base-catalysed methanolysis of refined, low-erucic RSO using ultrasound and THF to accelerate the process. Catalysts tested were MgO,

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CaO, Ca(OH)2, Ca(OCH3)2 and Ba(OH)2, which are all very slightly soluble in organic solvents (see Table 8.16). Figure 8.5 ranks catalytic activity in methanolysis of rapeseed oil at 333 K as NaOH > Ba(OH)2 > Ca(OMe)2 > CaO, where the strong base Ba(OH)2 is only slightly less active than NaOH. In fact, the most active heterogeneous catalyst reported to date is Ba(OH)2. The observed rate of reaction was lowest for CaO and zero for MgO and Ca(OH)2 [134]. The activity of CaO/THF was comparable to that of NaOH. Chemically, thermally and mechanically stable porous HPLC-grade microspherical supports (25 mm ZrO2, 80 mm TiO2, 300 mm a-Al2O3), with or without surface treatments (acidic or basic; typically hydroxide or phosphate modified), are suited for packing in a high-pressure (170 MPa), high-temperature (573–723 K), continuous-flow fixed-bed reactor for longTable 8.16 Alkaline earth metal compound solubilities in methanol (after ref. [134]) Compound

MgO

Solubility in methanol (%) 0.130

0.010

CaO 0.035

Ca(OCH3)2 0.040

a

Ba(OH)2 1.170

Colloidal suspension. 100

80

60 Yield (%)

a

Ca(OH)2

40

Ba(OH)2 20

Ca(OCH3)2 CaO NaOH

0 0.0

0.5

1.0 1.5 Time (h)

2.0

2.5

8.5 Activity of alkaline earth metal compounds in methanolysis of rapeseed oil (molar ratio MeOH/RSO = 4.5 : 1) at 333 K (after ref. [134]).

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Biodiesel science and technology

term simultaneous esterification and transesterification of low-value feedstocks under supercritical alcohol conditions with ultra-short residence times (< 1 min.) (Mcgyan process) [185]. The hydroxide ion is a stronger Lewis base than phosphate. Alkalinity is an important factor in determining the catalytic activity of base catalysts. It is noticed that alkaline power of alkaline earth (M = Mg, Ca, Ba) compounds can be ordered as follows: M(OH)2 < MO < M(OCH3)2. The basicity of alkaline earth metal hydroxides increases in the order Mg(OH)2 < Ca(OH)2 < Ba(OH)2. The true catalytic nature of Ba(OH)2 remains uncertain. In fact, homogeneous catalysis may also be involved in methanolysis of RSO at 338 K with >80% conversion in 1 h over Ba(OH)2 in view of the non-negligible solubility in water and methanol [134, 154]. Barium alcoholates can form as follows:

Ba(OH)2 + CH3OH ´ CH3OBaOH + H2O

8.7



CH3OBaOH + CH3OH ´ Ba(OCH3)2 + H2O

8.8

The catalytic activity shown by Ba(OH)2 may (partly) be due to dissolved Ba-alkoxide species rather than basic surface sites of the Ba(OH)2 solid. As soluble barium compounds are highly toxic, Ba(OH)2 is not a suitable catalyst for transesterification. Calcium hydroxide is practically insoluble in methanol (Table 8.16). Moreover, Ca(OH)2 is a much weaker base than Ba(OH)2 and does not catalyse the alcoholysis reaction. A drawback of CaO as a catalyst is its low catalytic activity in methanolysis of RSO in comparison to NaOH [134]. Although CaO is insoluble in alcohols at room temperature, it might show some solubility in methanol at moderate-to-high temperatures [134]. Moreover, as CaO is soluble in glycerol, even if the catalytic process is purely heterogeneous at the beginning, a homogeneous catalysed reaction may contribute once small amounts of glycerol are present. The issue of heterogeneous versus homogeneous catalysis requires attention in particular when dealing with solids that may show some solubility under the high T, p reaction conditions often applied using heterogeneous catalysts. Calcium methoxide, at the surface of CaO, is the real catalyst of the methanolysis of triglycerides. Because of its slight methanol solubility (Table 8.16) Ca(OCH3)2 acts mainly as a heterogeneous catalyst. Unexpectedly, the strong base character of MgO has resulted in the observation of low or no transesterification activity at 333 K [134, 152, 157]. Leclercq et al. [154] found that MgO and mixed (Mg, Al) oxides are active in methanolysis of oils but the experimental conditions (reaction time, 22 h; methanol/oil molar ratio, 275) excluded industrial use. However, strong base sites in solids are especially susceptible to catalyst pre-treatment; MgO activity is strongly dependent upon calcination temperature. Methanolysis of

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RSO (with alcohol/oil molar ratio of 75 : 1) at 338 K took 22 h for 65–69% total oil conversion over MgO calcined at 723 K in either air or nitrogen, but only 1 h for 35% conversion over a MgO catalyst calcined at 823 K [154]. Hence, more activation of the strong base sites in MgO occurred at high temperatures. Transesterification of SBO using MgO and Mg-Al calcined hydrotalcites (CHTs) shows a correlation with the catalyst basicity and texture [155]. The textural properties are affected by both the precursors and preparation method. MgO and CHT catalysts display at least four different types of basic surface sites. Calcination of hydrotalcites (at 573–773 K), catalyst precursors also known as layered double hydroxides (LDHs) or anionic clays, yields mixed oxides which present basic sites associated to structural hydroxyl groups and strong Lewis basic sites associated to Mn+–O2– acid-base pairs. Super-basic sites (desorbing CO2 at T > 623 K) promote transesterification also at very low temperature (373 K), whereas medium strength basic sites require higher temperatures (453 K). The FAME yields obtained using different MgO catalysts increase approximately with higher specific basicity of the catalyst. Both CHT and MgO catalysts are resistant to the presence of water (1%) in the reaction environment, and allow conversion of acid oils (up to 27% FFA), albeit with low conversion. PCT Int. Publ. No. WO 2006/050925 A1 to Santacesaria et al. [186] describes an industrial (batch or continuous) process for producing esters from vegetable oils or animal fats using MgO and CHTs. Heterogeneous base catalyst parameters were optimised in several instances [143, 147, 156]. A correlation between the basicity of the K2O/Al2O3 and Mg-Al hydrotalcite catalysts and their activity towards SBO methanolysis has been proposed [143, 156]. Kim et al. [147] described a solid superbase Na/NaOH/g-Al2O3 with almost the same catalytic activity under optimised reaction conditions as the conventional homogeneous NaOH catalyst despite the separation of the reactants in two phases. The activities of Na/ NaOH/g-Al2O3 catalysts in methanolysis of SBO correlated with their basic strengths. Similarly, the order of catalyst reactivity in transesterification of triolein with glycerol is MgO > hydrotalcite > Cs-sepiolite > Cs-MCM-41, in agreement with the base strength of the series [142]. Also the reaction rate of various solid basic catalysts (La2O3 > MgO > ZnO > CeO2) in glycerol transesterification with methyl stearate showed direct dependency with the base strength of each catalyst [187]. The activities of CaO and ZnO appear to be enhanced by the addition of MgO. Early attempts to use heterogeneous catalysts for the conversion of MeOH/LE-RSO (molar ratio 6 : 1) under near-reflux conditions used supported CaO catalysts, such as 9.2 wt% CaO/MgO, and resulted in a total oil conversion of over 95% in 12 h [152]. However, observed extensive soap formation indicates that most of the supported CaO was leaching out of the catalyst, thus favouring homogeneous catalysis.

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Simple carbonate salts such as CaCO3 and ZnCO3 have also been used as solid-base catalysts for transesterification [145]. Alcoholysis of SBO and beef tallow with ethylene-, diethylene-, triethylene-glycol and glycerol was carried out using M2CO3 (M = Na, K) and MCO3 (M = Mg, Ca, Zn) base catalysts [135]. Satisfactory and steady performance for methanolysis over weeks was achieved with CaCO3 catalysts, even though at relatively high temperatures (> 473 K). Major advantages of CaCO3 are low cost, availability and the extremely low solubility in fats and oils. Calcium carbonate catalysed SBO/ EtOH reaction at 513 K for 18 min yielded only <5% oil conversion, but high conversions (>95 % at 533 K) were obtained using a methyl ester of soybean oil (SBME) as a co-solvent [135]. Higher reaction temperatures are not considered to be a problem for flow reactors where heat exchangers can be readily used to minimise energy costs. US Patent Appl. No. 2003/0149289 A1 to Suppes [188] claims that carbonate catalysts (especially CaCO3) can be used efficiently in the production of biodiesel from TG mixtures with high FFA contents (reaction conditions: T = 513–543 K, p < 10 MPa, t = 0.7–10 h, presence of a hydrophobic solvent). The presence of 5 wt% fatty acids did not inhibit the CaCO3 catalyst; the free fatty acids were regularly esterified. The identity of the active site has not been established. As esterification of FFA produces water (Eqn 8.6), appreciable carbonate solubility in the system casts doubt on the kind of catalysis involved (heterogeneous or homogeneous). The robust morphology of the CaCO3 catalyst is suitable for use in packed-bed reactors. Catalyst removal requires only a screening process at reactor discharge. Carbonate species have shown leaching phenomena under mild reaction conditions. This has been observed for K2CO3 in K2CO3/Al2O3 and probably also for K2CO3/MgO used as transesterification catalysts for RSO with methanol at 333 K [152]. Most likely, a homogeneous catalysis mechanism was involved. Certain carbonate systems are also known to promote glycerolysis [189]. Zeolites that have been modified by ion exchange of alkali cations or by decomposition of an occluded alkali metal salt are interesting solids which catalyse reactions that require a base site. The base strength of the alkali ion-exchanged zeolite increases with greater electropositivity of the exchange cation. Occlusion of alkali-metal oxide clusters in large pore zeolite cages via decomposition of impregnated alkali metal salts results in a further increase in basicity of these materials. The use of NaOx/NaX zeolites in transesterification of MeOH/SBO (molar ratio 6 : 1) at 393 K for 24 h resulted in 57–94% total oil conversions [145]. Also in this case some catalyst leaching was reported. Suppes et al. [145] have described methanolysis of SBO in the presence of faujasite and ETS-10 (microporous titanosilicate) zeolites. NaX and ETS-

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10 are predominantly alkali cation-exchanged zeolite type materials. The basicity of NaX and ETS-10 zeolites was enhanced by ion exchange with higher electropositive metals like K and Cs. NaX contained occluded NaOx. ETS-10 catalysts provide higher conversions than zeolite-X type catalysts (see Table 8.14). Much higher conversions were reported for pre-treated zeolites. Conversions to methyl esters in excess of 90% were achieved at 393 K with residence times of 24 h. Although ETS-10 always gave better conversions of TGs than zeolite-X type catalysts, occlusion of the X type catalysts enhanced activity to levels similar to ETS-10. The increased conversions were attributed to the much higher basicity of ETS-10 zeolites and larger pore structure that improves diffusion. Figure 8.6 correlates Sanderson’s intermediate electronegativity [190] of zeolites with methyl ester yield. Zeolite catalysts also performed better than metal catalysts. High catalytic activities for ETS-10 were obtained at 373 K even for 2.6 wt% FFA containing SBO. However, poor conversions were reported with a high excess of FFA (27 wt% oleic acid). No reasonable explication has been given for the different behaviour in case of low and high FFA concentrations. US Patent No. 5,508,457 to Bayense et al. [138] reports the use of strong Brønsted type solid bases as alkali ETS-4 and ETS-10 for alcoholysis of 100 K-ETS10 (K, Cs) ETS10

Methyl esters (wt%)

80

ETS10

Cs-ETS10

60

40

20

(K, Cs)X

KX CsX

NaX

0 2.8

3.0 3.2 3.4 3.6 Sanderson’s intermediate electronegativity

3.8

8.6 Soybean methyl ester yield (wt%) at 393 K as a function of intermediate electronegativity calculated according to Sanderson’s intermediate rule [190]. Electronegativity was calculated on the assumption of 60% ion exchange for Cs and 95% for K (after ref. [145]).

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TGs. Batch experiments (0.23 wt% catalyst loading, 493 K, 2.1 MPa) with MeOH/SBO = 4.2 : 1 resulted in 69.0% total oil conversion and 52.6% ester yield for ETS-10 and 96.9% conversion with ester yield of 85.7% in 1.5 h for ETS-4. When tallow was used as a feedstock, conversions and ester yields were 30.6% and 19.1% for ETS-10 and 44.1% and 29.6% for ETS-4, respectively, under the same reaction conditions. It should be considered that basic sites in the channels of these zeolites are inaccessible to TG molecules. Their effective radius prevents entering through the small pore openings of ETS-4 (diameter of 3.7 Å) or even ETS-10 (diameter of about 8 Å). A homogeneous-like reaction mechanism may be envisaged in which alkoxides (RO–) formed within the zeolite pores interact with TG molecules outside the pores [20]. The high catalytic activity of several heterogeneous base catalysts (e.g. ETS-10, NaX) at temperatures below 413 K gives processes based on these catalysts distinctive competitive advantages over conventional processes based on homogeneous catalysis at temperatures between 323 and 343  K. The commercial viability will likely be determined by the cost and lifetime of the catalyst. It is desirable to develop more efficient and cheaper catalysts for transesterification of triglycerides with methanol for commercial production. The application of solid catalysts in liquid-phase reactions involving large molecules such as triglycerides is limited by poor reactant/catalyst contacting from either pore diffusion limitations or low active site availability for the catalytic reaction. Diffusion controlled inadequacies may be overcome by increasing the pore size of catalytic materials. Mesoporous catalytic materials, which allow tunable pore sizes from 2 to 30 nm, may be used [191]. Mesoporous catalysts are more active than catalysts containing many micropores for the difficulty of the bulky triglyceride molecules to reach the basic catalytic sites inside the micropores. A strategy for developing such a solid TG transesterification catalyst is to immobilise known basic moieties such as bicyclic amidines and guanidines onto a mesoporous support that has a large surface area and high dispersion of the catalytic active sites [192]. Guanidines preserve their catalytic activity even when immobilised. Gelbard and Vielefaure–Joly [193] reported more than 90% yield of methyl esters within 15 min when the reaction was catalysed by either free or immobilised guanidines (on polystyrene). Transesterification of SBO with MeOH has been carried out on heterogenised alkylguanidines anchored to modified polystyrene or MCM-41, or immobilised in microporous systems (encapsulated in zeolite Y or entrapped in SiO2 sol-gel matrices) [35]. Longer reactions times were needed in comparison to the corresponding homogeneous phase catalysis. Alkylguanidines supported on PS only showed a slightly lower activity than homogeneous catalysts. Alkylguanidines supported on mesoporous MCM-41 showed low initial catalytic conversion of TG – due to pore diffusion – but

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significant improvement at higher reaction time. Apparently, even larger pore diameters than available on MCM-41 are required for the relatively large TG molecules. Alkylguanidines on zeolite Y were the least active. Also the transesterification of b-ketoesters catalysed by TBD-MCM-41 has been investigated [194]. Similarly, the activities of TBD grafted to the pores of MCM-41 and a porous styrene-divinylbenzene resin for the formation of the monoglyceride from lauric acid and glycidol have been reported [195]. Barrault et al. [196] prepared MgO/MCM-41 and MgO/AlMCM-41 catalysts for transesterification of methyl esters and glycerol. Selectivity to monoglycerides has been enhanced significantly over MCM-41 as a result of the shape selectivity effect. Similarly, Corma et al. [142] investigated the catalytic activity of Cs-MCM-41 in the transesterification of TG with glycerol to produce MG. Biodiesel production has also been attempted over strong base anionicexchange resins in the hydroxide form [2, 197] (see Table 8.13). Some commercially available anion-exchange resins are Dowex® 550A (Dow Chemical Company) and Amberlyst® A26 (Rohm & Haas). As ion-exchange resins have the capability of removing trace metal ions, the oxidative stability of the final product is enhanced. Tables 8.12 and 8.17 show some potential problems with heterogeneous catalysts for biodiesel synthesis. Although some heterogeneous catalysts show reasonable activity, they generally require high T, p reaction conditions. Undoubtedly, the alkalinity of a given compound is a key factor which determines its catalytic activity in alcoholysis, but is not the only one. The degree of dispersion in the reaction system has a considerable effect on the level of catalytic activity, which is determined by diffusion. Due to the slow diffusion of triglycerides through the catalyst pores in heterogeneous catalysts such as supported metals, basic oxides and zeolites, the transesterification reaction is slow and a higher alcohol-to-glyceride molar ratio is required to achieve appreciable conversion of above 70%. The true nature of the active sites of some solid bases (e.g. Ba(OH)2, CaCO3, ETS-4, ETS-10) remains obscure. Ba(OH)2 shows non-negligible solubility in methanol and CaCO3 in water. Other active base catalysts with no solubility in alcohols (such as ETS-4 and ETS-10) most likely carry out catalysis by a homogeneous-like mechanism. This implies that the catalytic Table 8.17 Potential problems with heterogeneous catalysts for biodiesel synthesis ∑ ∑ ∑ ∑ ∑

Catalyst solubility in reagents and/or products Obscure reaction mechanism Deleterious effect of polar compounds on acid sites Leaching and catalyst deactivation Catalyst removal problems  

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effect can be lost after the formation and leaching out of the catalytically active RO– species. Catalysts that have significant solubility also bring with them catalyst removal problems associated with both heterogeneous and homogeneous catalysts. Commercial biodiesel production is operated using basic heterogeneous catalysts containing phosphate or Group IV metal organophosphorated compounds [157].

8.4.3 Catalysis by solid acids Heterogeneous acid-catalysed transesterification of TGs has not been investigated as much as the base-catalysed reaction (see Table 8.18). Solidacid catalysis as an active research area for biodiesel synthesis has been largely ignored due to pessimistic expectations in terms of reaction rates and undesired side reactions. Even though solid-acid catalysts have been applied effectively in the esterification of carboxylic acids, the use of these catalysts to obtain high conversion of triglycerides to biodiesel generally necessitates much higher reaction temperatures than base catalysts because of their lower activity for transesterification [198]. Amberlyst®15 is a notable exception. Fundamental studies dealing with the reaction of model compounds of TGs on solid acids are lacking. One important problem with acid catalysts in general is their lower reaction rates compared to base catalysts. Even lower rates can be expected for solid acids as compared to homogeneous acid catalysts on the same weight basis. Thus, generally, solid-acid catalysts need high temperatures, high catalyst loading, and/or large reactors in order to attain satisfactory biodiesel production rates. The reaction mechanism for heterogeneous acid-catalysed esterification is in principle similar to the homogeneously catalysed one [199]. Another main concern expressed has been the possibility of unwanted side reactions, in particular double dehydration of glycerol to form acrolein and water. However, this acid-catalysed reaction becomes important only above about 523 K [20]. On the other hand, attractive aspects are the ability of solid acids to catalyse both esterification (see Section 9.2) and transesterification reactions simultaneously and the possibility of reuse. Solid-acid catalysts eliminate the corrosion problems and environmental threat of liquid acids. Solid acids have the advantage of being easily removable by filtration and can be used for large-scale production [200]. Rohm & Haas has recently developed a commercial esterification/transesterification process for the conversion of high-acid feedstocks using AmberlystTM BD20 solid-catalyst technology (see Section 15.3.1, pp. 732–6). General requirements for a good solid-acid catalyst for biodiesel synthesis by (trans)esterification are appropriate acid site strength, high acid concentration (to secure an acceptable reaction rate), an interconnected system of large pores

Table 8.18 Transesterification of vegetable oils and animal fats by solid acids Catalyst class Catalyst(s)

Raw Alcohol(s) Reaction conditions material(s)

Metal

SBO

Zn/I2

MeOH

Ester Reference(s) yield (%)

338 K, 0.1 MPa, 26 h, ROH/VO = 42 93a, 96b

c

Cation-exchange Amberlyst-15/31/35/36 VO MeOH 333 K, 0.1 MPa   resins Amberlyst-15 SNO MeOH 333 K, 0.1 MPa, 8 h, ROH/VO = 6 Amberlyst-15, Lauric acidd 2-Ethylhexanol 423 K, >0.1 MPa, 2 h, ROH/VO = 1–5   Nafion-NR50 K2411, K1481 Oleic acidd MeOH 313 K, 13.5–16 MPa, 1–3.5 h,   ROH/VO =15–60 Amberlyst-15, SBO + PAf MeOH 358 K, > 0.1 MPa, 3 h, ROH/VO = 98   Nafion-NR50   Lewatit SPC 118 BG VO, VOg MeOH 333 K, 0.5 MPae

[164]

–

[201]

0.7 70–90

[2] [202]

17–90

[113]

46–73

[10] [203, 204]

100

[132]

51

[205]

Zeolites KNO3/KL CPKO, CCNO MeOH 473 K, 5 MPa, 4 h, ROH/VO = 6   H-ZSM-5, HY Acetic, benzoic EtOH, BuOH, 358–483 K, 0.1 MPa, 4–48 h,   and phthalic   i-PrOH   ROH/VO = 1.2–5   acidd

71–77 6–96

[206] [207]

Mesoporous   silicas

HMS-SO3H, SBA-SO3H SBO + PAf

MeOH

358 K, > 0.1 MPa, 3 h, ROH/VO = 98 60–65

[140] [208] [209]

365

Mixed metal Al, Ga, Fe(III) PKO MeOH 473 K, > 0.1 MPa, 5 h, ROH/VO = 7.5 > 50   oxides   orthophosphates WO3/ZrO2 SNO MeOH 473 K, > 0.1 MPa, 5 h, ROH/VO = 15 97   WO3/ZrO2 – Al2O3 SBO MeOH 523–573 K, 0.1 MPa, 20 h, > 90   ROH/VO = 40

[10]

Biodiesel catalysis

–

Clays KSF montmorillonite RSO MeOH, EtOH, 493 K, 5.2 MPa, 6 h, ROH/VO = 30   PrOH, i-PrOH   KSF montmorillonite RSOh MeOH 443 K, 0.1 MPa, 1 h, ROH/VO = 9

Superacids   a

SO42–/SnO2, SO42–/ZrO2 SO42–/ZrO2 SO42–/ZrO2 SO42–/ZrO2

Raw Alcohol(s) Reaction conditions material(s)

Ester Reference(s) yield (%)

CPKO CCNO SBO Lauric acidd

90 86 92–98.6 < 90

MeOH MeOH MeOH, EtOH MeOH, PrOH

473 K, 5 MPa, 4 h, ROH/VO = 6 473 K, 5 MPa, 4 h, ROH/VO = 6 393 K, >0.1 MPa, 1 h, ROH/VO = 20 333–453 K, 1–3.3 h, ROH/VO = 3–5

[206] [206] [210] [202]

Without co-solvent.         With co-solvent (DMSO). c Babassu, CRO, PKO, PMO, SBO. d Esterification. e Pre-esterification step. f Palmitic acid. g High FFA content. h Microwave-enhanced. b

Biodiesel science and technology

Catalyst class Catalyst(s)

366

Table 8.18 Continued

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(in order to minimise diffusion problems), hydrophobic surface (to promote preferential absorption of oily species and avoid deactivation by polar byproducts, such as water and glycerol) and low cost. Factors promoting organic reactions catalysed over solid acids comprise the strength of the acid sites, the Brønsted or Lewis nature, and active site location [211]. In comparison to liquid acids, solid acids encompass different populations of acid sites varying in nature and strength. In a large number of solid acids the acidity varies from mild to superacid level. Conflicting reports in the literature about the strength and nature of the acid sites intervening in catalysis may derive from poor material’s characterisation or from the use of different reaction conditions. The acidity can be tuned and adapted to the particular reaction thus largely avoiding undesirable reactions from occurring. The main problems for solid-acid catalysts concern the diffusivity of large molecules through pores and cavities of solid materials and the deleterious effect of water (and some polar compounds such as methanol and glycerol) on acid sites, which affects the acid strength of these sites. The solid acid must show water resistance in order to avoid adsorption of the water byproduct that will lead to deactivation. Water covering the surface of solid acids prevents adsorption of organics. The hydrophobicity of the catalyst surface and the density of the acid sites are therefore of paramount importance in determining the catalyst’s activity and selectivity. With the possibility of tuning the acidity and controlling the pore size, the selectivity in organic reactions can be improved. Various classes of solid-acid catalysts are potentially available with sufficient acid strength to be effective in transesterification, such as ionexchange resins, pillared clays, zeolites in acid form, mesoporous molecular sieves, Lewis acids, solid superacids such as promoted (mixed) metal oxides, carbon-based polysulphonic acids, functionalised polymers and others. Some typical examples of solid-acid catalysts that have been investigated as potential replacements of mineral acids in esterification and transesterification reactions are tungsten oxides [209, 212–214], sulphated zirconia [202, 206, 210, 212, 215–217], sulphonated saccharides [218–221], organosulphonic functionalised mesoporous silicas [10, 191, 222, 223], Amberlyst®15 [201, 202, 212], and Nafion® resins [202, 212, 217, 224–227]. The majority of publications on transesterification catalysed by solid acids have focused on the reaction of b-ketoesters [194, 228–232] using H-MCM-41, TBD/MCM-41, Hb, HY, H-mordenite, H-ZSM-5, H-ZSM-12, kaolin, STO, Amberlyst®15, Amberlyst®16 using C4-C12 alcohols. Larger pore zeolites and dealuminated zeolites showed higher yields, suggesting that catalytic activity depends on reagent intra-pore diffusion, acid strength and surface hydrophobicity. Various catalysts active for transesterification of b-ketoesters, such as Envirocat EPZG, natural kaolinite clay, B2O3/ZrO2, sulphated SnO2 and zeolites, could be effective in the transesterification of triglycerides and deserve testing.

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Commercial cation-exchange organic resins such as Dowex® 2030 (Dow Chemical Company) or Amberlyst® 36 (Rohm & Haas) are strong acids and good esterification catalysts. In general, when using organic resins, the catalytic activity strongly depends on their swelling properties. Resin swelling capacity is fundamental since it controls substrate accessibility to the acid sites and therefore affects its overall reactivity. Once swelled, the resin pores usually become macropores. Big molecules with long hydrocarbon chains (such as TG or FFA) then show no diffusion limitations and can readily access the acid sites in the bulk. At variance to most solid-acid catalysts, some resins such as Amberlyst® 15 catalyse appreciably both esterification and transesterification reactions under mild reaction conditions (see Table 8.18) due to their high concentration of acid sites [212]. However, their stability becomes an issue when resin-type catalysts are used at higher temperatures (for higher reaction rates, reactive distillative applications, or catalyst regeneration). Use of Amberlyst®15 for transesterification thus requires mild reaction conditions to avoid degradation of the catalyst. At 333 K and atmospheric pressure for a molar ratio MeOH/SNO = 6 : 1, a conversion of only 0.7% was achieved (see Table 8.18) [2]. Brazilian vegetable oils (babassu, corn, palm, palm kernel and soybean) were transesterified over ion-exchange resins (Amberlyst®15/31/35/36) [201]. The catalytic activity of the resins depends on the FA composition of the VO employed. The methyl ester yield is higher for palm kernel oil (PKO) and babassu oil than for SBO, probably due to their higher content of shorter-chain FA. A recent commercial solid-catalyst esterification/transesterification technology development is described in Section 15.3.1, pp. 732–6. Nafion ® (a perfluorosulphonated ionomer) is non-porous whereas Amberlyst® has large pores. Although Nafion® has very strong acid sites able to catalyse a great number of reactions occurring through carbocations, its low surface area is a serious handicap. Ion-exchange resins such as Nafion® NR50 are rapidly deactivated due to poor textural properties and also fail on thermal stability. However, recently developed high-surfacearea Nafion®-silica composites [233] are expected to substitute other less environment-friendly acids such as HF or H2SO4, and deserve attention as solid-acid transesterification catalysts. Mittelbach et al. [132] compared the activities of a series of layered aluminosilicates with H2SO4 for alcoholysis (MeOH, EtOH, PrOH, i-PrOH) of RSO (5 wt% catalyst, ROH/RSO = 30 : 1). The sulphuric acid catalyst showed the highest activity. The most active solid catalysts were activated by sulphuric acid impregnation. Activated KSF montmorillonite showed almost total conversion after 6 h of reaction at 493 K and 5.2 MPa. However, at this temperature some side reactions were observed, namely dimerisation of alkyl esters and formation of glycerol ethers. In less severe reaction conditions the side reactions were suppressed but ester yields were affected (70% yield

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after 8 h). Compared with liquid acids such as H2SO4, clay catalysts produce a cleaner biodiesel product due to their bleaching activity. Unrefined oils or waste cooking oils could be employed as feedstock without pre-treatment. The catalyst had to be reactivated after each run, suggesting that some leaching of sulphuric acid took place. Consequently, a homogeneous reaction mechanism may have contributed to the overall catalytic activity. Reusability of the catalyst was compromised by leaching of the sulphate species. Recently, KSF montmorillonite was also used in microwave-enhanced methanolysis of RSO [205]. The degree of acidity of KSF montmorillonite, as calculated by the Hammett acidity function, ranges between H2SO4 and HNO3. Pillared clays (PILC) are another class of solid-acid catalysts. Kloprogge et al. [234] have described the use of a variety of pillared clays, which exhibit a 2D porous structure with acidic properties comparable to those of zeolites, to produce biofuels from VOs such as CPO, SNO and canola. Most ion-exchange resins are not stable at temperatures above 413 K. For reactions requiring higher temperatures, inorganic acid catalysts such as zeolites are generally more suitable. Zeolites such as ZSM-5 (UOP or Zeolyst International) or ultrastable Y-zeolite (USY, Tosoh Corporation) as solid-acid catalysts enable reactions with low acid pretentions (e.g. Beckmann rearrangement), medium strength acid requirements (e.g. acetal formation, Friedel–Crafts alkylations) as well as those reactions demanding strong acid sites (e.g. dehydration of aliphatic alcohols, skeletal isomerisation of hydrocarbons). Strongly acidic zeolites also catalyse esterification of carboxylic acids with alcohols as well as their hydrolysis. In reactions involving bulky reactants (as in the case of transesterification of fatty acids), it is far more indicated to use new long-range ordered mesoporous materials (e.g. MCM-41 or MCM-48) as solid catalysts characterised by large pores, provided that they exhibit the required acidity. Kaita et al. [140] designed various aluminum phosphate catalysts (molar ratio Al/P = 1 : 3 to 1 : 0.01) for transesterification of PKO with methanol. These durable and thermostable catalysts with good selectivity to FAME (< 0.8% ether formation) required high temperatures (473 K) and a molar ratio MeOH/PKO = 75 : 1. Methyl ester yields (> 50%) were insufficient for industrial application. Heteropolyacids (HPAs), characterised by a large number of strongly acidic sites, have occasionally been applied to transesterification [235, 236]. HPAs show opportunities for substituting environmentally unfriendly Brønsted and Lewis acids, such as H2SO4, AlCl3, BF3 and ZnCl2. Sunita et al. [208] have compared zirconia-supported isopoly- and heteropolytungstates in methanolysis of SNO at 473 K and MeOH/VO molar ratio of 15 : 1. The most active catalyst (WO3/ZrO2) gave 97% oil conversion and also efficiently catalyses methanolysis of mustard and sesame oil. The deactivated catalyst could be regenerated by calcination without appreciable loss in activity.

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It appears that other solid superacids promote the transesterification of vegetable oils as well as the esterification of free fatty acids. In contrast to zeolites, sulphated zirconia (SO42–/ZrO2) and related promoted oxides can behave as strong acid to superacid solids. As the acid strength of SO42–/ZrO2 equals that of pure H2SO4 [237] this would imply that it is not really a solid superacid but a strong acid. Sulphated zirconia (SO42–/ZrO2) and tungstated zirconia (WO3/ZrO2) exhibit high catalytic activities for various reactions. The acid strength of SO42–/SnO2 exceeds that of SO42–/ZrO2 [238]. Tungstated zirconia-alumina shows particularly high activity for transesterification of vegetable oils (e.g. 90% yield in methanolysis of SBO at 473–573 K after 20 h) and for esterification of free fatty acids [209]. The activity of the catalyst was maintained for up to 100 h. High sulphur content ZrO2-based catalysts (from chlorosulphonic acid as a source of sulphate ions) exhibit higher catalytic activity than conventional sulphated zirconia, albeit without testing for methanolysis [239]. Jitputti et al. [206] have tested various solid catalysts (ZrO2, ZnO, SO42–/SnO2, SO42–/ZrO2, KNO3/KL zeolite and KNO3/ZrO2) for transesterification of crude palm kernel oil (CPKO) and crude coconut oil (CCNO). The superacid solids SO42–/SnO2 and SO42–/ZrO2 provided both the highest yield of methyl esters (90.3%) for CPKO, whereas SO42–/ZrO2 showed the highest yield (86.3%) for CCNO. ZnO has considerable potential for transesterification catalysis of both CPKO and CCNO. Zirconia, with acidic and basic properties, exhibits the lowest catalytic activity. Recently, Garcia et al. [210] investigated sulphated zirconia as a heterogeneous catalyst in the transesterification of SBO and simultaneous esterification of fatty acids with methanol and ethanol. Although the catalyst is very active under optimised conditions (393 K, 1 h, 5 wt% catalyst, ROH/VO molar ratio = 20 : 1), with conversions of 98.6% (methanolysis) and 92% (ethanolysis), the catalyst is deactivated rapidly. Sulphated zirconia also tends to form volatile sulphur compounds during catalysis [240]. Finally, López et al. [241] described the catalytic performance for (trans)esterification of three thermally robust zirconia catalysts: titanic zirconia (TiZ), sulphated zirconia and tungstated zirconia (WZ). TiZ shows greater transesterification activity than WZ, as opposed to esterification. Heterogeneous catalytic conversions with hydrous SnO2 were used for the transesterification of ethyl acetate at 443–483 K, but not yet for triglycerides [242]. SnO is active for SBO methanolysis [167]. Zn/I 2 was found to be a practical and effective catalyst for the transesterification of SBO with methanol [164]. The high catalytic activity is not associated with ZnI2. Tentatively, a Lewis acid mechanism was proposed. Advantages of the use of Zn/I2 (with co-solvent) are operational simplicity, mild reaction conditions and high conversion (96% for 5 wt% catalyst at 338 K with MeOH/SBO molar ratio of 42 : 1 after 26 h in the presence of dimethyl sulphoxide (DMSO)). The catalytic activity was only slightly affected by 1.5 wt% H2O and free fatty acids (acid value of 3 mg

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KOH/g), with a decrease in oil conversion to 85%. The system may be a promising alternative catalyst for biodiesel production when the feedstock does not meet the requirements for base-catalysed processes. Recently, sulphonated incompletely carbonised organic material (such as saccharides) was reported to act as a solid (trans)esterification catalyst [218]. A drawback of the method is the hugh amount of H2SO4 needed for sulphonation, which is significantly higher than the direct use of H2SO4 for esterification [243]. Moreover, reproducibility appears to be problematic. The catalytic activity of strong Lewis acids such as titanium (IV) alkoxides Ti(OR)4 [169, 182, 183] can provide effective alternatives to traditional Brønsted base catalysts. However, many of these catalysts suffer from problems of cost, toxicity, water poisoning and/or difficulty of removal from the product. The synthesis of biodiesel via (solid) acid catalysis was recently reviewed by Lotero et al. [5, 20]. Acid catalysts are in great need for the transesterification of triglycerides with high content of free fatty acids. Rothenberg [244] has described use of an undisclosed solid-acid catalyst in a reactive distillative process for biodiesel production from high-FFA oils (see also Section 11.2). Further development of heterogeneous acid catalysts which esterify and transesterify simultaneously is highly desirable.

8.5

Bibliography

G. Rothenberg, Catalysis. Concepts and Green Applications, Wiley-VCH, Weinheim (2008). G. Centi and R.A. van Santen (eds), Catalysis for Renewables, Wiley-VCH, Weinheim (2007). G.P. Chiusoli and P. Maitlis, Metal Catalysis in Industrial Organic Processes. Fundamentals and Applications, The Royal Society of Chemistry, Cambridge (2006). G. Knothe, J. Van Gerpen and J. Krahl (eds), The Biodiesel Handbook, AOCS Press, Urbana, IL (2005). R.H. Crabtree, The Organometallic Chemistry of the Transition Metals, Wiley-Interscience, New York, NY (2005). P.W.N.M. van Leeuwen, Homogeneous Catalysis, Kluwer Academic Publishers, Dordrecht (2004). J. Hagen, Industrial Catalysis, Wiley-VCH, Weinheim (1999).

8.6

References

[1] J. Graille, P. Lozano, D. Pioch and P. Geneste, Alcoholysis tests for vegetable oils with natural catalysts for the production of diesel fuels, Oléagineux 40 (1985) 271–6.

372

Biodiesel science and technology

[2] G. Vicente, A. Coteron, M. Martínez and J. Aracil, Application of the factorial design of experiments and response surface methodology to optimize biodiesel production, Ind. Crops Prod. 8 (1998) 29–35. [3] H.J. Wright, J.B. Segur, H.V. Clark, S.K. Coburn, E.E. Langdon and R.N. DuPuis, A report on ester interchange, Oil & Soap 21 (1944) 145–8. [4] D.G.B. Boocock, S.K. Konar, V. Mao, C. Lee and S. Buligan, Fast formation of high-purity methyl esters from vegetable oils, J. Am. Oil Chem. Soc. 75 (1998) 1167–72. [5] E. Lotero, Y. Liu, D.E. Lopez, K. Suwannakarn, D.A. Bruce and J.G. Goodwin Jr., Synthesis of biodiesel via acid catalysis, I&EC Res. 44 (2005) 5353–63. [6] P. Felizardo, M.J.N. Correia, I. Raposo, J.F. Mendez, R. Berkemeier and J.M. Bordado, Production of biodiesel from waste frying oils, Waste Managm. 26 (2006) 487–94. [7] F. Ma, L.D. Clements and M.A. Hanna, The effects of catalyst, free fatty acids, and water on transesterification of beef tallow, Trans. ASAE 41 (1998) 1261–4. [8] X. Miao and Q. Wu, Biodiesel production from heterotrophic microalgal oil, Bioresour. Technol. 97 (2006) 841–6. [9] B. Freedman, E.H. Pryde and T.L. Mounts, Variables affecting the yields of fatty esters from transesterified vegetable oils, J. Am. Oil Chem. Soc. 61 (1984) 1638–43. [10] I.K. Mbaraka, D.R. Radu, V.S.-Y. Lin and B.H. Shanks, Organosulfonic acidfunctionalized mesoporous silicas for the esterification of fatty acid, J. Catal. 219 (2003) 329–36. [11] H.N. Basu and M.E. Norris (to Agricultural Utilization Research Institute), Process for the production of esters for use as a diesel fuel substitute using a non-alkaline catalyst, US Pat. 5,525,126 11 June 1996). [12] B. Freedman, R. O. Butterfield and E.H. Pryde, Transesterification kinetics of soybean oil, J. Am. Oil. Chem. Soc. 63 (1986) 1375–80. [13] R. Von Wedel, Technical Handbook for Marine Biodiesel, in Recreational Boats, Subcontract No. ACG- 7 16688-01 under Prime Contract No. DE-AC36-83CH10093, USDE (1999). [14] K.-S. Liu, Preparation of fatty acid methyl esters for gas-chromatographic analysis of lipids in biological materials, J. Am. Oil Chem. Soc. 71 (1994) 1179–87. [15] M. Canakci and J. Van Gerpen, Biodiesel production via acid catalysis, Trans. ASAE 42 (1999) 1203–10. [16] Y. Zhang, M.A. Dubé, D.D. McLean and M. Kates, Biodiesel production from waste cooking oil: 2. Economic assessment and sensitivity analysis, Bioresour. Technol. 90 (2003) 229–40. [17] Y. Zhang, M.A. Dubé, D.D. McLean and M. Kates, Biodiesel production from waste cooking oil: 1. Process design and technological assessment, Bioresour. Technol. 89 (2003) 1–16. [18] H. Fukuda, A. Kondo and H. Noda, Review. Biodiesel fuel production by transesterification of oils, J. Biosci. Bioengng. 92 (2001) 405–16. [19] F. Ma and M.A. Hanna, Biodiesel production: a review, Bioresour. Technol. 70 (1999) 1–15. [20] E. Lotero, J.G. Goodwin Jr., D.A. Bruce, K. Suwannakarn, Y. Liu and D.E. Lopez, The catalysis of biodiesel synthesis, Catal. 19 (2006) 41–83. [21] G.B. Bradshaw and W.C. Meuly (to E.I. du Pont de Nemours & Co.), Preparation of detergents, US Pat. 2,360,844 (24 Oct. 1944).

Biodiesel catalysis

373

[22] R.O. Feuge and A.T. Gros, Modification of vegetable oils. VII. Alkali catalyzed interesterification of peanut oil with ethanol, J. Am. Oil Chem. Soc. 26 (1949) 97–102. [23] E.J. Gauglitz Jr. and L.W. Lehman, The preparation of alkyl esters from highly unsaturated triglycerides, J. Am. Oil Chem. Soc. 40 (1963) 197–8. [24] M. Mittelbach, M. Wörgetter, J. Pernkopf and H. Junek, Diesel fuel derived from vegetable oils: preparation and use of rape oil methyl ester, En. Agric. 2 (1983) 369–84. [25] M.J. Nye, T.W. Williamson, S. Deshpande, J.H. Schrader, W.H. Snively, T.P. Yurkewich and C.L. French, Conversion of used frying oil to diesel fuel by transesterification: preliminary tests, J. Am. Oil Chem. Soc. 60 (1983) 1598– 601. [26] R.C. Lago, R.R. Szpiz, F.H. Jablonka, D.A. Pereira and L. Hartman, Extraction and transesterification of vegetable oils with ethanol, Oléagineux 40 (1985) 147–51. [27] D.G.B. Boocock, S.K. Konar, V. Mao and H. Sidi, Fast one-phase oil-rich processes for the preparation of vegetable oil methyl esters, Biomass Bioen. 11 (1996) 43–50. [28] J. Cvengroš and F. Povazanec, Production and treatment of rapeseed oil methyl esters as alternative fuels for diesel engines, Bioresour. Technol. 55 (1996) 145–50. [29] Y.-C. Bak, J.-H. Choi, S.-B. Kim and D.-W. Kang, Production of biodiesel fuels by transesterification of rice bran oil, Kor. J. Chem. Engng. 13 (1996) 242–5. [30] A. Coteron, G. Vicente, M. Martínez and J. Aracil, Biodiesel production from vegetable oils. Influence of catalysts and operating conditions, Recent Res. Developm. Oil Chem. 1 (1997) 109–14. [31] H. Noureddini, D. Harkey and V. Medikonduru, A continuous process for the conversion of vegetable oils into methyl esters of fatty acids, J. Am. Oil Chem. Soc. 75 (1998) 1775–83. [32] G. Vicente, Study of the Biodiesel Production. Ph.D. Thesis, Complutense University, Madrid (2001). [33] A.W. Schwab, M.O. Bagby and B. Freedman, Preparation and properties of diesel fuels from vegetable oils, Fuel 66 (1987) 1372–8. [34] G. Shapiro and M. Marzi, Facile and selective O-alkyl transesterification of primary carbamates with titanium (IV) alkoxides, J. Org. Chem. 62 (1997) 7096–7. [35] A.W. Schwab, G.J. Dykstra, E. Selke, S.C. Sorenson and E.H. Pryde, Diesel fuel from thermal decomposition of soybean oil, J. Am. Oil Chem. Soc. 65 (1988) 1781–6. [36] U. Schuchardt, R.M. Vargas and G. Gelbard, Alkylguanidines as catalysts for the transesterification of rapeseed oil, J. Mol. Catal. A: Chem. 99 (1995) 65–70. [37] U. Schuchardt and O.C. Lopes, Tetramethylguanidine catalyzed transesterification of fats and oils: a new method for rapid determination of their composition, J. Am. Oil Chem. Soc. 65 (1988) 1940–1 [38] U. Schuchardt, R. Sercheli and R.M. Vargas, Transesterification of vegetable oils: a review, J. Braz. Chem. Soc. 9 (1998) 199–210. [39] M. Cardone, M. Mazzoncini, S. Menini, V. Rocco, A. Senatore, M. Reggiani and S. Vitolo, Brassica carinata as an alternative oil crop for the production of biodiesel in Italy: agronomic evaluation, fuel production by transesterification and characterization, Biomass Bioen. 25 (2003) 623–36. [40] A. Bouaid, Y. Diaz, M. Martínez and J. Aracil, Pilot plant studies of biodiesel

374

[41]

[42] [43]

[44] [45] [46] [47] [48] [49] [50]

[51]

[52]

[53]

[54]

[55] [56] [57]

[58]

[59]

Biodiesel science and technology production using Brassica carinata as raw material, Catal. Today 106 (2005) 193–6. G. Vicente, M. Martínez and J. Aracil, Optimization of Brassica carinata oil methanolysis for biodiesel production, J. Am. Oil Chem. Soc. 82 (2005) 899– 904. D. Zhang, Crystallization Characteristics and Fuel Properties of Tallow Methyl Esters, M.Sc. Thesis, University of Nebraska, Lincoln, NE (1994). R. Alcantara, J. Amores, L. Canoira, E. Fidalgo, M.J. Franco and A. Navarro, Catalytic production of biodiesel from soybean oil, used frying oil and tallow, Biomass Bioen. 18 (2000) 515–27. Y. Tanaka and A. Okabe (to Lion Corp.), Verfahren zur Herstellung niederer Fettsäurealkylester, Germ. Offenl. DE 3020612 (5 May 1980). F. Ma, L.D. Clements and M.A. Hanna, Biodiesel fuel from animal fat. Ancillary studies on transesterification of beef tallow, I&EC Res. 37 (1998) 3768–71. F. Ma, L.D. Clements and M.A. Hanna, The effect of mixing on transesterification of beef tallow, Bioresour. Technol. 69 (1999) 289–93. D. Zheng and M.A. Hanna, Preparation and properties of methyl esters of beef tallow, Bioresour. Technol. 57 (1996) 137–42. H.D. Allen, G. Rock and W.A. Kline, Process for treating fats and fatty oils, US Pat. 2,383,579 (28 Aug. 1945). C.A. Fleischer (to Biodiesel Technologies, Inc.), Continuous esterification process, US Pat. Appl. 2003/0229238 A1 (11 Dec. 2003). G. Assmann, G. Blasey, B. Gutsche, L. Jeromin, J. Rigal, R. Armengaud and B. Cormary (to Henkel KaA), Continuous process for producing lower alkyl esters, PCT Int. Pat. No. WO 91/ 05,034 (18 Apr. 1991). S.L. Dmytryshyn, A.K. Dalai, S.T. Chaudhari, H.K. Mishra and M.J. Reaney, Synthesis and characterization of vegetable oil derived esters: evaluation for their diesel additive properties, Bioresour. Technol. 92 (2004) 55–64. X. Lang, A.K. Dalai, N.N. Bakhshi, M.J. Reaney and P.B. Hertz, Preparation and characterization of biodiesels from various bio-oils, Bioresour. Technol. 80 (2001) 53–62. E. Bikou, A. Louloudi and N. Papayannakos, The effect of water on the transesterification kinetics of cottonseed oil with ethanol, Chem. Engng. Technol. 22 (1999) 70–5. J.M. Encinar, J.F. González, J.J. Rodriguez and A. Tejedor, Biodiesel fuels from vegetable oils: transesterification of Cynara cardunculus L. oils with ethanol, En. Fuels 16 (2002) 443–50. J.M. Encinar, J.F. González, E. Sabio and M.J. Ramiro, Preparation and properties of biodiesel from Cynara cardunculus L. oil, I&EC Res. 38 (1999) 2927–31. H. Kurz, The catalytic alcoholysis of fatty oils with alcoholic potash, Fett Seifen 44 (1937) 144–5. H.A. Aksoy, I. Beceric, F. Karaosmanoğlu, H.C. Yatmaz and H. Civelekoğlu, Utilization prospects of Turkish raisin seed oil as an alternative engine fuel, Fuel 69 (1990) 600–3. P. Chitra, P. Venkatachalam and A. Sampathrajan, Optimisation of experimental conditions for biodiesel production for alkali-catalysed transesterification of Jatropha curcas oil, En. Sustain. Developm. 9 (2005) 13–18. L. Canoira, R. Alcántara, M. García-Martínez and J. Carrasco, Biodiesel from Jojoba oil-wax: transesterification with methanol and properties as a fuel, Biomass Bioen. 30 (2006) 76–81.

Biodiesel catalysis

375

[60] H. Junek, M. Mittelbach and F. Andreae, Verfahren und Vorrichtung zur Herstellung eines als Kraft- bzw. Brennstoff geeigneten Fettsäureestergemisches, Germ. Offenl. DE 3,727,981 (21 Aug. 1987). [61] B. Adler (to Dracowo Forschungs- u. Entwicklungs GmbH) Method for the continuous production of biomethanol diesel, PCT Int. Publ. No. WO 2003/076558 A2 (18 Sept. 2003). [62] S.V. Ghadge and H. Raheman, Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids, Biomass Bioen. 28 (2005) 601–5. [63] K. Krisnangkura and R. Simamaharnnop, Continuous transmethylation of palm oil in an organic solvent, J. Am. Oil Chem. Soc. 69 (1992) 166–9. [64] D. Darnoko and M. Cheryan, Continuous production of palm methyl esters, J. Am. Oil Chem. Soc. 77 (2000) 1269–72. [65] R.A. Korus, D.S. Hoffman, N. Bam, C.L. Peterson and D.C. Drown, Transesterification process and manufucture of ethyl ester from rapeseed oil, Proc. First Biomass Conf. of the Americas: Energy, Environment, Agriculture and Industry, Burlington, VT (30 Aug.–2 Sept. 1993), Vol. II, pp. 815–26. [66] C.L. Peterson, D.L. Reece, R. Cruz and J. Thompson, A comparison of ethyl and methyl esters of vegetable oil as diesel fuel substitutes, Proc. Alternative Energy Conf., Liquid Fuels from Renewable Resources, Nashville, TN (1992), pp. 99–110. [67] M.J. Nye and P.H. Southwell, Conversion of rapeseed oil to esters for use as diesel fuel, Proc. 5th Can. Bioenergy R&D Seminar (S. Hasnain, ed.), Elsevier Applied Science, London (1984), pp. 487–90. [68] R. Fillières, B. Benjelloun-Mlayeh and M. Delmas, Ethanolysis of rapeseed oil: quantitation of ethyl esters, mono-, di-, and triglycerides and glycerol by highperformance size-exclusion chromatography, J. Am. Oil Chem. Soc. 72 (1995) 427–32. [69] T. Wimmer (to Vogel und Noot Industrieanlagenbau GmbH), Transesterification process for the preparation of C1-5 alkyl fatty esters from fatty acid glycerides and monovalent lower alcohols, PCT Int. Publ. No. WO 92/009268 A1 (9 Jan. 1992). [70] U. Schuchardt, R.M. Vargas and G. Gelbard, Transesterification of soybean oil catalyzed by alkylguanidines heterogenized on different substituted polystyrenes, J. Mol. Catal. A: Chem. 109 (1996) 37–44. [71] A. Saydut, M.Z. Duz, C. Kaya, A.B. Kafadar and C. Hamanci, Transesterified sesame (Sesamum indicum L.) seed oil as a biodiesel fuel, Bioresour. Technol. 99 (2008) 6656–60. [72] G. Antolín, F.V. Tinaut, Y. Briceño, V. Castaño, C. Pérez and A.I. Ramirez, Optimisation of biodiesel production by sunflower oil transterification, Bioresour. Technol. 83 (2002) 111–14. [73] I.N. Dobrev (to Vekta OOD), Production of a fuel mixture with diesel fuel, Bulg. Pat. Appl. 105,409 (31 Dec. 2001). [74] G. Vicente, M. Martínez and J. Aracil, Integrated biodiesel production: a comparison of different homogeneous catalyst systems, Bioresour. Technol. 92 (2004) 297–305. [75] M. Mittelbach, F. Andrae and H. Junek, Verfahren und Vorrichtung zur Herstellung eines als Kraft- bzw. Brennstoffs geeigneten Fettsäureestergemisches, Austr. Pat. AT 386,222 B (15 Dec, 1987). [76] T. Wimmer, Verfahren zur Herstellung von Fettsäureestern kurzkettiger Alkohole, Austr. Pat. AT 394,571 B (15 Oct. 1991).

376

Biodiesel science and technology

[77] M.P. Dorado, E. Ballestreros, M. Mittelbach and F.J. López, Kinetic parameters affecting the alkali-catalyzed transesterification process of used olive oil, En. Fuels 18 (2004) 1457–62. [78] M.P. Dorado, E. Ballestreros, J.A. de Almeida, C. Schellert, H.P. Löhrlein and R. Krause, An alkali-catalyzed transesterification process for high free fatty acid waste oils, Trans. ASAE 45 (2002) 525–9. [79] G. Knothe, R.O. Dunn and M.O. Bagby, The use of vegetable oils and their derivatives as alternative diesel fuels, in Fuels and Chemicals from Biomass (B.C. Saha and J. Woodward, eds), ACS, Washington, DC (1997), pp. 172–208. [80] W.R. Trent (to Colgate-Palmolive-Peet Co.), Process of treating fatty glycerides, US Pat. 2,383,632 (28 Aug. 1945). [81] A. Center, E. Johnson, A. Nady, C. Wood and C.A. Fleisher (to Cornell Research Foundation Inc.), Continuous transesterification process, PCT Int. Publ. No. WO 2003/087279 A2 (23 Oct. 2003). [82] R.G. Stern, G. Hillion, J.-J. Rouxel and S. Leporq (to IFP), Process for the production of esters from vegetable oils or animal oils and alcohols, US Pat. 5,908,946 (1 June 1999). [83] M. Mittelbach, Herstellung von Fettsäuremethylestern und deren Verwendung als Dieselkraftstoff, Österr. Chemie Ztschr. 90 (1989) 147–50. [84] M. Markolwitz, Consider Europe’s most popular catalyst, Biodiesel Mag. 1 (2004) 20–22. [85] E.F. Caldin and G. Long, The equilibrium between ethoxide and hydroxide ions in ethanol and in ethanol-water mixtures, J. Chem. Soc. (1954) 3737–42. [86] L.M. Du Plessis, J.B.M. De Villiers and W.H. Van der Walt, Stability studies on methyl and ethyl fatty esters of sunflowerseed oil, J. Am. Chem. Soc. 62 (1985) 748–52. [87] A. Işigigür, F. Karaosmanoğlu and H.A. Aksoy, Methyl ester from safflower seed oil of Turkish origin as a biofuel for diesel engines, Appl. Biochem. Biotechnol. 45–46 (1994) 103–12. [88] Y. Shimada, Y. Watanabe, T. Samukawa, A. Sugihara, H. Noda, H. Fukuda and Y. Tominaga, Conversion of vegetable oil to biodiesel using immobilized Candida antarctica lipase, J. Am. Oil Chem. Soc. 76 (1999) 789–92. [89] G. Steinke, S. Schönwiese and K.D. Mukherjee, Alkali-catalyzed alcoholysis of crambe oil and camelina oil for the preparation of long-chain esters, J. Am. Oil Chem. Soc. 77 (2000) 367–71. [90] T. Wimmer (to Vogel & Noot Industrieanlagenbau GmbH), Process for the production of fatty acid esters of lower alcohols, US Pat. 5,399,731 (21 Mar. 1995). [91] K. Rethmann (to Recyclat Tierischer Rohstoffe GmbH), Verfahren zur Herstellung von Biodiesel mit verbesserter Kältestabilität, Germ. Pat. DE 10,245,758 A1 (1 Oct. 2002). [92] I. Lee, L.A. Johnson and E.G. Hammond, Use of branched-chain esters to reduce the crystallization temperature of biodiesel, J. Am. Oil Chem. Soc. 72 (1995) 1155–60. [93] A.A. Anggraini Süb, Wiederverwertung von gebrauchten Speiseölen/fetten im energetisch-technischen Bereich: Ein Verfahren und dessen Bewertung, Fortschr. Ber. VDI, Reihe 15: Umwelttechnik, Nummer 219, VDI Verlag, Düsseldorf (1999). [94] R. Türck (to Agrar-Technik GmbH), Verfahren zur Herstellung von Fettsäureestern einwertiger Alkylalkohole und deren Verwendung, Germ. Pat. DE 19,925,871 A1 (7 June 1999).

Biodiesel catalysis

377

[95] A.J. Yuste and M.P. Dorado, A neural network approach to simulate biodiesel production from waste olive oil, En. Fuels 20 (2006) 399–402. [96] H. Noureddini and D. Zhu, Kinetics of transesterification of soybean oil, J. Am. Oil Chem. Soc. 74 (1997) 1457–63. [97] M.W. Formo, Ester reactions of fatty materials, J. Am. Oil Chem. Soc. 31 (1954) 548–59. [98] K.J. Harrington and C.D’Arcy-Evans, Transesterification in situ of soybean seed oil, I&EC Prod. Res. Dev. 24 (1985) 314–18. [99] M. Koncar (to BDI-Biodiesel International AG), Method for production of carboxylate alkyl esters, PCT Int. Publ. No. WO 2007/012097 A1 (1 Feb. 2007). [100] N. Glasl, M. Mittelbach, M. Siebenhofer, E. Jeitler, W. Hammer, H. Gossler and M. Koncar (to BDI-Biodiesel International AG), Process for the production of carboxylic acid esters, US Pat. Appl. No. 2008/0227994 A1 (18 Sept. 2008). [101] F.R. Abreu, D.G. Lima, E.H. Hamú, S. Einloft, J.C. Rubim and P.A.Z. Suarez, New metal catalysts for soybean oil transesterification, J. Am. Oil Chem. Soc. 80 (2003) 601–4. [102] F.R. Abreu, D.G. Lima, E.H. Hamú, C. Wolf and P.A.Z. Suarez, Utilization of metal complexes as catalysts in the transesterification of Brazilian vegetable oils with different alcohols, J. Mol. Catal. A: Chem. 209 (2004) 29–33. [103] K.-H. Büttgen, M. Lindemann, J. Falkowsky, H.-P. Kubersky and G. Wollmann (to Cognis Deutschland GmbH), Verfahren zur Herstellung von Fettsäuremethylestern, Germ. Pat. DE 19,949,718 A1 (14 Oct. 1999). [104] S. Billenstein, B. Kukla and H. Stühler (to Hoechst AG), Process for the preparation of fatty acid esters of short-chain alcohols, US Pat. 4,668,439 (26 May 1987). [105] S. Billenstein, B. Kukla and H. Stühler (to Hoechst AG), Verfahren zur Herstellung von Fettsäureestern kurzkettiger Alkohole, Germ. Pat. DE 3,421,217 A1 (7 June 1984). [106] S. Zheng, M. Kates, M.A. Dubé and D.D. McLean, Acid-catalyzed production of biodiesel from waste frying oil, Biomass Bioen. 30 (2006) 267–72. [107] O. Rachmaniah, Y.-H. Yu, S.R. Vali, I. Tjondronegoro and A.S. Musfil, A study on acid-catalyzed transesterification of crude rice bran oil for biodiesel production, Paper presented at World Energy Congress, Sydney (2004). [108] M.J. Haas, P.J. Michalski, S. Runyon, A. Nuñez and K.M. Scott, Production of FAME from acid oil, by-product of vegetable oil refining, J. Am. Oil Chem. Soc. 80 (2003) 97–102. [109] F.J. Luxem and W.M. Troy (to Stepan Co.), Method of making alkyl esters under pressure, US Pat. 6,768,015 (27 July 2004). [110] I.B. Agra, S. Warnijati and Wiratni, Two steps ethanolysis of castor oil using sulfuric acid as catalyst to produce motor oil, Proc. World Renewable Energy Congress IV, Denver, CO (1996), Vol. 2, pp. 1025–8. [111] E. Crabbe, C. Nolasco-Hipolito, G. Kobayashi, K. Sonomoto and A. Ishizaki, Biodiesel production from crude palm oil and evaluation of butanol extraction and fuel properties, Process Biochem. 37 (2001) 65–71. [112] M.J. Haas, Improving the economics of biodiesel production through the use of low value lipids as feedstocks: vegetable oil soapstock, Fuel Proc. Technol. 86 (2005) 1087–96. [113] C. Vieville, Z. Mouloungui and A. Gaset, Esterification of oleic acid by methanol catalyzed by p-toluenesulfonic acid and the cation-exchange resins K2411 and K1481 in supercritical carbon dioxide, I&EC 32(9) (1993) 2065–8.

378

Biodiesel science and technology

[114] T. Dimmig, W. Radig, J. Haupt and T. Dittmar (to L.U.T. Labor- und Umwelttechnik Jena GmbH), Verfahren zur Herstellung von Fettsäuremethylestern aus Triglyceriden und Fettsäuren, Germ. Pat. DE 19,908,978 A1 (2 Mar. 1999). [115] M.J. Goff, N.S. Bauer, S. Lopes, W.R. Sutterlin and G.J. Suppes, Acid-catalyzed alcoholysis of soybean oil, J. Am. Oil Chem. Soc. 81 (2004) 415–20. [116] S. Siler-Marinkovic and A. Tomasevic, Transesterification of sunflower oil in situ, Fuel 77 (1998) 1389–91. [117] K.J. Harrington and C. D’Arcy-Evans, A comparison of conventional and in situ methods of transesterification of seed oil from a series of sunflower cultivars, J. Am. Oil Chem. Soc. 62 (1985) 1009–13. [118] H. Lepper and L. Friesenhagen (to Henkel KaA), Verfahren zur Herstellung von Fettsäureestern kurzkettiger aliphatischer Alkohole aus freie Fettsäuren enthaltenden Fetten und/oder Ölen, Eur. Pat. EP 0,127,104 A1 (5 Dec. 1984). [119] G. Demmering, C. Pelzer and L. Friesenhagen (to Henkel KaA), Method of producing lower-alkyl esters of fatty acids, PCT Int. Publ. No. WO 95/13343 A1 (31 Oct. 1994). [120] R. Stern, G. Hillion, P. Gateau and J.C. Guibet (to IFP), Procédé de fabrication d’une composition d’esters d’acide gras utilisables comme carburant de substitution du gazole avec de l’álcool éthylique hydrate et composition d’esters ainsi formés, Fr. Pat. 2,577,569 A1 (15 Feb. 1985). [121] Ex-Rohr Center GmbH and V. Kramaschke, Dieselkraftstoffsubstitut und Verfahren zu dessen Herstellung, Germ. Offenl. DE 19,807,519 A1 (21 Feb. 1998). [122] M.J. Nye, T.W. Williamson, S. Deshpande, J.H. Schrader, W.H. Snively, T.P. Yurkewich and C.L. French, Conversion of used frying oil to diesel fuel by transesterification: preliminary tests, J. Am. Oil Chem. Soc. 60 (1983) 1598– 601. [123] M.I. Al-Widyan and A.O. Al-Shyoukh, Experimental evaluation of the transesterification of waste palm oil into biodiesel, Bioresour. Technol. 85 (2002) 253–6. [124] D.B. Keyes, Esterification process and equipment, I&EC 24 (1932) 1096–103. [125] A.K. Khan, Research into Biodiesel Kinetics and Catalyst Development, Ph.D. Thesis, University of Queensland, Brisbane (2002). [126] H.A. Aksoy, I. Kahraman, F. Karaosmanoğlu and H. Civelekoğlu, Evaluation of Turkish sulphur olive oil as an alternative diesel fuel, J. Am. Oil Chem. Soc. 65 (1988) 936–8. [127] M. Canakci and J. van Gerpen, Biodiesel production from oils and fats with high free fatty acids, Trans. ASAE 44 (2001) 1429–36. [128] D. Kusdiana and S. Saka, Effects of water on biodiesel fuel production by supercritical methanol treatment, Bioresour. Technol. 91 (2004) 289–95. [129] N.B. Kyriakidis and G. Dionysopoulos, Preparation of fatty acid methyl esters from olive oil and other vegetable oils using aqueous hydrochloric acid-methanol, Analyst 108 (1983) 738–41. [130] R. Sridharan and I.M. Mathai, Transesterification reactions, J. Sci. Ind. Res. 33 (1974) 178–87. [131] D. Nimcevic, R. Puntigam, M. Wörgetter and J.R. Gapes, Preparation of rapeseed oil esters of lower aliphatic alcohols, J. Am. Oil Chem. Soc. 77 (2000) 275–80. [132] M. Mittelbach, A. Silberholz and M. Koncar, Novel aspects concerning acid catalyzed alcoholysis of triglycerides, Proc. 21st World Congr. Intl. Soc. Fat Research (OilsFats-Lipids), The Hague (1–6 Oct. 1995), Vol. 3 (1996), pp. 497–9.

Biodiesel catalysis

379

[133] A.S. Kulkarni, R.R. Khotpal, R.L. Mehta and H.A. Bhakare, Studies in sulfation and sulfonation of some semi-drying oils, PaintIndia 41 (1991) 41–2. [134] S. Gryglewicz, Rapeseed oil methyl esters preparation using heterogeneous catalysts, Bioresour. Technol. 70 (1999) 249–53. [135] G.J. Suppes, K. Bockwinkel, S. Lucas, J.B. Botts, M.H. Mason and J.A. Heppert, Calcium carbonate catalysed alcoholysis of fats and oils, J. Am. Oil Chem. Soc. 78 (2001) 139–45. [136] L.C. Hoang, J. Barbault, R. Prunet and P. Desbordes (to Huileries de l’Arceau), Procédé de transesterification catalitique de corps gras d’origine végétale ou animale et procédé de récupération des produits obtenus, Fr. Pat. 2,698,101 A1 (19 Nov. 1992). [137] R. Stern, G. Hillion and J.-J. Rouxel (to IFP), Process for the preparation of fatty acid esters and thus obtained high purity esters, Eur. Pat. EP 0,924,185 A1 (23 June 1999). [138] C.R. Bayense, H. Hinnekens and J. Martens (to Engelhard/Fina), Esterification process, US Pat. 5,508,457 (16 Apr. 1996). [139] C.R. Bayense, H. Hinnekens and J. Martens (to Engelhard/Fina), Esterification process, Eur. Pat. EP 0,623,581 A2 (4 May 1994). [140] J. Kaita, T. Mimura, N. Fukuoka and Y. Hattori (to Kao Corporation), Catalysts for transesterification, US Pat. 6,407,269 (18 June 2002). [141] K.J. Harrington and C. D’Arcy-Evans, A comparison of conventional and in situ methods of transesterification of seed oil from a series of sunflower cultivars, J. Am. Oil Chem. Soc. 62 (1985) 1009–13. [142] A. Corma, S. Iborra, S. Miquel and J. Primo, Catalysts for the production of fine chemicals, J. Catal. 173 (1998) 315–21. [143] W. Xie, H. Peng and L. Chen, Calcined Mg-Al hydrotalcites as solid base catalysts for methanolysis of soybean oil, J. Mol. Catal. A: Chem. 246 (2006) 24–32. [144] J. Connemann and J. Fischer, Biodiesel in Europe 1990, Paper presented at Intl. Liquid Biofuels Congress (unpubl.), Curitiba, PR, Brazil (19–22 July 1998); http// www.biodiesel.de. [145] G.J. Suppes, M.A. Dasari, E.J. Doskocil, P.J. Mankidy and M.J. Goff, Transesterification of soybean oils with zeolite and metal catalysts, Appl. Catal. A: Gen. 257 (2004) 213–23. [146] (S&T)2 Consulting Company, Economic Opportunities in Renewable Bio-resource Utilization, Report for Industry Canada (2001). [147] H.-J. Kim, B.-S. Kang, M.-J. Kim, Y.M. Park, D.-K. Kim, J.-S. Lee and K.-Y. Lee, Transesterification of vegetable oil to biodiesel using heterogeneous base catalyst, Catal. Today 93–95 (2004) 315–20. [148] L. Jeromin, E. Peukert and G. Wollmann (to Henkel KGaA), Verfahren zur katalytischen Umesterung von Fettsäureglyceriden mit niederen Alkanolen, Germ. Pat. DE 3,515,403 A1 (29 Apr. 1985). [149] J. Graille, D. Lozano, D. Pioch, P. Geneste and A. Guida, Esters méthyliques ou éthyliques comme carburant diesel de substitution, Oléagineux 37 (1982) 421–4. [150] W. Kiehtreiber (to EVVA – Schmiermittel Fabrik GmbH), Verfahren und Vorrichtung zur kontinuierlichen Herstellung von Fattsäureestern, Eur. Pat. EP 0,535,290 A1 (2 Sept. 1991). [151] L. Hartman, Methanolysis of triglycerides, J. Am. Oil Chem. Soc. 78 (1956) 129–32.

380

Biodiesel science and technology

[152] G.R. Peterson and W.P. Scarrah, Rapeseed oil transesterification by heterogeneous catalysis, J. Am. Oil Chem. Soc. 61 (1984) 1593–7. [153] G. Karavalakis, G. Anastopoulos, S. Stournas, E. Lois, F. Zannikos and D. Karonis, Calcium oxide-supported potassium iodide as a heterogeneous catalyst for biodiesel production, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [154] E. Leclercq, A. Finiels and C. Moreau, Transesterification of rapeseed oil in the presence of basic zeolites and related solid catalysts, J. Am. Oil Chem. Soc. 78 (2001) 1161–5. [155] M. Di Serio, M. Ledda, M. Cozzolino, G. Minutillo, R. Tesser and E. Santacesaria, Transesterification of soybean oil to biodiesel by using heterogeneous basic catalysts, I&EC Res. 45 (2006) 3009–14. [156] W. Xie, H. Peng and L. Chen, Transesterification of soybean oil catalyzed by potassium loaded on alumina as a solid-base catalyst, Appl. Catal. A: Gen. 300 (2006) 67–74. [157] V. Lecocq, S. Maury and D. Bazer-Bachi (to IFP), Method for producing alcoholic esters from triglycerides and alcohols using heterogeneous catalysts containing phosphate or an organophosphorated compound of a Group 4 metal, PCT Int. Publ. No. WO 2008/135665 A1 (13 Nov. 2008); FR 2008/000389 (21 Mar. 2008). [158] D.G. Cantrell, L.J. Gillie, A.F. Lee and K. Wilson, Structure-reactivity in MgAl hydrotalcite catalysts for biodiesel synthesis, Appl. Catal. A287 (2005) 183–90. [159] P. Hofmann (to Hüls AG), Verfahren zur Herstellung von Carbonsäurealkylestern, insbesondere Fettsäurealkylestern, und deren Verwendung als Dieselkraftstoff, Eur. Pat. EP 0,198,243 A2 (15 Mar. 1986). [160] Y. Pouilloux, S. Metayer and J. Barrault, Synthesis of glycerol monooctadecanoate from octadecanoic acid and glycerol. Influence of solvent on the catalytic properties of basic oxides, C.R. Acad. Sci., Ser. IIc: Chim. 3 (2000) 589–94. [161] B. Delfort, G. Hillion, D. Le Pennec, J.A. Chodorge and L. Bournay, Biodiesel production by a continuous process using a heterogeneous catalyst, Abstr. 226th ACS Natl. Mtg., New York, NY (7–11 Sept. 2003), FUEL-066. [162] L. Bournay, D. Casanave, B. Delfort, G. Hillion and J.A. Chodorge, New heterogeneous process for biodiesel production: a way to improve the quality and the value of crude glycerine produced by biodiesel plants, Catal. Today 106 (2005) 190–2. [163] M. Di Serio, R. Tesser, L. Pengmei and E. Santacesaria, Heterogeneous catalysts for biodiesel production, En. Fuels 22 (2008) 207–17. [164] H. Li and W. Xie, Transesterification of soybean oil to biodiesel with Zn/I2 catalyst, Catal. Lett. 107 (2006) 25–30. [165] A.K. Gupta, A.K. Bhatnagar and S. Kaul (to Council of Scientific and Industrial Research), Improved process for preparing fatty acid alkylesters using as biodiesel, PCT Int. Publ. No. WO 2005/063954 (14 July 2005). [166] O.A. Mascaretti and R.L.E. Furlan, Esterifications, transesterifications and deesterifications mediated by organotin oxides, hydroxides and alkoxides, Aldrichim. Acta 30 (1997) 55–68. [167] F.R. Abreu, M.B. Alves, C.C.S. Macêdo, L.F. Zara and P.A.Z. Suarez, New multi-phase catalytic systems based on tin compounds active for vegetable oil transesterification reaction, J. Mol. Catal. A: Chem. 227 (2005) 263–7. [168] M. Martinelli, C.S.P. Zarth, J.L.S. Sonego and M.E.B. Gomes, VO(acac) 2: homogeneous and heterogeneous system for transesterification of soybean oil, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007).

Biodiesel catalysis

381

[169] M. Gheorghiu, Process for the preparation of methyl fatty acid esters starting from natural oil or fat, methyl esters obtained in this way and use thereof, US Pat. 5,532,392 (2 July 1996). [170] T. Hirano and K. Tsuto (to Lonford Development Ltd), Method of producing fatty acid lower alkyl esters from fat and oil, US Pat. 6,090,959 A (18 July 2000). [171] T. Tateno and T. Sasaki, Process for producing fatty acid esters and fuels comprising fatty acid esters, Eur. Pat. EP 1,126,011 A2 (15 Feb. 2001). [172] R.G. Stern, G. Hillion, J.-J. Rouxel and S. Leporq (to IFP), Process for the production of esters from vegetable oils or animal oils and alcohols, US Pat. 5,908,946 A (1 June 1999). [173] Institut Français du Petrole, Procédé de fabrication d’esters à partir d’huiles végétales ou animales et d’alcools, Fr. Pat. 2,752,242 (8 Aug. 1996). [174] W. Xie and X. Huang, Synthesis of biodiesel from soybean oil using heterogeneous KF/ZnO catalyst, Catal. Lett. 107 (2006) 53–9. [175] Société Belge de l’Azote et des Produits Chimiques de Marly, An improved process for the preparation of higher aliphatic alcohols, UK Pat. GB-A-795573 (6 Apr. 1956). [176] S. Peter, R. Ganswindt, H.-P. Neuner and E. Weidner, Alcoholysis of triacylglycerols by heterogeneous catalysis, Eur. J. Lipid Sci. Technol. 104 (2002) 324–30. [177] B. Delfort, G. Hillion and I. Durand (to IFP), Procédé de fabrication de biocarburants; Transformation de triglycerides en deux familles de biocarburants: monoesters d’acides gras et acetals solubles du glycerol, Fr. Pat. 2,866,654 (26 Aug. 2005). [178] G. Hillion, B. Delfort and I. Durand (to IFP), Procédé de fabrication de biocarburants; Transformation de triglycerides en deux familles de biocarburants: monoesters d’acides gras et ethers solubles du glycerol, Fr. Pat. 2,866,653 (26 Aug. 2005). [179] W.A. Summers, An effective solution to the glycerin glut, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [180] C. Blandy, J.L. Pellegatta and B. Gilot, Catalytic properties of supported titanates in transesterification, J. Catal. 150 (1994) 150–4. [181] H. Deleuze, X. Schultze and D.C. Sherrington, Reactivity of some polymer-supported titanium catalysts in transesterification and epoxidation reactions, J. Mol. Catal. A: Chem. 159 (2000) 257–67. [182] M.I. Siling and T.N. Laricheva, Titanium compounds as catalysts for esterification and alcoholysis, Russ. Chem. Revs. 65 (1996) 279–86. [183] M. Cozzolino, R. Tesser, M. Di Serio, M. Ledda, G. Minutillo and E. Santacesaria, Preparation, characterization and catalytic performances of highly dispersed supported TiO2/SiO2 catalysts in biodiesel production, Stud. Surf. Sci. Catal. 162 (2006) 299–306. [184] D. Swern (ed.), Bailey’s Industrial Oil and Fat Products, 4th edn, Vol. 2, John Wiley & Sons, Inc., New York, NY (1982), p. 97. [185] C.V. McNeff, L.C. McNeff, B. Yan, D.T. Nowlan, M. Rasmussen, A.E. Gyberg, B.J. Krohn, R.L. Fedie and T.R. Hoye, A continuous catalytic system for biodiesel production, Appl. Catal. A: Gen. 343 (2008) 39–48. [186] D. Siano, M. Nastasi, E. Santacesaria, M. Di Serio, R. Tesser, G. Minutillo, M. Ledda and T. Tenore (to Aser Srl), Process for producing esters from vegetable oils or animal fats using heterogeneous catalysts, PCT Int. Publ. No. WO 2006/050925 A1 (18 May 2006). [187] S. Bancquart, C. Vanhove, Y. Pouilloux and J. Barrault, Glycerol transesterification with methyl stearate over solid basic catalysts. I. Relationship between activity and basicity, Appl. Catal. A: Gen. 218 (2001) 1–11.

382

Biodiesel science and technology

[188] G.J. Suppes, Carbonate catalyzed alcoholysis of triglycerides, US Pat. Appl. 2003/0149289 A1 (7 Aug. 2003). [189] S.H. Stoldt and H. Dave (to Lubrizol Corporation), Esters derived from vegetable oils used as additives for fuels, US Pat. 5,730,029 (24 Mar. 1998). [190] R.T. Sanderson, Chemical Bonds and Bond Energy, Academic Press, New York, NY (1976). [191] I.K. Mbaraka and B.H. Shanks, Conversion of oils and fats using advanced mesoporous heterogeneous catalysts, J. Am. Oil Chem. Soc. 83 (2006) 79–91. [192] A. Derrien, G. Renard and D. Brunel, Guanidine linked to micelle-templated mesoporous silica as base catalyst for transesterification, in Mesoporous Molecular Sieves (L. Bonneviot, F. Bélard, C. Danumah, S. Giasson and S. Kaliaguine, eds), Stud. Surf. Sci. Catal. Stud. 117 (1998) 445–52. [193] G. Gelbard and F. Vielefaure-Joly, Polynitrogen strong bases as immobilized catalysts for the transesterification of vegetable oils, C.R. Acad. Sci., Ser. IIc: Chim. 3 (2000) 563–7. [194] M.L. Kantam and P. Sreekanth, Transesterification of b-keto esters catalysed by basic porous material, Catal. Lett. 77 (2001) 241–3. [195] S. Jaenicke, G.K. Chuah, X.H. Lin and X.C. Hu, Organic-inorganic hybrid catalysts for acid- and base-catalyzed reactions, Micropor. Mesopor. Mater. 35–36 (2000) 143–53. [196] J. Barrault, S. Bancquart and Y. Pouilloux, Selective glycerol transesterification over mesoporous basic catalysts, C.R. Chim. 7 (2204) 593–9. [197] M. Kim, K. Wadu-Mesthridge, A. Wang, J. Wilson, S.O. Sailey and K.Y.S. Ng, Development of anionic resin exchange catalysts for biodiesel production, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [198] M. Canakci and J. Van Gerpen, A pilot plant to produce biodiesel from high free fatty acid feedstocks, Trans. ASAE 46 (2003) 945–54. [199] R. Koster, B. van der Linden, E. Poels and A. Bliek, The mechanism of the gasphase esterification of acetic acid and ethanol over MCM-41, J. Catal. 204 (2001) 333–8. [200] J. Otera, Esterification Methods. Reactions and Applications, Wiley-VCH, Weinheim (2003). [201] S.C.M. Dos Reis, E.R. Lachter, R.S.V. Nascimento, J.A. Rodrigues and M. Garcia Reid, Transesterification of Brazilian vegetable oils with methanol over ion-exchange resins, J. Am. Oil Chem. Soc. 82 (2005) 661–5. [202] A.A. Kiss, A.C. Dimian and G. Rothenberg, Solid acid catalysts for biodiesel production – towards sustainable energy, Adv. Synth. Catal. 348 (2006) 75–81. [203] L. Jeromin, E. Peukert and G. Wollmann (to Henkel), Process for the pre-esterification of free fatty acids in fats and oils, US Pat. 4,698,186 (6 Oct. 1987). [204] L. Jeromin, E. Peukert and G. Wollmann (to Henkel), Verfahren zur Vorveresterung freier Fettsäuren in Rohfetten und/oder -ölen, Germ. Pat. DE 3,501,761 A1 (21 Jan. 1985). [205] C. Mazzocchia, G. Modica, A. Kaddouri and R. Nannicini, Fatty acid methyl esters synthesis from triglycerides over heterogeneous catalysts in the presence of microwaves, C.R. Chim. 7 (2004) 601–5. [206] J. Jitputti, B. Kitiyanan, P. Rangsunvigit, K. Bunyakiat, L. Attanatho and P. Jenvanitpanjakul, Transesterification of crude palm kernel oil and crude coconut oil by different solid catalysts, Chem. Engng. J. 116 (2006) 61–6. [207] Y. Ma, Q.L. Wang, H. Yan, X. Ji and Q. Qiu, Zeolite-catalyzed esterification. I.

Biodiesel catalysis

383

Synthesis of acetates, benzoates and phthalates, Appl. Catal. A: Gen. 139 (1996) 51–7. [208] G. Sunita, B.M. Devassy, A. Vinu, D.P. Sawant, V.V. Balasubramanian and S.B. Halligudi, Synthesis of biodiesel over zirconia-supported isopoly and heteropoly tungstate catalysts, Catal. Commun. (2008) 696–702. [209] S. Furuta, H. Matsuhashi and K. Arata, Biodiesel fuel production with solid superacid catalysis in fixed bed reactor under atmospheric pressure, Catal. Commun. 5 (2004) 721–3. [210] C.M. Garcia, S. Teixeira, L. Marciniuk and U. Schuchardt, Transesterification of soybean oil catalyzed by sulfated zirconia, Bioresour. Technol. 99 (2008) 6608–13. [211] A. Corma and H. García, Organic reactions catalyzed over solid acids, Catal. Today 38 (1997) 257–308. [212] D.E. López, J.G. Goodwin Jr., D.A. Bruce and E. Lotero, Transesterification of triacetin with methanol on solid acid and base catalysts, Appl. Catal. A: Gen. 295 (2005) 97–105. [213] D.E. López, K. Suwannakarn, D.A. Bruce and J.G. Goodwin Jr., Esterification and transesterification on tungstated zirconia: effect of calcination temperature, J. Catal. 247 (2007) 43–50. [214] K.N. Rao, A. Sridhar, A.F. Lee, S.J. Tavener, N.A. Young and K. Wilson, Zirconium phosphate supported tungsten oxide solid acid catalysts for the esterification of palmitic acid, Green Chem. 8 (2006) 790–7. [215] A.A. Kiss, F. Omota, A.C. Dimian and G. Rothenberg, The heterogeneous advantage: biodiesel by catalytic reactive distillation, Topics Catal. 40 (2006) 141–50. [216] A.H. West, D. Posarac and N. Ellis, Simulation, case studies and optimization of a biodiesel process with a solid acid catalyst, Int. J. Chem. React. Engng. 5 (2007) A37. [217] J. Ni and F.C. Meunier, Esterification of free fatty acids in sunflower oil over solid acid catalysts using batch and fixed-bed reactors, Appl. Catal. A: Gen. 333 (2007) 122–30. [218] M. Toda, A. Takagaki, M. Okamura, J.N. Kondo, S. Hayashi, K. Domen and M. Hara, Biodiesel made with sugar catalyst, Nature 438 (2005) 178. [219] A. Takagaki, M. Toda, M. Okamura, A. Kondo, S. Hayashi, K. Domen and M.Hara, Esterification of higher fatty acids by a novel strong solid acid, Catal. Today 116 (2006) 157–61. [220] M.-H. Zong, Z.-Q. Duan, W.-Y. Lou, T.J. Smith and H. Wu, Preparation of a sugar catalyst and its use for highly efficient production of biodiesel, Green Chem. 9 (2007) 434–7. [221] X. Mo, D.E. López, K. Suwannakarn, Y. Liu, E. Lotero, J.G. Goodwin Jr. and C. Liu, Activation and deactivation characteristics of sulfonated carbon catalysts, J. Catal. 254 (2008) 332–8. [222] I.K. Mbaraka, K.J. McGuire and B.H. Shanks, Acidic mesoporous silica for the catalytic conversion of fatty acids in beef tallow, I&EC Res. 45 (2006) 3022–8. [223] M.A. Jackson, I.K. Mbaraka and B.H. Shanks, Esterification of oleic acid in supercritical carbon dioxide catalyzed by functionalized mesoporous silica and an immobilized lipase, Appl. Catal. A: Gen. 310 (2006) 48–53. [224] Y. Liu, E. Lotero and J.G. Goodwin Jr., Effect of carbon chain length on esterification of carboxylic acids with methanol using acid catalysis, J. Catal. 243 (2006) 221–8.

384

Biodiesel science and technology

[225] D.E. López, J.G. Goodwin Jr. and D.A. Bruce, Transesterification of triacetin with methanol on Nafion® acid resins, J. Catal. 245 (2007) 381–91. [226] Y. Liu, E. Lotero and J.G. Goodwin Jr., A comparison of the esterification of acetic acid with methanol using heterogeneous versus homogeneous acid catalysis, J. Catal. 242 (2006) 278–86. [227] T.A. Nijhuis, A.E.W. Beers, F. Kapteijn and J.A. Moulijn, Water removal by reactive stripping for a solid-acid catalyzed esterification in a monolithic reactor, Chem. Engng. Sci. 57 (2002) 1627–32. [228] B.S. Balaji and B.M. Chanda, Simple and high yielding synthesis of b-keto esters catalysed by zeolites, Tetrahedron 54 (1998) 13237–52. [229] M. Sasidharan and R. Kumar, Transesterification over various zeolites under liquid-phase conditions, J. Mol. Catal. A: Chem. 210 (2004) 93–8. [230] B.P. Bandgar, L.S. Uppalla and V.S. Sadaverte, Envirocat EPZG and natural clay as efficient catalysts for transesterification of b-keto esters, Green Chem. 3 (2001) 39–41. [231] S.P. Chavan, P. Zubaida, S.W. Dantale, A. Keshavaraja, A.V. Ramaswamy and T. Ravindranathan, Use of solid superacid (sulphated SnO2) as efficient catalyst in facile transesterification of ketoesters, Tetrah. Lett. 37 (1996) 233–6. [232] S.P. Chavan, Y.T. Subbarao, S.W. Dantale and R. Sivappa, Transesterification of ketoesters using Amberlyst-15, Synth. Commun. 31 (2001) 289–94. [233] M.A. Harmer, W.E. Farneth and Q. Sun, High surface area Nafion resin/silica nanocomposites: a new class of solid acid catalyst, J. Am. Chem. Soc. 118 (1996) 7708–15. [234] J.T. Kloprogge, L.V. Duong and R.L. Frost, A review of the synthesis and characterisation of pillared clays and related porous materials for cracking of vegetable oils to produce biofuels, Environm. Geol. 47 (2005) 967–81. [235] H. Lepper and L. Friesenhagen (to Henkel), Verfahren zur Herstellung von Fettsäuremethylestern, Eur. Pat. EP 184,740 A (18 June 1986). [236] M.G. Kulkarni, R. Gopinath, L.C. Meher and A.K. Dalai, Solid acid catalyzed biodiesel production by simultaneous esterification and transesterification, Green Chem. 8 (2006) 1056–62. [237] F. Babou, B. Bigot, G. Coudurier, P. Sautet and J.C. Védrine, Sulfated zirconia for n-butane isomerization experimental and theoretical approaches, Stud. Surf. Sci. Catal. 90 (1994) 519–29. [238] H. Matsuhashi, H. Miyazaki, Y. Kawamura, H. Nakamura and K. Arata, Preparation of a solid superacid of sulphated tin oxide with acidity higher than that of sulphated zirconia and its applications to aldol condensation and benzoylation, Chem. Mater. 13 (2001) 3038–42. [239] G.D. Yadav and A.D. Murkute, Preparation of a novel catalyst UDCaT-5: Enhancement in activity of acid treated zirconia – effect of treatment with chlorosulfonic acid vis-à-vis sulfuric acid, J. Catal. 224 (2004) 218–23. [240] G.D. Yadav and J.J. Nair, Sulfated zirconia and its modified versions as promising catalysts for industrial processes, Micropor. Mesopor. Mater. 33 (1999) 1–48. [241] D.E. López, J.G. Goodwin Jr., D.A. Bruce and S. Furuta, Esterification and transesterification using modified-zirconia catalysts, Appl. Catal. A: Gen. 339 (2008) 76–83. [242] G. Waghoo, R.V. Jayaram and M.V. Joshi, Heterogeneous catalytic conversions with hydrous SnO2, Synth. Commun. 29 (1999) 513–20.

Biodiesel catalysis

385

[243] B.A. Nebel, M. Mittelbach and J. Auvinen, Biodiesel made with sugar catalyst – a novel green production method? Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [244] G. Rothenberg, Catalysis. Concepts and Green Applications, Wiley-VCH, Weinheim (2008), p. 171.

9

Processes for biodiesel production from unrefined oils and fats

Abstract: More economic raw materials than refined triglyceride oils for biodiesel production are waste vegetable oils and low-value fats (technical tallows), containing high free fatty acid (FFA) and water contents. This chapter describes the actions to be taken to convert such rather heterogeneous feedstocks to specification compliant biodiesel, including removal of impurities, dehydration and deacidification. Different process schemes for transformation of low- and high-FFA oils and fats into biodiesel are described. Fatty acid esterification is considered in detail as well as simultaneous esterification/transesterification procedures. In particular, the prospects of jatrodiesel, algal and tall biodiesel, and the use of vegetable oil soapstocks are outlined. Key words: (Trans)esterification of acidic feedstocks, jatrodiesel, algal biodiesel, tall biodiesel, vegetable oil soapstocks.

9.1

Introduction

To improve the economic outlook of biodiesel, feedstock selection is critical. Refined triglyceride oils have been the predominant feedstocks for the synthesis of biodiesel to date. However, such raw materials are relatively high in cost, and result in a biodiesel product that cannot compete economically with petrodiesel fuel. This has fostered investigation of use of lower-valued lipids (see Table 5.31). Commercial grade fats and oils always contain relatively important quantities of free fatty acids, water and impurities such as polypeptides and phospholipids. Crude vegetable oils and fats frequently contain more than 3 wt% free fatty acids. The acid value (AV) of good quality vegetable oils is less than 10 mg KOH/g, but amounts to 20–25 mg KOH/g for lower quality oils. Typically, FFA contents for crude virgin oils may vary from a few percent (2–5 wt%) in coconut oil (mainly as lauric acid), Jatropha curcas oil (as C18:1 and C18:2) or castor oil (as oleic acid) to as much as 10–20% in crude palm oil (mainly as palmitic acid), rice bran oil (as C18:1 and C18:2) and mahua oil (mainly as oleic acid). In fact, the acid number of natural fats and oils, and hence their FFA content, may vary within wide limits even for the same crop, e.g. for crude coconut oil (CCNO) AV = 10–20 mg KOH/g (< 10 mg KOH/g for good qualities, 20–25 KOH mg/g for inferior qualities). Palm kernel oil possesses a variable degree of acidity, 386

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usually not exceeding 15%. Prime quality cottonseed should contain no more than 1.8% FFAs, less than 12.0% moisture, and less than 1.0% foreign matters. Cottonseed having more than 12.5% FFA, over 20% moisture, and more than 10% foreign matter is classified as off quality cottonseed. Table 9.1 lists indicative FFA contents of some prospective biodiesel feedstocks. The most economic raw materials are waste vegetable oils (WVO) and low-value fats, such as recycled restaurant grease, animal fats (beef tallow; BTW), and soapstock. Used cooking oils typically did cost approximately 2–3 times less than virgin oil depending on market conditions. These materials usually suffer from a high FFA content (5–10 mg KOH/g). The acidity of WVO increases with ageing, e.g. 2.76(8)% and 4.33(13)% in waste olive oil collected in 1999 and 1998, respectively [1]; cf. the acid value of virgin olive oil of 0.5–0.8 mg KOH/g. Technical tallows have acid numbers from about 1–40 mg KOH/g or higher, corresponding to a FFA content of 0.5–20 wt%, respectively. Research on biodiesel from used frying oils, waste glyceridic oils or greases (i.e. tallow-based cooking oils) has been described [1–6]. Biodiesel produced from used cooking oil and animal fats is sometimes termed ‘green biodiesel’. The ideal biodiesel process permits the production of fatty acid esters in high yield (nearly 100%) from fatty acid glycerides of any given origin in purified or unpurified form especially with fatty acid high contents in the free state at ambient temperatures and atmospheric pressure and the lowest possible alcohol excesses with a minimum of technical and equipment expenditure and is suitable for large industrial systems as well as small and minimum scale systems. In practice, low-cost feedstocks (acidic oils with > 4 mg KOH/g) must usually undergo some form of pre-treatment before they can be used for biodiesel production. In waste oils and fats, which have been contaminated by microorganisms and have been in prolonged contact with Table 9.1 Free fatty acid content in biodiesel feedstocka Feedstock

Approximate Feedstock wt% FFA

Approximate wt% FFA

Trade return margarine Soybean oil Rapeseed oil Sunflower oil Crude palm oil Coconut oil Used cooking oils Jatropha curcas oil Karanja oil Corn oil

< 1 1 3 3.5 4.5 5 2–7 4–10 7–8 9

4.5–9 5–20 2–35 2–50b 15–60 50–60 20–60 90 >98 30–100

a

Microalgal oil Yellow grease Inedible tallow Animal fats Crude rice bran oil Acidulated soapstocks Crude tall oil Deodoriser distillate High-acid oils (ex SS) Brown grease

Indicative values only. E.g. pig fat, 1.4; low-grade chicken fat, 6; duck fat, 23.

b

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water, the triglyceride ester bonds may have been partially disrupted and short-chain carbonic acids may have been formed. Also oxidative processes may have taken place. Consequently, waste oils and fats generally constitute a very heterogeneous mixture. Prior to transesterification, impurities contained in the feedstock (such as phosphatides, free fatty acids, waxes, tocopherols, colorants, particulates) need to be removed. Particulate matter in animal fats (such as meat and bone particles) is commonly removed using a cellulose filter. Other pre-treatment steps may include water removal, steam distillation, and bleaching (see also Fig. 3.8). Steam distillation removes water and denatures and degrades residual proteins in the grease and bleaching removes spoiled proteins [7]. Bleaching and deodorisation also remove colorants and odorous substances. Dehydration of fats and oils is essential as traces of water present in the reaction mixture decrease conversions in alkaline-catalysed transesterification and are detrimental in acid catalysis. Water removal via gravity separation in a horizontal tank is normally sufficient to reduce the concentration of water in waste grease to a level of about 0.5 wt%. This drying step is essential since yellow grease from used cooking oils may contain up to 3 wt% water. Water or acid degumming removes phosphatides. Deacidification by neutralisation or distillation removes an excessive amount of free fatty acids in crude oils with FFA levels between about 0.5 and 3.5 wt% prior to alkaline transesterification (requiring ideally acid numbers below 1 mg KOH/g). Soybean oil has been deacidified using supercritical CO 2 and membrane technology [8]. Rohm & Haas Co. (Philadelphia, PA) has recently (Feb. 2009) released new purification technology for high-FFA feedstock prior to esterification. This purification resin removes unwanted impurities such as phospholipids and proteins, as well as metal ions (Na+, K+, Mg++). Ambersep™ BD19 can replace or supplement conventional degumming processes and extend the life of esterification catalysts. Pre-treatment is generally necessary to make a good quality product later and is considered almost imperative for multi-feedstock operation. Impurities are removed during pre-biodiesel processing. Multi-feedstock technology (MFT) is more involved than using mono-feedstocks and usually relies on considerable analytical work on oil profiling. Techniques using high T, p in a supercritical reaction are less concerned about the variability of feedstock. However, if a fixed-bed catalyst is employed, contaminants could foul the catalyst and should be removed before transesterification. Multi-feedstock operation emphasises the importance of analytical support and requires careful setting of process parameters. For multiple and vastly different feedstocks it is critical to analyse them as they are delivered. In MFT it is most important to have a mix in the crude tank going into the process that does not vary too much. This requires real-time testing and automation. Provided a pre-treatment is used, the FFAs are stripped, and impurities such as metals, phospholipids,

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solids and water are removed, the clean amalgam of fats, greases and oils can move into transesterification. Highly saturated feedstocks such as tallow take more time to convert to biodiesel than lower saturate canola or soybean oil. It changes the process parameters, catalyst consumption, percentage of excess methanol, and residence time. Multi-feedstock operation also affects catalyst choice. Potassium methoxide is recommended for animal fats. Good end-product fuel quality in multi-feedstock processing can be ensured only through adequate quality control measures and much testing. Figure 9.1 shows different process schemes for the transformation of lowand high FFA oils and fats into biodiesel. Biodiesel from waste and crude feedstocks is suitable for blending with biodiesel produced from refined oils.

9.2

Fatty acid esterification

Biodiesel can be produced by transesterification of triglycerides or by esterification of fatty acids. Esterification of carboxylic acids (specifically FFAs) is directly relevant to biodiesel synthesis given the increasing importance of low-cost lipid feedstocks containing high FFA concentrations. Esterification is a more facile reaction than transesterification because it allows easy elimination of a reaction product (water); this is not the case in high-temperature transesterification, where glycerol remains present and Low-FFA oils/fats

High-FFA oils/fats

Pre-treatment

Alkaline catalyst + Dry methanol

Soapstock

Pre-treatment Steam refining

Transesterification FAD

Methanol recovery Crude glycerin

FAME

Glycerin refining

Washing

Glycerol

Dry methanol + Acid catalyst

Acid esterification

Biodiesel

9.1 Transformation of low- and high-FFA oils and fats into biodiesel by (trans)esterification.

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soluble. It follows that removal of water continuously from the reaction mixture is an important feature of the esterification process in order to shift the equilibrium towards the ester side. Figure 7.6 allows comparison of the esterification rate of FFA to that of transesterification of a triglyceride. Since esterification and transesterification share a common molecular pathway, evidence about catalyst reactivity for esterification also provides evidence about transesterification and vice versa. For esterification of FFA with an alcohol both base and acid catalysts can be used. However, base catalysts can only be used at high temperatures (otherwise catalyst deactivation takes place by soap formation). Traditionally, esterification reactions are carried out under batch conditions in homogeneous liquid phase. Esterification shares the same reactivity principles as transesterification when using acid catalysts. Like transesterification, esterification rates and yields are increased by higher alcohol-to-FFA molar ratios, catalyst concentration, temperature and pressure [9–11]. In acid-catalysed esterification the key catalyst-FFA interaction is protonation of the carboxylic moiety in the FFA. In general, solid acid-catalysed esterification of alkyl acids with alcohols exhibits overall second-order behaviour, similar to the homogeneous acidcatalysed reaction. Second-order kinetics were reported for esterification of oleic acid with glycerol over sulphated iron oxide [12] and for gas phase esterification of acetic acid with ethanol over MCM-41 [13]. For acid esterification catalysts there are several options (see Tables 8.9 and 8.18). Commercially, pseudo-homogeneous esterification of fatty acids with alcohols is commonly carried out at industrial scale using liquid acid catalysts (H2SO4, pTSA, MSA, HF) under mild reaction conditions. Sulphuric and p-toluenesulphonic acid are usually active at 423–443 K, although it is possible to carry out esterifications at temperatures below 343 K. Sulphuric acid is the oldest catalyst in use but has the disadvantage of yielding relatively high amounts of by-products. Its advantage is low price; the catalyst is not recovered. Another much used catalyst, pTSA, poses considerable recycling problems; the relatively expensive, and toxic, catalyst must be disposed of as chemical waste. Vieville et al. [14] described esterification of oleic acid with methanol by p-toluenesulphonic acid (in a pseudo-homogeneous phase) and by the sulphonic acid cation-exchange resins K2411 and K1481 (in a heterogeneous phase). Requirements for solid-acid esterification catalysts are high activity and selectivity (suitable strength and number of sites), adequate textural properties (porosity and surface area), long lifetime (thermal stability at 473–523 K and increased surface hydrophobicity) and low cost. Solid-acid catalysts are widely used in esterification reactions [15, 16]. Heterogeneous acid catalysts that perform well in esterification are likely to also be good catalysts for transesterification since the mechanisms for both reactions are quite similar. The ability of solid acids to catalyse both esterification and transesterification

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reactions simultaneously, thus eliminating any pre-treatment steps, is very attractive. Solid-acid resins are widely used in esterification reactions [15]. However, thermal stability above 413 K and lack of structural integrity at high pressures severely limit the applicability of organic resins as catalysts for (trans) esterification. The activity of acidic ion-exchange resins (Amberlyst®15, Amberlyst®16, Amberlyst®35 and Dowex®HCR-W2) were compared in esterification of FFAs in greases at 323–333 K. The catalytic activity (A-15 > A-35 > A-16 > Dowex® HCR-W2) of the resins closely parallels the magnitude of their ion-exchange capacity [17]. AmberlystTM BD20 (Rohm & Haas Co.) is claimed to show the fastest solid-catalyst esterification technology, which outperforms all current solid catalysts and even conventional sulphuric acid technology in terms of speed, FFA range, as well as conversion efficiency (see Section 15.3.1, pp 732–6). The disadvantages of using mineral acid catalysts for high-FFA feeds are summarised in Table 15.10. Figure 15.15 compares mineral acid and AmberlystTM BD20 esterification processes. Strongly acidic zeolites catalyse esterification of carboxylic acids with alcohols as well as their hydrolysis. Carboxylic acids can be esterified by alcohols in a batch reactor over acid zeolites in the same way as using liquid acids as H2SO4 [18, 19]. Besides acid strength, other factors such as reactant-preferent adsorption or differences in surface polarities may play a significant role in the activity and selectivity of these catalysts. At high reaction temperatures a variety of by-products are formed. The different crystal structures, dimensionality of the channel system, framework Si/Al ratios, proton-exchange levels and surface hydrophobicity of zeolites permit tailoring catalytic properties, such as acid strength, to fit the reaction requirements [20]. Optimum acidity for esterification reactions has yet to be established. As the catalytic activity of zeolites for the esterification of fatty acids increases with higher Si/Al ratio, the reactivity is influenced by both acid site strength and surface hydrophobicity. The SiO2/Al2O3 ratio represents a trade-off between acidity and hydrophobic character: water is easily adsorbed at low SiO2/Al2O3 ratios, whereas the acidic properties are lost at higher SiO2/Al2O3 ratios. The zeolite that is more suitable for a specific esterification reaction depends on the polarity and miscibility of the acid and alcohol reagents. Mass-transfer resistance is critical when using zeolites due to their microporous nature. Microporous zeolites with relatively narrow pore size, such as H-ZSM-5, Y and Beta show poor activity in esterification on account of limited diffusion of the bulky fatty acid reactants and products into the zeolite pores [21]. Zeolite (H-ZSM-5, HY)-catalysed esterification of acetic, benzoic and phthalic acids has been reported [19]. Although zeolites are active catalysts for esterification of large carboxylic acids, they catalyse the reaction rather slowly. Consequently, large-pore zeolites are favoured in fatty acid esterification [22]. In general, zeolite catalysis of reactions

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Biodiesel science and technology

involving molecules too large to diffuse into the channels and cavities of the zeolites take place on the external surface of the zeolite crystallites. Zeolites have also been used for the production of monoglycerides (MG) from fatty acids and glycerol [22, 23]. High catalytic activity and selectivity towards MG were observed in the esterification of FFAs with glycerol in relation to an increased hydrophobic character of the catalyst surface [24]. Likewise, a more hydrophilic mesoporous silica showed the least catalyst activity in the pre-esterification with methanol of FFAs in model mixtures with SBO [25]. Mesoporous catalytic materials have been used extensively for esterification reactions [26]. Silica molecular sieves, such as MCM-41 mesoporous materials, are generally not sufficiently acidic to promote esterification reactions. Metal (Al, Ti, Sn, Zr)-doped materials exhibit more of a weak acidic character and are unsuitable for reactions requiring a strong acid catalyst. Esterification of oleic acid with glycerol over Al-MCM-41 is considerably less successful than that over zeolite Beta with similar Si/Al ratio [24]. The maximum strength of the sites that can be obtained using mesoporous aluminosilicates and zeolites in general does not allow them to be classified as superacid solids. Also organosulphonic acid-functionalised mesoporous materials have been used in the esterification of fatty acids with alcohols. Organosulphonic acidfunctionalised mesoporous silicas have higher reactivity than commercially available solid-acid esterification catalysts (such as Nafion® NR50 and Amberlyst® 15 wet) for the conversion of fatty acids in high-FFA oils (e.g. palmitic acid in SBO) to methyl esters [25]. Increasing the acidity of the organosulphonic acid group significantly improves the activity of the mesoporous catalyst for the fatty acid esterification reaction. Proper choice of this group produces a mesoporous silica with activity at least comparable to H2SO4. Again, diffusion plays an important role in these reactions. Catalyst activity increases with the support pore diameter; medium pore diameters (22–35 Å) are required to avoid diffusion controlled reaction. Catalysts with a mean pore diameter of 50 Å and benzenesulphonic groups show activities comparable to sulphuric acid. Hara et al. [27] have recently developed thermostable, water-insoluble carbon-based solid acids, consisting of small polycyclic aromatic carbon sheets with a high density of attached sulphonic acid groups (SO3H). Strength and acid site density of these polysulphonic materials were demonstrated through esterification of acetic acid at 343 K. The activity is much higher than that of conventional solid acids (e.g. Nafion, Nb2O5◊nH2O) and comparable to that of H2SO4. Carbon-based strong solid acids should therefore have the potential to replace the sulphuric acid catalyst, but require further testing and development [21]. In contrast to zeolites, sulphated zirconia (SO42–/ZrO2) and related promoted oxides can behave as strong acid to superacid solids. Solid superacids

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promote both the esterification of free fatty acids and transesterification of triglycerides (see Table 8.18). Sulphated zirconia (SO42–/ZrO2, SZ) and tungstated zirconia (WO3/ZrO2) exhibit high catalytic activities for various reactions. SZ successfully promotes esterification of acetic acid with phenetyl and cyclohexyl alcohols [28] and has been used in the preparation of 2-ethylhexyldodecanoate from lauric acid and 2-ethylhexanol [29]. Water removal is essential for reaction progress. It drives the reaction to high product yields and, if allowed in the reaction medium, formation of an aqueous phase (accompanied by phase segregation) could promote hydrolysis of the supported sulphate groups causing leaching of the active acid sites and consequently deactivation of the catalyst [30]. Rothenberg et al. [21] have considered the benefits and drawbacks of producing biodiesel through fatty acid esterification using a variety of solid-acid catalysts, such as zeolites, ion-exchange resins and mixed metal oxides. Among the latter, SO42–/ZrO2 with high thermal stability and strong acid sites was outstanding in esterification of dodecanoic (lauric) acid with 2-ethylhexanol, 1-propanol and methanol at 333–453 K (see Table 8.18). Sulphated zirconia has large pores that improve the diffusion of the fatty acid molecules and does not leach under the reaction conditions (although it does leach in water) and does not give rise to side reactions such as etherification or alcohol dehydration. Recently, SZ catalysts (such as UDCaT-5) resistant to the presence of water have been described [31]. High sulphur content ZrO2-based catalysts (from chlorosulphonic acid as a source of sulphate ions) exhibit higher catalytic activity than conventional sulphated zirconia, albeit without testing for methanolysis [31]. Although sulphated tin oxide (SO42–/SnO2, STO) is classified as one of the strongest solid acids (H0 value = 18), with an acid strength exceeding that of SZ [32], its use is more limited than that of SZ due to preparation difficulties and poor yields. In esterification of n-octanoic acid with methanol, STO has shown superior activity compared to SZ at T < 423 K, approaching a 100% ester yield already at 373 K as compared to 423 K for SZ catalysts [33]. Furuta et al. [34] reported esterification of n-octanoic acid with methanol at 448–473 K and 0.1 MPa over superacid solid catalysts, reaching over 90% conversion for tungstated zirconia-alumina. Heteropolyacids (HPAs) are characterised by a large number of strongly acidic sites. They are very active catalysts for carrying out the dehydration of alcohols and have also shown very interesting possibilities as esterification catalysts [35]. Supported heteropolyacids are considered as superacids. Heteropolyacids show high selectivity (absence of by-products resulting from reactions of the conjugate base of the acid) and higher activity (on molar basis) than conventional homogeneous Brønsted acid catalysts, thus allowing operation at lower temperatures (363–393 K). However, HPA catalyst recovery must be complete to obtain a clean, cost-effective process. Heteropolyacids

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Biodiesel science and technology

have successfully been applied in several acid-catalysed reactions, even on an industrial scale. They have been tested with carboxylic acids [16, 36–39] and anhydrides [35]. The esterification of palmitic, oleic and stearic acid with methanol was described using the HPAs tungstophosphoric acid (PW), molybdophosphoric acid (PMo) and tungstosilicic acid (SiW) immobilised on silica at 333 K [40]. PW-silica was most active. MCM-41-supported HPAs are more active than pure HPA in the gas-phase esterification of acetic acid and 1-butanol [41]. Esterification of phthalic anhydride with several alcohols has been examined using HPAs, in particular dodecatungstophosphoric acid, H3PW12O40 [35]. Hydrous zirconia supported 12-tungstophosphoric acid has been used for simultaneous esterification and transesterification of low-quality canola oil (up to 20% FFA) [42]. Finally, non-acidic alkyl titanate catalysts form very low by-products, but as their activity is much lower than that of Brønsted acids, high reaction temperatures (> 473 K) are required. Esterifications and transesterifications mediated by organotin oxides, hydroxides and alkoxides were reviewed by Mascaretti and Furlan [43]. Antunes [44] developed an esterification method to produce biodiesel from fatty acids using a niobium-based heterogeneous catalyst. Continuous acid-catalysed esterification technology using ultrasounds has been described [45] (see also Section 11.2.2). Greenline Industries, Inc. (Larkspur, CA), a biodiesel process technology provider, is developing a new process to esterify free fatty acids without using acid catalysts.

9.3

Transesterification of acidic feedstocks

Base- and acid-catalysed transesterifications of some representative acidic (i.e. FFA-containing) triglyceride feedstocks (such as unrefined oils and fats, waste edible oils) are specified in Tables 8.5 and 8.9, respectively; see also Tables 8.13, 8.15 and 8.18. The following problems exist with producing diesel fuel oil from waste edible oils: ∑

lowering of the conversion rate by reduction of the activity of alkali catalysts by moisture and free fatty acids in untreated raw materials; ∑ formation of fatty acid soaps (reaction of saponification) in the presence of moisture and NaOH as a catalyst; ∑ inferior target product quality due to the presence of odour material produced by thermal decomposition and oxidation of vegetable oil; and ∑ presence of large amounts of foreign substances or impurities such as dust, lard, solid components (leading to inferior target product quality and/or clogging of product lines).

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Conventional alkali-catalysed, atmospheric transesterification in mild reaction conditions is readily applicable to produce FAAEs from refined VOs with FFA content < 0.5 wt% (corresponding to an acid value of about 1 mg KOH/g) but is ineffective at esterifying free fatty acids and can therefore not directly be applied to feedstocks such as unrefined VOs, animal fats, recycled greases or soapstocks. When an alkali catalyst is added to acid feedstocks, the free fatty acids react with the catalyst to form soap and water, as follows:

RCOOH + NaOH Æ RCOO–Na+ + H2O

Fatty acid

Catalyst

Soap

Water

9.1

Therefore, FFA-containing feeds present significant processing problems in standard biodiesel manufacture since saponification of the free fatty acid by the homogeneous alkali catalyst used to transesterify triglycerides leads to undesired catalyst consumption or deactivation. Free fatty acids may also inhibit solid catalysts relying on highly basic sites [46]. Base catalysis of oils containing free fatty acids also leads to formation of excessive emulsions, which hinder phase separation and removal of glycerol from the reaction mixture; consequently, the reaction does not proceed to completion leading to lower yields. Furthermore, due to the solubilising action of the resulting soap of the fatty acids, a greater amount of the fats is dissolved in the glycerol layer during transesterification. This impairs the quality of fatty esters and glycerol and increases the purification costs [47]. Freedman et al. [48] compared the base-catalysed transesterification of both crude and refined vegetable oils and reported a reduction in yield of methyl esters from 93% to 98% for refined oils, to 67% to 86% for crude oils. This was attributed mostly to the presence of up to 6.66% FFAs in the crude oil, although phospholipids might also be a source of catalyst destruction. Although transesterification by acid catalysis is more time consuming than by alkali catalysis, acid-catalysed transesterification is more suitable for oils and fats that have relatively high FFA contents and more water [48, 49]. If transesterification is to proceed under mild reaction conditions (323– 343 K, 0.1 MPa), it is absolutely necessary to remove the free fatty acids contained in the feedstocks either chemically or physically. Only if the (basecatalysed) process is carried out at high T, p (e.g. 513 K and 10 MPa) and with a large excess of alcohol can the prior removal of FFAs be dispensed with, so that non-deacidified oils and fats can be used [50]. Such procedures require expensive reactors and incur high energy costs. Alternatively, the oils and fats need to be deacidified and dried, which also calls for expensive equipment. As a result, atmospheric transesterification of unrefined raw materials requires a preparative refining process involving drying, reduction in acid number and removal of impurities despite the fact that for economic reasons it

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Biodiesel science and technology

is distinctly desirable to convert a fatty glyceride raw material to alkyl esters in a one-step process. To this end various options have been considered: ∑

Alkali refining, in which alkali is used to convert FFAs into fatty acid soaps, which are then removed by washing together with other impurities. This method involves loss of material and requires an undesirable aftertreatment of the removed soap. ∑ Solvent extraction in which, utilising the solubility difference between fatty acid and TG in a solvent (e.g. methanol), FFA is transferred into the solvent phase and is extracted for removal [51]. This method requires very large amounts of solvent and does not substantially remove impurities such as polypeptides and phospholipids. Recently, the design of a deacidification process of high acidity biodiesel feedstocks with liquid-liquid methanol extraction has been described [52]. ∑ Steam reforming, which distills off the free fatty acids. The method sets relatively important equipment requirements. ∑ Excess addition of alkali beyond the catalytic amount in order to account for the free fatty acids. This method involves deterioration of the product quality and loss of materials due to the emulsifying and solubilising action of the resulting fatty acid soap. ∑ Pre-esterification or two-step alcoholysis reaction [9, 53–57]; see Section 9.3.2. This method can relatively easily be applied on an industrial scale, but polypeptides and phospholipids are not removed and remain in the fat and finally impair the quality of the glycerol layer. One factor that has blocked the widespread use of acid esterification is that the process generates a small amount of water, which promotes soap formation in the transesterification process. Water removal needs to be engineered. SRS Engineering Corp. (Murrieta, CA) has developed a commercial continuous-flow esterification system, scalable to 15% FFA or higher, sized from 500 k to 150 MMgy, which can be added front-end to an existing plant allowing multi-feedstock biodiesel operation [58]. Biodiesel producers thus get the benefit of having access to lower-cost feedstocks, higher conversions to biodiesel, without excess soap contamination. The system consists of a two-step esterification process in which water is removed by distillation at the reaction midpoint to speed up the reaction again. Different pressure and temperature variances add in the final conversion. After water removal dry, FFA-free feedstock is transesterified. The new producers’ Choice Soy Energy LLC biodiesel plant at Moberly, MO, applies this process design in combination with cavitation technology. Greenline Industries, Inc. (Larkspur, CA) has its own unique multi-feedstock process technology and has developed a high-FFA pre-processor. The FFA pre-processor is a molecular distillation system (at 515 K) particularly suited to viscous feedstocks, which scrapes the FFA from the triglycerides under vacuum.

Processes for biodiesel production from unrefined oils and fats

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Table 9.2 lists the benefits of pre-treatment for the transesterification of oils and fats. However, as pre-treatment steps are generally quite expensive, it is doubtful that purification of waste oils is economically viable (see also Section 14.5). Typical procedures for the acid (H2SO4 or sulphonic acid)-catalysed esterification of free fatty acids in admixture with triglycerides require reaction times up to 2–3 h [53, 59–61]. In Germ. Offenl. DE 19,807,519 A1 to ExRohr Center GmbH [62], waste oils and fats (with UFA > 40%) of high water contents (> 70%) were prepared for acid (H2SO4)-catalysed methanolysis to biodiesel at 338 K by stepwise removal of water. After acidification at pH = 4–5 and settling overnight, the oil-rich phase (containing 40–50% H2O) was heated at 333–363 K, subjected to a second phase separation (eventually by centrifugation) and finally heated to 393–443 K for removal of residual water and short-chain carboxylic acids. In the continuous acid-catalysed transesterification technology of PCT Int. Publ. No. WO 2003/087278 A1, assigned to Ergün and Panning (to Energea Umwelttechnologie) [45], at high temperature (353–423 K) and initial high pressure (7–15 MPa), reaction times are short (min) (see Section 11.2.2). The process is typically meant as a pre-treatment step of high-FFA (> 5 wt%) containing triglycerides (e.g. UCO) for successive base-catalysed transesterification. The acid value greatly determines the possibility and the experimental conditions of the transesterification reaction. Consequently, biodiesel synthesis by alcoholysis of commercial oils and fats can technically be carried out in various ways. A free fatty acid neutralisation can be avoided using VOs with low FFA content (ca. 0.5%) [48, 63, 64]. Direct transesterification of native oils with some 1–3.5 wt% free fatty acids may be performed in several stages, where in the first stage only sufficient catalyst is added to make the FFAs react completely to soaps while using up the catalyst, and a small excess of catalyst effects a partial transesterification with separation of glycerol. In this partial amount of glycerol, the soaps so formed will dissolve and can substantially be separated together with the glycerol. In the following reaction stage, fresh catalyst is added which can no longer be destroyed by free fatty acids [65]. If the content of FFAs in the used oil or fat amounts to over about 3 wt% (or even up to about 5 wt%) the reaction Table 9.2 Benefits of pre-treatment for the transesterification of oils and fats ∑ ∑ ∑ ∑ ∑ a

No contamination – better glycerol quality No gums causing caking in the thermal glycerine process No free fatty acids No phosphates in waste water – reduced disposal costs Reduction of the MONGa proportion in glycerine

MONG, Matter Organic Not-Glycerine.

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Biodiesel science and technology

can still be catalysed with an alkali catalyst but at the cost of considerable amounts of an additional catalyst to compensate for the catalyst lost to soap; direct alkaline transesterification is then impractical and no longer performed at reasonable cost. Acid catalysts are more robust and can handle large amounts of FFA and higher concentrations of water. Other potential benefits of acid catalysis include: ∑ the catalyst remains active in the presence of FFA; ∑ esterification of FFA and alcoholysis of TG can occur simultaneously; ∑ catalyst loadings can be reduced to levels lower than are possible with base catalysts since FFAs do not neutralise the catalyst; and ∑ lower catalyst loadings can simplify product clean-up and result in a glycerol co-product that is easier to upgrade. In the case of base-catalysed transesterification with TGs containing FFA levels above 5 wt%, the soap inhibits separation of FAME and GL and contributes to emulsion formation during the water wash. In these cases an acid catalyst can be used to esterify the free fatty acids to methyl esters. This process can be used as a pre-treatment to convert the FFAs in high acidity biodiesel feedstocks to methyl esters and thereby reduce the FFA level. Pre-treated oils in which the FFA content is lowered to <0.5 wt% can then be processed under standard basic transesterification reaction conditions (see Fig. 9.1). The pre-treatment step can be carried out using H2SO4 [66]. Therefore, while acid catalysis can handle esterification of large amounts of FFAs in fat or oil feedstocks prior to base-catalysed alcoholysis, and thus effectively solves the FFA problem, the approach adds additional reaction and clean-up steps that increase batch times, catalyst costs and waste generation. Although acid catalysts are active in the esterification of fatty acids, there is still a considerable amount of FFA present after reaction completion [67, 68]. Typically, FAME yields of 97–98 wt% are obtained for esterification with 2 wt% H2SO4 and excess alcohol in about 4 h in reflux conditions [67]. However, reaction times of 24 h are necessary to decrease the FFA concentration to about 0.4 wt%, which is suitable for conversion of the triglycerides. Using acid catalysts throughout the entire reaction process for both esterification and transesterification reduces washing steps compared with the two-step process of acid catalysis followed by base catalysis, reduces waste streams and permits handling of high amounts of FFA in the oil. In the case of still higher contents of FFAs in the oil (FFA > 10 wt%), even pre-treatment by deacidification will lead to hardly acceptable losses. Special processes are required if the feedstock contains significant amounts of free fatty acids, as in the case of waste fats and oils obtained from canteen kitchens or animal fats (5–30% FFA); soapstocks or trap grease are very low-quality raw materials (with up to 100% FFAs). An acidic catalyst is

Processes for biodiesel production from unrefined oils and fats

399

usually employed when treating fatty materials containing large amounts of FFAs. However, the yields of fatty ester are usually much less than the theoretical amount.

9.3.1 Simultaneous esterification/transesterification It is desirable to obtain high-quality FAAEs and glycerol without expensive pre-treatment or after-treatment. This need can be taken into account in various ways, comprising catalytic transesterification of liquid glycerides with a stream of gaseous alcohol at high temperature (typically 503–533 K) but at atmospheric pressure [69, 70]. It is essential to remove the glycerol rapidly from the reaction zone. The process (Hoechst AG) can be carried out with either previously refined or non-refined oils and fats and eliminates the need for the time-consuming and expensive removal of FFAs; also nondeslimed fats (e.g. unfiltered animal body fat) can be employed directly. A drawback of the procedure is the need for a high alcohol-to-oil molar ratio (83 : 1). In the case of use of alkali or heavy metal soaps as catalysts, workup may be compromised. The homogeneous acid-catalysed process can deal with high-FFA feedstocks, carrying out simultaneously both esterification and transesterification, provided that water is removed during processing. An efficient way to remove water is by conducting feedstock transformation at T > 373 K at moderate pressures and with a continuous flow of an inert gas. The in-situ separation of water by water/alcohol co-evaporation in a process with continuous alcohol feed allows the reaction to be driven to the desired high conversions at relatively low cost. Germ. Offenl. DE 19,908,978 A1 to Dimmig et al. [71] describes continuous, simultaneous transesterification of TGs (unrefined RSO, PMO and UPGO containing up to 85% FFA) and esterification of free fatty acids using alkyl-, aryl- or alkylarylsulphonic acids as catalysts at 348–358  K and atmospheric pressure. Use of homogeneous phase acid catalysts requires simultaneous catalyst and water removal. In this respect it is more advantageous to employ strongly acidic solid cation-exchange resins [57] or heteropolyacids [42]. US Patent No. 6,887,283 to Ginosar and Fox [72] has described a (batch or continuous) process for producing alkyl esters by transesterifying glycerideand/or esterifying FFA-containing substances in a single critical phase medium (Fig. 9.2). An important criterion for the critical fluid (e.g. CO2) is its ability to dissolve the reactants. The critical phase medium eliminates mass transfer limitations and thus provides increased reaction rates, decreases the loss of (solid-phase) catalyst or catalyst activity and improves the overall yield of desired products. The solubility of the reaction products in the critical fluid can be controlled by T (293–473 K) and p (1.0–27.5 MPa). When a reaction product’s solubility is low, such as for glycerol in CO2 and propane, it drops

400

Biodiesel science and technology 4 1

3

TG ROH

PS R

Critical fluid FAAE 2

PS

GL

9.2 Continuous process for producing biodiesel (FAAE) in a critical fluid medium. Key: R, continuous reactor (eventually with packed bed for solid catalysts); PS, product separator; 1, reactant input stream; 2, final product stream; 3, glycerol (GL) depleted product stream; 4, critical fluid recycle stream (after ref. [72]). Table 9.3 Benefits of single-phase transesterification in a critical fluid ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Batch or continuous operation Increased reaction rate Higher product yields over conventional processes Reduced quantity of excess reactants (approximately stoichiometric quantities) Allowance for wide range of liquid and reusable solid-phase acid or base catalysts Efficient separations (purified reaction products) No need for process neutralisation No need for washing steps

out of the critical fluid, thereby driving the reaction equilibrium towards product formation, which significantly reduces the need for excess reactants such as alcohol. After completion of the reaction, the critical fluid medium also facilitates efficient and selective separations by adjusting T, p. In transesterification of TGs, glycerol is removed first leaving the FAAEs in the critical fluid. Subsequently, T, p conditions are changed to drop out the alkyl esters and the process may be repeated. No process neutralisation of FFAs is required. Table 9.3 summarises the benefits of single-phase transesterification in a critical fluid. Esterification and esterification-transesterification processes may also be microwave enhanced [73]. Several commercial (trans)esterification technologies are now able to handle high-FFA feedstocks (see Section 15.3.1). BDI-BioDiesel International AG

Processes for biodiesel production from unrefined oils and fats

401

has developed the RepCat reusable catalyst which improves the quality of multi-feed operations (using TLW and UCO) without the need for blending with clean vegetable oils and without losing the FFA content; the quality of the by-product glycerol is also improved. Objectives of the spinel-type IFP catalyst are also transesterification of neutral oils and esterificationtransesterification of acidic oils, the latter according to: RCOOH + R¢OH Æ RCOOR¢ + H2O RCOOH Glycerolysis

+

CH 2 OH | CHOH | CH 2 OH GL

Æ

CH 2 OCOR | CHOCOR + 3 H 2 O | CH 2 OCOR

9.2

9.3

Glyceride

Although the presence of fatty acids in the oil is not detrimental a priori, for acidic oils it is preferable to precede the transesterification reaction by an esterification reaction, such as glycerolysis (Eqn 9.3), to form a glyceride from fatty acids, at atmospheric pressure and 453–493 K. Solid-acid catalysis can be used as a method for producing a fatty ester not requiring the abovementioned pre-treatment process. PCT Int. Publ. No. WO 2005/063954 to Gupta et al. [74] discloses a neutral organometallic tin compound (preferably an alkyltin oxide such as dioctyltin oxide) suitable for single-step (simultaneous) catalytic esterification of free fatty acids and transesterification of TGs from vegetable oils or animal fats at moderate T (423–573 K) and p (0.1–3.0 MPa) with slight excess of a lower alcohol (C1-C4, molar ratio ROH/VO = 3 : 1–30 : 1). Applications were described for SBO (AV = 0.5 mg KOH/g), Jatropha curcas oil (16.1 mg KOH/g), Madhuca indica oil (17.4 mg KOH/g) and oleic acid (200 mg KOH/g). Separation of fatty acids and glycerol is easy and does not require the neutralisation step. Biodiesel was obtained with acid values of 0.01–0.50 mg KOH/g. Among the non-conventional oils, RBO ranks first in terms of availability and low cost. Dark coloured crude rice bran oil (CRBO) may contain up to 60% FFA, as well as unsaponifiable matter. A study of acid (HCl)-catalysed biodiesel production from RBO has shown that: (i) the FFA content in oil has a significant effect on the transesterification reaction; (ii) the reaction rate of FFAs to FAME is faster than that of TGs; and (iii) chain length and unsaturation of FFA exert no pronounced effect on methanol esterification [75]. Optimal reaction conditions for acid-catalysed methanolysis of low-grade high FFA (60%) RBO were established. RBO shows high conversion (> 90%) at 343 K after 6 h (or 85% in 1 h) for a molar ratio MeOH/RBO = 20 : 1 with 10 wt% HCl. Acid-catalysed methanolysis of fatty acids (conversion > 99% in 20 min at 343 K) is faster than that of either pure TGs or pure TGs + 5% H2O.

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Biodiesel science and technology

Use of bifunctional (acidic and basic) spherical honeycomb catalysts for multi-feedstock vegetable oil processing has been proposed [76]. Esterificationtransesterification is promoted by acidic functionalities on the surface of the spheres and basic catalyst sites inside the honeycomb channels. Catalyst testing is at a biodiesel pilot plant scale. The recyclable catalyst technology has potential for a more economical production of cleaner biodiesel and glycerol by-product. McNeff et al. [77] have recently described a novel continuous fixed-bed microreactor (0.46 cm i.d. × 15 cm length) process (called the Mcgyan process) for ultra-fast biodiesel production with residence times from 5.4–56.9 sec by transesterification and simultaneous esterification of free fatty acids using porous micro-particulate heterogeneous metal oxide-based catalysts (ZrO2, TiO2, a-Al2O3) under high pressure (ca. 170 MPa), high temperature (573–723 K) and supercritical alcohol conditions. An 86–95% conversion to FAMEs was achieved for 24 lipid feedstocks (BTW, CO, CNO, CRO, CSO, GSO, JCO, OO, PMO, PNO, RBO, SBO, SEO, SFO, SNO, TLW, algae oil, acidulated soapstock, almond oil, black oil, lard, tall oil, walnut oil and yellow grease) with highly varying acid number (0.04–88 mg KOH/g), see also Table 9.4. The different types of metal oxide catalysts employed, namely phosphate modified, base modified, and unmodified did not produce significant differences in biodiesel production. All biodiesel made from the Mcgyan process was further processed through a continuous system designed to remove residual unreacted free fatty acids by adsorption onto a 58 Å average pore size alumina packed-bed polisher system (so-called Easy Fatty Acid Removal system). Biodiesel produced from soybean oil, and inexpensive feedstocks such as Table 9.4 Selection of conversion efficiencies of metal oxides in Mcgyan process (after ref. [77]) Catalyst(s)a

Feedstock

None SBO BMZ, PMZ, SBO   UMA, UMZ BMZ USBO BMA, UMT CRO BMT Yellow grease BMT Algae oil BMT Acidulated   soapstock a

Acid numberb FAME%c

Total run time (h)

0.35 0.35

14.1 88.1–92.6

10 8–16

15.26 0.06 15.26 0.71 88.2

92.6 89.0–91.4 92.6 90.2 90.2

12 10–11 11 20 20

BMZ = base modified zirconia; UMZ = unmodified zirconia; BMA = base modified alumina; BMT = base modified titania; PMZ = phosphate modified zirconia; UMA = unmodified alumina; UMT = unmodified titania. b mg KOH/g. c Referring to steady-state production conditions (i.e. after about 30 min).

Processes for biodiesel production from unrefined oils and fats

403

acidulated soapstock, tall oil, algae oil, and corn oil with different alcohols (MeOH, EtOH, n-PrOH, n-BuOH) all passed the ASTM D 6751-7a testing specifications. Glycerol and dimethylether are by-products of the Mcgyan process. Most (> 90%) of the theoretical amount of glycerol is dehydrated under the high T, p conditions. The catalytic system has been employed for extended use (4000 h for BMT/SBO) without any loss in conversion rate. The process system has been scaled up to pilot plant scale to achieve a production level of more than 40 kgy (reaction conditions: 633 K, molar ratio ROH/VO = 32.7, contact time 56.9 sec). Ever Cat Fuels, LLC (Isanti, MN) is proceeding to start up a 3 MMgy multi-feedstock biodiesel plant using Mcgyan process technology by March 2009. The economics of this novel process is highly cost competitive (see Section 14.5.2). Table 9.5 lists the main features of the Mcgyan biodiesel process. It should be mentioned that also lipase catalysis allows the simultaneous transesterification of triglycerides and esterification of FFAs in a one-step process, and many lipases work well in the presence of water (see Chapter 10).

9.3.2

Multistage catalytic processes

Various multistage catalytic processes have been developed to produce biodiesel from various grades of acidic vegetable oils and fats: FFA base FFA soaps FFA acid acid æÆ æ æ æææ Æ æ æss) æ Æ FAAE (neutralisation (n (neutr eutralis alisatio atio ) (excess) TG FAAE (e FAAE

9.4

FFA acid FAAE base æÆ æ æ æææ ææ Æ FAAE, GL (excess) ss) TG TG

9.5

US Patent No. 2,494,366 to Sprules and Price [56] discloses an early multistage process for high acid-value oils consisting of base- followed Table 9.5 Main characteristics of Mcgyan biodiesel process ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Allows simultaneous conversion of triglycerides and free fatty acids Inexpensive feedstocks Thermally and mechanically stable (modified) metal oxide catalysts (ZrO2, TiO2, a-Al2O3) Continuous fixed-bed process Ultra-fast High, stable conversion efficiency High T, p and supercritical alcohol conditions High quality biodiesel High value-added by-product (DME) Competitive production cost

404

Biodiesel science and technology

by acid-catalysed (trans)esterification (Eqn 9.4). In this process sufficient alkaline esterification catalyst was added to neutralise any free fatty acids present and to provide a slight excess for the transesterification reaction. Such an approach, however, causes the free fatty acids to precipitate as soap, creating an additional recovery step. After conversion of TGs to esters, a sufficient amount of a liquid acid catalyst (usually H2SO4) was added to release the FFAs from the soap formed, to neutralise the previously added alkaline catalyst and to provide a slight excess of acidic material to serve as an esterification catalyst for the free fatty acids. By this process very high yields of superior quality esters may be obtained from inferior fatty materials with acid values from 1 to 70 mg KOH/g. In treatment of fatty materials with even higher acid values soaps formed by the alkali and saturated fatty acids might impede the efficiency of the alkaline transesterification step. Typical applications reported are as follows (fatty acid source, % conversion, initial and final acid values): fish oil, 97%, 1.9, < 1.0; fish oil, 96.6%, > 29, 1.9; SBO, 96%, 1.8, < 1.0; TLW, 96.9%, 7.5, < 1.0. US Patent No. 5,399,731 to Wimmer [78] describes a one- or multistage base-catalysed transesterification of refined and unrefined vegetable oils and animal fats (with up to 20% FFA, in addition to slimy and turbid substances, and other impurities) at ambient temperature and atmospheric pressure using low alcohol excess (molar ratio ROH/VO = 3.3–5.4). Subsequent purification of FAAEs was effected by addition of ca. 0.3 to 3.0 wt% of water. The characterising features of the process are: (i) catalyst amount (0.030 mols of a basic alkali or alkaline earth metal compound per 100 g of TG plus the amount equivalent to the free fatty acids); and (ii) addition of water (or a diluted (in)organic acid) after transesterification, whereby trouble-free elimination of the catalyst residues from the ester phase and other residual impurities is made possible. The addition of small amounts of water (equivalent to the amount of basic catalyst contained in the fatty acid ester phase) is not comparable to the conventional washing operations. Instead, water is involved here in the hydration of anhydrous catalysts present in the fatty acid esters. Obviously, the glycerol phase may accumulate large amounts of soaps, particularly when using TGs with high FFA contents. To avoid the precipitation method, TGs in unrefined fats and oils are mostly esterified in a two-step process (Eqn 9.5), with pre-esterification of the FFAs with an acidic catalyst first. The combination of acid-catalysed FFA preesterification followed by base-catalysed TG transesterification is commonly called the integrated process and is currently the preferred biodiesel synthesis route for dealing with high FFA content feedstocks [9, 53, 60, 79–81]. After lowering the FFA content to about 0.5 wt% the pre-treated oil can then be processed under standard transesterification conditions with an excess of alkaline catalyst to transesterify the triglycerides and neutralise the acid esterification catalyst and any free fatty acids still contained in the mixture

Processes for biodiesel production from unrefined oils and fats

405

[53–55, 82–84]. The amount of soap formed is kept down to permissible quantities. In the case of NaOH-catalysed transesterification, some H2O is formed according to Eqn 8.3. The process steps can be described by the following reaction scheme: Acidd catalys catalysis

TG + FFA + MeOH ææææ Æ TG + FAM ME E –H O 2

Base catalysis

ææææ Æ FAME + GL + H 2 O + MeOH

9.6

An advantage of the integrated process is that it limits the use of sulphuric acid to only the initial feedstock pre-treatment where acid-catalysed esterification is more effective. The acid-catalysed pre-esterification reduces the concentration of FFAs to levels amenable for the base-catalysed transesterification process. The disadvantages of two-step methods are the additional salt waste from neutralisation, long cycle times, and a cumbersome recovery scheme of residual free fatty acids. The procedure may result in a relatively low yield of alkyl esters with a fairly high acid value. Application of a consecutive two-step H2SO4-catalysed pre-esterification process reduced FFAs to below 1 wt% in used cooking oil; see also Table 9.6 [9, 79]. The reaction mixture was allowed to settle between steps so that the water-containing alcohol phase could be removed. Water removal in between pre-esterification steps is advantageous to ensure a high FFA conversion [9] but is not necessary as high FFA conversions have also been reported for only one-step pre-esterification processes [80, 81]. Pre-treatment processes using strong acid catalysts provide good conversion yields and high-quality fuel products. These techniques have been extended to allow biodiesel production from feedstocks that are often considered to be waste. Feedstocks high in FFAs, such as waste greases obtained from used cooking oil or low-grade animal fats, can be efficiently treated with the integrated process. Several researchers have worked with feedstocks having Table 9.6 Two-step pre-esterification reaction conditions in an integrated esterification/transesterification process of low-quality tallowa,b (after ref. [79]) First esterification step Catalyst (H2SO4) concentration MeOH/VO molar ratio Reaction time Temperature Pressure a

c

5 wt% , 10 wt% 20:1 1h 333–343 K 0.14–0.40 MPa

d

Yellow grease (12% FFA) and brown grease (33% FFA). Alcohol: methanol. c Yellow grease. d Brown grease. b

Second esterification step 5 wt%c, 10 wt%d 40:1 1h 333–343 K 0.14–0.40 MPa

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Biodiesel science and technology

high to very high FFA levels [3, 9, 82, 85–87]. For example, already Keim [82] has reported conversion of palm oil containing 50.8% FFA to methyl esters using acid (H2SO4) pre-treatment followed by base (NaOCH3) catalysis, and obtained a product in 97% yield with a residual acid value equivalent to about 5% palmitic acid. The incomplete reaction is caused by water formed in the reaction mixture. US Patent No. 4,164,506 to Kawahara and Ono [53] describes a process for producing FAAEs of unrefined fats containing impurities such as polypeptides and phospholipids in addition to FFAs. In this procedure FFAs are first esterified in the presence of an acid catalyst using a lower alcohol in amounts larger than its solubility in the fats. The product mixture is separated into a lower fat layer, and an upper alcohol (water) layer, and the latter is removed. Further alcohol is added to the fat layer for washing, followed again by layer separation. Finally, conventional transesterification of the resulting refined fat and a lower alcohol is effected with an alkali catalyst. In this two-step method, polypeptides and phospholipid impurities are decomposed and the effect of solvent extraction is remarkably enhanced. Fatty acid esters and glycerol of extremely high quality are thus obtained from unrefined oils and fats. For example, CCNO (AV = 7.7 mg KOH/g) was transesterified to FAME with an acid value of 0.3 mg KOH/g. In a Henkel process [60] acidic oils and fats were transformed into fatty acid esters by (dis)continuous pre-esterification of FFAs, followed by basecatalysed transesterification of TGs, both in mild reaction conditions using a low ROH/VO molar ratio. In this process, the oil or fat (TG + FFA) is pre-esterified at 323–373 K at atmospheric pressure using a sulphonic acid catalyst (RSO3H) in the presence of an auxiliary selective solvent (typically a polyfunctional alcohol, preferably glycerol, immiscibile with TGs). In the mild reaction conditions esterification of FFA with a C1-C4 mono-alcohol is much faster than with glycerol or transesterification of TGs. After phase separation of the lower glycerol phase (containing acid catalyst and reaction water) and upper triglyceride phase (now with AV < 1 mg KOH/g), the former is dried and recycled and the latter is transesterified by standard base catalysis. The procedure was illustrated for CCNO (AV = 12–16 mg KOH/g) and PMO (AV = 14.5 mg KOH/g), but is claimed to be suitable for AV ≥ 60 mg KOH/g. In another Henkel procedure [61] the acidic vegetable oil was preesterified with excess methanol at 323–393 K and 0.1–0.5 MPa using an acidic catalyst. After separation of the alcohol phase (containing catalyst and reaction water) and extraction of the residual reaction water from the oil phase using a glycerol-methanol mixture, base-catalysed transesterification was carried out in the usual way. Many known methods for the production of biodiesel are somehow limited by incomplete esterification of all fatty acids in the starting material, lengthy

Processes for biodiesel production from unrefined oils and fats

407

purification methods such as water washing, relatively long reaction times, contamination and separation difficulties associated with co-production of glycerol, and saponification of the starting material under certain reaction conditions. For example, acidic pre-esterification requires a relatively difficult but careful catalyst separation and water removal effected by washing with methanol. As mentioned before, in order to favour separation of the catalyst- and water-containing wash-methanol, addition of a non-solvent (usually glycerol) to the oil already during the pre-esterification stage is useful practice [60]. However, this procedure leads to losses of free fatty acid esters. On the other hand, according to PCT Int. Publ. No. WO 2002/28811 A1 to Koncar and Mittelbach (to BDI) [88], an enhanced yield of fatty acid alkyl esters (FAAE) is obtained by separating the fatty acids, fatty acid salts and/or other fatty acid compounds contained in the glycerol phase, resulting from base-catalysed transesterification of unrefined and recycled vegetable oils (typically CPO, RSO) or animal fats (>10 wt% FFA), by neutralisation, and subjecting the fatty acid phase to acid-catalysed post-esterification. The multistep processing mode is shown in Fig. 9.3. PCT Int. Publ. No. WO 2004/048311 A1 to Muskett and Anderson (to Biodiesel Australia) [89] claims low or no glycerol production by transesterification of high fatty acid content lipids, such as grease trap wastes, tallows or animal fats. The procedure comprises a first acid-catalysed (5 wt%) alkyl esterification (at pH = 1–2) in an alcoholic solution (ROH/ FFA = 10–25), followed by a base-catalysed (10 wt%) transesterification of glycerides contained in the mixture (at pH = 12) and a second acid-catalysed (20 wt%) esterification of residual saponified by-products from the previous treatment steps: pH = 1–2

pH = 12

TG, FFA æ æææ Æ TG, FAAE, F FFA FF FA F Aæ æææ Æ acid catalysis base catalysis ba pH = 2

FAAE, FA, soaps, GL æ æææ Æ FA AAE AE, GL acid catalysis

9.7

The process is not sensitive to or damaged by residual water contaminating the starting lipid. The alkyl esters produced by the method remain uncontaminated by glycerol by-products from the acid-catalysed esterification and base-catalysed transesterification reactions. An exception was found

TG, FFA

Transesterification

FAAE

GL

Base catalyst

GL, FAAE, FFA, soaps

Neutralisation FFA, FAAE

Esterification Acid catalyst

FAAE

9.3 Method for producing fatty acid alkyl esters from mixtures of triglycerides and fatty acids (after ref. [88]).

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Biodiesel science and technology

in the treatment of virgin vegetable oil where some 8% of good quality glycerol was readily separated. However, surprisingly no noticeable glycerol production occurred when treating other lipids such as PMO, CNO, TLW or grease trap waste. Better than 91% conversion of waste trap grease to methyl esters was reported. Biodiesel Plants [90] has recently disclosed a continuous two-step process for biodiesel production with extractive pre-washing of the raw material (typically containing 2–4 wt% FFA and < 0.8 wt% H2O) by the crude glycerol/ methanol phase for 15 min at 308 K. The overall process is as follows: glycerol glycerol

base

TG, FFA, H 2 O æ ææ Æ TG, FAAE æ ææ Æ FAAE, TG methanol catalysis catalysis

9.8

As during glycerol/methanol washing the alcohol reacts with the free fatty acids (chemical recycling of the alcohol) the MeOH/VO molar ratio for basecatalysed transesterification is reduced. The procedure presents numerous advantages: ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

the glycerol phase extracts water and other impurities; low-quality feedstocks may be converted; free fatty acids are transformed into methyl esters; the purified feedstock (0.1–0.5 wt% FFA, 0.1 wt% H2O) may be basecatalysed at atmospheric pressure and 318 K (in twice 14–20 min); the methanol content of the glycerol phase decreases from about 8–12 wt% to 1–2 wt% with simultaneous decrease in viscosity of the raw material (from 60–65 mPa.s to 45–50 mPa.s); reduction in alcohol/VO molar ratio; no need for thermal recovery of alcohol from the glycerol phase; reduction in volume of the glycerol phase; waste reduction (water-free and waste water-free procedure); and simplified plant outlay permitting economic performance for decentralised small-sized (< 4 t/yr) plants.

Glycerolysis pre-treatment of high-FFA feedstocks is also used in Nova technology [91] (see below). Acid catalysts have included homogeneous catalysts (e.g. H2SO4 [65, 66], KHSO4, pTSA [65], methane sulphonic acid) and heterogeneous catalysts (e.g. CaCO3 [92], cation-exchange resins [54], mesoporous molecular sieves or acidic zeolites). Vegetable oils with varying amounts of free fatty acids (up to 100 wt%) can be converted to methyl, ethyl or isopropyl esters in up to 98% yield in a continuous process by combining esterification (over a sulphonated ion-exchange catalyst at 338 K with ROH/VO = 4–10), resulting in a low-FFA (0.25 wt%) oil, and transesterification (using NaOH, ROH/VO = 6 at 333 K and 0.1–0.5 MPa) [93]. The MPOB/Petronas patented methyl esters process, which requires water removal prior to transesterification, is used for various palm oil grades

Processes for biodiesel production from unrefined oils and fats

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(CPO, CPOs, CPKO, RBDPO, RBDPOo and neutralised palm oil). Crude glycerol in 80% purity is obtained as a by-product. US Patent Appl. No. 2004/0102640 to Brunner et al. [65] has disclosed an industrial procedure for acidic pre-esterification (H2SO4 or pTSA) of unrefined oils and fats containing free fatty acids (e.g. soapstocks, crude HOSNO with acid numbers of 3 up to 40 mg KOH/g), followed by washing and two-stage alkaline catalysed methanolysis. Removal of an acid catalyst is necessary before performing the next transesterification of the fatty acid glyceride. When an acid catalyst remains, it is neutralised and consequently the amount of alkali metal catalyst increases corresponding to the neutralisation amount. Pre-esterification of the FFA content of oils with homogeneous phase catalysts requires a relatively complicated separation of the catalyst and removal of water to prepare the product for subsequent alkali-catalysed transesterification. It is therefore more desirable to perform the esterification pre-treatment step with a heterogeneous acidic catalyst (usually in amounts varying from about 1% to 25% depending on the FFA contents), e.g. solid cation-exchange resins [57]. Heterogeneously catalysed pre-esterification benefits from comparatively mild reaction T, p conditions and avoids the difficulties involved in the removal of undesirable acidic catalyst residues, which dissolve in the reaction mixture [54]. The relatively low FFA contents in crude palm oil (3.25% as palmitic acid) necessitate deacidification or solid acid-catalysed pre-esterification [93]. The esterification process is actually capable of processing CPO up to 30% FFA. US Patent No. 4,698,186 to Jeromin et al. (to Henkel) [54] describes lowering of the FFA content of unrefined fats and oils to an acid value below about 1 mg KOH/g by strongly acidic sulphonated mesoporous (cat) ion-exchange resins (commercial products Amberlite®, Permutit®, Dowex®, Lewatit®) used in fixed or fluidised beds as solid esterification catalysts in mild reaction conditions (ROH/VO molar ratio 20 : 1 to 25 : 1, atmospheric to low pressure, up to 0.5 MPa). Using Lewatit®, crude coconut oil (acid number = 10 mg KOH/g) was transformed into refined anhydrous CNO (acid number = 0.55 mg KOH/g, water content = 0.08 wt%). It has also been reported that organosulphonic acid-functionalised mesoporous silicas for the pre-treatment esterification reaction of high FFA oils have higher reactivity than commercially available solid-acid esterification catalysts (e.g. Nafion NR50, Amberlyst-15 wet) for the conversion of free fatty acids (such as palmitic acid in SBO) to methyl esters [25]. In pre-treatment of vegetable oils using strong acidic ion-exchange resins, more than 90% FFA was removed from cooking soybean oil and rapeseed oil [94]. In AmberlystTM BD20 esterification/transesterification technology (Rohm & Haas) for the generation of biodiesel from a wide range of low-cost, high FFA (including UCO, TLW, fatty acid distillate and recovered soaps)

410

Biodiesel science and technology

esterification of FFAs in mild reaction conditions (T < 373 K, p < 0.7 MPa, MeOH/VO < 25 : 1) precedes transesterification [95]. The technology converts feedstock with any FFA content to achieve < 0.1% FFA (see also Section 15.3.1, pp. 736–6.) In order to remove water formed during esterification, which adversely affects subsequent transesterification of TGs in the oil phase, the reaction mixture separated from the solid-acid catalyst should be dried (see Section 9.3). The anhydrous TGs recovered from the heterogeneous acidic pre-esterification can then be subjected to atmospheric alkali-catalysed transesterification at the alcohol boiling reaction temperature. The catalytic activity of Zn/I2 is not significantly affected by water and FFAs and the system may be a promising alternative catalyst for biodiesel production when the feedstock does not meet the requirements for base-catalysed processes [96]. Most comtemporary commercial processes do not handle feedstocks containing more than 15 wt% FFA. In order to save costs, producers would prefer to use feedstocks having up to 100 wt% FFA. US Patent Appl. No. 2007/0277432 A1 to Jackam et al. (to Nova Biosource Technologies, LLC) [91] claims a novel process for production of purified biodiesel and glycerol from glycerides. The process is able to handle low-value, high FFA feedstocks such as stripped FFAs, DDG corn oil, rendered yellow grease (20% FFA, 2% MIU), bleachable inedible tallow (4% FFA, 0.5% MIU), rendered trap grease (68% FFA, 5% MIU), and rendered brown grease (37% FFA, 5% MIU). The technology – without pre-treatment – allows seamless transition between feedstocks of variable FFA contents. In this unique, continuous process, fish oil, corn oil, poultry fat, tallow, yellow and brown grease can all be used without blending with soybean oil. Although the technology is not intended to process virgin palm oil, cheap secondary forms of palm oil offal, which are not used as a food source, may also be considered. In the process the filtered feedstock is fed to a first continuous stirred tank glycerolysis reactor at 483 K and the pressure is reduced to 0.014 MPa. Water vapour produced by the reaction is removed from the reactor headspace. A conversion of fatty acids to glycerides of over 85% is achieved; the fatty acid concentration exiting from a second reactor is reduced to 0.5 wt%. The product from the glycerolysis reactors (each with residence times of 2.5 to 3 h) is then subjected to KOH-catalysed transesterification in two CSTRs in series at 323 K, each with a 2 h residence time. Product work-up consists in separating a first biodiesel stream from the fatty acid alkyl ester streams by a first distillation (preferably reactive distillation) or non-evaporative separation, and subjecting at least a portion of the first biodiesel stream to a second distillation or non-evaporative separation to render a purified second biodiesel stream and a by-product fuel stream. Glycerol is obtained at a purity level of 95–99.7%, with non-detectable levels of alcohol and less than 0.5 wt% salts. The process minimises waste streams during normal operations

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and uses lower pressures than other commercial biodiesel processes. No separate acid esterification is needed. Breakthrough technology comes at a cost. Investment in a Nova process technology facility is higher (i.e. at least US$1.25/gal) than for a conventional biodiesel plant [97]. Nova now operates three biodiesel refineries with biodiesel production capacity of between 180 and 220 MMgy using its proprietary multi-feedstock process technology and for the next three years was expected to build up to seven facilities with production capacities ranging from 20 to 100 MMgy. Instead, Nova Biosource Fuels Inc. recently filed for Chapter 11 bankruptcy. Using Nova’s process technology the Sanimax Energy Biodiesel facility (De Forest, WI; 20 MMgy) operates with a variety of 18 different feedstocks (cooking oils and animal by-products) with FFA levels ranging from 2–7 wt%, some of which are 100% animal fat. Future test runs will include feedstocks with FFA levels up to 20 wt%. Transesterification of acid oils is usually carried out in the presence of absolute alcohol (methanol). Without particular precautions, with absolute EtOH and acid oils (presence of fatty acids) or conversely with a neutral oil and aqueous alcohol, transesterification by acid catalysis results in only a partial conversion. US Patent No. 4,695,411 to Stern et al. [84] has described a multi-step transesterification of (highly) acid oils such as cotton oil, raw palm oil and copra with aqueous EtOH (7–30 wt% H2O) consisting of an initial transesterification with partial conversion (85–90%) at 393–403 K followed by removal of the produced glycerol phase, reduction of acidity to about 2% by additional esterification, and finally transesterification in the presence of a base catalyst. Also various single-phase esterification/transesterification processes have been described, which aim at accelerating the reaction [72, 98]. In a singlephase two-step (batch or continuous) process for FAME production from mixtures of triglycerides and fatty acids with low water contents (< 1 wt%), using a co-solvent with a molar ratio alcohol/(TG + FFA) = 15–35, at first a homogeneous acid catalyst (H2SO4, HCl or CF3COOH) was added for esterification of the fatty acids; after 30–60 min the solution was neutralised with Na2CO3, water formed was removed and a base catalyst was added for rapid transesterification (7 min at 333 K) [98]. Figure 7.2 shows one-phase methanolysis of SBO with a co-solvent (THF). Feedstocks converted with high ester yields (> 99%) varied from refined SBO to a cafetaria waste product (14 wt% FFA), SBO/PA (50:50 w/w) and grease trap waste (97% FFA). Indian non-vegetable oils from tree-borne oil seeds usually contain substantial amounts of free fatty acids, typically Jatropha curcas, 3.7–10 wt%; mahua, 15–19 wt%; karanja, 12 wt%; neem, 18 wt%. Similarly, rice bran oil often contains some 15 wt% FFA. Consequently, these raw materials cannot be processed by conventional base catalysis. In US Patent Appl. No. 2006/094890 Sharma et al. [86] disclose a batchwise or continuous procedure

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Biodiesel science and technology

for biodiesel production in which the FFA-rich feedstock is mixed with an alcohol and acidic catalyst and refluxed for 1 h through a water adsorbent column for effective esterification of free fatty acid to fatty acid ester; subsequently, alcohol and a basic catalyst are added to the resultant mixture to transesterify the triglycerides. Therefore ROH

–H O

ROH

2 TG, FFA æ ææ æ Æ ææ æ æ Æ TG, FAAE æ ææ æ Æ FAAE, TG acid catalys catalystt drying drying base catalys ba catalystt

9.9

The second step, which is started only when the intermediate reaction mixture is free from fatty acids, also neutralises traces of the acid catalyst, yielding water soluble salt, which is washed out during final work-up procedures. Instead of water adsorbents (e.g. zeolites, silica gels, acidic clays or molecular sieves) water scavengers (e.g. 2,2-dimethoxypropane or PCl3) may be used in situ in the reaction mixture. Trapping of the water by-product facilitates the speedier conversion to the alkyl esters of FFAs in the non-edible vegetable oil. Also Ghadge and Raheman [85] reduced the 19% FFA content of crude mahua oil to an acid value below 2 mg KOH/g using a two-step treatment; transesterification reaction was completed with an alkaline catalyst to produce biodiesel. In an improved procedure, crude mahua oil (17 wt% FFA) was first converted in acid (H2SO4)-catalysed esterification with methanol at 333 K in 1.3 h; after settling (1 h) and removal of the methanol-water fraction, the product (containing < 1 wt% FFA) was used for base (KOH)-catalysed transesterification at 333 K for 0.5 h yielding mahua biodiesel in 98% yield and with properties conforming to both US and European standards [99].

9.4

Jatrodiesel

Jatropha curcas oil (hell oil or oil infernale) is chemically a good choice as the starting oil for sustainable production of biodiesel [100–102], but the crop needs domestication [103]. In fact, the seed oil of Jatropha was already used as a diesel substitute during World War II. Later, its blends with diesel fuel were tested [104]. Daimler-Chrysler studies indicated that jatropha oil is even better suited for biodiesel than rapeseed oil. The main characteristics of crude jatropha oil are as follows: AV, 19 mg KOH/g; SV, 188–196 mg KOH/g; IV, 93–107 g I2/hg; HV, 4–20 mg KOH/g; SFA, 22%; MUFA, 41%; and PUFA, 37%. Good quality crude jatropha oil has a rather low phosphatide content (< 0.25%) and a low free fatty acid content (2.5–5.5%). Pre-treatment of crude jatropha oil prior to alkali-catalysed transesterification may consist of an acid degumming process or silica treatment in combination with physical deacidification or stripping (to acid esterification) [105]. Jatrodiesel or curcas oil methyl ester (COME) is being produced on a small scale in India [86, 106] and P.R. China [107], has been evaluated in Nicaragua [108] and has been engine proven. Companhia Produtora de

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413

Biodiesel do Tocantins (Brazil) is operating a 40 kt/yr jatropha-based BDT plant. The facility has local feedstock agreements for 48 kha of jatropha plantations. A pilot plant in the Mexican State of Michoacán produces 9 kt/yr jatropha biodiesel [109]. Gold Star Biofuels is installing small modular biodiesel production units (8 MMgy) in Chile that will use locally cultivated jatropha as feedstock. Pure Biofuels Corp. (Port Callao, Peru) will utilise jatropha and algae as primary feedstocks for its 52.2 MMgy plant. Goldstar Farms Ltd. plans to start jatrodiesel production in Nkawkaw (Ghana) in 2009. At the same time, jatropha oil from micro-financed Indian operations will be processed by Mission NewEnergy in Kuantan (Malaysia). Jatropha biodiesel is characterised by CN 51 (ISO 5165) and a flash point of 464 K. The product has a CFPP value of 273 K to 270 K, or slightly worse cold-flow properties compared to RME or SME, but still a far better cold stability than biodiesel obtained from more saturated feedstocks such as palm oil or tallow [110]. Jatropha biodiesel is being explored by the universities of York (UK) and Sichuan (Chongqing, P.R. China). The biodiesel start-up D1 Oils PLC (London) has created a joint venture for the production of jatrodiesel in Saudi Arabia. BP is investing US$9.4 M in India to demonstrate the feasibility of producing jatrodiesel on an industrial scale. Naturol BioEnergy Ltd (Hyderabad) envisages a fully export-oriented 100 kt/yr biodiesel production unit at the oleochemical complex of Kakinada (Andhra Pradesh) in a joint venture with Fe Clean Energy, Inc. (USA) and Energea GmbH (Austria), initially using imported vegetable oils, subsequently domestically sourced jatropha and pongamia oil cultivated on 120 000 acres of dry wasteland across Andhra Pradesh [111]. The Indian government has mandated a price of 26.5 rupees per litre (US$ 2.32/gal) for jatropha biodiesel. Allegro Biodiesel Corp. and Global Clean Energy Holdings, Inc. (both Los Angeles, CA) have a testing and processing agreement for the production of biodiesel from jatropha oil. Allegro is processing crude jatropha oil at its 15 MMgy production facility in Pollock, CA (originally laid out for TLW/soy biodiesel), in an effort to reduce production costs. Blending with soy oil or soy biodiesel is foreseen. It is expected that jatropha oil will also blend well with other feedstocks to produce a high-grade biodiesel. While jatropha holds a great deal of potential as a biodiesel feedstock (but not before 2014), it is also important to acknowledge that many hurdles must be overcome before the crop can become economically viable in many parts of the world (see Section 5.9.1). For example, markets for post-crush jatropha meal are rather limited because of toxicity. However, D1 Oils PLC and others [111a] have recently devised ways to detoxify jatropha meal. USFuelTech, LLC (Aiken, SC) offers biomass-to-energy production units that can gasify crushed jatropha cake left over from biodiesel production. The gas can be converted into electricity or heat for rural Chilean villages (see also Fig. 4.1).

414

9.5

Biodiesel science and technology

Algal biodiesel

Raw algae can be processed to make biocrude, and refined into gasoline, diesel, jet fuel and chemical feedstocks for plastics and drugs. Alternatively, strains of algae that produce more carbohydrates and less oil can be processed and fermented to make ethanol, with leftover protein used for animal feed. Although the theoretical potential of algae is clear, the science of algae-todiesel conversion is in its infancy. Use of eukaryotic algae and prokaryotic cyanobacteria for biofuel production is considered third-generation technology. Microalgal biodiesel is technically feasible. Microalgae are dried to obtain microalgae powder, extracted and the oil transesterified. Production of biodiesel from microalgae uses the same transesterification process as used commercially for vegetable oils. As algae oil is low in phosphorus, degumming is not needed. Table 9.7 lists the main characteristics of algal biodiesel technology. Using microalgae to produce biodiesel will not compromise production of food, fodder and other products derived from crops. However, biodiesel is the lowest value product of algae. Table 9.8 compares biodiesel from algae and oilseed crops. The biochemical composition of algal strain is a key factor for oil production. Fairly little is known about algal oil characteristics (and variability) in Table 9.7 Main characteristics of algal biodiesel technology Advantages: ∑ Substantially higher algal biomass and biodiesel production than from oilseed crops ∑ Ability to grow microalgae in saline water ∑ Favourable resource assessment (climate, land, water, CO2); no resource restrictions ∑ Algae technology complementary to agricultural biomass technology ∑ No interference with production of food, fodder and other cropderived products ∑ Synergy of microalgae biodiesel production, coal combustion and wastewater treatment ∑ Potential supply of many quads of fuel by algal biodiesel ∑ Carbon neutral ∑ Substantially higher energy balance than vegetable oil biodiesel Disadvantages: ∑ Emerging technology ∑ Low efficiency of CO2 sequestration ∑ Control of the specific strain ∑ Need for low-temperature tolerant algae ∑ No one single algal species meeting all technological needs ∑ High PUFA concentration (negative effect on oxidative stability) ∑ Economics of commercial algal biodiesel versus petrodiesel still unsettled ∑ No commercial volumes of algae oil feedstock yet available

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Table 9.8 Biodiesel from algae and oilseed crops Parameter

Biodiesel/algae

Biodiesel/oilseed crops

Technology Production site Production period Oil content Land use Water use Harvesting Cost performance Development   potential

Cell bioengineering Pilot plant 5–7 d for batch fermentation > 40–50% in whole cells Very smalla Low to moderate if controlled Continuous US$2.4/L microalgal oil Unlimited

Traditional agriculture Farm Several months to years < 20% in seeds or fruits Very largeb High (evapotranspiration) Seasonal (1 or 2 crops/year) US$0.6–0.8/L plant oil Limited

a

0.010–0.013 ha (projected area of bioreactor in pilot plant) for producing 1000 L oil. b 2.24 ha for producing 1000 L soybean oil.

relation to the needs for algal biodiesel quality. Not all algal oils are equally satisfactory for making biodiesel, but suitable oils occur commonly. The chemical profile of lipids from selected species of microalgae varies widely (not unexpectedly) with SFA 4.1–50.2% (C16:0 being the major saturated fatty acid), MUFA 3.4–21.4%, and PUFA 16.8–71.9% [112]; see also Table 5.20. The oil quality depends on the algae species used and may range from soy oil quality to oils containing high FFA. Unlike most vegetable oils, microalgal oils are generally quite rich in polyunsaturated (w3 and w6) fatty acids with D ≥ 4 [113], but less so than cyanobacteria. Eicosapentaenoic acid (EPA, C20:5n-3; D = 5) and docosahexaenoic acid (DHA, C22:6n-3; D = 6) occur commonly in oleaginous microorganisms. For example, the fatty acid composition of the Arthrospira (Arthrospira platensis Nordst.) algal oil was reported as follows: C14 : 0, 12.0%; C16 : 0, 19.4%; C16 : 1, 10.2%; C18 : 0, 1.6%; C18 : 1, 3.4%; C18 : 2, 1.0%; C18 : 3, 7.5%; C18 : 4, 0.9%; C20 : 5, 39.0%; C22 : 6, 0.4%) with SN = 195.3 mg KOH/g, IV = 202.7 g I2/hg and CN = 28.6 (calculated values) [114]. Disagreement with other reported fatty acid profiles for the same filamentous, spiral-shaped, multicellular cyanobacterium [115, 116] has been attributed to different growing conditions, light, oxygen and environmental conditions. Algal oil could well turn out to be a more suitable feedstock for HVO renewable diesel than for biodiesel. Tables 9.9 and 9.10 show specifications of a biodiesel from an algae oil [117]. Acceptable biodiesel must meet various criteria relating in particular to the extent of total unsaturation of the oil. In the particular case values for ester content, linolenic acid methyl ester, copper corrosion, MG, TG and TG, free and total glycerol in biodiesel made from the crude algae oil are all within specification. The iodine value is the same as for the algae oil that was used as a feedstock, as expected. Standards EN 14214 and EN 14213 require the iodine value of biodiesel not to exceed 120 and 130 g I 2/hg

416

Biodiesel science and technology Table 9.9 Specification of an algal biodiesel (after ref. [117]) Fuel property

Value

Reference

Ester content (wt%) C18:3 methyl ester (wt%) Copper strip corrosion (3 h, 323 K) Oxidation stability (383 K) (h) Iodine value (g/hg) Monoglycerides (wt%) Diglycerides (wt%) Triglycerides (wt%) Free glycerol (wt%) Total glycerol (wt%)

98.3 7.1 Class 1 < 1.0 123 0.61 0.12 0.07 < 0.01 0.18

EN EN EN EN EN EN EN EN EN EN

14103 14103 ISO 2160 14112 14111 14105 14105 14105 14105 14105

Table 9.10 Comparison of biodiesel from algae with diesel fuel (after ref. [119]) Fuel property –1

Density (kg L ) Viscosity (Pa ◊ s, 313 K) Flash point (K) Solidifying point (K) Cold filter plugging point Acid value (mg KOH/g) Heating value (MJ kg–1)

Algal biodiesel

Diesel fuel

0.864 5.20E-04 388 261 262 0.374 41

0.838 1.9–4.1E-04 348 223–283 270 (266.3 max) 0.5 max 40–45

biodiesel, respectively. With IV being slightly higher than EN specifications, the reported algal biodiesel needs to be blended with a small amount of a feedstock with lower IV value. Furthermore, both the European biodiesel standards limit the contents of FAME with four or more double bonds (D ≥ 4) to a maximum of 1 mol%. Oxidation stability is low, as usual for an oil that is rich in omega-3 and omega-6 fatty acids. The high degree of unsaturation determines high susceptibility to oxidation during storage of the corresponding methyl esters (see Table 14.15). Consequently, commercially available additives may be needed to improve the oxidative stability of algal biodiesel to meet the standard quality specifications. In view of the composition of many microalgal oils, in all likelihood most of them do not comply with the European biodiesel standards for vehicle use. This problem can eventually be overcome by reducing the extent of unsaturation of microalgal oils by (partial) catalytic hydrogenation (see Section 15.3.2). Most research is focused on extracting oil from green algae for biodiesel. High-quality biodiesel production from the green algae Chlorella protothecoides through acidic (H2SO4) or lipase-catalysed transesterification technology has been reported [118]. Using cornstarch hydrolysate instead of glucose as the organic carbon source, heterotrophic growth of C. protothecoides resulted in a high lipid content up to 55.2% of dry cell weight [119]. The

Processes for biodiesel production from unrefined oils and fats

417

microalgal oil (mean MW = 933, mainly composed of C18 : 1 and C18 : 2) was efficiently extracted from the heterotrophic cells using n-hexane [120]. Because of the high acid value of the microalgal oil (8.97 mg KOH/g) basecatalysed transesterification was not possible. Acid-catalysed transformation into biodiesel required 4 h at 303 K with a high molar ratio MeOH/oil = 56 : 1 and a staggering 100% catalyst quantity (based on oil weight). The properties of algal biodiesel complied with ASTM D 6751 with a low CFPP of 262 K (Table 9.10). Recently, commercial-scale cultivation of the heterotrophic microalga C. protothecoides in a 11 000 L bioreactor, combined with enzymatic transesterification by immobilised lipase from Candida sp. 99–125, was shown to lead to ASTM D 6751 specification biodiesel [121]. The process is characterised by high crude lipid content (43% of cell dry weight). Batchwise transesterification in optimised reaction conditions reached 98.15% conversion in 12 h with biodiesel production rate of 6.24 g/L; main FAME profile: C16 : 0, 10.1%; C18 : 0, 2.85%; C18 : 1, 65.75%; C18 : 2, 18.33%; C20 : 0, 0.59%; C20 : 1, 0.67%. For further reduction of fermentation cost some critical steps in the cultivation need to be improved. Heterotrophic fermentation of algal cells combined with photosynthesis using flue gas is a promising approach for microbial diesel production and commercialisation. Biodiesel from heterotrophic microalgal oil could eventually be a competitive alternative to conventional diesel fuel. Locally derived strains of whole-cell, immobilised moulds were also used for biocatalysis of marine algal oil into biodiesel [122]. BioCentric Energy Algae, LLC (USA) has implemented a new proprietary technological process that efficiently transforms two unique species of algae into biofuels. Large-scale industrial algae cultivation is best embedded in a ‘whole crop’ biorefinery context, which separates the various biomass fractions into high-value components (for food supplements and ingredients for cosmetics), proteins (for food, feed) and lipids (as raw material for fuel and the chemical industry), with oil being the least profitable component. Combined extractiontransesterification is effective in quantitatively recovering the fatty acid esters from dry microalgal biomass. This technology has been applied in a low expense simultaneous extraction-transesterification process (followed by fractionation on a silver-silica gel chromatography column) for recovering esterified eicosapentaenoic acid (EPA) from microalgae [113]. The market price of EPA ethyl ester (95% pure) – for pharmaceutical use – is of the order of US$650/kg (2000). Co-production of algal biodiesel and value-added polyunsaturated fatty acids (like EPA) is only economically viable for strains with high oil content and high quantities of easily extractable high-value products. Credits for CO2 sequestration enhance the potential economic value of algae. Figure 9.4 shows an integrated algae-based industrial processing scheme, as developed by BioCentric Energy Algae, LLC. Although there is considerable interest in algae biodiesel, the technology is

418 Electricity

Biodiesel science and technology Syngas, CO2

Gasification (pyrolysis)

Trash (MSW)

CO2 capturing

Algae

Extraction

Algae Algae + residue oil

Transesterification

Biodiesel

9.4 Integrated algae-based industrial processing.

still too expensive and out of reach for large-volume commercial operation. The price of crude algae oil is very high (up to US$3.85/gal, April 2008). Algae production cost data vary by several orders, depending on climate, species and growing systems [112]. Algae production is labour intensive. Theoretical scenarios and actual experience differ considerably. The perceived high cost of algae production remains the major obstacle to algal biodiesel. Cost analyses indicate the need for highly productive organisms capable of near-theoretical levels of conversion of sunlight to biomass. In 1998 projected costs for algal biodiesel (open ponds) were two times higher than petroleum diesel fuel costs [123]. More recently, a reasonable target price for microalgal oil was given as US$0.48/L (2007) for algal diesel to be cost competitive with petrodiesel [124]. The economics of producing microalgal biodiesel needs considerable improvement to make it competitive with petrodiesel. Chisti [124] has discussed approaches for making microalgal biodiesel economically competitive with petrodiesel. Expectations have been expressed that algae production for biodiesel is becoming economically attractive at an oil price of US$100–120/barrel. However, some critics (www.biodieselfever.com) quote an oil price of US$800/barrel. A recent comparison (Jan. 2009) of algae production technologies indicates the following per-litre algal oil production and capital costs: raceway, US$14.44; photobioreactors (PBRs), US$24.60; fermenters, US$2.58 [112, 125]. Algae R&D for biodiesel should therefore concentrate on raceways (for warm climates) and fermenter technology. There are more serious challenges in making PBRs cost-effective for lowvalue products such as biofuels. Producing low-cost microalgal biodiesel may take advantage of inexpensive reactors and advances in algal biology through genetic and metabolic engineering. Use of the biorefinery concept (Figs 5.8 and 5.9) and further advances in photobioreactor engineering might also lower the cost of production. An estimated 200 companies are already pursuing plans to grow algae or process it into biodiesel [126]. A number of start-ups are demonstrating new algae-to-biocrude technology and several companies are even attempting to commercialise microalgal biodiesel processes. Algae biofuels projects include GreenFuel Technologies, Green Star Products, AlgaeLink, Valcent

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– Global Green Solutions, Cellana – Shell/HR Biopetroleum, LiveFuels – Sandia National Laboratories, Chevron – NREL, Chevron – Solazyme, UOP/Honeywell – DARPA, and PetroSun Biofuels Refining; see also refs. [112, 127]. Primafuel, Inc. (Signal Hall, CA; Lund, Sweden) has launched a programme intended to combine upstream algae production with downstream biorefining systems. However, current commercial production of algae for energy applications is non-existent, although small amounts have been made for demonstration purposes by Sapphire Energy (San Diego, CA), Solazyme, Inc. (San Francisco, CA) and Aquaflow Bionomic Corp. (Marlborough, New Zealand). GreenFuel Technologies (Cambridge, MA) uses a photobioreactor approach in a joint project at Aurantia’s Holcim cement plant near Jerez (Spain) to demonstrate how industrial CO2 emissions can be economically recycled to grow algae. Sunrise Ridge Algae, Inc. (Houston, TX) is to commercialise its wastewater algae production technology. Israeli firm Seambiotic (Ashkelon) uses CO2-rich flue gases from coal-fired generators in open algae beds. BioCentric Energy Algae, LLC is building an algae farm in Wuhan (China) to grow 80 t/d of algae for biodiesel production. AlgaeLink is installing photobioreactors in South China (25 ha) for a daily production of 10 000 L. Scottish Bioenergy Co-op Ventures is developing a photobioreactor capable of producing 1600 gallons of biodiesel per year. PetroAlgae, Inc. (Melbourne, FL) is utilising strains of microalgae developed by Arizona State University and bred selectively to produce rapid growth and an extremely high oil yield. PetroSun Inc. is moving forward with 2.56 Bgy algae-to-biodiesel production plans in Auburn and Opelika, AL. It considers algal oil to be a commercially viable alternative feedstock for the biodiesel industry. The quoted market price for algal oil is US$1.71/ gal, compared with US$2.81/gal for soybean oil. PetroSun is also developing a 30 Mgy algae biodiesel facility in Coolidge, AZ. The algal biotechnology company Solazyme, Inc. (San Francisco, CA) and Imperium Renewables (Seattle, WA) have entered into a biodiesel feedstock development agreement in which Solazyme will generate algal oil for Imperium’s biodiesel production process. Chevron Technology Ventures and Solazyme, Inc. will jointly develop and test biodiesel made from algae using Solazyme’s proprietary fermentation technology to optimise algal oil production. This oil can also be used to produce bio-based jet fuel. DARPA is funding several algae-to-jet fuel (JP-8) projects, targeting at a US$3/gal cost. Solazyme, Inc.’s Soladiesel RDTM microalgae-derived biodiesel exceeds the requirements of both ASTM D 6751 and EN 14214, and meets the new ASTM ultra-low-sulphur diesel standards. Soladiesel needs no blending with biodiesel from different feedstocks. Road-testing of Soladiesel/diesel blends, up to B100, have started. Soladiesel is produced from algae that are engineered to secure an oil with an optimised fatty acid profile to ensure

420

Biodiesel science and technology

cold-weather performance, among other properties, and are also modified to grow in the dark in industrial microbial fermentation tanks fed with plant sugars (see Section 5.7.2, pp. 184–5). The lipid composition of algal oil is crucial. The properties of Solazyme’s algal oil are claimed to be far better for biodiesel application than soy, palm and canola. Soladiesel will require at least another two or three years until it is at production economics, defined as parity with fossil fuels. Cellana (joint venture between Royal Dutch Shell and HR Biopetroleum, Inc.) is developing an algae-to-biodiesel project in Hawaiian coastal waters (Kona, 2.5 ha) using native, non-modified algal strains in low-cost, openair ponds. Natural species of microalgae will be screened on the highest yields and the most suitable oil. Portugal is ahead with algal biodiesel plans (SGCEnergia/Vertigro), whereas also Turkey plans to use algae as a raw material. In Austria, BDI is committed to develop biodiesel from algae. Algae may have made headlines in 2008, but will not produce a fuel until after 2016. Biological limitations of algae and cyanobacteria for biofuel production (organism survival, growth and lipid content, CO2 enrichment, light penetration, seasonality, harvest, biosafety) can all be overcome by transgenics, but not in the short term [103]. Algae-to-biodiesel technologies are still not-commercial. Commercial-scale algal biodiesel processes, now about a decade away from hitting the market, will then have a major impact on first and second-generation biodiesels. Biodiesel from microalgae has recently been reviewed [112, 124, 128– 130].

9.6

Vegetable oil soapstocks for biodiesel application

Soapstock (SS) is an underutilised low-quality by-product of the refining of vegetable oils, which consists of a thick alkaline (pH > 9) aqueous emulsion of lipids, containing free fatty acids and salts (soap), other components of the crude oil (triacyl- and phosphoacylglycerols, tocopherols, sterols and pigments) and over 50% water. Soapstock is produced in amounts corresponding to about 6 vol% of crude oil refined. Annual US production of soybean SS exceeds 103 Mlb = 450 kt. The fatty acid content of soapstock can vary according to its vegetable oil source or method of refining. Soybean oil soapstock has a fatty acid profile (typically C16 : 0, 17.2%; C18 : 0, 4.4%; C18 : 1, 15.7%; C18 : 2, 55.6%; C18 : 3, 7.1%) similar to that of SBO (see Table 5.1) [131] and a market value of about US$0.11/kg (on dry weight basis), which is a small fraction only of that of crude SBO (at corresponding US$0.50–0.60/kg). Soapstock is a potentially attractive source of simple fatty acid esters because of low cost, relatively high product volume and centralised production (i.e. no need for collection infrastructure as for most

Processes for biodiesel production from unrefined oils and fats

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waste greases), and absence of extended exposure to high temperature regimes typical of cooking oils. Soapstocks are particularly difficult to transform into FAAEs (biodiesel) not only in view of the free fatty acids and salts but also due to the presence of the substantial amount of water, which is heavily emulsified with lipid constituents. Water inhibits acid-catalysed esterification reactions, but also transesterification reactions since it competes with the alcohol reactant leading to ester hydrolysis and generating free fatty acids. Soapstock feedstocks for biodiesel production may also be derived from coconut, corn, cotton, flax, palm, rapeseed/canola, safflower, sunflower oils, animal fats and waste greases [132]. Various methods for production of FAME from SS have been investigated, including enzymatic catalysis [83, 87, 132–138]. Also the preparation of ethyl esters from soapstocks has been reported [139]. Alkaline esterification-acidic transesterification has been used to transform soybean SS, with composition different from SBO, to biodiesel [135, 136]. A typical compositional analysis of the starting material (wet wt. basis) is: 45.1% water, 10.1% TG, 1.8% DG, < 2% MG, 10.0% FFA, 2.7% phosphatidylcholine, 2.2% phosphatidylinositol and 3.6% phosphatidylethanolamine; fatty acid composition [134]; see Table 5.1. US Patent No. 6,399,800 to Haas et al. [138] describes that the fatty acids in the vegetable oil soapstock (pH 10–11) containing acylglycerides, phosphoglycerides and free fatty acids can be converted at high efficiency and virtually quantitatively to FAAEs in atmospheric conditions and at low T by complete saponification (alkaline hydrolysis) of the fatty acid ester bonds at 373 K for 2 h, thereby converting all fatty acids to the free acid form resulting in a product containing 51.1% water, 26.6% FFAs, and pH = 13.5. After removal of the water by freezedrying the dried saponified soapstock was esterified quantitatively within 2 h using sulphuric acid catalysis (molar ratios of FFA/MeOH/H2SO4 = 1 : 30 : 5) at 308 K. The crude reaction product needs successive washes to remove traces of alcohol, acid, glycerol and unreacted free fatty acid for use as biodiesel within specification. The method is characterised by high consumption of reagents. The procedure relies on a large excess of alcohol, and the cost of recovering the alcohol determines the process economics. Another drawback of the procedure is the significant amount of NaOH contained in the dried saponified feedstock entering the acid-catalysed esterification. Consequently, undesired and insoluble Na2SO4 is precipitated from the esterification reaction. Therefore, an alternative production route is more desirable. The overall reaction scheme may be visualised as follows: NaOH

–H O

2 TG, FFA æ æææ Æ FFA, GL L,, H 2 O, NaOH æ æ Æ saponification ponificatio drying drying

Soapstock

Soaps

MeOH, H SO

2 4 FFA, GL, NaOH æacid æææ catalysisÆ FAMe, GL, Na 2 SO 4

9.10

422

Biodiesel science and technology

In different procedures, acidic fats and oils may be transesterified in a high pressure transesterification process (10 MPa) with a 10-fold molar excess of alcohol in the presence of alkali or zinc catalysts at 513 K [50]. Apart from the need for expensive pressure reactors, high pressure transesterification uses considerably more alcohol at higher temperatures. Also some processes employing soapstocks or soapstock-derived acid oils make use of high temperatures (473 K) in a pressurised system. US Patent No. 5,525,126 to Basu and Norris [83] describes a single-step transesterification process of high FFA containing feedstocks (0.2–50%, eventually with varying fatty acid types and including MGs and DGs) using a non-alkaline Ca/Ba-acetate catalyst (Ca/Ba = 3 : 1) in rather severe reaction conditions (at 473–523 K and 3.4 MPa for 3 h). As the catalyst does not promote formation of soaps the pre-esterification step is eliminated. The procedure is applicable to feedstocks such as soy SS, degummed SBO, grease, turkey fat, etc. The best results are obtained for oils with FFA < 10%, resulting in esters with 0.6–0.8 wt% FFAs. For example, yellow grease (9.4% FFAs) is transformed into a product containing 0.8 wt% FFA. On the other hand, a highly acidulated SS (50 wt% FFA) produces a mixture of esters and FFAs in the ratio of 96 : 4 wt%, and thus needs recycling in order to further lower the FFA contents to 0.8 wt%. Reaction conditions (T, p, t) render the processes impractical and uneconomical for industrial scale production. Typical industrial processing of soapstocks involves ‘acidulation’, wherein H2SO4 and high pressure steam are employed at pH = 1–2 to acidify, heat and mix the heavy SS emulsion to achieve partial acid hydrolysis and/or removal of the acyl- and phosphoacylglycerol ester bonds of the starting material. The acidic conditions also protonate the fatty acid salts, thus greatly reducing their emulsifying properties. Consequently, the heavy soapstock emulsion is destroyed, resulting in spontaneous separation of an aqueous phase (containing sodium sulphate) and a clear, dark oil layer. This layer, termed ‘acid oil’, is typically composed of about 50% FFA, 30–40% tri-, di- and mono-acylglycerols, pigments and other lipophilic materials, and is essentially free of water. Acid oils, readily available commercial products, are used as animal feed ingredients, and as a source of industrial fatty acids with a market value of about half that of refined vegetable oils. As such, they are a desirable feedstock for biodiesel production. Haas [87] has reported the use of acid oils (FFA > 40 wt%) as feedstock for biodiesel. Acid catalysis of a commercial soybean acid oil containing 59.3% FFAs, 28.0% triacylglycerols, 4.4% diacylglycerols and < 1% monoacylglycerols did not achieve efficient and complete esterification of the fatty acids in acid oil (> 15% of the fatty acids remaining in free or glycerol-linked forms even after 26 h) [140]. A more effective use of soybean SS in the production of FAME consists in complete saponification (alkaline hydrolysis) of the acyl- and phosphoacyl-fatty acid glyceride ester bonds

Processes for biodiesel production from unrefined oils and fats

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by adding sufficient alkali to raise the pH to about 11–13 and by injection of steam prior to acidulation, in the aforementioned conditions. In this way, an acid oil rich in FFAs (80–98%) and lacking intact acylglycerols is obtained. Unlike the acid oil, this ‘high-acid’ (HA) acid oil can be esterified readily and almost quantitatively by acid catalysis [140]. Optimal reaction occurred at a molar ratio of fatty acid/alcohol/H2SO4 of 1 : 1.8 : 0.17 and with a reaction time of 14 h at 338 K. The fatty acid ester product lacks unreacted acylglycerols (< 0.1 wt%) but still contains 5–10% unreacted FFA. Complete esterification is presumably prevented by the accumulation of water released by esterification. A simple wash protocol or a second esterification following removal of water by centrifugation reduces the unreacted FFA content to 0.2%, corresponding to near-quantitative esterification of the fatty acids in HA-acid oil, and within established biodiesel specifications [132]. High-acid soybean acid oil is superior to regular soybean acid oil (FFA > 40 wt%) as a feedstock for FAME production since its optimal esterification requires less alcohol and acid, occurs more rapidly and yields a product low in FFA and lacking residual acylglycerols. Attractive features of the method are that it can be conducted at ambient pressure and at relatively low temperatures and does not involve expensive, time-consuming drying of the soapstock and does not produce a solid sodium sulphate waste stream. Acidulated soapstock (AV = 88.2 mg KOH/g) can also be turned into biodiesel complying with ASTM D 6751-7a standards by the Mcgyan process [77]; see Section 9.3.1. US Patent No. 6,768,015 to Luxem and Troy [137] discloses another method for making biodiesel from acidulated soapstock by one-step simultaneous esterification/transesterification of high acid oils (AV = 112.2 mg KOH/g), using acid catalysis (0.1–0.25 wt% H2SO4) at high T, p (403–423 K and 1.7 MPa), thereby reducing or eliminating salt and aqueous waste. Removal of the by-products facilitates the reaction. For lipase-catalysed conversion of acid oil model to FAME, see Fig. 10.7. With regard to engine emissions and performance, biodiesel produced from soy soapstock is comparable to commercially available soy biodiesel [135]. Further research in this area is worthwhile.

9.7

Tall biodiesel

Crude tall oil (CTO) consists of a mixture of 20–60% highly unsaturated fatty acids (TOFAs), comprising many conjugated diene systems, and 20–65% fatty alcohols and terpene derived resin acids (TORAs), such as abietic acid (C20H30O2) and pimaric acid (C20H30O2). CTO (typically AV = 100–175 mg KOH/g; SN = 120–180 mg KOH/g; IV = 140–150 g I2/hg) can be processed to produce various fractions of distilled tall oil [141]. While crude tall oil is a cheap feedstock, refined tall oil has a value almost as much as biodiesel. Distillation of tall oil reduces the resin acid content.

424

Biodiesel science and technology

The resulting tall oil fatty acids (TOFAs) can be used for esterification. Tall oil fatty acid consists mainly of C18 : 2, C18 : 2c and C18 : 1 (oleic) acids. Tall oil fatty acids are easily converted into their methyl esters according to Eqn 9.2 in the presence of H2SO4. Unlike alcoholysis of triglycerides, esterification of TOFAs releases water instead of glycerol as a by-product of the reaction. Where tall oil is used during the esterification reaction, the resin acids present in the starting product are not esterified and may be separated and recovered thanks to differences in volatility [142, 143]. Tall biodiesel may then be produced by direct esterification of tall oil, followed by high vacuum distillation for removal of the non-esterified resin acids, and selective hydrogenation (Fig. 9.5). Without the latter step, which removes polyenes with the formation of monoenes, avoiding complete saturation of the molecule, tall oil methyl esters would not meet biodiesel standards (see Table 15.12). The presence of resin acids in tall oil would result in increased Conradson carbon residue in tall biodiesel. Fatty acid methyl esters and resin acids were recovered from esterified tall oil yields of 93% and 94%, respectively [144]. As reported elsewhere (see Section 7.3.2, pp. 305–8), low-quality, high FFA feedstocks (e.g. TOFA, chicken fat) can be converted to biodiesel in a single step with high yields using supercritical methanol [145]. Tall biodiesel complying with the ASTM D 6751-7a testing procedures may also be produced by the Mcgyan process [77]; see Section 9.3.1.

Tall oil fatty acids

MeOH

Direct esterification

Methylester mixture + resins

Distillation

Resins market

Methylester mixture

Selective hydrogenation

Good quality biodiesel

9.5 Biodiesel fom tall oil.

Processes for biodiesel production from unrefined oils and fats

9.8

425

Bibliography

National Algal Biofuels Technology Roadmap, US DOE, Washington, DC (Draft version, 3 June 2009). Pike Research LLC, Biofuels Markets and Technologies, Boulden, CO (2009). G. Knothe, J. Van Gerpen and J. Krahl (eds), The Biodiesel Handbook, AOCS Press, Urbana, IL (2005). W. Thurmond, Algae 2020: Next Generation Biofuels Markets and Commercialization Outlook, Emerging Markets Online, Houston, TX (2009). G. Knothe, J. Van Gerpen and J. Krahl (eds), The Biodiesel Handbook, AOCS Press, Urbana, IL (2005). J. Otera, Esterification Methods. Reactions and Applications, Wiley-VCH, Weinheim (2003). Making Algae Biodiesel at Home, http://www.making-biodiesel-books.com/ algae-biodiesel.html.

9.9

References

[1] M.P. Dorado, E. Ballesteros, M. Mittelbach and F. J. López, Kinetics parameters affecting the alkali-catalyzed transesterification process of used olive oil, Energy Fuels 18 (2004) 1457–62. [2] M.J. Nye, T.W. Williamson, S. Deshpande, J.H. Schrader, W.H. Snively, T.P. Yurkewich and C.L. French, Conversion of used frying oil to diesel fuel by transesterification: preliminary tests, J. Am. Oil Chem. Soc. 60 (1983) 1598– 601. [3] M.P. Dorado, E. Ballestreros, J.A. de Almeida, C. Schellert, H.P. Löhrlein and R. Krause, An alkali-catalyzed transesterification process for high free fatty acid waste oils, Trans. ASAE 45 (2002) 525–9. [4] M. Mittelbach and H. Enzelsberger, Transesterification of heated rapeseed oil for extending diesel fuel, J. Am. Oil Chem. Soc. 76 (1999) 545–50. [5] M. Mittelbach, Erfahrungen mit Biodiesel aus gebrauchten Speiseölen in Österreich, in Biodiesel: Potenziale, Umweltwirkungen, Praxiserfahrungen (A. Munack and J. Krahl, eds), Bundesforschungsanstalt für Landwirtschaft, Braunschweig (2002), pp 47–52. [6] J.P. Lastella (to Bio-Clean Fuels), Method and apparatus for making biodiesel fuel, PCT Int. Publ. No. WO 2003/022961 A1 (20 March 2003). [7] M. Zappi, R. Hernandez, D. Sparks, J. Horne, M. Brough, S.M. Arora and W.D. Motsenbocker, A Review of the Engineering Aspects of the Biodiesel Industry, Mississippi Biomass Council, Jackson, MS, MSU E-TECH Laboratory Report ET-03-003 (2003), p. 71. [8] W.E. Artz, T. Kinyanjui and M. Cheryan, Deacidification of soybean oil using supercritical fluid and membrane technology, J. Am. Oil Chem. Soc. 82 (2005) 803–8. [9] M. Canakci and J. Van Gerpen, Biodiesel production from oils and fats with high free fatty acids, Trans. ASAE 44 (2001) 1429–36.

426

Biodiesel science and technology

[10] N.O.V. Sonntag, Esterification and interesterification of fatty acids, J. Am. Oil Chem. Soc. 56 (1979) 751A–4A. [11] C. Blandy, D. Gervais, J.-L. Pellegatta, B. Gilot and R. Guiraud, Stearic acid esterification catalysed by titanates: comparative study of homogeneous and heterogeneous systems. J. Mol. Catal. 64 (1991) LI–L6. [12] F.S. Guner, A. Sirkecioğlu, S. Yilmaz, A.T. Erciyes and A. Erdem-Senatalar, Esterification of oleic acid with glycerol in the presence of sulfated iron oxide catalyst J. Am. Oil Chem. Soc. 73 (1996) 347. [13] R. Koster, B. van der Linden, E. Poels and A. Bliek, The mechanism of the gasphase esterification of acetic acid and ethanol over MCM-41, J. Catal. 204 (2001) 333–8. [14] C. Vieville, Z. Mouloungui and A. Gaset, Esterification of oleic acid by methanol catalyzed by p-toluenesulfonic acid and the cation-exchange resins K 2411 and K 1481 in supercritical carbon dioxide, I&EC 32 (1993) 2065–8. [15] M.A. Harmer and Q. Sun, Solid acid catalysis using ion-exchange resins, Appl. Catal. A: Gen. 221 (2001) 45–62. [16] X. Chen, Z. Wu and T. Okuhara, Liquid-phase esterification of acrylic acid with 1-butanol catalyzed by solid acid catalysts, Appl. Catal. A: Gen. 180 (1999) 261–9. [17] N. Özbay, N. Oktar and N.A. Tapan, Direct free fatty acids esterification in waste cooking oils: role of ion-exchange resins, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [18] V.K. Gumaste, A.R.A.S. Deshmukh and B.M. Bhawal, An efficient use of zeolite catalysts for esterification of carboxylic acids, Ind. J. Chem. Soc. B35 (1996) 1174–9. [19] Y. Ma, Q.L. Wang, H. Yan, X. Ji and Q. Qu, Zeolite-catalyzed esterification. I. Synthesis of acetates, benzoates and phthalates, Appl. Catal. A: Gen. 139 (1996) 51–7. [20] A. Corma and H. Garcia, Organic reactions catalyzed over solid acids, Catal. Today 38 (1997) 257–308. [21] A.A. Kiss, A.C. Dimian and G. Rothenberg, Solid acid catalysts for biodiesel production – towards sustainable energy, Adv. Synth. Catal. 348 (2006) 75–81. [22] J. Aracil, A. Corma, M. Rodriguez and N. Sanchez, Process for the selective production of monoesters of diols and triols using zeolitic catalysts, PCT Int. Publ. No. WO 94/13617 (23 June 1994). [23] M. da S. Machado, J. Pérez-Pariente, E. Sastre, D. Cardoso and A.M. de Guereñu, Selective synthesis of glycerol monolaurate with zeolitic molecular sievies, Appl. Catal. A: Gen. 203 (2000) 321–8. [24] J. Pérez-Pariente, I. Díaz, F. Mohino and E. Sastre, Selective synthesis of fatty monoglycerides by using functionalised mesoporous catalysts, Appl. Catal. A: Gen. 254 (2003) 173–88. [25] I.K. Mbaraka, D.R. Radu, V.S.-Y. Lin and B.H. Shanks, Organosulfonic acidfunctionalized mesoporous silicas for the esterification of fatty acid, J. Catal. 219 (2003) 329–36. [26] I.K. Mbarata and B.H. Shanks, Conversion of oils and fats using advanced mesoporous heterogeneous catalysts, J. Am. Oil Chem. Soc. 83 (2006) 79–91. [27] M. Hara, T. Yoshida, A. Takagaki, T. Takata, J.N. Kondo, S. Hayashi and K. Domen, A carbon material as strong protonic acid, Angew. Chem. Intl. Ed. 43 (2004) 2955–8.

Processes for biodiesel production from unrefined oils and fats

427

[28] G.D. Yadav and P.H. Mehta, Heterogeneous catalysis in esterification reactions: preparation of phenethyl acetate and cyclohexyl acetate by using a variety of solid acidic catalysts, I&EC Res. 33 (1994) 2198–208. [29] F. Omota, A.C. Dimian and A. Bliek, Fatty acid esterification by reactive distillation: Part 2. Kinetics-based design for sulphated zirconia catalysts, Chem. Engng. Sci. 58 (2003) 3175–85. [30] S. Ardizzone, C.L. Bianchi, V. Ragaini and B. Vercelli, SO4-ZrO2 catalysts for the esterification of benzoic acid to methylbenzoate, Catal. Lett. 62 (1999) 59–65. [31] G.D. Yadav and A.D. Murkute, Preparation of a novel catalyst UDCaT-5: enhancement in activity of acid-treated zirconia – effect of treatment with chlorosulfonic acid vis-à-vis sulphuric acid, J. Catal. 224 (2004) 218–23. [32] H. Matsuhashi, H. Miyazaki, Y. Kawamura, H. Nakamura and K. Arata, Preparation of solid superacid of sulfated tin oxide with acidity higher than that of sulfated zirconia and its applications to aldol condensation and benzoylation, Chem. Mater. 13 (2001) 3038–42. [33] S. Furuta, H. Matsuhashi and K. Arata, Catalytic action of sulfated tin oxide for etherification and esterification in comparison with sulfated zirconia, Appl. Catal. A: Gen. 269 (2004) 187–91. [34] S. Furuta, H. Matsuhashi and K. Arata, Biodiesel fuel production with solid superacid catalysis in fixed bed reactor under atmospheric pressure, Catal. Comm. 5 (2004) 721–3. [35] M.A. Schwegler, H. van Bekkum and N.A. de Munck, Heteropolyacids as catalysts for the production of phthalate diesters, Appl. Catal. 74 (1991) 191–204. [36] A.T. Guttmann and R.K. Grasselli, Esterification of methacrylic acid with methyl tertiary butyl ether – a process for the manufacture of methyl methacrylate, Appl. Catal. 8 (1983) 57–70. [37] Y. Izumi, R. Hasebe and K. Urabe, Catalysis by heterogeneous supported heteropoly acid, J. Catal. 84 (1983) 402–9. [38] T. Baba and Y. Ono, Heteropolyacids and their salts supported on acidic ionexchange resin as highly active solid-acid catalysts, Appl. Catal. 22 (1986) 321. [39] P. Dupont, J.C. Védrine, E. Paumard, G. Hecquet and F. Lefebvre, Heteropolyacids supported on activated carbon as catalysts for the esterification of acrylic acid by butanol, Appl. Catal. A: Gen. 129 (1995) 217–27. [40] C.S. Caetano, I.M. Fonseca, A.M. Ramos, J. Vital and J.E. Castanheiro, Esterification of free fatty acids with methanol using heteropolyacids immobilized on silica, Catal. Commun. 9 (2008) 1996–9. [41] M.J. Verhoef, P.J. Kooyman, J.A. Peters and H. van Bekkum, A study on the stability of MCM-41-supported heteropoly acids under liquid- and gas-phase esterification conditions, Micropor. Mesopor. Mater. 27 (1999) 365–71. [42] M.G. Kulkarni, R. Gopinath, L.C. Meher and A.K. Dalai, Solid acid catalyzed biodiesel production by simultaneous esterification and transesterification, Green Chem. 8 (2006) 1056–62. [43] O.A. Mascaretti and R.L.E. Furlan, Esterifications, transesterifications, and deesterifications mediated by organotion oxides, hydroxides and alkoxides, Aldrichim. Acta 30 (1997) 55–68. [44] O.A.C. Antunes, Interfaces with the industry, Quim. Nova 28 (2005) 864–75. [45] N. Ergün and P. Panning (to Energea Umwelttechnologie), Method and system for the esterification of fatty acids, PCT Int. Publ. No. WO 2003/087278 A1 (23 Oct. 2003).

428

Biodiesel science and technology

[46] G.J. Suppes, M.A. Dasari, E.J. Doskocil, P.J. Mankidy and M.J. Goff, Transesterification of soybean oil with zeolite and metal catalysts, Appl. Catal. A: Gen. 257 (2004) 213–23. [47] D.G.B. Boocock, S.K. Konar, V. Mao, C. Lee and S. Buligan, Fast formation of high-purity methyl esters from vegetable oils, J. Am. Oil Chem. Soc. 75 (1998) 1167–72. [48] B. Freedman, E.H. Pryde and T.L. Mounts, Variables affecting the yields of fatty esters from transesterified vegetable oils, J. Am. Oil Chem. Soc. 61 (1984) 1638–43. [49] H. Fukuda, A. Kondo and H. Noda, Biodiesel fuel production by transesterification of oils, J. Biosci. Bioengng. 92 (2001) 405–16. [50] F. Ullmann, Ullmann’s Enzyklopädie der technischen Chemie (1976), 4th edn, Vol. II, p. 432. [51] L.O. Buxton (to National Oil Products Co.), Process for testing fatty oils, US Pat. 2,345,097 (28 March 1944). [52] H. Gürbüz, A. Sirkecioğlu, N. Yavasoğlu, G. Ahunbay and S. Türkay, Design of a deacidification process of high acidity biodiesel feedstocks with liquidliquid methanol extraction, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [53] Y. Kawahara and T. Ono (to Kao Soap Co.), Process for producing lower alcohol esters of fatty acids, US Pat. 4,164,506 (9 Mar. 1978). [54] L. Jeromin, E. Peukert and G. Wollmann (to Henkel KA), Process for the pre-esterification of free fatty acids in fats and oils, US Pat. 4,698,186 (6 Oct. 1987). [55] Y. Tanaka, A. Okabe and S. Ando (to Lion Co.), Method for the preparation of a lower alkyl ester of fatty acids, US Pat. 4,303,590 (1 Dec. 1981). [56] F.J. Sprules and D. Price (to Nopco Chemical Co.), Production of fatty esters, US Pat. 2,494,366 (10 Jan. 1950). [57] L. Jeromin, E. Peukert and G. Wollmann, Verfahren zur Vorveresterung freier Fettsäuren in Rohfetten und/oder -ölen, Germ. Pat. DE 3501761 A1 (21 Jan. 1985). [58] J.W. Kram, Improving the bottom line on the front end, Biodiesel Mag. 5(9) (2008) 80–4. [59] M. Mittelbach and M. Koncar (to Vogel & Noot Industrieanlagen), Process for preparing fatty acid alkyl esters, PCT Int. Publ. No. WO 95/02661 (26 Jan. 1995); Eur. Pat. EP 0,708,813 (1 May 1996). [60] H. Lepper and L. Friesenhagen (to Henkel), Verfahren zur Herstellung von Fettsäureestern kurzkettiger aliphatischer Alkohole aus freie Fettsäuren enthaltenden Fetten und oder Ölen, Eur. Pat. EP 127,104 A (5 Dec. 1984). [61] H. Lepper and L. Friesenhagen (to Henkel), Verfahren zur Herstellung von Fettsäuremethylestern, Eur. Pat. EP 184,740 A (18 June 1986). [62] Ex-Rohr Center GmbH and V. Kramaschke, Dieselkraftstoffsubstitut und Verfahren zu dessen Herstellung, Germ. Offenl. DE 19,807,519 A1 (21 Feb. 1998). [63] H.J. Wright, J.B. Segur, H.V. Clark, S.K. Coburn, E.E. Langdon and R.N. DuPuis, A report on ester interchange, Oil Soap 21 (1944) 145–8. [64] R.O. Feuge and A.T. Gros, Modification of vegetable oils. VII. Alkali catalyzed interesterification of peanut oil with ethanol, J. Am. Oil Chem. Soc. 26(3) (1949) 97–102. [65] K. Brunner, R. Frische and R. Ricker (to Frische GmbH), Method for pretreating

Processes for biodiesel production from unrefined oils and fats

[66]

[67]

[68]

[69] [70]

[71]

[72]

[73]

[74]

[75]

[76] [77]

[78]

[79] [80]

[81]

[82]

429

crude oils and raw fats for the production of fatty acid esters, PCT Int. Publ. No. WO 2002/046339 A2 (13 June 2002); US Pat. Appl. 2004/0102640 A1 (27 May 2004). S. Koono, O. Moriya, T. Noguchi and H. Okamura (to Sumitomo Chemical Co.), Process for producing carboxylic acid ester, Eur. Pat. 566,047 A2 (8 Apr. 1993). K.S. Markley, Esters and esterification, in Fatty Acids: Their Chemistry, Properties, Production and Uses (K.S. Markley, ed.), Interscience Publishers, New York, NY (1961), p. 775. R. Stern, G. Hillion, P. Gateau and J.-C. Guibet (to IFP), Procédé de fabrication d’une composition d’esters d’acide gras utilisables comme carburant de substitution du gazole avec de l’álcool éthylique hydrate et composition d’esters ainsi formés, Fr. Pat. FR 2,577,569 A1 (15 Feb. 1985). S. Billenstein, B. Kukla and H. Stühler (to Hoechst AG), Process for the preparation of fatty acid esters of short-chain alcohols, US Pat. 4,668,439 (26 May 1987). S. Billenstein, B. Kukla and H. Stühler (to Hoechst AG), Verfahren zur Herstellung von Fettsäureestern kurzkettiger Alkohole, Germ. Pat. D 3421217 A1 (7 June 1984). T. Dimmig, W. Radig, J. Haupt and T. Dittmar (to L.U.T. Labor- und Umwelttechnik Jena), Verfahren zur Herstellung von Fettsäuremethylestern aus Triglyceriden und Fettsäuren, Germ. Pat. DE 19,908,978 A1 (2 Mar. 1999). D.M. Ginosar and R.V. Fox (to Bechtel BWXT Idaho), Process for producing biodiesel, lubricants, and fuel and lubricant additives in a critical fluid medium, US Pat. 6,887,283 (3 May 2005). M.A. Portnoff, D.A. Purta, M.A. Nasta, J. Zhang and F. Pourarian (to Carnegie Mellon University), Methods for producing biodiesel, US Pat. Appl. 2005/0274065 A1 (15 Dec. 2005). A.K. Gupta, A.K. Bhatnagar and S. Kaul (to Council of Scientific and Industrial Research), Improved process for preparing fatty acid alkylesters using as biodiesel, PCT Int. Publ. No WO 2005/063954 (14 July 2005). O. Rachmaniah, Y.-H., Yu, S.R. Vali, I. Tjondronegoro and A.S. Musfil, A study on acid-catalyzed transesterification of crude rice bran for biodiesel production, Paper presented at World Energy Congress, Sydney (2004). J. Ebert, Nano-style biodiesel production, Biodiesel Mag. 4(10) (2007) 43–8. C.V. McNeff, L.C. McNeff, B.Yan, D.T. Nowlan, H. Rasmussen, A.E. Gyberg, B.J. Krohn, R.L. Fedie and T.R. Hoye, A continuous catalytic system for biodiesel production, Appl. Catal. A: Gen. 343 (2008) 39–48. T. Wimmer (to Vogel & Noot Industrieanlagenbau GmbH), Process for the production of fatty acid esters of lower alcohols, US Pat. 5,399,731 (21 Mar. 1995). M. Canakci and J. Van Gerpen, A pilot plant to produce biodiesel from high fatty acid feedstocks, Trans. ASAE 46 (2003) 945–54. Y. Zhang, M.A. Dubé, D.D. McLean and M. Kates, Biodiesel production from waste cooking oil: 1. Process design and technological assessment, Bioresour. Technol. 89 (2003) 1–16. D.G.B. Boocock, Single-phase process for production of fatty acid methyl esters from mixtures of triglycerides and fatty acids, US Pat. Appl. 2003/083514 A1 (1 May, 2003). G.I. Keim (to Colgate-Palmolive-Peet Co.), Treating fats and fatty oils, US Pat. 2,383,601 (28 Aug, 1945).

430

Biodiesel science and technology

[83] H.N. Basu and M.E. Norris (to Agricultural Utilization Research Institute), Process for production of esters for use as a diesel fuel substitute using a non-alkaline catalyst, US Pat. 5,525,126 (31 Oct. 1994). [84] R. Stern, G. Hillion, P. Gateau and J.-C. Guibet (to IFP), Process for manufacturing a composition of fatty acid esters useful as gas oil substitute motor fuel with hydrated ethyl alcohol and the resultant esters composition, US Pat. 4,695,411 (22 Sept. 1987). [85] S.V. Ghadge and H. Raheman, Biodiesel production from mahua (Madhuca indica) oil having high free fatty acids, Biomass Bioen. 28 (2005) 601–5. [86] M. Sharma, R. Kumar, S.S. Ray, R. Sarin, R.K. Malhotra, R.P. Verma and N.R. Raghunath, Process for producing biodiesel and the product thereof, US Pat. Appl. 2006/094890 A1 (4 May 2006). [87] M.J. Haas, Improving the economics of biodiesel production through the use of low value lipids as feedstocks: vegetable oil soapstock, Fuel Proc. Technol. 86 (2005) 1087–96. [88] M. Koncar and M. Mittelbach (to BDI Anlagenbau Gesellschaft), Method for producing fatty acid alkyl esters, PCT Int. Publ. No. WO 2002/028811 A1 (11 Apr. 2002). [89] R. Muskett and C.A. Anderson (to Biodiesel Australia), Method for production of alkyl esters, PCT Int. Publ. No. WO 2004/048311 (10 June 2004). [90] M. Kleber and W. Heitzer (to Biodiesel Plants), Verfahren zur kontinuierlichen Herstellung eines als Kraft- und/oder Brennstoff geeigneten Fettsäurealkylestergemisches sowie Verwendung des Fettsäurealkylesters als Kraft- bzw. Brennstoff, Germ. Offenl. DE 10043575 A1 (28 Mar. 2002). [91] J.P. Jackam, J.M. Pierce, J.D. Jones and R.H. Talley (to Nova Biosource Technologies, LLC), Production of biodiesel and glycerin from high free fatty acid feedstocks, US Pat. Appl. 2007/0277432 A1 (6 Dec. 2007). [92] G.J. Suppes, K Bockwinkel, S. Lucas, J.B. Botts, M.H. Mason and J.A. Heppert, Calcium carbonate catalyzed alcoholysis of fats and oils, J. Am. Oil Chem. Soc. 78 (2001) 139–45. [93] S.H. Ong, Y.M. Choo, K.Y. Cheah and N. Abu Bakar (to Palm Oil Research and Development Board/Petronas), Production of alkyl esters from oils and fats, Austral. Pat. AU-B- 43519/89 (18 Oct. 1989). [94] Y.K. Hong, Y.S. Huh, W.H. Hong and S.W. Oh, Pretreatment of vegetable oil using ion-exchange resin and biodiesel production, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [95] M. Pell, AmberlystTM BD20 technology: a solid catalyst process for converting high free-fatty acid feedstocks to biodiesel by esterification, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [96] H. Li and W. Xie, Transesterification of soybean oil to biodiesel with Zn/I2 catalyst, Catal. Lett. 107 (2006) 25–30. [97] K. Bevill, Do oil and biodiesel mix? Biodiesel Mag. 5(7) (2008) 64–71. [98] D.G.B. Boocock and B. Gavin, Single-phase process for production of fatty acid methyl esters from mixtures of triglycerides and fatty acids, PCT Int. Publ. No. WO 2001/012581 A1 (22 Feb. 2001). [99] S.V. Ghadge and H. Raheman, Process optimization for biodiesel production from mahua (Madhuca indica) oil using response surface methodology, Bioresour. Technol. 97 (2006) 379–84.

Processes for biodiesel production from unrefined oils and fats

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[100] N. Kumar and P.B. Sharma, Jatropha curcas – a sustainable source for production of biodiesel, J. Sci. Industr. Res. 64 (2005) 883–9. [101] K. Becker, Jatropha curcas: a potential source for tomorrow’s biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [102] W.M.J. Achten, E. Mathijs, L. Verchot, V.P. Singh, R. Aerts and B. Muys, Jatropha diesel fueling sustainability? Biofuel. Bioprod. Biorefin. 1 (2007) 283–91. [103] J. Gressel, Transgenics are imperative for biofuel crops, Plant Sci. 174 (2008) 246–63. [104] K. Pramanik, Properties and use of jatropha curcas oil and diesel fuel blends in compression ignition engine, Renew. Energy 28 (2003) 239–48. [105] J.-D. Choi, J.-Y. Park, S.-C. Park and J.-S. Lee, Production and characterization of biodiesel made from Jatropha oil, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [106] P. Chitra, P. Venkatachalam and A. Sampathrajan, Optimisation of experimental conditions for biodiesel production from alkali-catalysed transesterification of Jatropha curcas oil, Energy Sustain. Developm. 9(3) (2005) 13–18. [107] M. Zhou, M. Lu and B. Liang, Solubility of multicomponent systems in the biodiesel production by transesterification of Jatropha curcas L. oil with methanol, J. Chem. Eng. Data 51 (2006) 1130–5. [108] N. Foidl, G. Foidl, M. Sanchez, M. Mittelbach and S. Hackel, Jatropha curcas L. oil as a source for the production of biofuel in Nicaragua, Bioresour. Technol. 58 (1996) 77–82. [109] R. Lazos and E. García, Experiences in non-toxic jatropha curcas production in State Michoacán, Mexico, Presentation at Second Annual Monographic Conference on Jatropha curcas, Madrid (14–15 May 2008). [110] W. De Greyt, J. Maes, B. Simons, C. Balshaw and D. Miles, Improving yield and quality of biodiesel from Jatropha curcas by optimized seed processing and oil pretreatment, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [111] C.S. Bhaskar, Feedstock strategy and roadmap of biodiesel producer, Presentation at Second Annual Monographic Conference on jatropha curcas, Madrid (14–15 May 2008). [111a] R. Seemamahannop, B. Viswanathan and S. Kapila, A sustainable source of biofuels: Jatropha curcas, Lab. Intl. 23(3) (2009) 10–13. [112] A.O. Alabi, M. Tampier and E. Bibeau, Microalgae Technologies and Processes for Biofuels/Bioenergy Production in British Columbia: Current Technology, Suitability and Barriers to Implementation, Final Report to The British Columbia Innovation Council (14 Jan. 2009); www.bcic.ca/media-and-press/mediareleases/132-2009/598-high-technology-a-priority-for-agriculture. [113] E.-H. Belarbi, E. Molina and Y. Chisti, A process for high yield and scaleable recovery of high purity eicosapentaenoic acid esters from microalgae and fish oil, Enzyme Microb. Technol. 26 (2000) 516–29. [114] E. Bravi, G. Perretti and L. Montanari, Fatty acids by high-performance liquid chromatography and evaporative-light scattering detector, J. Chromatogr. A 1134 (2006) 210–14. [115] P.G. Roughan, Spirulina: a source of dietary gamma-linolenic acid? J. Sci. Food Agric. 47 (1989) 85–93. [116] A. Vonshak, G. Torzillo, P. Accolla and L. Tomaselli, Light and oxygen stress in Sprirulina platensis (cyanobacteria) grown outdoors in tubular reactors, Physiol. Plant. 97 (1996) 175–9.

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Biodiesel science and technology

[ 117] www.algaelink.com/algae_biodiesel_lab_analysis.htm. [118] H. Xu, X. Miao and Q. Wu, High quality biodiesel production from a microalga Chlorella protothecoides by heterotrophic growth in fermenters, J. Biotechnol. 126 (2006) 499–507. [119] Q. Wu, X. Li and X. Han, Heterotrophic fermentation of microalgae for biodiesel production, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [120] X. Miao and Q. Wu, Biodiesel production from heterotrophic microalgal oil, Bioresour. Technol. 97 (2006) 841–6. [121] X. Li, H. Xu and Q. Wu, Large-scale biodiesel production from microalga Chlorella protothecoides through heterotrophic cultivation in bioreactors, Biotechnol. Bioengng. 98(4) (2007) 764–71. [122] J. Obbard, S. Balasubramanian, M. Montefrio and T.T. Doan, Screening of tropical microalgae for cellular lipids for use as a biodiesel feedstock, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [123] J. Sheehan, T. Dunahay, J. Benemann and P. Roessler, A Look Back at the US Department of Energy’s Aquatic Species Program – Biodiesel from Algae, NREL/ TP-580-24190, National Renewable Energy Laboratory, Golden, CO (1998). [124] Y. Chisti, Biodiesel from microalgae, Biotechnol. Adv. 25 (2007) 294–306. [125] M. Tampier, A sober look at biofuels from algae, Biodiesel Mag. 6(4) (2009) 70–3. [126] J.W. Kram, Algae interest align, Biodiesel Mag. 5(11) (2008) 60–5. [127] W. Thurmer, Biodiesel 2020: A Global Market Survey, Emerging Markets Online, Houston, TX (2008). [128] Q. Hu, M. Sommerfeld, E. Jarvis, M. Ghirardi, M. Posewitz, M. Seibert and A. Darzins, Microalgal triacylglycerols as feedstocks for biodiesel production: perspectives and advances, Plant J. 54 (2008) 621–39. [129] B.E. Rittmann, Opportunities for renewable bioenergy using microorganisms, Biotechnol. Bioengng. 100 (2008) 203–12. [130] C. Ratledge and Z. Cohen, Microbial and algal lipids: do they have a future for biodiesel or as commodity oils? Lipid Technol. 20 (2008) 155–60. [131] R.E. Beal (to US Secretary of Agriculture), Feed additive for poultry from soybean oil soapstocks, US Pat. 3,916,031 (28 Oct. 1975). [132] M.J. Haas, K.M. Scott, P.J. Michalski and S. Runyon (to USDA/Runyon Industries), Lipid rich compositions, production of lipid rich compositions, production of fatty acid alkyl esters from heterogeneous lipid mixtures, PCT Int. Publ. No. WO 2003/059847 A1 (24 July 2003). [133] R. Stern, G. Hillion and J.-J. Rouxel (to IFP), Improved process for the production of esters from fatty substances having a natural origin, US Pat. 5,424,466 (13 June 1995). [134] M.J. Haas and K.M. Scott, Combined nonenzymatic-enzymatic method for the synthesis of simple alkyl fatty acid esters from soapstock, J. Am. Oil Chem. Soc. 73 (1996) 1393–401. [135] M.J. Haas, K.M. Scott, T.L. Alleman and R.L. McCormick, Engine performance of biodiesel fuel prepared from soybean soapstock: a high quality renewable fuel produced from a waste feedstock, Energy Fuels 15 (2001) 1207–12. [136] M.J. Haas, S. Bloomer and K. Scott, Simple, high-efficiency synthesis of fatty acid methyl esters from soapstock, J. Am. Oil Chem. Soc. 77 (2000) 373–9. [137] F.J. Luxem and W.M. Troy (to Stepan Company), Method of making alkyl esters under pressure, US Pat. 6,768,015 (27 July 2004).

Processes for biodiesel production from unrefined oils and fats

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[138] M.J. Haas, S. Bloomer and K. Scott (to US Secretary of Agriculture), Process for the production of fatty alkyl esters, US Pat. 6,399,800 (4 June 2002). [139] R. Stern, G. Hillion, P. Gateau and J.C. Guibet, Preparation of methyl and ethyl esters from crude vegetable oils and soapstock, Proc. World Conference Emerging Technol. Fats and Oils Ind., Cannes (4–10 Nov. 1985). [140] M.J. Haas, P.J. Michalski, S. Runyon, A. Nuñez and K.M. Scott, Production of FAME from acid oil, a by-product of vegetable oil refining, J. Am. Oil Chem. Soc. 80 (2003) 97–102. [141] A.M. Rojas, A.M. Schersl and M.A.F. Diaz, Process of refinement of crude tall oil using short path distillation, US Pat. Appl. 2005/0203279 (15 Sept. 2005). [142] A. Demirbaş, Fatty and resin acids recovered from spruce wood by supercritical acetone extraction, Holzforsch. 45 (1991) 337–9. [143] R.E. Babcock and B. Schulte, unpublished results (2008); see Biodiesel Mag. 5(2) (2008) 22. [144] G. Üstün, Separation of fatty acid methyl esters from tall oil by selective adsorption, J. Am. Oil Chem. Soc. 73 (1996) 203–10. [145] J. Ebert, Supercritical methanol for biodiesel production, Biodiesel Mag. 5(4) (2008) 81–5.

10

Biocatalytic production of biodiesel

Abstract: Biocatalytic biodiesel production is an alternative to chemical synthesis of fatty acid alkyl esters. Enzymatic (trans)esterification of cheap feedstocks (glycerides with high free fatty acid and water contents, such as waste oils and fats), in mild reaction conditions leads to cleaner products and significant reduction in solid and liquid waste streams. However, biocatalysts impart a high production cost; enzyme deactivation, inhibitor tolerance and the need for expensive sterile equipment requirements are other characteristics. Since biocatalysts are more expensive than traditional chemical catalysts, their recovery is compulsory from an economical point of view. Enzyme immobilisation on a solid support permits continuous processes. This chapter reviews (trans)esterification of lipases and biocatalysis of (immobilised) lipases for biodiesel synthesis. Key words: Enzymatic transesterification, biocatalytic biodiesel production, screening of lipases, immobilised lipases, reaction conditions.

10.1

Introduction

The chemical approach to synthesising alkyl esters from triglycerides (alkaline catalyst route), though efficient in terms of reaction yield and time, suffers from various deficiencies: ∑ need for refined feedstocks (limited FFA and water contents); ∑ inefficient conversion of feedstocks to esters of higher-chain alcohols; ∑ difficulties in the recovery of glycerol; ∑ need for removal of catalyst and salt residue; and ∑ energy-intensive nature of the process (high T, p). These disadvantages are largely overcome by a biochemical approach, which, however, presents other drawbacks. Biocatalysis refers to catalysis by enzymes, highly complex proteins. Since enzymes are composed of amino acids they may act as either acid or base catalysts through their —COOH, —NH2 and —CONH2 groups. Enzymes may be introduced into the reaction in a purified isolated form or as whole-cell microorganisms. The commercial utility of enzymes is currently limited by several factors. Single enzymes are expensive to isolate and purify and are difficult to recover, whereas whole-cell microorganisms are relatively inexpensive, but less selective. Enzymes are not stable outside a relatively narrow range of operating conditions (solvent, pH, temperature). Many enzymes are only effective in highly dilute solutions and are also easily poisoned. 434

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See also Section 5.8 for microorganisms for biodiesel production.

10.2

Enzymatic (trans)esterification

Lipases (water soluble proteins present in living organisms) belong to the enzymatic class of hydrolases and catalyse splitting of the ester bonds of triglycerides into free fatty acids and di- and monoglycerides (given a sufficiently high water activity) and enable synthesis of esters (esterification, transesterification, interesterification) in low water media. Enzymes operate in aqueous solution and not in oil. Lipases are active at the interface between oil and water. Lipase esterification is possible at ambient temperature and at neutral pH under normal pressure in simple reaction vessels. Enzymes are generally effective biocatalysts for having substrate, functional group and stereo specificity. Regio-specific lipases, catalysing transesterification of position 1 and 3 of triglycerides, may be applied to the production of valuable products such as cocoa butter substitutes [1]. Use of biocatalysis in the production of biodiesel was proposed some 20 years ago but has been pursued more extensively only quite recently, in particular in Japan. Table 10.1 shows the main characteristics of enzymic transesterification and also outlines the scientific and technological challenges. Compared with conventional acid and base catalysts, lipases offer the advantages of a cleaner product more readily isolated, coupled Table 10.1 Main characteristics of enzymatic transesterification Advantages: ∑ Enzymes readily available and stable ∑ High chemo-, regio- and stereoselectivity ∑ High purity products (no by-products) ∑ Suitable for continuous and batch processing ∑ Allowance for cheap feedstocks (high tolerance for FFA and water contents) ∑ Mild reaction conditions (low T, p) ∑ Low alcohol: oil molar ratio (~4) ∑ Ease of alcoholysis with higher and branched alcohols ∑ Environmentally friendly ∑ Simple product recovery, including glycerol (without purification) ∑ No production of chemical waste; no wastewater treatment ∑ Simple production schemes Disadvantages: ∑ Expensive enzymes (few providers) ∑ Relatively low lipase activity ∑ Long reaction time ∑ Enzyme deactivation (water) and recovery ∑ Limited tolerance for organic solvents (need for solvent-free reaction conditions) ∑ Affected by contaminants (e.g. phospholipids)

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with a significant reduction in solid and liquid waste streams. Biocatalysts typically impart a high production cost because of their low reaction rates (compared to basic homogeneous catalysts), short cell life spans, inhibitor tolerance, difficulties in product separation, and expensive sterile equipment requirements. These attributes adversely affect especially the production of large-volume chemicals such as biodiesel. Studies on biocatalytic biodiesel production have considered the use of triglycerides of different origin as well as variation in the alcohol. The use of biocatalysts allows for the synthesis of specific branched and higher alkyl esters, the transesterification of cheap feedstocks (glycerides with high free fatty acid (FFA) and water contents, such as waste oils and fats), easy recovery of glycerol, no complex operations for elimination of catalyst and salt, and requires less organic solvent and lower energy consumption compared with conventional chemical processes. Lipase catalysis allows the simultaneous transesterification of triglycerides and esterification of FFAs in one process step, and, unlike most chemocatalysts, many lipases work well in the presence of water [2, 3]. The main problems to be overcome are enzyme deactivation (e.g. most lipases are poisoned by methanol and other short-chain alcohols) and recovery, product contamination and overall cost. Expensive enzyme catalysts require repeated use by physical immobilisation on a porous carrier (see Section 10.2.1). Deactivation has essentially a physical origin and is due to the immiscibility of low alcohols and triglycerides. Reported reaction times of lipase-catalysed transesterifications vary typically from 6 h up to 36 h for immobilised Candida antarctica [4], which is considerably longer than the 1 h required for conventional base catalysis. However, recent progress has reduced the reaction time to near that of the latter residence time [5]. Specific enzymatic catalysts may require different residence times and reaction temperatures. Reaction temperatures in enzymatic catalysis are low (298–318 K, but might be higher for heatresistant microorganisms). Added advantages are simple product collection, no pollution of catalyst to glycerol, minimal waste residues, and simple production process for both continuous and batch reaction (in stages) (see Fig. 10.1). Compared to the chemically-catalysed reaction, lipase-catalysed transesterification presents significantly reduced costs of down-processing and ecological problems. In the case of animal fats with high melting points, which are usually near the denaturation temperature of lipase, an organic solvent medium is usually needed. In methods involving dissolution of an oil or fat in a solvent (e.g. hexane) in order to react with the alcohol in the presence of a lipase, it is necessary to separate the fatty acid alkyl esters (FAAEs) from the solvent, which increases process complexity and cost. Methanolysis requires the presence of a co-solvent with the need for recovery. For the practical application of making diesel fuel, it is not desirable to use a solvent.

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Solvent

Oil source

437

Reactant

Enzymatic catalyst

Co-product

Reactor Feedback

Biodiesel fuel

Processing plant

10.1 Schematic of a lipase-catalysed biodiesel plant (after ref. [5]).

The most used alcohol, methanol, mixes poorly with the oil or fat, and can even be enzyme denaturing. Lipases are frequently already inactivated by adding more than 1 molar equivalent of methanol, and methanolysis then ceases. For example, (immobilised) C. antarctica lipase is inactivated in a mixture containing > 1.5 molar equivalent of methanol in the oil (Fig. 10.2). However, at least 3 molar equivalents of methanol are required for the complete conversion of a vegetable oil to the corresponding ester. In order to overcome the aforementioned drawbacks, a multi-step addition of this alcohol to the reaction medium has been proposed [4, 6, 7] in order to achieve complete conversion of the oil (see Fig. 10.3). The inactivation has been eliminated both in a two-step methanolysis reaction [4] and in a continuous three-step flow reaction [6]. Since lipase inhibition can sometimes be avoided in the presence of a fatty acid ester, a pre-mixed solution of a fatty acid ester and alcohol can be added stepwise (in batch or continuous operation). Synthesis of FAAEs can thus be performed continuously by adding an alcohol to a reaction mixture in a fixed bed enzyme reactor, collecting a reaction product while maintaining the alcohol at the appropriate concentration, and separating the resultant FAAE from crude glycerol and unreacted glyceride by standing, centrifugation, membrane separation, molecular distillation or superfractionation. In batchwise operation a multi-step method is used. An alcohol is allowed to react at a concentration lower than the lipase inhibition concentration (which refers to a concentration at which the activation of

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Conversion (%)

80

60

40

20

0 0

1

2 3 4 Methanol/oil (mol/mol)

5

6

10.2 Effect of methanol content on methanolysis of vegetable oil (SBO/RSO mixture). Reaction conditions: 10 g oil/methanol, 0.4 g immobilised C. antarctica lipase at 303 K for 24 h (after ref. [6]).

the lipase in the microorganism is inhibited, or the lipase is inactivated irreversibly), and then alcohol is added so that the concentration is lower than the lipase inhibition concentration and further transesterification proceeds. There have been several reports of bacteria exhibiting resistance to toxic solvents. Some Pseudomonas strains have developed substantial methanol tolerance; with lipase from P. fluorescens, high conversions were observed at 4.5 Meq of methanol [7]. Broad screening of lipases and other immobilised enzymes in transesterification is desirable taking into account type, form and amount of lipase, the kind of alcohol and its supply (stepwise to avoid lipase inactivation) and the stoichiometric ratio of the reagents, the presence of organic solvents, the water content in the oil, the presence of glycerol and various operating conditions such as reaction temperature, time (typically 4–16 h) and stirring/ agitation [8–11]. Factors to consider are specificity, substrates and the intended end product. A lipase or enzyme having the ability to degrade a glyceride into glycerol or a partial glyceride and a fatty acid may be 1,3-specific (e.g. Rhizopus oryzae) or non-specific (e.g. C. antarctica). In general, specificity of the enzyme is selected depending on the desired end product. In view of production of fatty acid esters, a non-specific lipase is preferable. Non-specific

Biocatalytic production of biodiesel

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100

Conversion (%)

80

60

40

20

0 0

20

40 Reaction time (h)

60

80

10.3 Time course of methanolysis of vegetable oil (SBO/RSO mixture). Reaction conditions: 28.95 g oil, 1.05 g methanol (molar ratio MeOH/VO = 1 : 1), and 1.2 g immobilised C. antarctica lipase at 303 K. After 24 and 48 h reactions, 1.05 g methanol was added (after ref. [6]).

enzymes such as Pseudomonas cepacia and C. antarctica are particularly useful in the production of alkyl esters for use as biofuels and lubricants. Oils and fats can also be produced by microorganisms, such as Mortierella or Schizochytrium. Essentially any microorganism can be used as long as they produce lipase, such as filamentous fungus (e.g. Aspergillus, Mucor, Phycomyces, Rhizomucor, Penicillium, Rhizopus, Cunninghamella), bacteria (e.g. Pseudomonas, Alkaligenes), or yeasts (e.g. Candida, Cryptococcus). The microorganisms should preferably not allow a lipase to be secreted from the microorganism and be heat resistant. An intact microorganism is one that has not been subjected to any treatment (e.g. with solvents) for improving the permeability of the cell membrane. Most lipases used as catalysts in organic synthesis are of microbial and fungal origin. Typical lipases in powder form can be obtained from Penicillium roqueforti, Aspergillus niger, Mucor javanicus and others. Optimisation of lipase-catalysed transesterification also needs to consider tolerance of the enzymes to organic solvents (including the alcohol) and enzyme immobilisation. Lipases from Candida rugosa, P. cepacia and P. fluorescens display particularly high catalytic ability in methanolysis of soybean oil (SBO) [12].

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The reaction rates of methanolysis catalysed by C. rugosa and P. fluorescens lipases decreased significantly for low water contents, indicating that water prevents the inactivation of these lipases by methanol. On the other hand, the methanolysis reaction rate catalysed by P. cepacia lipase remains high even at low water content. Moreover, P. cepacia gives high methyl ester contents in the reaction mixture up to 2 or 3 molar equivalent of methanol to oil. Lipases strongly resistant to high methanol, such as P. cepacia, are desirable for use in methanolysis reaction processes. As methanol deactivates lipase, Du et al. [13] proposed high yield (92%) interesterification of SBO in continuous operation with methylacetate, which has no negative effect on enzyme activity even after 100-cycle reaction and yields triacetylglycerol (TAG) with higher value than glycerol (Eqn 10.1). Moreover, while glycerol blocks the active site of the lipase, this is not the case for TAG. By interaction of TAG with methanol methylacetate (recycled to the process) and glycerol are formed [14]. CH2-OOCR1 R1-COOCH3 CH2-OOCCH3 | | lipase CH-OOCR2 + 3CH3-COOCH3 I R2-COOCH3 + CH-OOCCH3 | | CH2-OOCR3 R3-COOCH3 CH2-OOCCH3

TG



TAG

10.1

The role of the reaction medium in lipase-catalysed esterifications and transesterifications has been discussed [15]. Various studies report lipasecatalysed production of FAAEs in aqueous medium [3, 12, 16], organic solvents [17–20] and in solvent-free systems [21, 22]. The nature of the reaction medium (different organic solvents and supercritical fluids) markedly influences the microbial lipase activity in (trans)esterification reactions in terms of reaction rates and lipase enantioselectivity [15]. Solvent polarity and hydrophobicity are able to modulate lipase activity greatly. Alcoholysis performed in a water-free medium is favoured because the possible recovery of glycerol from aqueous solutions is difficult and the activity of the enzyme may quickly decrease in aqueous environment. The presence of water is needed for the expression of enzyme activity, but may result in lipase inactivation. While lipases are soluble in aqueous solutions, lipids are not. Using a suitable organic solvent or an emulsifier helps to overcome the problem of intimate contact between enzyme and substrate. In an aqueous medium with an emulsified TG substrate, hydrolysis is the dominant lipase reaction. Lipase from R. oryzae efficiently catalyses the solvent-free methanolysis of SBO in the presence of 4–30 wt% water in the starting materials, but is nearly inactive in the absence of water [3]. The

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kinetics of the reaction suggests a succession of events, namely hydrolysis of the oil to free fatty acids and partial glycerides, followed by esterification of the fatty acids with methanol. On the other hand, in non-aqueous medium, esterification and transesterification reactions become predominant. Nonaqueous enzymology offers several advantages over aqueous biocatalysts such as enhanced substrate solubility, enzyme stability and ability to catalyse unusual reactions [23]. Transesterification using lipase in a non-aqueous system avoids hydrolysis of FAAEs produced. Enzymatic alcoholysis of blackcurrant oil in 96% (v/v) ethanol at 303 K mediated by P. fluorescens lipase resulted in a maximum chemical yield of 52% FAEEs after 8 h and a maximum conversion of 95.4% TG to MG, DG, FAEE and FFA after 16 h [22]. The amount of water present in the reaction media is a critical parameter in biodiesel production influencing biotransformation in non-aqueous media [24]. In the case of waste oils containing a large amount of water, progress of the reaction is inhibited and facilities for removing water are necessary. Less than a monolayer of water is required for an enzyme to show biological activity. As the water level increases, it increases the enzyme flexibility and the expressed activity [25]. With optimum level of water, hydrolytic reactions become significant and the transesterification yield decreases. Addition of 1% (wv–1) water in the case of free enzyme and 0.5% (wv–1) water in the case of immobilised Chromobacterium viscosum (lipase from a microbial source) gave maximum transesterification yields of Jatropha of 73% and 92%, respectively [26]. Iso et al. [27] have also reported that water content is an important parameter for lipase-catalysed transesterification reactions. C. antarctica lipase does not require pre-treatment with water for alcoholysis to occur [6, 17]. Supercritical fluids (SCFs) with their ‘liquid-like’ quality are a unique class of non-aqueous media for enzyme-catalysed reactions since high reaction rates can be achieved. Their lower viscosity compared to organic solvents make them attractive as reaction media to transport reactants and products to and from the enzyme. The most commonly applied enzymes used in SCF conditions are lipases. There are many reasons for the frequent use of lipases in SCFs: increased solubility of hydrophobic lipid substrates in non-polar SCFs, reversal of hydrolysis reactions in favour of synthesis (such as (trans)esterification), tuneable solvent properties (by adjusting T, p), high substrate diffusivity, ease of downstream processing of products, and easy removal of SCF by simple T, p reduction. Supercritical CO2 (scCO2) is an especially attractive process solvent for enzyme catalysis since it is non-hazardous, inexpensive and environmentally friendly. Use of free or immobilised lipases as catalysts in scCO2 is possible since these enzymes are both stable and active in this medium [28–31] and maintain their activity at pressures as high as 400 MPa [32]. Erickson et al. [33] investigated the effect

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of pressure-induced changes in the physical properties of scCO2 on the rate of lipase-catalysed transesterifications. Immobilised lipases from Rhizomucor miehei (Lipozyme“) [34] and C. antarctica (Novozym 435) [35] show ideal catalysis performance with respect to activity and stability when tested in scCO2 as the reaction solvent. Enzymatic catalysis [36], esterification [30, 37–41] and transesterification in scCO2 [42–48] have been reported. In solvent-free systems FAAEs are obtained efficiently only from expensive (branched) higher alcohols, not from MeOH or EtOH. Recently, the kinetic and thermodynamic performance of non-polar media and solvent-free processes have been compared [49]. Lipases effectively catalyse the esterification of free fatty acids [1]. Obviously, during an esterification reaction between an oil source containing a carboxylic acid and an alcohol, water (but no glycerol) is produced as a by-product, which may cause inhibition. Ethyl myristate was produced by continuous enzymatic reaction in scCO2 [50]. Modified lipases (thermostable and alcohol resistant) were used in the preparation of ethyl oleate from triolein and ethanol [51]. Lipase from A. niger, C. rugosa and R. oryzae were almost inactivated during methanolysis of triolein in n-hexane as organic solvent, whereas lipases from Penicillium camembertii, P. cepacia and P. fluorescens showed catalytic activity [7]. The latter showed the highest conversion (48%) after 24 h in this reaction medium. Several commercial lipases were also tested for their ability to catalyse the esterification of glycerol with conjugated linoleic acid and long-chain fatty acids from fish oil (EPA and DHA) [52]. Interesterification leads to changes in the triacylglyceride composition. Enzymatic interesterification (IE) can be used to upgrade cheap and saturated fats to obtain better melting behaviour. Interesterification reaction usually occurs together with hydrolysis, leading to diacyl- and monoacylglycerol. Another product of lipase-catalysed interesterification is FFA. Immobilised Thermomyces lanuginosa lipase was employed to catalyse the interesterification reaction between corn oil (CRO) and tristearin (SSS) at 318 K in a solventfree system [53]. Similarly, immobilised SP 435 lipase from C. antarctica has been used in the interesterification of saturated fat (lard) and an unsaturated vegetable oil (Trisun® Extra, HOSNO) [54]. Palm stearin (PS, solid fat) and palm kernel olein (PKOo, liquid phase) blends were modified by enzymatic interesterification using R. miehei (Lipozyme IM60) at 333 K to achieve the physical properties of margarine fats [55]. Also the enzymatic interesterification of blends of CO-PS [56, 57], TLW-RSO [58] and TLW-SNO [59] were reported. Lipase catalysis is also used for the production of fatty acids by vegetable oil hydrolysis (e.g. POo/C. rugosa [60]). Table 10.2 reports a great variety of bio-oil sources which have been subjected to biocatalysis for biodiesel production. Illustrative examples are lipase-catalysed alcoholysis (with alcohols other than methanol) of SBO and

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Table 10.2 Biocatalysts in (trans)esterification Source bio-oil

Biocatalyst(s)

SBO, BTW Lipase SNO C. antarctica, M. miehei,   P. fluorescens Myristic acid Lipase RSO Lipase RSO C. parapsilosis VOs, TLW G. candidum, P. cepacia, R. delemar PMF R. rhizopodiformis Cod liver oil H. lanuginosa, C. antarctica RSO, SBO, OO, TLW C. antarctica, M. miehei (supported),   P. cepacia, R. delemar,   G. candidum (lipase powders) SBO R. oryzae Whey fractions C. curvatus (Waste) fats/oils Lipase Waste oils/fats Lipase CNO, PKO P. cepacia CPO, PKO H. lanuginosa Crambe oil, camelina oil C. papaya SBO C. rugosa, P. cepacia, P. fluorescens Blackcurrant oil P. fluorescens VOs, TLW, SS, greases Lipase VOs (OO) C. curvatus MOSNO, triolein Various lipases Jatropha oil C. viscosum Waste ABE contg. PMO C. cylindracea CNO, PKO C. rugosa (hydrolysis) and   R. miehei (esterification) Waste ABE contg. VOs Lipase Triolein Modified lipases VOs, grease T. lanuginosa, R. miehei,   C. antarctica and microbial cells RSO Bacterial cultivation (Fungus) SBO Lipase from RMRC BD5

Reference(s) Year(s) [1] [61]

1985 1990

[50] [62] [63] [17] [64] [44, 65] [66]

1993 1994 1994 1996 1997 1997/8 1998

[3] [67] [68] [2] [21] [69] [70] [12] [22] [9] [71] [7] [26] [19] [72]

1999 1999 2000 2000 2000 2000 2000 2001 2001 2002 2002 2003 2004 2004 2005

[73] [51] [74]

2005 2006 2003

[75] [76]

2005 2005

BTW [1], of SNO in petroleum ether under anhydrous conditions [61] and of RSO (with 2-ethyl-1-hexanol) [62], as well as the alcoholysis of palm oil mid-fraction (PMF) by lipase from Rhizopus rhizopodiformis [64]. In the latter case differences were observed between methanolysis and propanolysis in hexane. Transesterification of RSO in aqueous medium catalysed by lipase from Candida parapsilosis was permitted by methanol inhibition of hydrolysis of esters [63]. Commercially available lipases have varied specificities in the transesterification reaction. Foglia et al. [66] screened 1,3-specific (M. miehei and R. delemar), acyl-specific (G. candidum) and non-specific (C. antarctica and P. cepacia) lipases for their transesterification ability of RSO, SBO, OO and TLW with short-chain primary alcohols (MeOH, EtOH,

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i-PrOH, i-BuOH) using various solvents (Figs 10.4 and 10.5). Since waste oils inevitably contain a certain amount of water, industrially it is necessary to be able to apply a lipase that efficiently catalyses methanolysis even in the presence of water. BDF production from plant oil catalysed by R. oryzae lipase in a water-containing system without an organic solvent was reported [3]. Biodiesel has also been produced in a combined microbial/chemical process in which Cryptococcus curvatus (C. curvata or A. curvatem) in deproteinated whey, a waste product of the dairy industry, produces an intracellular fatty acid-rich triglyceride, or ‘single-cell oil’ [67]. After disruption of the cells, the oil is removed from the culture broth and cell fragments and is directly subjected to known chemical treatment to produce FAME. Transesterification of waste oils/fats has been carried out in solvent-free conditions with an esterase in the presence of 1–20 wt% water [2]. Solvent-free glycerolysis of CPO and PKO catalysed by 1,3-specific lipase from Humicola lanuginosa was used for monoacyl glycerol production [69]. CNO and PKO were utilised to produce medium-chain glycerides (mixture TLW

SBO

RSO

100

Conversion (%)

80

60

40

20

0

Methyl

Ethyl Isopropyl Alkyl esters

Isobutyl

10.4 Lipase-catalysed transesterification of fats and oils using M. miehei (primary alcohols) and C. antarctica (secondary alcohols) (after ref. [66]).

Biocatalytic production of biodiesel Methyl

Ethyl

Isopropyl

445

2-Butyl

100

Conversion (%)

80

60

40

20

0

2.1% FFA

9.0% FFA 20.4% FFA Alkyl esters

32.9% FFA

10.5 Enzymatic transesterification and esterification of free fatty acid (FFA)-containing triglyceride feedstocks using M. miehei (primary alcohols) and C. antarctica (secondary alcohols) lipases (after ref. [66]).

of MG, DG and TG) by a combination of lipase-catalysed hydrolysis (with C. rugosa) and esterification (with R. miehei) [72]. Also lipase-catalysed alcoholysis of crambe and camelina oils was reported [70]. Lipase (C. curvatus)-catalysed methanolysis of olive oil was not affected by the presence of organic solvent and water [71]. Activated bleaching earth (ABE), containing up to 40% of waste palm oil, was used for the production of FAAEs using C. cylindracea lipase in an organic solvent system [19]. Similarly, Kojima and Park [73] described lipase-catalysed FAME production from residual vegetable oils (about 35–40 wt%) embedded in filtered waste activated bleaching earth (ABE), a mineral acid-treated montmorillonite clay used as an adsorbent in decolorisation of fat and oil refining (80 kt/yr discharged in Japan). Cao et al. [75] have reported biodiesel fuel production by fermentation of rapeseed (245 kg RSO from 1000 kg seeds). Also the biocatalytic transesterification of oils and fats (waste restaurant grease, (transgenic) SBO, RSO, engineered microalga oil, castor oil, industrial waste oil, etc.)

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with methanol in 3–4 serial enzyme-fixed bed reactors was reported using T. lanuginosa, R. miehei, C. antarctica and microbial cells [74]. SBME in 56% yield was produced in 24 h from 2.5 wt% RMRC BD5 lipase-producing free cells at 303 K in the presence of 10 wt% water [76]. Enzymatic transesterification of RME and trimethylolpropane leads to trimethylolpropane triesters which can be used as raw materials for biodegradable hydraulic fluids [77].

10.2.1 Biocatalysis by immobilised lipases Since biocatalysts are more expensive than traditional chemical catalysts, their recycling is essential to running an economic operation. This is possible through enzyme immobilisation on solid supports, which also permits continuous processes. Lipases may be immobilised by entrapment, as e.g. in a phyllosilicate sol-gel matrix or polymer. Physical immobilisation of enzymes allows repeated use and facilitates enzyme recovery from the reaction medium, improves stability, offers better control of reactions, and provides higher purity and product yields. Disadvantages include the time needed for isolation and immobilisation. Moreover, immobilisation of enzymes might also decrease their intrinsic activity. Immobilised lipases show higher affinity to methanol than to triglycerides. Consequently, when the alcohol is absorbed in the pores of an immobilised lipase, access of TGs is blocked. Moreover, the liberated glycerol can also inhibit the reaction by limiting substrate and product diffusion due to its insolubility in oil or organic solvent. Regeneration of a deactivated immobilised lipase may only be partial. Biocatalysis by immobilised lipases is considered as an alternative technology to produce biodiesel [78]. Immobilised C. antarctica is stable for at least two years [4]. This suggests that the cost of producing biodiesel fuel by a three-step flow reaction may become lower than that by chemical processing. There have been several reports on esterification of FFA with methanol or ethanol [79–82]. Bloomer et al. [79, 80] achieved an efficient organic solvent system of producing long-chain fatty acid ethyl esters with immobilised R. miehei lipase. Application of this system to conversion of waste FFA to their methyl esters requires removal of solvent after the reaction. Waste tuna FFAs (obtained in the enzymatic production process of a docosahexaenoic acid-rich oil from tuna oil) can be esterified at 303 K with 2 Meq of MeOH using 1.0 wt% immobilised C. antarctica lipase in an organic solvent-free system [92]. As shown in Table 10.3, various studies have also appeared on the synthesis of oleic acid esters catalysed by immobilised lipase [40, 45]. Immobilised R. miehei does not lose its activity when exposed to CO2 at 30 MPa for 24 h. Oleic acid esterification by EtOH catalysed by immobilised M. miehei in

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Table 10.3 Immobilised biocatalysts in (trans)esterification Source bio-oil

Biocatalyst(s)

Oleic acid Immobilised M. miehei Stearic acid Immobilised R. miehei Oleic acid Immobilised R. miehei Corn oil Immobilised lipase VOs, TLW Immobilised M. miehei,   C. antarctica Soapstock Immobilised lipases SNO Immobilised lipase Cod liver oil Immobilised H. lanuginosa,   C. antarctica Tuna oil Immobilised C. antarctica Restaurant grease PS-30 P. cepacia lipase SBO/RSO mixture Immobilised C. antarctica Crambe oil, Immobilised C. antarctica,   camelina oil   R. miehei Triolein, SFO Immobilised P. fluorescens Waste oil Immobilised C. antarctica Lard, restaurant grease Immobilised lipase SBO, animal fat, Immobilised P. fluorescens,   waste oils/fats   C. antarctica CSO Immobilised C. antarctica Degummed SBO Immobilised C. antarctica Waste tuna - FFA Immobilised C. antarctica SNO Immobilised C. antarctica MOSNO, triolein Immobilised P. fluorescens,   R. miehei Variousa Immobilised lipase RSO Immobilised C. antarctica SBO Immobilised C. antarctica SNO Immobilised porcine pancreatic   lipase Oleic acid Immobilised C. rugosa,   porcine pancreatic lipase RSO, SBO, PNO, Immobilised lipase   maize, lard oils Acid oil (TG/FFA) Immobilised C. antarctica SNO Various immobilised lipases Triolein Immobilised C. antarctica,   P. cepacia, R. miehei SNO Immobilised R. miehei,   H. insolens Salicornia oil Immobilised porcine pancreatic   lipase VOs, (waste) Immobilised lipaseb   animal fats, grease (Waste) fats/oils, fish Recombinant lipase-containing   oils, microbial oils   intact immobilised   microorganism SNO Lipozyme IM®20 SNO Lipozyme TL-IM a

Reference(s) Year(s) [40] [79, 80] [45] [47] [17]

1992 1992 1996 1996 1996

[83] [84] [43, 44]

1996 1998 1998

[85] [86] [4, 6] [70]

1999 1999 1999, 2000 2000

[27] [87] [88] [89]

2001 2001 2002 2002

[90] [91] [92] [93] [7]

2002 2002 2002 2002 2003

[94] [95] [13, 96] [97]

2003 2004 2004 2004

[98]

2004

[99]

2005

[100, 101] [11] [102]

2005/7 2005 2005

[103]

2006

[104]

2006

[5]

2006

[105]

2006

[78] [106]

2007 2007

SBO, CSO, RSO, OO, SNO, corn oil, rice bran oil, fish oil, microbial oil. At least one of C. antarctica, T. lanuginosa, P. fluorescens, P. cepacia and C. viscosum.

b

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Biodiesel science and technology

scCO2 and hexane were compared [40]. The stability of the enzyme was affected by the water content. Enzyme (M. miehei lipase immobilised on macroporous anion-exchange resin; Lipozyme IM)-catalysed hydrolysis of canola oil in scCO2 to DG, MG, glycerol and FFAs was reported [107]. Lipase-catalysed esterification of glycerol and oleic acid in iso-octane and hexane was described [98]. C. rugosa lipase and porcine pancreas lipase manifested contrasting positional specificities in glyceride synthesis; the water content in the reaction mixture was of primary importance. C. antarctica lipase B immobilised on polyacryl (Novozym 435) is a heterogeneous biocatalyst of excellent stability and activity. Refined CSO was transesterified with primary and secondary alcohols with immobilised C. antarctica in a solvent-free system with 91.5% (FAME) yield at 323 K after 7 h [90]. Similarly, the enzymatic biodiesel production from SNO by Novozym 435 in a solvent-free system was reported [93]. Immobilised lipase methanolysis of corn oil in flowing scCO2 was described [47], as well as continuous three-step methanolysis of a SBO/RSO mixture using 4% immobilised C. antarctica lipase with 98.4% yield after 48 h at 303 K (see also Fig. 10.3) [4, 6]. More than 95% of the ester conversion was maintained for at least 50 cycles of the reaction (100 days). Also, in esterification of linoleic acid (C18 : 2) with methanol, the half-time of the immobilised biocatalyst C. antarctica exceeded 100 days [95]. Immobilised P. fluorescens lipase is very popular as a biocatalyst compared to mobilised biocatalysts as its activity is more effective and it can be repeatedly used without decrease in activity [27]. Studies to genetically engineer this product are being carried out [108]. Immobilised P. fluorescens (on polypropylene EP100) was the best among several microbial lipases tested for methanolysis activity in a n-hexane system with 90% conversion of MOSNO after 48 h [7]. Also, with immobilised lipase from R. miehei (Lipozyme RMIM) in a solvent-free system, high conversion (> 80%) was possible in a three-step methanolysis protocol (molar ratio SNO/MeOH = 1 : 4.5). Transesterification of triolein (OOO) and SFO was carried out using various immobilised lipases (P. fluorescens, P. cepacia, M. javanicus, C. rugosa, R. niveus) in non-aqueous conditions [27]. P. fluorescens on porous kaolinite (Toyonite 200-M) showed the highest activity (100% conversion at 323–333 K in 10–20 h) with C3 and C4 alcohols, with quite similar results for OOO and SFO (Fig. 10.6). For methanolysis and ethanolysis the organic solvent 1,4-dioxine was needed for homogenisation of the reaction mixture. The activity of the immobilised enzymes in the non-aqueous system was affected by the water content; the highest conversion was reported for 0.3 wt% of water. Similarly, the water content of the support for the lipase of M. miehei immobilised on a macroporous anion resin is a determining factor in the catalytic activity of the enzyme for esterification [30, 31]. Immobilisation

Biocatalytic production of biodiesel

449

100

Conversion (%)

80

60

40

20 Triolein Safflower oil 0 0

2

4 6 Reaction time (h)

8

10

10.6 Comparison of triolein and safflower oil in transesterification using immobilised P. fluorescens lipase (after ref. [27]).

of Chromobacterium viscosum on Celite-545 enhanced the reaction yield of Jatropha oil with methanol at 313 K from 62% (for free lipase) to 71% with a process time of 8 h [26]. Further addition of water raised the yield to 92%, which is close to that achieved by chemical transesterification (93%). It is interesting to note that Jatropha seeds themselves contain lipase activity which could also catalyse transesterification reactions [109]. Solinas et al. [102] have compared the activity of immobilised R. miehei (Lipozyme RMIM), C. antarctica (Novozym 435) and P. cepacia (PS-C and PS-D) in the solvent-free three-stage batch reaction of triolein with C1-C5 alcohols at 313 K. The PS-C and PS-D preparations differed in the immobilising support (ceramic particles and diatomaceous earth, respectively). P. cepacia (PS-D) was most active with 100% conversion in butanolysis to oleic acid butyl esters after 6 h at 313 K for BuOH/triolein = 3. Low conversions in methanolysis were caused by the poor miscibility of methanol and triolein and denaturation of the enzyme. Immobilised lipase from P. cepacia on kaolinite was previously used for triolein reaction with butanol, but with very different results [27]. This has tentatively been ascribed to differences in the strength of the interaction between enzyme and support [102]. Wu et al. [86] used P. cepacia lipase for biodiesel production from recycled restaurant grease and ethanol. This lipase is not inactivated by methanol when used as a powder preparation [12].

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Biodiesel science and technology

Immobilised lipase-catalysed ethanolysis of SNO was carried out in a solvent-free medium [78, 84]. Also the solvent-free four-step ethanolysis process of SNO catalysed by an immobilised 1,3-specific porcine pancreatic lipase was reported [97]. In a critical evaluation of six commercially available immobilised lipases and seven simple monohydric alcohols (including straight and branched-chain primary and secondary alcohols) in the solvent-free enzymatic production of alkyl esters of SNO, very considerable differences in alcoholysis performance were observed. For most of the alcohols, Novozym 435 produced the highest FAAE yield (>90%) for methanol, absolute ethanol and 1-propanol [11]. Overall, 96% ethanol was the preferred alcohol for all lipases except Novozym 435 and ethanolysis reactions reached the maximal conversion efficiency. Increasing the water content in the system resulted in an increased degree of conversion for all lipases except Novozym 435. Enzymatic transesterification of SNO in an aqueous-oil biphasic system with methanol was catalysed by free and immobilised lipase from R. miehei (Palatase 20000 L) and Humicola insolens (Lipozyme TL 100 L) [103]. Continuous lipase-catalysed alcoholysis of SNO using immobilised Lipozyme TL-IM was also reported [106]. The methyl ester yield of Novozym 435 (C. antarctica on acrylic resin)catalysed transesterification of crude SBO (with high phospholipid content) by three-step addition of methanol is significantly lower than that of refined SBO [91, 96]. Apparently, the substances removed in the degumming step (mainly phospholipids, but also free acids and water) inhibit methanolysis of soybean triglycerides. Water activity also plays a role but FFAs have no negative effect on the enzymic transesterification. Biodiesel grade (acid number < 1 mg KOH/g) was obtained by lipase catalysis (and other feedstocks) at 318 K from one-phase solutions of SBO and alcohol in inert organic solvents using a two-reactor procedure with residence times for crude oil (first stage) and recycled crude biodiesel (second stage) of about 60 and 17 min, respectively [5]. Alcoholysis of Salicornia brachiata oil, mediated by free and immobilised porcine pancreatic lipase (on chitosan), was carried out at 298 K using methanol in hexane and acetone in 45–55% yields after 12 h [104]. As immobilised lipases may be poisoned by lower alcohols, complete regeneration is not always easily achieved. Germ. Offenl. DE 10,217,607 to Wu and Chen [89] discloses the application of a washing solvent for deactivated immobilised lipases. Requirements for the solvent are non-toxicity to the lipase and good solubility for oils and fats, alcohol and water. SBO methanolysis with Novozym 435 (C. antarctica) after pre-treatment with various solvents (e.g. isopropanol, SBO, biodiesel) was described. Yang et al. [94] have reported a method for producing glycerol diester from a variety of glycerides (vegetable, fish and microbial oils) using a lower alcohol (at molar ratio 1 : 0.3 to 1 : 1.5) in the presence of immobilised lipase

Biocatalytic production of biodiesel

451

for 1–10 h (in reactor) or for ≥ 5 min (in column reactor). Lipases from immobilised H. lanuginosa and C. antarctica were used for ethanolysis of cod liver oil in scCO2 conditions [43, 44]. Stepwise ethanolysis (in order to avoid inactivation of the lipase) of tuna oil using immobilised C. antarctica has been reported [85]. In the ester production from (acetone) fractionated lard and restaurant grease, the immobilised lipase (Chirazyme L-2) activity was hindered by excess amounts (exceeding 1 mol) of methanol [88]. Tallow-methyl ester was obtained with 74% conversion in a three-step reaction. Also the enzymatic three-step methanolysis of waste edible oil to biodiesel fuel with immobilised C. antarctica lipase in a fixed-bed reactor was reported [87]. A model substrate of acid oil (mixture of TG and FFA) was used for conversion to FAME by immobilised C. antarctica lipase [100, 101]. FFAs in the TG/FFA mixture were efficiently esterified with methanol, but the water generated by the esterification significantly inhibited methanolysis of the triglycerides. A two-step process (Fig. 10.7) with intermediate dehydration achieved > 98.5 wt% FAME after a 24 h reaction. The immobilised lipase was very stable in the first- and second-step reactions and could be used for over 100 days without significant loss of activity.

FFAs TGs First step: Methyl esterification of FFAs

MeOH FAMEs TGs MeOH Water

MeOH Water FAMEs TGs Second step: Methanolysis of TGs

MeOH

FAMEs

10.7 Two-step reaction system to convert acid oil to fatty acid methyl esters using immobilised C. antarctica lipase. The lipase concentrations were 0.5 wt% and 6 wt% for the first and second step, respectively (after ref. [101]).

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Biodiesel science and technology

Soapstock was evaluated as a feedstock for lipase-catalysed production of biodiesel [83]. The approach taken was to first conduct an alkali-catalysed transesterification of the glycerol-linked fatty acids followed by lipasecatalysed esterification of the free fatty acids in the preparation that were not esterified by the alkaline transesterification. Freeze-drying was employed to remove water from the SS prior to the reaction. Various commercially available immobilised lipases examined did not exhibit any transesterification activity at alkaline pH values (pH = 13). After adjusting pH to neutrality (pH = 6–7) under optimal conditions at 315 K, only Novo Lipozyme SP435 at a dosage of 1.1% (w/w) showed incomplete enzymatic esterification (63% of FFAs in the post-alcoholysis mixture), thus resulting in a product with FFA content greatly exceeding the specifications of biodiesel. The optimal water concentration was 0.70% (vol./vol.). This line of research was pursued no further. Crambe oil and camelina oil were transesterified solvent-free with longchain alcohols such as oleyl alcohol, the alcohols derived from crambe and camelina oils, n-octanol, as well as isopropanol using Novozym 435 (immobilised lipase B from C. antarctica), Lipozyme IM (immobilised lipase from R. miehei) and papaya (Carica papaya) latex lipase as biocatalysts mainly with the aim of preparing wax esters and ‘bio esters’ for cosmetics applications [70]. It is of interest to notice that alcoholysis of crambe and camelina oils with isopropanol could not be achieved by alkali (KOH) catalysis [110]. In detail, a typical process for production of biodiesel oil utilising lipase comprises the following steps: ∑

filtering the biological grease (RSO, SBO, PNO, maize, or lard oil) to remove impurities, stirring to emulsify; ∑ allowing grease and methanol at a molar ratio of 1 : 1 to 2 : 1, immobilised enzyme and organic solvent (petroleum ether, isooctane, n-hexane, n-heptane, cyclohexane or trichloromethane) at ratios of enzyme/VO 1 : 10 to 1 : 25, organic solvent/VO 1 : 0.5 to 1 : 1.5 to react at 303 K ± 15 K for 4–18 h under mixing; and ∑ separating the enzyme from the reaction product, centrifuging to stratify, standing to separate the lower coarse glycerol layer, distilling the upper liquid to recover the organic solvent and obtaining the final biodiesel oil [99]. The process is simple and high in yield, and shows no pollution. Most of the aforementioned problems of lipase catalysis have been overcome by Kansai Chemical Engineering Co. [105], which has developed a low-cost process for efficiently producing FAAEs by reacting an immobilised intact microorganism producing a recombinant lipase with a (waste) fat or oil and an inexpensive linear lower alcohol (with improved cell membrane

Biocatalytic production of biodiesel

453

permeability) in a system (almost) completely free of solvents in the presence of large amounts of water (3–30 wt%). In the process the alcohol concentration is kept below the lipase inhibitory concentration, or a fatty acid ester is added to the reaction system to prevent deactivation of the lipase. In using microorganisms themselves, permeability of the cell membrane usually requires a costly and time-consuming solvent treatment [111]. However, because the intact microorganism used by Kansai is not exposed to solvent treatment the preparation of the fatty acid ester is simple. The process allows recycling of waste oils and provides biodiesel fuel with little environmental pollution. As it is unnecessary to isolate an enzyme, the process required for purification of the enzyme can be eliminated. As the conventionally used solvents for reaction and treatment of microorganisms are eliminated, consequently so too are the facilities required for collection of the solvents. The use of whole-cell biocatalysts immobilised within a biomass support particle like lipases is of advantage to the biodiesel industry. Locally derived strains of whole-cell, immobilised moulds were used for biocatalysis of marine algal oil into biodiesel [112]. Fukuda [10, 113] has recently reviewed usage of whole-cell enzyme biocatalysts in lipase transesterification of triglycerides, and in particular BDF production by methanolysis catalysed by lipase on the cell surfaces of R. oryzae IFO4697. Direct use of intracellular lipase of R. oryzae cells as whole-cell biocatalyst [114, 115] represents an attractive alternative to the use of extracellular lipase [3, 4, 6, 17, 61]. The product quality obtainable in the operational conditions of lipase catalysis (see ref. [5]), at lower reaction temperatures and with residence times comparable to alkaline catalysis, justify some optimism. Lipase-catalysed transesterification of vegetable oil for the production of alkyl esters should be further improved in order to make it economically applicable. Problems to be solved are the maximisation of the conversion rate in solvent-free alcohols, scale-up to provide sufficient quantities, development of new reactor systems with immobilised biocatalysts and addition of alcohol in several portions, the use of extracellular lipases tolerant to organic solvents, intracellular lipases (i.e. whole microbial cells) and genetically modified microorganisms (‘intelligent’ yeasts) [8]. A significant improvement in the biocatalyst operational life would contribute substantially to reduction of the biodiesel production cost [13]. Immobilisation of lipases is one of the strategies presented so far to solve this problem. Equally important is the finding that regeneration of deactivated immobilised lipases can be achieved by washing with higher alcohols (C 3C4) [89]. In fact, the activity of (commercial) immobilised lipases can be increased significantly (by a factor of 8–10) by such a solvent pre-treatment. The other approach is illustrated by the cytoplasmic overexpression of R. oryzae lipase in recombinant Saccharomyces cerevisiae (bakers’ yeast) with subsequent freeze-thawing and air drying resulting in a whole-cell biocatalyst that catalyses methanolysis in a solvent-free reaction system [116, 117].

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Biodiesel science and technology

Enzyme-catalysed conversions of lipid feedstock for biodiesel production have been reviewed [108, 118]. Enzymatic processes to produce FAME from vegetable oil are slow to become commercially available. Although it is feasible to expand heterotrophic Chlorella fermentation for enzymatic biodiesel production at the industrial level (see Section 9.5), the process is not yet competitive with conventional diesel fuel. However, enzymatic biodiesel production is gaining ground, with one plant in China using Novozym enzymes on a consistent basis.

10.3

Bioplastic-to-biodiesel

A ‘fuel-latent biopolyester’, obtained from plant oils (e.g. SBO) by conversion into w-hydroxy fatty acids using a gene-altered yeast followed by polymerisation with lipase from C. antarctica as a catalyst, has been designed for double duty, first as a packaging material and then as a biofuel [119]. A naturally occurring enzyme (gene-altered cutinase from E. coli) may be used to break down a suspension of shredded biopolyester waste in lukewarm water to biodiesel in 3–5 days.

10.4

Bibliography

C. Hou and J.-F. Shaw (eds), Biocatalysis and Biotechnology for Functional Foods and Industrial Products, AOCS Press, Urbana, IL (2007). R.C. Ramesh (ed.), Microbial Biotechnology in Agriculture and Aquaculture, Science Publishers, Inc., Enfield, NH (2005). A. Bommarius and B.R. Riebel, Biocatalysis, Wiley-VCH, Weinheim (2004). Y. Asano, H. Fukuda, Y. Shimada, A. Tanaka and M. Ueda (eds), Special Issue on Biofuel Production Process by Novel Biocatalysts, in J. Mol. Catal. B.: Enzym. 17(3–5) (2002). A.J.J. Straathof and P. Adlercreutz (eds), Applied Biocatalysis, Harwood Academic Publishers, Amsterdam (2000). V. Moses, R.E. Cape and D.G. Springham (eds), Biotechnology: The Science and the Biomass, Harwood, New York, NY (1999). M.C. Flickinger and S.W. Drew (eds), Encyclopedia of Bioprocess Technology: Fermentation, Biocatalysis and Bioseparation, John Wiley & Sons, Inc., New York, NY (1999). T. Bugg, An Introduction to Enzyme and Coenzyme Chemistry, Blackwell Science, Oxford (1997). J.S. Dordick (ed.), Biocatalysis for Industry, Plenum Press, New York, NY (1991).

Biocatalytic production of biodiesel

10.5

455

References

[1] G. Lazar and K. Henkel, Estersynthesen mit Lipasen, Fette-Seifen-Anstrichm. 87 (1985) 394–400. [2] H. Fukuda, K. Otsuka and F. Nomoto (to Nagase and Co., Ltd.), Transesterification, Jpn. Kokai Tokkyo Koho JP 2000/270886 (3 Oct. 2000). [3] M. Kaieda, T. Samukawa, T. Matsumoto, K. Ban, A. Kondo, Y. Shimada, H. Noda, F. Nomoto, K. Ohtsuka, E. Izumoto and H. Fukuda, Biodiesel fuel production from plant oil catalyzed by Rhizopus oryzae lipase in a water-containing system without an organic solvent, J. Biosci. Bioengng. 88 (1999) 627–31. [4] Y. Watanabe, Y. Shimada, A. Sugihara, H. Noda, H. Fukuda and Y. Tominaga, Continuous production of biodiesel fuel from vegetable oil using immobilized Candida antartica lipase, J. Am. Oil Chem. Soc. 77 (2000) 355–60. [5] C.-C. Chou, Fuel production, US Pat. Appl. 2006/063242 A1 (23 Mar. 2006). [6] Y. Shimada, Y. Watanabe, T. Samukawa, A. Sugihara, H. Noda, H. Fukuda and Y. Tominaga, Conversion of vegetable oil to biodiesel using immobilized Candida antarctica lipase, J. Am. Oil Chem. Soc. 76 (1999) 789–93. [7] M.M. Soumanou and U.T. Bornscheuer, Improvement in lipase-catalyzed synthesis of fatty acid methyl esters from sunflower oil, Enzyme Microb. Technol. 33 (2003) 97–103. [8] O.S. Stamenković, M.L. Lazić, V.B. Veljković and D.U. Skala, Biodiesel production by enzyme-catalyzed transesterification, Hemijska Industrija 59 (2005) 49–59. [9] M.J. Haas, G.J. Piazza and T.A. Foglia, Enzymatic approaches to the production of biodiesel fuels, in Lipid Biotechnology (T.M. Kuo and H.W. Gardner, eds), Marcel Dekker, New York, NY (2002), pp. 587–98. [10] H. Fukuda, Production process for biodiesel fuel from vegetable oil, Kemikaru Enjiniyaringu 46 (2001) 943–8. [11] L. Deng, X. Xu, G.G. Haraldsson, T. Tan and F. Wang, Enzymatic production of alkyl esters through alcoholysis: a critical evaluation of lipases and alcohols, J. Am. Oil Chem. Soc. 82 (2005) 341–7. [12] M. Kaieda, T. Samukawa, A. Kondo and H. Fukuda, Effect of methanol and water contents on production of biodiesel fuel from plant oil catalyzed by various lipases in a solvent-free system, J. Biosci. Bioengng. 91 (2001) 12–15. [13] W. Du, Y. Xu, D. Liu and J. Zeng, Comparative study on lipase-catalyzed transformation of soybean oil for biodiesel production with different acyl acceptors, J. Mol. Catal. B: Enzym. 30 (2004) 125–9. [14] W. Du, Y. Xu and D. Liu (to Tsinghua University), Synthetic method of biodiesel from oils and fats, PCT Int. Publ. No. WO 2004/081158 (23 Sept. 2004). [15] E. Cernia, C. Palocci and S. Soro, The role of the reaction medium in lipasecatalyzed esterifications and transesterifications, Chem. Phys. Lipids 93 (1998) 157–68. [16] N.R. Kamini and H. Iefuji, Lipase catalyzed methanolysis of vegetable oils in aqueous medium by Chryptococcus spp. S-2, Process Biochem. 37 (2001) 405–10. [17] L.A. Nelson, T.A. Foglia and W.N. Marmer, Lipase-catalyzed production of biodiesel, J. Am. Oil Chem. Soc. 73 (1996) 1191–5. [18] V. Dossat, D. Combes and A. Marty, Continuous enzymatic transesterification of high oleic sunflower oil in a packed bed reactor: influence of the glycerol production, Enzyme Microb. Technol. 25 (1999) 194–200.

456

Biodiesel science and technology

[19] P.V. Lara and E.Y. Park, Potential application of waste activated bleaching earth on the production of fatty acid alkyl esters using Candida cylindracea lipase in organic solvent systems, Enzyme Microb. Technol. 34 (2004) 270–7. [20] A.M. Klibanov, Enzymes that work in organic solvents, ChemTech. 16 (1986) 354–9. [21] R.D. Abigor, P.O. Uadia, T.A. Foglia, M.J. Haas, K.C. Jones, E. Okpefa, J.U. Obibuzor and M.E. Bafor, Lipase-catalyzed production of biodiesel fuel from some Nigerian lauric oils, Biochem. Soc. Trans. 28 (2000) 979–81. [22] M. Vacek, M. Zarevúcka, Z. Wimmer, K. Stránský, M. Macková and K. Demnerová, Enzyme alcoholysis of blackcurrant oil, Biotechnol. Lett. 23 (2001) 27–32. [23] A.M. Klibanov, Enzymatic catalysis in anhydrous organic solvents, Trends Biochem. Sci. 14 (1986) 141–4. [24] G.V. Chowdary and S.G. Prapulla, The influence of water activity on the lipase catalyzed synthesis of butyl butyrate by transesterification, Process Biochem. 38 (2002) 393–7. [25] A.O. Triantafyllou, E. Wehtje, P. Adlercreutz and B. Mattiasson, Effects of sorbitol addition on the action of free and immobilized hydrolytic enzymes in organic media, Biotech. Bioengng. 45 (1995) 406–14. [26] S. Shah, S. Sharma and M.N. Gupta, Biodiesel preparation by lipase-catalyzed transesterification of Jatropha oil, Energy Fuels 8 (2004) 154–9. [27] M. Iso, B. Chen, M. Eguchi, T. Kudo and S. Shrestha, Production of biodiesel fuel from triglycerides and alcohol using immobilized lipase, J. Mol. Catal. B: Enzym. 16 (2001) 53–8. [28] K. Nakamura, Y.M. Chi, T. Yamada and T. Yano, Lipase activity and stability in supercritical carbon dioxide, Chem. Engng. Commun. 45 (1986) 207–12. [29] T. Adschiri, H. Akiya, L.C. Chin, K. Arai and K. Fujimoto, Lipase-catalyzed interesterification of triglyceride with supercritical carbon dioxide extraction, J. Chem. Engng. Jpn. 25 (1992) 104–5. [30] A. Marty, W. Chulalaksasanukul, J.-S. Condoret, R.M. Willemot and G. Durand, Comparison of lipase-catalysed esterification in supercritical carbon dioxide and in n-hexane, Biotechnol. Lett. 12 (1990) 11–16. [31] A. Marty and J.-S. Condoret, Enzymatic transesterifications in supercritical fluids, Meth. Biotechnol. 15 (2001) 587–602. [32] T.W. Randolph, H.W. Blanch and D.S. Clark, Biocatalysis in supercritical fluids, in Biocatalysis for Industry (J.S. Dordrick, ed.), Plenum Press, New York (1991), pp. 219–37. [33] J.C. Erickson, P. Schijns and C.L. Cooney, Effect of pressure on an enzymatic reaction in a supercritical fluid, AIChE J. 36 (1990) 299–301. [34] B. Al-Duri, R. Goddard and J. Bosley, Characterisation of a novel support for biocatalysis in supercritical carbon dioxide, J. Mol. Catal. B: Enzym. 11 (2001) 825–34. [35] S. Matsamura, H. Ebata, R. Kondo and K. Toshima, Organic solvent-free enzymatic transformation of poly (e-caprolactone) into repolymerizable oligomers in supercritical carbon dioxide, Macromol. Rapid Commun. 22 (2001) 1325–9. [36] H. Michor, R. Marr, T. Gamse, T. Schilling, E. Klingsbichel and H. Schwab, Enzymatic catalysis in supercritical carbon dioxide: comparison of different lipases and a novel esterase, Biotechnol. Lett. 18 (1996) 79–84. [37] A. Marty, D. Combes and J.-S. Condoret, Continuous reaction-separation process for enzymic esterification in supercritical carbon dioxide, Biotechnol. Bioengng. 43 (1994) 497–504.

Biocatalytic production of biodiesel

457

[38] H. Vija, A. Telling and V. Tougu, Lipase-catalysed esterification in supercritical carbon dioxide and in hexane, Biorg. Medic. Chem. Lett. 7(3) (1997) 259–62. [39] T. Mori, A. Kobayashi and Y. Okahata, Biocatalytic esterification in supercritical carbon dioxide using a liquid-coated lipase, Chem. Lett. 9 (1998) 921–2. [40] A. Marty, W. Chulalaksananukul, R.M. Willemot and J.-S. Condoret, Kinetics of lipase-catalyzed esterification in supercritical carbon dioxide, Biotechnol. Bioengng. 39 (1992) 273–80. [41] C. Vieville, Z. Mouloungui and A. Gaset, Esterification of oleic acid by methanol catalyzed by p-toluenesulfonic acid and the cation-exchange resins K2411 and K1481 in supercritical carbon dioxide, I&EC Res. 32(9) (1993) 2065–8. [42] S.-H. Yoon, O. Miyawaki, K.-H. Park and K. Nakamura, Transesterification between triolein and ethylbehenate by immobilized lipase in supercritical carbon dioxide, J. Ferment. Bioengng. 82 (1996) 334–40. [43] H. Gunnlaugsdottir, K. Wannerberger and B. Sivik, Alcoholysis and glyceride synthesis with immobilized lipase on controlled-pore glass of varying hydrophobicity in supercritical carbon dioxide, Enzyme Microb. Technol. 22 (1998) 360–7. [44] H. Gunnlaugsdottir, M. Järemo and B. Sivik, Process parameters influencing ethanolysis of cod liver oil in supercritical carbon dioxide, J. Supercrit. Fluids 12(1) (1998) 85–93. [45] M. Habulin, V. Krmelj and Ž. Knez, Synthesis of oleic acid esters catalyzed by immobilized lipase, J. Agric. Food Chem. 44 (1996) 338–42. [46] P. Pasta, G. Mazzola, G. Carrea and S. Riva, Subtilisin-catalyzed transesterification in supercritical carbon dioxide, Biotechnol. Lett. 11 (1989) 643–8. [47] M.A. Jackson and J.W. King, Methanolysis of seed oils in flowing supercritical carbon dioxide, J. Am. Oil Chem. Soc. 73 (1996) 353–6. [48] D.M. Ginosar and R.V. Fox (to Bechtel BWXT Idaho), Process for producing biodiesel, lubricants, and fuel and lubricant additives in a critical fluid medium, US Pat. 6,887,283 B1 (3 May 2005). [49] V. Dossat, D. Combes and A. Marty, Lipase-catalysed transesterification of high oleic sunflower oil, Enzyme Microb. Technol. 30 (2002) 90–4. [50] T. Dumont, D. Barth and M. Perrut, Continuous synthesis of ethyl myristate by enzymatic reaction in supercritical carbon dioxide, J. Supercrit. Fluids 6 (1993) 85–9. [51] T. Kajiuchi, Y. Hayakawa, Y. Okawa and K. Kou (to Nof Co.), Method for producing fatty acid ester using modified lipase, Jpn. Kokai Tokkyo Koho JP 2006/050954 (23 Feb. 2006). [52] C.F. Torres, H.S. Garcia, J.J. Ries and C.G. Hill Jr, Esterification of glycerol with conjugated linoleic acid and long-chain fatty acids from fish oil, J. Am. Oil Chem. Soc. 78 (2001) 1093–8. [53] C.F. Torres, F. Muniz, R.M. Blanco, C. Otero and C.G. Hill Jr., Catalytic transesterification of corn oil and tristearin using immobilized lipases from Thermomyces lanuginosa, J. Am. Oil Chem. Soc. 79 (2002) 775–81. [54] V. Seriburi and C.C. Akoh, Enzymatic interesterification of lard and high-oleic sunflower oil with Candida antarctica lipase to produce plastic fats, J. Am. Oil Chem. Soc. 75 (1998) 1339–45. [55] Z. Zainal and M.S.A. Yusoff, Enzymatic interesterification of palm stearin and palm kernel olein, J. Am. Oil Chem. Soc. 76 (1999) 1003–8. [56] F. Cho, J. deMax and O.B. Allen, Modification of hydrogenated canola oil/palm stearin/canola oil blends by continuous enzymatic interesterification, Elaies 6 (1992) 25–36.

458

Biodiesel science and technology

[57] F. Cho, J. deMan and O.B. Allen, Physical properties and composition of low trans canola/palm blends modified by continuous enzymatic interesterification, Elaies 6 (1992) 39–49. [58] P. Forssel, R. Kervinen, M. Lappi, P. Linko, T. Suortti and K. Poutanen, Effect of enzymatic interesterification on the melting point of tallow-rapeseed oil (LEAR) mixture, J. Am. Oil Chem. Soc. 69 (1992) 126–9. [59] T. Foglia, K. Petroso and S.H. Feairheller, Enzymatic interesterification of tallowsunflower oil mixtures, J. Am. Oil Chem. Soc. 70 (1993) 281–5. [60] A.H. Kittikun, P. Prasertsan and C. Sungpud, Continuous production of fatty acids from palm olein by immobilized lipase in a two-phase system, J. Am. Oil Chem. Soc. 77 (2000) 599–603. [61] M. Mittelbach, Lipase catalyzed alcoholysis of sunflower oil, J. Am. Oil Chem. Soc. 67 (1990) 168–70. [62] Y.Y. Linko, M. Lämsä, A. Huhtala and P. Linko, Lipase-catalyzed transesterification of rapeseed oil and 2-ethyl-1-hexanol, J. Am. Oil Chem. Soc. 71 (1994) 1411– 14. [63] D. Briand, E. Dubreucq and P. Galzy, Enzymatic fatty esters synthesis in aqueous medium with lipase from Candida parapsilosis (Ashford), Biotechnol. Lett. 16 (1994) 813–18. [64] M. Basri, A.C. Heng, C.N.A. Razak, W.M.Z. Wan Yunus, M. Ahmad, R.N.A. Rahman, K. Ampon and A.B. Salleh, Alcoholysis of palm oil mid-fraction by lipase from Rhizopus rhizopodiformis, J. Am. Oil Chem. Soc. 74 (1997) 113–16. [65] H. Gunnlaugsdottir and B. Sivik, Lipase-catalyzed alcoholysis with supercritical carbon dioxide extraction. 1: Influence of flow rate, J. Am. Oil Chem. Soc. 74 (1997) 1483–90. [66] T.A. Foglia, L.A. Nelson and W.N. Marmer (to US Secretary of Agriculture), Production of biodiesel, lubricants and fuel and lubricant additives, US Pat. 5,713,965 (3 Feb. 1998). [67] C. Syldatk, M. Reuss, A. Daniel and R. Otto, Verfahren zur biotechnischen Herstellung von Fettsäuremethylestern (‘Biodiesel’) auf Molkebasis, Germ. Offenl. DE 19,838,011 A1 (20 May 1999). [68] Y. Shimada, Y. Watanabe, A. Sugihara, Y. Tominaga, H. Fukuda and H. Noda (to Kansai Chemical Engineering Co.), Process for producing biodiesel fuel lower alcohol ester, PCT Int. Publ. No. WO 2000/012743 (9 Mar. 2000). [69] M. Tüter and H.A. Aksoy, Solvent-free glycerolysis of palm and palm kernel oils catalyzed by commercial 1,3-specific lipase from Humicola lanuginosa and composition of glycerolysis products, Biotechnol. Lett. 22 (2000) 31–4. [70] G. Steinke, R. Kirchhoff and K.D. Mukherjee, Lipase-catalyzed alcoholysis of crambe oil and camelina oil for preparation of long-chain esters, J. Am. Oil Chem. Soc. 77 (2000) 361–6. [71] H. Iefuji, N.R. Kamini, I. Fujii, T. Korosu and N. Okazaki (to Sakerui Sogo Kenkyusho), Method for producing biodiesel fuel (monoalkyl ester), Jpn. Kokai Tokkyo Koho JP 2002/233393 (A) (20 Aug. 2002). [72] S. Nandi, S. Gangopadhyay and S. Ghosh, Production of medium chain glycerides from coconut and palm kernel fatty acid distillates by lipase-catalyzed reactions, Enzyme Microb. Technol. 36 (2005) 725–8. [73] S. Kojima and E.Y. Park, Conversion of residual vegetable oil on waste bleaching earth to biodiesel fuel, Nendo Kagaku 44 (2005) 138–42. [74] M. Zong and H. Wu (to South China University of Science and Technology),

Biocatalytic production of biodiesel

[75] [76]

[77]

[78]

[79] [80]

[81]

[82]

[83]

[84] [85]

[86]

[87]

[88]

[89]

[90]

[91]

459

Biologically catalytic process of converting fat into ester to produce biological diesel oil, Chin. Pat. 1,453,332 (5 Nov. 2003). J. Cao, F. Lang and J. Li, Process for preparing biological diesel by rapeseed fermenting method, Chin. Pat. 1,583,959 (23 Feb. 2005). C.-L. Lin, B.-S. Fang, T.-L. Huang and C.-S. Wu, Production of biodiesel from soybean oil by lipase-catalyzed transesterification, Shiyou Jikan 41 (2005) 51–8. E. Uosukainen, M. Lämsä, Y.-Y. Linko, P. Linko and M. Leisola, Optimization of enzymatic transesterification of rapeseed oil ester response surface and principal component methodology, Enzyme Microb. Technol. 25 (1999) 236–43. L. Fernández, E. Rosenbaum and G. Pérez, Biocatalysis by immobilized lipases like an alternative technology to produce biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). S. Bloomer, P. Adlercreutz and B. Mattiasson, Facile synthesis of fatty acid esters in high yields, Enzyme Microb. Technol. 14 (1992) 546–52. S. Bloomer, P. Adlercreutz and B. Mattiasson, Kilogram-scale ester synthesis of acyl donor and use in lipase-catalyzed interesterifications, J. Am. Oil Chem. Soc. 69 (1992) 966–73. P. Langholz, P. Andersen, T. Forskov and W. Schmidtsdorff, Application of a specificity of Mucor miehei lipase to concentrate docosahexaenoic acid (DHA), J. Am. Oil Chem. Soc. 66 (1989) 1120–3. Y. Shimada, Y. Watanabe, A. Sugihara, T. Baba, T. Ooguri, S. Moriyama, T. Terai and Y. Tominaga, Ethyl esterification of docosahexaenoic acid in an organic solvent-free system with immobilized Candida antarctica lipase, J. Biosci. Bioengng. 92 (2001) 19–23. M.J. Haas and K.M. Scott, Combined nonenzymatic-enzymatic method for the synthesis of simple alkyl fatty acid esters by soapstock, J. Am. Oil Chem. Soc. 73 (1996) 1393–401. B. Selmi and D. Thomas, Immobilized lipase-catalyzed ethanolysis of sunflower oil in a solvent-free medium, J. Am. Oil Chem. Soc. 75 (1998) 691–5. Y. Watanabe, Y. Shimada, A. Sugihara and Y. Tominaga, Stepwise ethanolysis of tuna oil using immobilized Candida antarctica lipase, J. Biosci. Bioengng. 88 (1999) 622–6. W.-H. Wu, T.A. Foglia, W.N. Marmer and J.G. Phillips, Optimizing production of ethyl esters of grease using 95% ethanol by response surface methodology, J. Am. Oil Chem. Soc. 76 (1999) 517–21. Y. Watanabe, Y. Shimada, A. Sugihara and S. Tominaga, Enzymatic conversion of waste edible oil to biodiesel fuel in a fixed-bed bioreactor, J. Am. Oil Chem. Soc. 78 (2001) 703–7. K.-T. Lee, T.A. Foglia and K.-S. Chang, Production of alkyl ester as biodiesel from fractionated lard and restaurant grease, J. Am. Oil Chem. Soc. 79 (2002) 191–5. W.-T. Wu and J.-W. Chen, Verfahren zur Herstellung von Niedrigalkylfettsäureestern und insbesondere von Biodiesel, Germ. Offenl. DE 10,217,607 A1 (31 Oct. 2002). Ö. Köse, M. Tüter and H.A. Aksoy, Immobilized Candida antarctica lipasecatalyzed alcoholysis of cotton seed oil in a solvent-free medium, Bioresour. Technol. 83 (2002) 125–9. Y. Watanabe, Y. Shimada, A. Sugihara and Y. Tominaga, Conversion of degummed

460

[92]

[93]

[94]

[95] [96]

[97] [98] [99]

[100]

[101]

[102]

[103] [104] [105] [106]

[107] [108] [109]

Biodiesel science and technology soybean oil to biodiesel fuel with immobilized Candida antarctica lipase, J. Mol. Catal. B: Enzym. 17 (2002) 151–5. Y. Watanabe, Y. Shimada, T. Baba, N. Ohyagi, S. Moriyama, T. Terai, Y. Tominaga and A. Sugihara, Methyl esterification of waste fatty acids with immobilized Candida antarctica lipase, J. Oleo Sci. 51 (2002) 655–61. K. Bélafi-Bakó, F. Kovács, L. Gubicza and J. Hancsók, Enzymatic biodiesel production from sunflower oil by Candida antarctica lipase in a solvent-free system, Biocat. Biotransf. 20 (2002) 437–9. B. Yang, X. Wang, Y. Wang, Q. Li and R. Yao (to Huanan University of Technology), Method for producing diglyceride, Chin. Pat. 1,438,308 (27 Aug. 2003). Z. Cai, G. Wu, X. Lin, C. Zhu and L. Liu, Synthesis of biodiesel fuel catalyzed by immobilized Candida antarctica lipase, Zhongguo Youzhi 29 (2004) 29–32. W. Du, Y.-Y. Xu, J. Zeng and D.-H. Liu, Novozym 435-catalysed transesterification of crude soya bean oils for biodiesel production in a solvent-free medium, Biotechnol. Appl. Biochem. 40 (2004) 187–90. Y. Yesiloğlu, Immobilized lipase-catalyzed ethanolysis of sunflower oil, J. Am. Oil Chem. Soc. 81 (2004) 157–60. Y. Yesiloğlu and I. Kilic, Lipase-catalyzed esterification of glycerol and oleic acid, J. Am. Oil Chem. Soc. 81 (2004) 281–4. L. Yu, M. Zhu, Y. Xue, B. Jin and P. Zhou (to Huazhong University of Science and Technology), Method for producing biological diesel using lipase, Chin. Pat. 1,640,991 (20 July 2005). Y. Watanabe, P. Pinsirodom, T. Nagao, T. Kobayashi, Y. Nishida, Y. Takagi and Y. Shimada, Production of FAME from acid oil model using immobilized Candida antarctica lipase, J. Am. Oil Chem. Soc. 82 (2005) 825–31. Y. Watanabe, P. Pinsirodom, T. Nagao, A. Yamauchi, T. Kobayashi, Y. Nishida, T. Takagi and Y. Shimada, Conversion of acid oil by-produced in vegetable oil refining to biodiesel fuel by immobilized Candida antarctica lipase, J. Mol. Catal. B: Enzym. 44 (2007) 99–105. A. Salis, M. Pinna, M. Monduzzi and V. Solinas, Biodiesel production from triolein and short chain alcohols through biocatalysis, J. Biotechnol. 119 (2005) 291–9. A.C. Oliveira and M.F. Rosa, Enzymatic transesterification of sunflower oil in an aqueous-oil biphasic system, J. Am. Oil Chem. Soc. 83 (2006) 21–5. P.D. Desai, A.M. Dave and S. Devi, Alcoholysis of Salicornia oil using free and covalently bound lipase onto chitosan beads, Food Chem. 95 (2006) 193–9. H. Fukuda and H. Noda (to Kansai Chemical Engineering Co., Ltd), Process for producing fatty acid lower alcohol ester, US Pat. 6,982,155 B1 (3 Jan. 2006). I. Jachmanián, M. Dobroyán, B. Irigaray, J.P. Veira, I. Vieitez, M. Moltini, N. Segura and M.A. Grompone, Effect of substrate composition in the efficiency of a continuous lipase catalyzed alcoholysis of sunflower oil, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). K. Rezaei and F. Temelli, Lipase-catalyzed hydrolysis of canola oil in supercritical carbon dioxide, J. Am. Oil Chem. Soc. 77 (2000) 903–9. H. Fukuda, A. Kondo and H. Noda, Review. Biodiesel fuel production by transesterification of oils, J. Biosci. Bioengng. 92 (2001) 405–16. R. Staubmann, I. Ncube, G.M. Gübitz, W. Steiner and J.S. Read, Esterase and lipase activity in Jatropha curcas L. seeds, J. Biotechnol. 75 (1999) 117–26.

Biocatalytic production of biodiesel

461

[110] G. Steinke, S. Schönwiese and K.D. Mukherjee, Alkali-catalyzed alcoholysis of crambe oil and camelina oil for the preparation of long-chain esters, J. Am. Oil Chem. Soc. 77 (2000) 367–71. [111] H. Felix, Permeabilized cells, Anal. Biochem. 120 (1982) 211–34. [112] J. Obbard, S. Balasubramanian, M. Montefrio and T.T. Doan, Screening of tropical microalgae for cellular lipids for use as a biodiesel feedstock, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [113] H. Fukuda, Production of biodiesel fuel as clean energy, Nippon Nogei Kagaku Kaishi 77 (2003) 23–5. [114] K. Ban, M. Kaieda, T. Matsumoto, A. Kondo and H. Fukuda, Whole cell biocatalyst for biodiesel fuel production utilizing Rhizopus oryzae cells immobilized within biomass support particles, Biochem. Engng. J. 8 (2001) 39–43. [115] S. Hama, H. Yamaji, M. Kaieda, M. Oda, A. Kondo and H. Fukuda, Effect of fatty acid membrane composition on whole-cell biocatalysts for biodiesel-fuel production, Biochem. Engng. J. 21 (2004) 155–60. [116] T. Matsumoto, S. Takahashi, M. Kaieda, M. Ueda, A. Tanaka, H. Fukuda and A. Kondo, Yeast whole-cell biocatalyst constructed by intracellular overproduction of Rhizopus oryzae lipase is applicable to biodiesel fuel production, Appl. Microbiol. Biotechnol. 57 (2001) 515–20. [117] H. Fukuda, A. Kondo and T. Matsumoto (to BioEnergy K.K.), Method for producing optically active substance by using enzyme presented on cell surface layer, Jpn. Kokai Tokkyo Koho 2004/049014 (19 Feb. 2004). [118] S. Al-Zuhair, Production of biodiesel: possibilities and challenges, Biofuels Bioprod. Biorefin. 1 (2007) 57–66. [119] C. Scholz and R.A. Gross, Biopolyesters and biocatalysis introduction, in Polymers from Renewable Resources: Biopolyesters and Biocatalysis, ACS Symp. Ser. 764 (2000), pp. 1–11.

11

Industrial process technology for biodiesel production

Abstract: This chapter describes the main characteristics of various biodiesel process technologies (batch, semi-continuous, continuous flow; base- and acid-catalysed; plant size from miniplants at community level to large-scale plants; plant modularity; feedstock quality control, etc.) in terms of critical success factors. Plant technology is discussed in relation to feedstock supply. Factors affecting biodiesel manufacturing technology are outlined as well as minimum conditions for economically viable biodiesel plants. Several proprietary transesterification processing technologies are described. Selected biodiesel producers worldwide (Europe, USA, SouthEast Asia, South America), ranging from community-based production units to highly integrated biodiesel plants, are considered. Biodiesel blending techniques are evaluated. Key words: Biodiesel process options, industrial biodiesel process technology, plant design, plant sizing, blending techniques.

11.1

Introduction

Biodiesel plants are made to process different feedstocks. Table 11.1 lists the critical success factors for a biodiesel feedstock. Biomass facilities require an abundant supply of biomass to serve economies of scale. Some plants are Table 11.1 Critical success factors for a biodiesel feedstock   ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

462

Realistic assessment of feedstock volumes   Level of supply security in feedstocks sourcing (volume stabilisation) and purchasing cost (long-term contracts) Related logistics of acquiring targeted feedstocks (location of biomass harvesting) Ability to choose most economic feedstock options Production planning of source-related, seasonal or other fluctuations in supply Ready processing (no complex pre-processing or requirement for yet-to-be developed technology) Flexibility in processing various feedstock sources Process technology overcoming changes in quality and consistency of targeted feedstocks Flexibility in storage facility systems Sound economic analysis

Industrial process technology for biodiesel production

463

designed specifically for a refined vegetable oil or used cooking oil, whereas multi-feedstock plants combine different process technologies to deal with different input. Feedstock dictates the location of a production unit. Biodiesel plants that process a refined vegetable oil are generally located near a crushing facility, which produces seed oil and meal. Brown grease-based operations are preferably located near wastewater treatment plants. Crop-based production facilities close to local crop resources do not need massive capacities to achieve viable economies of scale. Typically, the small-scale biodiesel producer Piedmont Biofuels Industrial (Pittsboro, NC) collects its multi-feedstock (used cooking oil – UCO, tallow – TLW, waste vegetable oils-WVO) for its 4 MMgy batch facility within 100 miles of the plant and distributes fuel into that same 100 mile region. Plants next to crushing facilities help lower transportation costs. Partnership with feedstock suppliers is critical to producer survival. The most successful plants have some control over feedstock supply (own production, active involvement with farmer cooperatives, oil trading companies or rendering companies). Developing plants at the community level, using local, recycled materials, and distributing the biodiesel back into the same community should result in a more sustainable and price stable fuel. Collecting biomass from afar quickly changes the economics of a project. Plants producing more than 50 kt/yr require 10% of the cultivated area within 40 km of the site for oilseed crop growth, or transport of oilseed from beyond the region. For plants dependent on external sources, logistics is extremely important. Those biodiesel plants should preferably have existing sea, waterway, rail or road access to receive feedstock in large quantities at relatively low transport costs. This makes them independent from local feedstock sources. As a case in point, the French oilseed industry recently expanded to Le Meriot; the location was dictated by its proximity to three major rapeseed producing regions (Eastern France, Burgundy and the Parisian Basin) and its location on the Seine river. Other important biodiesel activities are located in the Texas Gulf area and along the Paraná river. Construction of recent large biodiesel plants in sea ports (e.g. Amsterdam, Antwerp, Rotterdam, Emden, Wilhelmshaven, St. Nazaire, Sète, Kingstonupon-Hull, Livorno, Bilbao, Callao, Kakinada (Andhra Pradesh), Kuantan, Rosario, Wilmington (NC), Port Neches (TX), Houston (TX), Gulfport (MS), Galveston (TX), Miami (FL), and many others) relies on shipping feedstock and biodiesel. Imperium Renewables recently opened a US$75 million, 100 MMgy biodiesel plant in Grays Harbor, WA, using imported canola oil from Canada (where canola is grown at lower cost than in the US). The operation will benefit from the US federal tax credit for blenders. Biodiesel plants should preferably also be situated close to a local mineral oil refinery (e.g. Erg, Priolo) and linked by pipeline to facilitate blending. Ideally, biodiesel could be handled similarly to conventional diesel fuels.

464

Biodiesel science and technology

However, at present the product is primarily being distributed using trucks because of integrity concerns about pipeline shipments. B5 is moved using a 550-mile pipeline in Southeast USA. Different infrastructure is required for B20 on higher blends. Standard modular biodiesel production systems are typically 4 kt, 8 kt, 20 kt and 100 kt/yr. Most current biodiesel plants range from small (200–1000 kg/day) to medium-large (10–200 kt/yr, even 500 kt/yr), but on the whole the average size of biodiesel production units is increasing. EU average plant size (2007) is about 40 kt/yr. Figure 11.1 shows the development of Brazil’s plant size distribution from 51 plants in 2007 (total and average capacities of 2058 kt/yr and 40.3 kt/yr, respectively) to 115 production plants in the near future (total and average capacities of 5590 kt/yr and 48.6 kt/yr, respectively) [1]. Similarly, the 2007 average US plant size (based on 165 plants with total capacity of 1.85 Bgy) is 11.2 MMgy (or 37.0 kt/ yr), whereas the average size of plants under construction and expansion (reportedly 84 plants with total capacity of 1.38 Bgy) is 16.3 MMgy (or 53.8 kt/yr) [2]. Production plants range in size from 50 000 gpy to over 100 MMgy (330 kt/yr). However, the number of plants under construction in the US had decreased rapidly by the end of 2008 (to 12 by 24 Sept. 2008). The slowdown in new plant construction has determined an all-time slow down 45 2007 Tomorrow

40 35

Number of plants

30 25 20 15 10 5 0

10

50

100 Plant size (kt/yr)

11.1 Biodiesel in Brazil (after ref. [1]).

150

> 150

Industrial process technology for biodiesel production

465

for the biodiesel industry. In all likelihood, future plants might be smaller (below 10 MMgy) in order to take avantage of niche feedstocks. (For US plant updates, see the monthly Biodiesel Magazine.) In 2008 only biodiesel projects with access to lower-cost feedstocks are financeable. Since manufacturing biodiesel is basically relatively simple, biodiesel can be made on a small scale. Small plants (2–5 kt/yr) are operated with no more than two operators. Small-scale biodiesel plants of 1–3 MMgy (4–10 kt/yr) are suitable in regional markets; 0.5–1 MMgy units are viable for communities with access to large quantities of vegetable oil. The key is not technology but rather the availability of feedstock. Generally, smaller biodiesel ‘brewing’ operations are not competitive with larger operations, although portable miniplants with a production volume of 0.05–1 kt/yr (mostly RCObased) are claimed to be economically viable [3]. In PCT Int. Publ. No. WO 2003/076558 to Dracowo [3], Adler describes very small-scale continuous production (0.05–1 kt/yr) of biodiesel in a microreactor unit at 338 K for local energy supply using freshly pressed oils. Community-scale biodiesel production at a plant scale of 0.5 MMgy (1.7 kt/yr) is economically viable in British Columbia if regional sources of low-cost feedstocks are combined with high-value fuel markets, chiefly in the transportation sector [4]. Cost-effective small community-scale biodiesel favours access to finished fuel in isolated rural areas. Africa, Asia and Brazil will likely see numerous small-scale biodiesel plants. Small-scale production units seem to be more profitable for recycled frying oil collection (‘McDiesel’ production). The US Navy is testing a mobile processing unit in California that turns used cooking oil into biodiesel. The challenge for small-scale facilities is quality testing for each batch of fuel. Larger scale biodiesel plants (from 5 to over 50 MMgy) are more efficient (quality, product marketing) up to a certain size where the logistics for raw material acquisition becomes more expensive. As large facilities need to always operate at full capacity, security of supply is crucial. In March 2008 the US biodiesel industry did operate at only 45% of nameplate capacity [5]. Market analysts consider optimum biodiesel plant size as 12–25 MMgy (or 40–82.5 kt/yr). Table 11.2 shows the main differences between various biodiesel production technologies. Feasibility studies for the implementation of a biodiesel production plant based on transesterification of triglycerides require an analysis of the technical aspects, such as an evaluation of the technology, biodiesel standards/quality (laboratory design, personnel training), supply chain, operating plant issues (including start-up), execution alternatives, as well as economic aspects. Process technology selection needs to consider the nature of the transesterification process (processing mode, nature of catalyst, reaction conditions, yield levels) and equipment layouts. Evaluation of the supply chain aims at selecting the raw materials (nature

466

Biodiesel science and technology Table 11.2 Differences between biodiesel production technologies ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Feedstock technology: required quality of raw materials Mass and energy balances Quantity and quality of by-products and residues Modularity of equipment Operational aspects of the process Process dynamics and stability Process control Flexibility Maintenance Product quality monitoring technology Costs Guarantees (technology provider)  

of the oilseeds – refined or unrefined, catalyst and alcohol) and considers the by-products (glycerol, waste water, salts). The evaluation of execution alternatives comprises a site location study, reliability of feedstock sourcing (eventually oilseed crushing facilities) and biodiesel blending/distribution, as well as plant components (reactor type, product purification section) and other factors (local regulations, permits, compliances, external impacts). The financial plan encompasses market considerations (market value, market distance/transportation/logistics) and financial aspects (production costs, plant operating costs, subsidies, taxation). A feasibility study for biodiesel development in British Columbia is exemplary [4]. Economically viable biodiesel plants distinguish themselves in terms of: ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

technology; feedstock control (through captive supply, own crushing or rendering facilities, strong grower alignment, reliable long-term supply contracts and quality); sustainable feedstock flexibility (MFT); advantageous geographic location; transportation flexibility; economy of scale; cost-effective operation (low labour requirement and operating costs with efficiency of process heating and design); marketing of the glycerol by-product; and sustainable incentive structure.

Critical strategic factors that will drive success or failure of a commercial biodiesel project comprise the ability to: ∑ ∑

balance feedstock supplies, processing technology, and market penetration in a reliable and efficient integrated system; form stable strategic alliances with feedstock suppliers, distributors, end users, and other stakeholders;

Industrial process technology for biodiesel production

∑ ∑

467

anticipate and deal effectively with competitive pressure; and generate a business plan that will allow a project to attract financing, and maintain its financial health.

11.2

Biodiesel plant design and engineering

Biodiesel is manufactured by the transesterification reaction of (un)refined oils and fats. Esterification technology is relatively mature (see Chapter 7). The overall process essentially includes transesterification, recovery of unreacted methanol, purification of methyl esters from catalyst and separation of glycerol as a co-product from saponified products (see Fig. 11.2). Typical processes consist of several reactors (for esterification, transesterification and neutralisation) and various columns (for alcohol distillation, washing, fatty acid ester distillation and glycerol purification) (see Fig. 11.3). The criteria for best practice biodiesel plant design are process technology selection and feedstock supply, apart from other equally important considerations (marketing strategy, site selection and financing). Plant technology defines what the feedstock and end-product cost will be. Technology drives the feedstock and feedstock drives technology. Each plant’s design should be tailored to the region and the feedstocks that are available in that area. For example, plant design in Georgia should consider processing yellow grease, poultry and catfish rather than canola. Table 11.3 Oil and fats

Pre-treatment Methanol

Methanol + Catalyst

Esterification

Transesterification

Biodiesel washing and drying

Chemicals

Glycerol treatment

Glycerol treatment

Biodiesel

Crude glycerol 80–85%

Glycerol (Pharma grade, 99.5%)

11.2 Block diagram for biodiesel production by esterification/ transesterification of triglycerides.

468

Biodiesel science and technology

Table 11.3 Factors affecting biodiesel manufacturing technology   ∑ ∑ ∑ ∑ ∑ ∑

Feedstock type, volume, quality and delivery schedule   (Inter)national biodiesel standards (impacting on pre-processing requirements and quality control) By-product processing options for methanol recovery, glycerol, fertiliser and water Monitoring technology Anticipated plant growth (modularity of equipment) Selected technology provider

lists some factors affecting biodiesel manufacturing technology. Important process technological considerations include: ∑ reaction yield; ∑ flexibility in handling multi-feedstock oils and fats, e.g. high FFA; ∑ flexible process and multi-feedstock recipes control; and ∑ reliable quality assurance (EN 14214/ASTM D 6751). Flexibility in feedstocks, intelligent plant design and established distribution channels are essential elements to keeping biodiesel moving forward as a fuel source. Planning for multiple feedstock capabilities is a minimum requirement for new facilities. A challenge for biodiesel is plant scale. Plant sizing depends on a number of region-specific parameters. Biomass collection makes the size of petrodiesel plants generally unattainable (consider, however, the prospected 800 kt/yr palm oil-based hydrodiesel plants). Two biodiesel plant sizes that are able to ride out difficult market fluctuations are small regional operations and large facilities. Smaller operations (1–9 MMgy) are a common US plant size (some 40%); larger operations (> 10 MMgy) make up about 30% of US biodiesel producers [6] and are favoured in Argentina. Small plants (typically 3 MMgy) with limited running costs typically have access to local feedstock. Large producers have the size to negotiate on all levels of operation including long-term feedstock and offtake agreements. They are usually well situated and have access to rail, truck and port facilities which allows for flexibility in feedstock procurement and offtake transport. A compact modular plant design that uses proven techniques for process optimisation and energy integration can improve biodiesel plant economics and speed up the construction or expansion process [7]. At present, markets are transiting to larger plants and second-generation technologies. Different operating plant alternatives can be applied to biodiesel production by vegetable oil transesterification. This is not surprising given variations in plant size (from home-built processors to mobile units, small agroplants and very large industrial oleochemical/biodiesel plants, up to 500 kt/yr), design (batch, semi-batch or continuous flow), operating conditions (from low T, p – typically < 373 K and 0.1–1 MPa – to high T, p – typically 523 K and

Industrial process technology for biodiesel production

469

9 MPa), reactor type (tubular, flow, plug-flow, standing column, stirring reactor, microreactor, etc.), single or multistep (with intermediate (by-) product removal), feedstock characteristics (refined vs. unrefined), nature of the catalyst (homogeneous vs. heterogeneous, base vs. acid) and downstream operations. For engineering simplicity it is desirable to design processes that run effectively at ambient or near-ambient temperatures and atmospheric pressure. Most biodiesel plants use low temperatures and near-atmospheric pressure to reduce equipment costs. Larger plants (> 4 kt/yr) mostly use continuous-flow processes involving continuous stirred-tank reactors (CSTR) or plug-flow reactors; smaller plants often use batch reactors. As to mixing, CSTR is preferred above high-shear mixers (with low residence times), which generally operate at higher cost. Alternative reactor design includes controlled cavitation (SPR), spinning tube-in-tube (STT) technology and a Microwave Accelerated Reaction System (MARS). The ShockWave PowerTM reactor (SPR) technology (controlled cavitation with rotor speeds up to 170 mph) drives the transesterification reaction in batch, continuous and semi-continuous biodiesel production systems towards completion in seconds (see also Section 7.3.2, pp. 303–4). Production rates of batch reaction processes are more than doubled and as the reaction occurs instantaneously, true continuous processing can then be achieved. The cavitation technology allows conversion of varied feedstocks such as crude degummed soy or chicken fat. Memphis Biofuels LLC (Memphis, TN) is using ShockWave PowerTM reactors in a 50 MMgy (continuous) capacity facility. Commercial-scale spinning tube-in-tube (STT) technology, based on Couette flow dynamics, is being implemented in a plant in Wilmington, NC (see Section 7.3.2, pp. 303–4). A MARS can be used for biodiesel production in batch (1 min at 323 K) and with a 4 L reaction vessel for continuous-flow preparation in small production units (0.8 MMgy or 3 kt/yr). Various other process innovations have been investigated including catalytic reactive distillation [8, 9], continuous-flow centrifugation [10], oscillatory flow reactors [11] and membrane reactions [11a]. The Yellowdiesel catalytic distillation process for making biodiesel and > 99.9% pure glycerol from high FFA oils (cooking oils and low-grade grease) integrates the transesterification reaction over a solid-acid catalyst and separation in one step using a reactive distillation column. This process intensifies mass transfer, allows in-situ energy integration, reduces equipment costs, and simplifies process flow and operation. A 2.5 kt/yr pilot plant based on this process, built by Fertibom, will come on stream in Rio de Janeiro in 2009. Although the standard methodology for producing biodiesel by transesterification offers many processing options, the ideal technology has not yet been established. The main technical thrust is transiting the traditional batch technology to a continuous process in larger facilities. Although there are many biodiesel plant manufacturers there are no plant manufacturing standards to follow.

470

Dryer

Biodiesel science and technology

Finished biodiesel

Methanol

Oilseeds

Processing

Oil

Oilseed meal

Catalyst

Reactor

Separator

Methyl esters

Methanol removal

Glycerol (50%)

Neutralisation and washing

Acid Water

Wash water

Acid Free fatty acids

Acidulation and separation

Crude glycerol (85%)

Methanol removal

Methanol/water rectification

Methanol storage

Water

11.3 Process flowsheet for biodiesel production.

Industrial process technology for biodiesel production

471

Figure 11.3 shows a schematic of typical process steps involved in biodiesel production [12]. Preparation of the raw material needs to respect certain degrees of humidity and acidity, and may consist in a neutralisation process, washing and/or pre-treatment. Any plant with more than 1% FFA in its feedstock needs to have a pre-treatment system. In the classical, commercial, alkalicatalysed transesterification procedure the reaction mixture (oil, methanol and catalyst) is then allowed to react (from min. to h) in a stirred reaction at atmospheric pressure, at the reaction temperature (typically 333  K). As transesterification is an equilibrium reaction, for high conversion the simple procedure is usually carried out with great excess of alcohol and high alkaline catalyst loadings, which impair downstream operations (separation, purification) and economicity. Use of smaller amounts of alcohol and catalyst requires a multi-stage process, either discontinuous [13] or continuous [14, 15]. In a two-stage process about 80% of alcohol and catalyst are added to the oil in a first reactor. After glycerol removal the reaction stream is then allowed to enter a second CSTR to which the remaining 20% of alcohol and catalyst are added. In this way complete reaction is achieved whereas potentially less alcohol is used than in single-step processing. The effluent stream exiting from the reactor contains methyl esters, glycerol, methanol, unconverted oil, catalyst residues and water. The final reaction mixture consists of two phases. Separation of glycerol from FAME generally occurs rapidly due to their low mutual solubility: gravitational phase separation is usually accomplished with either a settling tank or a centrifuge with alkyl esters (containing excess alcohol and impurities) as top phase and crude glycerol (impregnated by excess alcohol, water and raw material impurities) as bottom phase. Excess methanol is usually not removed from the reaction stream until after the glycerol and methyl esters are separated in view of concern about reversing the transesterification reaction. Water may be added to the reaction mixture after the transesterification is complete to improve the glycerol separation. In catalyst-free processes [16–18] the water washing step is eliminated. The ideal process would involve a continuous-flow reaction that does not deactivate or consume the catalyst and that further minimises or eliminates the need for multitudinous downstream separation and purification steps. High-efficiency phase separation is critical [18a]. Purity of the biodiesel product is affected by the feedstock quality, reaction conditions, glycerol separation, water washings, methanol stripping, particulate and/or adsorbent filtration and distillation (optional). After separation from the glycerol, the methyl esters pass a neutralisation step and a methanol stripper (vacuum flashing or falling film evaporator) before water washing. Acid is then added to the biodiesel to neutralise any residual catalyst and to split any soaps formed. Reaction of soaps with the acid forms water soluble salts and free fatty acids. While the salts will be removed during the water washing step, the free fatty acids will remain in the biodiesel.

472

Biodiesel science and technology

A key step in producing high-quality biodiesel is washing to remove impurities such as excess caustic catalyst, methanol, soaps and free glycerol. Wet washing uses water as a solvent to carry away the impurities, leaving the pure biodiesel behind. Neutralisation before washing minimises the amount of water required and reduces emulsion formation. When using KOH as the reaction catalyst and H3PO4 for neutralisation the salt formed is potassium phosphate, which finds application as a fertiliser. Water washing, which is very effective and makes most sense when using a good feedstock and for removal of all methanol, has been the de facto standard for quite some time. After the wash process, any remaining water is removed from the biodiesel by vacuum flashing. In the alternative (new) dry-wash biodiesel technology, an adsorbent is added that attracts and combines with soluble impurities (soaps, free and bound glycerol, and other polar molecules), separating them from the biodiesel. Dry washing can be expensive (up to 10 cents a gallon). Some systems use ion-exchange resins as the adsorbent. Amberlite™ BD10 Dry™ (Rohm & Haas) dry polymer biodiesel purification technology eliminates water washing from the process [19]. Crude biodiesel is purified from residual catalyst, soap and glycerol traces by passing it through a fixed-bed column of the specialty functionalised copolymer resin at the end of the process. The innovative technology is simple and cost-effective and maximises process yield for biodiesel made from any feedstock. Amberlite™ BD10 Dry™ resin can be integrated into any existing biodiesel plant. Ion-exchange technology is less suitable for large-capacity plants. Adsorbent filtration with Magnesol® D-Sol (Dallas Group of America, Inc.), a magnesium silicate rich in acidic and basic adsorption sites, is more effective in removal of contaminants (soaps, and free and bound glycerol) from raw biodiesel (contaminated FAME) than the traditional water washing processes [20, 21]. The benefits of Magnesol® include no water effluent stream, no emulsification, improved OSI, minimal yield loss, minimal capital expenditure, continuous processing and more rapid purification processing. The economics of the overall process is improved. An alternative to Magnesol® is MaxfloTM Advanced Filter Aids. Most recently, producers are changing from wet to dry washing for two reasons: speed and fuel quality. The glycerol stream leaving the separator and consisting of about 50% glycerol contains excess methanol, catalyst and soap. Glycerol refinement is usually carried out by first adding acid to split soap into free fatty acids and salts. While the salts remain in the glycerol, the free fatty acids – which are insoluble in glycerol – are removed as a top layer and may eventually be esterified and returned to the transesterification stream [22]. After acidulation and separation of the free fatty acids, methanol in glycerol is removed by vacuum flashing or evaporation. The resulting crude glycerol obtains a purity of about 85%. In a further separate glycerol refining process

Industrial process technology for biodiesel production

473

using vacuum distillation or an ion-exchange process finally a purity of up to 99.7% (pharmaceutical glycerol) can be obtained. Small-scale glycerol purification is not seen as economically viable. Methanol separated from the product streams has collected water that has entered the process, which needs to be removed in a distillation column before the methanol can be recycled to the process. In case of ethyl alcohol, dehydration is more complicated in view of azeotropy. In an acid-catalysed process using a high FFA feedstock two transesterification reactors operating in series are required to deal with the high molar ratio (100 : 1) of methanol to oil. Neutralisation of the acid catalyst follows methanol distillation to reduce corrosion in the downstream process units. The material of construction for the transesterification and neutralisation reactors and the methanol distillation column are stainless steel when sulphuric acid is used as a catalyst. Many proposed methods for the production of fatty acid esters suffer from incomplete conversion, long reaction time, need for pressurised reactors, and complex after-treatment. Much of the process complexity originates from contaminants in the feedstock, such as water and free fatty acids, or impurities in the final product, such as methanol, free glycerol and soap. Generally speaking, there are three basic ways for the production of methyl esters from oils and fats: ∑ ∑

base-catalysed transesterification of the oil (TGs) with methanol; acid-catalysed esterification of the free fatty acids (FFAs) with methanol; and ∑ conversion of the oil to FFA and then to methyl esters with acid catalysts.

For many decades, the patent literature has proposed (trans)esterification process technology. Technology providers are mentioned in Section 11.3. Tools are needed to evaluate and compare different biodiesel process options, process parameters and feedstocks. Complete understanding of biodiesel production requires a process model. Process modelling is utilised extensively by the chemical process industries for detailed design and feasibility evaluation of production plants. Various process engineering principles, such as mass and energy balances, can be utilised to collect and organise the production data by analysing the biodiesel production process in terms of the various inputs, outputs, and their composition at each process step. Such information is, in turn, needed for quantifying utility requirements and for sizing equipment. Performing mass and energy balance analyses of a full process are key steps towards calculating cost data for performing economic feasibility studies of biodiesel production from various feedstocks. In process modelling of conventional homogeneous base-catalysed (NaOCH3) two-stage continuous biodiesel production using stirred-tank reactors (CSTRs) and various crude

474

Biodiesel science and technology

vegetable oil feedstocks, the process was broken down into three main sections: crude oil degumming and refining, transesterification and ester washing, and methanol recovery and glycerol refining [23]. User-specified parameters consisted in transesterification efficiency (typically > 98%), nature of crude oil, crude oil throughput (> 100 kg/h) and ROH/VO molar ratio (typically 6 : 1). The process was modelled as 27 units with 51 flows and 18 components. A facility’s sustainability index depends on feedstock use, energy inputs for processing and methanol (derived for natural gas). Table 11.4 shows a 1998 comparison of production costs of six operating biodiesel plants [24]. As expected, operating costs decrease with used capacity. The table also shows cost differences between various technologies. Production costs represent only a minor part of the total cost of biodiesel, as the main part (almost 85%) is on account of the cost of the raw materials cost.

11.2.1 Base-catalysed biodiesel processing In conventional industrial biodiesel processes, methanol transesterification of vegetable oils is currently mostly achieved using a homogeneous catalyst system operated in either batch or continuous mode. The catalyst is often either NaOH or NaOCH3, with the former being preferred because of its lower cost. Base-catalysed processes show procedural differences arising from the type of lipid feedstock employed and the pre-treatment applied. In addition, they may differ in operational parameters, such as the use of co-solvents, reagents, temperature, pressure, batch or continuous processing, etc. Table 8.6 shows typical reaction conditions for (homogeneous) base-catalysed transesterification processes in biodiesel synthesis. Feedstock requirements are high as (expensive) refined or pre-treated oils are required (FFA content < 0.5 wt%). Biodiesel plants generally refine crude oils themselves [25], see also Section 3.6.5. Figure 11.4 depicts a simplified block flow diagram for a typical biodiesel production process by alkaline transesterification. Sodium is recovered after Table 11.4 Comparison of production costs of various operating biodiesel plants (after ref. [24])   Plant

A

B

C

D

E

F

Process Capacity (kt/yr) Oil qualitya Glycerol (%) Total operating   costs (DM/t)b

Batch 2.0 r, d 60 575

Batch 15.0 r, d 80, 99.5 392

Batch 75.0 r, d 90 152

Continuous 8.0 c, r 80 187

Continuous 125.0 r, d 92 174

Continuous 80.0 c, r 80, 99.7 128

a

c, crude; d, degummed; r, refined. 100 DM/t ª 0.20 US$/gal (1998).

b

MeOH NaOH

Catalyst preparation

Water washing or H3PO4

vegetable oil

Transesterification 333 K 0.14–0.4 MPa

Catalyst neutralisation

H3PO4

Fatty phase

Phosphates

Methanol recycle

Catalyst neutralisation

Separator

Separator

Filtration and water washing

Glycerol/alcohol phase Vacuum distillation 301 K, 0.02 MPa

Aqueous phase

Vacuum distillation 468–538 K, 0.04–0.05 MPa

Biodiesel (99.6%)

Oil waste

Vacuum distillation 329 K, 0.04 MPa

MeOH and water Glycerol (92%)

Aqueous phase

475

11.4 Simplified block flow diagram for a typical base-catalysed process for the production of biodiesel from refined vegetable oil (after ref. [26]).

Industrial process technology for biodiesel production

Ester phase Refined

Phosphates

476

Biodiesel science and technology

the transesterification reaction in the glycerol phase as sodium glycerate. An acidic neutralisation step is required to convert sodium glycerate to glycerol. Glycerol is obtained as a salt-containing aqueous solution. Depending on the process, the final glycerol purity is about 85%. When NaOH is used as a catalyst, side reactions forming sodium soaps generally occur. This type of reaction is also observed when sodium methylate is employed and traces of water are present. Sodium soaps are soluble in the glycerol phase and must be isolated after neutralisation by decanting the fatty acid product. The loss of esters converted to fatty acids can exceed 1% of the biodiesel production. In addition, waste salt streams require disposal in an ecologically friendly manner. In Eur. Pat. Appl. EP 0,708,813 A1 Mittelbach and Koncar [27] disclose a high yield of fatty acid esters by acid-catalysed post-transesterification of the fatty acids, fatty acid salts and/or other fatty acid compounds contained in and separated from the glycerol phase. PCT Int. Publ. No. WO 99/26913 assigned to Energea Handels GmbH [28] describes a variable pressure process (from up to 20 MPa to reduced pressure during processing) composed of base-catalysed transesterification under conditions of powerful dynamic turbulence (as created in a static mixer in a reactor filled with mono- or polydisperse beads, by cavitation emulgation or by means of ultrasounds). Reaction times of 20 sec at 313–343 K are claimed and processing of used cooking oils is possible. Phase separation is achieved either by vacuum distillation or molecular sieve filtration (see Fig. 11.5). The cost of biodiesel can be further reduced through the use of a heterogeneous catalyst, instead of a homogeneous one, providing for higherquality esters and glycerol, which are more easily separated, while there is no need for further expensive refining operations [29].

11.2.2 Acid-catalysed biodiesel processing Acid-catalysed processes do not enjoy the same popularity in commercial application as base-catalysed processes, largely because of the need for longer reaction times. Acid-catalysed pre-esterification may precede base-catalysed transesterification of the resulting pre-treated feedstock. Table 9.6 shows typical pre-esterification conditions in a procedure with two consecutive pre-esterification steps [30]. Esterification should reduce FFA levels to <1%. Figure 11.6 shows the corresponding simplified block flow diagram. Biodiesel plants that process used cooking oil or tallow and fat require additional processes to purify their feedstock before the biodiesel production process can start. These plants are more costly and have less valuable by-products. Typical procedures for the acid (H2SO4 or sulphonic acid)catalysed esterification of free fatty acids in admixture with triglycerides

Industrial process technology for biodiesel production

3

2

1

477

4

5 6

18

7

8 14

10

9

17

13 12

11 17

16

15

11.5 Energea process for producing biodiesel under high dynamic turbulence. Key: vegetable oil (1); alkali (2); alcohol (3); mixer (4); mixing chamber (5); high pressure pump (6); transesterification section (7); emulgator/ultrasonics (8); final product stream (9); manometer (10); molecular sieve filtration unit (11); glycerol product stream (12); FAME product stream (13); purification unit (14); recycle stream (15); phase separator (16); pump (17); vegetable oil recycle stream (18) (after ref. [28]).

require reaction times of at most 2–3 h [27, 31–33]. In the continuous acidcatalysed esterification technology of PCT Int. Publ. No. WO 2003/087278 A1, assigned to Ergün and Panning (to Energea Umwelttechnologie) [34], the interphases of the mixtures are increased in the reaction section by strong dynamic shearing cutting forces and/or turbulence (caused mechanically by the presence of mono- or polydisperse beads or by means of ultrasounds). The high-temperature (353–423 K) esterification begins at high pressure (7–15 MPa) and pressure is reduced during the process, whereby a high interface is maintained. A non-turbulent post-reaction section loaded with strong acidic ion-exchange resins further increases the reaction yield (see Fig. 11.7). Reaction times are short (min). The process is typically meant as a pre-treatment step for high FFA (> 5%)-containing triglycerides (e.g. UCO) for successive base-catalysed transesterification.

478

Biodiesel science and technology H2SO4

Feedstock (high in FFAs)

Feedstock pre-treatment

Methanol and water

MeOH

H2SO4/MeOH (Catalyst preparation) Methanol and water First esterification (333–343 K) (0.14–0.40 MPa)

Settling tank (24 h)

MeOH H2SO4

Settling tank (24 h)

Second esterification (333–343 K) (0.14–0.40 MPa)

Pre-treated feedstock

H2SO4/MeOH (Catalyst preparation)

11.6 Simplified block flow diagram for the acid-catalysed preesterification process of a high FFA feedstock (after refs [26, 30]).

Simultaneous transesterification of TGs and esterification of FFAs over acid catalysts is a considerable asset, which allows processing of low-cost, lowquality feedstocks (e.g. yellow grease). In general, acid-catalysed reactions are performed at high alcohol-to-oil molar ratios, moderately high temperatures and pressures, and high acid-catalyst concentrations (see Table 8.9). A simplified block flow diagram of a typical acid-catalysed simultaneous esterification/transesterification process is shown in Fig. 11.8 illustrating the most important steps in biodiesel production, as follows [26, 35]: ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

introduction of lipid feedstock, fresh and recycled alcohol and liquid acid catalyst into the main reactor; reaction; post-reaction separation of products and unreacted alcohol by distillation; catalyst (H2SO4) neutralisation with CaO, forming a CaSO4 precipitate and water; removal of the precipitate and washing of the liquid layer with water; settling of the liquid into two phases; distillation of the bottom layer to obtain 92% pure glycerol; and vacuum distillation of the upper phase consisting of biodiesel, water, alcohol and unreacted oil to obtain > 99.6% pure biodiesel.

Recovery and recycling of alcohol are required due to the large alcohol excess present.

Industrial process technology for biodiesel production 1

479

2

3

4

5

6

7

8 9

10

11.7 Acid-catalysed esterification of fatty acids and/or fatty acids contained in oils and fats. Key: fatty-acid containing raw material (1); alcohol/acid mixture (2); heating unit (3); high pressure pump (4); reaction section (5); (optionally) ultrasound (6); post-reaction section (7); pressure regulator (8); cooler (9); product collector tank (10) (after ref. [34]).

11.2.3 Batchwise manufacturing technologies Batch systems usually consist of a series of tanks in which each production is completed before being pumped to the next phase. The technology is relatively simple, suited to small-scale backyard producers, and generally less automated than continuous-flow processes. Each batch can take up several days to complete. Traditional batch processing using stirred-tank reactors (STRs) has been and still is the most widely used method for one- or two-step transesterification of vegetable oils and animal fats. Triglycerides can readily be transesterified batchwise at atmospheric pressure and at a slightly elevated temperature of approximately 333–343 K with an excess of methanol and in the presence of an alkaline catalyst. The mixture at the end of the reaction is allowed to settle. In discontinuous processing, it is possible to work in several stages,

480

Low-cost feedstock

MeOH

Biodiesel (99.6%) Unreacted oil

Filtration

Water removal settling tank (1)

H2SO4/MeOH (2)

Methanol and water

Vacuum distillation 537 K, 0.04 MPa (6)

Glycerol (92%) and water

Simultaneous esterification and transesterification (main reactor) (3)

Vacuum distillation 326 K, 0.04 MPa (6)

Water washing

Methanol Distillation 353 K, 0.19 MPa (4)

recycle H2SO4 + CaO Æ CaSO4 + H2O (5)

CaO

Gravity separation

CaSO4

11.8 Simplified block flow diagram for acid-catalysed esterification/transesterification of low-cost feedstock. Key: feedstock pre-treatment (1); catalyst preparation (2); simultaneous esterification (of FFAs) and transesterification (of TGs) (3); alcohol recycle (4); acid catalyst removal (5); (by-)product separation and purification process (6).

Biodiesel science and technology

H2SO4

Industrial process technology for biodiesel production

481

achieving a first reaction with only 85–90% conversion. The lower glycerol layer is then drawn off whereas the upper methyl ester layer is washed to remove entrained glycerol and is then processed further. Excess methanol is recovered in the condenser, sent to a rectifying column for purification and recycled. The reaction may then be finished by reheating and adding alcohol to achieve total conversion. It is also possible to reach a conversion rate of 98% by operating for a sufficiently long time in single-stage mode. Most plants in the world with a capacity range of 0.5–10 kt/yr are built as two-step batchwise operating units, each step consisting of a reactor vessel and a settling tank (see Fig. 11.4). These so-called mixer/settling systems are not very expensive, yield adequate product qualities, but present difficulties in consistency and safety. With modern process control they are well adapted to changing raw materials and small quantities. Batch processing with a two-phase liquid reaction results in long residence times and low yields. Under atmospheric conditions, transesterification can require many hours to proceed to completion. The Hielscher ultrasound technology (see Section 7.3.2, pp. 302–3) reduces the reaction time from several hours in a typical batch process to less than 1 h with 99% yield. Mild reaction conditions require removal of free fatty acids from the oil by refining or pre-esterification before transesterification. Pre-treatment is not required if the reaction is carried at high pressure (9 MPa) and temperature (513 K). Under these conditions, simultaneous esterification/transesterification takes place [36]. Consequently, batch reactors need to be run at high impeller intensity and high T, p to obtain reasonable reaction rates and yields. In the past, most biodiesel in the US was produced in reactors in charges of about 10 t. Batch systems offer the flexibility of varied feedstock source as each batch can be altered depending on the FFA level of the feedstock, while also offering the flexibility of troubleshooting during the processing stage. Batch systems typically only require one 8 h shift per day. On the other hand, batch processes suffer several disadvantages compared to continuous processes: ∑ ∑

They require larger reactor volumes and relative capital investment. They show inherently lower efficiency than continuous processes owing to the start-up and shut-down nature (leading to production downtimes). ∑ They present batch-to-batch variations in product quality. ∑ They operate at higher labour costs. Although batch plants require overall lower investment than continuous production plants and allow higher flexibility in the choice of TG feedstocks and reaction conditions, the current trend favours continuous production plants because of higher biodiesel throughputs and lower operational costs. In ‘continuous-flow/batch processes’ (or semi-continuous processes), biodiesel is produced in batches but continuously flows out of the plant.

482

Biodiesel science and technology

In PCT Int. Publ. No. WO 2003/022961 (to Bio-Clean Fuels) [37], Lastella describes a plant design with continuous-flow through all the reaction vessels and separation tanks for batchwise producing biofuel by (trans)esterifying (waste) oils and fats. Small plant footprint, low capital cost and minimal construction time enable site selection close to the raw material supplies, thereby minimising transportation costs for vegetable oil. Unrefined raw material (e.g. yellow grease) is heated and mixed with methanol and H2SO4 in a reaction vessel and then pumped to a settling tank for separation (methanol and H2SO4 at bottom; treated vegetable oil at top). The bottom material is recycled whereas the oil is transferred to an unloading tank, reheated, and then mixed with KOH and more methanol in a second reaction vessel. After a given reaction time (about 1 h) the mixture is pumped into a second settling tank. The ester product is separated from the top and glycerol and fatty acid soap are settled at the bottom. Because of the need for settlement in multiple settlement tanks, a continuous-flow process was not considered. US Patent No. 5,972,057 to Hayafuji et al. (to Lonford Development Ltd) [38] proposes a batchwise or semi-continuous production method for diesel fuel oil from Japanese waste oils (mainly SBO, RSO, CNO and CSO), dumped from restaurants, homes and food industry, by first removing solid materials (< 0.05%) by filtration, and moisture (< 0.03%) and odour materials (< 10 ppm) by evaporation. The method incorporates an initial pre-mixing step wherein the alkaline catalyst (KOH) is completely dissolved in hot alcohol before being added to the heated (298–473 K), vacuum-dehydrated and deodorised waste edible oil (with undisclosed FFA content and effect upon the reaction products) at p = 0.1–7.6 MPa under stirring, rather than mixing the catalyst, alcohol and oil together in the same tank simultaneously. An equilibrium conversion rate of 99% is reached in 1 min or less (at 333 K at a stirring speed of 300 rpm), as compared to 369 K in 30 min or more in the conventional method under the same conditions. However, the generated heat of dissolution might create a hazard. Many examples of one- or two-stage batch type transesterification processes are found in the literature, such as for winter rape oil [39], soybean oil [40], vegetable oils, fish oil, animal fat, waste oil/fat mixtures [41] and B. carinata [42]. Amongst others, Brazil opts for compact 500 to 1200 L/h biodiesel manufacturing plants installed in a 20 ft container frame for multi-feedstock transesterification.

11.2.4 Continuous-flow technologies New and more efficient processing schemes for large-scale production of biodiesel for fuel purposes are the key to commercialisation of biodiesel. Continuous-flow (CF) systems are highly efficient and quick at processing high-quality feedstocks with a low level of FFAs (<0.5%). Whereas smaller

Industrial process technology for biodiesel production

483

plants often use batch reactors, CF transesterification processing is especially well suited to more centralised, large capacity facilities, producing well over 8 kt/yr, where the economies of scale begin to take effect. Significant biodiesel production will only be achieved by continuous processing. Most continuous plants are found in Europe. Various continuous processes for the production of biodiesel, often involving continuous stirred-tank reactors (CSTR) or plug-flow reactors have been described [10, 26, 41, 43–49]. These systems are highly automated with excellent quality control. Continuous systems require operations 24 h/day. Many of the new continuous systems allow processing of high FFA feedstocks. These plants require at least 8 kt/yr to be economically viable. Large rendering companies are able to make effective use of these new multi-feedstock continuous-flow technologies. Advantages of continuous processing comprise higher esterification rates, a reduction in reactor volume and consequent reduction in relevant capital cost, easier process control and less variation in product quality. As compared to batch plants, a continuous transesterification process using homogeneous catalysts offers good opportunities for reducing the production costs [50]. However, this technology has different unavoidable drawbacks. In the presence of moisture or free fatty acids, soaps are formed that favour emulsion between glycerol and oil. Emulsion is also favoured by the presence of unreacted monoglycerides (MGs) and diglycerides (DGs). Therefore, a long settling time is necessary for the separation of the two emulsioned phases. Moreover, the recovered glycerol is, normally, impure, because of the presence of salts, soaps, MGs, DGs, and purification represents an additional cost. Continuous transesterification has seen several developments. Kusy [51] suggested an early scheme for continuous ethanolysis of vegetable oil, however without reporting actual process data. Later, Kreutzer [36] described a continuous process for the production of methyl esters from vegetable oil as a preliminary process for fatty alcohol production, but the process used high T, p conditions which might not be suitable for commercial biodiesel production. Good mixing is critical in transesterification reactions since methanol and oil are not miscible. In continuous transmethylation of palm oil using a co-solvent (toluene) to enhance mixing of the reactants and improve the reaction rate (to a few minutes) solvent consumption was relatively high, which increases production costs [52]. Noureddini et al. [43] used a motionless high-shear mixer for continuous conversion of vegetable oil into methyl esters. Darnoko and Cheryan [53] described an experimental laboratory set-up for continuous transesterification of palm oil using a 1 L CSTR and pumps for continuous delivery of oil and catalyst and for continuous removal of product (Fig. 11.9). Depending on the quality of the feedstock, the unit can be designed to operate at atmospheric pressure and slightly elevated temperatures or at high T, p (473–523 K, 5–10 MPa). Peterson et al. [10]

484

Biodiesel science and technology Condenser

Thermometer

Sample

Methyl esters

Separator

Reactor

Palm oil

MeOH -KOH

Heater/Stirrer

Glycerol

11.9 Experimental laboratory set-up for continuous transesterification using a 1 L continuous stirred-tank reactor (after ref. [53]).

have described continuous-flow biodiesel production (39 kgy) from RSO and EtOH. Fleisher et al. [54, 55] have described continuous transesterification in a plug-flow reactor with a single-pass residence time as low as 10 sec and conversions of 70–99+% using base catalysts (LiOH, NaOH, KOH) at high T, p (see Table 8.7). High T, p procedures are usually uneconomical. The continuous atmospheric pressure alkali-catalysed process for biodiesel production is currently applied industrially for refined rapeseed oil at T = 338–343 K. A significant advantage of Energea’s CTER (Continuous TransEsterification Reactor) technology is the acceleration of the transformation process: within a few minutes high-quality standardised biodiesel is produced from biogenic fats and oils [56]. It is well known that oscillatory flows through geometries in which a surface is presented transversely to the flow can produce uniform and efficient mixing patterns [57]. In oscillatory flow reactors (OFRs), which are a novel type of continuous reactor, consisting of tubes containing equally spaced orifice plate baffles, an oscillatory motion is superimposed upon the net flow of the process fluid, creating flow patterns conducive to efficient heat and mass transfer [11]. In OFRs, each baffle essentially behaves as a stirred tank. Hence, if there are enough baffles in series, a good approximation to plug-flow can be achieved. Unlike conventional plug-flow reactors (PFRs), where a minimum Reynolds number must be maintained, the degree of

Industrial process technology for biodiesel production

485

mixing is independent of the net flow, allowing long residence times to be achieved in a reactor of greatly reduced l/d ratio. Many long residence time processes are currently performed in batch. The OFR allows these processes to be converted to continuous, thereby intensifying the process. It has been demonstrated that the OFR is suitable for transesterification of vegetable oil to biodiesel [11]. A suitable conversion can be achieved in a residence time substantially lower than that of batch processes. Further advantages of producing biodiesel in OFRs should be realised when using a heterogeneous catalyst, as the OFR is ideal for suspending particles of solid catalyst or polymer supported catalysts. Introduction of the alcohol in the process can be advantageously conducted in several fractions. Introduction into a tubular reactor at two levels can be carried out by supplying the reactor with oil and about 2/3 of the alcohol, then introducing the alcohol supplement approximately at the level of the upper 1/3 of the catalytic bed. Similarly, the reaction is sometimes done in two steps in which ~ 80% of the alcohol and catalyst is added to the oil in a first-stage CSTR. Then, the product stream from this reactor goes through a glycerol removal step before entering a second CSTR. The remaining 20% of the alcohol and catalyst is added in this second reactor. This system provides a very complete reaction with the potential of using less alcohol than singlestep systems. In continuous reactions, the operation can be performed with several autoclaves and decanters. In the first reactor, a conversion of typically 85% is achieved; in a second reactor, decanting is done by evaporating the alcohol and by cooling. In a third, transesterification is completed by adding a portion of the alcohol that was evaporated previously. Finally, excess alcohol is removed in an evaporator, and the glycerol and esters are decanted. Process modelling of two-stage continuous, homogeneous base-catalysed, biodiesel production using SBO and RSO (canola) in CSTRs has been reported [23] (see Section 11.2). In PCT Int. Publ. No. WO 2003/076558 Adler [3] has described a continuous two-stage transesterification process at 338 K of biomethanol diesel in a small plant (production volumes of 0.05–1 kt/yr), e.g. for local energy supply for agriculture, from freshly pressed oils (e.g. RSO or LSO). A characteristic of the method is a methanol washing cascade before the transesterification process which removes FFAs (acid number ≤ 0.1 mg KOH/g) and other hydrophilic plant material (such as phospholipids) from the raw oil feedstock. This is at variance to the usual downstream washings of the biodiesel and raw glycerol products. The procedure suppresses soap formation in the reaction with anhydrous methanol/KOH. Various other base-catalysed continuous multi-step processes have been proposed: at T up to 373 K at ambient pressure with total reaction yields of 99.2–99.6% [46], and at T up to 373 K and 1 MPa with reaction yields of 98% [15]. The disclosure of Biodiesel Plants [58] for transformation of

486

Biodiesel science and technology

low-cost oils and fats at 318 K at ambient pressure (after extractive pretreatment with the glycerol phase) is more desirable. Process design and technological assessment of various alkali- and acidcatalysed continuous processes for biodiesel production (8 kt/yr) from virgin canola oil or waste cooking canola oil have been described [26]. The alkalicatalysed process using virgin vegetable oil as the raw material requires the fewest and smallest process equipment units but at a higher raw material cost. The acid-catalysed process using WCO is technically feasible with less complexity than the alkali-catalysed process using WCO, and is a competitive alternative. An economic evaluation of these alternative processes has been given [59]. Prototec (Germany) operates a two-stage (both transesterification–acid esterification) continuous, multi-feedstock production plant. While production costs of biodiesel are reduced on passing from batch to continuous transesterification, the same holds true for the use of heterogeneous rather than homogeneous catalysts, which offer many opportunities for improving the synthesis of biodiesel. An appropriate solid catalyst can be easily incorporated into a packed bed continuous-flow reactor, simplifying product separation and purification and reducing waste generation (EsterfipHTM technology). If a continuous process in a fixed bed is selected, it is possible to work advantageously at about 503–513 K and at 3–5 MPa if methyl esters are produced. For simultaneous esterification/transesterification in a continuous fixed-bed microreactor in supercritical conditions (Mcgyan process) [60], see Section 9.3.1. Recently, an economic evaluation of four continuous 8 kt/yr biodiesel production technologies for conversion of waste vegetable oil feedstocks, namely pre-treated alkali-catalysed, acid-catalysed, heterogeneous acidcatalysed and supercritical processes, was reported [61]. The relatively simple one-step heterogeneous acid-catalysed process guarantees lowest capital investment and total manufacturing costs (See Section 14.5.2).

11.2.5 Hybrid processing systems Various companies use hybrid systems that utilise a batch acid esterification pre-process for low to high FFA content feedstocks (5–30%). This creates a consistent feedstock that can then be fed into a continuous transesterification system. Other hybrid systems involve the use of continuous esterification, followed by batch transesterification reaction, and the resulting ester/glycerol processed continuously in downstream processing equipment. In this instance, only the transesterification reactor is batch and overall ‘continuous’ response is achieved using surge tanks ahead of and following the transesterification reactor. Depending on the size of facility, this approach can be as cost effective as a fully continuous system. Hybrid systems are suitable for 8–25 Mt/yr production. For more details, see Chapters 8 and 9 and Section 11.2.2.

Industrial process technology for biodiesel production

11.3

487

Selected proprietary transesterification processing technologies

The patent literature includes numerous proposals for transesterification processes of biogenic oils and fats. It should be stressed that the methyl esters produced are not biodiesel until the proper EN 14214 or ASTM D 6751 specifications are met. Different technologies are available and used in the industrial production of fatty acid esters, such as those developed by Lion Corporation (Japan), Henkel, Oelmühle Leer Connemann and Lurgi (Germany), BIOX Corporation (Canada), BDI and Energea (Austria), IFP (France) and many others (e.g. Cimbria Sket, Ekoil, Fox Petroli, MPOB, MUW, Navaol, Lonford Development) for a variety of feedstocks. For example, CD Connemann, Cimbria Sket, MUW and Lurgi mainly process fully refined RSO, whereas BDI, BDT, Ekoil and Energea (CTER) allow for multi-feedstock operation (see Tables 11.5 and 11.10). Many proprietary processes surround the chemical reactions and separation steps [62]. Providers of modern biodiesel process technology are listed in Table 11.5. Most of the Table 11.5 Selection of biodiesel technology providers Provider

Technologya

Feedstock

Ageratec (Norrköping, S) Batch (8000–24 000 L/d) Animal fats,   oils (20% FFA) Axens/IFP (Rueil-Malmaison, F) CF, solid phase Low FFA BDT (BioDiesel Technologies, Small-scale CF Low-high FFA   Vienna)   (200–1000 L/d) BDI-BioDiesel International Large-scale CF Multi-feedstock,   AG (Graz, A)   (> 6.8 ML/yr)   low–high FFA BIOX Corp. (Oakville, ON) CF (> 7.5 ML/yr) Multi-feedstock,   animal fats Bratney Companies Large-scale CFb (< 100 Mgy) Multi-feedstock   (Des Moines, IA) Crown Iron Works Co. Large-scale, batch, CF Multi-feedstock   (Roseville, MN) Desmet-Ballestra (Brussels, B) Large-scale Multi-feedstock Ekoil Biodiesel (Zohor, SK) Continuous (6–12 ML/yr) Multi-feedstock Energea Umwelttechnologie Large-scale, CF UCO   GmbH (Klosterneuburg, A) Greenline Industries Modular CF (3–100 Mgy) Multi-feedstock,   (Larkspur, CA)   low–high FFA Lurgi (Frankfurt a.M., D) Large-scale, batch, CF Refined oils Pacific Biodiesel, Inc. Semi-batch Multi-feedstock   (Honolulu, HI)   (1600–32 000 gpd)   (< 15% FFA) Westfalia Separator (Oelde, D) Large-scale CFb Multi-feedstock,   (100–1600 t/d)   low–high FFA Jatrodiesel, Inc. (Miamisburg, OH) Small-scale (1–5 MMgy) Multi-feedstock a

CF, continuous-flow. Connemann-ADM system CD process.

b

488

Biodiesel science and technology

biodiesel plant technology providers only offer plants that are economically feasible for more centralised, large-scale production using a continuous process. In order to reach these economies of scale, these plants operate mostly on virgin oils. The exception to this is large rendering plants that already have an abundant supply of cheaper used oils and rendered animal fats. Biodiesel processing technologies have been reviewed [24, 63, 64]. If low-quality beef tallow and cooking oils are used for biodiesel fuel, they must be refined by saponification using a NaOH solution to remove free fatty acids because of their high FFA contents. The refined beef tallow and cooking oils can then be base-transesterified to make biodiesel fuel. Otherwise, the slow acid-catalysed process [65], Lion Corporation’s ES (ester saponification) process [66], or a high pressure process known as the Henkel process [36] can be used. The latter two processes require low-water content oils and fats. Lion Corporation (Tokyo, Japan) developed an early continuous transesterification process using unrefined feedstock (known as the ES process). The free fatty acid in the oil is pre-esterified by passing the feedstock and methanol through a packed column of a special catalyst resin, after which alkali-catalysed transesterification is conducted through a two-stage reactor. High-quality products free from undesirable colouring impurities were claimed with high conversion rates (>99%). Beef tallow (containing 0.5 wt% FAME produced by preliminary esterification of free fatty acids; acid value <2.0 mg KOH/g) was converted to methyl esters in 99.1% yield at 338 K in 0.5–2.0 h [13, 67]. Henkel KGaA (Düsseldorf) has disclosed various technologies for vegetable oil transesterification (mainly for oleochemical purposes, not specifically intended for biodiesel production) [15, 31, 32, 36, 68]. Figure 11.10 shows a flow diagram of a Henkel process operated at 9 MPa and 513 K using unrefined oil as feedstock. Unrefined oil, methanol in excess, and alkali catalyst are metered and heated to 513 K before feeding into the reactor. The bulk of the excess methanol is flashed off as it leaves the reactor and is fed to a bubble tray column for purification. The recovered methanol is recycled into the system. The mixture from the reactor enters a separator where the glycerol in excess of 90% concentration is removed. The methyl ester is subsequently fed to a distillation column for purification. Further fractionation into special cuts may follow if desired. US Patent No. 4,698,186 to Jeromin et al. (to Henkel) [68] describes technology for lowering of the FFA content of unrefined fats and oils to an acid value below about 1 mg KOH/g by strongly acidic sulphonated mesoporous (cat)ion-exchange resins used in fixed or fluidised beds as solid esterification catalysts in mild reaction conditions (alcohol/VO molar ratio 20 : 1 to 25 : 1, atmospheric to low pressure, up to 0.5 MPa). Germ. Offenl. DE 3,932,514 A1 to Assmann et al. (to Henkel) [15]

Reactor

Methyl ester Glycerol Methanol

Oil

Catalyst Transesterification

Methanol/glycerol separation

Methyl ester distillation

Residue

11.10 Henkel process flow diagram for manufacture of methyl esters from unrefined oil by base-catalysed transesterification at 9 MPa and 513 K (after ref. [36]).

Industrial process technology for biodiesel production

Pure methanol

489

490

Biodiesel science and technology

describes continuous low-pressure transesterification of refined triglycerides (RSO, CNO; acid value < 1 mg KOH/g) in high yield (98%) at T < 373 K and p < 1 MPa (typically 0.4–0.5 MPa) by means of a homogeneously catalysed two-step conversion process in tube reactors (followed by settling vessels) with glycerol removal after each step (Fig. 11.11). After admixing of heated vegetable oil with (cold) methanol, the catalyst is added and the reaction mixture is passed through the first tube reactor (tR = 2–5 min for methanolysis). On exiting, the reaction mixture is allowed to post-react in a static separator (tR = 0.1–5 h) from which the heavy glycerol phase is extracted at the bottom. After enriching the top ester phase with a catalyst/ methanol solution (< 0.05% catalyst) the procedure is repeated and two product phases (FAME at the top and glycerol at the bottom) are obtained from the static separator. At least two plants (total capacity 170 kt/yr) are operating with this technology. The ester quality is good (high purity, low percentage of glycerides, very light colour), as is that of glycerol (92%). The disadvantages are high investment and energy consumption costs, free glycerol content (>0.02 wt%, i.e. beyond biodiesel specification), small depression of CFPP and low oxidation stability (because of a distillation step); finally, a 4–5% residue is lost. Oelmühle Leer Connemann’s low-cost ‘continuous deglycerolisation’ (CD) technology for transesterification was designed precisely for biodiesel on the basis of refined or well degummed rapeseed oil [46, 47]. The CD process, which in 1991 represented Europe’s first continuous operating lowCatalyst solution Oil/fat

10

5

Ester phase

Alcohol 3

9

4 1

2

7

6

8

Glycerol phase

11.11 Henkel’s continuous two-stage low-pressure transesterification process of refined triglycerides (reaction part). Key: static mixers (1, 2, 7, 8), heat exchanger (3), tube reactors (4, 9), static separators (5, 10), glycerol tank (6) (after ref. [15]).

Industrial process technology for biodiesel production

491

pressure transesterification process for biodiesel production (1 t/d), comprises reaction columns and centrifugal separators, a closed cycle for methanolysis and a closed loop for the extraction of glycerol and washing purification of the ester. Germ. Patent DE 4,209,779 C1 and US Patent No. 5,354,878 to Connemann et al. [46, 47] describe continuous multi-step transesterification of triglycerides (mainly RSO) in 99.2–99.6% yield with C1- to C4-monoalcohols at low temperature (typically 333–353 K) and atmospheric pressure using a homogeneous base catalyst. In CD processing for RME production, a mixture of oil phase, methanol and base catalyst is introduced at reaction temperature to the top of a first standing column reactor at a flow rate lower than the sinking rate of glycerol, which separates from the reaction mixture (Fig. 11.12). The mixture (transesterified for 85–90%) is then passed into a stirring reactor, then freed from additional glycerol in a first separating stage by short-term washing in a countercurrent stream of a hot aqueous extraction solution in order to finally reach a better conversion and a significant lower content of free and bonded glycerol. After passing the mixture in another standing column, the whole process is repeated. Afterwards the reaction product is freed of residual catalyst, glycerol, water and soap in another separating stage, under addition of an aqueous extraction buffer solution. Finally, the reaction mixture is freed of methanol by stripping, washed with suitable extraction and washing solutions and dried. The process yields biodiesel with low total glycerol content (0.1 wt%) without distillative purification. The intensive washing leads to very low free glycerol contents (< 0.002 wt%), low moisture (200 ppm) and methanol (0.0005 wt%) contents, and low acid number (< 0.15 mg KOH/g). As in CD processing, the free fatty acids formed (1–3%, according to catalyst) are post-esterified continuously by acid esterification, and an almost 100% yield is achieved [47, 69]. Glycerol is obtained as pharma glycerol (99.7%). Advantages of the CD technology are compactness, variable capacity (8–150+ kt/yr), rather low investment costs, operating conditions allowing for low energy consumption, excellent product quality, very high consistency and safety standards. Depending on the raw material the product colour may be yellowish. Continuous improvements have led to alcoholic neutralisation, glucosides handling for soybean oil feedstock, adaptation to ethanol and other alcohols instead of methanol, improvement of cold-flow properties, control of filter blocking tendencies, and suitable feedstocks. Today, seven plants using the so-called CD Process system Connemann-ADM (total 300 Mgy) are operating in Europe, with another 20 plants (1 Bgy or 3.3 Mt/yr) under construction elsewhere. The process is known for very stable production and safe EN 14214 quality with highest volumes; CD process plants were licensed worldwide to GEA-Westfalia, MAN-Ferrostaal, Cimbria-Sket, Bratney, Buss-SMS and others. More recently, CD technology has been adapted to acid raw materials. Germ. Offenl. DE 10,243,700 A1 to Connemann et al. [48] describes continuous

492

SV

SV C

He

SV

Biodiesel science and technology

He

F He D

MP

MP

SC

CR

SV

SV

CR

SV

SV

He He He

SR

S SR S

S

S

11.12 Oelmühle Leer Connemann’s multistage CD technology for transesterification of vegetable oils. Key: supply vessels (SV); standing column reactors (CR); stirring reactors (SR); heat exchangers (HE); separators (S); stripping column (SC); dryer (D); cooler (C); filter (F); mixing pumps (MP); (after ref. [46]).

Industrial process technology for biodiesel production

493

transesterification of high FFA-containing triglycerides at atmospheric pressure and 338 K by single- or multi-step acid-catalysed esterification of the free acids in the presence of glycerol and two-step base-catalysed transesterification requiring a complex flow scheme. Figure 11.13 shows a flow diagram of a Lurgi transesterification process operating at normal pressure [70]. The process requires the use of a degummed and deacidified feedstock. The refined vegetable oil and methanol are reacted at 333 K in a two-stage mixer-settler arrangement in the presence of a catalyst (NaOCH3). The product obtained in the first step is separated from the byproduct glycerol and then subjected to a second alcoholysis reaction. Glycerol produced in the reaction, dissolved in the surplus methanol, is recovered in the rectification column. Further glycerol water purification includes chemical treatment, evaporation, distillation and bleaching. Recovery of high-quality glycerol is essential for the integrated process economics. A countercurrent washing step for the methyl ester removes by-product components (entrained methanol and glycerol) and yields ready-for-use biodiesel after a final drying step. The methyl ester can be further purified by distillation. Surplus methanol recovered is used as a recycle stream. Biodiesel plants with a total capacity exceeding 1.5 Mt/yr have been realised by Lurgi. Lurgi plans construction of the world’s largest biodiesel plant [71]. While the Lurgi process involves two immiscible liquid phases which slowly react together to form the methyl esters, in the continuous BIOX process [72–74] an inert solvent, such as THF, is used that generates an oil-rich single phase containing the oil, methanol and catalyst. In this way, the reaction time is substantially reduced. In the presence of a co-solvent acid-catalysed (trans)esterification of high FFA feedstocks (waste cooking oils and animal fats) is completed in minutes instead of hours as in previous processes. The BIOX Corp. process (60 MMLy on commercial scale) is approximately 40–50% cheaper in capital expenditure and operational costs compared to other biodiesel processes. Because of the need for recovery of the inert solvent in the BIOX process by distillation, the energy costs are higher compared to the Lurgi process. Other problems are safety concerns over the use of co-solvents. Homogenisation of the reaction medium can also be achieved by dissolving the reactants in a subcritical or supercritical fluid (under pressure). Figure 9.2 shows a block flow diagram of a continuous process for transesterification in a critical fluid medium [75]. See also Section 7.3.2, pp. 305–8. The first industrial plant worldwide for rape biodiesel (Mureck, Austria, 1991) was developed by BDI-BioDiesel International AG (Graz, Austria). BDI also invented the so-called Multi-Feedstock Technology (MFT) as early as 1994 (using UCO, later followed by TLW). In fact, the first BDI MFT plant for biodiesel production from UCO was again operated in Mureck, 1994 (expansion project), whereas the first BDI MFT plants globally and

494

Reactor 1

Biodiesel science and technology

Wash column Distill Catalyst Reactor 2 Rect. column

Methanol

Oils and fats

Residue

Crude glycerol 80–85%

Distilled methyl ester

11.13 Lurgi process flow diagram for the manufacture of methyl esters by transesterification at normal pressure of degummed and deacidified feedstock (after ref. [70]).

Wash water

Industrial process technology for biodiesel production

495

in the EU for biodiesel from animal fat were located in Butler, KY (1998) and in Malchin, Germany (2001), respectively. BDI has developed into a global market leader for multi-feedstock technology (out of 28 BDI plants ordered/completed, 20 use MFT). Recently BDI has developed a robust new catalyst (RepCat) for its MFT process (see Section 15.3.1, pp. 731–2), which has been evaluated in 2007 at the BioDiesel plant Arnoldstein (Austria) using vegetable oils, UCO, TLW and trap grease, yielding high-quality biodiesel, glycerol (> 96%) and solid fertiliser [76]. MFT plants can switch between feedstocks on demand and do not need expensive fresh vegetable oils to produce top-quality biodiesel. MFT converts all fatty acids into biodiesel, including animal fat (with an FFA content between 7 and 30%). Any technology that does not convert fatty acids loses valuable feedstock for biodiesel production. MFT thus means higher investment costs but much better economic results compared with any other plant converting expensive fresh oils. Table 11.6 shows the competitive edges of BDI multi-feedstock technology. Also Desmet Ballestra’s technology offers feedstock flexibility (see Table 11.11). Most of the plants can use multi-feedstocks. Crude vegetable oils need to be mainly degummed and deacidified (via chemical neutralisation or via separate degumming followed by physical refining). Used frying oils are esterified in a side acid esterification unit before moving forward to the transesterification step. The first Desmet Ballestra continuous biodiesel plant was constructed in Umbertide (Italy) in 1993. Desmet Ballestra Oleo (DBO, Roma) is a major biodiesel technology supplier. The group has been involved in installation of 84 biodiesel plants (12 Mt/yr capacity) in Europe, USA, South America and Asia. More than 100 different oils and fats (with up to 70% FFA) have been tested on Ageratec (Norrköping, Sweden) modular production systems (0.6 to 7 kt/yr). BioKing BV (Roosendaal, Netherlands), a provider of compact biodiesel processors (from 300 L/d up), recently filed for insolvency as a result of a stagnating market. Figure 11.14 shows the process flow diagram of the original, conventional base-catalysed continuous Esterfip biodiesel process. Using a heterogeneous catalyst, the process scheme (dual-reactor IFP-Axens Esterfip-HTM technology) Table 11.6 Advantages of multi-feedstock technology ∑ ∑ ∑ ∑ ∑ ∑ ∑

Highest yield    Flexibility in raw materials Processing of UCO and TLW Processing of free fatty acids Feedstock specs: 20% FFA, 5% water Low cost feedstocks Approval for processing of SRM fats

496

Mineral acid

Partially refined vegetable oil

Reactor

Settler

Water

Neutralisation washing

Evaporation

Catalyst

Mineral acid

Glycerol purification

Fatty acids

11.14 Conventional base-catalysed biodiesel process (original Esterfip process).

Glycerol + water + salts

Biodiesel

Biodiesel science and technology

Methanol

Industrial process technology for biodiesel production

497

is greatly simplified (Figs 15.10 and 15.11; see also Figs 13.3 and 15.9) [77, 78]. This highly efficient continuous process produces high-purity biodiesel (> 99%) and salt-free glycerol (> 98%) from a variety of plant oils (refined oils, used frying oils, animal oils and fats). The fixed-bed catalyst process requires neither catalyst recovery nor aqueous treatment steps and thus enables a significant reduction in waste streams, which are drawbacks of the conventional base-catalysed homogeneous processes. In particular, there is no waste production of low-value fatty acids, no water saline streams requiring disposal, and no consumption or handling of chemicals, resulting in considerable economical advantages. It also features a lower catalyst requirement per ton of biodiesel produced than other processes. See also Section 15.3.1, pp. 729–31. Although algal biodiesel is still industrially premature several providers already offer proven technology, such as GreenFuel Technologies, Cambridge, MA (E2B™ technology), Valcent Products, Inc., El Paso, TX (Vertigro technology) and AlgaeLink NV, Spijkenisse, Netherlands (demonstration to industrial scale plants) (see Section 9.5). Solazyme has started road testing of microalgae-derived biodiesel (Soladiesel).

11.4

Selected biodiesel producers

The structure of the biodiesel industry is quite heterogeneous. Part of the plants are owned by the food industry, farmers, and investment groups lacking much technical background. Many production plants are not equipped with a laboratory. Typical transesterification plant sizes are 300 kg/h (pilot), 9 kt/yr (prefab) to 20–500 kt/yr (industrial). US plant production capacities typically range from 20 kgy to 80 MMgy. The predominant production mode is a batch or semi-continuous process. Production units designed for home use are closer to a capacity of 200 L/d or less [79]. Mobile biodiesel units using waste cooking oil (WCO) have been reported [80]. The conventional, rather complex industrial transesterification technology requires production facilities of at least 75 kt/yr for economic operation. Of course, the eco-balance of the overall process, consisting of raw material supply, production and end-use (local biodiesel market), is greatly improved by minimising transportation costs. Consequently, smaller plants are equally desirable [58]; see also Section 9.3.2. Pacific Biodiesel Technologies (Honolulu, HI) has implemented a variety of community-based production units (Table 11.7). Site selection for a transesterification unit depends on various factors including hardware costs, access to crushing facilities, and transportation costs of raw materials and end-products. Transesterification can be carried out in many specialty chemical plants with only slight modifications. Old chemical plants may offer high speed to market and low investment costs to

498

Biodiesel science and technology

Table 11.7 Community-based production unitsa

 

Company

Location

Feedstock

Capacityc

Start-up

Pacific Biodiesel Inc. Keystone Biofuels Bently Biofuels Pacific Biodiesel-Texas Energy Alternative   Solutions, Inc. SeQuential-Pacific   Biodiesel LLC Renew Legacy   Oil New York

Maui, HI Shiremanstown, PA Minden, NV Carl’s Corner, TX Gonzales, CA

UCO, TLW MFT UCO, RSOb UCO, CSO CSO, TLW

750 kgy 20 MMgy 1 MMgy 2.6 MMgy 1 MMgy

1996 2005 2005 2006 2007

Salem, OR

UCO, TLW, RSOb 5 MMgy

2008

New York, NY

UCO, TLW

2009

5 MMgy

a

Based on Pacific Biodiesel technology.   Canola. c At 16 March 2009. b

potential biodiesel producers [81]. While such chemical plants do have many advantages in the biodiesel business, they are generally not tied into seed crushing facilities. Association with a big oil mill is strategically advantageous in view of security of supply. Combining a crushing facility with a biodiesel plant assures total control over the entire biodiesel production process. Such independently operating plants (e.g. Producer’s Choice Soy Energy LLC, Moberly, MO; Green Fuel Corporacion and Dreyfus Argentina SA, both of Timbues, Santa Fé, Argentina) can eventually produce food-grade oil from the crushing plant and, with the flexibility in the biodiesel plant, operate with lower cost high FFA feedstock. Another important criterion in site selection is the use of existing infrastructure to transport raw materials and products, which are delivered and dispatched cost-effectively and in an environmentally friendly way at a sea harbour or by rail. The proximity to a refinery is another site advantage: the biodiesel produced can be used there directly in diesel blending (e.g. Diester Industrie/Grand Couronne in relation to Total and Shell). Biodiesel Vienna GmbH operates the only biodiesel pipeline in Europe. Figure 11.15 shows the block flow diagram for the official EU demonstration plant for biodiesel from animal fat and UCO (Motherwell, Scotland, 2005), based on BDI technology. Argent Energy Ltd/Motherwell (‘Sustainable Biodiesel Producer 2009’) is the leading biodiesel manufacturer in the UK and operates the world’s largest plant (50 kt/yr) for the conversion of used cooking oil and tallow from the meat industry using BDI technology. The plant provides nearly 5% of Scotland’s diesel requirements. UCO and TLW formerly went into animal feeds but this is no longer allowed (see Section 5.10.1). Argent Energy is owned by Argent Group Europe, with interests in meat wholesaling, animal by-products processing, tanneries, and wholesale fruit and vegetable distribution in the UK and abroad. The group owns a

Methanol Animal fat

Catalyst solution Acid

Fat preparation

Catalyst Recycle methanol

Preesterification

Transesterification

ME-purification

Methanolrecovery

MEDistillation

Quality control

Biodiesel EN 14214

Recycle methanol

Vegetable oil

Bio-heating oil

Fatty acid recovery Glycerinephase Acid

Glycerine preparation

Phase separation

Neutralisation

Methanolrecovery

Glycerine Techn. grade/ Ph. EUR/USP

Solid fertiliser drying

Solid fertiliser

499

11.15 Block flow diagram of EU Commission demonstration plant for biodiesel from animal fat (Motherwell, UK, 2005), based on BDI technology (after ref. [76]).

Industrial process technology for biodiesel production

Used cooking oil

500

Biodiesel science and technology

rendering business. The feedstock (max. 20% FFA) consists of 25 kt tallow from own production (compared with UK total tallow production of 250 kt/yr) and 30 kt UCO from own collection facility (UK total collected UCO 100 kt/yr). A fourfold increase in capacity to 200 kt/yr by 2008 is foreseen. Similarly, Transpacific Industries (TPI) is providing 50% of a 45 kt/yr biodiesel production facility in Brisbane through its used cooking oil collection business. ConocoPhillips and Tyson Foods share a partnership on tallow. The closed loop between feed, tallow and biodiesel of Fig. 11.16 is illustrated by the co-operation of GEN-X Energy Group, Inc. and Westway Feed Products, Inc., Burbank, WA. The first industrial European biodiesel demonstration plant (Oelmühle Leer Connemann GmbH & Co., Leer, 80 kt/yr) dates from Sept. 1995. With an installed European transesterification capacity of over 1 Mt/yr and a total production of 770 kt, only 195 kt biodiesel was produced and sold in 1997; other outlets for fatty acid esters were for oleochemical use and heating oil. There were some 85 biodiesel plants in 21 countries in 2000 [82]. Meanwhile biodiesel production and production capacity have increased considerably worldwide (see Table 11.8). The (partially speculative) rapid growth in biodiesel production has led to an alarming overcapacity worldwide. At today’s high vegetable oil Livestock industries

Food TLW

Biodiesel

Feed

Glycerine

11.16 Tallow biodiesel. Table 11.8 World biodiesel capacities and production (Mt/yr) (after ref. [83]) Year

Nameplate capacity

Production

2004 2005 2006 2007 2008

2.8 6.5 12.2 23.1 32.6

2.7 3.6 7.1 8.5 11.1f

f = forecast.

Industrial process technology for biodiesel production

501

prices the recently developed biodiesel capacity is unlikely to be fully utilised (not exceeding 40–45% for US plants in 2007–08). Some biodiesel plants currently on the drawing board may never materialise until there is a renaissance in the market. Biodiesel production plants have now been identified in almost all European countries (EU28; see Table 14.31), the Americas (USA, Canada, Argentina, Brazil, Colombia), Australasia (e.g. Australia, P.R. China, Philippines, Malaysia, Singapore, Indonesia, South Korea) and Africa (South Africa). The status of Asian biodiesel is given in Table 11.9. Table 11.10 lists some selected European biodiesel producers and Table 11.11 a selection of European biodiesel plants based on Desmet Ballestra technology. IEA/BA Task 39 has carried out a study (2004) on the best examples of European biodiesel production plants. Biodiesel from the German rendering company Saria Bioindustries (12 kt/yr) did not fulfil the European standard EN 14214 in all parameters. The unsuitable winter performance of Saria tallow biodiesel is compensated by mixing with RME. Recyclat Tierischer Rohstoffe (RTR, Selm, Germany) also produces biodiesel from animal fats. Esterfip-HTM technology (using a heterogeneous catalyst), developed by IFP and commercialised by Axens, has recently been chosen for several large biodiesel projects (Table 15.8). The process can use a variety of plant oils (RSO, PMO, SBO, SNO). Apart from Esterfip-H™ technology, most other recently installed and commissioned first-generation biodiesel (FAME) plants are alkaline catalyst based. New European plants rely on domestic feedstock (RSO for Germany; UCO, TLW for Scotland) or on partly imported raw materials (RSO, SBO, PMO for the Netherlands; RSO/SNO for Cyprus; SBO, SNO, UCO, PMO, POo for Spain) or are multi-feedstock (unspecified; Belgium). Nordbrandenburger Umesterungswerke (Schwedt/Oder) has recently (2006) started up a 220 kt/yr Table 11.9 Asian biodiesel (after ref. [84])   Country

Domestic feedstock availability

Production Oil trade balance status (2007)

P.R. China India Japan South Korea Taiwan Thailand Philippines Singapore Indonesia Malaysia

RSO, PMO, JCO, WVO Inedible oils, JCO RCO, UCO CNO, PMO, WVO RCO PMO CNO PMO PMO PMO

430 kt/yr 100 kt/yr 4 kt/yr 500 kt/yr 6 kt/yr 18 kt/yr 144 kt/yr 250 kt/yr 820 kt/yr 1.5 Mt/yra

a

12 plants operating; more licences issued.

Large VO importer Large VO importer VO, CNME importer VO importer, PME exporter VO, BDF importer PMO exporter Large CNO exporter PMO importer, PME exporter Large PMO exporter Large PMO exporter

Production Production Technology Feedstock capacity 2003 (kt)     2003 (kt)    

Max. FFA Yielda QC biodiesel QC content (%) glycerol

ADM Oelmühle Leer Continuous 110 112 RSO 1.0 1000 EN 14214 Connemann, Leer (D) (CD) Agropodnik 50 30 Batch RSO, UCO 2.0 980 EN 14214 Jihlava (CZ) Biodiesel Kärnten Semi-continuous 10% RSO, 20% 25 7 20.0 970 EN 14214 Arnoldstein (A) (BDI) TLW, 70% UCO Bio-Ölwerk Magdeburg Continuous 50 35 RSO 0.05 980 DIN 51606 Magdeburg (D) (Cimbria Sket) Diester Industrie Continuous 70% RSO, 20% 250 239 n.g. n.g. EN 14214 Grand Couronne (F) (Henkel) SNO, 10% VO Ekoil Biodiesel Continuous 30% RSO, 10% 25 6 6.0 970 EN 14214 Zohor (SK) (Proprietary) VO, 60% UCO EOP ElbeOel Prignitz Continuous 30 7 RSO 1.0 995 EN 14214 Falgenhagen (D) (Cimbria Sket) Fox Petroli Batch 90% RSO, 10% 100 90 n.g. n.g. EN 14214 Vasto (I) (Proprietary) SBO Mitteldt. Umesterungswerke Continuous 150 75 RSO 3.0 980 EN 14214 Greppin (D) (CD) Natural Energy West Continuous 100 95 RSO 0.05 995 DIN 51606 Marl (D) (Lurgi) Novaol Batch, semi-continuous RSO, SNO 100 80 n.g. n.g. EN 14214 Livorno (I) (Proprietary) (no UCO) Biodiesel Raffinerie Continuous 10% RSO, 90% 40 12 5.0 1000 EN 14214 Zistersdorf (A) (Energea) TLW and UCOb Rheinische Bioester Continuous 100 75 RSO 3.0 978 EN 14214 Neuss (D) (Proprietary)

BS 2623 (99.7%) BS 2621 (80%) BS 2621 (80%) BS 2623 (99%) n.g. BS 2621 (80%) BS 2622 (88%) BS 2622 (88%) BS 2623 (99%) BS 2622 (85.2%) BS 2622 (88%) BS 2621 (80%)   BS 2621 (80%)

Biodiesel science and technology

Producer

 

502

Table 11.10 Selected European biodiesel producers (after ref. [69])

a

kg biodiesel from 1000 kg raw material. Multi-feedstock: CO, PMO, PNO, RSO, SBO, TLW, UCO, WVO.

b

BS 2621 (80%) BS 2623 (99%) (50%) BS 2621 (80%)

Industrial process technology for biodiesel production

Saria Bioindustries Batch 12 12 TLW 20.0 970 EN 14214 Malchin (D) (BDI) Biodiesel Schwarzheide 100 n.g. Continuous RSO n.g. 980 DIN 51606 Schwarzheide (D) Stocks del Vallés Batch 6 4.5 TWO, UCO 20.0 1000 DIN 51606 Montmelo (E) (BDI) Thüringer Methylesterwerke Continuous RSO, TLW, 45 42 20.0 1000 EN 14214 Nieder Pöllnitz (D) (BDI) UCO

503

504 Productsc

Company

Location

Capacity (kt/yr)

Feedstock

Slunchevi Luchi Chemoproject Elvi Estereco Navaol Biopaliwa KS Wratislawia Fabrica Torrejana de   Biocombustiveis SA Rompetrol Martifer Linares Technology Greenenergy

Bulgaria Czech Republic Thessaloniki (Greece) Umbertide (Italy) Livorno (Italy) Poland Wroclaw (Poland) Lisbon (Portugal)

100 100 50 30 250 100 150 50

Multiple Multiple Multiple Multiple Multiple RSO Multiple Multiple

Romania Romania Linares (Spain) Immingham (U.K.)

60 100 100 100–200

Multiple (PMO, SBO, Multiple (PMO, SBO, Multiple (PMO, SBO, RSO, Multiple (PMO,

a

(PMO, (PMO, (PMO, (PMO, (PMO,

SBO, SBO, SBO, SBO, SBO,

SNO, RSO) RSO) SNO, RSO) SNO, RSO)a, UFO SNO, RSO)b, UFO

(VOs)b (VOs)b, UFO SNO, RSO) SNO, RSO) SNO, RSO)b SBO, SNO, RSO)b

Refined. Crude. c A, biodiesel and crude glycerol; B, biodiesel and pharma grade glycerol; C, biodiesel and 88% crude glycerol. b

A A A A A A B A C A A A

Biodiesel science and technology

Table 11.11 Selection of Desmet Balestra biodiesel plants operating in Europe

Industrial process technology for biodiesel production

505

rape diesel production facility. The largest first-generation European biodiesel plant will be operated by INEOS Enterprises (Grangemouth, Scotland) with 500 kt/yr (as from 2008). INEOS’ strategy – if realised – aims at a 1.2 Mt/ yr biodiesel production in 2010 (in the UK, Belgium, France and Germany). A major production centre (400 kt/yr) for rape and soy biodiesel, owned by Biopetrol/Vopak, is under construction in Rotterdam (2007). J & S BioEnergy (Mercuria) has commissioned a 200 kt/yr RSO, SBO, CO biodiesel plant in Amsterdam (2008). New South-East Asian plants are CNO, PMO or CPO grade based, as compared to SBO for the US and Argentina, and SBO, PMO in the case of Brazil. Figure 11.17 shows the integrated logistics of a bioethanol (sugarcane)/ biodiesel (SBO, TLW) plant (Barrálcool, Barra do Bugres, MT, Brazil, 2006). The cane bagasse-fired co-generation plant of the sugar and ethanol mill provides all the energy for the integrated mill operations, distillations, etc., while the biodiesel output fuels the farm machinery. The model of building a biodiesel plant onto an existing cane mill reduces required investment and costs while making maximum use of acreage around the plant.

11.5

Biodiesel blending techniques

Blending is an attractive way to valorise cheaper feedstocks into biodiesel. Feedstock blending (before transesterification) may be carried out by the Bioelectricity

Co-generation

Ethanol Cane bagasse

Heat

Sugar

Cane

Crusher (oil extraction)

Alcohol mill

Hydrated ethanol Anhydrous ethanol

Oilseeds

Heat

Catalyst Oil cake Biodiesel unit

Biodiesel

Vegetable oil

Glycerol

11.17 Integrated logistics of a bioethanol/biodiesel plant (Barrálcool, Barra do Bugres, MT, Brazil).

506

Biodiesel science and technology

biodiesel producer, or FAME blending by the diesel producer or dispencer. The most important part of product quality after good feedstock is to get the final product blended correctly. Blending processes can have considerable impact on product homogeneity. Challenges to getting an adequate mix during blending derive from the fact that biodiesel is typically denser than petroleum diesel, and also the cold-flow properties can change with different feedstocks. Ambient temperature affects the mixing. Blending fuels in cold weather with non-heated biodiesel reduces the chance of an adequate blend prior to delivery. To account for cold-flow properties of each feedstock, B100 should ideally be kept at least 10 K above the cloud point for blending and storage (see Section 14.4 for biodiesel cold-temperature operability and handling). There are basically two blending options available to marketers and distributors of biodiesel: splash blending (either in a tank or in the delivery truck) and in-line blending in various forms (sequential, ratio, hybrid or sidestream blending) [85–87]. Each type of blending carries with it a variety of costs, benefits and problems. Splash blending is the most common and least accurate method of blending. In splash blending the distributor first pumps B100 into the delivery truck at the time of loading, followed by diesel fuel, or vice versa. The hope is that the blend will be adequately mixed by the time the truck arrives at the delivery site. Prior to delivery the mix should be analysed. Splash-blended products have a tendency to stratify, failing to mix thoroughly unless some type of static mixer is used after the products are loaded. Typical results for splash blending a truck for B20 indicate a blend ratio of 11.9% at the top and 24.1% at the bottom after 5 min after filling [88]. In conventional batch blending, biodiesel and diesel fuel are pre-blended in a designated bulk storage tank by a distribution company before loading into a delivery tank. Batch blending is wasteful in terms of both time and storage facilities. Pre-blending has the same challenges facing splash blending with the addition of stratification of different concentrations in the tank due to different densities. Various quality surveys (see Section 12.4) have confirmed the inadequate mixing by splash blending. A transition to other forms of blending (in particular in-line or ratio blending) should seriously be considered. In-line blending (ILB) is a technological advancement. In-line or injection blending is the controlled proportioning of two or more component streams to produce a final blended product of closely defined quality from the beginning to the end of the batch, thus permitting the product to be used immediately or loaded directly to the customer. Table 11.12 lists the technical and economic advantages over batch blending. In-line blending keeps quality up, costs down [89]. It is often more economic than batch blending methods by faster blending and requiring less manpower and storage facilities. An in-line blending system can be used to deliver the finished product directly into a

Industrial process technology for biodiesel production

507

Table 11.12 Advantages of in-line blending over batch blending ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Reduced process time (high-throughput production) Increased flexibility of fixed assets Improved quality Reduced waste and bonus (‘give away’) Simplified planning Lower production and labour costs Reduced capital cost (no bulk storage tanks) Simplified process plant

pipeline or ready to ship. With ILB, the biodiesel is metered into the diesel fuel as it travels through a pipe. Mixing the component streams together is critical when blending in line. Unlike batch blending the mixing of an in-line blend has to be performed dynamically as the component streams converge to ensure that the blend is continuous and homogeneous. The degree of in-line mixing in a blend header depends on the rate of energy dissipation. Natural turbulence is usually inadequate to ensure a homogeneous blended product throughout the product flow range. In-line blending describes real-time measurement of liquid components using a series of flowmeter streams to automatically control the flow rate at the proper ratio. An in-line blending system will typically comprise two or more component streams, each with a strainer, flow metering device, temperature element, flow control valve and check valve. The blend header will consist of a mixing device and possibly a sampler and/or analyser. If one of the components varies in quality the blended product will be affected. This can be overcome by incorporation of an analyser in the mixed output of the blender in a closed loop control system. Relatively few biodiesel fuel distributors are using in-line blending. In-line blending systems are supplied in many different configurations. Sequential blending loads multiple products such as biodiesel and diesel, one at the time, through one meter and control valve. The method is commonly used for products with similar density and viscosity, which consequently mix well. However, this is not the situation for biodiesel and diesel. Sequential blending may then result in stratification due to inadequate mixing. Ratio blending is a better option. Ratio blending loads multiple products simultaneously rather than sequentially. Ratio blending employs a meter and control valve for each product and a common downstream header, thereby achieving thorough mixing. Because the biodiesel and diesel are pumped in at the same time, they tend to mix better than they do with sequential blending. Ratio blending is the normal technique of blending two or more products together by volume or weight. The accuracy of a ratio blending system is dependent on the accuracy of the flowmeters and transmitters.

508

Biodiesel science and technology

Hybrid blending is a combination of sequential and ratio blending that is designed for ratio blending B100 into existing diesel oil sequential blenders. In sidestream (injection or wild-stream) blending, the B100 is metered into the main diesel line upstream of the delivery meter prior to loading the truck. Passing through the delivery meter gives the blend an additional mechanical mix. Additional mixing for all these systems occurs as the fuels enter the receiving tank. These methods offer better blend consistency than splash or pre-blending. Sampling the quality of a blended product is important and regulated by international standards. Sampling of a blend must be representative; small samples should be taken at flow proportioned intervals from the mixed homogeneous section of the blend header. A portable fixed filter IR analyser can be used to measure the blend ratio (see Section 12.5.2). It is advisable to test for density, flash point, total contamination, oxidative stability, acid value, and free and total glycerol throughout the blending process. It is equally recommended to blanket all biodiesel produced with nitrogen to maintain stability and eliminate moisture from the time it leaves the plant until delivery to finishing tanks, railcars, tanker trucks or ships. New to the US retail market are non-UL certified fuel dispensers that offer various biodiesel blends (typically B5, B20 or B50); the blend quality delivered needs to be assessed (see Section 12.4).

11.6

Bibliography

A. Demirbaş, Biodiesel: A Realistic Fuel Alternative for Diesel Engines, Springer-Verlag, London (2008). National Renewable Energy Laboratory, Biodiesel Handling and Use Guide, 4th edn, NREL, Golden, CO (2008); www.nrel.gov/vehiclesandfuels/npdf/ feature_guidelines.html. J. Van Gerpen, R. Pruszko, D. Clements, B. Shanks and G. Knothe, Building a Successful Biodiesel Business, Biodiesel Basics, Ames, IA (2006). W.H. Kemp, Biodiesel, Basics and Beyond: A Comprehensive Guide to Production and Use for the Home and Farm, Aztext Press, Tamworth, ON (2006). L. Estill, Biodiesel Power, the Passion, the People, and the Politics of the Next Renewable Fuel, New Society Publishers, Gabriola Island, BC (2005). G. Pahl, Biodiesel: Growing a New Energy Economy, Chelsea Green Publishing Co., White River Junction, VT (2005); 2nd edn (2008). G. Knothe, J. Van Gerpen and J. Krahl (eds), The Biodiesel Handbook, AOCS Press, Urbana, IL (2005). P.C. Berger, Best Case Fallbeispiele der Europäischen Biodieselindustrie, Institut für Technologie und nachhaltiges Produktmanagement, Wirtschaftsuniversität Wien, Schriftenreihe Umweltschutz und Ressourcenökonomie, Band 42, Vienna (2004).

Industrial process technology for biodiesel production

11.7

509

References

[1] L.P. Ramos, Biodiesel in South America, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [2] J. Jobe, Biodiesel in the US – Growing the fuel supply, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [3] B. Adler (to Dracowo Forschungs- u. Entwicklungs GmbH), Method for the continuous production of biomethanol diesel, PCT Int. Publ. No. WO 2003/076558 A2 (18 Sept. 2003). [4] M. Boyd, A. Murray-Hill and K. Schaddelee, Biodiesel in British Columbia, Feasibility Study Report, WISE Energy Co-op/Eco-Literacy Canada (2004). [5] C.A. Johnson, Biodiesel production trends survey 2008, Biodiesel Mag. 5(5) (2008) 38–42. [6] J. Seybold, Taking the pulse of the biodiesel industry, Biodiesel Mag. 5(2) (2008) 166–71. [7] S. Lavorerio, C. Bambara and V. Fuschetti, A modular approach to plant design, Biodiesel Mag. 5(1) (2008) 98–102. [8] F. Omota, A.C. Dimian and A. Bliek, Fatty acid esterification by reactive distillation. Part I: Equilibrium-based design, Chem. Engng. Sci. 58 (2003) 3159–74. [9] F. Omota, A.C. Dimian and A. Bliek, Fatty acid esterification by reactive distillation. Part II: Kinetics-based design for sulphated zirconia catalysts, Chem. Engng. Sci. 58 (2003) 3175–85. [10] C.L. Peterson, J.L. Cook, J.C. Thompson and J.S. Taberski, Continuous flow biodiesel production, Appl. Engng. Agric. 18 (2002) 5–11. [11] A.P. Harvey, M.R. Mackley and T. Seliger, Process intensification of biodiesel production using a continuous oscillatory flow reactor, J. Chem. Technol. Biotechnol. 78 (2003) 338–41. [11a] M.A. Dubé and A. Tremblay, unpublished results (2009). [12] J. Van Gerpen, Biodiesel processing and production, Fuel Proc. Technol. 86 (2005) 1097–107. [13] Y. Tanaka and A. Okabe (to Lion Corp.), Verfahren zur Herstellung niederer Fettsäurealkylester, Germ. Offenl. DE 3,020,612 (5 May 1980). [14] A. Davidsohn, Modern production technology for fatty acid methylester-derived surfactants and soap, Seifen, Öle, Fette, Wachse 114 (1988) 595–600. [15] G. Assmann, G. Blasey, B. Gutsche, L. Jeromin, J. Rigal, R. Armengaud and B. Cormary (to Henkel), Kontinuierliches Verfahren zum Herstellen niederer Alkylester, Germ. Offenl. DE 3,932,514 A1 (29 Sept. 1989). [16] S. Saka (to Kyoto Lonford Development Ltd), Process for producing fatty acid alkyl ester composition, PCT Int. Publ. No. WO 2003/106604 (24 Dec. 2003); US Pat. Appl. 2006/0025620 A1 (2 Feb. 2006). [17] S. Saka and D. Kusdiana, Biodiesel fuel from rapeseed oil as prepared in supercritical methanol, Fuel 80 (2001) 225–31. [18] M.A. Dasari, M.J. Goff and G.J. Suppes, Noncatalytic alcoholysis kinetics of soybean oil, J. Am. Oil Chem. Soc. 80 (2003) 189–92. [18a] M. Anez – Lingerfelt, Coalescing technology for liquid/liquid separations, Biodiesel Mag. 6(8) (2009) 50–2. [19] Rohm & Haas Company, AmberliteTM BD10DryTM Biodiesel Purification Technology, Technical Bulletin, Philadelphia, PA (2007); www.amberlyst.com. [20] B.S. Cooke, Adsorbent purification of biodiesel, The Dallas Group of America Internal Report, Jeffersonville, IN (2007); biodiesel @ dallasgrp.com.

510

Biodiesel science and technology

[21] J. Van Gerpen and K. Menges, Evaluation of Magnesol R60 as an alternative to water washing during biodiesel production, Final Report to the Dallas Group of America, Ames, IA (3 May 2004). [22] M. Mittelbach and B. Koncar (to Vogel & Noot Industrieanlagenbau), Method for the preparation of fatty acid alkyl esters, US Pat. 5,849,939 (15 Dec. 1998). [23] D. Tapasvi, D. Wiesenborn and C. Gustafson, Process model for biodiesel production from various feedstocks, Trans. ASAE 48 (2005) 2215–21. [24] J. Connemann and J. Fischer, Biodiesel in Europe 1998, Paper presented at Intl. Liquid Biofuels Congress, Curitiba, PR, Brazil (19–22 July 1998), unpublished; http://www.biodiesel.de. [25] M. Zappi, R. Hernandez, D. Sparks, J. Horne, M. Brough, S.M. Arora and W.D. Motsenbocker, in A Review of the Engineering Aspects of the Biodiesel Industry, MSU E–TECH Laboratory Report ET-03-003, Mississippi Biomass Council, Jackson, MS (2003), p. 71. [26] Y. Zhang, M.A. Dubé, D.D. McLean and M. Kates, Biodiesel production from cooking oil: 1. Process design and technological assessment, Bioresour. Technol. 89 (2003) 1–16. [27] M. Mittelbach and M. Koncar (to Vogel & Noot Industrieanlagen), Process for preparing fatty acid alkyl esters, Eur. Pat. Appl. EP 0,708,813 A1 (1 May 1996). [28] N. Ergün and P. Panning (to Energea Handels GmbH), Method for producing fatty acid methyl ester and equipment for realising the same, PCT Int. Publ. No. WO 99/26913 (3 June 1999). [29] R. Stern, G. Hillion and J.-J. Rouxel, Process for producing esters of fatty substances and the high purity esters produced, US Pat. 6,147,196 (14 Nov. 2000). [30] M. Canakci and J. Van Gerpen, A pilot plant to produce biodiesel from high fatty acid feedstocks, Trans. ASAE 46 (2003) 945–54. [31] H. Lepper and L. Friesenhagen (to Henkel), Verfahren zur Herstellung von Fettsäureestern kurzkettiger aliphatischer Alkohole aus freie Fettsäuren enthaltenden Fetten und/oder Ölen, Eur. Pat. Appl. EP 0,127,104 A (5 Dec. 1984). [32] H. Lepper and L. Friesenhagen (to Henkel), Verfahren zur Herstellung von Fettsäuremethylestern, Eur. Pat. Appl. EP 0,184,740 A (18 June 1986). [33] Y. Kawahara and T. Ono (to Kao Soap Co., Ltd.), Process for producing lower alcohol esters of fatty acids, US Pat. 4,164,506 A (14 Aug. 1979). [34] N. Ergün and P. Panning (to Energea Umwelttechnologie), Method and system for the esterification of fatty acids, PCT Int. Publ. No. WO 2003/087278 A1 (23 Oct. 2003). [35] E. Lotero, Y. Liu, D.E. Lopez, K. Suwannakarn, D.A. Bruce and J.G. Goodwin Jr, Synthesis of biodiesel via acid catalysis, I&EC Res. 44 (2005) 5353–63. [36] U.R. Kreutzer, Manufacture of fatty alcohols based on natural fats and oils, J. Am. Oil Chem. Soc. 61 (1984) 343–8. [37] J.P. Lastella (to Bio-Clean Fuels), Method and apparatus for making biodiesel fuel, PCT Int. Publ. No. WO 2003/022961 A1 (20 Mar. 2003). [38] S. Hayafuji, T. Shimidzu, S. Oh and H. Zaima (to Lonford Development Ltd), Method and apparatus for producing diesel fuel oil from waste edible oil, US Pat. 5,972,057 (26 Oct. 1999). [39] C.L. Peterson, M. Feldman, R. Korus and D.L. Auld, Batch type transesterification process for winter rape oil, Appl. Engng. Agric. 7 (1991) 711–16. [40] W.D. Stidham, D.W. Seaman and M.F. Danzer (to West Central Cooperative),

Industrial process technology for biodiesel production

[41]

[42]

[43]

[44] [45] [46]

[47]

[48]

[49]

[50] [51] [52] [53] [54]

[55] [56] [57]

[58]

511

Method for preparing of lower alkyl ester product from vegetable oil, US Pat. 6,127,560 (3 Oct. 2000). N. Bam, D.C. Drown, R. Korus, D.S. Hoffman, T.G. Johnson and J.M. Washam (to Idaho Research Foundation), Method for purifying alcohol esters, US Pat. 5,424,467 (13 June 1995). M. Cardone, M. Mazzoncini, S. Menini, V. Rocco, A. Senatore, M. Reggiani and S. Vitolo, Brassica carinata as an alternative crop for the production of biodiesel in Italy; agronomic evaluation, fuel production by transesterification and characterization, Biomass Bioen. 25 (2003) 623–36. H. Noureddini, D. Harkey and V. Medikonduru, A continuous process for the conversion of vegetable oils into methyl esters of fatty acids, J. Am. Oil Chem. Soc. 75 (1998) 1775–83. D.G.B. Boocock (to Biox Corp.), Process for production of fatty acid methyl esters from fatty acid triglycerides, US Pat. 6,712,867 B1 (10 Mar. 2004). V. Jordan and B. Gutsche, Development of an environmentally benign process for the production of fatty acid methyl esters, Chemosphere 43 (2001) 99–105. J. Connemann, A. Krallmann and E. Fischer (to Oelmühle Leer Connemann), Verfahren zur kontinuierlichen Herstellung von C1- bis C4-Alkylestern höherer Fettsäuren, Germ. Pat. DE 4,209,779 C1 (3 Mar. 1992); Eur. Pat. Appl. EP 0,562,504 A2 (22 Mar. 1993). J. Connemann, A. Krallmann and E. Fischer (to Oelmühle Leer Connemann), Process for the continuous production of lower alkyl esters of higher fatty acids, US Pat. 5,354,878 (11 Oct. 1994). J. Connemann, J. Fischer, H. Groos and A. Philippsen (to Oelmühle Leer Connemann), Verfahren und Vorrichtung zur Herstellung von Biodiesel, Germ. Offenl. DE 10,243,700 A1 (1 Apr. 2004). G. Assmann, G. Blasey, B. Gutsche, L. Jeromin, J. Rigal, R. Armengaud and B. Cormary (to Henkel KaA), Continuous process for the production of lower alkyl esters, US Pat. 5,514,820 (7 May 1996). F. Ma and M.A. Hanna, Biodiesel production: a review, Bioresour. Technol. 70 (1999) 1–15. P.F. Kusy, Transesterification of vegetable oils for fuels, Proc. Intl. Conf. on Vegetable Oils as Fuels (ASAE), St. Joseph, MI (1982), pp. 127–37. K. Krisnangkura and R. Simamahamnop, Continuous transmethylation of palm oil in an organic solvent, J. Am. Oil Chem. Soc. 69 (1992) 166–9. D. Darnoko and M. Cheryan, Continuous production of palm methyl esters, J. Am. Oil Chem. Soc. 77 (2000) 1269–72. A. Center, E. Johnson, A. Nady, C. Wood and C. Fleisher (to Cornell Research Foundation, Inc.), Continuous transesterification process, PCT Int. Publ. No. WO 2003/087279 A2 (23 Oct. 2003). C.A. Fleisher (to Biodiesel Technologies, Inc.), Continuous transesterification process, US Pat. Appl., 2003/0229238 A1 (11 Dec. 2003). N. Ergün, Modern biofuels technology from Austria, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). C.R. Brunold, J.C.B. Hunns, M.R. Mackley and J.W. Thompson, Experimental observations on flow patterns and energy losses for oscillatory flows in ducts containing sharp edges, Chem. Engng. Sci. 44 (1989) 1227–44. M. Kleber and W. Heitzer (to Biodiesel Plants), Verfahren zur kontinuierlichen Herstellung eines als Kraft- und/oder Brennstoff geeigneten Fettsäurealkylester-

512

[59]

[60]

[61] [62]

[63] [64]

[65]

[66] [67] [68] [69]

[70] [ 71] [72]

[73]

[74]

[75]

[76]

Biodiesel science and technology gemisches sowie Verwendung des Fettsäurealkylesters als Kraft- bzw. Brennstoff, Germ. Offenl. DE 10,043,575 A1 (28 Mar. 2002). Y. Zhang, M.A. Dubé, D.D. McLean and M. Kates, Biodiesel production from waste cooking oil: 2. Economic assessment and sensitivity analysis, Bioresour. Technol. 90 (2003) 229–40. C.V. McNeff, L.C. McNeff, B. Yan, D.T. Nowlan, M. Rasmussen, A.E. Gyberg, B.J. Krohn, R.L. Fedie and T.R. Hoye, A continuous catalytic system for biodiesel production, Appl. Catal. A: Gen. 343 (2008) 39–48. A.H. West, D. Posarac and N. Ellis, Assessment of four biodiesel production processes using HYSYS.Plant, Bioresour. Technol. 99 (2008) 6587–601. D. Anderson, D. Masterson, B. McDonald and L. Sullivan, Industrial biodiesel plant design and engineering: practical experience, Presentation at the Chemistry and Technology Conference/Intl. Palm Oil Conference, Putrajaya/Malaysia (24–28 Aug. 2003). B. Gutsche, Technologie der Methylesterherstellung – Anwendung für die Biodieselproduktion, Fett/Lipid 99 (1997) 418–27. M.J.T. Reaney, P.B. Hertz and W.W. McCalley, Vegetable oils as biodiesel, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 6 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 223–57. B. Freedman, E.H. Pryde and T.L. Mounts, Variables affecting the yields of fatty esters from transesterified vegetable oils, J. Am. Oil Chem. Soc. 61 (1984) 1638–43. T. Ogoshi and Y. Miyawaki, Soap and related products: palm and lauric oil, J. Am. Oil Chem. Soc. 62 (1985) 331–5. Y. Tanaka, A. Okabe and S. Ando (to Lion Corporation), Method for the preparation of a lower alkyl ester of fatty acids, US Pat. 4,303,590 (1 Dec. 1981). L. Jeromin, E. Peukert and G. Wollmann (to Henkel), Process for the pre-esterification of free fatty acids in fats and oils, US Pat. 4,698,186 (6 Oct. 1987). P.C. Berger, Best Case Fallbeispiele der Europäischen Biodieselindustrie, Institut für Technologie und nachhaltiges Produktmanagement, Wirtschaftsuniversität Wien, Schriftenreihe Umweltschutz und Ressourcenökonomie, Band 42, Vienna (2004). Lurgi Technical Brochure No. 197e/3.91/30, Fatty Acid Technology, Lurgi AG, Frankfurt (1991). Anon., Business update, Chem. Engng. Progr. 102 (2006) 12. D.G.B. Boocock, S.K. Konar, V. Mao and H. Sidi, Fast one-phase oil-rich processes for the preparation of vegetable oil methyl esters, Biomass Bioen. 11 (1996) 43–50. D.G.B. Boocock, S.K. Konar, V. Mao, C. Lee and S. Buligan, Fast formation of high-purity methyl esters from vegetable oils, J. Am. Oil Chem. Soc. 75 (1998) 1167–72. D.G.B. Boocock, Single-phase process for production of fatty acid methyl esters from mixtures of triglycerides and fatty acids, PCT Int. Publ. No. WO 2001/012581 (22 Feb. 2001). D.M. Ginosar and R.V. Fox (to Bechtel BWXT Idaho), Process for producing biodiesel lubricants, and fuel and lubricant additives in a critical fluid medium, US Pat. 6,887,283 (3 May 2005). E. Ahn and T. Hilber, Experiences with new catalysts for production of high quality biodiesel from vegetable oils and animal fats, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007).

Industrial process technology for biodiesel production

513

[77] R.G. Stern, G. Hillion, J.-J. Rouxel and S. Leporq (to IFP), Process for the production of esters from vegetable oils or animal oils and alcohols, US Pat. 5,908,946 (1 June 1999). [78] G. Hillion, B. Delfort, D. le Pennec, L. Bournay and J.-A. Chodorge, Biodiesel production by a continuous process using a heterogeneous catalyst, Preprints ACS Symposia, Div. Fuel Chem. 48(2) (2003) 636–8. [79] C.-C. Chou, Fuel production, US Pat. Appl. 2006/063242 A1 (23 March 2006). [80] J.P. Patten, Mobile biodiesel refinery using waste cooking oil, US Pat Appl. 2005/006290 A1 (13 Jan. 2005). [81] A.H. Tullo, New life for old plants, C&EN (12 Feb. 2007), pp. 53–5. [82] Y.-M. Choo and A.-N. Ma, Plant power, Chem. Ind. (London) (2000) 530. [83] W. Thurmond, Biodiesel 2020: A Global Market Survey, Emerging Markets Online, Houston, TX (2008). [84] M.B. Wahid, Asian perspective: overview of the biodiesel industry in Asia, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [85] J. Gallehugh, Biodiesel blending techniques key to quality fuel, Biodiesel Mag. 5(7) (2008) 92–5. [86] G. Putten, The Art of Blending. Accuracy and Efficiency, Jiskoot Techn. Paper TB010-0607-2, Jiskoot Ltd, Tunbridge Wells (UK) (n.d.). [87] B.T. Ince, In-line Blending (Control Systems), Jiskoot Techn. Paper TB006-0512-2, Jiskoot Ltd, Tunbridge Wells (UK) (n.d.). [88] S. Rintoul, Meeting the challenges of biodiesel blend measurements with portable mid-infrared analyzers, Petro Industry News 9(3) (June/July 2008) 43. [89] J.W. Kram, No need to splash, Biodiesel Mag. 5(2) (2008) 56–61.

12

Analytical methods and standards for quality assurance in biodiesel production

Abstract: Fuel quality of biodiesel and its blends depends on the raw materials and chemicals used in transesterification, production process parameters and post-production conditions. Biodiesel feedstock analytical methods are outlined. Vital off-line, at-line, in-line and on-site chemical and physical analyses for production facilities and terminal services are described. The role of regulatory agencies and testing laboratories is illustrated and the current status of international biodiesel (blend) specifications is given. Biodiesel quality management sets different analytical requirements at various stages of the product life cycle, involving production, blending, transportation and storage, filling stations, consumers and car manufacturers. Fuel quality surveys have indicated that biodiesel batch-to-batch consistency needs further improvement. Key words: Biodiesel (blend) standardisation, process control, product quality management and control, biodiesel quality surveys, analytical methodology.

12.1

Introduction

High fuel quality is a prerequisite for market acceptance. Various parameters influence the quality of the biodiesel product. These include in the first place the vegetable oil source and other materials used in the transesterification process, the production process conditions as well as post-production parameters such as the content of water and sedimentation in the fuel and its storage stability [1]. Some vital analyses in the determination of the quality of biodiesel refer to the absence of free fatty acids (acid number), the complete reaction of monoalkyl esters (total-glycerol test), and removal of free glycerol (free-glycerol test), reactant alcohol (flash point) and residual catalyst (ash content). The acid value depends both on the free fatty acid (FFA) content in vegetable oil (VO) raw material and on the transesterification process. Since the source of biodiesel varies with the location and other origins (such as recycled oil), the various fatty acid profiles (chain length, degree of unsaturation and branching of the chain) do influence the biodiesel properties (see Section 14.4). Important fuel properties that are influenced by the fatty acid profile (see Table 5.1) and by the structural features of the various fatty esters are cetane number, and ultimately exhaust emissions, heat of combustion, cold flow, oxidative stability, viscosity and lubricity [2]. 514

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515

The analytical issues connected with biodiesel thus comprise various aspects. The laboratory is one of the most important sections of a biodiesel plant. Analytical measurements are important from feedstock to final biobased end-product. Reliable production and minimisation of pollution depend upon knowledge of the feedstock components and evaluation of the final product quality. Production facilities and terminal services need to ensure fuel quality (completion of transesterification, glycerol removal, etc.), while testing laboratories and regulatory agents must ensure the labelled blend levels are present. Both the pure biodiesel and the blended fuels present unique analytical challenges when measuring product quality. Chemical composition of a biodiesel blend is very complex.

12.2

Quality control of biodiesel feedstocks

Although the ASTM D 6751 and EN 14214 standards provide guidance on the methods of analysis of the biodiesel product, none of these standards address analysis of the feedstock. However, the need for methods of such analysis is apparent when considering the wide range of oil and fat-containing products which may be used as source material for biodiesel production. Oil sources vary regionally and may vary throughout the growing season, resulting in changes in oil composition. The quality of vegetable oil or fat may be assessed using methods of analysis in the Official Methods and Recommended Practices of the AOCS [3]. Tables 12.1 and 12.2 list AOCS methods for oil and fat products. Although feedstock quality testing is mandatory at biodiesel plants it is quite reasonable to defer feedstock analysis to the supplier and carry out random checks. AOCS Method CK 1-07 describes recommended practices for assessing feedstock to ensure Table 12.1 AOCS methods for vegetable oil quality parameters Chemical tests: 1. Acid value (AV) 2. Free fatty acids (FFA) 3. Oil content 4. Iodine value (IV) 5. Moisture content (KF) 6. Peroxide value (PV) 7. Saponification value (SV) 8. Soap content 9. Free gossypol

Cd 3d-63 Ca 5a-40 Ba 3-38 Cd 1d-92 Ca 2e-84 Cd 8b-90 Cd 3b-76 Cc 17-95 Ba 7-58

Physical tests: 1. Cloud point (CP) 2. Colour 3. Flash point 4. Specific gravity (SG)

Cc 6-25 Cc 13c-92 Cc 9a-48 AOCS 10a-25

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Biodiesel science and technology Table 12.2 AOCS methods for tallow and grease quality parameters Parameter

Method(s)

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14.

Cb 5-40-surplus Cc 13a-43 Cc 8d-55 Ce 1h-05 Ca 5a-40 Cd 1d-92 Ca 18c-91

Boehmer number a. Colour (FAC standard)a b. R & B Colourb Fatty acid profile Free fatty acids (FFA) Iodine value (IV) Lead content Moisture, impurities, unsaponifiables a. Moisture b. Unsaponifiable matter c. Insoluble impurities Peroxide value (PV) pH Polyethylene (PE) Rate of filtration Saponification value (SV) Titrec Total fatty acids (TFA)

Ca 2c-25 or Ca 2b-38 Ca 6a-40 Ca 3a-46 Cd 8b-90 Ca 16-75 Cd 3-25 Cc 12-59 Ce 1j-07

a

Comparison to Fat Analysis Committee (FAC) standard. R&B, refined and bleached. c Solidification point of fatty acids. b

biodiesel quality. Consistent quality control (QC) of incoming feedstocks is required for the optimal regulation of the production process, in particular in the case of multi-feedstock processing (see Chapter 9).

12.3

Biodiesel standardisation

Standards are vital for commercialisation and market introduction of biodiesel. Vehicle manufacturers also need to be able to approve vehicles to be operated using biodiesel. A standard, which is comprised of both chemical and physical tests, is meant to guarantee that all biodiesel manufactured for use as a blend for diesel engines conforms to a given purity. This ensures that the refining process is under control and produces a product that has no adverse effects on the engine, is going to run with no long-term engine components degradation, is contaminate free and is not going to pollute the air with any toxic gases or particulates. If biodiesel is to compete with fossil fuels and gain acceptance in the market, it must be manufactured to the highest performance standards. The only way this can be guaranteed is to ensure that the process is wellcontrolled by manufacturing to strict quality specifications, not unlike the diesel quality standards EN 590 and ASTM D 975. Specific legislation promoting and regulating the use of biodiesel is in

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force in various countries (Table 12.3). The German quality norm DIN 51606 is the strictest standard worldwide and is used as evidence of compliance by all manufacturers. Standardisation bodies such as the American Society for Testing and Materials (ASTM International) and the European Committee for Standardisation (CEN) have designed metrics for biodiesel (FAME) quality, in particular ASTM D 6751 (Table 12.5) and EN 14214 (Table 12.6), respectively. Compliance to American (ASTM) standards concerns B100, and B20 blends and lower; European (EN) norms address up to B5 and B100. National European standards have been replaced by EN 14214. By using sensitive instrumental techniques to monitor both the physical and chemical properties, it will help to establish biodiesel’s reputation as a high-quality, environmentally safe and viable alternative to petroleum-based fuels. Certain quality parameters (e.g. iodine value) are strictly related to the type of feedstock, while others can be influenced by the pre-treatment of the oil or fat (S-, P-content), the (trans)esterification process itself (ester content, acid value, mono-, di- and triglycerides) or any post-treatment of the biodiesel (e.g. improvement of cold-filter plugging point (CFPP) by addition of cold-flow improvers or of oxidative stability index (OSI) by addition of antioxidants). The standard specifications place restrictions in particular on several contaminants such as glycerol (free and total), residual alcohol (flash point), FFA (acid value) and residual catalyst (ash content). Certified reference standards (such as fatty acid methyl ester (FAME) and fatty acid ethyl ester (FAEE) mixtures, sulphur standards, physical standards, ASTM/EN method standards) for biodiesel analysis are now readily available (e.g. VHG Labs, Manchester, NH; AccuStandard®, USA). Analytik-Service Gesellschaft (ASG, Germany) has an established reputation for the production of reference oils. Table 12.3 Biodiesel standardisation       Country

Standards and specifications

Australia Austria Brazil Czech Republic EU France Germany India Italy Sweden US

Australian Biodiesel Standard (2003) ÖNORM C 1191 (1997) ANP 42/04 (2004) CSN 656509 for B5 (1998) CSN 656508 for B30 (1998) EN 14213 (biodiesel as heating fuel) (2003) EN 14214 (biodiesel as automotive fuel) (2003) JORF 20.8.1994 DIN 51606 (1997) ISO 15607 (for B100) UNI 10946 (biodiesel as automotive engine fuel) (2001) UNI 10947 (biodiesel as heating engine fuel) (2001) SS 155436 (1996) ASTM D 6751-08 for B100 (Nov. 2008)

518

Biodiesel science and technology

Biodiesel standards such as EN 14214 and ASTM D 6751 have been developed in close cooperation by the biodiesel and fuel producers, and by car, engine and injection pump manufacturers. To reduce the risk perceived by targeted fleet consumers, it is important that promoters of biodiesel be conversant with issues related to the performance of biodiesel blends in specific engine types, and with the impact upon engine warranties. Manufacturer warranties cover defects in material and workmanship of the engine. Those warranties extend to biodiesel as long as the fuel sold meets the specification of the fuel specified for the engine type. Biodiesel standards surpass all the engine manufacturer’s fuel specifications for warranty purposes. For detailed statements on biodiesel by major diesel engine manufacturers, visit: www.biodiesel.org/resources/fuel/factsheets/standards_and­_warranties.shtm. Daimler, Archer Daniels Midland (ADM) and Bayer CropScience are teaming up to develop production and quality standards for Jatropha biodiesel. Among the challenges facing the biodiesel industry is the international compatibility of biodiesel testing standards. The diversity among various specifications (EU, USA, Brazil) (Table 12.4) is a result of a number of factors, Table 12.4 Classification of various biodiesel specifications Similar: ∑ Sulphated ash ∑ Alkali and alkaline earth metal content ∑ Free glycerol content ∑ Copper strip corrosion ∑ Methanol and ethanol content ∑ Acid number Significant differences: ∑ Total glycerol content ∑ Phosphorus content ∑ Carbon residue ∑ Ester content ∑ Distillation temperature ∑ Flash point ∑ Total contamination ∑ Water content and sediment Fundamental differences: ∑ Sulphur content ∑ Cold climate operability ∑ Cetane number ∑ Oxidation stability ∑ Mono-, di-, triacylglycerides ∑ Density ∑ Kinematic viscosity ∑ Iodine number ∑ Linolenic acid content ∑ Polyunsaturated methyl ester

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such as: regionally available feedstock; blend stock (USA, Brazil) vs. 100% fuel for engines (EU); applicability for methyl esters only (EU) and methyl and ethyl esters elsewhere (USA, Brazil); and predominance of diesel engine types (EU: passenger cars; USA, Brazil: heavy duty). Development of worldwide biodiesel standards and international harmonisation is currently actively being pursued (International Biofuels Forum, Transatlantic Economic Council) [4]. A tripartite task force (Brazil, EU, USA) is developing internationally compatible biofuel standards [5]. Alignment of the international biodiesel standards will require considerable time and effort. Global standards would better protect original engine manufacturers (OEMs) and fuel purchasers. The half-dozen differences between the ASTM D 6751 and EN 14214 protocols for biodiesel quality are a challenge to the establishment of uniform standards. Differences between these standards are gradually disappearing. The American Oil Chemists’ Society (AOCS) has created an expert panel to deal with biodiesel analytical issues. Its activities are coordinated with ASTM and NBB (National Biodiesel Board, USA) to establish quality standards for the entire biodiesel industry. AOCS also acts as convenor for a Joint Working Group between ISO/TC 34/SC 11 (Fats and Oils) and ISO/TC 18 (Petroleum Products) to work on analytical issues affecting the production of biodiesel worldwide. ISO has no dedicated technical committee for biofuels.

12.3.1 ASTM standards D 6751 and D 7467 Biodiesel is legally registered with the US Environmental Protection Agency (EPA) and has fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments. Pure biodiesel (B100) has been designated as an alternative fuel by the US Department of Energy (DOE) and Department of Transport (DOT). The primary criterion for biodiesel quality is adherence to an appropriate standard, not unlike fossil diesel quality (ASTM D 975: Specification for Diesel Fuel Oils). The National Biodiesel Board has adopted the American Society for Testing and Materials ASTM D 6751 specification as the standard to produce B100 biodiesel. With the introduction of strict directives from the EPA and ASTM, it is becoming more and more important for biodiesel companies to comply with the regulations. All commercial-grade biodiesel has to conform to the ASTM D 6751-08 specification (Nov. 2008) if it is going to be used in diesel engines. ASTM standards for biodiesel are feedstock neutral and do not specify or limit the type of technology used to produce biodiesel. ASTM standards define what properties a biodiesel fuel must exhibit for use in a compression ignition engine. Desirable fuel properties can be controlled through feedstock blending, additives and various types of process technology. ASTM Standard D 6751 is actually made up of a compendium of 14

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ASTM standard methods for biodiesel quality evaluation (see Table 12.5) and references other methods. Of all the individual ASTM test methods that cover biodiesel analysis and specifications, probably the most important with regard to monitoring the actual refining process is ASTM D 6584, determining free and total glycerol in B100 biodiesel methyl ester by GC-FID. This standard gives the required extent of reaction. Total glycerol using ASTM D 6584 Table 12.5 Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels: ASTM D 6751-08 (Nov. 2008) Property

Test Method

 

Limits min.

Units   max.

Acid number ASTM D 664 – 0.50 mg KOH/g Alcohol controla 1. Methanol content EN 14110 – 0.20 v% 2. Flash point (closed cup) ASTM D 93 403 – K Calcium and magnesium EN 14538 – 5 ppm   (combined) Carbon residueb ASTM D 4530 – 0.050 wt% Cetane number ASTM D 613 47 – Cloud point ASTM D 2500d to be K specifiede Cold soak filtration ASTM D 7501 – 360/200g s Copper strip corrosion ASTM D 130 – No. 3 Rating   (3 h at 323 K) Distillation temperature, ASTM D 1160 – 633 K   T90 AETc Flash point (closed cup) ASTM D 93 366 – K Free glycerol ASTM D 6584 – 0.020 wt% Kinematic viscosity, ASTM D 445 1.90 6.0 mm2/s   at 313 K Oxidation stability EN 14112 3 – h Phosphorus content ASTM D 4951 – 0.001 wt% Sodium and potassium EN 14538 – 5 ppm   (combined) Sulphated ash content ASTM D 874 – 0.020 wt% Sulphur content ASTM D 5453 – 15 or 500f ppm Total glycerol ASTM D 6584 – 0.240 wt% Water and sediment ASTM D 2709 – 0.05 v% Workmanship Free of undissolved water, sediment and suspended matter Bold = BQ-9000 Critical specification testing once production process under control. a One of the following must be met. b To be run on 100% sample. c Atmospheric Equivalent Temperature, 90% recovered. d Optional: ASTM D 7397. e ~276–285 K. f The limits refer to S15 or S500 grades. g Limits refer to summer and winter (T < 261 K) biodiesel.

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measures the level of free glycerol plus any unreacted oils or fats (or bound glycerol), the latter being equal to the glycerol portion of the residual mono-, di- and triglycerides in the biodiesel. These indicators will denote how efficient the transesterification reaction is proceeding, or has proceeded. ASTM D 664 is the standard reference method for measuring the acid number of both ASTM biodiesel and petroleum-derived diesel. This potentiomentric method is characterised by acceptable repeatability and mediocre reproducibility, but lacks information on accuracy. The non-aqueous colorimetric titration according to ASTM D 974, using KOH in i-PrOH as the titrant and p-naphtholbenzein as indicator and originally designed for (coloured) petroleum products, is a good replacement for ASTM D 664 for evaluating the acid number compliance of biodiesel samples with accuracies within 3.3% [6]. See also Section 12.5.4. The cetane number (CN) test procedure according to ASTM D 613, which essentially dates back to work by Baxley and Rendel [7], is complex, and inherently involves considerable uncertainly. Several successive modifications to this cumbersome single-cylinder cetane engine standard test have been suggested. The constant volume combustion apparatus (CVCA) determines CNs more rapidly, with greater experimental ease and with higher accuracy and reproducibility [8–10]. The Ignition Quality Tester (IQT™) is a further automated CVCA apparatus, which allows CNs to be obtained which are fully competitive and more accurate than those derived from ASTM D 613 while using considerably less fuel sample [11–15]. The Ignition Quality Tester is being developed into an ASTM method. As the determination of cetane number requires equipment which is not always available in every laboratory, there have been various attempts to calculate CN or to derive an alternative parameter that could provide an indication of the ignition quality. Calculated cetane index (CCI) and diesel index are other parameters which indicate the quality of diesel fuel. While the cetane index, calculated from fuel density and volatility according to ASTM D 976, is a useful simplification for fossil diesel, it is less appropriate for biodiesel and its use should be discouraged (see also Section 12.4.3). Spectroscopic portable fuel analysers (mid-IR and NIRS) for testing biodiesel on cetane number are described in Section 12.5.2. When the limits indicated in Table 12.5 are met, biodiesel can be used in modern engines without modification while ensuring the engine’s reliability and durability. ASTM D 6751-08 (Nov. 2008) includes a trace metals specification for Na/K and Ca/Mg (EN 14538), whereas also a 3 h oxidation stability requirement (Rancimat test) has recently been introduced (cf 6 h in EN 14214). Biodiesel stability requirements vary by geographical region. The oxidation stability requirement is likely to lead to increased use of antioxidant additives. Some remaining differences between the ASTM and EN standards are the means of carbon residue testing (on B100 in ASTM

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D 6751 and on a 10% distillation residue in EN 14214), and a particulate contamination specification. Feedstock and/or process related sediments and haze in biodiesel determine non-compliance with official biodiesel standards, fuel filter and injector blockages, and sedimentation at the bottom of biodiesel storage tanks. Contaminants comprise steryl glycosides (SGs), bound and free glycerol (MG, DG, TG, GL), free sterols, soaps and inorganic impurities. Current analytical methods for their evaluation are EN 12662 (Total contamination at 313 K, 24 ppm), ASTM D 2709 (Water and Sediment, max. 0.05 vol%), ASTM D 2068 (Filter blocking tendency) and the state of Minnesota’s Cold Soak Filter (CSF) test. Precipitates forming in soy biodiesel above the cloud point were at the origin of the Minnesota filter plugging experience (see Section 12.4). Options not in ASTM D 6751 include Karl Fischer moisture (ASTM D 6304); Bromine index (ASTM D 457); Simulated distillation (ASTM D 2887); Biodiesel in blended fuels (EN 14331); Density (ASTM D 4052); Pour point (ASTM D 97); Iodine number (EN 14111); Lubricity (ASTM D 6079); and FAME (EN 14103). As the synchronisation of biodiesel standards moves forward across the world – most notably between the ASTM D 6751 and EN 14214 protocols – a concerted effort is under way in the US to improve ASTM D 6751. Further adjustments of ASTM D 6751 may consider monoglycerides, ash contamination, and water and sediments. It is foreseen that the ASTM standard will resemble the EN standard within the next few years while maintaining feedstock neutrality. Laboratory testing to ASTM D 6751 is a reliable way of ensuring biodiesel is on spec, but is not cheap and gives no instant results. Determination of the kinematic viscosity in accordance with ASTM D 445 (Ubbelohde viscometry) is a time-consuming test to perform in the laboratory; however, recently (semi-)automated systems have become available, which fully comply with ASTM D 445 in every respect. These lower-cost instrumental methods can provide measurement cycle times of 3–5 mins. The advantages of kinematic viscosity measurement in oil analysis have been discussed [16]. Under ASTM D 6751-08, biodiesel (B100) that meets this specification may be used in finished diesel fuel blends with petroleum diesel at up to 20 vol% (B20). In June 2008, ASTM International approved new stand-alone B6 to B20 biodiesel blend specifications (ASTM D 7467-08: Standard Specification for Diesel Fuel Oil, Biodiesel Blend (B6 to B20)) for on- and off-road diesel engine use in order to build OEM acceptance and give regulators a tool to enforce fuel quality. Companies can now confidently design engines for finished fuel blends. In the absence of these fuel specifications uniformity of quality in biodiesel blends on the US retail market was not assured. With the passage of this specification, biodiesel used in B20 blends and lower can now be considered a proven fuel. Standard ASTM D 7467 mirrors the ASTM D 975 diesel standard with a few modifications (as to higher distillation

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temperature and tests for a stability parameter and acid number). Although the biodiesel (B100) specification can be used, blends of over 20% biodiesel with diesel fuel should be evaluated on a case-by-case basis until further experience is available. ASTM International recently (Nov. 2008) also issued three other standards pertaining to fuel blends up to B5 for on- and off-road diesel applications (ASTM D 975-08a), biodiesel in fuel oils up to B5 used for home heating and boiler applications (ASTM 396-08b), and a cold soak filtration test (ASTM WK 22403). Work Item ASTM WK 22403 covers the determination of filtration time after cold soak of the suitability for a biodiesel (B100) blend stock for blending with light–middle distillates to provide adequate low temperature operability performance to at least the cloud point of the finished blend. The CSFT method recently received an official number – ASTM D 7501–09. Cold soak filtration testing, which consists of chilling the sample for a specified time and then allowing it to warm to ambient temperature prior to filtering in a modified ASTM D 6217 (Particulate Contamination in Middle Distillate Fuels by Laboratory Filtration) procedure, measures the time (in sec) it takes for cold soaked biodiesel to pass through two 0.7 mm filters and the amount of particulate matter (mg/L) collected on the filter. ASTM D 6217 was required already in Minnesota and Colorado as from July 2007. The lengthy test (36 h) is poorly reproducible and repeatable. There is no correlation between cloud point and CSFT. The new cold soak filtration test (< 360 sec for summer biodiesel; < 200 sec for winter biodiesel), associated with an official AOCS method for SG in biodiesel by GC, aims at controlling minor contaminants. Adding the empirical CSF test to the mandatory annex in the ASTM D 6751 specification for B100 biodiesel blend stock addresses the occurrence of gelling (i.e. formation of precipitates such as unconverted MGs and DGs from falling out of B20 and lower blends at temperatures above the cloud point), which causes filter plugging and damages biodiesel’s reputation as a transportation fuel. The test may not catch all of the insoluble impurities in biodiesel and is strongly affected by steryl glycosides (SGs) and soaps [17]. What compounds from which feedstocks are causing CSFT failure is still largely unknown. Poor filtration can be related to choice of feedstock, as well as incomplete glycerol removal during processing. It may also indicate the B100 product was subjected to low temperatures (below pour point). High filtration times indicate the potential for fuel filter plugging. Greenline Tea FASTRACK technology is designed to remove contaminants present in biodiesel that can cause the fuel to fail ASTM D 7501’s CSF test. In freezing climates remedies are heat trace on storage tanks, blend and piping equipment (distributors/ blenders) or installation of heated filter housings (end users). US biodiesel blend specifications thus now cover up to B5 in home heating oil (ASTM D 396-08b), up to B5 in diesel fuel (ASTM D 975-08a) – without

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the need for content labelling –, and up to B20 (ASTM D 7467-08). ASTMcertified B5 blended fuel is UL approved. With the specifications in place, all that is necessary is to ensure that these blend standards are being utilised, and testing is done to ensure compliance. Support from engine and equipment manufacturers is increasing. All major OEMs support B5 and lower blends, provided they are made with biodiesel meeting ASTM D 6751 specifications. Among light-duty vehicle manufacturers, Chrysler has also approved use of B20 by its fleet customers who follow specifications for fuel quality. General Motors approves the use of B5 in all of its diesel powered trucks and vans and offers a special equipment option for fleets to operate vehicles on B20. Cummins, Caterpillar, Case IH, New Holland and John Deere approve use of B20 or higher blends in the majority of their engines and equipment. As from 1 June 2006 any refiner desiring to sell diesel fuel in the US must also meet the new ultra-low sulphur requirements outlined by US EPA of 15 ppm sulphur in diesel fuel. NIST reference standards are available to comply with the legislation. EPA offers guidance to producers [18]; the agency has the authority to act against producers of off-spec product.

12.3.2 European Norm EN 14214 The European Union leads the way in environmental protection and implementation of biodiesel production. Biodiesel is a mature fuel with a strictly specified qualitative minimum standard as described in EN 14214 for FAME as an automotive fuel for diesel engines and in EN 14213 for FAME as a heating fuel. These standards define the worldwide highest requirements for biodiesel. CEN round-robin tests have allowed determination of repeatability and reproducibility of the test methods. EN 14214 was developed in CEN Technical Committee 19 (2001/02). EN 14214 (2003) includes 26 quality parameters (Table 12.6); some of these are regulated in order to control the production process and ensure good conversion of the fatty acids into FAME, while other parameters depend on the feedstock used. For example, acid number is a measure of acids in the fuel, which emanate from two sources: acids utilised in the production of biodiesel that are not completely removed in the production process; and degradation by oxidation. For biodiesel blends the acid number will change as a result of the normal oxidation process over time. Once purchased, biodiesel fuel blends that will not be utilised immediately should be monitored for changes in acid number as an indicator of fuel degradation. In principle, EN 14214 (based on the German DIN V 51606 and the Austrian standards ÖNORM C 1190 for RME and ÖNORM C 1191 for FAME) defines biodiesel as FAME (not faee) without reference to a specific raw material; however, the limits defined in the specification essentially reflect those of

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Table 12.6 European Union Draft Standard for Biodiesel: EN 14214 (2003) Property

Test method



Limits min.

Units

Typea

max.    

Acid value EN 14104 – 0.5 mg KOH/g Group I metals (Na+K) EN 14108/EN – 5 ppm   14109 Group II metals (Ca+Mg) EN 14538 – 5 ppm Carbon residue (on 10% EN-ISO 10370 – 0.3 wt%   distillation residue) Cetane number EN-ISO 5165 51 – d d K CFPP EN 116 Copper strip corrosion EN-ISO 2160 Class 1 Class 1 –   (3h @ 323 K) Density @ 288 K EN-ISO 3675/ 860 900 kg/m3   EN–ISO 12185 Diglyceride content EN 14105 – 0.2 wt% Ester content EN 14103 96.5 – wt%   (biodiesel yield) Flash point EN-ISO 3679 393 – K Free glycerol EN 14105/EN – 0.02 wt%   14106 Iodine value EN 14111 – 120 g I2/100 g Kinematic viscosity EN-ISO 3104/ 3.5 5.0 mm2/s   @ 313 K   ISO 3105 Linolenic acid ME EN 14103 – 12 wt% Methanol content EN 14110 – 0.2 wt% Monoglyceride content EN 14105 – 0.8 wt% Oxidation stability EN 14112 6 – hours   @ 383 K Phosphorus content EN 14107 – 10 ppm b Polyunsaturated – 1 wt%   ( ≥4 double bonds) ME Sulphated ash content ISO 3987 – 0.02 wt% Sulphur content EN-ISO 20846/ – 10 ppm   EN-ISO 20884 c Thermal stability Total contamination EN 12662 – 24 ppm Total glycerol EN 14105 – 0.25 wt% Triglyceride content EN 14105 – 0.2 wt% Water content EN-ISO 12937 – 500 ppm

N, P P P P N N P N P P P P N N N P P N P N P P N P P P P

a

Property related to the nature (N) of the raw material or to the quality of the process (P). b Suitable test method under development. c Suitable test method and limits to be proposed by CENT/TC 19. d Various classes for temperate (253–278 K) and arctic (229–253 K) climates.

RSO. (In contrast, ASTM D 6751 is designed to be feedstock neutral, whereas the JIS standard reflects CNO). In Germany practically only rape biodiesel is offered on sale at its public filling stations. This is because several car manufacturers only approve rape methyl ester (RME) for operation with

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Biodiesel science and technology

biodiesel. Mercedes Benz experience suggests that biodiesel with IV > 115 g I2/hg is not acceptable because of excessive carbon deposit. As biodiesel production is not only limited to rapeseed oil but can be applied to any plantderived oil as well as animal fats, standardised quality control is essential. This has been documented in the EN 14214 norm which also takes into account that biodiesel as a natural product is subject to limited shelf-life. EN 14214 combines all analytical procedures – for the most part chromatographic and spectroscopic measurements – and specifies under which conditions these methods are to be applied for biodiesel quality control. As EN 14214 is very restrictive in its limits, some oil crops that would be suitable in regard of their fatty acid content are excluded from FAME production because they exceed these limits (in particular IV, stability and CFPP in wintertime). The European EN 14214 sets the specifications and test methods for FAME to be used neat as automotive fuel for diesel engines, or as an extender for automotive fuel for diesel engines, in conformity with the European Automotive Diesel Standard (EN 590). In the EU, diesel containing up to 7% biodiesel is considered as diesel at all effects and is covered by normal diesel standard EN 590 (as from Apr. 2009). The US ASTM D 6751 specifies the standards for biodiesel (100%, denoted as B100) for use as a blend component with diesel fuels. The European norm EN 14214 tends to be stricter than the American ASTM D 6751 standard, either displaying more stringent limits (e.g. on viscosity, cetane number and copper strip corrosion) or providing limits on parameters which are not regulated in the ASTM norm at all (e.g. organic contaminants, total contamination, ester content, linolenic acid methyl content, polyunsaturated methyl esters, CFPP, IV and density), whereas ASTM D 6751 emphasises distillation temperature and filterability (absent in EN 14214). The other major difference between these standards is the preferred testing methods. EN 14214 contains a few parameters concerning the same properties. Consequently, deletion of the parameters methanol content, sulphated ash content and total glycerol has been proposed [19]. Suggestions have also been made concerning revision of the prescribed limits of other parameters, in particular extension of IV up to 130 g I2/100 g. As some tests methods have problems in precision or application other updates are necessary and currently under consideration. It is predicted that a future EN 14214 standard will permit more feedstocks or at least permit blending of other oils and fats in greater proportion.

12.4

Biodiesel quality management

Biodiesel production only appears to be an easy process. Reliable product output is essential, as is adherence to (inter)national norms and standards

Analytical methods and standards for quality assurance

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(see Section 12.3). Biodiesel quality control is challenging, especially if we consider that many (small to medium) production plants are not well equipped with analytical facilities. Uncontrolled home-brewing plants are unlikely to generate the highest quality biodiesel from their usually crude feedstocks. The product will most probably contain detrimental impurities like residual alcohol, moisture, unreacted vegetable oil (triglycerides), incompletely reacted mono- and diglycerides, free fatty acids and trace metals from the catalyst. Commercial manufacturers must ensure that the manufacturing process quality is well controlled in order to produce on-spec bulk biodiesel fuel for blending with petroleum products. The fuel quality of biodiesel depends on several factors including feedstock quality, the fatty acid composition of the parent oil or animal fat, the production process and other materials used in the process. It is important to test the fuel to ensure the quality of the biodiesel at the time of delivery, monitor the consistency of the biodiesel from batch-to-batch production and check the biodiesel quality for any deterioration during storage. Lack of quality control over the storage process can lead to impurities finding their way into fuel tanks. Most fuel quality problems occur post-production. A quality management (QM) system therefore needs to cover the whole life cycle of biodiesel from raw material to filling station (and beyond): ∑ ∑ ∑ ∑ ∑ ∑

production (including feedstock selection and quality, production control, laboratory testing, and product quality); blending; transport and storage conditions (biodiesel stress, tank control); filling stations (external quality checks); consumers (complaints; problem solving); and original equipment/car manufacturers (technical working groups).

Producers can set up their own QC laboratories for analysing biodiesel according to the standards. This requires significant capital investment ranging from US$0.5–1.5 M. Carrying out the full suite of ASTM D 6751 or EN 14214 tests can be costly, particularly because cetane is required, and the regularity with which these tests are needed can prove particularly costly for the smaller producer. Samples can also be sent to a third-party laboratory at a cost of approximately US$1000 per batch. A testing budget of US$10 000 is required per 100 kgal produced (or an analysis cost of US$0.10/gal) [20]. Producers could also purchase equipment to perform the critical test parameters themselves, e.g. density, viscosity, flash point, water and acid content. These tests provide an indication of fuel quality and sustainability of use. However, regardless of how a producer chooses to test its fuel, all biodiesel has finally to meet the full requirements of ASTM D 6751/EN 14214 for sales purposes to the end-user. Biodiesel is more sensitive to environmental factors than petroleum

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products. For example, problems that occur in storage and transit arise from no single cause, but rather from a synergistic effect produced from a variety of conditions: chilling (B100 has ‘thermal memory’); formation of steryl glycosides; elevated moisture; and near-specification levels of bound glycerol (mono-, di- and triglycerides). As a maturing industry, biodiesel needs compliance to standards for its reputation and credibility to protect the consumer, to encourage investment and to create confidence (manufacturer, supplier, user, government). The main German producers and distributors of biodiesel have joined forces in the ‘Arbeitsgemeinschaft Qualitätsmanagement Biodiesel eV’ (AGQM – Association for the Quality Management of Biodiesel). AGQM, which nowadays comprises most of the German biodiesel business, has set up a controlled QM system ensuring a high and long-term unvarying fuel quality [21]. The mandate of AGQM also includes setting up quality standards for biodiesel, offering assistance to members in installing (minimum) QC systems for production and delivery, and organisation of round-robin tests, audits and workshops. Field surveys of biodiesel quality are a common way of obtaining an overview of standard qualities. In Germany, UFOP first and AGQM next have carried out regular quality surveys as from 1997. Complaints about German biodiesel quality, related to filter blocking and damaged injection equipment, date from 1999. Practical experience (2003) has indicated that stability is most difficult to guarantee at the pump. With plummeting retail sales in spring 2009 the program has temporarily been halted. AGQM has also published a list of 13 biodiesel stabilisers that fulfil no-harm criteria for diesel engines (www.agqm_biodiesel). Fuel quality surveys of commercially available biodiesel (B100) and B20 blends conducted by NREL in the US in 2004–2006 have resulted in significant concern for the local biodiesel industry [22–24]. Of the 27 B100 samples collected at terminals in 2004, 85% did meet all the requirements of ASTM D 6751-03a (the version in effect at the time of sampling). Typical B100 and B20 samples exhibited less than 1 h and 2 h Rancimat (EN 14112) induction time, respectively, in the oxidation stability test. However, at that time there was no oxidation stability specification for biodiesel in the US. Many of the B20 samples – stored for about 6 months – showed high peroxide levels and low levels of water interfacial tension. Moreover, a serious blending problem was detected. Figure 12.1 shows unacceptable blending inaccuracies in 50 splash-blended B20 samples. Only 32 samples were nominally B20 (18–22% biodiesel), whereas 18 samples ranged from 7–98%. In fact, 2% biodiesel blends in the US have been found to contain anywhere between 0% and 8% biodiesel. In the 2006 survey, 59% of B100 samples (again collected at terminals and wholesalers) failed to meet the specifications, in particular by exceeding the allowable total glycerol and by not meeting the flash point specification.

Analytical methods and standards for quality assurance

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Percent biodiesel (FTIR method)

100

80

60

40

20

0 0

5

10

15

20 25 30 35 Sample no.

40

45

50

55

12.1 Percent biodiesel content for B20 quality survey samples (Source: NREL [22]).

EN 14112 oxidation stability averaged about 1 h with a peroxide content of 157 ppm. The results have raised considerable concern about the quality of B100 produced and distributed in the US during 2006. Small-scale biodiesel producers most often did not produce fuel meeting the standards or did not adequately address the process waste streams. Also another recent study (published Feb. 2008) by WHOI (Falmouth, MA) still found incorrectly calibrated biodiesel blends. The Woods Hole study [25] – based on blends from more than 20 US distributors and small retailers – found B20 blends to be correct in only 10% of the stations sampled, with the remaining samples varying from 10–74% biodiesel. This is not unlike the previous NREL study involving large-scale retailers. When blends deviate to the higher ranges, such as B74, they could damage gaskets and hoses in older vehicles. The observed variance may stem from inadequate mixing, measurement mistakes or mathematical error. A likely source of error is splash blending, i.e. pouring two fuels into a container. Because biodiesel is denser than petroleum-based fuel, it has a tendency to settle at the bottom of a container if not properly mixed. As the biodiesel industry grows, a transition from splash blending with inadequate mixing to in-line blending should be considered to eliminate this serious problem (see also Section 11.5). Existing refinery infrastructure overcomes the blending problems. Mixing challenges determine the need for on-site blend ratio methods [26].

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Biodiesel science and technology

It is encouraging, though, to notice that the 2007 NREL fuel quality survey of 56 samples collected at production level found that 90% of US biodiesel did meet the industry specifications [23], as compared to only 41% in the NREL 2006 survey. In particular, 94% of the 15 large producers’ samples (accounting for 89% market share) were on-spec (ASTM D 6751), against 68% of the 16 samples of medium producers (10% market share), and a disturbing 28% only of samples from 25 small plants (accounting for 1% market share). In the most recent NREL B20 quality survey (sampled from spring to summer 2008 from fleets using B20 and pumps labelled B20) again only 60% was nominally B20 (i.e. B18–B22). While two of the 32 samples contained biodiesel percentages far exceeding 20%, most off-spec samples contained too little biodiesel, most commonly B2, B5 and B11. A total of 74% of the samples passed the new B20 spec’s stability test for induction time (8.4 h on average). Although these latest B20 survey results show improvements over those of 2004, still considerable caution is required in equating blend advertised and blend delivered. Sub-standard quality of some 50% of biodiesel produced in the US in the last few years has seriously damaged the image of the industry. Quality is directly related to liability issues, as shown by off-spec products in MN, TN, WA and other states. Bad product can cause harm to the diesel engine (see Section 14.4.4) and has made engine manufacturers wary of extending warranties to high ratios of biofuels. Table 12.7 lists the primary concerns for engine performance and the associated official test methods. The last column lists potential test options, some of which are different from the ASTM method and may be quicker or simpler. Filter plugging problems in vehicles using B20 or lower biodiesel blends in the state of Minnesota made headlines during the winter of 2005–06 (and again in January 2009). The effect of minor components in soy biodiesel (MG, steryl glycosides, soap and water) on cloud point and filterability was investigated [27]. MG (especially above 0.6%) had a significant negative impact on CP; a filter test response was particularly sensitive to the glycosides (SGs) and soaps. On the whole, the biodiesel industry has an unfavourable quality control history, and in the present turbulent market conditions a shakeout of substandard (especially smaller) producers would not be surprising. As a response to the persisting quality problems BQ-9000 was set up as the US National Biodiesel Accreditation Program (and overseen by NBAC) for producers and distributors of biodiesel. The programme is a combination of the ASTM D 6751 standard for biodiesel and quality systems for storage, sampling, testing, blending, shipping, distribution and fuel management practices. While ASTM D 6751 defines minimum requirements for biodiesel that is ‘fit for purpose’ for blending up to 20% with petrodiesel, the voluntary BQ-9000 NBB/ Canadian Renewable Fuels Association fuel quality enforcement programme

Parameter

Testing for

Engine problem

Official test method

Test options

Residual glycerol Free and total glycerol

Injector coking, filter plugging, shortened shelf-life, sediment formation

ASTM D 6584 (GC)

GC or IR

Residual catalyst Sulphated ash

Injector plugging, filter plugging, ring wear issues with lubricant

ASTM D 874 (gravimetric)

Gravimetric

Residual alcohol Flash point or % methanol

Degradation of some plastics and elastomers, corrosiveness, lower flashpoint (fire safety)

ASTM D 93 (Pensky-Martens Pensky-Martens Closed Closed Cup Tester) Cup Tester, GC or IR

FFA Acid number

Poor cold-flow properties, deposits ASTM D 664 (potentiometric Titration or IR on injectors and in cylinders titration)

Water and sediment Water and sediment Accelerated oxidation, filter plugging Cloud point Bacterial growth   (in storage tanks)

ASTM D 2709 (centrifuge)

Reduced fuel flow in ASTM D 2500 (visual test) cold climates Clogs filters, ASTM D 6974-04 (membrane deteriorates fuel filter)

Centrifuge Cooling system, visual test Membrane filter   procedure

Analytical methods and standards for quality assurance

Table 12.7 Ensuring product quality at the buyer’s end    

531

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Biodiesel science and technology

requires D 6751 compliance on every lot (see also Table 12.5). BQ-9000 has become the premier quality designation in the industry. In Feb. 2008 27 BQ-9000 accredited manufacturers were registered (out of a total of 61 active producers), representing about 75% of US biodiesel production. Buyers should insist on a complete Certificate of Analysis (COA) that guarantees that the fuel meets ASTM D 6751 or EN 14214 requirements or buy from a BQ-9000 or AGQM certified producer. Renewable Energy Group®, Inc. (REG, Ames, IA) has trademarked its own product qualifications for biodiesel at a level that goes above and beyond the ASTM requirements regardless of feedstock. Higher quality specifications include reduced and total glycerin levels, reduced acid number, sulphur content, free water and sediment. REG’s specifications also require that internal tests are performed which are not currently required by ASTM. These include tests for MGs, DGs, TGs, for total biodiesel moisture, and a cold soak filtration test (which indicates how well the biodiesel will perform in cold weather). REG offers products with improved oxidation stability and enhanced purity compared with other B100 biodiesels on the market (see Table 12.8), thus meeting different customers’ needs and budgets. Also ExxonMobil’s biodiesel specifications (for blending) go beyond ASM D 6751/7467 standards. For further information about biodiesel fuel quality, consult also the website www.biodiesel.org/resources/fuelqualityguide.

12.4.1 Process control Whereas petroleum is highly regulated (i.e. tested to specification during production and transportation to market), produced in enormous quantities and transported via pipeline, it is subject to relatively small variations during its production process. On the other hand, biodiesel is much more loosely regulated, typically produced in smaller quantities (thus rendering testing more expensive) and subject to various quality-affecting factors including the feedstock used and the way it is transported to the market (tanker, truck or railway). Moreover, some positive characteristics of biodiesel, such as its lower emissions profile and non-toxic nature, are also responsible for its notorious variation in quality. It is biodegradable and more susceptible to incidental chemical interactions and microbial contamination. Table 12.8 Renewable Energy Group®, Inc. advanced biodiesel product line Property

Biodiesel grade

 

REG-9000-1

REG-9000-5

REG-9000-10

Cloud point (K) Cetane number OSI (h)

273–275 47–50 3–6

277–279 50–53 5–8

281–285 53–59 7–10

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533

Process control, optimised product output and biodiesel quality require adequate accuracy and reliability, matched with economy, accessibility and ease-of-use. Production facilities are generally concerned with high FAME content materials (B100). Biodiesel processing and quality are closely related. The processes used to refine the feedstock and convert it to biodiesel determine whether the fuel will meet the applicable specifications. The production process must be resilient enough to accommodate a wide range of operating parameters to adjust to feed variations. Monitoring the process parameters enables the controlled use of expensive substances. On-site concentration measurement allows exact dosage of raw materials. Producers of biodiesel require both a way to perform quality control on their raw materials (including checks for initial free fatty acids) and for completion of the transesterification reaction. Although any kind of vegetable oil – virgin or used – may be transesterified, the final product is not necessarily within biodiesel specifications. High conversion rates are required in order to meet the (inter)national quality specifications. Testing for the completeness of transesterification of glycerol esters to fatty acid methyl esters via quantification of the remaining mono-, di- and triglycerides represents an important aspect of daily process control. This procedure simultaneously determines the amount of free glycerol in biodiesel. Biodiesel monitoring technology may take advantage of a wide range of laboratory, plant-based and portable instruments for numerous standard test methods including analytical instruments for in-process analysis equipment and quality control. Most biodiesel producers want the ability to conduct quality testing during the manufacturing process rather than risking unnecessary waste by testing after the fact. Continuous monitoring of a biodiesel plant also avoids the need for manual batch testing for quality assurance. The need for streamlined production processes has spiked interest in more efficient and less costly on-line analytical methods which provide real-time information, instead of the traditional, slow and expensive wet-chemical reference methods and physical testing. Explosion-proof on-line biodiesel analysers (testing fatty acids, water and iodine number) are now available for validating the product quality at completion of the manufacturing process or controlling blends. For example, rapid monitoring of transesterification and assessment of biodiesel fuel quality are possible by means of fibre-optic probe NIRS [28]. The Aspectrics Biodiesel Quality Analyzer 1000 (BQA 1000), based on encoded photometric near-infrared (EP-NIR) technology, enables users to carry out at-line biodiesel production quality control and to analyse the biodiesel production process in real time from start to finish measuring concentrations of water, methanol, total and bound glycerol, and free fatty acids [29] (see also Section 12.5.2). The small–medium size commercial biodiesel producer Bionic Fuels (UK) has been involved in testing and assisting in the development of a biodiesel

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specific field test kit (Kittiwake, UK) designed to give key data throughout the production cycle. The key point indicators of water content, total acid number, density and viscosity give an early indication of off-spec batches or production trends. Manufacturers can optimise the ratio of chemicals used, gain real-time batch-to-batch data, ensure quality of base stocks; refine and troubleshoot production and ensure end-product quality and consistency. Endusers can ensure quality of delivered fuel, monitor batch-to-batch consistency, check stored biodiesel for deterioration over time and gain confidence in the producer. Biodiesel process and quality control brings about a distinct set of challenges. The consistent quality control of incoming feedstocks with high-precision measuring instruments ensures the optimal regulation of the production process. Monitoring the process parameters enables the controlled use of expensive substances. On-site concentration measurement allows the exact dosage of raw materials. Fast process and quality control schemes may be based variously on density, viscosity and refraction index measurements [30], mid-infrared [31] and NIRS [28]. Simple density, viscosity and refraction index measurements in various stages of the biodiesel manufacturing process allow: ∑ ∑ ∑ ∑ ∑ ∑ ∑

quality control of incoming feedstocks; filling volume determination; determination of acid and base concentration; monitoring of concentration of methanol and catalyst; monitoring the transesterification process; quality control of biodiesel; and quality control of glycerol (Fig. 12.2) [30].

Viscosity provides essential data for all pumping, stirring and mixing operations. In the final stage of production, quality control in accordance with all applicable standards is essential. Testing biodiesel for every specification in the standard is a lengthy and extremely expensive process. Table 12.9 details the essentials of process monitoring, product verification and blending control. Testing allows for the development of process data that can be used to improve production. For example, testing is recommended for proper acid neutralisation and the removal of soaps that cause foaming and fouling problems. Testing can also optimise the flash evaporation steps, any required distillations and new technology for the wash portion of production. The following are some illustrative examples of process control. In the final equilibrium of the ethanolysis of RSO, 2% and 4% di- and monoglycerides were reported at an ester yield of 94%, i.e. well beyond the limits of EN 14214 [32]. On the other hand, the reported values for pilot plant produced B. carinata biodiesel (yield 97.1%) were well within these limits (except for density and possibly linolenic acid content) [33].

Analytical methods and standards for quality assurance Vegetable oil grease A

C

Pre-treatment

Acid

535

Recycled grease recycled oil B Pre-treatment

D Catalyst methanol

Raw glycerin refining

Transesterification E Biodiesel refining F

G Glycerol (pharmaceutical)

B Biodiesel

Key: A quality control of incoming feedstocks – viscosity, density; B filling volume determination – viscosity, density; C determination of acid and base concentration – density; D monitoring concentration of methanol and catalyst concentration – density; E monitoring transesterification – density; F quality control of biodiesel – viscosity, density; G quality control of glycerol – density, refraction index.

12.2 Biodiesel process control using density, viscosity and refraction index measurements (after ref. [30]). Table 12.9 Biodiesel process control   Process monitoring: ∑ Oil feedstock quality characterisation ∑ Progress of transesterification and by-product monitoring ∑ Identification of end-points for improved production yields ∑ Assessment of product quality prior to decanting or blending Product verification: ∑ Prevention of cross-contamination during line transfers ∑ Screening of the final product prior to full EN/ASTM quality assay ∑ Verification of product quality before rundown to tankage Blending control: ∑ Measurement of pre-assay blend ∑ Measurement of biocontent (% FAME) in diesel blends ∑ Coverage of point-of-use blending

12.4.2 Biodiesel product quality control Biodiesel manufacturers need ideally to be able to ensure the quality of the base feedstock at the time of delivery, optimise the ratio of chemicals used, refine and troubleshoot the manufacturing process and guarantee the quality and batch-to-batch consistency of the end product and stored biodiesel in just minutes. Options for fuel quality testing are several (Table 12.10).

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Biodiesel science and technology

Table 12.10 Options for fuel quality testing Characteristics Instrumentation  

Field test kits Portable

Multifunctional Laboratory

Cost Ease of use Fuel quality   indicators Results

Inexpensive US$3–25a Simple Various

Cheap US$3000–25 000b More difficult One

Medium n.g. Simple Several

Go/no-go

Nearly lab-quality Accurate

a

High US$4000–70 000b Technical staff One High quality

Per test. Per instrument.

b

Product quality is closely linked to measurement quality. Specially developed biodiesel test kits, designed to complement laboratory test results, allow rapid determination of a variety of key indicators of fuel quality, such as water content of stocks of oils and biodiesel, acid number of stock oils (for catalyst optimisation) and density, viscosity, microbial contamination, glycerol content, percentage biodiesel in diesel blend, and visual quality check of biodiesel in a go/no-go manner (no exact measurements). The recently developed BQP-02 kit (Sigma Aldrich Co.) for glycerol determination by enzymatic analysis allows determination of both free and total glycerol in a very easy and precise way. This method is now under evaluation by the National Biodiesel Accreditation Committee (NBAC, USA) and may eventually be considered as an alternative to ASTM D 6584. Small, portable laboratory instruments are often typically focused on one particular fuel quality characteristic. Several multifunctional instruments use infrared technology; typical key indicators include free and total glycerol, biodiesel content, water content, free fatty acids and cloud point. Like field test kits, these instruments do not use the ASTM testing protocols. On-site field portable FTIR biodiesel analysers allow determination of fuel composition and predict properties such as cetane number, distillation points (like T 90) and vapour pressure (see Section 12.5.2). Laboratory instruments are the ultimate testing option allowing for high-quality results derived according to official ASTM protocols. All biodiesel for sales purposes needs to comply with ASTM D 6751/EN 14214 protocols.

12.4.3 From producer to user Table 12.7 shows important product quality parameters for the end-user. The quality of biodiesel fuel produced to specification can change at any point between producer and fuel injector. Bulk purchasers and end-users may wish to ensure the quality of the biodiesel at the time of delivery whilst

Analytical methods and standards for quality assurance

537

monitoring the consistency of the biodiesel from batch to batch and check stored biodiesel for any deterioration over time. As shown in Section 12.4, a major challenge in introducing biodiesel blends to the diesel pool is determining how to dependably and simply quantify the amount of biodiesel present. The detection of blend levels is an important aspect of biodiesel analysis. Knowing the biodiesel/diesel blend ratio is relevant to distributors, engine manufacturers, fleet operators and regulatory agencies. Many engine warranties are not valid above a specified biodiesel percentage and fleet operators need to know the blend ratio to ensure compliance with the warranty terms. The volumetric blend tax credit at the blender level also makes revenue services concerned about the percentage blend. There are important economical justifications for an accurate biodiesel concentration determination. With the widespread use of blending facilities today, it is much more difficult for the consumer to know the quality of the diesel being delivered. A concern with any blend analysis is whether feedstock differences affect the blend ratio measurement. Using soy biodiesel as a reference blend calibration, only coco methyl esters require a separate calibration in order to accurately determine the blend ratio (see Table 12.11). It should be noticed that measurement at 5.7 mm does not distinguish a biodiesel/diesel blend from an adulterated vegetable oil/diesel blend. A multi-wavelength analyser (FTIR) or a portable variable filter array (VFA) spectrometer can scan different wavelengths and detect the presence of vegetable oil in a blend. Distribution centres face another serious problem in determining the resulting cetane number of diesel/biodiesel blends. Most customers use cetane index (a mathematerial model using distillation and density as a correlation to cetane number) rather than cetane number to evaluate their diesel fuel’s combustion quality. However, biodiesel blends dramatically change the distillation qualities of diesel, making the current cetane index equation unusable (see Section 12.3.1). The blender is forced to use cetane engines or a correlative cetane method. Mid-IR or NIRS can also be used Table 12.11 Comparison of different feedstocks using a fixed filter IR analyser at 1745 cm–1 calibrated for soy biodiesel (after ref. [26]) Feedstock

Biodiesel (%)

Soybean Yellow grease Palm Animal fat Rapeseed Coconut

20.4 20.1 20.5 20.5 20.4 26.3

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Biodiesel science and technology

(see Section 12.5.2). The quality consciousness of distributors is all important (Table 12.12). Fuel delivery from a distributor is a most likely cause of drastic changes in fuel quality [34]. The aforementioned fuel quality surveys indicate that there is still generally little recognition that quality problems can arise in the distribution chain. Verification of fuel quality before use may rely on time-consuming and costly laboratory testing or on periodic laboratory testing, which does not spot the occasional bad batch of fuel. Several options exist for reliable and quick on-site quality testing, namely the aforementioned field test kits, portable laboratory instruments and fully-fledged laboratory instruments. Fleet managers often prefer a combination of field-testing (using a test kit or portable laboratory instrument) and periodic laboratory testing. The field tests will increase the likelihood of catching bad fuel before it does any harm, and laboratory testing will catch more subtle problems before they trigger the field tests [34]. On-site biodiesel test kits are available to complement laboratory test results and reduce the frequency of laboratory analysis [35]. Typical on-site test kits allow users to rapidly determine water contents (of stock oils and biodiesel), density, and viscosity (of biodiesel), total acid number (TAN) (of biodiesel), acid content (of stock oils, for catalyst optimisation) and visual quality. Benefits for manufacturers and end-users are listed in Table 12.13. Table 12.12 Quality consciousness of distributors   ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Ascertain use of consistent feedstock by supplier Verify fuel quality from supplier Use additives to compensate for seasonal conditions Use correct blending method of biodiesel fuel with petroleum diesel Use dedicated storage tanks and trucks Test periodically biodiesel tanks for fuel degradation Provide assistance in case of suspect bad fuel Cooperate with a fleet’s quality assurance programme

Table 12.13 Benefits of on-site biodiesel field test kits for manufacturers (M) and end-users (E) ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Ensure quality of base feedstocks (M) Optimise the ratio of chemicals used (M) Gain real-time batch-to-batch data (M) Refine and troubleshoot production (M) Ensure end-product quality and consistency (M) Ensure quality of delivered fuel (E) Monitor batch-to-batch consistency (E) Check stored biodiesel for deterioration over time (E) Gain confidence in producer (E)

Analytical methods and standards for quality assurance

539

Hand-held devices for biodiesel testing are available such as those based on mid-IR or on electrochemical impedance spectroscopy (EIS), allowing the determination of blend ratio, total glycerol, methanol and acid number. The hand-held Paradigm Sensors, LLC (Milwaukee, MI) i-Spec™-Q100 biodiesel analyser, based on EIS and honoured with the 2008 R&D Award for Biodiesel Analyzer, can be used for determination of blend concentration, 2–99% (reference: ASTM D 7371, mid IR); total glycerol in B100, 0.03– 0.7 wt% (reference: ASTM D 6584, GC); methanol in B100, 0.02–0.9% (reference: EN 14110, GC); and acid number in B100, 0.2–3.5 mg KOH/g (reference: ASTM D 664) [36]. With such devices biodiesel producers can identify and manage variables in B100 batches affordably between regular laboratory checks, blenders can determine incoming quality, fleet managers and owners can test on-site to determine the quality and blend percentage of their biodiesel, regulators have a convenient and cost-effective means to screen biodiesel and increase throughput, and revenue agents can screen the percentage blend on-site. On-vehicle biodiesel/diesel blend sensors enable the engine management system to detect the fuel, adjust the engine settings in correspondence with different blend levels and optimise emission control [37–39].

12.4.4 Regulatory analysis and fuel testing Testing laboratories and regulatory agents may be exposed to a wide range of FAME content, from B2 up to B100. Infrared provides a rapid, precise and accurate tool for this analysis (EN 14078, ASTM D 7371). Bradley [40] has described ATR-FTIR with partial least squares (PLS) analysis procedures, following the guidelines developed by the ASTM D02 Committee on biodiesel analysis. The key concern for testing laboratories is that the variability in petroleum diesels from region to region must be modelled for the analysis to be useful. For quantification of the amount of ester in a blended diesel fuel for regulatory or tax benefit purposes, FTIR technology can be used (see Section 12.5.2). Alternatively, both liquid scintillation counting (LSC) and the (very expensive) accelerator mass spectrometry (AMS) technology can be used for bio-content analysis of such blends (14C fraction is directly proportional to the biodiesel fraction) [41]. Similarly, Reddy et al. [25] used natural abundance radiocarbon analysis. Products such as petrodiesel, fully composed of fossil carbohydrates, no longer contain any radiocarbon, which has decayed completely within the past millions of years. ASTM Standard D 6866-05 describes Standard Test Methods for Determining the Biobased Content of Natural Range Materials Using Radiocarbon and Isotope Ratio Mass Spectrometry Analysis. Certified biodiesel laboratory testing services are available worldwide

540

Biodiesel science and technology

(e.g. Intertek) or locally (e.g. Fuel Only, Vancouver, WA; Gorge Analytical LLC, Hood River, OR; or Manitoba Hydro, Selkirk, MB) for biodiesel fuel produced from various sources, as well as for alternative or experimental biofuels. NBAC certifies commercial laboratories that analyse biodiesel. Analytik-Service Gesellschaft (ASG, Augsburg) is a pan-European accredited testing institute for the analysis of biofuels, established in 1992 on behalf of the fuel trade, government committees, the automobile industry and other associations. According to regulators, detection limits must be ten times below the regulated concentration levels to provide sufficient margin to ensure a sensitive measurement.

12.5

Biodiesel analytical methodology

A wide variety of analytical methods is needed in order to guarantee a high level of biodiesel manufacturing and final product quality (Table 12.14). The choice of equipment needed for a specific analysis depends on regulatory requirements, or time, cost and labour requirements. The standard analytical methods are slow (requiring hours or days) and often require multiple physical analyses per sample. Most traditional reference instrumentation must be kept in a stable laboratory environment, away from the process line. Some analyses for process control or quality verification are quick, while others require a more complete test according to the ASTM and EN approved methods. The parameters for quality of biodiesel require different types of instruments. No analyser will do it all. For example, test methods under ASTM D 675108 for quantifying contaminants present in biodiesel (with free and total glycerol, methanol and water being of most importance) all require different equipment, reagents and supplies, which increase cost and complexity of a QA system. Methanol presence is determined by a flash-point tester (ASTM D 93) or a GC method (EN 14110). The flash-point method does not allow for exact quantification but determines only that the concentration is above or below a certain threshold. The amount of water present is determined by the percentage volume of water centrifuged out of a sample (ASTM D 2709). Free fatty acid levels are determined by a potentiometric titration that is not part of the ASTM test methods. There are common analytical pitfalls that increased analytical capability helps resolve. The following sections discuss methods for biodiesel analysis in more detail. Biodiesel analytics have been reviewed recently [42, 43].

12.5.1 Chromatography Early work on chromatographic analysis of transesterification products used thin-layer chromatography-flame ionisation detection (TLC-FID) [44, 45].

Table 12.14 Biodiesel analysis chart     B5 5% Biodiesel B20 20% Biodiesel blendd blendc

B100 100% Biodiesel (FAME)

541

Acid value D 664, EN 14104   Potentiometric titration   Alkali metals (Na, K) EN 14108/9   FAAS   Alkaline earth metals (Ca, Mg) EN 14538   ICP-OES   Aromaticity D 1319 GC-FID; Mid-IR GC-FID Biodiesel in blended fuels EN 14331; EN 14078, D 7371 GC, LC; Mid-IR GC, LC Bromine index D 457   Titration   Carbon residue (10%) D 4530, EN-ISO 10370   Conradson method   Cetane index D 976, D 4737, EN-ISO 5165 Engine test, Mid-IR Engine test Cetane number D 613, EN-ISO 5165 Engine test, Mid-IR Engine test Cloud point D 2500, D 3117, EN-ISO 23015 Optical detection Cold filter plugging point D 6371, EN 116 Flow test through   filtering device Copper strip corrosion D 130, EN-ISO 2160 Heating in fuel bath at   323 K for 3 h Density D 4052, D 5002, EN-ISO   Hydrometer,   3675/12185   oscillating U-tube na Distillation temperature D 86 Atmospheric pressure distillation   Distillation temperature D 1160 (B100) na   Vacuum distillation (AET) Ester content EN 14103a CGC-FID, Mid-IR CGC-FID Free fatty acids AOCS Ca 5a-40   Titration   Flash point D 93, EN-ISO 3679 Pensky-Martens closed cup   tester, Setaflash method Free total glycerol D 6584, EN 14105/6 HTGC, COC HTGC-FID Heat of combustion D 240   Oxygen bomb calorimeter   Iodine number EN 14103, EN 14111 Potentiometric titrationb,   CGC-FID

Analytical methods and standards for quality assurance

Application Test method(s)

B5 5% Biodiesel B20 20% Biodiesel blendd blendc

B100 100% Biodiesel (FAME)

Karl Fischer moisture D 6304 Coulometric titration Kinematic viscosity @ 313 K D 445, EN-ISO 3104 Capillary viscosimeter Linolenic acid methyl ester EN 14103 CGC-FID Lubricity D 5001, D 6079 BOCLE wear test, HFRR Methanol EN 14110 CGC-FID Mono-, di-, tri-glycerides D 6584 COC HTGC-FID Oxidation stability D 2274, EN 14112 Rancimat induction period PAHs   GC, Mid-IR GC Phosphorus D 4951, EN 14107 ICP-OES Polyunsaturated methyl esters – Under development Pour point D 97   IR - detection   Simulated distillation D 2887 GC Specific gravity D 792, 1SO 1183   Weighing   Storage stability –   to be proposed   Sulphated ash content D 874, ISO 3987   Combustion; addition of   sulphuric acid Sulphur D 5453, EN-ISO 20846, UV fluorescence; WDXRF EN-ISO 20884 Thermal stability – to be proposed Total contamination EN 12662   Filtration over 0.8 mm filter   Water D 1796, D 2709, EN-ISO 12937 Coulometric Karl   Fischer titration a

Under ASTM development. Wijs reagent. c Applies also for B20. d Applies also for B5–B100. na Not applicable. b

Biodiesel science and technology

Application Test method(s)

542

Table 12.14 Continued  

Analytical methods and standards for quality assurance

543

However, detection of steryl glycosides still takes advantage of thin-layer chromatography [46]. To date, standard GC methods are most widely used for analysing biodiesel due to their high accuracy and resolution in quantifying minor components (such as key organic contaminants). Arguably the most critical test for biodiesel is the measure of glycerol content. Free glycerol has been associated with injector deposits, clogged fuel systems and general failure in diesel engines, with the amount of free and bonded glycerol reflecting the fuel quality. Free glycerol analysis is therefore a key point for quality control. The first tailor-made method for analysing glycerol in biodiesel, published in 1991, was based on multiplestep enzymatic conversion of free glycerol extracted from fuel samples [47]. Recently, an enzymatic method for determining free and total glycerol has become available commercially [48]. Various other procedures have been described for determination of free glycerol in biodiesel (Table 12.15). Some of these methodologies also allow the simultaneous determination of mono-, di- and triglycerides and methanol [49–54]. Gas chromatography is often used as the analytical method of choice for free and combined glycerol analysis since it is sensitive and reliable. One of the biggest challenges in biodiesel fuel analysis is the accurate determination of residual triglycerides, which are present at low levels and elute at high chromatographic temperatures. GC analysis typically involves a derivatisation step that is both time- and reagent-consuming [55]. GC-FID is more widely used for biodiesel analysis than GC-MS [56, 57]. ASTM D 6584 and EN 14105 are the standard GC-FID test methods for the quantitative analysis of free glycerol and MG, DG and TG (bound glycerol) in biodiesel. There are differences in the standard solution concentrations and column temperature conditions in ASTM D 6584 and EN 14105. However, in both cases derivatisation is conducted using N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA) and analysis is carried out with cool on-column (COC) injection into the capillary column and field ionisation detection (FID). A column that can support a maximum temperature of 673 K is used. One of the standard methods for determination of free glycerol listed in the European norm (EN 14106) prescribes a first extraction step in which glycerol is separated from the bulk of methyl esters, followed by CGC-FID analysis. The procedure, which does not require derivatisation prior to chromatographic separation, is applicable to fuel samples with a free glycerol content of 0.005 to 0.070 wt%. A procedure allowing contemporary determination of free and bonded glycerol (mono-, di- and triacylglycerols), described by Plank and Lorbeer [49], was later developed and standardised under CEN activity into norm EN 14105. The test method is very accurate, easy to handle and satisfactory. Nevertheless, according to the CEN TC 307/WG1 Committee the availability of an alternative free glycerol evaluation method is wanted because traces of some volatile products (solvents, hydrocarbons) may interfere

544

Biodiesel science and technology

Table 12.15 Determination of free glycerol in biodiesel   Analytical methodology

Reference(s)

∑ Spectrophotometry; aqueous extraction, enzymatic conversion ∑ GC; without extraction and derivatisationa ∑ CGC-FID, CGC-MS; aqueous extraction or derivatisationb ∑ CGC-FID; derivatisation by trimethylchlorosilanc ∑ GC-FID; ethanol/hexane extraction ∑ CGC; derivatisation with TMSd ∑ HPLC-PAD; after aqueous extraction ∑ Spectrophometry; enzymatic glycerol conversion to coloured compounde, l = 540 nm ∑ Colorimetry, PDA UV-VIS; periodate oxidation, l = 410 nm ∑ HPLC-RID; aqueous extraction ∑ COC CGC-FID; derivatisation with MSTFAf ∑ RPLC-PDA/ESI-MS ∑ Simple on-column CGC ∑ COC GC-FID; derivatisation with silylating agent ∑ HTGC-FID; derivatisation

[47] [59] [56] [49], EN 14105 EN 14106 [57] [60] [51] [58, 61] [62] ASTM D 6584, [50, 53, 63–66] [67] [54] [68] [52]

a

Insufficient detection limit.   Silylation with N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA). c Generally known as Christina Plank’s method. d Simultaneous determination of free glycerol and methanol. e Quinoneimine dye. f N-Methyl-N-trimethylsilyltrifluoro-acetamide (MSTFA). b

with the procedure according to EN 14105. Table 12.15 lists some recent developments. The colorimetric method for determination of free glycerol in biodiesel by means of PDA UV-VIS spectrophotometry, described by Bondioli and Della Bella [58], is based on the sodium periodate oxidation of free glycerol to formaldehyde and its subsequent reaction with acetyl acetone to form the yellow complex 3,5-diacetyl-1,4-dihydrolutidine (lmax = 410 nm). Currently, high-temperature gas chromatography (HTGC) is the accepted method for determining total glycerol in biodiesel. PTV HTGC-FID analysis at 653 K of glycerol in biodiesel complies with ASTM D 6584 [52]. Although GC is the standard analysis technique for determination of glycerol, it has several inherent challenges. In the first place, HTGC may not be applicable with biodiesel produced from certain feedstocks (greases) since it speciates both fatty esters and partial glycerides. Secondly, the tests run at very high temperature whereas standard fused silica columns do not withstand temperatures above 653 K. In fact, above this temperature the polyimide coating of most fused silica columns starts to degrade. The alternative metal columns present other challenges as they often develop leaks due to expansions and contractions during oven heating cycles; this compromises the accuracy of the analysis. Unique fused-silica columns (Zebron™ ZB-1HT and ZB-5HT

Analytical methods and standards for quality assurance

545

Inferno™), designed specifically by Phenomenex, Inc. for high-temperature analysis, are thermally stable up to 703 K and allow rugged and durable HTGC at 653 K [63, 69, 70]. In other work, COC HTGC-FID equipped with a TRACE GC Ultra column was used for the determination of free and total glycerol in B100 at 638 K [66]; also the application of a TRACE TR-HT5 high-temperature carborane-modified siloxane phase column at 638 K was reported for the same purpose [64]. The high temperature stability problem in the analysis of total glycerides has reportedly also been solved by using new full metal capillary columns (Restek MXT®-Biodiesel TG) with low bleed at 703 K [65].The latest GC column technology includes Varian’s Select™ Biodiesel Glycerides column, a high-resolution metal capillary column specifically designed to withstand the rigours of triglycerides analysis at high temperature over extended periods of use. Measurement of glycerides in biodiesel is a lengthy process due to the need for standards and derivatisation. In view of the diverse molecular size and elution range, several reference materials (e.g. glycerol, monoolein, diolein) and internal standards (e.g. tricaprin, 1,2,4-butanetriol) are required. Chemical reference standards of FAMEs, free glycerol and mono-, di- and trigycerides in biodiesel (in particular to meet ASTM method D 6584 and EN 14103-14105) and biodiesel/diesel blends are commercially available (Interscience, Chiron AS, AccuStandard and others). Chromatographic methods for the determination of bound glycerol in biodiesel were compared [71]. Non-glyceridic materials such as sterols and sterol esters in biodiesel were also analysed by GC [72]. For the three most commonly applied GC-based methods, namely EN 14103 for characterisation of FAME and determination of linolenic acid methyl ester, EN 14105/ASTM D 6584 for free and total glycerol content, and EN 14110 for methanol, comprehensive single integrated GC analysis packages are now available. Biodiesel GC turnkey systems have been developed which combine several chromatographic ASTM and EN methods in an all-in-one GC-FID solution (hot COC-injection technique) with calibration according to specified methods (see Table 12.16) [73]. EN 14106 quickly determines Table 12.16 All-in-one biodiesel chromatographic analysis methods (after ref. [73])   Method Analysis Inlet

Analysis time (min)

ASTM D 6584 Free and total glycerol EN 14103 Ester and linolenic acid methyl   ester content EN 14105 Free and total glycerol, MG, DG   and TG content EN 14106 Free glycerol EN 14110 Methanol content

On-column (TPI) Split/Splitless

35 25

On-column (TPI)

35

Split/Splitless Split/Splitless

10 10

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Biodiesel science and technology

the free glycerol content in FAME upon a single level calibration. The free glycerol content determined according to EN 14105 and ASTM D 6584 requires more labour intensive sample preparation, multilevel calibration and a longer analysis time. PerkinElmer® has recently (March 2008) launched the EcoAnalytix™ Glycerin and Methanol Analyzer providing a complete solution to test biodiesel – for both free and total glycerol (EN 14105, ASTM D 6584) as well as residual methanol (EN 14110) – with a single integrated HS-GC system. Similarly, Thermo Fisher Scientific, Inc. has come forward with the Biodiesel GC Productivity Solutions system in a two-GC/one autosampler configuration [74]. EN 14331 is the only industry standard GC method for measuring the FAME content in biodiesel blends [75]. Present trends are towards fast GC methods using capillary flow technology and 2D GC [76]. ASTM D 6584 is designed to analyse biodiesel samples for impurities that foul, clog and cause deposits in engines. Making the correct identification of closely related formulas in complex mixtures is among the greater challenges facing the practitioner. Two-dimensional GCFID data alone are often insufficient to indicate the specific source of an interference. Test method ASTM D 6584 is a work in progress. Balogh [77] recently discussed advanced chromatography-mass spectrometry in biodiesel characterisation. Few reports exist on coupled-column techniques in biodiesel analysis [78–80]. This is partly due to the fact that regulations recommend GC analysis for free and total glycerol, FAME and residual methanol, but is also partly on account of higher equipment cost and the need for considerable technical skills. On the other hand, meeting the requirements of biodiesel standards only requires quantitation of classes of compounds rather than individual compounds, i.e. acylglycerol instead of MG, DG or TG; FAME instead of oleic acid methyl ester. Consequently, the need for enhanced analytical discriminating power is often limited. Nevertheless, the GC¥GC technique provides an effective solution for characterising biodiesel blends by increasing the chromatographic power. It can determine the biodiesel percentage content in the blend and details the FAME composition, delivering information about the type of oil used, the origin of the biodiesel and the cetane number, and pour point evaluation. Analysis of FAME content in blended biodiesel samples, using a LE-RSO standard, has been described using a heartcutting 2D GC method with a primary non-polar and a secondary polar capillary column [81]. The primary column separates most of the petroleum hydrocarbons from the FAMEs, which are then completely resolved in the secondary column. The distribution of individual FAMEs is obtained, which allows identification of the feedstock source. Since the total amount of biodiesel in the blends is distributed among several FAME peaks, it is not possible to use any single peak for quantification. Instead, the area responses of all FAME peaks need to be summed to represent the total amount of biodiesel in the blend for

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calibration. Good linearity for biodiesel blends from 1 vol% to 25 vol% FAME concentrations can be achieved. Multidimensional chromatographic techniques such as AgLC ¥ GC and GC ¥ GC are important for a detailed four-dimensional characterisation (variations in chain length, number of double bonds, double bond positions and orientation) of triacylglycerides from edible oils and fats and their corresponding FAMEs [82]. In the past, LC-GC coupling was mainly used for the analysis of minor components in vegetable oil methyl esters [79, 80]. As indicated in Table 12.6, a suitable standard PUFA (D ≥ 4) methyl ester procedure within EN 14214 is still pending. The main problem for testing the analysis of long-chain (LC) PUFAs is their instability. AOCS Official Method 991.39 [83] and AOCS Official Method Ce 1b-89 [84] provide guidelines for quantification of n-3 LC-PUFAs in marine oils using C23 : 0 (methyl tricosanoate) as an internal standard (IS). However, choosing C23 : 0 IS can lead to systematic overestimation of n-3 LC-PUFAs (by as much as 7% or more). Selecting the appropriate IS (C19:0 for unsaturated C20 FAMEs or C21 : 0 for unsaturated C22 FAMEs) improves the analytical results [85]. Recently, a GC-FID method for determination of polyunsaturated fatty acid methyl esters using a polar column and C23 : 0 methyl ester as an internal standard has been developed [86]. Predominant PUFAs found in marine oils and fats (C20 : 4, C20 : 5, C22 : 5 and C22 : 6) have been used for quantification in concentration ranges of 0.1–3.0 wt%. The method has been proposed within a European project called BIOSCOPES and is based on AOCS Official Method Ce 1b-89 and EN 14103 with some modifications. Fewer reports appeared on the use of HPLC in biodiesel analysis [60, 87–94] in comparison to GC analysis. However, European producers typically also use HPLC methodology for analysis of the final product for by-products. HPLC offers considerable advantages for biodiesel analysis (see Table 12.17). A notable advantage of HPLC over GC is that derivatisations are generally not necessary, which reduces analysis time to some 20 min per run [43, 95], occasionally even lower [92]. HPLC-PAD for free glycerol determination is characterised by high sensitivity; the simultaneous detection of residual alcohol is also possible with this technique [60]. HPLC-ELSD has been used to quantify product esters, FFA and acylglycerols [89]. RPLC in combination with various detection methods (UV, ELSD, APCI-MS) was used for rapid quantification of rapeseed oil methyl esters [90]. The results differed for various detection methods. APCI-MS and ELSD showed decreased sensitivity with increasing number of double bonds in the fatty acid methyl esters, whereas UV does not quantify the saturates. Foglia et al. [87] described the use of HPLC-ELSD for determination of total glycerol and soy diesel blend levels (B1 to B99). No statistical difference was observed between the GC and HPLC methods in determining bound glycerol in soy, rapeseed, grease or animal fat-based biodiesel fuels [87].

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Table 12.17 Comparison between biodiesel GC and HPLC methods (after ref. [87])   GC method Advantages: Disadvantages: ∑ Analysis of free and bound glycerol ∑ Requires silylation prior to ∑ Internal standards used for quantitation analysis ∑ Standards for each feedstock ∑ Interpretation of chromatograms ∑ Procedurally difficult HPLC method Advantages: Disadvantages: ∑ No sample derivatisation required ∑ External standard curves for ∑ Simple class separation of lipid classes quantitation ∑ Analyses biodiesel from most feedstocks ∑ Procedurally easy ∑ Analysis time < 30 min ∑ Detects and measures fatty acid oxidation products ∑ Quantitative analysis of bound glycerol in B100 ∑ Analysis of biodiesel/petrodiesel blend levels (B1 to B99) ∑ Quantitation of total glycerol (at 0.02 wt% specified ASTM) ∑ Detects glycosides  

GC and HPLC analyses of biodiesel consume valuable personnel and instrumentation time. Lab workers are often exposed to carcinogenic, halogenated solvents to perform needed analyses. UPLC-PDA/ELSD provides a methodology with lower toxicity solvents (acetonitrile and 2-propanol) for high resolution and sensitive separation of biodiesel feedstock, reaction intermediates, glycerol, FFA and fuel products (FAME) in a single 12-min experiment [92]. This facilitates monitoring of production processes to improve the yield. In a well-developed biodiesel production process, obtaining the relative amounts of FAME, FFA and residual total TAG is sufficient to make critical process decisions. UPLC-PDA/ELSD separation is faster than conventional techniques, derivatisation is unnecessary and toxic halogenated solvents are not used. An additional value from using the UPLC system is reduced solvent consumption and disposal, resulting in lower cost and increased safety benefits. Gas chromatography is less convenient for the analysis of non-volatile acylglycerols, where LC-MS can be adopted instead. Huang et al. [93] and Chen and Cavagnino [94] have developed a preliminary high-speed RPLC-PDA/ESI-MS method (with cone wash) for the complete analysis of blended biodiesels, in particular B5. The method, which reveals information about low-MW compounds (including FAMEs) and higher-MW compounds in 20 min (as compared to 60 min for conventional LC-MS), is focused on

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standard EN 14331. This analysis is usually carried out by GC-MS due to the higher resolution compared to LC separation. However, GC analysis of high-boiling triglycerides requires an accurate choice of injector, column and overall operating conditions, in order to avoid any sample discrimination and/ or degradation. LC-MS methods can be adapted for non-volatile component analysis but have not been generalised in the regulatory analysis. The patented cone wash integrated into the electrospray source of the mass spectrometer allows for uninterrupted analysis of complicated sample matrices. Recently, ASTM D 5186 has been modified for biodiesel analysis using SFC-FID [96]. As a fast SFC-MS/UV-ELSD method with overall analysis time of only 3.5 min can be used for group separation of FFAs, FAMEs and glycerol, the main target compounds for biodiesel analysis, SFC holds great potential to become the chromatographic technique of choice for biodiesel analysis [97]. Applications of size-exclusion chromatography (SEC) to biodiesel analysis are sporadic. SEC-RI has been used for analysis of mono-, di-, and triacylglycerols, methyl esters and glycerol in palm biodiesel [98, 99]. SEC has also been evaluated as an alternative method for the EN 14103 standard in the determination of fatty acid methyl ester purity [100]. With the maximum free glycerol content being limited to 200 ppm in ASTM D 6751 and EN 14214, gas chromatographic determination is both tedious and rather expensive, involving time- and reagent-consuming derivatisations. In addition, GC methods encounter co-elution problems with biodiesel samples produced from or containing lauric oils, such as coconut and palm kernel oil. Ion chromatography (IC) has been proposed as a simple, cost-efficient and highly accurate alternative [101]. Prior to chromatographic separation, free and bound glycerol are isolated by a straightforward extraction and saponification-extraction technique, respectively. IC-PAD achieves a detection limit of 0.7 ppm for free and total glycerol, which exceeds the ASTM and EN performance specifications. In contrast to GC, the ion-chromatographic method is applicable to all types of vegetable oil methyl esters. Ion chromatography also allows determination in biodiesel of alkaline metals and alkaline earth metals by non-suppressed and suppressed conductivity detection (see Section 12.5.5), and of antioxidants by UV/VIS detection [102]. Volatile fatty acids can be accurately determined applying ion-exclusion chromatography with suppressed conductivity detection.

12.5.2 Spectroscopy Spectroscopic analysis is often a quicker method than chromatography for production monitoring, verification of product quality on the buyer end, and determination of biodiesel blend levels. The main spectroscopic methods evaluated for the analysis of biodiesel are mid-IR and near-infrared (NIR)

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spectroscopy; 1H and 13C NMR spectroscopy and Raman spectroscopy have been used more sporadically. Apart from measuring oil and moisture contents in oilseeds and in total fat analysis there appear to be few opportunities for the use of process NMR in the biodiesel industry. Many crucial measurements in biodiesel analysis can be performed by mid-IR analysis. A rapid, practical and accurate FTIR method was reported for the determination of FFA in edible oils [103]. FTIR (with or without chemometric modelling) for rapid feedstock and process check can determine viscosity, acid number, flash point, cetane number, iodine value, water (ppm), methanol, free glycerol, bound glycerol (MG, DG and TG), and biodiesel/diesel blend ratio. FTIR offers rapid multi-property analysis. These measurements include FFAs and water in the feedstock (5 min by unskilled technician). Measuring FFA in oils by rapid FTIR analysis involves adding a weak base to form a salt whose carbonyl absorption band is shifted away from that of the biodiesel ester [103]. The method correlates well with the AOAC titrimetric method. Mid-infrared routinely allows simultaneous determination of total glycerol, acid number, cloud point, free glycerol, moisture and methanol (QTA System, Cognis Corp.) [31]. Anaspec’s (Moordrecht, The Netherlands) polychromatic diode array analyser (1100–2100 nm range) can be placed inline or near the production line and allows measurement of various properties (free MG, DG, TG, methanol) in different process steps and final control of biodiesel production. FTIR can also be used during the production process by monitoring the conversion in terms of unreacted fatty acids and glycerol, and to determine FAME yield [104]. FTIR methodology was used to monitor ultrasonicallyassisted biodiesel production [104]. A portable ATR-FTIR analyser enables determination within 5 min of when the reaction is complete, namely when bound glycerol (MG, DG and TG) is below 0.24 wt%; GC analysis would require 45 min. The speed of the procedure allows reactor throughput to be increased by 15–20%. Obviously, GC testing according to ASTM D 6584 and EN 14105 specifications is still necessary for finished lots of biodiesel. Recently, an analytical procedure was developed to monitor ethanolysis of degummed SBO using FTIR and methods of multivariate analysis such as PCA and PLS [105]. Infrared spectroscopy is also often used for rapid on-line assessment of the quality of biofuel products, such as the determination of contamination of the finished fuel on the distribution end [106]. However, the technique is less sensitive to minor components than GC. The two techniques are frequently used in conjunction with each other for a more complete analysis. Methods developed thus far have often focused on FAME content [40]. Water can be extracted from biodiesel with acetonitrile and measured in the 6 mm region. Mid-IR spectroscopy is suitable for the direct determination of biodiesel/

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diesel blend levels [107]. The blend ratio can readily be measured on-site at the characteristic absorption of the carbonyl group (~1745 cm –1) of the biodiesel ester in 1 min by non-technical personnel using portable mid-IR instrumentation (e.g. Wilks Enterprise, Inc. ATR-based, variable filter array Infra Spec VFA-IR spectrometer) [106]. Blend detection by IR at this frequency is at the basis of EN 14078 [Determination of Fatty Acid Methyl Esters (FAME) in Middle Distillates – IR Spectroscopy Method]. Also the recently-passed ASTM Method D 7371–07 specifies mid-IR for the determination of FAME content in B1 to B20 blends using ATR-FTIR-PLS. In principle, a portable fixed-filter IR analyser (e.g. Wilks’ InfraCal Biodiesel Blend Analyzer [106]) can be used to measure the blend ratio. However, the method of FAME concentration measurement in blends from the height of the carbonyl band using Beer’s law [108] is actually limited to approximately 18% FAME. Using a short range of the IR spectrum (peak area between 1300 and 1130 cm–1) allows determination of a wider range of FAME concentrations (up to B50). Recently, an even more robust IR transmission method for biodiesel concentration measurement was reported using the full IR spectrum (except for the 1745 cm–1 carbonyl peak and C-H peaks at 2900, 1460 and 1370 cm–1 regions) and principal component regression (PCR) chemometrics for even higher FAME concentrations [109]. Also genetic algorithms have been applied to FTIR spectrograms for biodiesel/diesel blend ratio measurement [110]. With the Grabner Instruments (Vienna) IROX-Diesel it is possible to determine the biodiesel concentration from 0 to 40 vol% using FTIR spectroscopy [111]. The measurement method is under evaluation within the ASTM committee (WK 10753). Portable fuel analysers enable testing of biodiesel for cetane number in the field and at the pump. CETANE 2000 is a spectroscopic diesel fuel analyser (resulting from co-development of Shell, BP, Ethyl and PetroSpec) for determining cetane number of biodiesel blends through mid-IR analysis (in particular C-O stretch at 1745 and 1160 cm–1) [112, 113]. It combines analysis for density, cetane number and cetane index, total aromatics, polynuclear aromatic and biodiesel content in one portable instrument, which has successfully been applied for process/on-line use. Refiners and regulators can monitor blending operations and measure final specifications efficiently. Distributors are provided with a cost-effective QC tool for monitoring diesel fuels as the fuels move through the distribution system. This virtually eliminates sales of non-branded product throughout the distribution system and the liability of selling product that is off-specification. Zeltex ZX-101XL (Zeltex Inc., Hagerstown, MD) is an alternative portable (near-infrared-based) cetane number analyser to screen biodiesel in the field and at the pump. In accordance with ASTM D 7066-4, portable infrared analysers can be used for on-site determinations of the total oil and grease concentration level in biodiesel plant discharges for compliance with regulatory limits.

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In the recent past, several US biodiesel plants have been fined for illegally discharging vegetable oils and grease and polluting nearby streams. Near-infrared (NIR) transmission spectroscopy is a suitable secondary analytical technique for rapid evaluation of a great many critical chemical and physical properties of substances and can be used for characterisation and identification of complex sample material. Near-infrared (NIRS) spectroscopy allows simultaneous qualitative and accurate quantitative analysis of different parameters, high sample throughput, real-time monitoring, needs no additional solvents and is a non-destructive, cost-effective and user-friendly quality and process tool. On the other hand, the technique needs a relatively high number of samples for robust calibration and development and maintenance of a calibration routine [114]. NIRS instrumentation is rugged, flexible and even portable, and can be used in a process environment. Table 12.18 summarises the main characteristics of NIR spectroscopy. From the characterisation of oil content in oilseeds to fast monitoring of the quality of incoming feedstock oils and fats, on-line quantification of key parameters in biodiesel processing and quality analyses of the product, the use of NIR spectroscopy is rapidly increasing throughout the biodiesel industry provided a sufficient number of samples is available as Table 12.18 Main characteristics of near-infrared spectroscopy   Advantages: ∑ Non-destructive ∑ Small absorption coefficient(s) ∑ Fast measurements (< 1 min) ∑ Multicomponent analysis ∑ Medium sensitivity ∑ Favourable S/N ratio (105 : 1) ∑ Mature technology ∑ Fibre-optic probe ∑ Wavelength and ordinate accuracy and precision ∑ Simple and robust instrumentation (favourable hardware cost) ∑ Low maintenance costs ∑ Qualitative and quantitative applications ∑ Ideal for QC and production environment ∑ Limited operator training needed Disadvantages: ∑ Secondary method (requires calibration against reference method) ∑ Dependence on a large reference set ∑ Slow and costly method development ∑ Need for quantitative calibration model ∑ Troublesome calibration transfer ∑ Strict sample temperature control required ∑ Heavy computation load ∑ Weak sensitivity to minor components; minimum concentration > 0.1% (no trace analysis)

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reference for calibration. The escalating use of NIR is directly attributable to the technique’s convenience and ease of use. Typically, on-line NIR applications can reliably and accurately quantify levels of key parameters in raw fuel material, including free fatty acid and water content, acid and iodine number. The biodiesel production process is a complex catalytic dynamic equilibrium process, with no guaranteed end-point. Use of an at-line monitoring tool such as FT-NIR avoids the need for expensive, slow, and frequently offsite wet-chemical quality screening measurements for production process monitoring, thereby improving the reliability and throughput of both batch and continuous biodiesel transesterification reactors. Very time-consuming analytical procedures of biodiesel quality control are an obstacle to quickly address problems arising during production. Since only one instrument is all that is needed in using FT-NIRS for multiple measurements in a biodiesel production facility, the testing protocol for process samples is simplified, multiple pieces of equipment can be replaced and laboratory supply costs are reduced. Moreover, the ability to quickly analyse samples for multiple components using FT-NIRS much more quickly (30 sec) than traditional primary analytical laboratory methods (up to 1 h) results in considerable time savings. Target analytical properties for biodiesel production monitoring, endpoint determination and final product quality qualification are percentages of methyl ester (yield), FFAs, residual methanol, total glycerol, moisture and by-product mono-, di- and triglyceride (bound glycerol). Trace contaminants of biodiesel can be quantified simultaneously at the low levels called for in biodiesel standards, albeit not with very high accuracy (1–1.5%); correlation coefficients greater than 0.93 were reported [115]. In addition, bulk oil and fuel properties such as viscosity, acid number, flash point and cetane number are specified in the relevant EN and ASTM norms, particularly for final product quality control. All these analyses can be carried out rapidly using off-, at- or on-line FT-NIR methods. NIR analyses of fresh and used cooking oils in terms of the parameters FFA content (acid value), water content, iodine value and trace sulphur content were performed on the basis of reference values obtained by titration (EN 14164), Karl Fischer titration, GC-FID and chemiluminescence (Mitsubishi TS-100), respectively [116]. Biodiesel (B100) end-product parameters determined by near-infrared transmission spectroscopy (NITS) are FFA content [29, 116], moisture content [29, 116, 117], iodine value [116], total glycerol [29, 117, 118], bound glycerol [29, 119], methanol content [29, 117, 119] and methyl esters [119, 120]. FOSS’ XDS Biodiesel AnalyserTM for testing of the intake vegetable oil (FFA, H2O, P), process and quality control of biodiesel, allows rapid simultaneous analysis according to EN 14214 of multiple parameters (Table 12.19) without sample preparation within 2 min

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Biodiesel science and technology

Table 12.19 Concentration ranges and performance of XDS™ analysisa,b (after ref. [121]) Parameter

Nc

Limits

R2

   

Min.

Max.  

Acidity (mg KOH/g) Monoglyceride (wt%) Diglyceride (wt%) Triglyceride (wt%) Total glycerol (wt%) Free glycerol (wt%) Moisture (ppm) IV (g I2/100 g) Linoleic acid (wt%) Methanol (wt%) Ester (wt%)

0.00 0.25 0.00 0.00 0.04 0.00 0 97 4.6 0.00 96

1.14 0.64 0.35 0.78 0.28 0.03 510 131 11.0 0.29 100

399 363 366 355 361 353 389 180 185 59 245

0.98 0.91 0.97 0.95 0.96 0.81 0.95 1.00 0.99 0.99 0.53

a

FOSS XDS Biodiesel Analyser™. Model: PLS. c Number of reference samples. b

by unskilled plant operators, instead of traditional GC analysis by a trained laboratory technician in 1 h [121]. Calibrations are based on methyl esters produced from RSO, PMO, UCO and TLW. NIRS also allows biodiesel blend determination in real time [122]. As shown in Table 12.20, other possibilities for application of NIR analysis of biodiesel are still untapped. NIR procedures are considerably less labour-intensive, faster and easier to perform than GC and sample integrity is preserved. NIRS also finds application as a non-destructive method in pre-screening of seed quality traits in plant breeding projects (see Section 3.3). The literature is rather scarce in relation to the use of spectroscopic methods coupled to multivariate analysis as an analytical tool to evaluate biodiesel characteristics. NIRS and PLS regression [28] and 1H-NMR [123] were used to monitor transesterification and NIRS/PCA and 1H-NMR to determine the blend level of biodiesel in conventional diesel fuel [122]. Fast and accurate simultaneous NIR measurements of water, methanol and total glycerol in B100 in the range of 1375–2750 nm, based on calibration models using PLS and PCR chemometrics, have been reported [117]. NIRS and PLS were also used to determine other multiple components (including trace contaminants) in biodiesel samples [115, 121]. Also ethanolysis of degummed SBO using FTIR and multivariate analysis (PCA, PLS) was described recently [105]. Oliveira et al. [120] have used FT-NIRS and ATR-FTIR combined with PLS and artificial neural network (ANN) analysis methods to determine the methyl ester contents in Brazilian biodiesel blends (soybean, babassu, dendê and soybean fried oils).

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Table 12.20 Opportunities for application of NIR spectroscopy in the biodiesel industry Chemical properties: ∑ Identification of raw material, in-process stock and finished products ∑ Oil content ∑ Free fatty acids (acid number) ∑ IV/HV/AV/SV/PV ∑ Process monitoring ∑ Ester content (biodiesel yield) ∑ Quality control ∑ Composition determinations (0.1–100%) ∑ Methanol content ∑ Bound glycerol ∑ Total glycerol ∑ Water content ∑ Blending control Physical properties: ∑ Flash point ∑ Cetane number ∑ Transparency ∑ Density ∑ Viscosity ∑ Colour

Formation of FAME by transesterification with methanol can be monitored by 1H NMR [124]. This accurate determination is simpler than chromatographic methods. Turnover and reaction kinetics of methanolysis of rapeseed oil have been studied by 13C NMR [125]. Raman spectroscopy has been used to monitor and quantify ethyl esters in soybean oil transesterification [126]. Although the technique is less sensitive than chromatographic methods, the data obtained can be correlated with other techniques, allowing biodiesel yield and quality to be quickly assessed.

12.5.3 Oxidation stability testing It is important to be able to forecast whether diesel fuels containing biodiesel have a storage and oxidation stability sufficient for actual use. Although most biodiesel is used within a few weeks of production, biodiesel blends such as B5 and B20 could be stored for several months. The need to prevent degradation and sediment formation in stored biodiesel blends is essential. Sediment components originate from oxidative cleavage of double bonds in the fatty acid methyl esters (oleate, linoleate), forming polar organic compounds such as aldehydes, carboxylic acids (e.g. azelaic acid, hexanoic acid), ketones, hydrolysis products, etc., which exhibit poor solubility in non-polar ULSD fuel and result in fall-out. Antioxidant addition to B100

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prior to blending with ULSD prevents sediment formation during long-term storage. The significantly lower percentage of oxidatively reactive compounds in palm oil explains why no precipitates form in palm biodiesel. Testing methods for storage stability of fuels are EN 14112 (Fat and Oil Derivatives – Fatty Acid Methyl Esters – FAME; Rancimat™ test), ASTM D 2274 (Standard Test Method for Oxidation Stability of Distillate Fuel Oil) and ASTM D 4625 (Standard Test Method for Middle Distillate Fuel Storage Stability at 110 Degrees Fahrenheit). The oxidation stability of FAME is included in EN 14214 and ASTM D 6751 (based on EN 14112) as a standard parameter used to define the minimum quality requirements of biodiesel. Oxidation stability test methods have so far been very time consuming with rather limited relevance to practical use. ISO 12205/ASTM D 2274 require a 16 h ageing process at 368 K under air-flow and determination of a very small amount of residue. As a result, the method is quite unreliable and does not allow precise differentiation between samples. The approved standard methods for evaluation of oxidation stability differ for B100 and its related mixtures. B100 needs to be assessed by test method EN 14112. Straight diesel fuel and biodiesel/diesel blends should be evaluated in Europe by EN 590 test method DIN EN-ISO 12205 (Determination of the Oxidation Stability of Distillate Fuels). EN 14112 is an accelerated oxidation test at 383 K in which the oxidation stability is detected through conductivity of highly volatile carboxylic acids produced by autoxidation, which is used to indicate induction time. Interpretation requires skill. Metrohm’s 873 Biodiesel Rancimat allows simultaneous and rapid oil stability indexes (OSI) to be performed. Typical applications include: oxidation stability of oils and fats, oxidation stability of motor oils, oxidation stability of biodiesel and determination of the effectiveness of antioxidants. More recently, Petrotest’s PetroOXY method was developed out of the bomb method ISO 7536 – ASTM D 525 – IP 40 [127]. This method is based on a very fast (30 min to 1 h) artificial ageing process in a sealed test chamber at 700 kPa and 413 K, whereby an observed pressure drop is directly related to the oxidation stability of the fuel. The method accounts for all volatile and non-volatile oxidation products thus providing a complete analysis of the liquid sample’s oxidation stability. Correlation with the EN 14112 method is good. The PetroOXY method allows important time savings. The method has recently been standardised as ASTM D 7525–09: Standard Test Method for Oxidation Stability of Spark Ignition Fuel. EI-IP (London) runs a standardisation project for Oxidation Stability of FAME. Pressurised differential scanning colorimetry (PDSC) has recently also been proposed to enable direct comparison of testing results [128]. PDSC allows determination of oxidation induction time (OIT), in compliance with ASTM D 6186, and of the oxidation onset temperature (OOT) [129]. Although OIT and OOT are not strictly correlated, they both measure the

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oxidation stability of a material. PDSC is a useful tool to screen different antioxidants or different antioxidant concentrations for biodiesel fuel. Figure 12.3 shows that a rape biodiesel sample produced with a good Rancimat value of 7 h falls short of the standard already after several days. The European Quality Standard is expected to be tightened in particular as to the oxidation stability requirement. Even stricter demands will then be placed on production, distribution of biodiesel and quality control. There are some doubts on the suitability of ASTM D 4625 for determining the storage stability of FAME and their blends [130]. The oxidation stability of biodiesel can be improved by addition of antioxidants (see Section 6.3.4). Oxidation of biodiesel is a free-radical process, leading to decomposition products via peroxides. Soy biodiesel with 200 ppm antioxidants (BHT, BKF, 2,6-di-t-butylphenol, and TBHQ/citric acid or Eastman BioExtend) was evaluated in an accelerated ageing study [131]. Some analytical tools for oxidation studies (including AN, GC, GPC, OSI, PV, UV, YI) are better than others. The Yellowness Index (YI) and GC-MS were found not to be discerning enough tools for following oxidation under the given experimental conditions. Peroxide value (PV) and UV absorbance measure the intermediate peroxide formation. When peroxide forms, the methylene-interrupted double bonds in the fat molecules rearrange to form 8

7 EN 14214 limit

h Rancimat @ 383 K

6

5 4

3 2

1

0 0

10

20

30 40 Days at 313 K

50

12.3 Ageing of an industrial rape biodiesel sample.

60

70

558

Biodiesel science and technology

a conjugated system, giving rise to absorbance at 232 nm. Good correlation between PV and UV absorbance was observed. Acid number (AN) and GPC are measures of the termination products of the free-radical oxidation. Both show small increases with time, but lack sensitivity. OSI is the recognised tool for assessing extent of oxidation. 200 ppm active antioxidant resulted in very different initial induction times. Transition metal contamination (to 10 ppm) has a significant detrimental effect on OSI. Optimum performance of antioxidants is realised when added to freshly produced biodiesel. Treating already oxidised biodiesel results in little improvement in OSI. The presence of a metal chelator in the antioxidant formulation can mitigate the negative effect of metals on OSI. Although not regulated by standards, antioxidants can also be determined by ion chromatography within the context of quality monitoring and for determining the quantities of additives required [102].

12.5.4 Titration applications Titration is a very useful and practical analytical technique for determining a number of important biodiesel properties, as shown in Table 12.21. A multi-function titration system is a cost-effective solution for product quality control of biodiesel [132]. Moisture within storage systems has a negative effect on biodiesel quality and is a critical parameter in predicting the stability of the bulk product for storage and transportation purposes. Accelerated degradation of biodiesel blends, microbial contamination and filter blockages are all directly caused by moisture within underground fuel storage systems. Water content is determined in biodiesel according to EN-ISO 12937 (Karl Fischer titration, KFT). Coulometric KFT allows ease-of-use and high accuracy and precision at low moisture levels (< 100 ppm). It has been pointed out that many biodiesel fuels contain additives or impurities that can undergo side reactions during coulometric KF titration [133]. There is an ongoing workshop at ASTM

Table 12.21 Titration applications in biodiesel analytics   Titration technique Coulometry (KF) Potentiometryb Thermometry Colorimetry Redox a

a

Biodiesel property Water content Total acid number (FFA content), iodine number, neutralisation number (soap content) Free fatty acids Soap content, acid numberc Iodine value

Standard test methods: ASTM D 6304, E 1064, ISO 760, JIS K2275. Standard test methods: ASTM D 664, ISO 6619, JIS K2501. c Standard test method: ASTM D 974. b

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looking at utilising the Karl Fischer moisture test method in the biodiesel specification. Potentiometric titrations may be used to determine acidic or basic properties, including the total acid number (TAN) or neutralisation number (NN), and FFA content. Free fatty acid values in edible fats and oils can be determined by thermometric titration (measuring reaction enthalpy) using a strong endothermic response caused by base-catalysed depolymerisation of paraformaldehyde as an end-point indicator [134, 135]. On-line free fatty acid titro analysers bridge the gap between process and laboratory by providing analysis within a process environment with laboratory accuracy at approximately 10 min intervals. Colorimetric titration can be used to determine the soap content of biodiesel, where the sample is titrated with a standard HCl solution (in acetone) to the Bromophenol Blue end-point. Non-aqueous colorimetric titration according to ASTM D 974 uses KOH/i-PrOH as a titrant and p-naphtholbenzein as an indicator for acid number analysis. Redox titrations can be used to indicate the relative amounts of unsaturated hydrocarbons in a given sample, as expressed by the iodine value (IV), which in turn is an indicator of the fuel’s stability.

12.5.5 Trace element analysis The capability to quantify trace contaminants in biodiesel is crucial for optimising the biodiesel production process and ensuring final product quality. Quantifying impurities in the biodiesel production process, either in-line or on-line, can help optimise yield and purity of the fuel. Determination of Na and K in certain biodiesel manufacturing processes is especially important since alkali compounds are used as catalysts in the transesterification of vegetable oils to biodiesel. Calcium and magnesium contaminations derive from the use of hard water to extract impurities or from the use of certain adsorbents for their removal. Ash is a measure of the amount of metals contained in a fuel. Ash forming materials may be present in three forms: abrasive solids, soluble metallic soaps and residual biodiesel catalyst. Abrasive solids and biodiesel catalyst materials result in wear of fuel system and internal engine components exposed to fuel after injection. Metallic soaps can contribute to deposits in the fuel system. Therefore, standards defining quality specifications and test methods have been developed. Accurate elemental analysis of biodiesel requires sensitive and selective analytical methodology, such as AAS, XRF, ICP-OES, SCD, UVF and IC. In Europe, methods EN 14108 and EN 14109 are specified and use AAS for measuring Na, K in biodiesel. ASTM D 6751 specifies the use of ICPOES for the determination of alkali and alkaline earth metals in biodiesel.

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With ICP, elemental content can be rapidly monitored throughout the entire processing cycle, starting with the raw oil and continuing through to the finished product. ICP-OES is ideally suited for the analysis of biodiesel fuels and can determine up to 70 elements in a sample simultaneously in under 30 sec. ICP detection limits easily satisfy the requirements of the EN 14214/ASTM D 6751 standards for biodiesel [136] (see also Table 12.22). Comparable results are reported for axial- and radial-view configurations; however, the detection limits of P, S and Pb are poorer for the axial view [137]. PerkinElmer® has recently launched the EcoAnalytixTM Trace Metals Biodiesel Analyzer, based on ICP-OES. Biodiesel standards for single- and multi-element analysis of metals (Na, K, Mg, Ca) and phosphorus and sulphur by ICP-OES, formulated from soybean oil, are available from VHG Labs (USA). Although raw materials may not contain large quantities of sulphur, some processing methods use sulphur-containing catalysts to convert fatty acid feedstocks [138]. Phosphorus damages catalytic converters used in emission control systems. Since catalytic converters are becoming more common in diesel powered equipment, maintaining low or no S and P levels will be of increasing importance. Combustion and UV fluorescence (UVF) detection has been used for accurate sulphur analysis in motor fuels (ASTM D 5453), but ICP-OES is rapidly gaining ground as the analytical method of choice for trace sulphur determination. ICP-OES procedures for determining S and P in canola oil and beef tallow for biodiesel production have been reported [139]. A crude degummed canola oil reference material (ID 05-183, ref. [140]) was utilised for QC purposes. There are no certified reference materials for S and P in tallow. Also XRF is well suited for measurement of S, P, K and Ca contents. Ion chromatography (IC) using conductivity detection is capable of simultaneously determining, within a reasonable time, the target cations Na+, K+, Mg2+ and Ca2+ in sub-ppm range after aqueous extraction of a biodiesel sample [102]. Additionally, the use of reagent-free ion-chromatography systems Table 12.22 Wavelengths and ICP-OES detection limits at each wavelength for key elements in a typical biodiesel sample Wavelength (nm)

Detection limit (ppm)

P 213.618 Ca 317.933 Ca 315.887 Mg 285.213 Mg 280.271 S 180.731 K 766.491 Na 589.592

0.0072 0.0014 0.0026 0.0007 0.0008 0.065 0.035 0.02

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with eluent generation simplifies the determination of cations in biodiesel by requiring only a source of deionised water to generate the methanesulphonic acid eluent used in the chromatographic method [141]. In comparison to AAS and ICP-OES the method for determination of the four cations of interest allows for simple sample preparation, simultaneous determination of the target cations, and limited interference from other elements in the sample. Besides the quantitation of cations, glycerol and antioxidants in biodiesel, a direct-injection IC method also permits determination of chloride and sulphate contents [101].

12.5.6 Physical property testing Density determination is usually a first step in biofuel analysis and provides a sum parameter which is ideal for plausibility checks on samples. A prerequisite for exact density measurement is precise temperature control and adjustment. The considerable viscosity difference between vegetable oils and their corresponding esters forms the basis of the use of viscometry in determining conversion of a vegetable oil to methyl esters [142]. The method is suitable 440 430 420 410

Flash point (K)

400 390 380 370 360 350 340 330 320 310 0.0

0.1

0.2 0.3 MeOH (wt%)

0.4

0.5

0.6

12.4 Flash point of biodiesel containing small amounts of methanol (after ref. [111]).

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for process control purposes due to its speed. Similar results were obtained from density measurements [142]. (See also Section 12.4.1). A European interlaboratory programme resulted in Stanhope Seta (UK)’s Setaflash method (EN-ISO 3679) being adopted in two European biofuel specifications (EN 14213 and EN 14214) as the only accepted test method for flash point. Test results being endorsed by interlaboratory cross-check programmes have established excellent correlations with other flash point test methods, including Pensky-Martens (ASTM D 93) and TAG (ASTM D 56). The flash point of biodiesel drops dramatically from 393 K to 333 K with only 0.2 wt% of free methanol (Fig. 12.4) [111]. Automated cloud and pour point analysers enable unattended operation with greatly improved reproducibility and repeatability. ISL’s (PAC Company, USA) CPP 5Gs determines pour point by tilting the sample. Precise optics detect cloud point in the specimen when wax crystals first appear.

12.6

Bibliography

Phenomenex Biofuel Guide LIT_5784_1, Essential Guide for Biofuel Analysis, Phenomenex® Inc., Torrance, CA (2008). Restek Application Note, Biodiesel Solutions, Restek Corporation, Bellefonte, PA (2008). R. Thomas, Practical Guide to ICP-MS, CRC Press, Boca Raton, FL (2008). Aspectrics Biodiesel Quality Analyzer (CD ROM), Aspectrics, Inc., Pleasanton, CA (2007). AOCS Methods for Biodiesel Feedstock Quality (CD-ROM), AOCS Press, Urbana, IL (2007). PerkinElmer Field Application Report, Biofuels Analysis, Shelton, CT (2006). US Department of Energy, Biodiesel Handling and Use Guidelines, 3rd edn, DOE/GO – 102006-2358, Oak Ridge, TN (2006). J. Van Gerpen, R. Pruszko, D. Clements, B. Shanks and G. Knothe, Building a Successful Biodiesel Business, AOCS Press, Urbana, IL (2006). Official Methods and Recommended Practices of the AOCS, 5th edn, AOCS Press, Champaign, IL (2004). W.W. Christie, Lipid Analysis, The Oily Press Lipid Library, Bridgwater (2003), Vol. 15. ThermoElectron Corporation, Biodiesel Analysis: Pure and Blended Biodiesel, Madison, WI (n.d.). Petroleum Analyzer Company (PAC), Biodiesel Analysis, Pasadena, TX (n.d.). E.N. Frankel, Lipid Oxidation, The Oily Press, Dundee (1998). J. Bailer, P. Hödl, K. de Hueber, M. Mittelbach, C. Plank and H. Schindlbauer,

Analytical methods and standards for quality assurance

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Handbook of Analytical Methods for Fatty Acid Methyl Esters Used as Diesel Fuel Substitutes, Research Institute for Chemistry and Technology of Petroleum Products, Vienna (1994). W.W. Christie, Gas Chromatography and Lipids – A Practical Guide, The Oily Press, Ayr (1992). R.G. Ackman, Analysis of Fats, Oils and Lipoproteins, AOCS, Champaign, IL (1991).

12.7

References

[1] J. Van Gerpen, Biodiesel Production and Fuel Quality, University of Idaho, Moscow, ID (2004). [2] G. Knothe, Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters, Fuel Proc. Technol. 86 (2005) 1059–70. [3] Official Methods and Recommended Practices of the AOCS, 5th edn. AOCS Press, Champaign, IL (2004). [4] J. Fischer, S. Howell and O. Costenoble, ASTM and CEN biodiesel specification status and global harmonization efforts, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [5] Tripartite Task Force Brazil, European Union and United States of America, White Paper on Internationally Compatible Biofuels Standards, ASTM International, West Conshohocken, PA (31 Dec. 2007), pp. 1–85. [6] S. Mahajan, S.K. Konar and D.G.B. Boocock, Determining the acid number of biodiesel, J. Am. Oil Chem. Soc. 83 (2006) 567–70. [7] C.H. Baxley and T.B. Rendel, Report of the volunteer group for compressionignition fuel research, SAE Journal (Transactions) 42 (1938) 27–36. [8] T.W. Ryan III and B. Stapper, Diesel fuel ignition quality as determined in a constant volume combustion bomb, SAE Techn. Paper Series 870586; SAE Intl. Congress and Exposition, Detroit, MI (1987). [9] A.A. Aradi and T.W. Ryan III, Cetane effect on diesel ignition delay times measured in a constant-volume combustion apparatus, SAE Techn. Paper Series 952352; also in Emission Processes and Control Technologies in Diesel Engines, SP–1119 (1995), pp. 43–56. [10] P. Wilharm, Apparatus and method for automatic determination of the cetane number, PCT Int. Publ. No. WO 2006/136349 A1 (28 Dec. 2006). [11] L.N. Allard, G.D. Webster, N.J. Hole, T.W. Ryan III, D. Ott and C.W. Fairbridge, Diesel fuel ignition quality as determined in the Ignition Quality Tester (IQT), SAE Techn. Paper Series 961182 (1996). [12] L.N. Allard, N.J. Hole, G.D. Webster, T.W. Ryan III, D. Ott, A. Beregszasy, C.W. Fairbridge, J. Cooley, K. Mitchell, E.K. Richardson, N.G. Elliott and D.J. Rickeard, Diesel fuel ignition quality as determined in the Ignition Quality Tester (IQT) – Part II. Fuel additives and performance (SP-1277), SAE Techn. Paper Series 971636 (1997). [13] L.N. Allard, G.D. Webster, T.W. Ryan III, G. Baker, A. Beregszasy, C.W. Fairbridge, A. Ecker and J. Rath, Analysis of the ignition behaviour of the ASTM D-613 primary reference fuels and full boiling range diesel fuels in the Ignition Quality Tester (IQTTM) – Part III. Gasoline and diesel fuel: performance and additives (SP-1479), SAE Techn. Paper Series 1999-01-3591 (1999).

564

Biodiesel science and technology

[14] L.N. Allard, G.D. Webster, T.W. Ryan III, A.C. Matheaus, G. Baker, A. Beregszasy, H. Read, K. Mortimer and G. Jones, Diesel fuel ignition quality as determined in the Ignition Quality Tester (Part IV), SAE Techn. Paper Series 2000-01-3527 (2000). [15] G. Knothe, A.C. Matheaus and T.W. Ryan, Cetane numbers of branched and straight-chain fatty esters determined in an ignition quality tester, Fuel 82 (2003) 971–5. [16] C.P. Maggi, Advantages of kinematic viscosity measurement in used oil analysis, Petro Ind. News 8(2) (2007) 18. [17] R. Kotrba, The fourth hour, Biodiesel Mag. 5(4) (2008) 71–6. [18] Environmental Protection Agency (EPA), Guidance for Biodiesel Producers and Biodiesel Blenders/Users, EPA, Washington, DC (2006). [19] J. Paligova, A. Kleinova, J. Mikulec and J. Cvengroš, Some remarks to the standard EN 14214 for FAME, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [20] D. Walsh, Quality control of biodiesel, Presentation at 47th Annual Eastern Analytical Symposium (EAS), Somerset, NJ (17–20 Nov. 2008). [21] J. Fischer, Biodiesel quality management: the AGQM story, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 204–10. [22] R.L. McCormick, T.L. Alleman, M. Ratcliff, L. Moens and R. Lawrence, Survey of the Quality and Stability of Biodiesel and Biodiesel Blends in the United States in 2004, NREL Techn. Rept. TP–540-38836, Golden, CO (Oct. 2005). [23] T.L. Alleman and R.L. McCormick, Results of the 2007 B100 Quality Survey, NREL Techn. Rept. TP-540-42787, Golden, CO (Mar. 2008). [24] T.L. Alleman and R.L. McCormick, Biodiesel fuel survey results for the USA, B100 and B20, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [25] C.M. Reddy, J.A. DeMello, C.A. Carmichael, E.E. Peacock, L. Xu and J.S. Arey, Determination of biodiesel blending percentages using natural abundance radiocarbon analysis: testing the accuracy of retail biodiesel blends, Environm. Sci. Technol. 42 (2008) 2476–82. [26] S. Rintoul, Meeting the challenges of biodiesel blend measurements with portable mid-infrared analyzers, Petro Ind. News 9(3) (June/July 2008) 43. [27] L. Pfalzgraf, I. Lee, J. Foster and G. Poppe, Effect of minor components in soy biodiesel on cloud point and filterability, Biorenew. Resources No. 4 (Special Suppl. to Inform) (2007) 17–21. [28] G. Knothe, Rapid monitoring of transesterification and assessing biodiesel fuel quality by NIR spectroscopy using a fiber-optic probe, J. Am. Oil Chem. Soc. 76 (1999) 795–800. [29] Aspectrics Biodiesel Quality Analyzer 1000/MultiComponentTM 2750 EP-NIR Analyzer, Aspectrics Inc., Pleasanton, CA (2007). [30] Anton Paar® Gmbh, Fast and firm on fuel: Biodiesel QC with Anton Paar, Petro Ind. News 9(2) (2008) 68. [31] B. Stefl, Quality testing at light speed, Biodiesel Mag. 5(2) (2008) 192–6. [32] R. Fillières, B. Benjelloun-Mlayah and M. Delmas, Ethanolysis of rapeseed oil: quantitation of ethyl esters, mono-, di- and triglycerides and glycerol by highperformance size-exclusion chromatography J. Am. Oil Chem. Soc. 72 (1995) 427–32. [33] A. Bouaid, Y. Diaz, M. Martínez and J. Aracil, Pilot plant studies of biodiesel

Analytical methods and standards for quality assurance

[34] [35] [36]

[37]

[38] [39] [40] [41]

[42]

[43] [44]

[45] [46] [47] [48] [49]

[50] [51] [52]

[53]

565

production using Brassica carinata as raw material, Catal. Today 106 (2005) 193–6. S. Wallace, Fuel quality testing for the fleet manager, Biodiesel Mag. 5(4) (2008) 114–20. P. Froome, Application study: biodiesel field test kit, Petro Ind. News 9(1) (2008) 23. (a) R.W. Hirthe, V.C. Gordon and R. Young, Biodiesel analysis utilising alternating current small-signal impedance spectroscopy – the i-SPECTM Q100 handheld analyser, Petro Ind. News 9(5) (2008) 12–13; (b) V.C. Gordon, R.W. Hirthe and K. Capizzi, Evaluation of the i-SPEC™ Q100 handheld biodiesel analyser in ten laboratories, Petro Ind. News 10(3) (2009) 36–7. A. Munack, J. Krahl, A. Marto and R. Bantzhaff, Basic research on a sensor for detection of biodiesel and development of prototypes as well as mass production, VDI-Berichte 1798 (2003) 331–6. M.E. Tat and J.H. Van Gerpen, Biodiesel blend detection with a fuel composition sensor, Appl. Engng. Agric. 19 (2003) 125–31. A. Munack and J. Krahl, Erkennung des RME-Betriebs mittels eines Biodiesel Kraftstoffsensors, Landbauforschung Völkenrode, Sonderheft 257 (2003). M. Bradley, Biodiesel (FAME) Analysis by FT-IR, Thermo Scientific Application Note 51258, Thermo Fisher Scientific Inc., Madison, WI (n.d.). R. Edler, The use of liquid scintillation counting technology for the determination of biogenic materials in fuels, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). G. Knothe, Analytical methods for biodiesel, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2003) pp. 62–75. G. Knothe, Analyzing biodiesel: standards and other methods, J. Am. Oil Chem. Soc. 83 (2006) 823–33. B. Freedman, E.H. Pryde and W.F. Kwolek, Thin-layer chromatography/flameionization analysis of transesterified vegetable oils, J. Am. Oil Chem. Soc. 61 (1984) 1215–20. J. Cvengroš and Z. Cvengrošová, Quality control of rapeseed oil methyl esters by determination of acyl conversion, J. Am. Oil Chem. Soc. 71 (1994) 1349–52. Analytik-Service Gesellschaft (Neusäb/Augsburg) test method. J. Baller and K. de Hueber, Determination of saponifiable glycerol in biodiesel, Fresenius J. Anal. Chem. 340 (1991) 186. Anon., Glycerine, Chem. Market Reporter 263, No. 21 (26 May 2003), 12. Ch. Plank and E. Lorbeer, Simultaneous determination of glycerol, and mono-, diand triglycerides in vegetable oil methyl esters by capillary gas chromatography, J. Chromatogr. A 697 (1995) 461–8. T. Ruppel and G. Hall, in Biofuels Analysis, PerkinElmer Field Application Report, PerkinElmer, Shelton, CT (2006). S. Greenhill (to Stepan Company), Method for determination of free and combined glycerin in biodiesel, PCT Int. Publ. No. WO 2004/059315 A1 (15 July 2004). J. Warden, L. Pereira, J. Cliff and A. Evans, GC Analysis of Biodiesel Using a High Temperature Carborane-Modified Siloxane Phase Column, Thermo Fisher Scientific Application Note, Runcorn (2007). T. Ruppel and G. Hall, Free and total glycerin in B100 biodiesel by gas chromatography, LC.GC Europe. Applications Book (March 2007), p. 45.

566

Biodiesel science and technology

[54] Anon., GC for quality control of biodiesel, Shimadzu News 3 (2006) 2–3. [55] J. Chang, R. Biniakewitz and G. Harkey, Determination of Free and Total Glycerin in B-100 Biodiesel via Method ASTM D 6584, Thermo Scientific Application Note 10192, Thermo Fisher Scientific Inc., San José, CA (n.d.). [56] M. Mittelbach, Diesel fuel derived from vegetable oils. V. Gas chromatographic determination of free glycerol in transesterified vegetable oils, Chromatographia 37 (1993) 623–6. [57] M. Mittelbach, G. Roth and A. Bergmann, Simultaneous gas chromatographic determination of methanol and free glycerol in biodiesel, Chromatographia 42 (1992) 431–4; Proc. Intl. Conf. on Standardisation and Analysis of Biodiesel, Vienna (1995), pp. 201–8. [58] P. Bondioli and L. Della Bella, An alternative spectrophotometric method for the determination of free glycerol in biodiesel, Eur. J. Lipid Sci. Technol. 107 (2005) 153–7. [59] P. Bondioli, C. Mariani, A. Lanzani, E. Fedeli and S. Veronese, Vegetable oil derivatives as diesel fuel substitutes. Analytical aspects. Note 2: Determination of free glycerol, Riv. Ital. Sost. Grasse 69 (1992) 7–9. [60] P. Lozano, N. Chirat, J. Graille and D. Ploch, Measurement of free glycerol in biofuels, Fresenius J. Anal. Chem. 354 (1996) 319–22. [61] S. Gong, Determination of free glycerol in biodiesel by using PDA UV-Vis spectrophotometer – colorimetric method, Petro Ind. News Annual Buyers’ Guide (2007), pp. 54–5. [62] M. Hájek, F. Skopal and J. Machek, Determination of free glycerol in biodiesel, Eur. J. Lipid Sci. Technol. 108 (2006) 666–9. [63] N. Nguyen, K. Kelly and S. Countryman, Reliable analysis of glycerin in biodiesel, Biodiesel Mag. 5(2) (2008) 142–6. [64] J. Warden and L. Pereira, GC analysis of biodiesel using a high-temperature carborane-modified siloxane phase column, LC.GC Europe Applications Book (Sept. 2007) 54. [65] B.L. Burger and J. de Zeeuw, High temperature stability problem solved with new metal columns – analysis of total glycerides in biodiesel oils by ASTM D 6584, Petro Ind. News 8(3) (2007) 42–3. [66] F. Munari, D. Cavagnino and A. Cadoppi, Determination of free and total glycerine in pure biodiesel (B100) by gas chromatography in compliance with EN 14105, LC.GC Applications Book (Dec. 2007) 15. [67] J. Huang, R. Chen, D. Cavagnino and E. Long, Analysis of Biodiesel Using LC/ MS with Limited Contamination of the LC/MS Interfaces, Thermo Fisher Scientific Application Note, Waltham, MA (2006). [68] M. Bowman, D. Hilligoss, S. Rasmussen and R. Thomas, Biodiesel: a renewable and biodegradable fuel, Hydrocarbon Proc. 85(2) (2006) 103–6. [69] Phenomenex Biofuel Guide LIT_5784_1, Essential Guide for Biofuel Analysis, Phenomenex® Inc. Torrance, CA (2008). [70] N. Nguyen, K. Kelly and S. Countryman, Reliable Analysis of Glycerin in Biodiesel Using a High-temperature Non-metal GC Column, Phenomenex Appl. Note TN2030, Phenomenex® Inc., Torrance, CA (2008). [71] T.A. Foglia, K.C. Jones, A. Nuñez, J.G. Phillips and M. Mittelbach, Comparison of chromatographic methods for the determination of bound glycerol in biodiesel, Chromatographia 60 (5/6) (2004) 305–11. [72] C. Plank and E. Lorbeer, Analysis of free and esterified sterols in vegetable oil methyl esters by capillary GC, J. High Resolut. Chromatog. 16 (1993) 483–7.

Analytical methods and standards for quality assurance

567

[73] V. Otten, Biodiesel analyser determines the quality of fatty acid methyl esters (FAME) blending stock for diesel fuel, LC.GC Europe Applications Book (Sept. 2007), p. 10. [74] F. Munari, D. Cavagnino and A. Cadoppi, An integrated approach to B100 biodiesel analysis by gas chromatography according to EN norms and ASTM standard methods, GC, LC, GC/MS and LC/MS Application Notebook, LC.GC Europe (May 2008), p. 24. [75] EN 14331, Liquid Petroleum Products – Separation and Characterisation of Fatty Acid Methyl Esters (FAMEs) from Middle Distillates, European Committee for Standardization, Brussels (2004). [76] J. McCurry, Analysis of biodiesel and biodiesel blends using capillary flow technology, Gulf Analytical Summit, Galveston, TX (1–7 May 2007), Paper T28. [77] M.P. Balogh, Alternative futures: biofuels and mass spectrometry, LC.GC Europe 22(4) (2009) 195–202. [78] M. Lechner, C. Bauer-Plank and E. Lorbeer, Determination of acylglycerols in vegetable oil methyl esters by on-line normal phase LC-GC, J. High Resolut. Chromatog. 20 (1997) 581–5. [79] C. Plank and E. Lorbeer, Minor components in vegetable oil methyl esters. I: Sterols in rapeseed oil methyl ester, Fett Wiss. Technol. 96 (1994) 379–86. [80] C. Plank and E. Lorbeer, On-line liquid chromatography-gas chromatography for the analysis of free and esterified sterols in vegetable oil methyl esters used as diesel fuel substitutes, J. Chromatogr. A 683 (1994) 95–104. [81] J.D. McCurry and C. Wang, Analysis of fatty acid methyl ester (FAME) content and distribution in biodiesel blends using heart-cutting 2D gas chromatography, Petro Ind. News 9(3) (2008) 48–50. [82] S. de Koning, H.-G. Janssen and U.A.Th. Brinkman, Characterization of triacylglycerides from edible oils and fats using single and multidimensional techniques, LC.GC Europe 19(11) (2006) 590–600. [83] P. Cunniff (ed.), AOCS Official Method 991.39 (Omega-3 Fatty Acids), AOAC International, Gaithersburg, MD (1995). [84] AOCS Method Ce 1b-89 (Fatty acid composition), Official Methods and Recommended Practices of the American Oil Chemists’ Society, 4th edn (D. Firestone, ed.), American Oil Chemists’ Society, Champaign, IL (1989). [85] M. Schreiner, Quantification of long chain polyunsaturated fatty acids by gas chromatography. Evaluation of factors affecting accuracy, J. Chromatogr. A 1095 (2005) 126–30. [86] S. Schober and M. Mittelbach, Determination of polyunsaturated fatty acid methyl esters in biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [87] T.A. Foglia, K.C. Jones, M.J. Haas and W.N. Marmer, Biodiesel HPLC methods: determination of glycerol and blend level, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [88] B. Trathnigg and M. Mittelbach, Analysis of triglyceride methanolysis mixtures using isocratic HPLC with density detection, J. Liq. Chromatogr. 13 (1990) 95–105. [89] T.A. Foglia and K.C. Jones, Quantitation of neutral lipid mixtures using highperformance liquid chromatography with light scattering detection, J. Liq. Chromatogr. Related Technol. 20 (1997) 1829–38. [90] M. Hol�apek, P. Jandera, J. Fischer and B. Prokeš, Analytical monitoring of the

568

[91]

[92]

[93]

[94] [95] [96]

[97]

[98]

[99]

[100] [101]

[102]

[103] [104]

[105] [106] [107]

Biodiesel science and technology production of biodiesel by high-performance liquid chromatography with various detection methods, J. Chromatogr. A 858 (1999) 13–31. M. Hol�apek, P. Jandera and J. Fischer, Analysis of acylglycerols and methyl esters of fatty acids in vegetable oils and biodiesel, Crit. Rev. Anal. Chem. 31 (2001) 53–6. P.J. Lee and A.J. Di Gioia, One methodology for FFA, FAME and TAG analysis in biodiesel using ultra performance LC and ELSD and photodiode array detection, Petro Ind. News 8(4) (2007) 22–3; Waters Application Note, Milford, MA (2007). J. Huang, R. Chen, D. Cavagnino and E. Long, Analysis of biodiesels using LCMS, LC.GC Europe Applications Book (Sept. 2007) 53; Thermo Fisher Scientific Application Note (2006). R. Chen and D. Cavagnino, Analyze biodiesel using liquid chromatography/mass spectrometry instrumentation, Hydrocarb. Proc. (Feb. 2008) 107–10. T.A. Foglia, K.C. Jones and J.G. Phillips, Determination of biodiesel and triacylglycerols in diesel fuels by LC, Chromatographia 62 (2005) 115–19. J.W. Diehl and F. DiSanzo, Determination of total biodiesel fatty acid methyl, ethyl esters, and hydrocarbon types in diesel fuels by supercritical fluid chromatographyflame ionization detection, J. Chromatogr. Sci. 45 (2007) 690–3. J. Cole, J. Lefler and R. Chen, Fast separation of FFA, FAME and glycerol for biodiesel analysis by supercritical fluid chromatography, LC.GC Europe. The Applications Book (Mar. 2008), pp. 44–6. D. Darnoko, M. Cheryan and E.G. Perkins, Analysis of vegetable oil transesterification products by gel permeation chromatography, J. Liq. Chrom. Related Technol. 23 (2000) 2327–35. G. Reinhold, GPC/SEC analysis of mono-, di-, triacylglycerides and glycerol according to European Pharmacopoeia, LC.GC Europe. The Applications Book (Mar. 2008) p. 27. F. Lacoste, F. Dejean and E. Brenne, Ester content determination in biodiesel by HPLC-SEC, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). G. Bogenschütz and T. Kolb, Ion Chromatographic Determination of Anions, Cations and Organic Acids in Biofuels, Deutsche Metrohm Application Note, Filderstadt (2007); http://products.metrohm.com. A. Steinbach, A. Wille and N.H. Subramanian, Biofuel analysis by ion chromatography, LC.GC Europe. The Applications Book (March 2008), pp. 35–8. A. Al-Alawi, F.R. Van der Voort and J. Sedman, New FTIR method for determination of FFA in oils, J. Am. Oil Chem. Soc. 81 (2004) 441–6. N.G. Siatis, A.C. Kimbaris, C.S. Pappas, P.A. Tarantilis and M.G. Polissiou, Improvement of biodiesel production based on the application of ultrasound: monitoring of the procedure by FTIR spectroscopy, J. Am. Oil Chem. Soc. 83 (2006) 53–7. G.F. Zagonel, P. Peralta-Zamora and L.P. Ramos, Multivariate monitoring of soybean oil ethanolysis by FTIR, Talanta 63 (2004) 1021–5. J. Boyd and S. Rintoul, Biodiesel analysis with mid infrared – from feedstock to fuel, Petro Ind. News 8(3) (2007) 44–5. A. Bírová, E. Švajdlenka, J. Cvengroš and V. Dostálíková, Determination of the mass fraction of methyl esters in mixed fuels, Eur. J. Liquid Sci. Technol. 104 (2002) 271–7.

Analytical methods and standards for quality assurance

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[108] EN 14078, Liquid Petroleum Products – Determination of Fatty Acid Methyl Esters (FAME) in Middle Distillates – Infrared Spectroscopy Method, European Committee for Standardization, Brussels (July 2004). [109] D. Armstrong, S. Williams and D. Wooten, Biodiesel concentration measurements using Spectrum OilExpress, Petro Ind. News 8(3) (2007) 36–7. [110] T. Roder, S. Tadepalli and M. Polczynski, Applying genetic algorithms to FTIR spectrograms for biodiesel/diesel blend ratio measurement, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [111] O. Sauer and H. Pichler, Fit for biofuels and blends, Petro Ind. News 9(6) (2008) 42. [112] G.P. Ritz and M.C. Croudace, Biodiesel or FAME (Fatty Acid Methyl Ester): Mid-infrared Determination of Ester Concentration in Diesel Fuel, SpectroSpec/ Petroleum Analyzer Co. Application Note, Petroleum Analyzer Co., Pasadena, TX (2002). [113] M.C. Croudace, Analysis of fuel properties by mid-infrared spectroscopy, World Refining 11 (2001) 36–9. [114] D. Shiley, Demystifying near-infrared analysis for biodiesel production, Biodiesel Mag. 5(5) (2008) 94–7. [115] S. Scherer, W. Kosman, C. Heil and J. Hirsch, Testing shows benefits of nearinfrared analysis, Biodiesel Mag. 5(6) (2008) 106–9. [116] Z. Christian and M. Mittelbach, Critical evaluation of NIR-spectroscopy as an analytical method in biodiesel production, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [117] Aspectrics Application Note, Simultaneous Measurement of Water, Methanol and Total Glycerin in Biodiesel Synthetic Samples Using a MC2750 EP-NIR Spectrometer, Aspectrics Inc. Pleasanton, CA (2007). [118] Cropscan 2000 BF Bio-Fuels Analyzer, NIR Technology Systems Pty Ltd., Australia. [119] A. Niemöller and H. Li, The benefit of at-line and in-line analysis by FT-NIR and FT-IR spectroscopy for the biodiesel industry, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [120] J.S. Oliveira, R. Montalvão, L. Daher, P.A.Z. Suarez and J.C. Rubim, Determination of methyl ester contents in biodiesel blends by FTIR-ATR and FTNIR spectroscopies, Talanta 69 (2006) 1278–84. [121] Rapid Process and Quality Control of Biodiesel, FOSS Application Note 273, FOSS, Hilleroed (May 2008). [122] G. Knothe, Determining the blend level of mixtures of biodiesel with conventional diesel fuel by fiber optics NIR spectroscopy and 1H nuclear magnetic resonance spectroscopy, J. Am. Oil Chem. Soc. 78 (2001) 1025–8. [123] G. Knothe, Monitoring the turnover of a progressing transesterification reaction by fiber-optic near infrared spectroscopy with correlation to 1H-NMR spectroscopy, J. Am. Oil Chem. Soc. 77 (2000) 489–93. [124] G. Gelbard, O. Brès, R.M. Vargas, F. Vielfaure and U.F. Schuchardt, 1H nuclear magnetic resonance determination of the yield of the transesterification of rapeseed oil with methanol, J. Am. Oil Chem. Soc. 72 (1995) 1239–41. [125] T. Dimmig, W. Radig, C. Knoll and T. Dittmar, 13C-NMR-Spektroskopie zur Bestimmung von Umsatz und Reaktionskinetik der Umesterung von Triglyceriden zu Methylestern, Chem. Tech. (Leipzig) 51 (1999) 326–9. [126] G.F. Ghesti, J.L. de Macedo, V.S. Braga, A.T.C.P. de Souza, V.C.I. Parente,

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[127]

[128]

[129] [130] [131] [132] [133] [134] [135]

[136] [137] [138]

[139] [ 140] [141] [142]

Biodiesel science and technology E.S. Figuerêdo, I.S. Resck, J.A. Dias and S.C.L. Dias, Application of Raman spectroscopy to monitor and quantify ethyl esters in soybean oil transesterification, J. Am. Oil Chem. Soc. 83 (2006) 597–601. A. Neumann, T. Jebens and V. Wierzbicki, PetroOXY: a new method for determination of oxidation stability of diesel-fuels, biodiesel and biodiesel blend, Petro Ind. News 8(6) (2008) 30–1. C.C. Conconi, P. Grassato, W. Capelupi, L.C.F. Canale and G.E. Totten, Evaluation of oxidation stability of biodiesel, diesel fuel and their mixtures using PDSC (Pressurized Differential Scanning Calorimetry) method, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). P. Ye, Weighing oxidation stability tests for biodiesel, Biodiesel Mag. 5(7) (2008) 102–5. B.-R. Altmann, Biofuels. Requirements, properties, and effects of blending with conventional fuels, Erdoel, Erdgas, Kohle 121 (2005) 156–9. Eastman Chemical Company Publication P296, Oxidative Stability of Biodiesel, Eastman Chemical Co. Kingsport, TN (2007). R. Shah and V. Colantuoni, Testing of biodiesel products: key titration applications, Petro Ind. News 9(4) (2008) 54. R. Schlink and B. Faas, Water content determination in biodiesel according to EN ISO 12937, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). Metrohm Application Note H-29, Determination of Free Fatty Acids in Edible Fats and Oils, Metrohm, Herisau (2003). M.J.D. Carneiro, M.A. Feres Jr and O.E.S. Godinho, Determination of the acidity of oils using paraformaldehyde as a thermometric end-point indicator, J. Braz. Chem. Soc. 13 (2002) 692–4. Anon., Analysis of biodiesel using Spectro Arcos ICP-OES with radial plasma observation, Petro Ind. News 8(6) (2008) 39. M. Cassap, Efficient biodiesel analysis using ICP emission spectrometry, Petro Ind. News 10 (Mar. 2009) 34–5. J.A. Kinast, Production of Biodiesel from Multiple Feedstocks and Properties of Biodiesels and Biodiesel/Diesel Blends, NREL, US Dept. of Energy Laboratory, Golden, CO (2003). M. Ostrovsky, T. Loukianova, D. Hilligoss and P. Wee, in Biofuels Analysis, PerkinElmer Field Application Report, PerkinElmer, Shelton, CT (2006). Cargill Ltd., PO Box 190, Cheirot Rd., Clavet, Sask., S0K 0Y0, Canada. D. Hurum, B. De Borba and J. Rohrer, Ensuring biodiesel quality through lab analysis, Biodiesel Mag. 5(8) (2008) 98–101. P. De Filippis, C. Giavarini, M. Scarsella and M. Sorrentino, Transesterification process for vegetable oils: a simple control method of methyl ester content, J. Am. Oil Chem. Soc. 72 (1995) 1399–404.

13

Valorisation of the glycerol by-product from biodiesel production

Abstract: The economic viability of the transesterification process of triglycerides is enhanced by valorisation of the main by-product, glycerol. Glycerol quality depends on the biodiesel process characteristics. This chapter describes new high-volume products and applications based on direct use of crude glycerol as a platform substrate, cost-effective purification processes, and innovative commercial use of glycerol by (bio)catalytic conversion into commodity chemicals by selective oxidation, hydrogenolysis and dehydration, pyrolysis and gasification, steam reforming, thermal reduction, selective (trans)esterification and etherification, oligomerisation and polymerisation, chlorination and carboxylation. Key words: Propanediols, biomethanol, aqueous-phase reforming, glycerol (poly)ethers, epichlorohydrin.

13.1

Introduction

A critical issue in biodiesel production is economic viability, specifically enhanced by the profitable use of the glycerol by-product and waste streams (salts) in other industrial processes [1]. Biodiesel producers sell raw glycerol to be refined to remove the contaminants and make it suitable for a wide range of applications. The credit for this sale is used to offset production costs of biodiesel. A biodiesel plant is best combined with a glycerol recovery facility and/or further downstream operations, which improves the economic viability of the transesterification process. Meanwhile, however, glycerol is no longer a high-priced commodity. In fact, in March 2007 glycerol prices had plummeted to about one-third the level of 2004. The trend is one of long-term decline up to the point that currently the by-product glycerol makes little contribution to the overall biodiesel economics. The production of marketable chemicals via catalytic transformation of biosustainable resources employed as substitutes for fossil fuels is a global challenge. Effective utilisation of glycerol for the synthesis of high valueadded products (bulk chemicals or fuels) is of great industrial interest in the promotion of biodiesel commercialisation and development. Equally challenging is the fact that glycerol obtained as a by-product from the biodiesel industry is usually crude and impure. Consequently, the industry needs the following: 571

572

Biodiesel science and technology

∑ ∑

new products and applications based on direct use of crude glycerol; cost-effective purification processes to refine raw glycerol from biodiesel manufacturing; ∑ a combination of separation of crude glycerol with catalytic conversion; and ∑ direct biocatalytic conversion of crude glycerol. Although the improvement of the economic viability of the biodiesel industry through new applications of crude glycerol is still largely unsettled, higher quality biodiesel glycerol can nowadays be obtained directly with heterogeneous catalysed continuous processing rather than using homogeneous processes. This presents a better basis for conversion to value-added chemicals and fuels. Glycerol valorisation is a very active field of research [2–8]. Several European research projects were funded in the recent past with the aim of investigating new outlets for glycerol, including AIR3-CT94-2218 ‘Reactivity of fatty acid esters and glycerol: new methods’; FAIR-CT96-1829 ‘Polyglycerol chemistry, ecology and applications of polyglycerol esters’; and FAIR-CT973884 ‘Chemical technical utilisation of vegetable oils’ (CTVOnet). More recently, a Supermethanol project was launched (www.supermethanol.eu). In the US an AOCS Glycerin Innovation Award was launched in 2002 and first assigned to the development of dibutoxyglycerol (DBG). The 2008 Glycerin Innovation Award was recently assigned to R. Ashby, D. Solaiman and T. Foglia (USDA Agriculture Research Service Eastern Regional Research Center, Wyndmoor, PA) for new eco-friendly uses of natural glycerin (see ref. [5]). Also the SDA/NBB Glycerine Innovation Award recognises outstanding achievement for research in new applications for glycerol, with particular emphasis on commercial viability.

13.2

Industrial glycerol production

The terms glycerine, glycerin, and glycerol are used interchangeably although slight differences exist in their definitions and use. Glycerol is the pure chemical compound 1,2,3-propanetriol. Glycerine is the commonly used commercial name for products whose principal component is glycerol. Glycerin refers to purified commercial products containing 95% or more of glycerol. In this text we almost invariably use ‘glycerol’ without distinction. Almost all operations carried out in oleochemistry lead to the generation of the co-product glycerol. This chemical has been obtained mainly by: ∑ pressurised hydrolysis of vegetable oils (fatty acids); ∑ transesterification (alcoholysis) of triglycerides (biofuels); ∑ saponification of triglycerides with alkali (soaps); ∑ chemical synthesis from C3 derivatives (petrochemicals); and

Valorisation of the glycerol by-product

∑

573

controlled microbial fermentation of sugars, molasses and other carbohydrates.

The importance of these various routes has strongly varied with time. In fact, some former starting materials for glycerol (such as epichlorohydrin) are nowadays being proposed as glycerol products (see Section 13.5.7). Following the emergence of synthetic detergents in the 1940s, soap manufacturing from fatty acids was reduced and various synthetic processes for glycerol were developed (by IG Farben, Degussa, Leuna, Shell, Olin Mathieson and others), based mainly on allyl chloride (preferred; or its conversion product epichlorohydrin), allyl alcohol and some other petrochemicals (Fig. 13.1). Nowadays, synthetic processes for commercial production of glycerol

H 2C

H C

Cl2

CH2

H C

CH3

H 2C

H C

O2

CH

H 2C

O

Cl

Allylchloride

Propylene

Acrolein

HCIO OH– H C H2C

HCIO OH–

O

CH3

Li3PO4

H2O2 H C

H2C

H2C

OH

H C O

CH2

Allyl alcohol

CH2 Cl

Epichlorohydrin

H2 O OH–

H C

H2C

H2 O

O

CH2 OH

Glycidol

–

OH

H2C

H C OH

HO

H 2O OH– CH2 OH

Glycerol

13.1 Synthetic routes to glycerol.

H2

H2C

H C O

CH O

Glycilaldehyde

574

Biodiesel science and technology

account for only about 10% of global production (see Table 13.1) and 25% of US production capacity (134 kt/yr). Glycerol production by yeast fermentation has been known since Pasteur [9]. In Saccharomyces cerevisiae (bakers’ yeast), glycerol is a by-product of the fermentation of sugar to ethanol. Glycerol production by microbial fermentation is unable to compete with chemical synthesis from petrochemical feedstocks due to low glycerol yields and difficulty with extraction and purification of glycerol from broth. Not surprisingly, the production cost of glycerol obtained by fermentation is generally much higher than that of glycerol obtained from vegetable oils and fats. Recently, significant improvements have been made in glycerol production from glucose using osmotolerant yeasts on a (limited) commercial scale in China (10 kt/yr). Glycerol production by microbial fermentation is reviewed in ref. [10]. Glycerol from renewable materials denotes a particular glycerol obtained during conversions of fats or oils of plant or animal origin in general, such as saponification or hydrolysis reactions, or else glycerol obtained in the production of biodiesel by transesterification. Currently about 80% of US production and 90% of global production are from natural glycerides. The primary sources of glycerol include tallow (TLW), palm kernel oil (PKO) and coconut oil (CNO). Procter & Gamble is the largest natural glycerol producer. Animal fats have been a main raw material for glycerol. However, in view of BSE (bovine spongiform encephalopathy), use of glycerol for human contact (food, pharmaceutical, cosmetics, etc.) nowadays favours glycerol of vegetable origin. Global glycerol production increased from 650 kt in 1995 to almost 900 kt in 2006, of which 600 kt was from biodiesel production. Table 13.1 shows the global production volume of natural and synthetic glycerol by source. In 2001, European biodiesel production accounted for 11% of glycerol production or about 80 kt. Before 1995, this source of glycerol was non-existent. In the past, US glycerol production has oscillated in the range of 130 000–160 000 MT/yr. Nowadays, the oleochemical (over)production of glycerol has greatly suppressed synthetic glycerol and biodiesel glycerol production is becoming a major source. In 2007 US biodiesel manufacturers produced 187 kt of crude Table 13.1 Global sources of glycerol production (2001) (after ref. [11]) Process

Global production (%)

Fatty acids Soap manufacture Methyl esters for detergent alcohols Methyl esters as biodiesel Synthetic Fermentation Other

41 21 14 11 9 – 4

Valorisation of the glycerol by-product

575

glycerine, as compared to 150 kt from other sources. The large surplus of glycerol by-product which entered the chemical market has caused closure of existing glycerol plants. Glycerol is now part of the fuel market, which has generated 800 kt of the product in 2007. If the EU 2010 target is achieved, biodiesel demand could then increase to 9.8 Mt/yr (see Table 1.2), thus co-producing about 1 Mt/yr of glycerol. This quantity exceeds the present total world consumption of glycerol. Moreover, if the US replaces 2% of the on-road diesel with biodiesel by 2012, almost 333 kt/yr glycerol would additionally be added to the market. This would rapidly saturate even the current Chinese export market (about 0.1 Mt/yr). USDA-Foreign Agricultural Service forecasts in June 2007 suggest an increase in glycerol from biodiesel production by 2010 of over 167% from 2006. Glycerol amounts typically to about 10% of the product output of a biodiesel fuel (BDF) production process, although the yield depends on the feedstock composition. For low FFA feedstocks (RSO, SBO, PMO, TLW, UCO) some 103.6–108.9 t/ton feedstock is obtained, as compared to only 21.8 t glycerol/ton palm fatty acid distillate (P-FAD) [12], (see Table 7.3). Most biodiesel companies (70%) end up with a crude glycerin by-product. Some 20% is taking glycerin to technical grade and only 5% pharmaceutical grade; burning is another outlet. Although at present (2008) the global production of biodiesel is still fairly limited, markets have already reacted strongly to the increased availability of this polyalcohol with rapidly dropping prices which tend to destabilise the free market for oleochemicals. At the same time, the excess market supply of glycerol in biofuel and biolubricant applications could also easily set the biodiesel industry backwards. Glycerol, produced in many countries, is now considered as a major platform feedstock for a range of chemical processes (Fig. 13.2) and an important building block for future biorefineries [13]. ADM, Ashland, BioMCN, Cargill, Dow, Senergy Chemical, Solvay and others are set to produce glycerol-derived industrial products such as methanol, ethylene glycol (EG), propylene glycol (PG) and epichlorohydrin (ECH).

13.3

Glycerol purification

Several grades of crude glycerol are marketed, including soap-lye crude glycerol (from soap-making processes), which contains ~80% glycerol, 10–15% water and 5% salts, and hydrolysis crude glycerol (from hydrolysis of fats), which contains ~ 88–91% glycerol and a small amount of organic salts. Technical grade glycerin is a refined, high-purity product (98.0% minimum) that is water white with most of its contaminants completely removed (no methanol, soaps, salts or other foreign matter). Technical grade

CH

glycidol

glycerol carbonate ethers and esters

O O

C

C H2

Representative glycerol derivatives

O

H2C CH H2C OH

Fermentation

HO

H2 C

HO

H2 C

H2 C CH

H2 C

HO

OH

TEMPO

HO

HOOC

H2 C

OH

Sorona (DuPont)

O

H 2C

O

New polyesters, nylons

O

PLA analogues

fatty acids (e.g. oleic acid)

Catalytic oxidation

Selective esterification

HO

13.2 Glycerol chemistry.

OH CH

C

C H

C

O

Chlorination

H2 C

OH C

C

O

HO

H2 C

OH CH

CH2

Highly branched polymers

OR

ROH FAAEs (biodiesel)

OH

H C

OH

OH

saponification

C H2

O C

glycerol

partial saponification triglycerides

C H2

glycerol carbonate

Fermentation

Existing markets

polyglycidol new hyperbranched systems dendrimers catalysts alcohols

Cl

H2 C

O C H

CH2

Epoxy resins

Biodiesel science and technology

coatings polymers gas separation solvents cosmetics personal care detergents

OH

576

O H 2C

Valorisation of the glycerol by-product

577

glycerin is not subject to governmental regulatory control. The most common purity found in the marketplace is 99.5% minimum glycerol. Several other grades of refined glycerol, such as high-gravity and USP/FCC (vegetableor tallow-based), are marketed. USP-grade glycerol (96–99.5%) obviously meets the requirements of USP, is controlled by the FDA, classified as GRAS (generally recognised as safe) and is suitable for use in food, personal care, cosmetics and pharmaceuticals. The European Pharmacopæia (PH.EUR) grade is similar to the USP. Also the chemically pure (CP) grade designates a glycerol that is about the same as the USP. Also available is food grade kosher glycerol (99.5–99.7%), which typically commands a higher value in the marketplace. To be Kashrut endorsed, glycerol must be from 100% vegetable sources instead of from animal tallow. The purity of by-product glycerol is of key economic and technological concern in conventional industrial biodiesel processes. Small biodiesel plants usually discard the glycerol by-product as waste. The quality of glycerol depends on the biodiesel process characteristics. Crude glycerol from a biodiesel plant has been described as the wastebasket of the biodiesel process, in the sense that this phase collects the catalyst, much of the oil impurities, methanol and water. Crude glycerol with 50% purity (containing methanol, water, catalyst residues, salts, free fatty acids, unreacted mono-, di-, and triglycerides, methyl esters and other organic matter) has few direct uses and is of low value; even its fuel value is marginal. Depending on the type of catalyst route and separation process used, the glycerol purity can reach 80–95%. In conventional industrial biodiesel processes using methanol transesterification of vegetable oils in the presence of a homogeneous catalyst (e.g. NaOH or NaOCH3), sodium is recovered from the glycerol phase as sodium glycerate. An acid neutralisation step with, for example, aqueous HCl is required to convert sodium glycerate to glycerol (see Fig. 13.3). Glycerol is obtained as an aqueous solution containing NaCl. Such crude glycerol is typically sold to industrial glycerol refiners at low cost. Upgrading crude glycerol in the fatty acid industry requires the removal of dissolved salts, elimination of colour and fat and oil impurities, concentration (evaporation of water) and/or distillation so that it is acceptable as either (higher valued) food grade or pharmaceutical grade. Glycerol purification for industrial uses is generally expensive. The cost of recovering high-quality glycerol from biodiesel glycerol is lower than that of soap glycerol [14]. The purity requirements for the emerging applications of glycerol vary, and are often intermediate to the crude and refined grades previously established for the classical applications. Purification is required to transform crude biodiesel glycerin to a usable state for existing or emerging uses. The salt content in crude glycerin, stemming from the use of homogeneous alkaline catalysts (typically 5–7%) makes conventional techniques cost intensive. Ion-exchange processes or

578

Biodiesel science and technology RCOOCH2 RCOOCH RCOOCH2 + CH3OH

3 RCOOCH3 (Biodiesel) NaOH

CH3OH

or NaOCH3

CH2OH

+

CH2ONa

CHOH

CHOH

CH2OH

CH2OH

+

CH3ONa RCOONa

Neutralisation step aq. HCl CH2OH Glycerol

CHOH CH2OH

CH3OH +

RCOOH Fatty acid

+

NaCl H2O

13.3 Reactions in conventional homogeneous-catalysed transesterification of vegetable oils.

(energy-intensive) vacuum distillation in biodiesel manufacturing are the most commonly practised methods for purifying glycerin, which allow obtaining a highly refined (97%+ purity) product. Classical ion-exchange techniques are uneconomical in view of chemical regeneration costs for the resins exposed to the high salt content of glycerin from homogeneous catalysed processes. Rohm & Haas Co./Novasep Process have recently developed a patentpending crude biodiesel glycerin purification technology (Ambersep™ BD50 process) which allows production of a glycerol product with 99.5% purity or high-quality glycerol with 5–10 ppm salt content (employing an ion-exchange demineralisation unit) (Fig. 13.4). The overall process is characterised by a low energy requirement and does not involve vaporisation of glycerol. Water is used for chromatographic separation. The energy consumption is essentially limited to removal of water from the purified glycerol after purification. The technology should benefit biodiesel producers in terms of a value-added revenue stream due to the disparity in crude and purified glycerol prices in global markets. Future glycerol markets benefit from a new low-cost purification strategy. Recently, an economic solution for purification of crude glycerol compositions by electrodialysis, filtration through nanofiltration or reverse osmosis filters has been proposed, which can yield a colourless liquid with low salt content, equivalent to fuel grade, technical grade, or pharmaceutical grade glycerol [15]. Similarly, Cimbria Sket GmbH (Magdeburg, Germany)/ Bratney Cos. (Des Moines, IA) have introduced an improved glycerin refining process that removes odour from the final product.

Valorisation of the glycerol by-product

579

Crude glycerol 95% Glycerol 5% NaCl Pre-heating

NaCl Crystallisation

Raffinate

Heating 363 K

Heating 363 K

Safety filtration

Safety filtration

Degassing

Degassing

CHR

Cooling 313 K (optional)

Secondary NaCl glycerol Effluent

IEX (optional) Concentration

Condensates

Soft water

Condensates

Refined glycerol

13.4 AmbersepTM BD50 process steps for purification of crude glycerin from biodiesel. CHR = chromatographic separator; IEX = ionexchange column (after ref. [16]).

The projected volume production of crude glycerol over the next five years will exceed the present commercial demand for purified glycerol. Consequently, purifying the by-product glycerol for use as a commodity in applications in the pharmaceutical, cosmetics and food industries is not a viable option for the biodiesel industry. New processes are needed which co-produce high-purity glycerol. Unlike traditional homogeneous catalysed biodiesel processes, in the highly efficient, continuous solid-catalyst EsterfipHTM process (IFP-Axens), high-purity biodiesel and top-grade glycerol (limpid, colourless and salt-free) of unequalled purity (> 98%) are obtained directly (see Section 15.3, pp. 729–31). The catalytic reactive distillative Yellowdiesel process (see Section 11.2) for making biodiesel from high FFA oils produces > 99.9% purity glycerol [17].

13.4

Industrial uses and markets

Industrial use of glycerol is derived from its chemistry (see Fig. 13.2). Use of glycerol is extremely fragmented varying from its traditional applications

580

Biodiesel science and technology

(pharmaceutical, personal care products, food additives) to more recently developed ones (animal feed, carbon feedstock in fermentations, polymers, surfactants, intermediates and lubricants) [18] (see Table 13.2). Although glycerol is used in foods and personal care products (in particular toothpastes), at present there is no large-scale industrial demand. Indeed, around 200 kt are incinerated in the US each year. Glycerol is an important chemical compound which can be used, for example, as a solvent, a humectant additive, a textile auxiliary, an additive to heat transfer and power transmission fluids and in many other fields. The industrial uses of glycerol are determined both by its physical and chemical properties. As a high-boiling, viscous, hygroscopic substance, glycerol is used as an antifreeze, in the manufacture of cosmetics (skin creams, toothpastes, soaps) and pharmaceuticals, in tobacco moisturing (protection against excessive humidity), and as an auxiliary agent for printing inks, adhesive cements, etc. Cummins Filtration, Inc. (Nashville, TN) has recently developed a new heavy-duty engine antifreeze/coolant based on glycerol (Fleetguard ES Compleat™ Glycerin), replacing ethylene glycol (EG) and propylene glycol (PG). As a triol, glycerol is used for the manufacture of alkyd resins (polycondensation products of glycerol and phthalic anhydride) and glycerol tripolyethers (by ethoxylation or propoxylation), applied as tensides and also as starting materials for the reaction with diisocyanates to give polyurethanes. Glycerol competes with sorbitol and propylene glycol in food, beverage and tobacco applications. Mono- and diesters of glycerol with fatty acids are used on a large scale in food production. Although glycerol is less suitable as a heat source due to its low calorific value (18 000 kJ/kg), typically less than the Btu content of diesel No. 2, it may be used for energy production and in low-grade heat processes. The surplus of glycerol in Japan is currently being disposed of in a dedicated purpose incinerator. In a production method of diesel fuel oil from waste oil, glycerol was recycled for use as a fuel for boilers, heat recovery type incinerators or

Table 13.2 Main traditional applications of glycerol ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Solvent Cosmetic and pharmaceutical compositions Textile auxiliary Antifreeze Tobacco moisturing Auxiliary agent for printing inks, adhesive cements Component to alkyd resins Lubricant Tenside Food additive (E422) Explosive (nitroglycerol)

Valorisation of the glycerol by-product

581

the like. Advantages of glycerin as a fuel are non-toxicity, biodegradability and high flash point. Aquafuel Research, Ltd. (Sittingbourne, UK) has developed commercially available technology allowing glycerin to be burned in off-the-shelf diesel generators that are used in combined heat and power applications; 1 t of glycerin produces approximately 1.7 MWh of electricity and 2 MW of heat. The technology is expected to be installed at Greenergy, a UK-based biodiesel producer. Also Diversified Energy Corp. (Gilbert, AZ) has developed an efficient crude glycerin (ex biodiesel) combustion system. By the end of 2009 Xcelplus Global Holdings, Inc. (Topping, VA) expects to produce 60 kt of two types of glycerin-based liquid fuels, GlyClene™ (for standard turbine engines in industrial boiler applications) and GlyCoal™ (for power plants), which are obtained by chemical and thermal heat processing of waste glycerin sourced from biodiesel plants. The glycerol market is currently undergoing radical changes, driven by very large supplies of glycerol arising from biodiesel production. To date, glycerol is too expensive to be used as a fuel, but as biodiesel production increases (EU target: 9.8 Mt/yr by 2010), its availability could greatly exceed demand for traditional use making it a cost-effective raw material for the preparation of fuels. Wiedermann et al. [19] have proposed a glycerol-based fuel for diesel engines consisting of glycerol 25–70, soaps 5–40, water 3–25 and methanol 0.1–5.0 wt%, as a by-product of biodiesel production by transesterification of vegetable oils and/or animal fats. Disposal of the byproducts can be avoided. Conversion of biomass using anhydrous glycerol and Na2CO3 or KOH at 540–565 K allows a liquid fuel to be obtained for blending gasoline as an alternative engine fuel [20]. Glycerol in itself is unsuitable for fuel purposes; its combustion heat is low, and its viscosity is orders of magnitude higher than that of the original triglyceride. Yet, a large-volume utilisation of glycerol would be its ‘feedback’ as fuel or fuel additive. In PCT Int. Publ. No. WO 2009/007306 A1 to Oleo SA [21], Noel discloses a fuel composition for internal combustion engines, such as 85 vol% straight glycerol and 15 vol% viscosity modifier (typically an alcohol). For fuel use, in admixture with hydrocarbons, glycerol needs to be chemically modified to suitable derivatives, such as acetals, ketals, etc. [22–24] (see Section 13.5.6). But biodiesel may not be diluted too much with these derivatives, because of their low combustion heat. Moreover, since biodiesels themselves are only additives (in 5–20%) to petrodiesel, it is obvious that utilisation of the glycerol glut in this form can only be limited. It follows that direct utilisation of triglycerides and derivatives as fuels is still of continuing interest (see also Section 4.3). In PCT Int. Publ. No. WO 2008/096187 [25], Thész, Boros and Király (TBK) disclose a new method for reduction of the viscosity and molecular mass of triglycerides by reacting the glycerol-triester with another ester instead of an alcohol (interesterification, see also Eqn 10.1), namely with

582

Biodiesel science and technology

methyl/ethyl esters of short-chain (C1-C6) carboxylic acids, in such a way that the acyl groups exchange only partially, e.g. as follows:

CH2-OCO-Long Ù CH-OCO-Long + Short-COO-Methyl Æ Ù CH2-OCO-Long

CH2-OCO-Short Ù CH-OCO-Long + Long-COO-Methyl Ù CH2-OCO-Long



Triglyceride of Carboxylic acid biological origin methyl ester

Triglyceride of modified structure

Fatty acid methyl ester



13.1

Molar mass, viscosity and pour point of the original triglyceride decreases, without production of glycerol. The reaction product of the TBK-biodiesel process, in which triglycerides are interesterified with ethyl acetate, resulting in a mixture of fatty acid ethyl esters and partially modified triglycerides (containing both original C 16-C22 and introduced C 2 acyl groups), is characterised by low viscosity (5–6 cSt), 15–20% more biofuel from a unit of vegetable oil than in the case of biodiesel, lowered IV, no wastes, no glycerol and no sewage. The reaction product is proposed as a new fuel. Global consumption of glycerol is roughly equally divided among the US, Europe and the rest of the world (see Table 13.3) and is stable in the absence of alternative market opportunities. Glycerol prices fluctuate widely, depending on supply and demand factors. Once glycerol was sold at high prices for various purposes, but only when of high purity. The glycerol Table 13.3 Estimated end uses (%) of glycerol (adapted from ref. [10]) Use field

Use (%)



USA Europe Japan (230 kt/yr)a (275 kt/yr)a (50 kt/yr)a

China Globalb (80 kt/yr)a

39.5 15.8 ND 14.5

23.1 2.5 14.4 5.6

34.0 5.3 ND ND

5.2 7.3 ND ND

20 6 10 10

10.5 9.2 2.0 0.6 ND ND 7.9

13.1 13.1 4.4 3.1 ND ND 20.6

11.6 19.5 3.8 1.9 ND ND 23.9

5.2 49.0 1.5 3.1 16.0 6.3 7.2

12 11 2 2 14

Pharmaceuticals Tobacco Glycerin triacetate Food/beverages, incl.   emulsifiers Polyether alcohol Alkyd resins Cellophane Explosives Toothpaste Cosmetics/personal care Miscellaneousc a

1998 data. 2001 data. c Some 1500 applications. ND = no data. b

13

Valorisation of the glycerol by-product

583

market was tight in the early 1990s. Historically, high prices of US$1.10/lb in 1995 were due to a worldwide shortage of glycerol estimated at roughly 50 kt on a total market of about 610 kt/yr. Although glycerol prices were then expected to remain high because of continued increases in demand, to be satisfied by projected expansions of existing facilities [26], Fig. 13.5 shows the considerable impact of biodiesel production on (97%+purity) glycerol prices (US$1000/t = US$0.50/lb), down to US$0.50/lb in 2003. In fact, the present rate of worldwide biodiesel production causes an increasing mismatch in supply and a drop in glycerol value. South-East Asia and Europe are exporting glycerin to the US in large volumes at low prices. Glycerin prices depend totally on how much biodiesel production continues in SouthEast Asia, Europe, the US and Argentina. At present, the glycerin market is experiencing reduced demand from Asia. Glycerol availability has now resulted in very low product value. As the demand for and production of biodiesel increases, the value of the by-product glycerol will fall dramatically unless new glycerol utilisation approaches are developed. Already in December 2003, a large German biodiesel producer (Nevest, Schwarzheide) filed for insolvency, partly because of the sharp decline in the price of glycerol to far below 71000/t. Raw glycerine prices (2004) of about US$0.15/lb and below were reached [27]. US$ pricing (May 2007) for tallow, vegetable and pharmaceutical grade glycerine were still of 2500

Refined price ($/MT)

2000

1500

1000

500

0 1995

1996 1997 1998

1999 Year

2000 2001

2002

2003

13.5 Impact of biodiesel production on glycerol prices (after ref. [28]).

584

Biodiesel science and technology

the order of US$683–816/MT, US$750–904/MT and US$1058–1278/MT, respectively (ICIS pricing). Glycerol pricing is likely to be sustained as long as biodiesel plants operate far below capacity due to high vegetable oil prices. Yet, in a highly volatile glycerol market, further reduction of the chemical value of refined glycerol to US$0.35/lb by 2010 could be expected. At particularly low refined glycerol prices (< US$300/t) crude glycerol becomes competitive for animal feed use and as a carbon source in fermentation broths as a substitute for carbohydrates. The agricultural sector can utilise large volumes of glycerol of varying qualities in several areas. These uses include feed, fertiliser and alternative application opportunities, such as dust and ice control. Uses of low-grade glycerol include mixing with animal manure to form a fertiliser, and mixing with feed for animals [29]. Animal feed applications are an opportunity for direct use of crude glycerol without the need for further refining. Technical glycerols from biodiesel production have been evaluated as a feed component in fattening of pigs [30]. Crude glycerin (85% glycerol, 10% water, 5% salts) is a viable energy-creating animal feed (for swine and poultry), comparable to corn [31]. Obviously, market prices determine farmers’ preference. A liquid by-product (containing 58–68% glycerol, 14–24% water, 10–16% residual oil and 3–8% methanol) from FAME production from RSO was utilised as the starting material for the preparation of a feed energy supplement for ruminants to provide an outlet for further use of the by-product [32].

13.5

Innovative use of glycerol

Innovative use of glycerol is of strategic interest to the oleochemical industry. It is imperative that new applications are indeed innovative, rather than substitutions resulting in competition to (lower-priced) petrochemicals. Highvolume conversions into valuable chemicals are most desirable. Long-term, the crude glycerol by-product from the transesterification process should serve as a very useful platform substrate to use as a building block in developing higher-value products. New bulk uses must be identified for a consumption estimated at about 1 Mt/yr of glycerol. Bondioli [33] has addressed the problem of glycerol production in terms of both economic significance and new outlets for surplus production. In recent years various new opportunities for the conversion of glycerol into value-added chemicals have emerged [2, 34]. Highly purified glycerol is an ideal feedstock for catalytic conversion processes. The problem with crude biodiesel glycerol is its contamination with salts and ashes, which poison chemocatalysts and affect their stability. The challenge here is in devising chemocatalysts which are stable in aqueous medium at relatively high T, p. R&D efforts are seeking new catalysts and processing methods that will provide economical markets for the extra glycerol production. Reaction

Valorisation of the glycerol by-product

585

pathways have been described for the catalytic conversion of glycerol into commodity chemicals, including selective oxidation, hydrogenolysis and dehydration, pyrolysis and gasification, steam reforming, thermal reduction into syngas, selective (trans)esterification and etherification, oligomerisation and polymerisation, chlorination and carboxylation (Table 13.4). While much research has concentrated on the oxidation and (trans)esterification of glycerol to more valuable products, less attention has been paid to novel processes such as carboxylation of glycerol. The glycerol phase from the biodiesel cycle is a potential feedstock for both material and energy production [7]. Several outlets for glycerol are listed in Table 13.5. Potentially high-volume applications of derivatives of glycerol are methanol and 1,3-propanediol for preparation of linear polymers and as an EG substitute. Development programmes using commercially proven catalysts are aimed at propylene glycol, polyglycerols, glycerol ethers and esters, and dichloropropanol (epichlorohydrin). Glycerol and polyglycerols may be used as substitutes for ethylene oxide and polyoxyethylene. Some other promising innovative applications of glycerol are replacement for synthetic polyols (e.g. ethoxylates, surfactants), production of glycerol carbonate and glycidol (intermediate for cosmetics and pharma industries), production of fine chemicals, synthesis of conjugated linoleic acid (a desirable nutraceutical), and Table 13.4 Catalytic conversion processes of glycerol Process

Productsa

• • • • • • • • •

DHA, GLYAC, GLYALD, HYPAC, MESAC, TARAC, etc. 1,2-PD, 1,3-PD, EG, ROH (R=C1-C3) Acetol, ACR, PGs CnH2n+2, CnH2n, ROH, CO/H2, C/H2 MG, DG, TG Mono-, di- and tri-ethers PGs, PGEs ECH Glycerol carbonate, Glycidol

a

Oxidation Hydrogenolysis Dehydration Pyrolysis/gasification (Trans)esterification Etherification Oligo/polymerisation Chlorination Carboxylation

For abbreviations, see Appendix II. Table 13.5 Some potential outlets for glycerol ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Glycerol alkyl ethers (e.g. GTBE), for use as additives in diesel fuels Glycerol alkenyl ethers (conversion of glycerol with dienes) Glycerol telomers (feedstock for detergent production) Short-chained glycerol oligomers Glycerol polymers (hydrophilic hydroxypolyethers) Short-chained glycerol-based carboxylic acids 1,2-PD, 1,3-PD, acrolein Glycerol-to-methanol

586

Biodiesel science and technology

epoxidation (plasticisers). The most promising and economically viable use for crude glycerol might be, however, conversion into mono- and di-fatty acid esters [35]. Among the various glycerol derivatives (acetals, ketals, amines, esters, ethers, chlorohydrins) the esters are most widely employed. Important new bulk outlets for glycerol are 1,2-propanediol, glycerol polyethers and epichlorohydrin. As the price of glycerol decreases, new products, especially polymers, will be increasingly derived from glycerol (e.g. polyhydroxy compounds). While Biobode, Ltd. (Edgeworthstown, Ireland) is developing commodity plastics containing 20–38% glycerin [36], Vertellus Specialties (Indianapolis, IN) is developing specialty chemicals from glycerol in cooperation with UK’s Cardiff University. Conversion of glycerol to fuel products is also expected to grow. The use of glycerol-based additives to improve petrol fuel properties (antiknock, octane number) is one of the possibilities currently being explored to utilise this renewable feedstock [37, 38]. Using glycerol to produce fuel additives, e.g. tert-butyl esters of glycerol and acetylated glycerol derivatives as diesel fuel or gasoline additives, could develop into an important market for biomass resources. Dibutoxyglycerol (DBG) has also been evaluated as a diesel fuel blend component [39]. Converting glycerol into H2 or syngas by steam reforming is very promising. Aqueous glycerol solutions may also be used for liquid alkane production by carbohydrate reforming. Catalytic transformation of glycerol has been reviewed [34, 40]. Where large amounts of by-products are produced, as in the case of glycerol in manufacturing of biodiesel through transesterification of vegetable oils, catalytic upgrading into chemical products could make an important contribution to improving the overall process economy. Economic forecasts have indicated that the net production costs of B100 type biodiesel can be reduced from US$0.63/L to US$0.35/L by adding value to the glycerol byproduct [41].

13.5.1 Selective oxidation of glycerol Since glycerol (GL) is a highly functionalised molecule compared to hydrocarbons from petrochemistry, it is an advantageous feedstock for the production of valuable oxygenates such as the C3 derivatives dihydroxyacetone (DHA), glyceric acid (GLYAC), glyceraldehyde (GLYALD), hydroxypyruvic acid (HYPAC), mesooxalic acid (MESAC) and tartronic acid (TARAC), as well as similar C2 and C1 products [34]. Other chemicals that could be derived economically from low-cost glycerol include citric acid. Some are niche applications only, quite insufficient to absorb the current surplus glycerol production volumes. The fine chemicals DHA and HYPAC are usually obtained by low productivity fermentation processes, and GLYAC by potentially polluting oxidation processes using mineral acids [42]. Gallezot

Valorisation of the glycerol by-product

587

et al. [43] have proposed selective oxidation of aqueous glycerol solutions, obtaining high selectivity to GLYAC (77% at 90% conversion), but only 37% yield in DHA at 70% conversion. �� ��

��



� ��

� ��

��

�� � ��

��

��

� ��

��

��

�����

�

�

�

� ��

��

��

���

� ��

�

�����

�

��

�

� �

��

13.2

Industrialisation of these products requires the design of effective chemoselective catalytic oxidation catalysts. For oxidation of glycerol it is important to use macroporous catalysts to overcome any diffusion-related problems, which result in products of non-selective oxidation. In most cases, good selectivity to the desired products at high glycerol conversion is still difficult because of the extensive functionalisation of the triol glycerol molecule with hydroxyl groups of similar reactivity, and because of a lack of optimal catalysts or unknown reaction conditions.

13.5.2 Glycerol hydrogenolysis Catalytic hydrogenolysis of glycerol is an alternative route to increase the profitability of biodiesel manufacturing as the reaction products can easily replace high-volume chemicals which are currently being produced industrially using non-renewable sources. Through selective reduction of glycerol in the presence of metallic catalysts and hydrogen, methanol, 1,2-propanediol (1,2PD), 1,3-propanediol (1,3-PD), and ethylene glycol (EG) can be obtained. BioMethanol Chemie Nederland/BioMCN (Delfzijl, The Netherlands), now Waterland Invests, has developed an innovative catalytic process that converts crude glycerine (after upgrading to pharmaceutical grade) into biomethanol. The feedstock is first cracked to obtain syngas, which is then reformed to methanol (see Fig. 13.6). Methanol is commonly produced industrially from fossil fuel via the syngas reaction. The feasibility of the crude glycerine-tomethanol process was demonstrated in a pilot plant in March 2008; a first 200 kt/yr commercial unit will come on stream in 2009 and production is expected to grow to 1 Mt/yr by 2010 (http://www.biomcn.com). The process

588

Biodiesel science and technology

Steam reforming

CO/H2 Syngas Reforming

CPO Natural gas

C3H5(OH)3 Glycerol

Cu/ZnO/Al2O3 523 K 8 MPa

H2 PMG

373 K 2 MPa

CH3OH Methanol

13.6 Alternative methanol production schemes.

allows biodiesel production to become even more sustainable and avoids the potential problems with disposal of surplus glycerol. We can readily envisage a time when syngas obtained in high yield from glycerol will be used to synthesise both methanol and fuels by the Fischer–Tropsch and MtS processes. In a further advancement, a recent invention, subject to a pending patent application [44] and to be commercialised by Isis Innovation (University of Oxford’s technology transfer company), allows glycerine (from biodiesel) to be converted directly and cleanly to (almost) green methanol by selective hydrogenolysis using a new supported precious metal catalyst in mild reaction conditions (373 K, 2 MPa) (see Fig. 13.6). In the conditions of direct catalytic hydrogenolysis of glycerol to methanol C—C bonds are broken without cleaving C—O bonds, thereby avoiding the production of gases such as CO2 and CH4. The technology saves on processing steps and requires lower energy costs. In nature, microorganisms produce methanol from biomass through fermentation, but the process is too slow for industrial scale production. Also the ‘Supermethanol’ project envisages a one-step conversion of crude glycerine to methanol (GtM). In PCT Int. Publ. No. WO 2008/144448, Hulteberg et al. [45], to Primafuel, Inc., disclose a gas phase process for a monoalcohol production from aqueous glycerol. The process consists in a first reaction step at 523–613 K at 0.05–1 MPa over a dehydration catalyst (e.g. WO3/ZrO2) in combination with a platinum group metals (PGM) hydrogenation catalyst to yield an intermediate dehydrated-glycerol mixture, mainly composed of acrolein and propionaldehyde, which is then further hydrogenated to monohydric alcohols (C1 to C3), with at least 70 wt% n-PrOH. The process for converting glycerol to propyl alcohol formally proceeds as follows:

Valorisation of the glycerol by-product

H2C HO

CH H2C

OH –2H2O Catalyst

OH

Glycerol

H2 Catalyst

H C

O C H

Acrolein

CH2

H2 Catalyst

589

H2 C

O C H

CH3

Propionaldehyde

H2 C

HO C H2

CH3

13.3

1-Propanol Depending on the reaction conditions, other intermediates can be produced, including glycols, or the three-carbon chain of glycerol can be cleaved, leading to a mixture of lower aldehydes and alcohols. Other development programmes using commercially proven catalysts are aimed at propylene glycol (PG) production from glycerol [6]. Such developments for the co-product glycerol enable biodiesel and fatty acid producers to improve the economics of the overall oleochemicals scheme and provide a lower-cost propylene glycol at a time of high propylene prices. Propylene glycol (i.e. 1,2-PD) is a medium-value commodity chemical currently almost exclusively derived from the non-renewable resource propylene oxide (annual production > 1 Mt/yr) with a broad spectrum of applications [46, 47]. Some typical uses of 1,2-PD are in unsaturated polyester resins, functional fluids (antifreeze, deicing, and heat transfer), foods, cosmetics, pharmaceuticals, liquid detergents, tobacco humectants, flavours and fragrances, personal care, paints and animal feed. The antifreeze and deicing market is in rapid expansion because of concern over the toxicity of ethylene glycol-based products to humans and animals. 1,3-Propanediol (1,3-PD) has traditionally been considered a high-value (75000/t, 2005) specialty chemical with numerous applications in polyester fibres, films and coatings, and other organic chemicals, but with small markets. However, more recently this situation has changed significantly. An emerging large-volume application of 1,3-PD is as a monomer for poly(propylene terephthalate) (PPT) [48], used in carpeting (Corterra®, Shell) and special textile fibres (Sorona®, DuPont). As production of PPT increases, 1,3-PD is expected to become a new commodity chemical. Current industrial chemical techniques for 1,3-PD production are based on the catalytic conversion of the petroleum derivatives ethylene oxide (by hydroformylation; Shell-DuPont route) [49, 50] and acrolein (by hydration/hydrogenation; Degussa route) [51]. The acrolein route shows low conversion efficiency. Ethylene glycol, now mainly derived from ethylene, is a raw material for synthetic fibres and explosives.

590

Biodiesel science and technology

While commercial production of 1,2-PD is by hydrolysis of propylene oxide, there are several alternative routes to 1,2-PD from renewable feedstocks, such as catalytic hydrogenolysis at high T, p of aldoses (e.g. glucose, xylose) and alditols (e.g. glycerol, sorbitol) [52, 53]. Although catalytic hydrogenolysis has been known for over 70 years, none of these processes has been commercialised, primarily due to the large number of co-products, the relatively low selectivity to ethylene and propylene glycols (EG and PG) and catalyst degradation. Theoretical pathways for catalytic hydrogenolysis of glycerol are indicated in Fig. 13.7. Unlike glycerol-to-methanol, catalytic hydrogenation of glycerol to propanediols and ethylene glycols requires a degree of C—O bond cleavage accompanied by the addition of hydrogen under relatively harsh conditions. Hydrogenolysis of aqueous solutions of glycerol in the presence of supported metal catalysts has generally resulted in 1,2-PD/1,3-PD mixtures. In order to obtain optimum selectivity values, usually very complex conditions and catalytic systems are needed. In general, the conversion process of crude glycerol to PG involves the use of a metal catalyst, high T, p, dilute solutions, and the addition of (an external source of) hydrogen. The challenge is therefore to develop catalysts and technologies that allow the reaction to occur in milder reaction conditions at higher yields. Selectivity for 1,2-PD relative to EG and degradation products can be enhanced if the catalyst is active for dehydration. In 1985, Celanese patented the catalytic hydrogenolysis of aqueous glycerol under 30 MPa of syngas at 473 K in the presence of a homogeneous rhodium complex to low yields of the propanediol isomer mixture [54]. In US Patent H2C

CH2

HO

HO

H2 C

CH

H2 C

OH

HO

H2 C

OH

+ CH3OH

OH

Ethylene glycol

CH

CH3

OH

H3C

1,2-Propanediol

CH3

CH OH 2-Propanol

HO

H2 C

C H2

H2 C

1,3-Propanediol

OH

HO

H2 C

C H2

1-Propanol

CH3

H3C

C H2 Propane

13.7 Pathways for catalytic hydrogenolysis of glycerol.

CH3

Valorisation of the glycerol by-product

591

No. 5,426,249 to Haas et al. [55], Degussa discloses a heterogeneously catalysed manufacturing process for the co-production of 1,2-PD and 1,3-PD from crude aqueous (10–25%) glycerol (from fat cleavage) in high yield, wherein the first step is dehydration of glycerol. Later, Shell developed a homogeneous palladium complex for the co-production of 1-propanol, 1,2PD and 1,3-PD (in 47 : 22 : 31 ratio) in moderate T, p conditions [56]. More recently, Schlaf et al. [57] described dehydroxylation of glycerol catalysed by a homogeneous ruthenium complex to 1,2-PD and 1,3-PD in very low yields (<5%). Hydrogenolysis of glycerol over a Ni/Re catalyst at 503 K under 8.2 MPa H2 leads to 44% 1,2-PD, 5% 1,3-PD and 13% EG (carbon molar selectivity) after 4 h [58]. Hydrogenolysis of glycerol has also been conducted on Ru/C catalysts in the presence of Amberlyst resin, yielding mainly 1,2-PD [59]. According to Montassier et al. [60, 61] hydrogenolysis of glycerol under 30 MPa H2 at 533 K in the presence of Raney copper leads to 1,2-PD as the main reaction product. Copper catalysis appears to be essential. Treatment of liquid-phase glycerol under hydrogen in the presence of copper-chromiumbased catalysts also yielded only 1,2-PD [62]. US Patent No. 5,616,817 to Schuster and Eggersdorfer (to BASF) [63] discloses a process for the preparation of the 1,2-PD isomer by heterogeneous catalytic hydrogenation of highly concentrated (>80%) glycerol at elevated T, p using a (Co, Cu, Mn, Mo) catalyst. In another study 100% selectivity to 1,2-PD was obtained with only 20% conversion after 168 h by hydrogenolysis of aqueous glycerol at 453 K and 8 MPa H2 over CuO/ZnO catalysts [64]. Suppes et al. [6, 65–67] have recently developed a low-cost liquid-phase hydrogenolysis process to convert both refined and crude glycerol (1,2,3propanetriol) into high-purity propylene glycol (1,2-propanediol). Using a CuO•Cr2O3 catalyst in mild hydrogenation conditions (473 K, 1.37 MPa), high selectivity towards propylene glycol (> 73% yield) and little or no selectivity towards ethylene glycol or other by-products was achieved. Figure 13.8 shows the proposed reaction mechanism. In a two-step process, glycerol is first dehydrated to form the intermediate acetol or 1-hydroxy-2-propanone (at a cost of about US$0.50/lb), which is then hydrogenated at low pressure to form propylene glycol (valued at US$0.71/lb [68]). The technology qualified OH H H 2C

O

C

CH2

O

H

OH O

H Dehydration – H2O

H2C

C

Glycerol Acetol

OH OH CH3

Hydrogenation + H2

H2C

C H

CH3

Propylene glycol

13.8 Proposed reaction mechanism for conversion of glycerol to propylene glycol (after ref. [65]).

592

Biodiesel science and technology

for the 2006 AOCS Glycerin Innovation award and the 2006 Presidential Green Chemistry Challenge award. Inexpensive propylene glycol (or a 70% PG/30% GL mixture) can be used as a low-toxicity replacement for ethylene glycol in automotive antifreeze. This outlet is expected to have a major impact on the future of biodiesel fuel (lowering costs by some US$0.40/ gal), the world glycerol market, and the environmental health and safety of antifreeze and deicing chemicals. A first commercial facility (11.5 Mgy) in Atlanta, GA, to be built by Senergy Chemical Holdings LLC (Gig Harbor, WA) and licensed through Missouri Soybean Merchandising Council, is based on the patented process [69, 70]. Recently, Davy Process Technology, Ltd (DPT) has developed a robust homogeneous catalyst system (based on a precious metal and organic phosphine ligand) for economic conversion of glycerol by highly efficient vapour-phase hydrogenolysis to ethylene and propylene glycols under mild reaction conditions [71, 72], which represents a significant advance on previous homogeneous systems. The DPT results (with high PG yields) compare favourably with those reported in the literature (Table 13.6). Even more promising is the use of reduced heterogeneous copper catalysts in vapour-phase hydrogenation at 478–493 K and 2 MPa with high 1,2-PD conversions (> 95%) [73]. Biodiesel waste glycerol can also be converted into 1,2-PD via catalytic in-situ hydrogenation of hydroxyacetone [74]. OH HO

O

CH C H2

OH C H2

C

–H2O Catalyst, H

+

Glycerol

H3C

OH C H2

Hydroxyacetone

OH +H2 Pt



CH H3C

OH

13.4

C H2 1,2 - PD



Table 13.6 Catalytic hydrogenolysis of glycerol Catalyst

Added Temp. (K) Pressure Tons/ton feed Reference base (MPa) —————————— EG PG Total

DPTa None 523 Ni+Re/C+NaOH NaOH 503 7%Ni/1%Re/C NaOH 503 a

Davy Process Technology, Ltd.

6.7 8.9 8.9

0.07 0.09 0.07

0.717 0.787 0.55 0.64 0.66 0.73

[72] US 6,479,713 US 6,479,713

Valorisation of the glycerol by-product

593

Many other academic and industrial efforts are directed towards biobased forms of PG and EG produced from vegetable oil-derived glycerol. The Cargill/Ashland joint venture intends commercialising a high-purity grade of renewable PG from European biodiesel glycerol by mid-2008 using Davy’s hydrogenation technology in a 65 kt/yr plant. ADM is developing a glycerin refinery in Illinois that will be part of a glycerin-to-propylene glycol facility in 2009. The world’s largest manufacturer and marketer of PG from propylene oxide (Dow) is already producing limited commercial quantities of propylene glycol renewable (PGR) from biodiesel glycerol in a Houston, TX, plant using a proprietary process. US specialty chemicals firm Huntsman Corp. is scaling up its own process to convert glycerol into propylene glycol for production in 2008. Propylene glycol production is also the focus of Virent Energy Systems, Inc. (Madison, WI) development activities. This approach to produce PG from glycerol is based on its patented BioForming™ process, in which a liquid stream of a water-soluble carbon source such as glycerol is fed into a solid-state catalyst system. Through a process called aqueous-phase reforming, this liquid stream is converted into various high-value chemicals (liquid and gaseous fuels, including hydrogen). Virent’s completely renewable PG is based on in situ generated hydrogen. Depending on the biodiesel process, the glycerol that is used may require pre-treatment before being fed to the BioForming™ process. Virent is designing a glycerin-to-propylene glycol pilot plant which is associated with a biodiesel production facility in Arkansas. Virent Energy Systems, Inc. received the 2008 Red Herring North America Award for advanced technology and EPA’s Presidential green chemistry small business award. Bio-based 1,3-propanediol is being considered for production from crops, because it is relatively expensive to make by chemical routes. Propylene glycols can be produced by alternative routes involving selective dehydroxylation or microbial conversion of renewable feedstocks (e.g. glycerol and sugars). (see Section 13.5.9). A DuPont/Tate & Lyle joint venture produces 45 kt/yr 1,3-PD from corn at Tate & Lyle’s processing site at Loudun, TN, for the production of DuPont’s Sorona polymer fibre [75]. The Loudun facility is the world’s first 1,3-PD unit based on renewable resources. Microbial production of 1,3-PD from glucose is under development by DuPont-Genencor [76]. Routes to 1,3-PD have also been developed from vegetable oils and animal fats, but none has yet been brought to commercial scale. The yields of 1,3-PD are usually low when using raw glycerol from biodiesel production. Wang et al. [77] have recently converted glycerol to 1,3-PD in 70% yield.

13.5.3 Catalytic dehydration of glycerol Two important chemicals can be derived by dehydration of glycerol, namely 3-hydroxypropionaldehyde (3-HPA) and acrolein. 3-HPA is of considerable

594

Biodiesel science and technology

industrial interest as an intermediate, since it is easily converted to a number of large-scale commodity chemicals, including acrolein and 1,3-propanediol (see Fig. 13.9), 3-hydroxypropionic acid, acrylic acid, malonic acid and acrylamide. 3-HPA can be produced efficiently from renewable aqueous glycerol in a onestep enzymatic reaction using glycerol dehydratase. Commercial biochemical production (Danisco Deutschland) is expected soon. A sustainable and cost-effective acid dehydration of low-cost glycerol to acrolein offers an alternative for the commercial petrochemical oxidation process based on propylene. While a process for the production of acrolein from glycerol was already described in Fr. Patent No. 695,931 to ScheringKahlbaum AG [78], this product can also be obtained from very dilute glycerol [79]. Double dehydration of glycerol to acrolein (Fig. 13.9) is very significant over acid sites. For catalytic dehydration of glycerol to acrolein, mineral acids or their salts are used as catalysts in homogeneous catalytic processes. These homogeneous catalytic processes still cause severe pollution and corrosion, leading to high production costs. Dehydration of glycerol is an energy consuming process. New solid-acid catalysts stable under the reaction conditions are under development by Arkema (Colomes, France). Several patents cover the gas phase dehydration of glycerol [55, 80]. Solid-acid catalysts (i.e. Amberlyst® ion-exchange resins) can catalyse the dehydration of glycerol. Sub- and supercritical water (SCW) reactions can also be used for the production of acrolein from glycerol [81, 82]. Addition of acids allows substantially lower dehydration temperatures. Polyglycerols are also obtained by dehydration of glycerol (see Fig. 13.17). A fair compromise between activity and selectivity has been obtained by Clacens et al. [83] using Cs-impregnated mesoporous MCM-41.

13.5.4 Pyrolysis and gasification The pyrolysis process yields liquid fuels at low temperatures (673–873 K) and gaseous products at high temperatures (> 1023 K). Gasification is a process conducted in the presence of oxygen, in the form of air or steam.

C3H8O3 Æ 3CO + 4H2



C3H8O3 + 3H2O Æ 3CO2 + 7H2 (ΔH°298 K = + 346.4 kJ/mol)



13.5 13.6

Glycerol can be converted to syngas at high rates and selectivities at 498–620 K according to Eqn 13.5 [84]. Carefully calibrated amounts of oxygen can be used to partially oxidise glycerin into syngas. The Florida Syngas LLC (Grant, FL) high-temperature reforming process requires partially refined crude glycerin because salts will degrade the unit’s catalyst. Operation of gasification at

OH HO

CH C H2

C H2

OH

–H2O Glycerol dehydratase

HO

H C C H

C H2

OH

H2 C

O C H

C H2

OH

+H2O

H2C

H C

O C H

Acrolein

1,3-Propanediol oxidoreductase

HO

C H2

H2 C

C H2

OH

1,3-Propanediol

13.9 Schematic reaction path for catalytic dehydration of glycerol to 3-HPA and acrolein, and formation of 1,3propanediol (after ref. [83]).

Valorisation of the glycerol by-product

3-HPA

Glycerol

–H2O

595

596

Biodiesel science and technology

low temperature provides the opportunity to couple the endothermic glycerol conversion with exothermic Fischer–Tropsch synthesis to produce liquid transportation fuels through the following integrated process [84]:

C 3H 8 O 3 Æ 7 C8 H18 + 19 CO 2 + 37 H 2 O 25 25 25

13.7

Liquid alkanes have advantages over other biofuels, such as ethanol, for use as transportation fuels because they can be used in existing engines and distributed by infrastructure already in place. Producing liquid alkanes from renewable biomass resources is also an attractive processing option because its use produces less CO2, and thus impacts less on global warming. Liquid alkanes can be produced directly from concentrated glycerol feed solutions by an integrated two-bed reactor process involving catalytic conversion to synthesis gas (H2/CO between 1.0 and 1.6) at low temperatures (548 K) and high pressures (0.1–1.7 MPa) over a 10 wt% Pt-Re/C catalyst (atomic ratio Pt/Re = 1 : 1) combined with ‘green’ Fischer–Tropsch synthesis (using biomass) at 548 K and 0.5 MPa over a Ru/TiO2 catalyst [85], schematically as follows:

Pt Re F-T Glycerol/water æ æ Æ H 2 /CO æ Æ Liquid alkanes

13.8

The syngas produced in the first process can be fed directly into the second process without purification. The coupled process avoids the highly endothermic and exothermic steps that would result from the separate operation of the processes and eliminates the need to condense water and oxygenated hydrocarbon by-products between the catalyst beds. By-products are methanol and ethanol, both useful in their own right. Figure 13.10 shows a process schematic which illustrates the potential end-use of the various product phases obtainable from aqueous-glycerol conversion. The gaseous product stream consisting of light alkanes can be combusted to produce electricity and heat while the oxygenated hydrocarbons in the aqueous phase effluent can be separated by distillation for use in the chemical industry. The oil phase containing liquid alkanes can be upgraded to gasoline and diesel fuel. Long-chain alkanes comprise the vast majority of components in transportation fuels from petroleum (branched for gasoline and linear for diesel). The production of renewable alkanes from biomassderived carbohydrates through aqueous-phase carbohydrate reforming (ACR) confirms the technology as a new pathway to the production of liquid fuels [86–89]. Virent’s BioForming™ platform, based on the ACR pathway (Fig. 13.11), converts carbohydrates from biomass into gasoline, diesel and jet fuel, and is an attractive alternative for fermentation processes. Conversion of glycerol into traffic fuels was reviewed in ref. [90]. The production of hydrogen for fuel cell and other industrial applications

Vegetable oils and animal fats

Biodiesel

Transesterification ACR

Aqueous glycerol (25–85 wt%)

Distillation

Light alcohols and polyols

H2/CO Reforming

Aqueous solution of oxygenated hydrocarbons (acetone, methanol, ethanol)

Selective dehydration/ hydrogenation

ACR

Fuels

Integrated glycerol conversion with Fischer-Tropsch synthesis

Gaseous alkanes

Liquid hydrocarbons

Electricity and heat

Combustion

Upgrading Naphtha, Diesel fuel, Kerosene

H2

13.10 Process pathway for production of various product phases from aqueous glycerol (ACR = aqueous-phase carbohydrate reforming).

Valorisation of the glycerol by-product

Chemicals and solvents

H2

597

598

Biodiesel science and technology HO

OH CH

+ H 2O

CH

CO2, H2

reforming

H2

H Dehydrogenation/ rearrangement

H2

Methanation, Fischer-Tropsch reactions

H2 H

H2O

CH

Dehydration/ hydrogenation

OH C O

H CH

OH reforming

CH

+H O 2

CH4, Alkanes, H2, CO2, H2O

H

13.11 Schematic representation of reaction pathways for aqueous phase reforming of oxygenated compounds in which each carbon atom is bonded to an oxygen atom. Selectivity for production of H2 is compromised by pathways leading to the formation of methane and heavier alkanes (after ref. [91]).

from renewable biomass-derived resources is a major challenge. The use of residual glycerol as a hydrogen source has recently been studied extensively by catalytic reforming, photocatalytic processing and microbial conversion [4, 40, 89–97]. Glycerol is potentially a useful feedstock for hydrogen production because one mol of glycerol can produce up to four mols of hydrogen (Eqn 13.5). In this regard, reforming of glycerol is a suitable reaction (Eqn 13.6). Cost-effective aqueous-phase carbohydrate reforming using a variety of inexpensive catalysts allows generation of hydrogen in high yields from low-value raw glycerol streams [92]. The extracted raw glycerol waste of biodiesel production is soluble in water. The (endothermic) one-step reforming process of an aqueous solution of raw glycerol to hydrogen takes place over a catalyst in a single ACR reactor at low temperature (473–523 K) and moderate pressure (1.6–4.0 MPa). Aqueous-phase reforming (APR) reactions occur at substantially lower temperatures than conventional alkane steam reforming (typically 923 K) [90]. In APR reaction conditions, decomposition reactions, which take place when carbohydrates are heated to elevated temperatures, are minimised. Moreover, the fact that in the APR process there is no need to volatilise water represents a major energy saving compared to conventional vapour-phase steam reforming processes. However, the primary economic driver for the APR process is the feedstock.

Valorisation of the glycerol by-product

599

The conversion of oxygenated hydrocarbons in the presence of water to H2 and CO2 is highly favourable at low temperatures [91]. Nevertheless, selectivity challenges must be overcome to generate hydrogen from glycerol, since the subsequent reaction of H2 and CO2 to form alkanes and water is also highly favourable at low temperatures. A variety of catalyst compositions are active for the selective (in-situ) generation of hydrogen via APR of oxygenated compounds (such as ethylene glycol, glycerol, sorbitol and glucose) [91, 98]. Effective catalysts should be active for C—C, O—H and C—H bond cleavage in glycerol and for water–gas shift of CO to CO2 to remove adsorbed CO from the surface. The catalyst must not perform subsequent methanation and/ or Fischer–Tropsch synthesis reactions to produce alkanes, which consume hydrogen and decrease the hydrogen selectivity. Using Raney-NiSn catalysts at 498 K for the aqueous-phase reforming of glycerol produces a gas stream composed of 66 mol% H2, 30 mol% CO2 and 4.2 mol% methane (dry basis). The selectivity for H2 production over Pt-based catalysts is lower for APR of glycerol compared to ethylene glycol [92]. Although the aqueous-phase reaction has the advantage of low catalyst deactivation, high pressure and slow reaction rates hinder commercialisation. While having an adverse impact on suppliers of glycerol, the increased co-production of glycerol anticipates a price which could make hydrogen generation by the APR process very attractive. Virent Energy Systems, Inc. (Madison, WI) is further developing the APR process for generating hydrogen from aqueous solutions of glycerol streams from biodiesel plants [92]. The non-condensable gas stream leaving the APR contains predominantly CO2 and H2. Hydrogen can easily be purified from this gas stream utilising pressure swing adsorption (PSA) technology. The simple, one-step process in conditions of favourable water–gas shift generates H2 with low amounts of CO, which can be utilised as a renewable chemical reagent to produce ammonia, methanol and hydrogenated food oils, as well as a fuel for current internal combustion engines and future hydrogen fuel cells. Virent’s GEM™ (Green Energy Machine) integrates an aqueous-phase carbohydrate reforming system with a hydrogen/natural gas fuelled internal combustion engine (ICE). Figure 13.12 shows the schematic of GEM™ using the process.

ACR

H2 Alkanes CO2

e– ICE

Aqueous glycerol Heat

13.12 Schematic of GEM

TM

(Green Energy Machine).

CO2 H2O, heat

600

Biodiesel science and technology

Catalytic conversion to methanol by the reaction

2CO2 + 6H2 Æ 2CH3OH + 2H2O

13.9

provides a starting reactant for biodiesel production, thus reducing the material cost (Fig. 13.13). Unlike current methods (i.e. steam reforming) for producing hydrogen from non-renewable petroleum feedstocks [99], the selective production of hydrogen by ACR of renewable biomass resources does not increase the levels of atmospheric CO2, because this greenhouse gas is recycled when consumed during further production of biomass. Unlike aqueous-phase reforming, steam reforming must ideally be carried out at high temperature, low (atmospheric) pressure and high steam-to-glycerol ratio to achieve high conversions. Steam reforming of glycerol is an active field of research [100–102]. Hirai et al. [101] developed an efficient 3 wt% Ru/Y2O3 catalyst for glycerol steam reforming in the gas phase which is resistant to deactivation caused by carbon deposition. Glycerol is also easily and completely gasified to a hydrogen-rich gas in supercritical water without a catalyst after 44 sec. at 873 K and 34.5 MPa [103]. Hydrogen production from glycerol-containing wastes discharged after biodiesel manufacturing was also studied using Enterobacter aerogenes HU101 [96]. Dihydrogen formation from aqueous glycerol can be affected by polyoxometalate photocatalysts [97]. Also pure biodiesel makes an excellent high-density source that can be easily reformed into hydrogen for fuel cell applications.

13.5.5 Selective glycerol transesterification and esterification The production of glycerol esters is a main outlet for glycerol. Monoglycerides (MG) and polyglycerol esters (PGE) with a hydrophilic head and hydrophobic tail exhibit detergent characteristics. It is of interest to convert glycerol into ester or ether derivatives that can be used as biogradable surfactants [104]. Monoglycerides may be obtained by: hydrolysis of triglycerides, glycerolysis of triglycerides or direct esterification of glycerol with fatty acids. However,

VO + MeOH

catalyst

FAME (biodiesel) + GL H2O

e– ACR Ni cat.

CO2 + H2

NH3 Hydrogenation

Cu/ZnO/Al2O3

13.13 Production of hydrogen from raw glycerol and conversion of the non-condensable gas stream to methanol.

Valorisation of the glycerol by-product

601

as the reactivity of the three hydroxyl groups in glycerol is rather similar, usually mixtures of MGs, DGs and TGs are formed. It is a challenging task to develop solid catalysts that improve the monoester yield under mild reaction conditions [105, 106]. Preparation of monoglycerides (MG) from fatty acids or fatty methyl esters and glycerol can be carried out in the presence of acidic or basic catalysts. Solid-basic materials such as MgO, CeO2, LaO3, ZnO, Al-Mg hydrotalcites, Cs-exchanged sepiolite and mesoporous MCM-41 have been tested as potential catalysts for the glycerol transesterification with triglycerides [107, 108]. In glycerol transesterification with methyl stearate the activity of the solid-basic catalyst was related to the intrinsic basicity (La2O3 > MgO >> ZnO > CeO2) (see Table 13.7) [108]. In the use of zeolites for production of MG from fatty acids and GL, the reaction is influenced by acid site strength and surface hydrophobicity [109, 110]. Functionalised mesoporous materials with organosulphonic groups have also been used in the esterification of fatty acids with alcohols [111, 112]. High catalytic activity and selectivity towards monoglycerides were observed in the esterification of FFAs with GL in relation to an increased hydrophobic character of the catalyst surface [112]. The selectivity to MG has been enhanced significantly over MCM-41 as a result of the shape selectivity effect. Corma et al. [107] described the catalytic activity of Cs-MCM-41 in transesterification of TG with glycerol to produce MG. Barrault et al. [113] prepared MgO/MCM-41 and MgO/AlMCM-41 catalysts for transesterification of several methyl esters (lauric, myristic and stearic) and glycerol. Despite improvements in MG selectivity when using mesoporous acid catalysts, a MG yield of 90%+ is required to avoid uneconomic distillation of the ester mixtures. Glycerol can also be converted into pure monoglycerides in the presence of a lipase from R. miehei and free acids as acyl donors [114]. The procedure is suitable for the conversion of CNO, PKO, RSO, SBO and SNO into monoglycerides. Table 13.7 Conversion and selectivity to mono-, di- and triglycerides in glycerol transesterification with methyl stearate after 6 h at 493 K (after ref. [108]) Catalyst Without La2O3 MgO ZnO CeO2 a

Conversion (%)a 2.5 97 83 18 4

Methyl stearate conversion.

Selectivity (%) Mono

Di

Tri

100 28 42 80 100

0 61 52 20 0

0 11 6 0 0

602

Biodiesel science and technology

Glycerol has also been esterified with acetic acid or transesterified with methyl acetate to yield triacetylglycerol (or triacetin) [22, 38, 115]. Solidacid catalysts show excellent catalytic behaviour in the esterification of glycerol with acetic acid to yield acetylated derivatives [116]. In particular, diacetylglycerol (DAG) and triacetylglycerol (TAG) are valuable petrol fuel additives leading to either enhanced cold and viscosity properties when blended with diesel fuel or anti-knocking properties when added to gasoline. Triacetin is also used as a plasticiser in various applications.

13.5.6 Selective etherification of glycerol Glycerol can be processed through selective etherification into various valuable marketable products, typically fuel additives (e.g. for reduced emissions) [117, 118], flavours (e.g. glucosylglycerol), solvents or biodegradable surfactants [104]. In fact, an important option for glycerol valorisation consists in using the product as a raw material for fuel applications. However, as glycerol is insoluble in hydrocarbons, conversion into soluble derivatives as fuel components is necessary. This can be achieved by etherification with an olefinic hydrocarbon (in particular isobutylene or isoamylene; see Fig. 13.14) or by transformation into acetals by reaction with aldehydes or ketones, in the presence of a strong homogeneous or heterogeneous acidic catalyst [24, 119–121]. The best results at 100% conversion of glycerol tert-butylation using isobutylene with 92%+ selectivities to di- and tri-ethers were obtained over strong acid macroreticular ion-exchange resins [8]. Alkyl ethers of glycerol have been explored for decades. Ether derivatives in gasoline reformation to form oxygenated gasoline (e.g. MTBE and ETBE) are well known. Their glycerol-based counterpart (glycerol tert-butyl ether, GTBE) is made easily using an acidic ion-exchange resin such as Amberlyst15® or Dowex-50®. These compounds (with low cetane number) can be blended directly with gasoline as alternatives to MTBE and ETBE [122] or can be added to the transesterified triglycerides to yield an improved biodiesel before being blended with the diesel fuel [123, 124]. A market need for tert-butyl esters from glycerol with a high content of di- and triethers is expected to develop in the near future. A 20 kt/yr GTBE plant is being planned (www.procede.nl); market introduction of solketal-tert-butyl ether (STBE) is foreseen by 2010 (www.biovalue.nl). CH2OH CHOH CH2OH

CH2OC4H9 + isobutene

acid catalyst

CHOH CH2OC4H9

13.14 Acid-catalysed preparation of glycerol ethers.

Valorisation of the glycerol by-product

603

US Patent No. 5,476,971 to Gupta [125] describes reacting pure glycerol with isobutylene in the presence of an acid catalyst in a two-phase reaction to produce mono-, di- and tri-tert-butyl ethers of glycerol. However, the crude glycerol co-product obtained in conventional biodiesel manufacturing using homogeneous base catalysts cannot be used directly for etherification or acetalisation as the transformation requires a neutral (and preferably almost anhydrous) glycerol. US Patent No. 5,308,365 to Kesling et al. [118] describes the use of glycerol di- and trialkyl ether derivatives mixed with diesel fuels to improve the particulate matter emissions content. US Patent No. 5,578,090 to Bradin [126] discloses an alternative fuel composition that includes a fuel additive composition based on fatty acid alkyl esters and glyceryl ethers. The resulting alternative fuel has a viscosity substantially similar to diesel fuel. The fuel additive composition was prepared by esterifying free fatty acids (from hydrolysis of triglycerides) and etherifying glycerol with olefins in the presence of a strong acid catalyst, e.g. Dowex-50®, in one or separate reactors. Even more importantly, US Patents No. 6,015,440 and 6,174,501 to Noureddini [123, 124] disclose cloud point, pour point and viscosity depressing properties of etherified glycerol. Di- and tri-ethers provide better biodiesel fuel improving results than mono-ethers. It is well known that the use of biodiesel fuel is limited in practice due to adverse cold temperature properties. Noureddini remedies this by describing an ‘oxygenated’ biodiesel fuel based on soy fatty acid esters and glycerol ethers with a cloud point reduced to approximately 266.4 K. A considerable drawback according to the invention is that glycerol obtained from soy biodiesel production using a homogeneous base catalyst needs to be neutralised (deionised) by strong cationic resins prior to etherification with isobutene. On the other hand, neutral, salt-free glycerol of 98% purity may be obtained in an alternative heterogeneously catalysed procedure using ZnAl2O4·xZnO·yAl2O3 according to Fr. Patent No. 2,752,242 to IFP [127], which allows direct use in solid acid-catalysed etherification/acetalisation of by-product glycerol after merely flashing to remove residual alcohol. This then provides the basis for two-step processes for the manufacture of two biofuels based on integral use of initial triglycerides according to Figs 13.15 (etherification of glycerol

TG + ROH (R = Me, Et)

Heterogeneous catalyst

FAAEs (conventional biodiesel) + Glycerol

H

New biofuel

+

GTBEs

isobutene

Gasoline formulations

13.15 Reaction scheme for integral use of triglycerides as biofuel by etherification of glycerol (after ref. [23]).

604

Biodiesel science and technology

with a C4 to C12 olefinic hydrocarbon) [23] and 13.16 (glycerol acetalisation/ ketalisation) [22]. Some work has also been described on the preparation of ketals of glycerol by reaction with acetone or aldehydes over Amberlyst-15® [22, 38]. Soluble glycerol ethers and acetals may be incorporated in various amounts (1–20%) in gasoline or biodiesel fuels. Benefuel Inc. (Mt. Prospect, IL) uses a new dual metal catalytic (DMC) process for transesterification of triglycerides (ENSELTM), followed by costeffective alkylation of glycerol (97–99.9% purity) to glycerol polyethers in a second process using solid catalysts [128]; (see Section 15.3.1). The proposed scheme is an effective solution to the glycerol glut. Incorporation into RME of a mixture of mono-, di- and tri-tert-butyl ethers (with average composition of di-tert-butyl ether), obtained by etherification with isobutene of the entire volume of glycerol derived from methanol transesterification of rapeseed oil, leads to an improved biodiesel composition of 82% RME and 18% glycerol ethers. This green product can be used in diesel engines either directly or admixed in all proportions with conventional biodiesel. The reaction of glycerol and n-butyraldehyde in the presence of the acidic Amberlyst-15® resin at 326 K in 7 h leads to a mixture of isomers, as follows: CH2—O

CH2OH CHOH

CH3CH2CH2–CHO H+ /–H2O

CH2OH

CHCH2CH2CH3

CH—O CH2OH

13.10

+ H2C



O

HO—H2C

CHCH2CH2CH3

H 2C

O

Incorporation into RME of 2,2-dimethyl-1,3-dioxolane-4-methanol (solketal), obtained by acetalisation with acetone of all glycerol derived FAAEs TG (conventional biodiesel) + Heterogeneous + Glycerol catalyst ROH (R = Me, Et) R1

New biofuel

H+ C O

R2

Glycerol acetals H2 O

Gasoline formulations

13.16 Reaction scheme for integral use of triglycerides as biofuel by acetalisation of glycerol (after ref. [22]).

Valorisation of the glycerol by-product OH HO

OH

CH C H2

C H2

OH

–H2O

HO

OH O

CH C H2

CH

C H2

Glycerol

605

C H2

OH

C H2

Diglycerol

+ Glycerol – H 2O OH HO

OH

CH C H2

O C H2

OH

CH C H2

O C H2

CH C H2

C H2

OH

Triglycerol

+ x Glycerol – xH2O Polyglycerols

RCOOH(Me)

Polyglycerol esters + H2O (MeOH)

13.17 Glycerol oligomerisation and polyglycerol esterification.

from methanolysis of RSO, leads to a new biodiesel composition of 87.5% RME and 12.5% solketal with improved properties. Diesel fuel compositions containing glycerol acetals show particulate emission reduction [24]. Glycerol ethers as fuel components were reviewed in ref. [90]. Polyglycerols (PGs) and polyglycerol esters (PGEs) are normally obtained from the selective etherification of glycerol and the esterification or transesterification of the oligomers with fatty acids or methyl esters in the presence of homogeneous or heterogeneous catalysts (Fig. 13.17). These products have potential in application as biodegradable surfactants, lubricants, cosmetics, food additives and solvents. Polyglycerols may be used as substitutes for ethylene oxide and polyoxyethylene. Several glycerolderived polymers are available commercially. Glycerol may be etherified to polyglycerol using solid-base catalysts [80, 129]. Clacens et al. [83] reported the catalytic activity of silica or aluminosilica mesoporous materials impregnated with different elements (Li, Cs, La, Na, Mg) on the solvent-free polymerisation of glycerol. Caesium impregnated onto MCM-41 type mesoporous catalysts gave the best activity as well as significant selectivity towards di- and triglycerols. Glycerol oligomerisation was reviewed in ref. [40].

13.5.7 Epichlorohydrin In the past, synthetic processes for glycerol were developed based on various starting products, including epichlorohydrin (ECH), obtained from propylene.

606

Biodiesel science and technology

The reaction scheme of transformation of epichlorohydrin into glycerol (and vice versa) is as follows: CH2

O

CH

CH2OH +H2O

CHOH

CH2OH –HCl

CH2Cl

CH2Cl

CH CH2

CH2OH +H2O

O

CHOH CH2OH 13.11

Meanwhile, the allylic derivative ECH has developed as an important intermediate in the production of epoxy resins, and current global capacity – all petrochemical – is about 1.4 Mt/yr. The EpicerolTM process, recently developed by Solvay (covered by 22 pending patent applications), allows the direct synthesis of dichloropropanol, an intermediate product, from glycerol and HCl. The term ‘dichloropropanol’ comprises a mixture of isomers consisting essentially of 1,3-dichloropropane2-ol and 2,3-dichloropropane-1-ol. The former is particularly suitable as a starting product for a dehydrochlorination with a view to producing epichlorohydrin. Solvay developed the glycerol-based process described in earlier scientific literature [130] and made its industrialisation possible thanks to the application of an entirely new class of catalysts. In the process, chlorohydrin (i.e. dichloropropanol) is produced by liquid phase reacting glycerol with anhydrous or aqueous HCl at about 393 K and 1 MPa, preferably in the presence of an aliphatic or aromatic carboxylic acid catalyst (e.g. adipic acid) [131–137]. Dehydrative chlorination is then followed by a second step – dehydrochlorination – which generates the final product, epichlorohydrin [133, 135, 138–140]: OH Cl CH

HO C H2

OH C H2

HCl Catalyst

CH

Cl C H2

OH

NaOH

C H2 + OH

Cl

C H2

Cl

Cl

O CH H 2C

CH C H2

CH2

+ NaCl

13.12

The processes for producing ECH that are generally used, for example starting with allylchloride, lead to epichlorohydrin containing organic impurities

Valorisation of the glycerol by-product

607

which have drawbacks when the product is used in certain applications, such as epoxy resins. The EpicerolTM process (Eqn 13.12) makes it possible to produce highly pure ECH containing few bothersome impurities. Compared to the traditional epichlorohydrin synthesis (from propylene and chlorine), the EpicerolTM process is marked by a lower consumption of chlorine and water, consequently reducing chlorinated effluents. Solvay’s green chemistry technology for the manufacture of epichlorohydrin from glycerol derived from RSO (supplied by a French biodiesel producer) is operational in Tavaux (Jura, France) with a nameplate capacity of 10 kt/ yr (extendable) as from the second half of 2007; this retrofitted plant had formerly been used for decades to produce glycerol from epichlorohydrin. Solvay is planning a further 100 kt/yr production unit in Map Ta Phut, Thailand (start-up mid 2009). Epichlorohydrin is useful for condensation with glycerol in the manufacture of polyglycerol, for condensation with bisphenol-A in the synthesis of bisphenol-A glycidyl ethers (important precursors for epoxy resins) (see Fig. 13.18), in water purification and in reinforcement of paper. The EpicerolTM technology (Glycerine Innovation Award 2007) allows integrated production of biodiesel and glycerol by transesterification of plant oil with alcohols, epichlorohydrin formation from glycerol, and polyglycerol and epoxy resin manufacture [133]. Dow and Cargill have also announced projects for production of the epoxy resin raw material epichlorohydrin from biodiesel-derived glycerol rather than allyl chloride. Dow Epoxy’s 150 kt/yr ECH-from-glycerol plant at Shanghai Chemical Industry Park is expected to come on stream in 2010.

13.5.8 Carboxylation of glycerol Glycerol carbonate is a relatively new material to the chemical industry and could serve as a monomer for the synthesis of new functionalised polymers [141]. Various synthesis routes have been suggested [142–144]. Huntsman Corp. has developed an alkylene carbonate product based on bio-glycerine. The high yield preparation of low-cost glycidol (2-oxiranemethanol) from glycerol carbonate (and thus from low-cost glycerol) has also been reported [145]. Alternative value-adding chemicals such as glycidol are particularly interesting as this chemical has conventionally been synthesised from epichlorohydrin – a product from the chlorination of allyl alcohol. Epichlorohydrin, which in the past was used to produce glycerol, can now be produced from glycerol (e.g. EpicerolTM) (see Fig. 13.19).

13.5.9 Biochemical conversion of glycerol In most chemoselective catalytic processes, it is difficult to directly use crude glycerol with high levels of contaminants; this offers an opportunity for

608

HO

C

O OH

+

H2C

CH

C Cl H2

CH3 bisphenol A

H2C

epichlorohydrin

OH

CH3

O CH

C O H2

C

NaOH

O

CH3

13.18 Synthesis of bisphenol-A glycidyl ethers.

C H2

CH

H2 C

CH3 C

O n

CH3

O

H2 C

O CH

CH2

Biodiesel science and technology

CH3

Valorisation of the glycerol by-product OH

609

O

H 2C

H2C

Epicerol™

OH

CH

CH

(Past)

H 2C

C H2

Cl

ECH

OH GL

CO2

HO

O

H2C

KOH/ROH

C

CH C H2

O

O

O

H2C

D

CH

–CO2

Glycerol carbonate

C H2

OH

Glycidol

13.19 Schematic of production of glycerol carbonate and glycidol from glycerol (GL) and epichlorohydrin (ECH). Transesterification

Algal oil

Extraction

Transesterification Biodiesel

E. coli fermentation Cl os Algal tri di fermentation um

Crude glycerol

Omega-3 fatty acid rich algae

Ethanol

Butanol

Animal ‘extractors’ Omega-3 rich food

13.20 Biochemical use of crude glycerol as an organic carbon source.

biocatalytic transformations. In view of its low price level and availability, aqueous glycerol is now very competitive to sugars and carbohydrates in the production of chemicals and fuels by fermentative processing (see Fig. 13.20). It is possible to use the crude glycerol by-product from the biodiesel industry as a carbon source for microalgae that produce omega-3 fatty acids in high content [146, 147]. Gonzalez et al. [148] have developed a glycerin-toethanol fermentation process using E. coli. Green Biologics, Ltd (Abingdon, UK) is focusing on producing biobutanol from waste glycerin and molasses using genetically engineered Clostridium microbial strains, thus eventually allowing integrated biodiesel/biobutanol (ButafuelTM) plants. In addition, butyl biodiesel (with reduced cloud point) improves the renewable nature

610

Biodiesel science and technology

of biodiesel by substituting fossil-derived methanol. Concentrated glycerin (22%) can also be converted into high-purity D-glycerin acid [148a]. Biochemical oxidation of glycerol by the bacterium Acetobacter suboxydans favours conversion to dihydroxyacetone in high yield and selectivity [149]. Other research activities are directed towards the use of low-value biodiesel glycerol as a fermentative substrate to produce value-added biogradable polymers, such as poly(hydroxyalkanoates) (PHA) [5]; the bacterium Pseudomonas putida KT 2440 is active in this process [150]. Potential exists for the use of bacteriologically transformed crude glycerol to form other products useful in plastics production [151]. Glycerol can be fermented anaerobically to 1,2-PD using E. coli [152]. Glycerol can also be fermented to 1,3-propanediol [153–155]. Bioconversion processes for the production of 1,3-PD from raw glycerol waters from FAME production without further pre-treatment are of considerable interest [156, 157]. The fermentation of glycerol to 1,3-propanediol has been studied using microorganisms such as Klebsiella pneumoniae [158–163], Citrobacter freundii [163, 164], Clostridium butyricum [165–168] and Enterobacter agglomerans [169]. In fermentation of glycerol at low concentrations (5 g/L) by C. butyricum moderate yields (60%) of 1,3-PD were achieved [166]. Similarly, in another microbiological process, 3% glycerol solutions could be converted to 1,3-PD by means of K. pneumoniae NRRL B-199 [158]. In both processes the space-time yield was low, recovery of 1,3-PD from the very dilute fermentation solutions energy-intensive and 1,2-PD was formed. Also the microbial production of 1,3-PD by C. butyricum VPI 3266 using a synthetic medium and raw glycerol [165] and by K. pneumoniae using crude glycerol from biodiesel preparations [159] have been reported. New microorganisms enable product concentrations of more than 100 g/L (Fig. 13.21 [170]) to be obtained from pharma glycerol. Biochemical production of 1,3-PD by use of low priced crude glycerol or glycerol-water (Fig. 13.22) has also been indicated. However, at the present time, glycerol is too expensive a substrate for fermentation to compete with synthetic methods. Advances in metabolic engineering might allow economic competitiveness with synthetic routes [155]. In a combined one pot biocatalytic (C. butyricum)/chemocatalytic (Ir catalyst) process, waste glycerol can be converted to valuable secondary amines in a biphasic system without isolation of the 1,3-PD intermediate [171]. Glycerol and the 1,3-PD fermentation waste streams may also be used to generate electricity or hydrogen in microbial fuel cells [172]. Microbial fuel cells use bacteria to oxidise organic matter to produce electricity. To produce hydrogen instead of electricity, the microbial fuel cell is modified to be anaerobic and a small input of electrical energy is added. Recently, Minteer et al. [173] have described enzyme-based biofuel cells as potential

Valorisation of the glycerol by-product

100

611

1,3-Propanediol Strain IK 123

Concentration (g/L)

80

60 Glycerol 40

Butyrate

20

Acetate 0 0

10

20

30 40 Time (h)

50

60

70

13.21 1,3-Propanediol production from pharma glycerol with a new strain from screening (after ref. [170]).

battery replacements. Using alcohol and aldehyde dehydrogenase enzymes, extracted from the bacteria Gluconobacter and immobilised on hydrophobically modified Nafion, power outputs of some 70 mW/cm2 of methane were achieved (enough to run a small mobile phone) with glycerol as a fuel [174].

13.6

Renewable diesel synthesis without glycerol co-production

By using methylacetate instead of methanol as a novel acyl acceptor for biodiesel production the higher valued product triacetylglycerol is being generated, instead of glycerol (see Eqn 10.1) [175]. As 25 wt% triacetylglycerol (TAG) is produced in the process, this contributes considerably to the reduction of product cost. Table 13.8 compares the Novozym 435 lipasecatalysed transformation of SBO for both acyl acceptors. Unfortunately in this case, the reaction rate with methyl acetate is unfavourable as compared to methanol. Different catalysis might be a pursuable option. Recently, Saka and Isayama [176] have described biodiesel production without producing glycerol from oils and fats with using supercritical carboxylate esters (methyl acetate and formate). Also the TBK-biodiesel process [25],

612

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100 1,3-Propanediol

Concentration (g/L)

80

60

Glycerol

40

20 Butyrate Acetate 0 0

10

20

30 Time [h]

40

50

13.22 1,3-Propanediol production from raw glycerol-water with a new strain from screening (after ref. [170]). Table 13.8 Comparison of lipase-catalysed transformation of SBO for biodiesel production with two different acyl acceptors (after ref. [175]) Methanol

Methyl acetate

- Negative effect of methanol and + glycerol on enzyme activity + - Much lower methyl ester yield for + crude SBO as compared to refined SBO - Glycerol co-production + + -

No negative effect of methyl acetate and TAG on enzyme activity Increased lipase operational life (lower catalyst cost) Equal ester yield (92%) for crude and refined oil sources Production of higher valued TAG Reduction of biodiesel production costs Low reaction rate

+ = benefit   – = disadvantage.

based on transesterification with esters (instead of alcohols), avoids glycerol generation (see Eqn 13.1). Glycerol-free biodiesel can be produced from feedstocks based entirely on free fatty acids, such as wood extractives and grease trap wastes. Sweden shows interest in producing biodiesel from wood extractives: a 50 kt/yr plant

Valorisation of the glycerol by-product

613

is being designed. As this new feedstock is based entirely on free fatty acids, no glycerol is being produced and the major by-product is resin acids, which is a very valuable base chemical (see also Section 9.7). In PCT Int. Publ. No. WO 2004/048311 (to Biodiesel Australia), Muskett and Anderson [177] claim low or no glycerol production by (trans)esterification of high fatty acid content lipids, such as grease trap wastes, containing n-hexadecanoic and octadecanoic acid as the major components (see also Table 7.3). Processes for producing biodiesel fuels that conveniently reclaim the byproduct glycerol have great utility, even more so when glycerol is reclaimed in the produced biodiesel fuel in a way that improves the fuel properties. A viable alternative to the low-purity glycerol produced during biodiesel processing is the preparation of glycerol-based additives for biodiesel, making good use of the surplus production of glycerol and improving overall production economies [122]. Reformulated biodiesel fuels have been described consisting of a mixture of transesterified triglycerides, and etherified or acetalised glycerol. US Patent No. 6,174,501 to Noureddini [124] describes a two-step process comprising transesterification of SBO using a homogeneous base catalyst and the separated etherification of glycerol with isobutylene or isoamylene using Amberlyst-15®. The mixture of tert-butyl ethers of glycerol (GTBE) so obtained, blended with standard biodiesel, results in a fuel with lower viscosity, cloud and pour point characteristics, thus with improved flow properties at low temperature, more similar to petrodiesel. The conversion process is facilitated using neutral, salt-free glycerol of 98% purity, as obtained by transesterification of vegetable oils using a heterogeneous solid catalyst (ZnAl2O4 · xZnO · yAl2O3), according to Fr. Patent No. 2,752,242 to IFP [127]. The two types of biofuel, based on etherification [23] or acetalisation (ketalisation) [22] of the by-product glycerol, make integral use of the initial triglycerides (green products). Similarly, NCL’s solid-phase catalytic process for transesterification of triglycerides (ENSELTM) may be combined with another cost-effective process for converting glycerol into glyceryl polyethers, thus overcoming the glycerol glut. An even more appealing process would be based on in-situ etherification of glycerol, without the need for glycerol separation and subsequent blending. However, in the presence of a strong acid catalyst, olefins and an alcohol, this could result in alcohol olefin etherification and/or olefin polymerisation. More detailed studies of the synthesis of glycerol ether additives to improve the flow properties of biodiesel are wanted. Several conversion processes of plant oils have been described which avoid the generation of glycerol. US Patent Appl. No. 2006/0288636 A1 to Iijima et al. [178] discloses a non-catalytic partial and degradative transesterification process for producing an unconventional biodiesel fuel

614

Biodiesel science and technology

(mainly composed of FAME, MG, DG, and other aliphatic – degradation – compounds) from animal/vegetable fat or waste edible oil, without yielding glycerol as a by-product. The methanolysis reaction is carried out under supercritical reaction conditions (T = 643–773 K, p = 20–60 MPa, tr = 4–12 min., TG/MeOH volume ratio of 1 : 2 to 2 : 1) wherein substantially no glycerol is generated or the generated glycerol is not separated from the biodiesel fuel. As the viscosities of MG and DG with long-chain fatty acid groups are higher than those of FAME and quite detrimental for use in biodiesel fuel, experimentally provision has been taken for the simultaneous conversion of the long-chain fatty acids to medium-chain (C 6 to C12) fatty acid groups in the reaction conditions of the methanolysis process. This lowers the viscosity of a FAME, DG and MG mixture. The biodiesel fuel obtained has a cetane number of 49–65, flash point of 373–473 K, kinematic viscosity at 303 K of 3 mm2/sec to 20 mm2/sec, and a pour point of 268 K or lower. Since no by-product is produced, the biodiesel fuel yield can be enhanced. The non-catalytic technique eliminates the need for pre-treating the starting material, for neutralisation and washing of the products, and for purging of washing liquid, all of which are essential in conventional production techniques. The emerging vegetable oil hydrogenation technology producing hydrodiesel is becoming established at existing refineries (e.g. Neste Oil’s 170 kt/yr plant in Porvoo, 2007, and 800 kt/yr plant in Singapore, 2010; Eni’s 250 kt/yr plant in Livorno, 2009). This superior industrial hydrocarbon fuel contributes to avoiding the glycerol glut problem using triglyceride feedstocks. US Patent No. 6,364,917 to Matsumura and Murakami [179] discloses a method of converting virgin plant oils and/or waste vegetable oils into (diesel) fuel, by heating the oil, mixing the oil with water and/or ozone and agitating the mixture of oil and water, dissipating the ozone. The end product has lower average molecular weight than petrodiesel as a result of formation of ozonides (1,2,4-trioxolane rings) and bond rupture in the fatty acids composing the vegetable oil (i.e. aldehyde formation) [180]. Obviously, the chemistry of the resulting fuel differs totally from that of transesterification or hydrotreating technology. Ozonation hardly produces any post-refining waste matter. In principle, the glycerol problem in connection to conventional biodiesel fuel production can be avoided totally by direct use of short-chain triglycerides (SCT), i.e. even without the need for transesterification. Unfortunately, nature does not supply sufficient plant oil volumes of high SCT level (see also Section 3.5). Conventionally, the term biodiesel fuel has been used to identify esterified triglycerides. As mentioned above, alkane biodiesel derives from hydrogenation of the same source, but without glycerol co-production. Also amide biodiesel has been reported, resulting from amidation of triglycerides

Valorisation of the glycerol by-product

615

with diethylamine, however with glycerol co-production [181]. Amide biodiesel is not commercially available.

13.7

Bibliography

M. Pagliaro and M. Rossi, The Future of Glycerol. New Usages for a Versatile Raw Material, RSC Publishing, Cambridge (2008). G. Centi and R.A. Van Santen (eds), Catalysis for Renewables, Wiley-VCH, Weinheim (2007). G. Knothe, J. Van Gerpen and J. Krahl (eds), The Biodiesel Handbook, AOCS Press, Urbana, IL (2005). T. Werpy and G. Petersen (eds), Top-value Added Chemicals from Biomass, Vol. 1, US DOE, Washington, DC (2004). J.R. Rostrup-Nielsen, Steam Reforming Catalysts, Danish Technical Press, Copenhagen (1975).

13.8

References

[1] C. O’Driscoll, Seeking a new role for glycerol, Biofuels Bioprod. Bioref. 1 (2007) 6–7. [2] A. Behr, New chemical products on the basis of glycerol, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [3] S. Lux, V. Mertlitz, T. Hilber, M. Siebenhofer and R. Marr, Conversion of dihydroxyacetone to lactic acid, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [4] N.S. Mhase, Glycerol – a hydrogen source, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [5] D.K.Y. Solaiman, R.D. Ashby, B. Panilaitis, D.L. Kaplan, T.A. Foglia and W.N. Marmer, Industrial biochemicals from fermentation of glycerol and soy molasses, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [6] W.R. Sutterlin, A. Takeei, B. Sawyer and G.J. Suppes, New phase conversion of biodiesel crude glycerin to propylene glycol, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [7] S. Miele and E. Bargiacchi, Glycerol phase from biodiesel cycle: a potential feedstock for material and energy production, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [8] R.S. Karinen and A.O.I. Krause, New biocomponents from glycerol, Appl. Catal. A: Gen. 306 (2006) 128–33. [9] L. Pasteur, Production constante de glycerine dans la fermentation alcoolique, C.R. Acad. Sci. 46 (1858) 857. [10] Z.-X. Wang, J. Zhuge, H. Fang and B.A. Prior, Glycerol production by microbial fermentation: a review, Biotechn. Adv. 19 (2001) 201–23. [11] HBI Report, Oleoline Glycerine Market Report (Mar. 2002). [12] W. De Greyt, J. Maes, F. Soragna and M. Kellens, Processing pathways to an improved yield and quality of biodiesel from vegetable oils and animal fats, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007).

616

Biodiesel science and technology

[13] T.A. Werpy and G. Petersen (eds), Top-value Added Chemicals from Biomass, Vol. 1, US DOE, Washington, DC (2004). [14] F. Ma and M.A. Hanna, Biodiesel production: a review, Bioresour. Technol. 70 (1999) 1–15. [15] H.S. Muralidhara and M.K. Ko (to Cargill), Process for the purification of crude glycerol compositions, PCT Int. Publ. No. WO 2008/156612 A1 (24 Dec. 2008). [16] X. Lancrenon and J. Fedders, An innovation in glycerin purification, Biodiesel Mag. 5(6) (2008) 100–3. [17] G. Rothenberg, Catalysis. Concepts and Green Applications, Wiley-VCH, Weinheim (2008), p. 171. [18] S. Claude, Research of new outlets for glycerol. Recent developments in France, Fett/Lipid 101 (3) (1999) 101–4. [19] K. Wiedermann, G. Tomberger and B. Hauser, Fuel for automatic ignition internal combustion engines, PCT Intl. Publ. No. WO 2001/012756 (22 Feb. 2001). [20] A. Demirbaş, Conversion of biomass using glycerin to liquid fuel for blending gasoline as alternative engine fuel, En. Conv. Managm. 41 (2000) 1741–8. [21] M. Noel (to Oleo SA), Glycerol-based fuel, Eur. Pat. EP 2,011,852 A1 (7 Jan. 2009); PCT Int. Publ. No. WO 2009/007306 A1 (15 Jan. 2009). [22] B. Delfort, G. Hillion and I. Durand (to IFP), Procédé de fabrication de biocarburants. Transformation de triglycerides en deux familles de biocarburants: Monoesters d’acides gras et acetales solubles du glycerol, Fr. Pat. 2,866,654 (26 Aug. 2005). [23] G. Hillion, B. Delfort and I. Durand (to IFP), Procédé de fabrication de biocarburants. Transformation de triglycerides en deux familles de biocarburants: monoesters d’acides gras et ethers solubles du glycerol, Fr. Pat. 2,866,653 (26 Aug. 2005). [24] B. Delfort, I. Durand, A. Jaecker, T. Lacome, X. Montagne and F. Paille (to IFP), Compositions de carburants diesel contenant des acetals de glycerol, Fr. Pat. 2,833,607 A1 (20 June 2003). [25] J. Thész, B.I. Boros and Z. Király, Use of fuels or fuel additives based on triglycerides of modified structure and process for their preparation, PCT Int. Publ. No. WO 2008/096187 A1 (14 Aug. 2008). [26] Economic Research Service, USDA (6 Sept. 1996). [27] A. Radich, Biodiesel production methods, costs and available capacity; www. distibutiondrive.com/Article15.html [28] K.S. Tyson, Biodiesel R&D potential, Presentation at the Montana Biodiesel Workshop (8 Oct. 2003). [29] E. Ahn, M. Koncar, M. Mittelbach and R. Marr, A low-waste process for the production of biodiesel, Sep. Sci. Techno. 30 (1995) 2021–33. [30] C. Kijora and R.D. Kupsch, Evaluation of technical glycerols from ‘biodiesel’ production as a feed component in fattening of pigs, Fett/Lipid 98 (7/8) (1996) 240–5. [31] B. Kerr, unpublished results (2008). [32] B. Vojtisek, F. Vacek, J. Poul, L. Urban, J. Kratky, R. Dvorak and M. Simek (to Vyzkumny Ustov Veterinarniho Lakarstvi), Process for preparing feed supplements for ruminants, Czech Pat. 285,745 B6 (13 Oct. 1999). [33] P. Bondioli, From oil seeds to industrial products: present and future oleochemistry, J. Synth. Lubr. 21 (2005) 332–43. [34] C.-H. Zhou, J.N. Beltramini, Y.-X. Fan and G.Q. Lu, Chemoselective catalytic

Valorisation of the glycerol by-product

[35] [36] [37] [38] [39]

[40]

[41] [42]

[43] [44] [45]

[46] [47] [48] [49] [50] [51] [52] [53] [54] [55]

[56]

617

conversion of glycerol as a biorenewable source to valuable commodity chemicals, Chem. Soc. Rev. 37 (2008) 527–49. A. Meffert, Technical uses of fatty acid esters, J. Am. Oil Chem. Soc. 61(2) (1984) 255–8. S. O’Connor, unpublished results (2009). R. Wessendorf and W. Graf, Verfahren zur Herstellung von Polyalkylethern, Eur. Pat. Appl. EP 718,270 A2 (21 Dec. 1995). R. Wessendorf, Derivatives of glycerol as components of fuels, Erdöl & Kohle, Erdgas, Petrochem. 48 (1995) 138–43. D.M. Yost, D.B. Appleby and J.K. Spooner-Wyman, Evaluation of dibutoxyglycerol (DBG) for use as a diesel fuel blend component, in Advanced Diesel Engines and Liquid Alternative Fuels, SAE Intl. (Spec. Publ.) SP-1791 (June 2003), Paper no. 2003-01-2281. B. Sels, E. D’Hondt and P. Jacobs, Catalytic transformation of glycerol, in Catalysis for Renewables (G. Centi and R. van Santen, eds), Wiley-VCH, Weinheim (2007), pp. 223–56. K.S. Tyson, J. Bozell, R. Wallace, E. Petersen and L. Moens, Biomass Oil Analysis, Research Needs and Recommendations, NREL/TP-510-34796 (2004). K. Miltenberg, Hydroxycarboxylic acids, aliphatic, in Ullmann’s Encyclopedia of Industrial Chemistry, 5th edn (B. Elvers, S. Hawkins, M. Ravenscroft, J.F. Rounsaville and G. Schulz, eds), VCH Publishers, New York, NY (1987), Vol. A13, p. 507. R. Garcia, M. Besson and P. Gallezot, Chemoselective catalytic oxidation of glycerol with air on platinum metals, Appl. Catal. A: Gen. 127 (1995) 165–76. S.C. Tsang, unpublished results (2008). C. Hulteberg, J. Brandin, R.R. Woods and B. Porter (to Primafuel, Inc.), Gas phase process for monoalcohol production from glycerol, PCT Int. Publ. No. WO 2008/144448 A1 (27 Nov. 2008). R. Perrin and J.P. Schraff, Chimie Industrielle, Masson Ed., Paris (1993). Anon., Propylene glycol, Chemical Profile, Chemical Market Reporter 249 (1996) 37. C. Potera, Genencor & DuPont create ‘green’ polyester, Genet. Engng. News 17 (1 June 1997) 17. K.T. Lam, J.B. Powell and P.R. Wieder (to Shell), Process for preparing 1,3propanediol, PCT Int. Publ. No. WO 97/16250 (7 May 1997). F.R. Lawrence and R.H. Sullivan (to E.I. du Pont de Nemours), Process for making a dioxane, US Pat. 3,687,981 (29 Aug. 1972). D. Arntz, T. Haas, A. Müller and N. Wiegand, Kinetic studies on the hydration of acrolein, Chem. Ing. Tech. 63 (1991) 733–5. D.C. Cameron, N.E. Altaras, M.L. Hoffman and A.J. Shaw, Metabolic engineering of propanediol pathways, Biotechnol. Progr. 14 (1998) 116–25. N.E. Altaras and D.C. Cameron, Metabolic engineering of a 1,2-propanediol pathway in Escherichia coli, Appl. Environ. Microbiol. 65 (1999) 1180–5. T.M. Che (to Celanese), Production of propanediols, US Pat. 4,642,394 (10 Feb. 1987). T. Haas, A. Neher, D. Arntz, H. Klenk and W. Girke (to Degussa AG), Process for the simultaneous production of 1,2- and 1,3-propanediol, US Pat. 5,426,249 (20 June 1995). E. Drent and W.W. Jager (to Shell Oil Co.), Hydrogenolysis of glycerol, US Pat. 6,080,898 (27 June 2000).

618

Biodiesel science and technology

[57] M. Schlaf, P. Ghosh, P.J. Fagan, E. Hauptman and R.M. Bullock, Metal-catalyzed selective deoxygenation of diols to alcohols, Angew. Chem. Int. Ed. 40 (2001) 3887–90. [58] T.A. Werpy, J.G. Frye, A.H. Zacher and D.J. Miller (to Michigan State University), Hydrogenolysis of 6-carbon sugars and other organic compounds, PCT Int. Publ. No. WO 03/035582 A1 (23 Oct. 2002). [59] T. Miyazawa, Y. Kusunoki, K. Kunimori and K. Tomishige, Glycerol conversion in the aqueous solution under hydrogen over Ru/C + an ion-exchange resin and its reaction mechanism, J. Catal. 240 (2006) 213–21. [60] C. Montassier, D. Giraud and J. Barbier, Polyol conversion by liquid phase heterogeneous catalysis over metals, Stud. Surf. Sci. Catal. (1988), pp. 165–70. [61] C. Montassier, D. Giraud, J. Barbier and J.-P. Boitiaux, Polyol transformation by liquid phase heterogeneous catalysis over metals, Bull. Soc. Chim. Fr. (1989), 148–55. [62] T. Fleckenstein, G. Göbel and F.-J. Carduck (to Henkel), Herstellung von 1,2Propanediol aus Glycerin, Germ. Pat. DE 4,302,464 A1 (4 Aug. 1994). [63] L. Schuster and M. Eggersdorfer (to BASF AG), Preparation of 1,2-propanediol, US Pat. 5,616,817 (1 Apr. 1997). [64] J. Chaminand, L. Djakovitch, P. Gallezot, P. Marion, C. Pinel and C. Rosier, Glycerol hydrogenolysis on heterogeneous catalysts, Green Chem. 6 (2004) 359–61. [65] M.A. Dasari, P.-P. Kiatsimkul, W.R. Sutterlin and G.J. Suppes, Low-pressure hydrogenolysis of glycerol to propylene glycol, Appl. Cat. A: Gen. 281 (2005) 225–31. [66] M.A. Dasari and G. Suppes, Hydrogenolysis of crude glycerin to propanediols for use as antifreeze, Abstr. 36th Great Lakes Regional Mtg. ACS, Peoria, IL (17–20 Oct. 2004). [67] C.-W. Chiu, M.A. Dasari, G.J. Suppes and W.R. Sutterlin, Dehydration of glycerol to acetol via catalytic reactive distillation, AIChE J. 52 (2006) 3543–8. [68] Chemical Market Reporter, 1092-0110, 265(17) (26 Apr., 2004) 20(4). [69] G.J. Suppes, W.R. Sutterlin and M.A. Dasari, Method of producing lower alcohols from glycerol, catalytic hydrogenation process, and antifreeze composition, US Pat. 2005/244312 A1 (3 Nov. 2005). [70] G.J. Suppes, W.R. Sutterlin and M.A. Dasari, Method of producing lower alcohols from glycerol, PCT Int. Publ. No. WO 2005/095536 A2 (13 Oct. 2005). [71] S.P. Crabtree, R.C. Lawrence, M.W.M. Tuck and D.V. Tyers, Optimize glycol production from biomass, Hydrocarb. Proc. 85 (2006) 87–92. [72] S.P. Crabtree, R.C. Lawrence, M.W.M. Tuck and D.V. Tyers, Novel catalysis for glycol manufacture, Proc. 7th World Congr. Chem. Engng., Glasgow (10–14 July 2005). [73] M.W.M. Tuck and S.N. Tilley (to Davy Process Technology, Ltd.), Vapour-phase hydrogenation of glycerol, PCT Int. Publ. No. WO 2007/010299 A1 (25 Jan. 2007). [74] E. D’Hondt, S. van de Vyver, B.F. Sels and P.A. Jacobs, Catalytic glycerol conversion into 1,2-propanediol in absence of added hydrogen, Chem. Commun. (2008) 6011–12. [75] R. Milby, Sustainable polyester via 1,3-propanediol from corn, Proc. Industrial Applications of Renewable Resources, AOCS, Chicago, IL (11–14 Oct. 2004). [76] G.M. Whited, B. Bulthuis, D.E. Trimbur and A.A. Gatenby (to E.I. Du Pont de Nemours & Co.), Method for the production of 1,3-propanediol by recombinant

Valorisation of the glycerol by-product

[77] [78] [79]

[80] [81]

[82] [83]

[84]

[85]

[86]

[87]

[88]

[89]

[90]

[91]

[92]

[93]

619

organisms comprising genes for Vitamin B12, PCT Int. Publ. No. WO 99/10356 (12 May 1999). K. Wang, M.C. Hawley and S.J. DeAthos, Conversion of glycerol to 1,3-propanediol via selective dehydroxylation, I&EC Res. 42 (2003) 2913–23. Schering-Kahlbaum A.G., Procédé de fabrication d’acroléine, Fr. Pat. 695,931 (3 Dec. 1930). K. Ishikawa, K. Watabe, T. Hobo and S. Suzuki, Generation of trace amount of acrolein standard gas using reaction gas chromatography, Bunseki Kagaku 32 (1983) E321–5. E. Schwenk, M. Gehrke and F. Aichner (to Schering-Kahlbaum A.-G.), Production of acrolein, US Pat. 1,916,743 (4 July 1933). L. Ott, M. Bicker and H. Vogel, Catalytic dehydration of glycerol in sub- and supercritical water: a new chemical process for acrolein production, Green Chem. 8 (2006) 214–20. M. Watanabe, T. Iida, Y. Aizawa, T.M. Aida and H. Inomata, Acrolein synthesis from glycerol in hot-compressed water, Bioresour. Technol. 98 (2007) 1285–90. J.-M. Clacens, Y. Pouilloux and J. Barrault, Selective etherification of glycerol to polyglycerols over impregnated basic MCM-41 type mesoporous catalysts. Appl. Catal. A: Gen. 227 (2002) 181–90. R.R. Soares, D.A. Simonetti and J.A. Dumesic, Glycerol as a source for fuels and chemicals by low-temperature catalytic processing, Angew. Chem. Intl. Ed. 45 (2006) 3982–5. D.A. Simonetti, J. Rass-Hansen, E.L. Kunkes, R.R. Soares and J.A. Dumesic, Coupling of glycerol processing with Fischer-Tropsch synthesis for production of liquid fuels, Green Chem. 9 (2007) 1073–83. G.W. Huber, J.N. Chheda, J.C. Barrett and J.A. Dumesic, Production of liquid alkanes by aqueous-phase processing of biomass-derived carbohydrates, Science 308 (2005) 1446–50. G.W. Huber, R.D. Cortright and J.A. Dumesic, Renewable alkanes by aqueousphase reforming of biomass-derived oxygenates, Angew. Chem. Intl. Ed. 43 (2004) 1549–51. R.D. Cortright and P.G. Blommel (to Virent Energy Systems, Inc.), Synthesis of liquid fuels and chemicals from oxygenated hydrocarbons, US Pat. Appl. 2008/216391 A1 (11 Sept. 2008). R.R. Davda, J.W. Shabaker, G.W. Huber, R.D. Cortright and J.A. Dumesic, A review of catalytic issues and process conditions for renewable hydrogen and alkanes by aqueous-phase reforming of oxygenated hydrocarbons over supported metal catalysts, Appl. Catal. B: Environm. 76 (2005) 171–86. T.S. Viinikainen, R.S. Karinen and A. Outi I. Krause, Conversion of glycerol into traffic fuels, in Catalysis for Renewables (G. Centi and R. van Santen, eds), Wiley-VCH, Weinheim (2007), pp. 209–22. R.R. Davda, J.W. Shabaker, G.W. Huber, R.D. Cortright and J.A. Dumesic, Aqueous-phase reforming of ethylene glycol on silica-supported metal catalysts, Appl. Catal. B: Environm. 43 (2003) 13–26. R.D. Cortright, R.R. Davda and J.A. Dumesic, Hydrogen from catalytic reforming of biomass-derived hydrocarbons in liquid water, Nature 418 (29 Aug. 2002) 64–7. A. Iriondo, V.L. Barrio, J.F. Cambra, P.L. Arias, M.B. Guemez, R.M. Navarro, M.C. Sánchez-Sánchez and J.L.G. Fierro, Hydrogen production from glycerol

620

[94] [95]

[96]

[97]

[98]

[99] [100]

[101] [102]

[103] [104] [105] [106]

[107]

[108]

[109]

[110]

[111]

Biodiesel science and technology obtained from biomass transesterification, Preprints ACS Div. Fuel Chem. 51 (2006) 557–8. S. Fernando and S. Adhikari, Glycerol steam reforming for hydrogen production, Abstr. 231st ACS Natl. Mtg., Atlanta, GA (26–30 Mar. 2006), PETR-004. S. Adhikari, S. Fernando, S.R. Gwaltney and A. Haryanto, Thermodynamic analysis of hydrogen production by steam reforming of glycerol, Preprints ACS Div. Fuel Chem. 51 (2006) 621–2. T. Ito, Y. Nakashimada, K. Senba, T. Matsui and N. Nishio, Hydrogen and ethanol production from glycerol-containing wastes discharged after biodiesel manufacturing process, J. Biosci. Bioengng. 100 (2005) 260–5. H. Hori, K. Koike, Y. Sakai, H. Murakami, K. Hayashi and K. Nomiya, New application of glycerin from a photochemical approach: dihydrogen formation from aqueous glycerin by use of giant polyoxometalate photocatalysts, En. Fuels 19 (2005) 2209–13. E.L. Kunkes, D.A. Simonetti, R.M. West, J.C. Serrano-Ruiz, C.A. Gärtner and J.A. Dumesic, Catalytic conversion of biomass to monofunctional hydrocarbons and targeted liquid-fuel classes, Science 322 (2008) 417–21. J.R. Rostrup-Nielsen, Steam Reforming Catalysts, Danish Technical Press, Copenhagen (1975). S. Adhikari, S. Fernando and A. Haryanto, Production of hydrogen by steam reforming of glycerin over alumina-supported metal catalysts, Catal. Today 129 (2007) 355–64. T. Hirai, N.-O. Ikenaga, T. Miyake and T. Suzuki, Production of hydrogen by steam reforming of glycerin on ruthenium catalyst, En. Fuels 19 (2005) 1761–2. S. Czernik, R. French, C. Feik and E. Chornet, Hydrogen by catalytic steam reforming of liquid byproducts from biomass thermoconversion processes, I&EC Res. 41 (2002) 4209–15. X. Xu, Y. Matsamura, J. Stenberg and M.J. Antal Jr, Carbon-catalyzed gasification of organic feedstocks in supercritical water, I&EC Res. 35 (1996) 2522–30. K. Gottlieb, H. Neitsch and R. Wessendorf, Glycerol, a sustainable raw material, Chem. Ing. Tech. 66 (1994) 64–6. N.O.V. Sonntag, Glycerolysis of fats and methyl esters. Status, review and critique, J. Am. Oil Chem. Soc. 59 (1982) A 795–802. C. Márquez-Alvarez, E. Sastre and J. Pérez-Pariente, Solid catalysts for the synthesis of fatty esters of glycerol, polyglycerols and sorbitol from renewable resources, Top. Catal. 27 (2004) 105–17. A. Corma, S. Iborra, S. Miquel and J. Primo, Catalysts for the production of fine chemicals. Production of food emulsifiers, monoglycerides, by glycerolysis of fats with solid base catalysts, J. Catal. 173 (1998) 315–21. S. Bancquart, C. Vanhove, Y. Pouilloux and J. Barrault, Glycerol transesterification with methyl stearate over solid basic catalysts. I. Relationship between activity and basicity, Appl. Catal. A: Gen. 218 (2001) 1–11. J. Aracil, A. Corma, M. Rodriguez and N. Sanchez, Process for the selective production of monoesters of diols and triols using zeolitic catalysts, PCT Int. Publ. No. WO 94/13617 (23 June 1994). M. da S. Machedo, J. Pérez-Pariente, E. Sastre, D. Cardoso and A.M. de Guereñu, Selective synthesis of glycerol monolaurate with zeolitic molecular sieves, Appl. Catal. A: Gen. 203 (2000) 321–8. I.K. Mbaraka, D.R. Radu, V.S.-Y. Lin and B.H. Shanks, Organosulfonic acid-

Valorisation of the glycerol by-product

[112]

[113] [114]

[115]

[116]

[117]

[118] [119] [120] [121]

[122] [123]

[124]

[125] [ 126] [127] [128] [129] [130] [131]

621

functionalized mesoporous silicas for the esterification of fatty acid, J. Catal. 219 (2003) 329–36. J. Pérez-Pariente, I. Díaz, F. Mohino and E. Sastre, Selective synthesis of fatty monoglycerides by using functionalised mesoporous catalysts, Appl. Catal. A: Gen. 254 (2003) 173–88. J. Barrault, S. Bancquart and Y. Pouilloux, Selective glycerol transesterification over mesoporous basic catalysts, C.R. Chimie 7 (2004) 593–9. B. Steffen, S. Lang, D. Hamann, P. Schneider, H.K. Cammenga and F. Wagner, Enzymic formation and physico-chemical behavior of uncommon monoglycerides, Fett Wissensch. Technol. 97 (1995) 132–6. J. Delgado Puche, Procedimiento para producir combustibles biodiesel con propiedades mejoradas a baja temperatura, Spanish Pat. 2,201,894 (18 Jan. 2002). J.A. Melero, R. van Grieken, G. Morales and M. Paniagua, Acidic mesoporous silica for the acetylation of glycerol: synthesis of bioadditives to petrol fuel, En. Fuels 21 (2007) 1782–91. L. Bournay, D. Casanave, B. Delfort, G. Hillion and J.A. Chodorge, New heterogeneous process for biodiesel production: a way to improve the quality and the value of the crude glycerin produced by biodiesel plants, Catal. Today 106 (2005) 190–2. H.S. Kesling, L.J. Karas and F.J. Liotta Jr. (to ARCO Chemical Technology), Diesel fuel, US Pat. 5,308,365 (3 May 1994). J. Gelas, Cyclic glycerol acetals: II. Synthesis and identification of hydroxylated and (or) chlorinated acetals, Bull. Soc. Chim. Fr. (6) (1970) 2341–9. T. Evans and K.R. Edlund (to Shell Development Co.), Process and product relating to tertiary ethers, U.S. Pat. 1,968,033 (31 July 1934). H. Noureddini, W.R. Dailey and B.A. Hunt, Production of ethers of glycerol from crude glycerol. The byproduct of biodiesel production, Adv. Environm. Res. 2 (1998) 232–43. SAE International, Advanced Diesel Engines and Liquid Alternative Fuels, SAE, Warrendale, PA (June 2003). H. Noureddini (to Board of Regents of University of Nebraska), Process for producing biodiesel fuel with reduced viscosity and a cloud point below thirtytwo degrees Fahrenheit, US Pat. 6,015,440 (18 Jan. 2000). H. Noureddini (to Board of Regents of University of Nebraska), System and process for producing biodiesel fuel with reduced viscosity and a cloud point below thirty-two (32) degrees Fahrenheit, US Pat. 6,174,501 (16 Jan. 2001). V.P. Gupta (to Arco Chem. Technol.), Glycerine ditertiary butyl ether preparation, US Pat. 5,476,971 (19 Dec. 1995). D.S. Bradin (to BRI), Biodiesel fuel, US Pat. 5,578,090 (26 Nov. 1996). Institut Français du Petrole (FR), Procédé de fabrication d’esters à partir d’huiles vegetables ou animales et d’alcools, Fr. Pat. 2,752,242 (13 Feb. 1998). W.A. Summers, An effective solution to the glycerin glut, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). J. Barrault, J.-M. Clacens and Y. Pouilloux, Selective oligomerization of glycerol over mesoporous catalysts, Topics Catal. 27 (2004) 137–42. Ullmann’s Encyclopedia of Industrial Chemistry, 5th edn (H.J. Arpen, ed.), WileyVCH, Weinheim, Vol. A9 (1987), pp. 539–40. P. Gilbeau (to Solvay), Catalytic chlorination method for making a chlorohydrin

622

[132]

[133]

[134]

[135]

[136]

[137]

[138]

[139]

[140]

[141] [142]

[143]

[144]

[145]

[146]

Biodiesel science and technology from a polyhydric alcohol or polyhydric alcohol esters, PCT Int. Publ. No. WO 2006/106154 A1 (12 Oct. 2006). P. Krafft, P. Gilbeau, D. Balthasart and V. Smets (to Solvay), Catalytic chlorination method for making a chlorohydrin from a polyhydric alcohol or polyhydric alcohol esters, PCT Int. Publ. No. WO 2006/100313 A2 (28 Sept. 2006). P. Krafft, P. Gilbeau, B. Gosselin and S. Claessens (to Solvay), Process for producing dichloropropanol from glycerol coming from the conversion of animal fats in the manufacture of biodiesel, PCT Int. Publ. No. WO 2005/054167 A1 (16 June 2005). P. Krafft (to Solvay), Chlorination method for making a chlorohydrin from an aliphatic polyhydric alcohol, PCT Int. Publ. No. WO 2006/106153 A2 (12 Oct. 2006). P. Krafft, P. Gilbeau, D. Balthasart and V. Smets (to Solvay), Chorination method for making a chlorohydrin from an aliphatic polyhydric alcohol, PCT Int. Publ. No. WO 2006/100314 A1 (28 Sept. 2006). P. Krafft and P. Gilbeau (to Solvay), Method for preparing chlorohydrins by the catalytic chlorination of polyhydric alcohols, PCT Int. Publ. No. WO 2006/100319 A1 (28 Sept. 2006). P. Gilbeau, I. De Andolenko, P. Krafft and F. Gielen (to Solvay), Process for producing a chlorohydrin from a polyhydric alcohol and a chlorinating agent, PCT Int. Publ. No. WO 2006/100312 A2 (28 Sept. 2006). P. Krafft, D. Balthasart, V. Smets and P. Gilbeau (to Solvay), Method for making an epoxide starting from a chlorohydrin, PCT Int. Publ. No. WO 2006/106155 A2 (12 Oct. 2006). P. Krafft, P. Gilbeau, D. Balthasart and V. Smets (to Solvay), Method for making an epoxide starting with a polyhydroxylated aliphatic hydrocarbon and chlorinating agent, PCT Int. Publ. No. WO 2006/100318 A2 (28 Sept. 2006). P. Krafft, P. Gilbeau, B. Gosselin and S. Claessens (to Solvay), Use of renewable resources for manufacture of chlorinated organic compounds, Fr. Pat. Appl. 2,862,644 A1 (27 May 2005). V. Plasman, T. Caulier and N. Boulos, Polyglycerol esters demonstrate superior antifogging properties for films, Plast. Addit. Compd. 7(2) (2005) 30–3. M. Aresta, A. Dibenedetto, F. Nocito and C. Pastore, A study on the carboxylation of glycerol to glycerol carbonate with carbon dioxide: the role of the catalyst, solvent and reaction conditions, J. Mol. Catal. A 257 (2006) 149–53. Z. Mouloungui, J.-W. Yoo, C.-A. Gachen, A. Gaset and G. Vermeersch (to Organisation Nationale Interprofessionelle des Oléagineux – O.N.I.D. Ol), Procédé de fabrication de carbonate de glycérol à partir de glycérol et d’un carbonate organique cyclique, en particulier carbonate d’éthylène ou de propylène, Eur. Pat. EP 0,739,888 A1 (22 Apr. 1996). C. Vieville, J.W. Yoo, S. Pelet and Z. Mouloungui, Synthesis of glycerol carbonate by direct carbonatation of glycerol in supercritical CO2 in the presence of zeolites and ion exchange, Catal. Lett. 56 (1998) 245–7. J.-W. Yoo, Z. Mouloungui and A. Gaset (to Organisation Nationale Interprofessionnelle des Oléagineux – O.N.I.D. Ol), Method for producing an epoxide, in particular of glycidol, and installation for implementation, PCT Int. Publ. No. WO 98/40371 (17 Sept. 1998). Z. Chi, D. Pyle, Z. Wen, C. Frear and S. Chen, A laboratory study of producing docasahexaenoic acid from biodiesel-waste glycerol by microalgal fermentation, Process Biochem. 42 (2007) 1537–45.

Valorisation of the glycerol by-product

623

[ 147] Z. Wen, unpublished results (2009). [148] A. Murarka, Y. Dharmadi, S.S. Yazdani and R. Gonzalez, Fermentative utilization of glycerol by Escherichia coli and its implications for the production of fuels and chemicals, Appl. Environm. Microbiol. 74 (2008) 1124–35. [148a] H. Abe, unpublished results (2009). [149] W. Charney (to Schering Co.), Process for the production of dihydroxyacetone, US Pat. 4,076,589 (28 Feb. 1978). [150] G.D. Boyd, M.R. Martino and C.T. Nomura, Bacterial production of biodegradable plastics from biodiesel process waste glycerol, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [151] J. Chowdhury and K. Fouhy, Vegetable oils: from table to gas tank, Chem. Engng. 100(2) (1993) 35, 37, 39. [152] R. Gonzalez, Anaerobic fermentation of glycerol, PCT Int. Publ. No. WO 2007/115228 A2 (11 Oct. 2007). [153] H. Biebl, A.-P. Zeng, K. Menzel and W.-D. Deckwer, Fermentation of glycerol to 1,3-propanediol and 2,3-butanediol by Klebsiella pneumoniae, Appl. Microbiol. Biotechnol. 50 (1998) 453–7. [154] H. Biebl, K. Menzel, A.-P. Zeng, and W.-D. Deckwer, Microbial production of 1,3-propanediol, Appl. Microbiol. Biotechnol. 52 (1999) 289–96. [155] M.M. Zhu, P.D. Lawman and D.C. Cameron, Improving 1,3-propanediol production from glycerol in a metabolically engineered E. coli by reducing accumulation of glycerol-3-phosphate, Biotechnol. Progr. 18 (2002) 694–9. [156] S. Hirschmann, K. Baganz, I. Koschik and K.-D. Vorlop, Development of an integrated bioconversion process for the production of 1,3-propanediol from raw glycerol waters. Landbauforschung Voelkenrode 55 (2005) 261–7. [157] A.-P. Zeng, H. Biebl and W.-D. Deckwer, Microbial conversion of glycerol to 1,3-propanediol, Abstr. 211th ACS Natl. Mtg., New Orleans, LA (24–28 Mar. 1996), BTEC-021. [158] P.J. Slininger, R.J. Bothast and K.L. Smiley, Production of 3-hydroxypropionaldehyde from glycerol, App. Environm. Microbiol. 46 (1983) 62–7. [159] Y. Mu, H. Teng, D.-J. Zhang, W. Wang and Z.-L. Xiu, Microbial production of 1,3-propanediol by Klebsiella pneumoniae using crude glycerol from biodiesel preparations, Biotechnol. Lett. 28 (2006) 1755–9. [160] H. Streekstra, M.J. Teixeira de Mattos, O.M. Neijssel and D.W. Tempest, Overflow metabolism during anaerobic growth of Klebsiella aerogenes NCTC 418 on glycerol and dihydroxyacetone in chemostat culture, Arch. Microbiol. 147 (1987) 268–75. [161] B.O. Solomon, A.P. Zeng, H. Biebl, A. Okechukwu Ejiofor, C. Posten and W.-D. Deckwer, Effects of substrate limitation on product distribution and H2/CO2 ratio in Klebsiella pneumoniae during anaerobic fermentation of glycerol, App. Microbiol. Biotechnol. 42 (1994) 222–6. [162] A.P. Zeng, H. Biebl, H. Schlieker and W.-D. Deckwer, Pathway analysis of glycerol fermentation by Klebsiella pneumoniae: regulation of reducing equivalent balance and product formation, Enzyme Microb. Technol. 15 (1993) 770–9. [163] T. Homann, C. Tag, H. Biebl, W.-D. Deckwer and B. Schink, Fermentation of glycerol to 1,3-propanediol by Klebsiella and Citrobacter strains, Appl. Microbiol. Biotechnol. 33 (1990) 121–6. [164] R. Boenigk, S. Bowien and G. Gottschalk, Fermentation of glycerol to 1,3propanediol in continuous cultures of Citrobacter freundii, Appl. Microbiol. Biotechnol. 38 (1993) 453–70.

624

Biodiesel science and technology

[165] M. Gonzalez-Pajuelo, J.C. Andrade and I. Vasconcelos, Production of 1,3propanediol by Clostridium butyricum VPI 3266 using a synthetic medium and raw glycerol, J. Industr. Microbiol. Biotechnol. 31 (2004) 442–6. [166] B. Günzel, S. Yonsel and W.-D. Deckwer, Fermentation production of 1,3propanediol from glycerol by Clostridium butyricum up to a scale of 2 m3, Appl. Microbiol. Biotechnol. 36 (1991) 289–94. [167] S. Abbad-Andaloussi, C. Durr, G. Raval and H. Petitdemange, Carbon and electron flow in Clostridium butyricum grown in chemostat culture on glycerol and on glucose, Microbiol. 142 (1996) 1149–58. [168] C.W. Forsberg, Production of 1,3-propanediol from glycerol by Clostridium acetobutylicum and other Clostridium species, Appl. Environm. Microbiol. 53 (1987) 639–43. [169] F. Barbirato, A. Bories, C. Camarasa-Claret and J.P. Grivet, Glycerol fermentation by a new 1,3-propanediol-producing microorganism: Enterobacter agglomerans, Appl. Microbiol. Biotechnol. 43 (1995) 786–93. [170] T. Wilke, U. Prüße and K.-D. Vorlop, Biocatalytic and catalytic routes for the production of bulk and fine chemicals from renewable resources, in Biorefineries – Industrial Processes and Products, Vol. 1 (B. Kamm, P.R. Gruber and M. Kamm, eds), Wiley-VCH, Weinheim (2006), pp. 385–407. [171] S. Liu, M. Rebros, G. Stephens and A.C. Marr, Adding value to renewables: a one pot process combining microbial cells and hydrogen transfer catalysis to utilise waste glycerol from biodiesel production, Chem. Commun. (2009) 2308–10. [172] P.G. Selembo, B.E. Logan and J.M. Perez, Glycol – electricity and hydrogen generation via microbial fuel cells, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [173] S.D. Minteer, B.Y. Liaw and M.J. Cooney, Enzyme-based biofuel cells, Curr. Opin. Biotechnol. 18 (2007) 228–34. [174] R.L. Arechederra and S.D. Minteer, Using glycerol as fuel in biofuel cells, Abstr. 233rd ACS Natl. Mtg., Chicago, IL (25–29 Mar. 2007), FUEL-074. [175] W. Du, Y. Xu, D. Liu and J. Zeng, Comparative study on lipase-catalyzed transformation of soybean oil for biodiesel production with different acyl acceptors, J. Mol. Catal. B: Enzym. 30 (2004) 125–9. [176] S. Saka and Y. Isayama, Biodiesel production without producing glycerol from oils/fats with using supercritical carboxylate esters, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [177] R. Muskett and C.A. Anderson (to Biodiesel Australia), Method for production of alkyl esters, PCT Int. Publ. No. WO 2004/048311 A1 (10 June 2004). [178] W. Iijima, Y. Kobayashi and K. Taniwaki, Process for non-catalytically producing biodiesel fuel without yielding by-product, PCT Int. Publ. No. WO 2005/017075 (24 Feb. 2005); US Pat. Appl. 2006/288636 A1 (28 Dec. 2006). [179] M. Matsumura and S. Murakami, Method and equipment of refining plant oil and waste vegetable oil into diesel engine fuel, US Pat. 6,364,917 B1 (2 Apr. 2002). [180] N.U. Soriano, V.P. Migo and M. Matsumura, Ozonation of sunflower oil: spectroscopic monitoring of the degree of unsaturation, J. Am. Oil Chem. Soc. 80 (2003) 997–1001. [181] R. Alcantara, J. Amores, L. Canoira, E. Fidalgo, M.J. Franco and A. Navarro, Catalytic production of biodiesel from soybean oil, used frying oil and tallow, Biomass Bioen. 18 (2000) 515–27.

14

Sustainability and use of biodiesel

Abstract: One of the energy policy goals is production and use of sustainable biodiesel. There is no general consensus on the use of an important analytical tool (life cycle assessment) as to inclusion of the effects of land use (change). Biodiesel fuel properties were evaluated in comparison to petrodiesel, in particular as to operability in terms of coldtemperature performance, storage stability and engine exhaust emissions. Not all biodiesel fuels are created equal. Biodiesel economics have been evaluated in particular in relation to feedstock and manufacturing costs and competitiveness. Biodiesel use and market prospects were detailed critically for the EU, the US and emerging economies (BRIC, South-East Asia, Argentina). Key words: Sustainable biodiesel, life cycle assessment, performance characteristics, biodiesel cost structure, biodiesel use and global markets.

14.1

Introduction

The present level of global energy consumption, production and industrial growth is not sustainable because fossil carbon is finite and not renewable. Developing a sustainable bio-based economy that uses eco-efficient bioprocesses and renewable bioresources is one of the key strategic challenges for the 21st century. The life sciences, and in particular biotechnology, will play a prominent role in meeting that challenge by: ∑

selecting and developing value-added crop and tree varieties for conventional and industrial applications; ∑ high-yield, sustainable crop and tree production; and ∑ sustainable utilisation of the resulting products.

The chemical industry offers various opportunities for the application of vegetable oils, both as substitute petrochemical products and as replacement of fossil crude oil. Although at first glance only positive environmental effects are expected from their industrial use because they are CO2 neutral (Fig. 14.1), biodegradable, and save finite resources, these advantages do not necessarily persist after considering the entire product life cycle leading to vegetable oils and biodiesel (esters), including the agricultural production of oilseeds, pressing and refinement to oil, conversion to ester, all transports, energetic use, disposal, etc. As one of the biofuels policy goals is a sustainable production and use of bioenergy crops, all potential feedstocks need to be 625

626

Biodiesel science and technology Sun

Water

Plant

CO2

Carbohydrates

O2

Man CO2

14.1 Simplified life cycle.

assessed for their effectiveness to achieve this goal, and this assessment is to be made part of the sustainability standards for bioenergy feedstock crops. At present, biodiesel is a niche rather than a mainstream energy source, which can hardly be considered a serious competitor to petrodiesel because of the different order of magnitude of the two outputs with volume ratios of 100 : 1 in favour of the petrochemical industry. Even in the distant future biodiesel cannot be expected to represent a mainstream energy source, because of the limited amount of fatty material available worldwide. At most, biodiesel can possibly replace a maximum of 15% of mineral fuel, but not until 10–15 years from now. Sustainable development of biodiesel for transportation, i.e. development that meets the needs of the present without compromising the ability of future generations to meet their own needs, also requires consideration of alternative use of biomass for electricity and heat generation, as well as for chemistry and industry. No single process or product can be sustainable in isolation. Industry is sustainable when it is economically viable, environmentally compatible and socially responsible. Issues surrounding sustainability thus comprise corporate social responsibility, new certification requirements, wildlife conservation, life cycle analysis and carbon balance, amongst other topics. In the biodiesel business, sustainability is related to fuel quality, feedstock diversification and production efficiency. The Sustainable Biodiesel Alliance (SBA) focuses on the environmental, social and economic sustainability issues facing the US biodiesel industry. The SBA emphasises the local model, i.e. local feedstocks, local production and localised distribution of sustainably produced fuel. The National Biodiesel Board (NBB) have developed guiding principles for biodiesel sustainability (see www.biodieselsustainability. com).

Sustainability and use of biodiesel

14.2

627

Energy balance

The energy balance debate revolves around whether a biofuel that requires some fossil fuel energy for its production can be defined as a renewable fuel. The extent to which a fuel is renewable is frequently expressed by an energy ratio. The concept of biodiesel energy balance is controversial and varies with the definition of the energy ratio [1]. For example, for soy biodiesel various (non-comparable) positive energy ratios (input vs. output) of 1 : 3.24 [2], 1 : 1 [3], 1 : 1.5 [4], 1 : 1.1 [5] and 1 : 3.9 [6] have been reported, compared with 1 : 1.34 for corn ethanol. If recycled oils are used, the energy balance is even more positive. Instead of accounting only for the non-renewable energy input, ratios are also reported that compare the total energy that went into producing a unit of biofuel with the energy content of that fuel unit. For biodiesel, the (total) energy ratio does not differ much from the renewable ratio. The total energy input is close to the non-renewable energy input. It should be considered that only a fraction of all the energy used in farming and oil crushing goes into biodiesel production because glycerol and oilseed meal are also obtained. Consequently, biodiesel is to be held accountable for only a fraction of the total energy input when assessing its energy balance. The biodiesel industry needs to establish and adopt a standard definition of energy balance. The energy ratio of a biofuel is commonly defined as the ratio of the nonrenewable energy used in its production to the energy value of the fuel and any utilised by-product, i.e. energy input vs. energy output. This index greatly depends on local climatic conditions, agronomic and production technologies. Figure 14.2 [7] shows the primary energy and mass flows of a basic biofuel system. One of the main requirements for renewable fuels is that the value of the energy efficiency index evaluated by means of life cycle assessment (EN ISO 14040-43) should exceed unity [8]. To be a viable alternative to conventional fuels, biodiesel should provide a net energy gain. Batchelor et al. [9] have described the energy analysis of rape methyl ester (RME) production from winter oilseed rape in crop management conditions typical to Scottish agriculture varying crop yield (from 2.8 t/ha for poor yield to 3.5 t/ha for a typical rapeseed yield, and 4.2 t/ha for a good yield) and energy efficiency scenarios. Fossil energy-requiring processes for oilseed rape production are: ∑

direct on-farm energy inputs (e.g. ploughing, discing, harrowing, sowing, rolling, fertiliser and pesticide application, swathing, combining the crop and grain drying); ∑ indirect on-farm energy inputs (e.g. manufacture of tractor, field equipment, grain-drier, fertilisers and pesticides); and ∑ processing to RME (transport, crushing to oil, refining and esterification).

628

Biodiesel science and technology Non-fuel co-products

Process system

Feedstock

Energy inputs

Fuel product

Fuel co-products

14.2 Biodiesel process system mass and energy flows (after ref. [7]).

Table 14.1 Energy ratios for rape methyl ester production from winter rape for various scenariosa (after ref. [9]) Energy ratiob

Outputs includedc

Scenario (I)

Scenario (II)

Scenario (III)

Scenario (IV)

1 2 3 4

1:2.23 1:3.83 1:3.95 1:9.18

1:1.58 1:2.22 1:2.30 1:5.46

1:1.12 1:1.60 1:1.65 1:3.92

1:0.67 1:0.88 1:0.91 1:2.22

a

Scenarios: best case (I), good intermediate (II), poor intermediate (III), worst case (IV). b Energy input/energy output. c 1 = RME only; 2 = RME + rapemeal; 3 = RME + rapemeal + glycerol; 4 = RME + rapemeal + glycerol + residual biomass (straw).

In the analysis the amount of methanol required for esterification of 1 t of refined oil was assumed to vary from 0.0958 to 0.124 t. The vast majority of energy used in RME production is consumed during crop growing rather than RME processing. The input from N fertiliser varies from 10% to 43.5% in the best- and worst-case scenarios (very low crop yields, very high inputs, energy-inefficient production), respectively. This eventually calls for modification of agricultural practice. The use of fuel and machinery for field operations is another large energy consumer in the production of RME. The quantity of RME obtained from the esterification of 1 t of refined rape oil was taken to vary from 941 to 1003 kg of RME. Utilisable by-products are rapemeal, glycerol and straw. Rapemeal is currently used as an animal feed but could potentially be used as a solid fuel. The yield of straw per tonne of seed varies from 1.84 t to 2.00 t straw/t seed. As shown in Table 14.1, RME production is sustainable. In practice, the energy ratios are likely to fall within the range of the two intermediate values. In this respect, rapeseed grown in Lithuania does not score highly in terms of the energy efficiency index and thus eventually does not qualify as

Sustainability and use of biodiesel

629

a renewable energy resource [10]. Where no by-product use is accounted for, the energy balance is positive except for the worst conditions. Utilisation of by-products is an important factor in the energy efficiency and economies of RME production. Utilisation of rapemeal greatly improves the energy ratio, but there remains a net loss in energy under the worst-case scenario (see Table 14.1). As expected on the basis of its poor calorific value, glycerol has little effect on the energy ratio. Addition of the gross energy content of rape straw greatly increases the energy ratio for RME production. The energy gained from the use of straw as a fuel will vary depending on the method of conversion. At the moment, the use of rape straw as a fuel is still limited. Failure to utilise glycerol as a by-product of RME production could result in lower glycerol and higher RME prices, but would not greatly affect the energy ratio or therefore the sustainability of the fuel. On the other hand, failure to utilise rapemeal would, however, affect the energy ratio. If the price of rapemeal were to drop, it may become competitive with other forms of biomass as a fuel for heat and power generation. As illustrated in Table 14.2, various other studies all report a positive energy balance for various biodiesel fuels (rape, soy and recycled frying oil methyl esters, RFO-ME). Biodiesel provides a highly positive energy balance: for every unit of energy needed to produce (soybean) biodiesel, up to 4.56 units of energy are gained. Virgin oil from other sources may have an even higher energy content. The energy efficiency of the agricultural and industrial production process of curcas oil methyl ester is between 1 : 3.75 and 1 : 5. Algae can yield substantially higher energy balances. In comparison to biodiesel fuels from other sources, the energy ratio of RFO-ME is positively Table 14.2 Selection of results of energy balances for various biodiesel fuels and fossil diesel fuel Fuel type RME RME RME RME RME RME RME RME SBME RFO-ME Bioethanol DF DF Petrogasoline a

Study applicable to Switzerland Europe Scotland Germany Germany Germany Germany UK USA Germany USA Germany USA USA

Energy balancea b

1 : 1.88 1 : 3.0 1 : 3.92–5.46 1 : 2.6 1 : 2.3 1 : 4.3 1 : 2.28–2.96 1 : 2.29 1 : 3.21–4.56 1 : 5.51b 1 : 1.34 1 : 0.90 1 : 0.84 1 : 0.805

Reference(s) [11] [12] [9] [13] [14] [15] [16] [17] [2, 18, 18a] [19] [20] [13] [18, 20] [20]

Input : output relationship. Coupled products are not considered in favour of biodiesel in the calculations.

b

630

Biodiesel science and technology

affected as no fertiliser manufacture, cultivation, harvesting and oil recovery need to be considered for this waste product; input of fossil energy is therefore limited to the production of methanol used for transesterification (the logistics for waste collection should also have been included). Sunflower cultivation has the advantage of requiring lower nitrogen fertiliser amounts than rapeseed. The net energy balance estimates for coconut methyl ester (CNME) are significantly higher than those reported for other biodiesels, namely approximately 36 MJ kg–1, which greatly exceeds the 28 MJ kg–1 net energy typical of RME relevant to UK conditions [7, 21]. Two main factors account for this disparity. In contrast to the highly energy-intensive agricultural practices used for soybean, canola and rapeseed, coconut plantations in the Philippines generally do not use fertilisers and other energy-intensive inputs such as farm machinery but traditionally rely on human labour and animal power. Moreover, energy requirements for coconut oil pressing and transesterification are easily met by the large quantities of agricultural residues generated. This results in a highly favourable energy ratio for coconut methyl ester. Although there are claims that oil palm leads many other crops in terms of energy balance [22], this has recently been put in sharper perspective [1]. The energy ratios for rape and soy biodiesel are more favourable than those calculated for bioethanol under similar assumptions [20, 23]. Where no by-product use is taken into account, a net loss in energy resulting from the production of bioethanol from wheat was indicated under all scenarios considered. Addition of the gross energy of wheat straw to the output energy improves the energy ratio to at most only 1 : 1.79. Fossil diesel fuel shows a negative energy balance as up to 20% of the energy contained is used for fuel production (exploration, refining and transport) [18, 20]. It is important to realise that a fuel balance is greatly dependent on transport, e.g. of oilseeds to a refinery, thus favouring local production and use. In actual practice, however, in recent years fuel balances have been greatly (negatively) distorted as a result of ‘splash-and-dash’ practices involving massive transports of biodiesel around the globe merely in order to cash subsidies. The energy analysis for conventional biofuels from agricultural production sustains biomass-to-liquids (BTL) as the most promising route to liquid biofuels production with an overall higher fuel rate. BTL biofuel processing will make biodiesel production from edible oils less attractive.

14.3

Life cycle assessment of biodiesel

The life cycle evaluation programme is a method to determine and compare the environmental aspects and potential impacts associated with alternative

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products or processes, considering the relevant energy and materials inputs and releases, from the initial resource extraction to waste disposal. Life cycle analysis of chemicals not only allows evaluation of the contribution to energy efficiency on the basis of energy consumption during production but also helps end-users to conserve energy during their lifetime and final disposal. The energy and environmental balance (GHG (greenhouse gas) emissions) of biofuels is greatly influenced by agricultural techniques, the yield of cultivation of raw material, pre-treatment of the feedstock, technological transformation processes and utilisation. Figure 14.3 shows the biodiesel life cycle. At first glance, the life cycle of biogenic fuel appears to be neutral with respect to CO2 release. In fact, the CO2 released has already been assimilated from the atmosphere during plant growth. In contrast to fossil fuels, biogenic fuels thus neither contribute to the accumulation of CO2 in the atmosphere nor to global warming. Biodiesel fits potentially into a lowcarbon economy. Life cycle assessment (LCA, or ecobalance) is an efficient means of comparing the ecological impact in terms of advantages and disadvantages of energy sources ‘from cradle to grave’. Despite standardisation (DIN EN ISO 14040 ff norms) [24], consistent direct comparison of LCAs is very difficult because of variations in impact categories, assumptions (e.g. hectare yields) and balancing methods. In particular, the LCA community (e.g. EPA vs. CARB) is yet to come to a consensus on a methodology to incorporate indirect land use in LCA and life cycle carbon emission [25]. Land use and land use change are significant aspects of global change, which may induce climate change, desertification and loss of biodiversity and life support functions. A further major source for divergent results is the approaches to account for coupled products created during the life cycle, which can substitute for Food/feed/fibre/ oleochemical products

Solar energy Crop refining

Renewable resource

Feed products Biodiesel production Glycerin products

CO2 Transportation

14.3 Biodiesel life cycle.

Renewable fuel

632

Biodiesel science and technology

products from other sources. For example, in case of biodiesel, glycerol from transesterification can replace synthetic glycerol, rapeseed meal can substitute imported soybean meal as fodder, etc. LCAs are best subjected to various sensitivity analyses; social and economic aspects are usually not considered. Life cycle assessment allows a detailed evaluation of the ecological performance of vegetable oils in the production of biodiesel. Production of oilseed involves energy investment and causes emissions. When the whole life cycle of biodiesel from production of the biomass via conversion to use as an energy source is analysed, CO2 neutrality of biodiesel can be challenged [26]. In fact, converting carbon-rich ecosystems to biofuel production results in large amounts of CO2 being released for decades following land clearing (so-called ‘carbon debts’) [27, 28]. Greenhouse gas emissions depend on the type of lands converted (rainforests, peatlands, savannahs, or grasslands). Conversely only biofuels from perennials grown on degraded or abandoned cropland and from waste biomass avoid land-use change, minimise habitat destruction, competition with food production, and carbon debts, and can offer immediate and sustained GHG advantages [29]. Algae grown in deserts or feedstocks produced on carbon-poor lands might also keep land-use change emissions low, but the ability to produce biodiesel feedstocks abundantly on unproductive lands remains questionable. As to N2O (nitrous oxide), which arises from fertiliser production and agricultural ecosystems, it is not liberated in significant amounts in the production of fossil fuels. Assessment of the production cycle of biodiesel based on canola oil, SBO, waste vegetable oils (WVO) and animal fats – starting from oilseed crop growth (not including land-use change) via conversion to VO and oilseed meal to biodiesel/glycerol production – has indicated that nitrous oxide emission from soils during crop growth is the largest GHG emission factor [30]. Total GHG emissions for different biodiesel sources decreased by 8% for animal fat to 37% for SBO with respect to fossil diesel fuel (on an equivalent energy basis). The coconut biodiesel life cycle system is shown in Fig. 14.4. There is more than enough agricultural residue in the form of coconut husk and shell to meet both thermal energy and electricity requirements of coconut biodiesel processing. The biofuel cycle thus exhibits a high degree of potential selfsufficiency, with only the methanol input and transportation energy being dependent on external fossil fuel supply. Many life cycle analyses of RSO and RME have been reported [31–33]. Figure 14.5 shows a schematic life cycle comparison of RME and fossil diesel fuel. On the basis of life cycle analyses, the Institute for Energy and Environmental Research (IFEU), Heidelberg, considers that all biodiesel fuels possess positive energy and climate gas balances, i.e., all biodiesel fuels preserve fossil energy sources compared with conventional diesel regardless of the source of the vegetable oils and help to avoid greenhouse gases [26].

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Net carbon dioxide emissions

Coconut plantation Copra + residues Residues

Transport of copra and residues

Diesel

Diesel system

Petroleum

Copra Co-generation plant Excess power

Heat Power

Glycerol Copra cake

Coconut methyl ester plant Biodiesel Transport of coconut biodiesel

Methanol

Methanol system

Natural gas

Biodiesel Co-products

End-user

System boundary

14.4 Coconut biodiesel system (after ref. [21]).

The savings effect (from well-to-wheels) is greatest for biodiesel from rape and sunflower, followed by canola, and lowest for coconut and soybean, waste oils or animal fats. LCA takes into account various impact categories, such as resource demand, greenhouse effect, ozone depletion, acidification, eutrophication, human and eco toxicity, photosmog, etc. However, as noted above, the use of land resulting from the cultivation of oil crops needs careful consideration (e.g. promotion of fallow oil plant cultures in Europe, deforestation of tropical rainforests for palm tree plantations in South-East Asia and soy-related deforestation in the Amazon). In Austria and Germany oilseed rape for energy use is currently only grown on set-aside fields in rotation. Biodiesel from palm oil must be discussed in the context of tropical rainforest clearance [34]. Indeed, some LCAs of palm oil-based biofuel are flawed because they overlook some crucial factors and indirect impacts, such as destruction of peatlands and rainforests, as well as the so-called ‘leakage effects’, whereby farmers, displaced from their lands by palm oil companies, turn natural forests into crop lands [35]. Biodiesel has both advantages and disadvantages compared with fossil diesel fuel. Advantages are the preservation of non-renewable fossil resources and the

634

Biodiesel science and technology Fossil fuel

Biodiesel

Credits

On-farm input Exploration

Raw material production

Agriculture

Transport pipeline/overseas Refinery

Fallow maintenance

Regional transport Conversion

Rapeseed processing Rapeseed meal

Soybean meal

Soybean oil

Rapeseed oil Transesterification

Diesel fuel

End product

Technical glycerol

RME

Synthetic glycerol

Blending Final distribution Combustion in vehicle

Utilisation

Final distribution Combustion in vehicle

Processes

Materials

Substitutions

14.5 Schematic life cycle comparison of RME and fossil diesel fuel.

potentially diminished greenhouse effect; the main ecological disadvantages are eutrophication and acidification. In particular, Table 14.3 [36] shows that life cycle comparison of the demand of finite energy and global warming potential (with high ecological relevance) is in favour of RME as compared to petrodiesel fuel, whereas acidification and eutrophication potential (both of medium ecological relevance) are unfavourable for RME. The overall assessment of environmental impacts according to Table 14.3 is considered to be in favour of RME [37]. The environmental impact of biodiesel for transportation does not easily allow assessment of a total balance (Table 14.4). The prime ecological advantage of biodiesel is its net energy yield, whereas the main ecological disadvantage is the impact of energy crop farming [38]. An objective decision for or against a particular fuel cannot be made. A decision requires a subjective

Sustainability and use of biodiesel

635

Table 14.3 Overall assessment of the results of life cycle analyses (after ref. [36]) Balanced category Parameter

General assessmenta

Ecological relevanceb

Demand of resources Global warming potential Acidification potential Eutrophication potential Stratospheric ozone depletion Tropospheric ozone formation   potential Toxicity/exotoxicity,   biodegradability

Energy CO2 equivalent SO2 equivalent PO4 equivalent NO NMHC

+ + – – – 0

High Very high Medium Medium High/Very high –

NOx, PM

+

Medium/High

a

+ advantage of RME over fossil DF; – disadvantage of RME over fossil DF; 0 similar assessment for RME and DF. b According to ref. [37]. Table 14.4 Total balance of biodiesel use for transportation Advantages

Disadvantages

∑ ∑ ∑ ∑

∑ ∑ ∑ ∑

CO2 neutral Saves fossil energy Organic waste reduction Less transport

Land use Acidification/eutrophication of surface waters Water pollution by pesticides Energy-intensive production

value system. If energy saving and greenhouse effect are given the highest priority, biofuels perform better than fossil fuels. On the other hand, fossil fuels do also have some positive environmental impacts compared with biodiesel (e.g. no N2O emissions). Rapeseed oil is the best biofuel from the point of view of all emissions considered, whereas the energy balance is one of the worst [32]. The conservation of finite energy and reduction in the emission of GHG is even higher if vegetable oils are used as a feedstock to produce oleochemical surfactants compared to their use as biofuels [39]. Because of competition for land and in the usage of biomass, the potential for energy crops is limited. If energy crops are used for biofuels, the biggest GHG savings are associated with high crop yields (notably sugar beet). Feedstock supply must be taken into account when assessing the potential of a biodiesel programme since net CO2 reduction benefits are obviously proportionate to the extent to which biodiesel displaces petrodiesel. The observed positive balance of RME is limited by the actual substitution potential of fossil diesel fuel by RME, which even in the medium term will amount to a few percent only [40]. Increases in RME production are impeded by the restricted acreage of cultivable areas and by the implications of international trade agreements, limiting the substitution of imported soybean meal by rapeseed meal. Similar observations can be made for other vegetable oils, such as coconut oil in the Philippines [21].

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Biodiesel science and technology

14.3.1 Environmental and macroeconomic implications Investment in biofuels has surged in recent years because of its attraction as a supposedly eco-friendly alternative to fossil fuels. However, sustainability criteria need to be built into the supply chains. Sustainability issues of biodiesel concern feedstock (continuity and security of supply), water resources, carbon release, working conditions, air emissions, waste handling, community benefit and quality. As the area of land required to grow biofuels is so great, this may easily lead to serious environmental problems (deforestation, water demand, biodiversity loss, toxicity of agricultural pesticides) and social impacts (reduced food supplies increasing commodity prices, civil unrest). The environmental impacts of biofuels can very easily exceed those of petrol and mineral diesel. Water demands could easily undermine alternatives to fossils fuels [41]. For example, water demand for bioethanol production is about twice that of gasoline production. Environmental impact is reduced by raw materials that are manufactured responsibly from renewable sources, are regionally produced or further improve the energy balance. EISA 2007 requires full feedstock certification back to origin (land, slaughterhouse or restaurant). Sustainable agriculture is environmentally sound land management and integration of environmental health, social responsibility and economic profitability. On the environmental front, sustainability comprises planned land management, environmental impact assessments, zero-burning replanting, integrated pest management, soil conservation, waste management, effluent treatment and oil mill waste recycling. Biodiesel production from energy crops could destroy natural habitats and push up food farming costs in some developing countries. Rapid expansion of agrofuel monocultures is speeding up the destruction of peat lands, tropical forest and other ecosystems. The reduction in GHG emissions that biodiesel causes should not be at the expense of an even larger increase due to deforestation, other land-use change, NO x emissions, and potentially the loss of major carbon sinks. Carbon sequestered by restoring forests might well be greater than the emissions avoided by the use of biofuels. Biodiesel is caught in an environmental dilemma: energy or climate. An OECD biofuels report has cast doubts on the CO2 benefits of biofuels and brings into focus the downside of higher food prices and loss of biodiversity. OECD forecasts predict food price rises of between 20% and 50% over the next decade, due to increasing affluence and population growth in developing countries (in particular China and India) and the effects of biofuel production (mainly in developed countries). At present, the biofuels boom is diverting corn, soy and palm oil to fuel use and driving up food/feed prices. Palm oil biodiesel gives best results in terms of energy savings and greenhouse effect for palm oil plantations on tropical fallow land but GHG balances can also be negative depending on the previous land use; disadvantages compared to fossil diesel fuel are acidification and

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eutrophication. As long as palm oil is not produced sustainably, palm oil should not be used for biodiesel [35]. An often ignored factor when considering costs and benefits of industrial feedstock materials is the macroeconomic effect associated with domestically produced renewable energy sources. To illustrate the interaction of environmental and economic implications of biodiesel commercialisation, the Philippines’ coconut biodiesel programme is of interest [7, 21]. This country generates some 1.3 Mt of coconut oil (mean annual production in the 1990s) with rather unproductive, traditional (low-energy intensive) agricultural practices. Utilisation of all available coconut resources for biodiesel production would be sufficient to substitute only roughly 8% of the diesel fuel requirement in the Philippines in 2010 and would reduce the projected 2010 combustion-related CO2 emissions by up to 3.85% per annum. Increased production of biodiesel needs improved agricultural productivity, the conversion of more land or forest into coconut plantations, or utilisation of alternative feedstocks such as waste grease (very limited availability). Higher rates of biodiesel production and substitution can be made possible through enhanced agricultural yields of coconut through improved irrigation, genetic engineering and other technological advances, or conversion of additional non-agricultural land into sustainable energy farms. However, such measures are likely to increase the CO2 emissions per unit of fuel product. On the other hand, the biodiesel programme helps to safeguard the Philippines from world price fluctuations and simultaneously revitalises stagnant sectors of the economy. These benefits may well be enough to compensate for a relatively high production cost of biodiesel. Implementation of carbon trading can also be employed to subsidise such a programme. Coconut biodiesel is likely to be best utilised either as a specialty fuel for niche markets, or as an additive for conventional diesel fuel. The production of biodiesel in Europe is practically waste-free (all by-products are used), as the meal produced in processing of rapeseed is displacing imported soy meal as a high-quality protein bearing fodder.

14.4

Performance characteristics for biodiesel

Fuel properties important for potential diesel applications include: lubricity, cetane number (CN), density, viscosity, heating value, sulphur, flash point, cloud point, distillation curve, carbon residue, ash and iodine value (IV). Lubricity affects the wear of pumps and injection systems. Cetane number rates the ignition quality of diesel fuels. Density, normally expressed as specific gravity, is defined as the ratio of the mass of a volume of the fuel to the mass of the same volume of water. Viscosity measures the fluid resistance to flow. Heating value is a measure of available energy in the fuel. Flash point is the lowest temperature at which a combustible mixture can be

638

Biodiesel science and technology

formed above the liquid fuel. Cloud point measures the first appearance of wax. Distillation curve is characterised by the initial temperature at which the first drop of liquid leaves the condenser and subsequent temperatures at each 10 vol% of the liquid. Carbon residue correlates with the amount of carbonaceous deposits in a combustion chamber. Ash refers to extraneous solids that result after combustion. Iodine value measures the number of double bonds. Biodiesel has several distinct advantages compared with petrodiesel in addition to being fully competitive with petrodiesel in most technical aspects (Table 14.5). The characteristics of biodiesel are close to diesel fuels. One of the main differences is that the esters contain 10–11 wt% oxygen. Biodiesel has lower volumetric heating values (about 12%) than diesel fuels but has a high cetane number and flash point. The esters have cloud and pour points that are 15–25 K higher than those of diesel fuels. Biodiesel fulfils the highest requirements of engine technology such as the modern high-pressure fuel injection systems. Biodiesel is described as ‘champaign for the engine’ [42]. Tables 14.6 and 14.7 show the benefits and technical challenges of biodiesel. Primary benefits are domestic production (not in all cases), increased lubricity, higher flash point and reduced emissions. Performance advantages of biodiesel compared to conventional diesel are limited. The conventional diesel engine can be operated with biodiesel without much modification to the engine [43]. B100 has higher kinetic viscosity than diesel, which improves injector efficiency. One of the most important characteristics of Table 14.5 Comparison of fuel properties between petrodiesel and biodiesel (B100) Fuel property

Diesel

Biodiesel

Fuel standard Fuel composition Lower heating value, Btu/gal Kin. viscosity, @ 313 K Specific gravity, kg/L @ 288 K Density, lb/gal @ 288 K Water, ppm by wt Carbon, wt% Hydrogen, wt% Oxygen, by dif. wt% Sulphur, wt% Boiling point, K Flash point, K Cloud point, K Pour point, K Cetane number Stoichiometric air/fuel ratio, wt/wt

ASTM D 975 C10-C21 HC 131 295 1.3–4.1 0.85 7.079 161 87 13 0 0.05 max 461–616 333–353 258–278 238–258 40–55 15

ASTM PS 121 C12-C22 FAME 117 093 1.9–6.0 0.88 7.328 500 max 77 12 11 0.0–0.0024 455–616 373–443 270–282 258–283 48–65 13.8

Sustainability and use of biodiesel

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Table 14.6 Ecological and economic benefits of biodiesel ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Decreasing reliance on petroleum derivatives (greater energy independence; improved trade balance) Favourable energy balance (1 : 3) Higher engine efficiency and durability Improvement of ignition, excellent lubrication capability, reduction of wear (HFRR ª 200) Recovery of co-product glycerol Ease of integration into existing infrastructures Technically feasible Compatible with any diesel engine Derived from any renewable, domestic lipid feedstock resource (sustainable development; ‘green’ fuel) New market opportunities for agro-business/agro-energy sector (use of agricultural surplus; energy crop production) Enhances rural revitalisation; job creation Reduced loss of waste oils (recycled materials as feedstock) Biodegradable in water, non-toxic, low mutagenic effects Environmental compatibility: decreased global warming impacts, reduced GHG emissions (CO, CO2, HC) and local air pollution Neutral global CO2 balance (emission vs. plant photosynthesis) Favourable combustion-emission profile (particulate emission: –15 to –50%; reduction of aromatics) Practically null sulphur content (< 0.001%) Safer handling and storage (flash point ~423 K vs. petroleum diesel ~343 K); non-inflammable Alternative fuel credits (CERs) and tax breaks No bacterial growth

Table 14.7 Technical challenges of biodiesel ∑ ∑ ∑ ∑ ∑ ∑

High pour, cloud and cold filter plugging points Slow low-temperature flow (remedy: use of additives) Slightly increased NOx emissions (except for CNO) Limited oxidation stability (feedstock dependent) Incomplete combustion Corrosion

diesel fuel is its ability to autoignite, as quantified by the cetane number (for biodiesel) or cetane index (for petrodiesel). The cetane number (CN) is generally dependent on the composition of the fuel and can impact the engine’s startability, noise level and exhaust emissions. The cetane number for biodiesel ranges from 45.8 to 56.9 for soybean oil methyl esters, with an average of 50.9 [44]; even higher values may be achieved by addition of ignition accelerators. Biodiesel blend stock typically has a higher minimum cetane level than that of petroleum diesel; the higher cetane number results in shorter ignition delay and longer combustion duration and hence, low particulate emissions. Its use results in minimisation of carbon deposits on

640

Biodiesel science and technology

injector nozzles. The higher flash point of biodiesel allows safer handling at higher temperatures than diesel. Biodiesel is a low-sulphur fuel. Soy biodiesel contains essentially no sulphur. The sulphur content of yellow grease biodiesel (24 ppm) exceeds the limits for ultra-low sulphur diesel (ULSD) (15 ppm). Lubricity is a measure of lubricating properties and another important characteristic of diesel fuel. Fuel injectors and some types of fuel pumps rely on fuel for lubrication. Diesel engines depend upon the fuel for lubrication. Biodiesel has better lubricity than low-sulphur petroleum diesel (500 ppm sulphur). The petrodiesel lubricity problem is even more severe for ultra-low-sulphur petroleum diesel (15 ppm sulphur) introduced in 2006. FAME restores the lubricity of petrodiesel even at the B1 to B2 level through an antiwear action on the engine injection system, making biodiesel extremely attractive as an additive. The use of other lubricity additives might eventually achieve the same effect at higher cost. US Patent No. 5,730,029 to Stoldt and Dave (to Lubrizol) [45] describes esters derived from genetically modified vegetable oils (CRO, CSO, PMO, RSO, SBO, SFO, SNO) with high monounsaturation content (preferably exceeding 80%, such as Sunyl 80“ and RS80) as lubricity enhancers of low-sulphur diesel oil. Biodiesel lubricity was recently reviewed by Schumacher [46]. Two very different applications may thus be envisaged for biodiesel: (i) as a renewable fuel added to diesel fuel (DF) (5% in winter or B5, up to 20% in summer), with the object of reducing air pollutants and GHG buildup; and (ii) as a lubricity improvement agent added to DF (<2%), with the object of improving fuel efficiency and reducing engine wear. Typically, 1% canola biodiesel improves Canadian diesel fuel efficiency by 5.8% and reduces engine wear by 51% [47] (see also Section 14.6.3). Table 14.7 shows that biodiesel also has some performance disadvantages. Material compatibility must be ensured when dealing with a diverse fuel infrastructure. The fuel properties of biodiesel are solvent-like and corrosive, which may cause unwanted liberation of residues or integrity issues with gaskets, metals, etc. High biodiesel contents (> 30%) may lead to softening and degradation of non-compatible polymeric materials, such as natural rubbers and polyurethane foams, in rings and seals. Binders used in cellulose (paper) filters, polypropylene and rubber materials are particularly vulnerable to B100. A remedy to wear-out of such packings is use of fluorine rubbers. Materials such as Teflon, Viton, fluorinated plastics and nylon are compatible with B100. In general, B2–B20 blends have no real issues with seals and gaskets but several metals, such as yellow metals, can give some problems. Brass, bronze, copper, lead, tin and zinc may accelerate in particular the oxidation of higher concentration biodiesel fuels and potentially create fuel insolubles (sediments) or gels and salts when combined with some fuel components. Although biodiesel is safe for use in underground steel storage tanks, the

Sustainability and use of biodiesel

641

fuel cannot be moved in the petroleum pipeline infrastructure. Heating oil systems are especially at risk without proper precautions. Although biodiesel is hydrophobic, repelling water, it can retain up to 20 times more water than regular diesel (1200 ppm compared to 60 ppm). Water removal is an arduous task. While biodiesel is biodegradable, in a poor environment it can also be one of biodiesel’s negative features [48]. In particular, introduction of water into biodiesel can create an environment for biological attack on the fuel itself. In fact, biodiesel and blend compositions are more susceptible to biological attack than regular diesel fuel. Consequently, removing water from a biodiesel system (to below 500 ppm) is important. A side effect of microbiological contamination is severe corrosion of the metal components of a fuel system (‘microbial influenced corrosion’). Another is filter plugging. For biodegradability and toxicity studies of biodiesel, see ref. [49]. An additional disadvantage of biodiesel is that it tends to reduce fuel economy. The energy content per volume unit of biodiesel (B100) is about 11% lower than that of petroleum diesel (see Table 14.5). This results from the higher oxygen content of the fuel. The lower energy content of biodiesel is partially offset by a 7% increase in combustion efficiency. Vehicles running on B5 are expected to achieve 0.55% (0.05 ¥ 11%) lower mileage per fuel volume.

14.4.1 Cold-temperature performance One of the major technical obstacles confronting the use of biodiesel is its poor low-temperature flow properties in comparison with fossil-based diesel fuel, as indicated by relatively high pour points and cloud points (see Table 14.5) [50]. There are two cold-temperature performance concerns: handling and operability. Handling refers to the ability to store, blend and pump B100 or the resulting biodiesel blend. Operability refers to the usage of the blended fuel in a vehicle or equipment. While biodiesel handling is typically of concern to the B100 producer or blender, operability falls in the realm of biodiesel blender, marketer and user. To enhance winter operability, heat is used to enable pumping. During winter months in colder climates, diesel fuel’s cold-flow properties are an operability issue. Operability means for equipment using the biodiesel (blend) to start and run without problems in a particular climate. Factors impacting biodiesel cold-temperature operability and handling are: ∑ type of feedstock; ∑ processing technique and resulting B100 purity; ∑ biodiesel blend level; ∑ cold-flow properties of the diesel fuel; and ∑ usage and type of cold-flow additives.

642

Biodiesel science and technology

Additives can be used to lower the pour point, either alone or in combination with heat. Commercial additives are available that will improve cold-weather performance of biodiesel and its blends. Different additive packages are effectively tailored to the specific biodiesel feedstocks. Operability levels of (bio)diesel are commonly expressed in terms of cloud point (CP), pour point (PP), and cold-filter plugging point (CFPP) or low-temperature flow test (LTFT) (which differs from CFPP in cooling rate and filter). With traditional diesel, operability concerns are quite well understood. Today, with well established additive treatments, operability issues have become increasingly rare. Biodiesel reaches cloud point (usually at a higher temperature than PP) at the start of crystal formation and solidification of saturated components during cooling. The wax that causes cold-flow concerns largely comes from saturated fatty acids, which are able to form highly regular crystalline structures easily – even at relatively high temperatures. Biodiesel typically clouds at temperatures between 269 and 289 K. Pour point is the minimum temperature at which a liquid pours, i.e. below which the fuel will no longer flow. Pour point occurs during further cooling below CP as a result of crystal growth and agglomeration involving not only the saturated, but also unsaturated components. The higher the proportion of saturated components therefore leads to higher CPs and PPs. The fuel becomes a gel that cannot be pumped. In comparison with fossil-based diesel there are some new challenges for biodiesel. The wax crystallisation temperature of biodiesel fuels is generally higher than that of fossil-based diesel fuel; formation of crystals at relatively high temperatures can plug fuel lines and filters, causing problems in fuel pumping and engine operation. Moreover, PP and CFPP can occur at much too high a temperature to meet specifications and winter requirements. During cooler weather, biodiesel ‘gels’ at temperatures near freezing (273 K) compared with 258 K for conventional diesel fuel. Depending on the nature of the vegetable oil from which the biodiesel is derived, it exhibits a pour point some 15–40 K higher than conventional diesel fuel. Viscosity, flash point, pour point and cloud point of saturated FAME increase linearly with increasing chain length (Table 14.8). In the presence of unsaturation, all these properties decrease. High amounts of saturated fatty acids (SFAs) in palm oil (PMO) lead to highly viscous palm oil methyl ester (PMME). Finally, traditional cold-flow additives are often not effective in biodiesel stocks. Biodiesel fuels are thus not all created equal when it comes to weather operability. Biodiesel low-temperature properties are affected by their chemical composition, which determines crystal growth. Methyl and ethyl esters of vegetable oils will crystallise in winter time operation. The presence of saturated FAMEs with significantly higher melting points than unsaturated fatty compounds increases the crystallisation temperature. Figure 14.6 shows that biodiesel with high levels of saturates (SFAs) has poorer

Sustainability and use of biodiesel

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Table 14.8 Effect of chain length on pour point, cloud point and viscosity of FAME (after ref. [51]) Physical property

Equationa,b

R2

Kinematic viscosity Dynamic viscosity Pour point Cloud point

y y y y

0.9913 0.9913 0.9936 0.9945

a

= = = =

0.50x–3.87 0.43x–3.31 5.7x–65.5 6x–67

Regression for saturated FAME only (C12 : 0–C18 : 0). x, carbon number of saturated FAME; y, physical property.

b

100 Better cold flow 80

m

PUFA (%)

Better stability

o n d

60

e p

40

r

l

i

20 g

f

a

q

0 0

20

h b

c

40

60 80 100 SFA (%) Key (a) beef tallow, (b) butterfat, (c) coconut, (d) corn, (e) cottonseed, (f) lard, (g) olive, (h) palm, (i) peanut, (l) rapeseed, (m) safflower, (n) soybean, (o) sunflower, (p) sesame, (q) moringa, (r) jatropha.

14.6 Effect of chemical composition of oils and fats on operability and handling of biodiesel (after ref. [52]).

cold-weather operability but better oxidative or storage stability. Biodiesel fuels derived from oils or fats with significant amounts of saturated fatty compounds will display higher CPs and PPs. Starting materials with a high proportion of medium- and long-chain saturated fatty acids, such as palm oil or tallow (TLW), are to be preferred for the ignition quality of biodiesel fuels; however, these same characteristics are disadvantageous in regard to viscosity and cold-temperature behaviour [53]. Biodiesel made from used

644

Biodiesel science and technology

cooking oil (UCO) or TLW is far less resistant to cold weather than biodiesel based on most virgin oils (problematic use of TLW B20 even in Californian winter). Base biodiesel fuels containing higher amounts of polyunsaturates (PUFAs), such as SBO and SNO, have better low-temperature operability but lack ignition quality and oxidation stability. In a NREL study [54], a variety of biodiesel/diesel blends were tested for a number of parameters, including CP and CFPP. Feedstocks that start out with a lower FFA level operated better at low temperatures. While the cold-weather performance of biodiesel is markedly worse than that of petroleum diesel, biodiesel made from yellow grease is worse than soy biodiesel in this respect. On the other hand, the lubricity and oxidative stability of the former are comparable or better than the latter [55]. Performance of soy biodiesel is a potential concern during winter in much of the US. In fact, quite recently biodiesel-powered schoolbuses in the Bloomington area of Minneapolis, MN, were stranded in freezing weather [56]. Biodiesel made from oils high in monounsaturates (olive, peanut, lard) provides good oxidative stability and reasonable cold-temperature performance. Rapeseed oil, with high MUFA and low SFA and PUFA contents, offers a desirable compromise regarding these properties. Table 14.9 reports coldflow properties for selected biodiesels. Linseed, olive and rapeseed oils give biodiesel with CP £ 273 K. At 7% saturated fat, canola has the lowest SFA level of all major vegetable oils. This implies improved cold-weather performance of canola biodiesel (CP, 270 K). On the other hand, soy biodiesel raises performance problems at temperatures below 273–275 K. It should be noted that oleic acid isomers with a double bond position differing from the natural position, i.e. 9(10), and the trans isomer (elaidic acid), have much higher melting points than oleic acid (Table 14.10); their presence might significantly compromise the cold-weather properties, which are very important for diesel fuels. Table 14.9 Cold-flow properties of selected vegetable oil and fat-derived biodiesel (FAME) compositions (adapted from refs [57, 58]) Oil or fat

CP (K)

PP (K)

Linseed 273 264 Olive 271 270 Palm 286 289 Rapeseed 271 264 Safflower 267 Soybean 273 271 Sunflower 275 270 Jatropha Tallow 290 288 Chicken fat 275.3 Palm-FAD 283.5

CFPP (K) 267 254–265 266–271 271 270–273 282 > 283

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Table 14.10 Influence of double bonds number, position and geometry on the melting points of C18 atom fatty acids (adapted from ref. [59]) Fatty acid

No. of double bonds

m.p. (K)

9,12,15 C18 : 3 9,12 C18 : 2 9 C18 : 1 C18 : 0

3 2 1 0

260 266 289 343

Monounsaturated fatty acids D6 D9 D12 D15

m.p. cis (K) 301 289 300 313

m.p. trans (K) 326 318 325 331

Probably the best way to improve the cold-temperature flow properties of biodiesel is to alter the fatty acid composition of the raw material. The key fatty acids limiting the cold-flow quality of biodiesel are palmitic (C16 : 0) and stearic (C18 : 0) acids. Polyunsaturated fatty acids (PUFAs) improve cold-flow properties but are most susceptible to oxidation. An optimum level of PUFA is desired, such as about 24% in SBO [60] (see Section 5.4.3). Jatropha-palm biodiesel blends are an optimum mix for Asia (see also Fig. 14.6) [61]. Various alternative strategies for the improvement of cold-temperature behaviour in biodiesel fuels have been suggested, including: ∑ blending with petrodiesel; ∑ transesterification with long- or branched-chain alcohols; ∑ addition of commercial cold-flow improvers (CFIs); and ∑ crystallisation fractionation (winterisation) [62, 63]. Blending FAME with fossil diesels is in principle straightforward, but does not pose engine compatibility problems, does not involve an extra processing step, and is relatively cheap (see Section 11.5). Admixed alkyl esters (such as SBME and TME) tend to exhibit cold-flow properties of the predominant alkyl ester in the mixture. Transesterification of oils and fats with medium (C3-C8)-chain alkyl alcohols improves cold-flow properties (CFP) of biodiesel [64]. Similarly, esters of fatty compounds obtained from branched alcohols have improved low-temperature properties compared to those derived from straight-chain alcohols [65]. Isopropyl soyate crystallises 7–11 K lower than the corresponding methyl esters [66]. Cetane numbers of straight-chain and branched C1-C4 esters and 2-ethylhexyl esters of common fatty acids are not greatly affected by branching in the alcohol moiety (see Table 6.4) [65]. Therefore, branched esters, which improve the cold-flow properties of biodiesel, can be employed

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without greatly influencing ignition properties compared to the more common methyl esters. The combination of improved low-temperature properties with competitive CNs makes the branched fatty acids attractive alternatives to fatty acid methyl esters as diesel fuel. Long-chain or branched-chain esters show considerable advantages regarding pour points, and moderate benefits in cloud points and CFPP [67]. Disadvantages of branched-chain esters are higher price of the alcohol and changes needed in the (trans)esterification process yielding branched esters. In Germ. Patent No. DE 4,040,317 A1, Demmering et al. [68] propose blending with short-chain FAMEs, isolated from transesterified coconut oil, as a means of improving cold-flow properties. Cold-flow improvers (CFIs) were widely developed for petrodiesel. The main practical challenge today is finding effective chemistries to treat the more difficult biodiesel types. Biodiesel cannot be used with conventional EVA-based cold-flow additives or winterising agents typically used for diesel fuel. Petrodiesel CFIs decrease the pour point of SBME/D-2 (B20) blends by up to 18–20 K, but do not affect CP. Cold-flow improvers act by modifying crystal growth, but do not inhibit crystal initiation. They have little effect on the temperature at which the crystals start to form, or the total amount of crystals that form. Rather, when crystals form, CFIs co-crystallise on the edges of the growing crystal plates, thereby blocking the continued growth of the plate. The resulting smaller crystals more easily pass filters and are less able to form a 3D gel that impairs flow of the fuel. The impact on cold-flow properties is that, while CP is little affected, considerable improvements in CFPP and PP can be obtained (see Table 14.11). With the correct choice of CFI in blends, the target CFPP can often be achieved with a lesser quantity of the higher cost FAME. In most cases, the CFI treat cost overcompensates the reduction in cost derived from the more favourable economics of the raw material blend. Dunn et al. [69] have studied the effect of cold-flow additives on cloud point, pour point and cold-filter plugging point. Additive treatment significantly improves PP of methyl ester blends, but does not greatly affect CP; CFPP decreases (although in a rather unpredictable fashion). Viable Table 14.11 Performance of commercial CFIs CFI

Feedstock

®

a

VISCOPLEX 10-305 VISCOPLEX® 10-330b VISCOPLEX® 10-330c a

0.5 wt%. 0.25 wt%. c 0.75 wt%. b

RME SME PME

Beneficial effect (K) on CFPP

CP

PP

13 5 5

1–4 1–4 2

25 > 20 2

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methods for the improvement of cold-flow properties in fatty acid methyl esters need to concentrate more on cloud point than pour point [70]. Poor low-temperature properties, such as high CP and PP, may be improved by adding butyl oleate. Adverse cold-temperature flow properties of biodiesel can also be overcome by addition of glycerol ethers and acetals [71–73]. In cold months (Oct.–April), European biodiesel is usually supplemented in order to guarantee CFPP of 253 K. Also estolides (oligomeric fatty acids formed from the condensation of fatty acids), in particular oleic estolides, used as vegetable-oil based lubricants, have excellent low temperature properties because the random short chains disrupt the stacking interactions and produce considerably lower pour points [74, 75]. The patent literature is scarce in terms of CFI additives specifically designed to improve the cold-weather performance of biodiesel [76, 77]. Lubrizol’s BioQualifiedTM flow improver additives are available that improve the cold-weather performance of many biodiesel blends [78]. Also Evonik’s VISCOPLEX® cold-flow improvers are designed specifically for biodiesel [79]. Nalco Co. (Naperville, IL) also commercialises CFIs. Eur. Pat. Appl. EP 1,681,338 to Matsumura [80] (to Sun Care Fuels Corp.) and ref. [51] describe the use of ozonated vegetable oils (1–1.5 wt%) as pour point depressants of biodiesel fuel. The PP depression action of the biodiesel fuel modifying agent is related to the number of unsaturated double bonds present in vegetable oil used as a raw material for the synthesis of this biodiesel fuel modifying agent. Unsaturated double bonds of triglycerides form ozonides. Vegetable oils such as SNO, LSO and RSO with a large number of unsaturated double bonds are particularly effective for the production of the biodiesel fuel modifying agent (‘ozone-treated vegetable oil’). Ozonised vegetable oils are effective in reducing the pour point of biodiesel prepared from SNO, SBO and RSO to 244, 261 and 243 K, respectively [80]. As shown in Table 14.12, the best results are obtained when the biodiesel and additive are prepared from the same vegetable oil. Significant decreases in pour point of samples added with ozonised SNO were observed in SNO, SBO and RSO biodiesel. Incidentally, also the flash point of biodiesel is decreased; cloud points are not affected. Based on the German biodiesel standard (DIN Table 14.12 Effect of ozone-treated oils on pour point (K) of vegetable oil methyl esters (after ref. [80]) Methyl-esterified Additive-free biodiesel

Addition of 1% ozone-treated vegetable oil SNO

RSO

SBO

PMO

SNME RME SBME PMME

244 243 262 284

253 243 262 286

251 244 261 286

258 263 263 283

269 262 272 287

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Biodiesel science and technology

V51606), SFO and RSO biodiesel supplemented with only 1% ozonised SFO with a dosage of 0.183 g O3/mL oil can be used even during the coldest season in Germany (mid Nov.–end Feb.). Only soy biodiesel treated with ozonised SNO does not pass the German standard. Because almost 50% of FAME components in palm biodiesel are saturated, correction with ozonised vegetable oil (e.g. SFO) to improve the pour point is ineffective. Suitably modified pour points open the possibility of using B100 fuel for a diesel engine. Finally, crystallisation fractionation (winterisation) is a useful technique for decreasing total saturated alkyl ester content. Various methods have been proposed for the partial removal by filtration of low-melting, (mainly) saturated compounds from biodiesel by inducing partial crystallisation upon cooling to produce diesel fuels enriched in unsaturated fatty acid methyl esters. Unit processes employed in commercial crystallisation fractionation of fatty derivatives are dry, solvent and surfactant (detergent) fractionation (see ref. [57]). Supercritical fluid extraction may also be envisaged. Fractionation leaves a mixture with higher content of unsaturated fatty esters and consequently lower CP and PP [81]. As the key to improving the cold-weather performance of biodiesel as a neat fuel and in blends with petrodiesel is to decrease its CP, fractionation to remove high melting-point constituents is one of the most promising approaches. Winterisation of waste cooking oil methyl esters has been proposed to improve cold-temperature fuel properties [82]. However, to achieve significant reduction in pour point, several winterisation steps are required resulting in less acceptable yields. Lee et al. [81] described winterising the neat methyl esters of (low-palmitate) soybean oil. Winterisation can reduce the cloud point of methyl soyate to 257 K. CP/CFPP improve either by dry fractionation of the vegetable oil followed by transesterification of the (higher melting) olein fraction, or by transesterification followed by dry fractionation of FAME [58]. Accordingly, crude palm oil (IV = 52 g I 2/ hg, CP = 293.6 K) was converted to olein-FAME (IV = 56 g I2/hg, CFPP = 275–284 K). Additionally, better valorisation of the stearin-rich fraction for animal feed was obtained. In addition to cold flow, reducing the total saturated ester fraction in biodiesel affects other fuel properties, such as acid value, specific gravity, peroxide value, iodine value, oxidative stability and ignition quality (CN). More specifically, winterisation leads to a decrease in CN value. Although winterisation significantly reduces resistance to autoxidation, it does not greatly compromise fuel quality. However, care must be taken not to remove the entire SFA fraction through winterisation, as these methyl esters have a higher calorific value compared to unsaturated esters. Developing technology to improve CFP of biodiesel (blends) is of great relevance. Dunn [57] has recently reviewed cold-weather properties of biodiesel. Permaflo soy biodiesel is a cold-climate biodiesel (CP 218 K) produced

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using a cold-flow physical fractionation process which separates saturated and unsaturated methyl esters by urea clathration [82a]. Neste Oil’s development of NExBTL Renewable Synthetic Diesel (see Section 15.4.1), based on vegetable oils, was essentially triggered by the poor fuel performance of conventional biodiesel in cold climates. Cold properties (cloud point) of NExBTL can be adjusted in production from 268 K to 243 K, thus meeting the needs of various climatic conditions, in particular in Nordic countries. Moreover, NExBTL is a stable hydrocarbon that can be stored for extended periods.

14.4.2 Storage stability Whereas biodegradability of biodiesel (> 98% in 21 days) is higher than that of conventional diesel, methyl esters are relatively unstable on storage. Biodiesel stability is a top priority. Biodiesel requires proper storage and fuel transport/logistics. Stability encompasses thermal stability under both hot and cold temperatures, resistance to oxidation, polymerisation, water absorption and microbial activity. Instability in biodiesel is partly caused by the presence of unsaturated fatty acid chains. Table 14.13 and Fig. 14.6 show a correlation between chemical parameters and properties of biodiesel. The number and position of the unsaturated bonds exert great influence on the properties of the fuel, such as CN, IV, low-temperature fluidity, and oxidative stability, despite the fact that there is not a direct relation between the unsaturation level in the biodiesel and diesel engine malfunctioning. The problems encountered in the long-term storage of biodiesel are due mainly Table 14.13 Effect of chemical parameters of biodiesel on properties Catalyst Property Acidity High Free Free Free hydroxyl monoalcohol polyalcohol methylestersa residues value Corrosivity + + Cold stability + + Hydrolytic + +   stability Thermal stability + + Oxidation   stability Fire resistance + + Demulsivity + Flash point + Insolubles + Viscosity + Soap formation a

In polyolesters.

+ + +

+ +

650

Biodiesel science and technology

to hydrolytic and oxidative degradation. Hydrolytic degradation consists of hydrolysis of methyl esters to alcohols and acids by the presence of water. In particular, a biodiesel with a high content of mono- and diglycerides tends to absorb water. Oxidative degradation develops from hydroperoxides towards secondary oxidation products. It is influenced by the fatty acid profile (mainly in terms of the number of double bonds), the presence of hydroperoxides, natural antioxidants and pre-oxidising agents (UV light, metals), and by temperature and air (see Section 6.3.4). Bondioli et al. [83] studied the storage stability of rape biodiesel. Oxidation of RME is strongly influenced by the characteristics of the storage container (glass, iron) and by temperature. Stability determination methods, storage and stabilisation of biodiesel fuel have been the subject of the EC-funded project ‘Stability of Biodiesel’ (BIOSTAB) [84, 85]. It is necessary to store biodiesel fuel at proper temperatures (some 15 K above PP) and in stable environments. Biodiesel can be stored under normal storage conditions (avoiding contact with air, water and sunlight) without a dramatic change in quality parameters for a period of 1 year. Most changes affect oxidative stability and peroxide value (PV), depending on the quality and storage conditions. The current industry recommendation is that biodiesel be used within six months. Biodiesel can be stored almost indefinitely in cold climates in appropriate conditions, in particular when using storage-enhancing additives; however, such stability additives can affect fuel separation. It is generally not possible to use biodiesel without antioxidants. The efficiency and the dosage rates of the different antioxidants required depend strongly on the feedstock, biodiesel production technology, storage and handling protocols. Using the correct additives ensures that samples continue to meet the specifications after a storage period of 1 year. Synthetic antioxidants are more effective than natural ones. Not all proven antioxidants for hydrocarbons are equally effective in blends with biodiesel. For jatropha-palm (60 : 40 v/v%) biodiesel 25 ppm antioxidant (BHT) is an optimum dose [61]. If biodiesel is stored in a humid or warm climate, biocide should be added to the biodiesel storage container.

14.4.3 Exhaust emissions The demand for transportation fuel inexorably drives crude oil production (approximately 85 Mbd). To counter the environmental impact of increasing fuel use, a reduction in vehicle emissions is a key driver in determining fuel specification. This requires production of fuels with properties that are increasingly divergent from those of crude oil. Biodiesel is meant to replace petrodiesel and cut carbon emissions, but their savings vary enormously depending on which crop is grown, where it is planted, and how it is harvested

Sustainability and use of biodiesel

651

and processed. The vast uncertainties in GHG emissions reflect different agricultural practices and crop yield (see Section 14.3). The US EPA (Environmental Protection Agency) has evaluated the effects of biodiesel produced from virgin soy oil, rapeseed (canola) oil and animal fats on pollutant emissions (NOx, PM, CO, HC) for heavy-duty engines [86]. Reported average heavy-duty emission effects of B20 relative to conventional diesel fuel are NOx, +2.0%; PM, –10.1%; CO, –11.0%; and HC, –21.1%. With the possible exception of NOx, biodiesel clearly has a significantly lower emission profile in comparison to petrodiesel. Biodiesel originating from animal fats has a lower emission profile than all vegetable oils. Biodiesel eliminates the cloud of dense, black smoke normally associated with diesel vehicles. Exhaust emissions from modern diesel engines using biodiesel and other diesel fuels were recently reviewed [87, 88]. Whereas biodiesel blends reduce smoke opacity, particulates (PM), unburnt hydrocarbons (HC), CO and CO2 emissions (Table 6.8), most reports concur in indicating that biodiesel does not significantly reduce or, worse, even slightly increases NOx emissions (see Table 14.14 [89]). Non-saturation in the fatty compounds causes an increase in NOx exhaust emissions [90]. In fact, used cooking oil (UCO) methyl esters show slightly lower CO and HC emissions but increased NOx values compared with reference fossil diesel fuel [91]. By weight, biodiesel contains less C, S and water and more oxygen than petrodiesel. The higher oxygen content of biodiesel obtained by transesterification of vegetable oil (11 wt% in B100) produces more complete combustion and therefore determines lower tailpipe emissions and soot (elemental carbon) formation compared to petroleum diesel. The CO2 balance depends on the selected raw material and processing. Figure 14.7 shows CO2 emissions of various pure biofuels vs. conventional motor fuels. The reductions are about 60% for bioethanol and 70% for biodiesel. Figure 14.8 indicates that the CO2 balances for NExBTL synthetic diesel are 0.5–1.5 kg CO2/kg fuel gas compared with fossil origin diesel with 3.8 kg CO2/kg Table 14.14 Emission changes with biodiesel fuels (after ref. [89]) Emission

B100

B20

CO CO2 HC Particulates (PM) NOx SO2 Air toxicsa Mutagenicity

–43.2% –78.3% –56.3% –55.4% +5.8% –100% –60% to –90% –80% to –90%

–12.6% –15.7% –11.0% –18.0% +1.2% –20% –12% to –20% –20.0%

a

Polycyclic aromatic hydrocarbons (PAHs).

652

Biodiesel science and technology 100

80

g CO2/MJ

60

40

20

od bi er

nfl

ow

pe Ra

ie

ie

se

se

l

l

l bi

se ie D

od

lf

be ar

ug

BE

-s

ue

et

at he

et -w

be BE

Su

ET

l-

ET

su

ga

r

w no

Et

ha

Et

ha

no

G

l-

as

ol

he

in

at

e

0

14.7 CO2 emissions of biofuels vs. conventional motor fuels. Fossil diesel

Synthetic diesel

FAME (RME)

Crude oil • Production

Vegetable oils • Agriculture • Processing

Animal fats • Transport • Processing

Rapeseed oil • Agriculture • Processing

Transport

Transport

Transport

Transport

Refining diesel

Hydrogen < 0.4 kg CO2/kg

BTL – diesel process

Esterification to FAME

End use diesel 3.2 kg CO2/kg

End use 0 kg CO2/kg

End use 0 kg CO2/kg

S 3.8 kg CO2/kgoe fuel

S 0.5–1.5 kg CO2/ kgoe fuel

S 1.6–2.3 kg CO2/ kgoe fuel

14.8 Life cycle CO2-equivalent emissions for diesel products (Source: Concawe/Eucar WTW Brussels, May 28, 2004).

Sustainability and use of biodiesel

653

fuel and FAME with 1.6–2.3 kg CO2/kg fuel. Increased use of sustainable biodiesel is important to meet the emission reduction targets set under the Kyoto Protocol. Key emissions, such as PM and NOx, form in a different way in the engine: NOx comes from high-temperature combustion, when nitrogen from the intake air reacts with oxygen; particulate is produced in cooler spots where burning of the fuel is incomplete and soot is formed. Changes in engine technology will affect the level of each pollutant. Selective catalytic reduction (SCR) and diesel particulate filters (DPFs) deal with NOx emissions and particulate or soot, respectively. The magnitude of the biodiesel NOx impact still remains controversial [92] and has led to a heated debate over the resulting environmental benefits of using biodiesel over petrodiesel. Although the EPA’s 2002 biodiesel emissions analysis indicated that biodiesel blends lead to higher nitrogen oxide emissions, the EPA now admits that the study was deficient in engine sample representation and the emulation of real-world cycle and load activity. The EPA has recently shown that NOx emission is proportional to test cycle load. The EPA is intending to address the NOx issue in a Collaborative Biodiesel Emission Test Program. Biodiesel impacts on emissions vary depending on the feedstock used (soy, rape or tallow) and on the type of conventional diesel to which the biodiesel is added. Reduction of bio-NOx exhaust emissions to meet increasingly stringent environmental regulations is a technical problem still associated with the use of biodiesel fuels. Strategies for mitigating the NOx increase were outlined in ref. [86]. Fuel density (or energy content), CN and IV were found to be highly correlated with one another in a study on the influence of biodiesel chemical structure on the emission performance (NOx, PM) in a heavy-duty truck engine [93]. NOx emissions increased with increasing fuel density or decreasing CN. Increasing the number of double bonds (or IV) correlates with increasing NOx emissions. For fully saturated fatty acid chains the NOx emission increased with decreasing chain length (C18 to C16 to C12). Cetaneimproving additives (such as 1% di-tert-butylperoxide or 0.5% 2-ethylhexyl nitrate) decrease NOx emissions from petrodiesel. Nitration of biodiesel from waste frying oils has been proposed to produce additives that could substitute 2-ethylhexyl nitrate of petrochemical origin [94]. NOx emissions might be lower by adding a cetane improver to the biodiesel blend. Knothe and Dunn [62] have identified cetane improvers for biodiesel. Nitrogen oxide emissions from biodiesel blends can also be reduced by blending with Fischer–Tropsch diesel (sulphur-free, very high CN) [95]. Regulators want better emissions, end-users want increased fuel economy and OEMs want more power. Meeting new emissions regulations requires tighter controls on primary emissions. Technologies that reduce emissions can be very effective, but they add cost to the engine and can reduce fuel economy. An additive solution is available for reversing the problems

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Biodiesel science and technology

associated with loss of performance caused specifically by engine deposits. As tighter emissions standards are introduced, the use of diesel detergent additives appears to be growing. Diesel injector additives are common in Europe, less so in the US. Using detergent additives at low dosages in the fuel can control or even remove their deposits, restoring combustion performance [96].

14.4.4 Biodiesel properties for various feedstocks Biodiesel properties can vary widely according to the source of the feedstock used and also depend on the production technology or process. In fact, the biodiesel quality standards EN 14214 and ASTM D 6751 (see Chapter 12) have specified relevant parameters to govern the quality of biodiesel. Biodiesel properties are largely influenced by the major components. The fatty acid composition of biodiesel corresponds to that of the parent oil or fat. Some components have a beneficial effect on one property but a negative effect on others (see Table 14.15 [97]). Important fuel properties of biodiesel that are influenced by the fatty acid profile are ultimately ignition quality, exhaust emissions, heat of combustion, cold flow, oxidative stability, viscosity and lubricity [50]. Moreover, in some cases minor components (e.g. natural antioxidants) exert a significant effect as well. Inherent vegetable oil or animal fat properties that affect biodiesel performance as diesel substitute are iodine value (IV), density, viscosity, cetane number, copper strip corrosion, linolenic acid methyl esters content, polyunsaturated (more than few double bonds) methyl esters content and phosphorus content. Properties of biodiesel related to the production technology are the contents of ester, sulphated ash, water, partial glycerides (MG, DG, TG), alkali, free and total glycerol, flash point and acid value. The flash point and methanol content in biodiesel are interrelated. Even a very small amount of methanol will greatly reduce the flash point (see Fig. 12.4). Chemical structure and physical properties of various vegetable oil (soybean, corn, linseed, babassu coconut) esters were correlated [98]. The length of the FA chain has a marked influence on the viscosity and crystallisation Table 14.15 Relationships between fatty acid composition and biodiesel properties (after ref. [97]) Fatty acid (FA)

Positive effect(s)

Saturated Cetane value Oxidative stability Polyunsaturated Cold stability Short-chain FA Distillation curve Long-chain FA

Negative effect(s) Cold stability Oxidative stability Flash point Viscosity Cold stability

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temperature; branching affects only the crystallisation temperature to a significant extent. Viscosity and crystallisation temperature are influenced by the degree of unsaturation. One double bond increases the viscosity, whereas two or three double bonds cause a decrease in viscosity. Unsaturation lowers the crystallisation temperature in all cases, regardless of the number of double bonds. Of the oils studied, babassu coconut oil methyl ester has the lowest crystallisation temperature. As indicated in Tables 14.5 and 14.16, however, there is a greater difference between conventional diesel and biodiesel than between various types of biodiesel. Knothe [50] has described the influence of fatty acid profile (chain length, degree of unsaturation and chain branching) and alcohol moieties of the fatty esters on the overall fuel properties of biodiesel. For example, the NOx emissions are significantly influenced by the proportion of double bonds; saturated fatty esters result in low NOx emissions. Biodiesel produced from RSO or canola has better cold properties than palm biodiesel, although the latter has a high, powerful, cetane number of 65. Rape biodiesel has a CFPP value of approximately 261–263 K without additives and 253 K with additives. Biodiesel based on rapeseed oil (RME) has a naturally high resistance to oxidation (high storage stability). Some car producers are not in favour of providing engine and vehicle warranties for biodiesel other than that derived from rapeseed oil. Palm diesel has been successfully evaluated as a diesel substitute. Due to the presence of some 45% of methyl palmitate, palm diesel has a pour point of 288 K, which limits its usage as a biofuel in countries with a cold climate. The pour point of palm diesel can be lowered by: ∑ addition of cold-flow improvers (CFI); ∑ esterification of palm fatty acids with certain carbon chain length; ∑ dry fractionation of palm oil methyl esters; or ∑ blending with biodiesel with good CFP. Palm diesel with the desired pour point (from 253–273 K) was produced [99, 100]. Blending with jatropha improves cold flow of palm biodiesel [61]. Different CFIs are commercially available and applied. These components are added in low concentrations (0.1–0.5%) and will basically inhibit crystal growth and prevent the filters of the engines from getting plugged at lower temperatures. The effect of the addition of CFI on the cold-flow properties (CFP) is largely product-dependent. Fractionation of FAME is an efficient way to improve CFP (see Section 14.4.1), but is only economically viable if a good outlet can be found for the saturated FAME fraction. The use of soybean oil in the EU for biodiesel production is limited by the iodine value in the EN 14214 standard. Import of SBO also suffers from the European GM limitations. Biodiesel produced from soybean as well as palm olein feedstocks contains fairly large amounts of steryl glycosides (SG). At

656

Fuel property

Diesel No. 2

Soybean methyl ester

Rapeseed methyl ester

Soybean ethyl ester

Rapeseed ethyl ester

Tallow Frying oil methyl ester ethyl ester

Cetane number 40–52 48.7–55.9 47.9–56.0 48.2 64.9–67.4 58.8–61.8 Flash point, K 333–345 393–464 439–443 433 443–458 390–460.8 Distillation IBP, K 458 572 599 482 T10, K 483 601 613 597 T50, K 533 609 617 609 601 T90, K 588 613 621 617 615 EP, K 618 619 639 622 Specific gravity, kg/L 0.85 0.885 0.883 0.881 0.876 0.876 Lower heating value, MJ/kg 43.4 37.0 37.3 Higher heating value, MJ/kg 44.9 40.4 40.7 40.0 40.5 40.2 Cloud point, K 248–258 271.9–276 269 271–274 271–274 285.9–288.6 Pour point, K 248–278 266–273 262.2 267–269 258–261 282–285.8 Cold-filter plugging point, K 253–263 268.6 267–276.6 284 Viscosity at 313 K, CS 2.60 3.99–4.18 4.53–4.96 4.41 6.02–6.17 4.80–4.99 Iodine number, g/hg 8.6 133.2 97.4 123.0 99.7

61.0 397

0.872 37.2 40.5 282 281 5.78

Biodiesel science and technology

Table 14.16 Fuel properties for various biodiesel feedstocks

Sustainability and use of biodiesel

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low temperatures, they form crystals which cause plugging of engine filters, (Minnesota 2005–06 winter problem). By chilling biodiesel SG crystals may be removed by filtration. Cellulose filter aids may also act as a desiccant to bind traces of water. The availability of sunflower oil is limited, and the price generally exceeds that of most other vegetable oils (see Fig. 5.1). Like SBO, SNO also has a high iodine value, thus requiring blending of sunflower biodiesel in order to meet the European norm. Biodiesel quality also depends on the quality of used frying oil, especially on the duration and temperature of heating. During heating of vegetable oils for frying purposes, thermal and oxidative reactions can cause chemical changes, including intra- and intermolecular cyclisation and oligomerisation, as well as (hydro)peroxide formation [101]. Higher oligomer content may influence viscosity, volatility and other fuel parameters, as shown for heated rapeseed oil [101]. Hydrolytic reactions can induce formation of mono- and diglycerides, and free fatty acids. Limitations of cheap used cooking oils and rendered animal fats are largely technical (see Chapter 9). Biodiesel produced from waste cooking oil is liable to freeze in winter. Blending with a high percentage of rape biodiesel is required to meet the EN 14214 standard. Another option is blending with low pour point palm diesel (without additives). Palm oil is usually more cost-effective and abundantly available. As the life cycle analysis for biodiesel from rendered fats is better than for RME (see Section 14.3), the use of rendered fats as additional feedstock for biodiesel production is an economic and ecologic alternative. Fatty acid profiles can be engineered to optimise biodiesel fuel characteristics. Given the antagonistic requirements between cold-temperature flow properties on the one hand and oxidative stability (see Fig. 14.6), NOx emissions and cetane number on the other, there is no fatty acid profile that will provide a fuel for which all these parameters are optimal (Table 14.17 [50, 93, 102–104]). However, a very good compromise is reached for a fuel high in mono-unsaturated fatty acids (typically 18 : 1 or 16 : 1), and low in both saturated and polysaturated fatty acids. This has been verified for high-oleic transgenic soybean oil (C18 : 1, >85%; SFA, < 6%) [105] by Van Gerpen et al. [106]. The objective of the EU ALTENER-2 programme 2003–07 (coordinated by the Austrian Biofuels Institute) was testing a broad variety of oilseeds and fats (RSO, SBO, SNO, PMO, CNO) with attractive fatty acid profiles (e.g. low-linolenic, high-oleic, short-chain fatty acids) in pure and blended form in order to develop and define an optimum designer biodiesel with lowest feedstock cost but highest biodiesel quality. In fact, there is essentially no ideal or unique fatty acid composition for biodiesel at a global level to be expected. Various options are suited under various climatic conditions. At most, the best feedstock sources and intelligent blends in a given geographical

658

Biodiesel science and technology

Table 14.17 Comparison of fuel properties of the main FAME components of biodiesel with conventional diesel

C16 : 1

C18 : 0

C18 : 1

C18 : 2

C18 : 3

Double bonds Cold flowa Fuel stabilityb NOx emissionsc Ignition qualityd

0 Worse Good Lower Higher

0 Worse Good Lower Higher

1 Similar Satisfactory Similar Higher

2 n.g. Poor Higher Similar

3 n.g. Poor Higher Lowere

a

Ref. [102]. Comparison between various FAMEs; refs. [103, 104]. c Ref. [93]. d Ref. [50]. e Ethyl linolenate. b

user area may be identified. Various tropical oil plants can be assumed to be suitable from the point of view of cost and availability. Low-temperature flow properties are most important in countries with cold winters. For those fatty acids, double bonds are unavoidable. When fatty acid profiles indicate poor cold-flow properties, the suitability for FAME production could be limited to use as a blending component. The key factor for biodiesel is that feedstock must be economical. The crux for a feedstock is the minimal quality requirements of the aforementioned recognised standards, leading to problems for such feedstocks as SBO, SNO, UCO/TLW and others. A Biodiesel Cost Optimizer model was developed to permit objective matching raw materials blends with specific performance characteristics at the lowest possible total cost of the blend [107]. Important car companies (such as DaimlerChrysler, GM, Ford, Volkswagen, Citroen, Peugeot, Renault and others) and farm equipment manufacturers (John Deere) publicly endorse biodiesel. Chrysler LLC supports the use of up to B5 biodiesel in its diesel vehicles. Several (German) vehicle manufacturers only approve RME for operation with biodiesel. As a result, in Germany only rape biodiesel is offered for sale at public filling stations.

14.5

Biodiesel cost structure

In addition to meeting engine performance and emissions specifications, biodiesel needs to compete economically with petrodiesel fuel. The economic competitiveness of biodiesel is not ensured. Two major factors that determine the viability of any fuel are the economic cost and energy ratio. Mineral oil is about as expensive as biofuels if all external costs are taken into account. Nevertheless, the apparent price gap between petro- and bio-based products needs to be closed before ecofuels will make their much needed inroad. Biodiesel fuel may become an ideal biofuel of the future only if sustainable economical production can be assured.

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Biodiesel production costs need to take into account the impacts of net feedstock production costs plus capital and operating costs. Economic evaluation criteria are indicated in Table 14.18. Plant capacity, processing mode, feedstock cost and market price of biodiesel (and meal cake and glycerine by-product values) are major factors affecting the economic feasibility of biodiesel manufacture [108, 109]. Transportation costs, quality supply and reliability are some of the obvious costs of procurement. Biodiesel yield, storage, oxidation stability, disposal cost, labour and infrastructure are some of the other costs of operating a biodiesel plant [110]. Variables in cost calculation are biodiesel technology, production capacity and plant location. A typical 100 kt/yr (Desmet Ballestra) biodiesel plant requires an initial investment (2008) of about 730 M (crude oil basis), with operating costs of 740–50/t for refined oils to 760–70/t for crude oils, and 30–35 operators. Investment costs for recently installed 250 kt/yr French plants in Le Meriot and St Nazaire (Diester Industrie) were quoted as 795 M (including 770 M for a rapeseed crushing and refining facility and 725 M for a transesterification unit) and 735 M (refinery, esterification and storage facilities), respectively. Investment in the prospected 250 kt/yr Rosendaal Energy MFT facility requires 760 M, as compared to 790 M for a 500 kt/ yr Ineos plant in Grangemouth (now shelved). The prospected Greenline Industries LLC/Oilsource Holding LLC joint venture Miami plant requires an investment of the order of US$96 M/60 MMgy or US$1.6/gal installed. In Argentine conditions, 50–150 kt plants require investments of the order of US$15–25 M, as compared to US$35–45 M for 200–300 kt plants [111]. Studies of biodiesel production with soybeans and canola clearly indicate that average biodiesel processing cost is minimised in plants producing more than 10 MMgy [112]. Most estimates for these larger plants indicate that crushing and processing costs are about US$0.50/gal and total processing cost is about US$1/gal. Crushing costs are estimated as being less than US$0.30/ gal in a large plant (27 MMgy) producing both soy and canola oil [113]. The economics of producing biodiesel is dependent on the input costs relative to the income generated by the scale of biodiesel and its reaction byproducts (protein, glycerol and fertiliser salt). Biodiesel producers typically sell raw glycerol to be refined to remove the contaminants and make the glycerol suitable for a wide range of applications, including food additives and

Table 14.18 Economic evaluation criteria for biodiesel production ∑ ∑ ∑ ∑

Fixed capital cost (plant size) Total manufacturing costs (raw materials, catalysts and solvents; energy consumption, operational and maintenance costs) Break-even price (biodiesel, by-product credits) After-tax rate of return

660

Biodiesel science and technology Table 14.19 Projected production costs for diesel fuel by feedstock, 2004–06a,b (after ref. [114]) Marketing year

Soybean oil

Yellow grease

Petroleum

2004–05 2005–06 2006–07

2.54 2.49 2.47

1.41 1.39 1.38

0.67 0.78 0.77

a

In 2002 US$/gal. Biodiesel costs for total output of 80 Mgy, exclusive of distribution or applicable taxes. b

personal care products. As costly purification of crude glycerol is necessary to prepare it for third party usage, the market price is minimal. Increased demand for biodiesel has led to an overproduction of seed meal and glycerol in Europe. For these two products new markets need to be identified. Falling prices of the by-products negatively influence overall biodiesel production costs. Some prospective industrial alternatives for use of crude glycerol, as outlined in Section 13.5, are expected to be most beneficial to the economics of biodiesel fuel production. NREL has provided estimates of other components of biodiesel production costs, based on base-catalysed transesterification of oil with methanol. Operating expenses were estimated at 31 cts/gal (2002 cts), excluding the cost of oil or grease and energy; the commercial value of glycerol was accounted for reducing the cost by 15 cts/gal of biodiesel [115]. Energy costs were estimated at 18 cts/gal (in 2002 cts) in 2004 and 16 cts/gal in 2005–06 [116]. Estimated capital cost of a biodiesel plant was set at 13.6 cts/gal (2002 cts) at full output. Table 14.19 then shows the total production costs for diesel fuel by type of feedstock (SBO, yellow grease, petroleum). The projected cost of biodiesel according to Table 14.19 is higher than that of petroleum based diesel. Typical biodiesel production costs in 2008 are reported as 70.4–0.7/L (71 = US$1.5).

14.5.1 Feedstock costs Prices of vegetable oils, semi-refined or fully refined vegetable oils of ediblegrade quality, are relatively high for fuel-grade commodities: typically, crude SBO sells at US$480–570/t (in 2003–04), more recently (June 2008) even at US$1376/t, or about US$0.50–1.30 for the oil sufficient to produce one litre of biodiesel. Oil(seed) prices are seasonal and can vary greatly (see Figs 5.1, 14.9, 14.10 and Table 5.9). Recent developments show that feedstock prices are difficult to predict. Virgin vegetable oil market prices are affected by crop growing variables such as season, drought, early frost, poor harvest and biological pests as well as by origin and volatility of the vegetable oil markets (influenced by demand, multinationals, political

Sustainability and use of biodiesel

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1000 Palm 900

Sunflower Rape

800

Soy

700

US$/t

600 500 400 300 200 100

2006/07

2005/06

2004/05

2003/04

2002/03

2001/02

2000/01

1999/00

0

Year

14.9 World market prices of soft vegetable oils.

mandates, speculation, etc.). Vegetable oil prices have tripled within 2007–08 from US$500/t to US$1500/t (Table 14.20). RBD palm olein at US$900/t is at an all-time high. Recycled waste oils are much less expensive and are not directly affected by the growing season. Several years ago (before substantial biodiesel production), at a time of gradually increasing oil prices, agricultural raw materials were becoming cheaper as a consequence of increasing agricultural efficiency and yield, thus creating the conditions for tipping the economic balance towards the use of renewable resources. The biodiesel industry has actually developed on the glut of virgin oils, such as RSO and SBO, which were on the market some 5–10 years ago. The rally in key vegetable oil prices since July 2006 has determined an increase from about US$70/barrel for soya oil (Argentina) and palm oil (Europe) to US$130 (Nov. 2007) causing a macroeconomic shock; in the same period crude mineral oil increased from US$70 to US$95/ barrel. Moreover, in 2007 all major vegetable oils began to move in strong correlation with crude oil prices. Agricultural lipids are now being traded globally as an energy commodity. Resulting price increases over 2007 at origin (average FOB prices in US$) have been remarkable, e.g. 75% for SNO and 66% for CPO. Even yellow grease (mainly recycled cooking oil) and tallow (rendered beef fat) have

662

Biodiesel science and technology 45 (a) 40 (b) 35

US cents/lb

30

(c)

25 (d)

20 15 10 5

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

0

14.10 Price development (2006–07) of (a) palm olein RBD (US Gulf), (b) crude/degummed soybean oil (Illinois), (c) intermediate tallow (6% FFA) (Chicago Prime), and (d) yellow grease (Illinois) (Source: Jacobsen Publishing Co.). Table 14.20 Escalation of vegetable oil market pricesa (after ref. [117]) Period

Soyb

Canolac

Palmd

Aug. 2008 June 2008 March 2008 June 2007 2005–06 2004–05 2000–01 1999–2000

1120 1376 – 684 – 507 – –

– 1577 – – 770 – – 359

879 – 1291 – 416 – 235 –

a

US$/pmt. USA. c Europe. d Malaysia. b

been rising steadily by 70% in response to anticipated demand for biodiesel production. The agricultural commodity price inflation has originated from a structural mismatch between global demand and supply for both food and

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fuel needs (see Section 5.3), and partly from rampant speculative interest [118]. In particular, the effect of China’s growth has been massive. Chinese oilseed imports have increased in 10 years from 4.6 Mt/yr (1997) to 31.6 Mt/ yr (2007). At the current rate, the country needs at least another 20 Million tonnes of imported oilseeds in less than 10 years’ time. On the basis of increased demand from major consumers, prices for cereals on the world markets are expected to remain high and the food sector is likely to reclaim market share from the biofuel industry. For current pricing of selected oils and fats, see www.icis.com and www.oilsandfatsinternational.com. Historical price developments (e.g. for RBDPO, RBDPS, PKO, SBO, CSO, CNO and TLW) are also readily available [119]. The October 2008 financial crisis has shaken all the commodity markets. It is a commonly held view that feedstock costs (oils and fats), while highly dependent on food markets volatility, are controlling the costs of conventional biofuels to some 60% to 80% and thus constitute the major obstacle to the market feasibility of biodiesel [15, 120–122]. Semi-refined and refined vegetable oils are still the predominant feedstocks for production of biodiesel. Their use decreases the complexity of commercial plants. However, their relatively high costs render the resulting fuels unable to compete with petroleum-derived fuel. Average production cost per litre can be approximated from available lipid feedstock prices, increased by a US$0.12 refining cost and decreased by US$0.04 for the sale of by-products. According to Zhang et al. [109] the direct manufacturing cost (including raw material costs, catalyst and solvent costs) represents 63–75% of the total manufacturing cost in various technologically feasible processes at high processing efficiency (~ 100%). More precisely, the cost of feedstock oil comprises up to 50% of the direct manufacturing cost for a first-generation acid-catalysed process, as compared to 80% for virgin oil in base-catalysed processes. The feedstock cost share for rapeseed diesel is typically about 70%, which can be partly reduced by the sale of by-products accounting for about 15% and more of the total production costs. Various options can lower the production costs significantly, such as the use of alternative feedstocks, adaptation of a continuous transesterification process and recovery of highquality glycerol. Multiple feedstock (animal fats, PMO, SBO, SNO, RSO, CSO, UFO/UCO, jatropha) stands for flexibility and lower costs. In-line blending keeps quality up, costs down [123]. The true costs and benefits of biofuels are highly debated [124]. Palm oil is currently the best option, compared with RSO and SBO, in terms of process economics. The most destabilising factor facing the biodiesel industry in the coming years is the economics of inordinately high (edible) feedstock costs. Until oilseed producers catch up with demand, high seed oil prices are likely to negatively affect biodiesel production. Although it has recently been argued that 2015 may see an annual oil demand of 165 Mt as compared to an upper-limit

664

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total potential volume of 530 Mt due to agricultural yield increases, thereby largely overcoming the present demand/supply problems [125], it should be remembered that in the past tripling the crop yield of a typical vegetable oil (RSO) took 50 years. Moreover, agricultural productivity is limited by the availability of water. Efforts to identify and develop more sustainable feedstocks (e.g. algae, jatropha, etc.) show great promise but require time and application of resources to become available. These alternative raw materials are options for the longer term only. It is of interest to notice that at US$72/barrel of crude oil the wholesale market price of algae oil was US$1.71/gal as compared with US$2.81/gal of soybean oil. Long-term factors appear to be in favour of a gradual replacement of RSO and SNO as biodiesel feedstocks by SBO and CPO. In Europe, the cost of RSO typically employed in biodiesel production is roughly 25% higher than that of SBO in the US, which does not contribute to its competitive edge. Expectations are that US soy product prices will increase as many US farmers – despite high demand – are switching to corn cultivation. Currently, soybean and corn are at an all-time high. Soy biodiesel has advantages over its competitors, namely lower production costs than canola and suitability for use in colder regions. Argentina is quickly becoming a world leader in biodiesel production. The country is characterised by an abundant biodiesel feedstock supply, including SBO (Sante Fé, Córdoba and Buenos Aires provinces) and SNO (mainly Buenos Aires), with prospects for TLW/UCO (beef industry, restaurants) and jatropha (North-West Argentina). In particular, Argentina is a low-cost producer of soy biodiesel, taking advantage of an important domestic cost advantage of SBO (32% below international market price) over producers elsewhere, modern oilseed crushing capacity (150 ktd) and a rapidly growing biofuel capacity (from 150 kt in 2006 to 1.4 Mt in 2008 and forecasted 3.5 Mt by end 2010) [126]. Virtually all of Argentina’s biodiesel production (already 500 kt in the first half of 2008) is for export to Europe (via the US), subject to a 20% export tax (Retención). Palm oil is often cited as the big hope in terms of meeting increasing biodiesel demand. The economic viability of palm diesel production was still considered questionable in Aug. 2005 [127]. As for other crops, the price has to be right if palm oil is to be channelled into biodiesel. Crude palm oil is still the cheapest vegetable oil (see Table 5.9 and Fig. 14.9) despite a new all-time record price of US$840/t (or US$135/barrel) registered in May 2007, as compared to a then Brent crude oil price of around US$70/barrel. Lauric oils have even exceeded US$1000/t (C&F Rotterdam). A similar development (with price rises of over 90% in one year) has also been noted for SBO and CNO. This scenario obviously benefits vegetable oil producers but hurts the food, oleochemical and biodiesel business. The surge in price of vegetable oils and deterioration in its competitive position as an industrial feedstock

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has led to delays in implementation of numerous biodiesel projects as they have become unprofitable. As also the price of other commodities used in biodiesel production have recently increased considerably, with methanol prices rising from US$0.36/gal in Feb. 2002 to US$2.50/gal in Dec. 2007, it is not surprising that various commercial operators in Europe, the US, Malaysia and Australia have (temporarily) mothballed plants. An economic analysis of the production of biodiesel using different edible oils (CNO, LSO, PNO, RSO, SBO, SEO, SFO, SNO) and a non-edible oil (pongamia) in Indian conditions (2005) has indicated that only pongamia, linseed and coconut biodiesel are competitive with petrodiesel [128]. Biodiesel costs were found to increase in the order pongamia < LSO < CNO < SBO < RSO < SNO < PNO < SFO < SEO. Although soybeans are the most expensive feedstock with only 20% of oil content, its by-product meal cake has the highest monetary credit. At a value of US$0.52/kg (US$0.236/lb) for SBO feedstock, a biodiesel production cost (2006) of US$0.53/L (US$2.00/ gal) was indicated [129]. In this case the oil feedstock accounts for 88% of the total estimated production costs. The cost of biodiesel can eventually be reduced if we consider other nonedible oils, such as jatropha, babassu, mahua, karanja, which are available in many parts of the world (e.g. India, Brazil), used frying oils and acid oils (see Chapter 9). Although alternative feedstocks are cheaper than conventional (refined) virgin oils, they require higher conversion costs (pre-treatment and acid esterification for high FFA oils), namely 7120–150/t vs 760–90/t for conventional feedstocks. Low-value feedstocks are typically heterogeneous lipid mixtures that require multiple chemical steps to produce FAME and can yield ester preparations requiring greater degrees of clean-up than those from refined oils to meet the quality specification for biodiesel. Animal fats and inferior high FFA oils (waste oils, new emerging feedstock such as algae oil) all require acid transesterification catalysis or at least acid pre-treatment (esterification). Use of such low-value feedstocks in an acid-catalysed transesterification process helps make biodiesel competitive in price with petroleum diesel [109]. Low-cost, scalable, continuous-flow, skid mounted acid pre-treatment systems that can front-end any existing base-catalysed biodiesel system, allow efficient conversion of FFAs into useable oil with no yield loss [130]. Table 14.21 shows the effect of feedstock pricing of several low-value oils and fats on biodiesel production cost. Used frying oils are widely available in many countries (US, Western Europe, Japan); logistics and quality are apparent drawbacks. Moreover, competing uses of yellow grease (in production of soaps and detergents, or as feed additive) limit the potential supply of this feedstock for fuel use by biodiesel production to at most 100 Mgy [131]. Few industrial plants actually use recycled cooking oils extensively as a feedstock for biodiesel production. Fatty acid methyl esters can also be produced from tall oil, which consists

666

Biodiesel science and technology Table 14.21 Biodiesel feedstock pricing and impact on production cost (US$, 2007) Feedstock Price/lb

Feedstock weight/gala

Feedstock cost/galb

Crude SBO Inedible TLW Poultry fat Yellow grease (6–15% FFA) Brown grease (> 15% FFA)

7.5 7.5 7.5 8 8

$2.63 $1.87 $1.87 $0.64–1.60 $0.40–1.20

a

$0.35 $0.25 $0.25 $0.08–0.20 $0.05–0.15

Estimated pounds of feedstock per gallon of biodiesel. Feedstock cost per gallon of biodiesel produced.

b

of free C18 unsaturated fatty acids, resin acids and relatively small amounts of unsaponifiables (see Section 9.7). Acid oil, a major by-product of the alkali refining industries, is another potential raw material for producing biodiesel [132] (see Section 5.10.2). The production cost of soapstock biodiesel would be approximately US$0.41/L (2005), i.e. a 25% reduction relative to soybean diesel (US$0.53/L) [133] (see Section 9.6). Multi-feedstock capability is nowadays a business necessity instead of only a competitive advantage.

14.5.2 Manufacturing costs Biodiesel can be produced by several processes (see Chapters 8–11). Refining costs generally scale linearly with volume for each processor type; continuous-flow reactors have lower overall costs of production than batch reactors due to their higher overall efficiency and throughput. Base catalysation is preferred industrially because the reaction is quick and in high yield. It also occurs at lower T, p than other processes, resulting in lower capital and operating costs for the biodiesel plant. Various economic assessments of transesterification processes have been published [109, 129, 134–140]. Although the alkali-catalysed process using virgin VOs has the lowest fixed capital cost, the acid-catalysed process using WVO is more economically feasible overall, providing a lower total manufacturing cost, a more attractive after-tax rate of return and a lower biodiesel break-even price [109]. The cost of transesterification reactor(s) forms a significant part of the capital investment, especially for acid-catalysed processes (up to 35–46% of the total cost). Large amounts of methanol required in acid-catalysed processes lead to an increased reaction volume. Processes requiring very high molar ratios of methanol-to-oil (e.g. 245 : 1 in ref. [141]) are technologically feasible but not economically reasonable at break-even prices far exceeding those mentioned in Table 14.22. In addition, there is the need for stainless steel as construction material for reactors and some downstream units. The

Table 14.22 Economic evaluation for biodiesel production plants using (first-generation) homogeneous catalysts Noordam and Withers [135]

Bender [136]

Zhang et al. [109]

Zhang et al. [109]

Plant capacity Process type Raw material Biodiesel break-even   price (year)

7800 t/yr Alkali-catalysed batch process Canola oilseed US$763/t (1996)

10 560 t/yr Alkali-catalysed batch/continuous processes VOsa, animal fats US$540–620/t, US$340–420/t (1999)

8000 t/yr Alkali-catalysed continuous process Canola oilseed US$857/t (2003)

8000 t/yr Alkali -catalysed continuous process Waste canola oilseed US$644/t (2003)

a

100 000 t/yr Alkali-catalysed continuous process Beef tallow US$340/t (1994)

Oilseeds: SBO, CO, SNO, RSO.

Sustainability and use of biodiesel

Feature Nelson et al. [134]

667

668

Biodiesel science and technology

need for a pre-treatment unit is unfavourable for the fixed capital cost of an alkali-catalysed process of waste vegetable oils. Table 14.23 summarises the economic prospects of transesterification technology of vegetable oils and animal fats for biodiesel production. Because the base-catalysed method is the most widely used and the majority of biodiesel currently produced in the US is derived from expensive high-purity virgin soybean oil (FFA < 0.5%), the resulting production costs currently make the US biodiesel industry commercially non-viable without government support. Producing more economically means obtaining an ester within specification together with pure glycerol, at a reasonable spatial velocity and reaction times, and without a rigorous purification system. Second-generation biodiesel technology, based on important process innovations and flexible, cheap feedstocks rather than refined, expensive foodstocks allows considerable economic advantages over conventional biodiesel production. For more details, see Table 14.24 and Section 15.3. Procedures under high pressure are generally very expensive from the point of view of plant costs, and should be avoided. Nevertheless, a recent cost evaluation of industrial scale biodiesel production from waste cooking oil by supercritical transesterification in 8 kt/yr to 125 kt/yr plants indicated that the process can compete with the existing alkali- and acid-catalysed processes [138]. Recently, four continuous 8 kt/yr biodiesel production processes for conversion of waste vegetable oil feedstocks were assessed using HYSYSbased process simulation [140]. Processes I and II of Table 14.25 employed traditional homogeneous alkali and acid catalysts, respectively, while process III used a heterogeneous acid catalyst; the catalyst-free process IV was based on supercritical methanol treatment. All four processes produced biodiesel of higher purity than required by the ASTM D 6751 standard of 99.65%. The heterogeneous and supercritical processes were the least complex with the smallest number of unit operations. The key differences between the processes relate to the catalyst removal method and separation of glycerol. Each process was evaluated based on total capital investment (TCI), total manufacturing cost (TMC) and after-tax rate-of-return (ATROR) (Table 14.26). The direct manufacturing cost (DMC) represents between 71% and 77% of TMC of each process. The largest proportion of DMC is due to oil feedstock, namely 40–50%. As predicted by Lotero et al. [142], the relatively simple one-step heterogeneous acid-catalysed process III is by far the most economically attractive process, as it had the only positive rate-of-return, lowest capital investment and lowest total manufacturing costs, due to the use of low-cost waste vegetable oil and lower utility costs of the process resulting from the smaller material streams involved. Only process III could earn a profit in US conditions without any government subsidy. The

Table 14.23 Economic prospects of transesterification technology of vegetable oils/animal fats for biodiesel application Main feature(s)

In-situ transesterification Non-catalytic Catalytic Ethanolysis Acid catalysis Enzymatic catalysis Homogeneous alkaline catalysis Heterogeneous alkaline catalysis Homogeneous acid catalysis Heterogeneous acid catalysis High-pressure methods Low-pressure, low-temperature process Batch processing Continuous processing Solvent homogenisation Supercritical alcohol

High price of absolute EtOH and longer-chain alcohols Energy consuming, long reaction time Production costs of edible oils Energy consuming Energy consuming Expensive catalysts; poor reaction efficiency High feedstock cost Severe reaction conditions (T, p), high alcohol volumes; lower investment costs Low cost (catalyst, feedstock) Favourable process economics, low-quality feedstocks High process costs High edible oil feedstock cost Small plants only (0.5–10 kt/yr) Large plants (> 30 kt/yr); complex processing High solvent consumption Unfavourable reaction conditions (T, t), high alcohol volumes, low ester yields

Sustainability and use of biodiesel

Procedure

669

670

Biodiesel science and technology Table 14.24 Economic advantages of second-generation biodiesel technology Alternative feedstocks: ∑ No feedstock purification ∑ Allowance for lower-cost low-quality multi-feedstocks Process innovation: ∑ Reusable high-performance heterogeneous catalysts ∑ Reduced catalyst requirements ∑ No need for catalyst recovery ∑ Simplified process schemes ∑ Simplified product purification technology ∑ No need for downstream washing steps ∑ No associated waste saline streams requiring disposal ∑ Innovative reactor concepts ∑ Lower investment costs ∑ Continuous processing ∑ No corrosion problems Product improvements: ∑ Increased biodiesel yield (~ 100%) ∑ High-purity biodiesel ∑ High-purity glycerol (> 96%) ∑ No waste products

Table 14.25 Unit operating conditions for four continuous biodiesel production processes (after ref. [140])

I II III IV Pre-treated Acid-catalysed Heterogeneous Supercritical alkali-catalysed acid-catalysed process

Transesterification Feedstock WVO (5% FFA) WCO (5% FFA) WVO SnO Catalyst H2SO4a/NaOH H2SO4 Reactor type CSTRa/CSTR CSTR Multi-phase Temperature (K) 343a/333 353 333 Pressure (MPa) 0.4a/0.4 0.4 0.1 Alcohol-to-oil ratio 6 : 1a/6 : 1 50 : 1 4.5 : 1 Residence time (h) 1a/4 4 3 Conversion (%) 100a/95 97 94 Methanol recovery Recovery (%) 94a/94 99.2 99.9 Catalyst removal Glycerol – Hydrocyclone washa/– Glycerol separation Water washing Water Gravity washing settling Catalyst neutralisation Neutralising agent H3PO4 CaSO4 – Biodiesel recovery Recovery (%) 99.9 98.65 99.9 Final purity (%) 99.97 99.65 99.9 a

WVO – CSTR 623 20 42 : 1 0.33 98 99.3 – Gravity settling – 99.9 99.65

Operating conditions for the pre-treatment unit in the pre-treatment case.

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Table 14.26 Economic evaluation for four 8 kt/yr continuous biodiesel production processes (after ref. [140]) Costa

Pre-treated Homogeneous Heterogeneous Supercritical alkali- acid- acid- process catalysed catalysed catalysed

Total capital investment 1.59 Direct manufacturing 4.19   cost Oil feedstock 1.66 Indirect manufacturing 0.46   cost General expenses 0.89 Total production cost 5.78 After-tax rate-of-return –22.2   (%) a

1.99 3.84

0.63 3.19

2.15 3.61

1.63 0.47

1.66 0.42

1.66 0.47

0.84 5.37 –8.71

0.69 4.45 58.76

0.81 5.19 –0.90

Costs are reported as US$ millions.

Table 14.27 Economic comparison of the conventional and Mcgyan biodiesel production processes (after ref. [139])

Soybean oil

Acidulated soapstock

Operating costs per gallon (US$) Sale price per gallon (US$) Blending tax credit (US$) Net gross profit per gallon (US$)

2.87 2.10 1.00 0.23

2.13 2.10 1.00 0.97

large excesses of methanol in processes II and IV resulted in much higher manufacturing costs than in process III. The total manufacturing cost of the supercritical process is slightly more than that of process III, owing to large energy requirements for the separation of methanol from the product stream. TMC of process I is highest because of the pre-treatment step. The relative economic order for processes I and II is in agreement with earlier assessment by Zhang et al. [109]. The Mcgyan process (see Section 9.3.1) is another highly cost competitive biodiesel process [139]. Although both acidulated soapstock and refined triglyceride sources produce nearly identical quality biodiesel fuels in this process, the economics of production for these two feedstocks is markedly different. Table 14.27 shows an economic comparison of the conventional and Mcgyan biodiesel production processes based on lipid feedstock prices of US$0.35 and US$0.25/lb for virgin soybean oil and acidulated soapstock, respectively. Another economic benefit of the Mcgyan process is the predicted reduction in capital costs due to the elimination of process chemicals and of large batch reactors and water washing tanks in a commercial production plant.

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14.5.3 Biodiesel competitiveness The economics of biodiesel encompass both a private and a public dimension. In the private dimension, success requires that incentives for producers, blenders and consumers be sufficient to compete in the marketplace with the alternatives available (e.g. alternative uses of land, labour and capital, and alternative fuel choice for consumers). In the public dimension, success is defined in terms of the public goals that motivate government’s intervention (i.e. subsidies) and whether biodiesel will achieve the public goals in a costeffective manner, when compared to other options. It is important to evaluate both dimensions. If the public evaluation is highly favourable but the market incentives are inadequate, no biodiesel will be produced. On the other hand, if market prices generate strong interest among producers and consumers, but the social gains are very small, or the costs are very high compared to other approaches, then the activity may not represent a good use of scarce public resources. The private costs of producing biodiesel, as compared to market biodiesel prices, can be presented in several useful ways. From the blender’s perspective, it is important to estimate the feedstock price for biodiesel production to break even at current market prices. It is suggested that feedstock prices need to be 50–90% lower than current market prices [112]. From the grower’s perspective, it is crucial to know the per-acre subsidy which would allow growers and processors to break even on producing biodiesel. Given a US$125/ acre opportunity cost of land, a subsidy of between US$173 and US$422/ acre is necessary [112]. Cost estimates per gallon depend on the seeds’ oil content and on crushing efficiency. Operating scale markedly affects average costs (see Section 3.6.2). The European transportation sector is diesel dominated, in contrast to the US. Europe, which has far higher fossil fuel prices at the pump than the United States (cf. US$9/gal diesel in the UK vs. US$4.2/gal in the US; May 2008), primarily because of taxes, also has self-imposed stringent and rising biofuel requirements which cannot be satisfied from domestic production. The economical feasibility of biodiesel fuels depends on the feedstock, geographic area, variability in crop production from season to season, production and distribution, the price of crude petroleum, amongst other factors. As with all industrial processes based on natural raw materials, supplies are season-bounded (except in the tropics), which adds to the difficulty of economic operation. Both changes in the petroleum industry and in (inter) national renewable energy and fuel prices have a direct impact on biodiesel competitiveness. Crude oil prices have been driven largely by international geopolitical forces, but are also influenced (at least in the short term) by finished product inventory fluctuations, refinery rationalisations, economic performance, etc. In the long term, the cost of crude petroleum is bound to

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increase due to increases in demand and limited supply. Moreover, the ever stricter regulations on the aromatics and sulphur contents in diesel fuels result in a higher cost of production of petrodiesel. Decreasing sulphur content is a market opportunity for biodiesel which is rapidly becoming a desirable additive for low lubricity ultra-low-sulphur diesel. The total economic package surrounding biodiesel is far from clear with a variety of incentives and tax breaks. Biodiesel production in any country is in the most part driven by legislation and government targets (see Section 1.2). Government price controls and subsidies (B99.9) distort both the vegetable oil and fuel markets. Farmers are paid not to grow certain crops. Farm commodity programmes were designed to ensure that farmers do not overproduce crops to keep prices of farm products from dropping. Unlike the price of fossil fuel, the price of vegetable oil is not kept artificially low. Jaeger and Siegel [112] have considered the full cost of biodiesel production with current subsidies available to growers and processors (Oregon’s Willamette Valley, 2008). It appears that for every dollar paid in subsidies, the public pays an additional US$0.20 to 0.40 in added distortionary cost associated with the subsidies’ financing. Public economics thus indicate that biodiesel is not a cost-effective way to reduce fossil fuel consumption (or GHG emissions), in accordance with an analysis of rape biodiesel [143]. Omitting government subsidies, biodiesel production costs for all six feedstocks considered, namely canola (winter and spring), flax (linseed or solin/linola), camelina, yellow mustard, sunflower and safflower, exceed revenues for all biodiesel options. Compared to biodiesel wholesale prices in Oregon of about US$2.50/gal in 2007, locally produced biodiesel would cost an estimated US$5.85/gal for flax feedstock, US$6.84/gal for winter canola, and US$12.94/gal for yellow mustard (excluding co-product credits) [112]. Federal and state subsidies to growers and blenders, which do not exceed US$2.30 and US$3.10/gal, are insufficient to reach the break-even point. The economic outlook for biodiesel production, which depends greatly on cost structure (feedstock, technology, wages) and the effects of energy policy (mandates, tax credits, etc.), differs for developed and emerging markets (Table 14.28). EU and US markets are transiting away from subsidies. In Brazil, India and China, economic and environmental security concerns are giving birth to new government targets and incentives, aimed at reducing petroleum imports and increasing the production and consumption of renewable fuels. Despite feedstock yield improvement scenarios, growth of first-generation feedstocks in developed countries is limited. First-generation markets are shifting to large scale and next-generation plants (non-food feedstocks, new technologies). Brazil, India and China largely support nonfood feedstocks. Illustrative retail price indications for petrodiesel and biodiesel in Europe are 70.867 and 70.765, respectively (Oct. 2003, Germany) and 70.728 and

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Table 14.28 Economic sustainability outlook for biodiesel Market

Outlook a

Developed markets ∑ First generation commodity/food-grade feedstocks ∑ First generation non-food feedstocks ∑ Second generation

Consolidating Accelerating Expanding

Emerging marketsb ∑ First generation commodity/food-grade feedstocks ∑ First generation non-food feedstocks ∑ Second generation

Rapid expansion Rapid expansion Opportunities

a

Europe, US, Malaysia. Brazil, India, China and Argentina.

b

70.717/L, respectively (March 2004, Austria). Tax exemptions are now being lifted. In June 2007 German sales prices per litre amounted to 71.20 and 71.33 for diesel and rape biodiesel, respectively. In the US, B20 costs roughly 15 to 20 cents-a-gallon more than petrodiesel. In Europe, the price gap between fossil and renewable diesel fuels is less pronounced largely because taxation elevates the price of fossil fuel. The non-competitive price of biodiesel fuel becomes less of an issue when it is used as a B5 blend, and becomes largely irrelevant when used as fuel additive at 0.5–2.0%. For the most part, the cost of producing methyl or ethyl esters from edible oils has always been higher than that of petrodiesel. Without incentives, there are few scenarios where biodiesel can truly be competitive with petrodiesel. USDA has offered incentives for biodiesel production through the Commodity Credit Corporation (CCC) payments, namely US$1.45–US$1.47/gal for soy biodiesel in 2004–06 and US$0.89–0.91 for yellow grease biodiesel. The CCC payments effectively reduce the variable cost of additional soy and yellow grease biodiesel to US$1.10 and US$0.53/gal respectively, in fiscal year 2004. In a comparative study, biodiesel break-even prices (in comparison to petrodiesel) were found to be lowest for SBO and highest for RSO and SNO, with canola falling in between [136]. (N.B. Palm oil had not been considered in this comparison and could well turn out to be the most profitable.) The various technologically feasible processes all have a negative net annual profit, as well as a negative after-tax rate of return (Table 14.22). This calls for suitable government actions. In 2002 the projected cost of biodiesel was higher than that of petroleumbased diesel, namely US$1.40–2.40/gal and US$1.10–1.50/gal, respectively [144]. The higher cost of biodiesel is due to its being produced mostly from expensive high-quality virgin soy oil. US crude soybean oil prices have been in the range of US$0.48–0.57/kg in 2002–05 (with price spikes up to US$0.77/kg oil), which corresponds to a production cost of US$1.50–1.80/ gal of biodiesel. In the US the raw material cost of the conventional biodiesel

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feedstock is thus substantially higher than the finished cost of petrodiesel (spot prices of US$0.80–0.90/gal). The additional cost of biodiesel manufacture from the vegetable oil feedstock accentuates this discrepancy. A breakdown of the retail price of biodiesel is typically as follows: 85% vegetable oil, 12% production and 3% marketing. A 2005 review of 12 economic feasibility studies showed that the projected costs for biodiesel from oilseed or animal fats range from US$1.13 to U$2.60/ gal, including meal and glycerol credits and the assumption of reduced capital investment costs by having the crushing and/or esterification facility added onto an existing grain or tallow facility. Rough projections of the cost of biodiesel from vegetable oil and waste grease are US$2.04–2.34/gal and US$1.28–1.59/gal, respectively. With the corresponding pre-tax diesel priced at US$0.69/gal in the US and US$0.76–0.90/gal in some European countries, biodiesel is then not economically feasible [145]. During 2006 the on-highway petrodiesel price in the US already ranged from US$2.50 to US$3.00/gal. These prices included taxes (20%), cost of crude oil (52%), refining expenses (19%), distribution and marketing (9%). Excluding taxes and distribution, the average price in 2006 was US$1.95/gal with a 73% contribution from crude oil and 27% from refining. At the end of 2006 rising soybean and methanol prices, and declining diesel and glycerin prices shaved about US$0.25/gal off biodiesel profits making the business even less profitable. In comparison, palm biodiesel cost roughly US$2.50/gal, or 30% more than petrodiesel. For palm biodiesel to be competitive with petrodiesel, the price of palm oil should not have exceeded US$1.85/gal. Palm diesel was also not competitive with petrodiesel in July 2005 [146]. At present, the biodiesel industry has hit tough times due to high feedstock costs, quality concerns, lack of legislative support, fickle financiers, razorthin capitalisation of projects, the 2008 Wall Street crash and increasing construction costs with consequent slowdown in construction and production. In the absence of tax relief, there is an urgent need to explore alternative feedstocks for the production of biodiesel. Successful development of a scheme for ester synthesis from less expensive, low-value lipids (e.g. acid oils, tall oil, waste oils) could address the economic barriers to a wider adoption of biodiesel [132, 147, 148], (see also Sections 9.5 and 9.6). Unfortunately, highly acidic feedstocks usually require more process steps (at least according to first-generation biodiesel technology). A key factor in the industry will be near 100% plant utilisation, which is far from the situation in 2008. With high crude oil prices (up to US$140/barrel) and equally high vegetable oil prices, it does not appear that biodiesel can be produced in large quantities at a cost that is competitive with petroleum diesel. Due to the high prices of virgin agricultural crops, tens of kt/yr of biodiesel must be produced for a plant to remain economical. As a result of increased production costs, several biodiesel operations reported losses in

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2007–08. Process models for biodiesel production from various feedstocks and estimates of production costs have been reported [129, 149]. In times of higher and more volatile vegetable oil prices, intensified competition (especially from integrated oilseed operators), emerging technological threats (e.g. renewable diesel fuel), high hardware costs, rapid industrial growth and fairly stable biodiesel prices, investor returns have been impacted negatively. Margins are razor thin to negative. Biodiesel production in Europe using virgin oils is at present an unattractive commercial proposition, as shown in Table 14.29, which refers to 100 kt plants. Many European operations have run at a loss since mid-2007. A number of production facilities in Germany and Southern Europe have ceased operation. For example, one of Germany’s leading biodiesel producers (Campa AG) stopped its 45 Mgy production in Ochsenfurt and put construction of a 60 Mgy plant in Straubling on hold. In time, the free market will sort out the supply and demand situation of the total oils and fats market. Pressure on biodiesel margins are expected at higher production levels and use of larger portions of feedstock supply for biofuel. Under current economic conditions, most biodiesel is not competitive with fossil diesel if one simply compares selling prices. However, if one includes positive externalities, such as impacts related to the environment, climate change, employment, support for sustainable agriculture, social costs due to diseases caused by pollution and trade balance, which are not reflected in Table 14.29 Model cost comparison for biodiesel production in Europe, South-East Asia and the US

FAMEa 7/pmt

RME 7/pmt

Crude vegetable oil Semi-refining cost Cost of semi-refined vegetable oil   (ex refinery) Transportation Cost of semi-refined vegetable oil   (@ biodiesel factory) Methanol (11%) Crude glycerine credit Material cost of biodiesel Variable production costs Out of pocket cost of biodiesel   (ex works) Biodiesel price (ex works) Margin of biodiesel production

537.0 26.1 563.1

573.0 580.0 26.4 599.4 580.0

655.0 32.4 687.4

15 578.1

15 614.4

10 590.0

65 752.4

47.9 –10.0 615.9 50 665.9

47.9 –10.0 652.3 50 702.3

58.3 –16.9 631.4 50 681.4

55.6 –10.0 798.0 65 863.0

639.9 –26.1

679.5 –22.8

720 38.6

894 31.0

a

FAME = 70% SBO, 20% POo, 10% RSO. Based on RBD palm olein. Source: Oleoline®, 9 March 2007. b

PMEb SME US$/pmt US$/pmt

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the price mechanism, the conclusion can be very different. The only biofuels that are price competitive presently are biodiesel produced from soybean oil in Argentina, and bioethanol from sugarcane in Brazil.

14.6

Biodiesel use and markets

In 2007, there were only 20 fossil oil-producing countries supplying the needs of more than 200 nations. At the present time, the world’s biggest biodiesel and bio-based diesel fuel producers are typically Western hemisphere countries with solid infrastructure and abundant capital to subsidise and protect their nascent industries, despite high operating costs. It is expected that by 2010 there will be some 100 biodiesel-producing nations and suppliers. The biodiesel market can be divided into separated segments (in some countries imposed by law): ∑ self-consumption (farmers and co-operatives for own use); ∑ domestic demand (mandated or not); and ∑ export markets. Biofuels are no longer produced and used locally, such as bioethanol in Brazil. In recent years, this pattern has changed in Europe by imports of biodiesel from the US and Argentina, and exports of vegetable oils to northern Europe (UK, Finland, Netherlands). The trade situation has largely come about as a result of tax policies. Bio-based diesel fuel can be used in various ways: ∑

as a biocomponent (several per cent) to a fossil-diesel fuel (common approach for bio-esters); ∑ as blends of tens of per cent of biocomponent with a fossil-diesel fuel (as in the case of HVOs); or ∑ as pure biodiesel or HVOs in fleet operations. Most OEMs only approve biodiesel use in blends up to 5%. Niche markets for biodiesel are bus fleets for public transport, truck operators and non-road applications (mining, forestry, construction and agricultural vehicles), which are able to utilise high-level blends or pure forms of biodiesel. In addition to being an alternative motor fuel for freight and transportation fleets, the marine, farming and rail industries, biodiesel has other fuel or fuelrelated applications [150]. Biodiesel has been proposed as a cetane improver and as an aviation fuel. When employed at levels of over one per cent in ultra-low sulphur diesel (ULSD) blends, biodiesel restores lubricity through its anti-wear action on engine injection systems. Future technologies, such as ultraclean diesel engines or fuel cells, represent further opportunities for biodiesel. A predicted growth area of bio-based diesel is the aviation industry, where the first commercial (Virgin Atlantic) flight using biofuel (5% babassu

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Biodiesel science and technology

biodiesel in jet fuel) took place in February 2008. Test flights using biofuels were also carried out by Continental, JAL and Air New Zealand. However, current commercial processes for producing biodiesel yield a fuel that is unsuitable for military applications, in contrast to petroleum-derived JP-8. Biodiesel is 25% lower in energy density than JP-8 and exhibits unacceptable cold-flow properties at the lower extreme of the required JP-8 operating regime (228 K). The key standards to accomplish are freeze point, flash point, energy content, density and stability. Renewable jet fuel is more likely to be based on subjecting animal fats or vegetable sources to hydrogenation and aromatisation to make alkanes and aromatics that can be distilled and combined into jet fuel (see also Section 15.5.2). Other markets for FAME include home heating and industrial (refinery) boiler fuels, biosolvents, herbicide adjuvants and consumer products. Heating oil is a marginal market for biodiesel (up to 1 Bgy in the US appears possible). Biodiesel can be used as a blend or as a neat fuel for generation of electricity in diesel generator sets and gas turbine applications. While lower-grade fuel (not meeting ASTM specifications) cannot be used in a diesel engine, offspec biodiesel can be burned in a turbine engine for electricity generation, thereby taking full advantage of the fuel’s clean-burning properties [151]. Methyl esters can also be utilised as intermediates in the production of fatty alcohols (surfactants) from vegetable oils. Vegetable oil esters (e.g. SBME) also possess good solvent properties and are attractive as cleaning agents and plasticisers. The biodiesel industry was born almost 15 years ago in Germany, France and Italy and was originally meant to serve a dedicated market close to the producer. In 1995 about one-third of the world production of biodiesel was located in Leer, Germany, with a 35 Mgy industrial plant based on the socalled CD Process System Connemann-ADM. In 2008 global production exceeded 12.7 Mt (12.5 Mt expected for 2009). Biodiesel production capacity has quadrupled between 2001 and 2005 with a plant build rate implying further doubling from 2006 to 2008. The industry has not reached its maturity yet and is in a state of presumed further expansion. However, at present the biodiesel industry is faced with an overwhelming surplus of nameplate capacity (37.9 Mt in 2009). The US biodiesel industry is operating at 35–40% of capacity, and the EU at about 50%. In the short term the biodiesel industry is heading for consolidation unless there is an increase in mandates or feedstock costs come down. Biodiesel is considered to be a compelling business for the rendering industry [152]. Table 14.30 shows predicted annual increases in biodiesel production. Global biodiesel demand is expected to grow by 15%/yr to 85 Mt by 2020 [152a]. In the short term at least 11 countries (Germany, France, Italy, UK, Spain, Netherlands, US, Argentina, Brazil, Indonesia and Malaysia) are expected to exceed a production of 1 Mt/yr.

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Table 14.30 Predicted annual increases (Mt) in biodiesel production (after ref. [153]) Producer

2008–10

2011–15

EU USA South America Asia-Pacific World

1.7 0.8 1.1 1.1 5.0

1.2 0.4 1.1 1.4 4.7

Apart from overcapacity, other hindrances to the global bio-based diesel market include feedstock supply (and high cost of the main commodities RSO, SBO and PMO), trade blocks, internationally varying quality standards, unclear analytical tools (LCA), lack of investment in next-generation biofuels, infrastructure and the food-fuel dilemma. Annual increases in vegetable oil supply are about 4 Mt for food use and 2 Mt for non-food use, which would set the annual requirement at 6 Mt more each year. The question whether oils and fats will be used for fuel rather than food is affecting current world vegetable oil market prices. Given the total EU and US biodiesel nameplate capacity of about 25 Mt/yr by mid-2008 with some 400 largely under-utilised plants and the expected ROW (mainly Brazil, India, China and South-East Asian countries) capacity anywhere between 5 and 15 Mt/yr, forecasts for 1000 operating plants by 2012 might be over-optimistic in view of the recent steep rises in vegetable oil prices on the world market and the financial crisis. In the future, profitability of biodiesel plants might be determined by the added value of the by-products (glycerol, meal, salts, nutraceuticals) rather than by biodiesel itself.

14.6.1 On-farm biodiesel processing and use It is often easier to find biodiesel in rural areas than in cities. The possibility that farmers who grow biodiesel feedstocks can also benefit by producing and using biodiesel on-farm is of considerable interest. Many farmers who raise oilseeds use a biodiesel blend in tractors and equipment as a matter of policy to foster production of biodiesel and raise public awareness. Most European manufacturers (Case, Deutz-Fahr, Fendt, Fiatagri, Ford, John Deere, Lamborghini, Lindner, Massey-Ferguson, Mercedes-Benz, Same, Steyr, etc.) offer biodiesel-compatible tractors. On-farm production and use could enable farmers to be more self-reliant in fuel, and would diminish fossil fuel costs. On-farm crushing capacity could also be used to crush oilseeds for other growers, making the operator a net seller of oil or biodiesel. An interesting example of self-consumption is Barrálcool’s integrated bioethanol/biodiesel plant (see Section 11.4).

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The economies of scale suggest, however, that the cost per gallon for small-scale crushing and processing are significantly higher than for larger operations. At or below 0.5 MMgy, crushing and processing costs are likely to be more than US$1/gal higher than for consolidated operations of 5 or 10 MMgy [112]. The reasons for scale economies include the higher maintenance cost on small-scale equipment such as presses to crush oilseeds, and the fact that capital costs generally rise more slowly than the volume of production as the scale of operation is increased. There are limits to trade-offs between capital and labour and larger-scale operations tend to be able to take the greatest advantage of substituting relatively low-cost capital for relatively high-cost carbon. Brazilian and Argentinian biodiesel reflect this duality.

14.6.2 Europe Garofalo (EBB) [154] has recently given an overview of the European biodiesel industry. Most biodiesel in the EU is used in urban public bus and truck fleets and increasingly so also in private cars (as blends to petrodiesel); all French public urban buses consume ecodiesel containing 30% biodiesel (Diester®; contraction of Diesel and ester). It is also utilised to fuel farm equipment and as a heating fuel, solvent, hydraulic oil and lubricant. The years 2005 and 2006 have experienced unprecedented growth in global biodiesel demand, production and nameplate capacity (see Table 14.31 for Europe). The total biodiesel capacity of the EU15 amounted to 2.25 Mt in 2004, located mainly in Germany, France and Italy, and has rapidly been extended to a EU25 capacity of 6.2 Mt by July 2006 and in excess of 16 Mt for the EU27 by mid-2008. The increasing demand has been met by the traditional domestic feedstocks (RSO, SNO) and imports. At present, biodiesel accounts for only around 1% of total road fuel in terms of energy content in the EU compared to the use of a 10% ethanol blend in nearly half of all petrol sold in the US. The popularity of biodiesel in the EU derives from various factors, including tradition, use in existing vehicles with little or no adaptation, vast acreages of farmland for targeted vegetable oil production, EU legislation and (past) tax policy. Most biodiesel in the EU is processed from RSO (West and Central Europe) and high-oleic SNO (Southern Europe) with a growing percentage of recycle frying oil (see Table 14.31); SBO and PMO are blended in summertime. Lack of raw materials, recent droughts and high oil prices have had a specific effect on biodiesel production in Southern European countries. If rapeseed is to remain the main European feedstock, the EU will have to double its domestic production or else resort to imports to meet its biodiesel targets. At present, feedstock for a European biodiesel plant consists on average of 60% RSO, 20% SBO, 10% SNO, 5% PMO and 5% UCO/TLW. Both biodiesel and bioethanol are currently produced in the EU almost

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exclusively from agricultural feedstock. Production figures (2006) for the EU27 were 4.9 and 1.2 Mt, respectively. A total of 5.6 Mtoe of energy crops were harvested in Europe in 2006. However, the production of transport biofuels from agricultural feedstock is constrained by various factors such as restrictions on feasible land availability, strong competition with other prime applications of agricultural land (e.g. for food and feed production), cultivation specifics of biofuel crops (e.g. long crop rotation periods, rather limited biofuel yield per hectare, typically 1300 L ha–1 for rape biodiesel), etc. Furthermore, oilseed crops like rapeseed and soybean are not selfcompatible; therefore, their cultivation requires a frequent crop-rotation regime. In consequence, biodiesel based on oilseed crops will probably not be able to substitute more than 5–15% of petroleum-based diesel in the future. Although the EU27 on average have succeeded in their biodiesel targets for 2007 (though not for all countries taken individually and even less so in terms of biofuels as a percentage of all transport fuels) (see Tables 1.2 and 14.31), broader use of biodiesel is hampered mainly by the extensive acreage required for sufficient production of oilseed crops. The French Agency for Environment and Energy Management (ADEME) estimates that the 2010 objective would require industrial rapeseed plantings in the EU to increase from 3 Mha (2003) to 8 Mha [155]. EU oilseeds production is not expected to meet the necessary growth rate to reach the desired targets in the long term (see Sections 5.2 and 5.3). This calls for increasing imports. Alternative feedstocks for EU biodiesel production are non-EU RSO (imports from Russia and Ukraine) and other vegetable oils, notably SBO, SNO and PMO (see Tables 14.31 and 14.32). Eastern European biodiesel production is booming. In the near future, some 10–15% of European biodiesel is likely to be palm oil-based. EU 2007–08 production statistics show restrained growth due to market conditions (higher costs for rapeseed, higher taxes, overcapacity) and competition from biodiesel imports (in particular 1 Mt of US B99 in 2007). Production increased from 4.9 Mt in 2006 to 5.7 Mt in 2007. Growth figures in 2007, 2006 and 2005 were 16.8%, 54% and 65%, respectively, compared to the previous year. Biodiesel production has decreased in six member states since 2006 and has stagnated in many other countries (see Table 14.31), in contradiction of EU objectives. EU biodiesel production figures in early 2009 were back to 2006 levels. Table 14.31 shows the present mismatch between biodiesel production and capacity in Europe. Installed plant capacity increased by 55% in 2007, to 16 Mt nameplate capacity in 2008, of which at least 6 Mt will be idle due to lack of a viable market. The number of EU plants as of July 2008 was 241, compared with only 70 in 2004. A biofuel capacity of 34 Mt is needed by 2020. Expectations of EU biodiesel production range widely from 11 Mt [153] and 13.9 Mt (Eurostat) in 2010 to 10 Mt/yr in 2011 (Frost & Sullivan) with

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Biodiesel science and technology

Table 14.31 Country-by-country European biodiesel production (2006–07) and nameplate capacity (2007–08) Country

Production (kt)

Nameplate Feedstockb capacity (kt)a



2006 2007

2007 2008

Germany 2662 2890 4361 5302 70% RSO (d,i); 20% SBO, PMO (i); 10% UCO (d), TLW (d) France 743 872 780 1980 RSO (d,i), SBO (i), SNO (d), UCO (d), TLW (d) Italy 447 363 1366c 1566c 70% RSO (i); 20% SBO (i), SNO (i), PMO (i) UK 192 150 657 726 RSO (d), UCO/TLW (d), SBO (i), SNO (i) Austria 123 267 326 485 RSO (d), UCO (d) Poland 116 80 250 450 RSO (d) Czech Republic 107 61 203 203 RSO (d), UCO Spain 99 168 508 1267 PMO (i), SBO (i), SNO (i), UCO (d) Portugal 91 175 246 406 SBO (i), SNO (d, i), algae (i) Slovakia 82 46 99 206 RSO (d) Denmark 80 85 90 140 Greece 42 100 440 565 70% SBO (i); RSO (i), CSO (d), UCO (i) Belgium 25 166 335 665 Netherlands 18 85 115 571 RSO (i), SBO (i), UCO, TLW, PMO (i) Sweden 13 63 212 212 RSO, tall oil (d) Slovenia 11 11 17 67 RSO (d) Romania 10 36 81 111 RSO (d), SNO, SBO Lithuania 10 26 42 147 RSO (d) Latvia 7 9 20 130 RSO Bulgaria 4 9 65 215 UCO (d), TLW (d) Ireland 4 3 6c 80c RSO, TLW (d), UCO (d) Malta 2 1 8 8 UCO (d) Cyprus 1 1 6 6 RSO (i), SNO (i) Estonia 1 0 35 135 c 170c PMO(i), RSO(i), TLW Finland – 39 Hungary – 7 21 186 RSO, SNO Luxemburg – 0 – 0 Turkey n.d. n.d. n.d. n.d. SNO (d), CSO (d), CO (d), RSO (i), algae Serbia/ n.d. n.d. 40 100 RSO (d), SNO (d), SFO (d) Montenegro Norway n.d. n.d. n.d. 100 MFT (d) Total 4890 5713 10 329 16 100 a b

1 July 2007 and 1 July 2008; 5% variance. d, domestic; i, import.

c Additional hydrodiesel capacity. Source: European Biodiesel Board.

a 20% share of biofuels (biodiesel, ethanol, methanol and gas) in 2020. This requires an annual growth percentage as from 2007 of at least 20%. However, current market conditions for the European biodiesel industry are unfavourable.

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Table 14.32 EU27 biodiesel sources (Mt) Source

2005

2010

2015

Rapeseed oil Other domestic (EU) oils Imported oils Imported biodiesel

2.5 0.6 – –

5.0 1.0 1.0 4.0

6.0 1.0 2.0 6.0

Total

3.1

11.0

15.0

The German tax holiday for biodiesel, which lasted several years, has led to biodiesel capturing 12% of the German fuel market, compared with less than 1% for the EU as a whole. Germany had 1900 biodiesel fuel stations in 2005. Consumption kept pace with production until 2007. In 2007 consumption by trucks made up over 50% of Germany’s 3.3 Mt of pure biodiesel sales. Germany’s biodiesel industry has peaked, capacity has grown very quickly and outstripped production (2.8 Mt in 2008). The country’s biodiesel capacity has risen to over 5 Mt by mid-2008, corresponding to 17% of total diesel consumption (29 Mt). Recently, Germany’s biodiesel production has been undermined by an increase in price of rapeseed and the introduction of an unfavourable taxation system (70.09/L in 2007 increasing yearly by 70.06/L to reach 70.45/L by 2012), meaning that biodiesel will become just as expensive as regular diesel. As a consequence, German biodiesel producers have been directed towards lower-priced raw materials, such as soybean or palm oil (in summer blends). The higher German taxes have made biodiesel uncompetitive in the road haulage sector where it had been gaining share as an unblended fuel because of its high cetane number or combustion quality. Demand for biodiesel in Germany dried up almost instantaneously, now not exceeding 2% of the German fuel market. In 2008, only 250 biodiesel filling stations were left. At the same time, there have also been large imports of US B99 biodiesel, which benefits from a US$1/ gal tax credit. The inadvertent combination of US and German tax policies has led to a collapse of the thriving German biodiesel industry [156]. Total sales of biodiesel (domestic or import) in Germany fell from 3.3 Mt in 2007 to 2.8 Mt in 2008, while sales of bioethanol rose from 460 kt to 625 kt. It is estimated that about 30% of Germany’s biodiesel plants, mainly small producers, were idle in 2008. Large companies are still producing but way below capacity or temporarily halted production (e.g. Petrotec AG, 160 kt/ yr). As of January 2009 a legally specified overall quota (B7) is in force for biofuels, aimed at guaranteeing a minimum level of blend sales. A further fall in the biofuels share to fuel supply in Germany is not expected. It is of considerable interest to compare the development and current biodiesel situation in Germany and the UK in view of contrasting national socio-political contexts (see Table 14.33). Germany is the leading EU producer

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Table 14.33 Biodiesel from Germany and the UK (after ref. [157]) Descriptor

Germany

UK

Domestic industry Leading (> 1993) Underdeveloped,   inexperienced (>2002) Biodiesel plants 39 (2006) n.g. Biodiesel plant capacity 4361 kt/yr (1 July 2007) 657 kt/yr (1 July 2007) Feedstock RSO (domestic) WVO, RSO (domestic);   VOs (import) Market Leading EU consumer; B5; no B100 market   trucks (B100) 300¥ Required market expansiona 3¥ Government Consistent support (>1990s) Ambiguous support Transport fuels strategy RTFO Excise duty exemption Excise duty reduction   (expiring)   (until 2008) Trade associations Strong (VDB, UFOP, MWV) Weak (REA, ABI) Oil companies Supportive Wait-and-see Technology providers Active Passive Automobile manufacturers Active Passive General public No active role Uninformed Environmentalists Strongly opposed Supportive a

Expansion needed to meet indicative EU biofuels target of 5.75% by 2010.

and consumer. Most of the biodiesel is produced domestically from RSO with some imports and only negligible exports. Consumption of biofuels in Germany (until 2004 only biodiesel) needs to expand by a factor of 3 to meet the EU biofuels target of 5.75% in 2010. In the UK biodiesel production started only in 2002, mainly from WVO. The country had set itself a modest target of 0.3% by 2005. Bioethanol was not used for transport until 2005 but is now more important than biodiesel. No bioethanol is being produced in the UK; imports are predominantly from Brazil. The biofuel consumption needs to expand by a factor of 300 in order to meet the 2010 target. The main regulatory frameworks supporting the biodiesel industry in Germany are the transport fuels strategy [158] and initial excise duty exemption (as from 2004). The potential for biodiesel blends is limited by land availability. In Germany, biodiesel is viewed as an important energy source for environmental reasons and energy security, as well as a way to support the agricultural industry and regional development. Leading environmental groups in Germany (BUND, UBA) are extremely critical of biodiesel. The main regulatory frameworks in the UK are the transport biofuels strategy (RTFO) and excise duty reduction (from 2002 until 2008). Imports of biofuels dominate the market in the UK without creating opportunities for British farmers [159]. Environmental groups in the UK support biofuels conditionally. There is considerable cooperation in Germany between the biodiesel

Sustainability and use of biodiesel

685

industry, oil companies and automobile manufacturers, which is facilitated by the trade organisations (VOB, UFOP). Oil companies are generally critical of first-generation biodiesel, which is viewed as contributing insignificantly to energy security, in contrast to developing second-generation biofuels and hydrogen [160]. The German market for biodiesel (B100) is shifting to trucks. On the contrary, there is no market for B100 in the UK and all biodiesel is utilised for blending. The UK biodiesel industry is not highly organised. With petrol surplus and diesel shortage in the UK, oil companies favour support for biodiesel over bioethanol. First-generation biodiesel is viewed as a short-term product as opposed to second-generation biodiesel [161]. Although it appears that the UK has made a late start, the country is exceeding all EU targets for 2008. Biofuels accounted for 2.61% of the total fuel supply (exceeding the yearly target of 2.5%). Biodiesel accounted for approximately 84% of biofuels used, 25% of which was produced using American soybeans as feedstock. Scotland intends to increase its biodiesel usage from less than 1% to 10% by 2020, using mainly European sunflower and imported palm oil. Most recently, investment in the UK is growing. In Cardiff (South Wales), Flex Fuels Energy Ltd is building a 60 MMgy biodiesel plant using 80% RSO/20% SBO. Meanwhile, most of the UK’s biodiesel capacity has shut down due to large subsidies to US biodiesel producers. Ireland collects about 7 kt/yr used vegetable oil. Its potential for biodiesel production has been evaluated [162]. Ester yields were low, total glycerol concentrations high and low-temperature properties unsuitable for winter use. Currently, biodiesel constitutes about 2% of the total French diesel consumption. Recently, France cannot produce the amount of rapeseed necessary to process the quantities of biodiesel to fill the 2008 quota (2.3 Mt), especially as the food industry also needs rape oil. 2.3 Mt of RME would require 1.6–1.9 Mha of planted rapeseed, depending on yield [163]. France’s maximum acreage of rapeseed, based on agronomic constraints, is 1.5 to 1.8 Mha. In 2005, French rapeseed acreage was 1.2 Mha, including 450 kha for industrial rapeseed. Alternative supplies are RSO and SBO (import), SNO and animal fats (domestic). Total French nameplate capacity was almost 2.0 Mt by mid-2008. Diester Industrie is planning to extend its production capacity to 1433 kt by 2007–08. French production amounted to 1815 kt in 2008. Italy’s biodiesel production is based mainly on imported RSO (70%) and SBO (20%). The impact of biodiesel production on Italian agriculture is negligible. In fact, Italian production has declined in 2007 following the reduced biodiesel tax relief in 2005. Italy produced 595 kt in 2008. In Spain transport accounts for about 40% of primary energy consumption. Road fuel consumption shares of diesel and gasoline in Spain are about

686

Biodiesel science and technology

80% and 20%, respectively (end 2007). Spain provides a tax exemption for commercial biofuels production until 2012 (Act 53/2002). The country did not reach the 2% share in 2005, with a total liquid biofuels production of 137 ktoe (of which 113 ktoe was bioethanol and 24 ktoe biodiesel), or 0.44% of total consumption of fuels for transport. Although biodiesel production capacity has increased by 400% from about 96 kt/yr (2003) to 358 kt/yr (2006), production has been lagging behind (from 6 kt in 2003 to 99 kt in 2006 and 207 kt in 2008), and is being used equally for internal consumption and the export market (Portugal). Capacity coverage in 2006 did not exceed 35%. Meanwhile, the capacity has further increased. Table 14.34 lists biodiesel plants in Spain by the end of 2007; 23 plants account for a total nameplate capacity of 921 kt/yr. As internal biofuels consumption in Table 14.34 Biodiesel plants in Spain (at end 2007) Plant Location Province Bionorte San Martin del   Rey Aurelio Idae Alcalá de Henares Transportes Ceferino Vilafant   Martinez Bercam Los Yébenes Biocarburos del Almanzora Almanzora   (Biocarsa) Biocom Pisuerga Castrojeriz Grupo Ecológico Natural (GEN) Llucmajor Biocemsa Elda Biocarburantes de Castilla Cuevas del   (Biocast)   Valdescorriel Bionor Transformación Berantevilla Stocks del Vallés BDP Montmelo Biocarburantes Almadén Almadén   (Grupo Activos) Biodiesel Andalucia 2004 (BIDA) Fuentes de Andalucia Biodiesel Castilla-La Mancha Santa Olalla   (Biodiesel CLM) Combunet Monzón Bionet Europa Reus Ecoproma Montalbo Montalbo Entabán Biocombustibles Sevilla   del Guadalquivir Biodiesel Caparroso EHN Caparroso   (Acciona Energia) Combustibles Ecológicos Biotel Barajas de Melo Linares Biodiesel Technologies Linares Biocarburantes CLM (Natura) Ocaña Biocom Energia Algemesi Total

Capacity (kt/yr)

Asturias

4

Madrid Girona

5 5

Toledo Almeria

6 6

Burgos Baleares Alicante Zamora

8 16 20 20

Alava Barcelona Ciudad Real

30 31 32

Sevilla Toledo

36 45

Huesca Tarragona Cuenca Sevilla

50 50 50 50

Navarra

70

Cuenca Jaén Toledo Valencia

72 100 105 110



921

Sustainability and use of biodiesel

687

Spain grew by only 66% from 2003 to 2006, commercialisation of biodiesel is the real bottleneck, which suffers from: ∑ lack of support from the petrol companies to use direct blending; ∑ logistics; and ∑ lack of confidence on biodiesel quality. Objectives for biodiesel within the Spanish Renewable Energy Plan 2005–10 are 1440 ktoe biodiesel (3.8% market share), to be derived from 1022 ktoe vegetable oils and 300 kt used vegetable oils. Finland, with NExBTL production from Neste Oil, is emerging as a major producer/exporter of renewable diesel (non-ester bio-based diesel). Other noteworthy developments are taking place in the Netherlands which aims at becoming a major European biodiesel manufacturer. According to the Netherlands Biodiesel Industry Association (VNBI), biodiesel manufacturers (Biodiesel Amsterdam, Biodiesel Kampen, Biopetrol Rotterdam – now idle, Biovalue Holding, Clean Energy, Dutch Biodiesel, J&S BioEnergy, Rosendaal Energy and SunOil Biodiesel) will produce 1.5 Mty, thus replacing at least 10% of the country’s mineral diesel by 2009. Rosendaal Energy (Sluiskil), laid out to produce 250 kt/yr biodiesel as from January 2009 using Ukrainian rapeseed oil and able to also handle UCO, TLW and jatropha oil recently filed for bankruptcy. Belgium is extending its nameplate capacity with 380 ML/yr of biodiesel (Néochim, Oleon – now Sofiproteol, Proviron and Flanders Bio Fuel) and 250 ML/yr of bioethanol (Bio Wanze, Alco Bio Fuel and Tate & Lyle); this production will reduce fossil fuel needs by 6%. Austria operates 11 biodiesel plants but not at full capacity. In Romania Ulerom Vaslui/Greenline Industries operates a 25 kt/yr facility using upgraded RSO, SNO and SBO. The country plans production of 400 kt rape biodiesel using 500 kha. Russia, Ukraine and Belarus and other Eastern European countries (e.g. Romania and Poland) have huge potential to develop highly competitive biodiesel (and biethanol) industries, particularly aimed at exports. Russia alone has about 40 Mha of unused arable lands which could be used for energy crops without affecting food production. In addition, there is the potential to raise farm productivity, which is currently half that in most EU countries. European biodiesel producers are severely affected by a flood of subsidised US imports. Low-cost supplies of Latin American soy and South-East Asian palm biodiesel are being shipped to the US for blending with conventional diesel in US shore tanks or indeed in vessels at US ports in order to qualify for a tax credit of 99 cents per gallon (US$298/pmt), and then re-exported to Europe. Out of a total export of 1 Mt in 2007, 600 kt was sold in Germany. The ‘splash and dash’ provision has even induced European producers to ship fuel to the US, qualifying for the blenders credit and then re-exporting back home. To end the unfair and unsustainable trade practice, which allows

688

Biodiesel science and technology

sales of US originated biodiesel in Europe at a price below the EU industry’s raw materials costs, urgent WTO arbitration has been requested [164]. For comparison, US B99 blends are sold in Germany at US$2.78/gal whereas the domestic cost of production of biodiesel amounts to US$3.34/gal. Early 2009 the EU commission has released its findings concering EBB’s allegations that export from the US has destroyed the European biodiesel industry. As a result, on 13 March, 2009 EU has enacted temporary anti-subsidy tariffs (approximately US$270 to US$300/Mt) on biodiesel imported from the US. Recently, the US Energy and Tax Extenders Act of 2008 (H.R. 6049) has shut down the ‘splash-and-dash’ loophole. Moreover, EU producers are currently also negatively impacted by EU and national policies. In the current economic climate many biodiesel investment plans are being shelved. For example, Ineos shelved plans to build four large-scale biodiesel plants across Europe (in Belgium, France, Germany and Scotland) as a result of the financial crisis in autumn 2008.

14.6.3 North America Most of the diesel fuel sold in the US goes to over 200 major fleets operating heavy-duty vehicles used in transport, agriculture, and other industries requiring large machinery. US biodiesel markets comprise urban transit, governmental/ regulated fleets (e.g. US Postal Service, Army, NASA, etc.), marine (e.g. US Navy), and underground mining. Biodiesel, mostly EcoDiesel B20, is now being used in federal, state and transit fleets, municipal and school buses, private truck companies, ferries, tourist boats and launches, locomotives, power generators, some heating furnaces, and other equipment. B2 use is more limited. Regulated fleets are being rewarded for implementing biodiesel use into their heavy-duty vehicles. The biodiesel industry in the US has recently experienced explosive growth with an increase in production of 25 Mgy in 2004 (or a minor fraction of EU production) to 698 Mgy in 2008. Several factors have contributed to this heightened interest: ∑

considerable reductions in production cost as a result of feedstock diversity (from US$4.50/gal in 1997 to US$1.00/gal in 2001); ∑ EPAct amendments (alternative vehicle incentives for blends of biodiesel that exceed 20% in diesel fuel); ∑ subsidised US methyl ester (B99) exports to the EU; ∑ low toxicity; and ∑ high lubricity. US regulations aim at stimulating production rather than consumer demand. On 23 Sept. 2008, the US Senate passed a bill that extends the biodiesel tax credit (until 31 Dec. 2009). The high volume of US biodiesel exports has

Sustainability and use of biodiesel

689

been fuelled by a weak dollar, loopholes regarding the US federal blenders’ credit (now closed) and strong European incentives. Table 14.35 shows the development of biodiesel projects in the US. The US biodiesel industry has invested heavily in some 100 new plants in the period 2006–07. In 2006, 88 US biodiesel plants had a combined capacity of 864 MMgy. In October 2007, US production capacity was reported as 1.85 Bgy (6.2 Mt/yr) for 165 plants (average plant size 11.2 MMgy) with another 1.38 Bgy (4.6 Mt/yr) under construction or in expansion (84 plants, average plant size 16.3 MMgy). In Sept. 2008 at least 31 US operations (with average and total capacities of 13 and 409 MMgy, respectively) were idle. The number of biodiesel projects (construction or expansion) in the US has recently decreased significantly to only 19 in spring 2008 and a mere 13 in Sept. 2008. The reasons for this steep decline are several, including skyrocketing cost of No. 2 diesel (US$3.88/gal in April 2008, or 30% higher than in March 2007), and high soy oil prices (US$0.56/lb in July 2008) causing soy biodiesel to be produced at US$6/gal. While on-road diesel fuel prices, which averaged US$3.79/gal in 2008, are projected to average US$2.28/gal in 2009 and US$2.55/gal in 2010, the advent of the financial crisis will not improve biodiesel plant construction activities. US diesel plant construction lists can regularly be found in Biodiesel Magazine (see Table 14.36). By October 2009, some 1650 US retail pumps offered biodiesel, with 645 outlets for B20 or higher. In March 2009 almost all US states (except for AK, ME, MT, UT, WY) Table 14.35 Development of biodiesel projects in the United States Yeara Proposed

Plants under construction

Total capacity (MMgy)

2005 2006 2007 2008

17 31 51 13

n.g. n.g. 1420 219

a

36 65 94 27

Monthly average.

Table 14.36 US biodiesel plant map Plant statusa

Number

Nameplate capacity (MMgy)

Operating plants Plants under constructiuon Plants under expansion Idle plants Unconfirmed plants

113 (85) 12 (10) 1 (3) 31 (32) 21 (62)

1853 (1382) 347 (162) 1 (4) 409 (507) 392 (939)

a

As of 24 Sept. 2008 (16 March 2009). Source: Biodiesel Magazine.

690

Biodiesel science and technology

had biodiesel production units installed. The top 10 North American biodiesel producing states are TX, IA, MO, WA, MS, NY, OH, NV, AR and IL, with an installed capacity (Sept. 2008) in the leading biodiesel-producing states, Texas and Iowa, of about 336 and 328 MMgy, respectively. The typical US biodiesel producer is located in Central USA (IA, IL, MO). Texas Gulf biodiesel operations are most significant. Major challenges for the Texan biodiesel industry include: air quality (NOx); expiration of state production incentives; and virtually a complete lack of local demand for biodiesel. Minnesota aims at being a top renewable fuels state and was the first to require a biodiesel blend (B2 as from Sept. 2005). In May 2009, Minnesota will boost its blend requirement to B5, and gradually up to B20 by 2015 (mandatory for seven months a year, with a fallback to B5 during winter). Legislation requires that 5% of the mandated fuel comes from non-food feedstocks, such as algae, waste oils, tallow, and at some point even cuphea and industrial hazelnuts that are currently being researched in the state. Minnesota’s current biodiesel production capacity exceeds 64 MMgy, more than enough to meet the 5% mandate that would require approximately 40 MMgy. Most of the biodiesel produced in the US was originally made either from virgin or used cooking soybean oil; more occasionally canola, animal fats, yellow grease (primarily recycled cooking oil from restaurants) or multifeedstocks (SBO/CO, SBO/CSO, SBO/CRO) were used. This situation is now changing. While the US biodiesel production in 2007 was based on refined SBO (78%), crude SBO (18%), inedible tallow and yellow grease (4%) and CSO (< 1%), North American biodiesel feedstocks in spring 2008 were soy oil (45%), multi-feedstock (39%), animal fats/soy (3%), animal fats (3%), canola oil (4%) and other (6%) [165]. However, quantitatively still the same amount of soy oil has been converted to biodiesel. Many plants, originally laid out for SBO as their primary or exclusive feedstock, have now changed to a multi-feedstock programme (including SBO). Out of the 27 biodiesel projects in 2008, which on average will require one year to completion, most are planning to process multiple feedstocks, only five will use soy oil, five others are lined out for animal fats and other oilseeds (canola), and two projects (Raccoon Valley Biodiesel, Storm Lake, IN; BioPower USA LLC, Knoxville, TN) are algae-based (from undisclosed source). The number of plants using multiple (more than two) feedstocks has recently (autumn 2008) increased to 55%, overtaking those dedicated or restricted to soy oil only (30%). Various major US metropolitan areas, including San Francisco, Los Angeles, New York, Seattle, Portland, Denver, Atlanta and Austin are committed to using waste cooking oil as a fuel source for city fleets. As indicated in Section 6.4.6, besides domestic production, alternative feedstocks for the US biodiesel industry could be imported (mainly palm and coconut oil, and jatropha in the future).

Sustainability and use of biodiesel

691

The installed capacity requires adequate domestic and global supplies. Biodiesel plants are projected to use 2.2 billion pounds or 12% of the total US soybean oil production for 2008–09 (18.4 billion pounds), not dissimilar from 2007/08 (cf. up to 30% of corn for ethanol). While soybean oil supplies are high, so are prices. Recent plant start-ups raise several feedstock questions. In the US biodiesel plants are now being developed mainly as large conglomerate entities (60–100 MMgy) (see Table 14.37). The feedstock, mainly oils from virgin crops, is transported to the plants from across many states. The produced fuel is then transported back to widely dispersed distribution depots and over 50% is being exported, mainly to Europe. Imperium Renewables started (at reduced capacity) one of the largest overall US biodiesel production units at its 100 MMgy (335 kt/yr) multi-feedstock facility in Aberdeen, WA. What is predicted to be the world’s largest fully integrated 80 MMgy (270 kt/yr) soy-based biodiesel plant, operated by Louis Dreyfus (LD Commodities) in Claypool, IN, can process more feedstock than Indiana state can provide. Similarly, Archer Daniels Midland’s (ADM) 85 MMgy (285 kt/yr) plant in Velva, ND, is the largest canola-based biodiesel operation in the US, and needs 700 kt of seed, i.e. more than 100% of North Dakota’s canola supply. While such large plants continue to get on stream, the US biodiesel industry is operating far below capacity. One reason for this is the increase in vegetable oil prices. Actually, the need for large dinosauric production units in the current US market is rather non-existent and consequently these facilities are not doing well. Dozens of biodiesel producers have plants that are going out of business or sitting idle. Green Country Biodiesel Inc., Chelsea, OK, and others, have already filed for bankruptcy following rising soybean prices, and Table 14.37 Top 10 largest US biodiesel plants (March 2009) Company Location

Nameplate Feedstock Statusa capacity (MMgy)

Metro Bio Fuel New York City, NY 110 MFT GreenHunter Biofuels LLC Houston, TX 105 MFT Imperium Grays Harbor Grays Harbor City, 100 MFT   WA Biodiesel of Las Vegas, Inc. Las Vegas, NV 100 MFT Green Earth Fuels LLC Houston, TX 90 MFT Archer Daniels Midland Co. Velva, ND 85 Canola Delta Biofuels Inc. Natchez, MS 80 SBO/TLW Louis Dreyfus Agricultural   Industries LLC Claypool, IN 80 SBO Nova Biosource Fuels Inc. Seneca, IL 60 MFT Twin Rivers Technologies Cincinnati, OH 60 MFT   Natural Ingredients LLC a

1 2 3 4 2 5 5 5 6 2

Key: 1 under construction; 2 unconfirmed; 3 reduced capacity; 4 suspended; 5 operating; 6 filed for bankruptcy.

692

Biodiesel science and technology

more might follow. Also Nova Biosource Fuels Inc. (Seneca, IL), a cheap feedstock-based producer, has been affected. US industry might be heading towards containerised biodiesel production modules with a capacity between 2 MMgy and 5 MMgy. The United States (total area = 2.3 billion acres) has 450 M acres of land for growing crops for food and animal feed, and 580 M acres for grassland pasture and range. A record of 3.2 billion bushels of soy crop were produced in 2006. Expanding soy oil will drive down prices in the animal feed markets and therefore limit the supply potential. According to USDA, in January 2007 some 202 million pounds of all oils and fats were used for biodiesel (< 8% of total oil and fat consumption), as compared to 392 million pounds (or 13% of total consumption) six months later. In the rush for ethanol, US farmers are now expanding corn-growing areas at the expense of soybean. The competition brings the food vs. fuel debate into sharp focus, as more arable land in the US is used for fuel crops than for food at a time when global food demand is increasing strongly. Conversion of 20% of US corn produced 5 billion gallons of ethanol in 2006, equivalent to only 2.6% of total transportation fuel use. The US drive to encourage ethanol production from corn is much criticised. The provenance of bioethanol is the issue. Fuel from maize (corn) with very low power per unit area does not meet the definition of low carbon. Recently, VeraSun, the second largest bioethanol producer in the US, has been forced to make idle three distilleries, as falling demand means ethanol prices are failing to cover the production costs. The company was forced to seek bankruptcy protection in October 2008, blaming strongly fluctuating corn prices. According to the monthly World Agricultural Supply and Demand Estimates (USDA), US oilseed production will increase to 93 Mt in 2008–09 (with higher soybean but lower sunflower, canola and cottonseed production compared with 2007–08). USDA reported 2.96 Bbu for 2008 (up 11% from 2007). While the country produces 2.4 Bgy of soy oil, the US rendering industry produces 1.7 Bgy of grease and tallow. Dedicating the entire US soybean production to biodiesel would meet only 4% of diesel demand. While biodiesel is gaining momentum in the US, eight oilseed crops are expected to show particular promise in the short term: soybean, rapeseed/canola, industrial mustard, peanut, sunflower, cottonseed, corn and camelina. Many US biodiesel plants intend to switch from SBO to less expensive feedstocks, including tallow. US biodiesel industry investment is also growing in new non-edible raw materials such as algae, seashore mallow and jatropha. High vegetable oil costs (with record highs in July 2008) have chipped away profits in the biodiesel sector. Vegetable oil prices are well above the break-even point for many biodiesel plants. Consequently, USDA underscored a less promising biodiesel outlook in its recent forecast for next season’s US soybean oil demand from this sector, reducing it from 1.72 Mt to 1.59

Sustainability and use of biodiesel

693

Mt. However, this would still be far above 2006–07’s estimated 1.09 Mt and the previous season’s 705 kt. At a domestic production of 700 Mgy (2008) with forecast of 40% contraction in 2009, biodiesel is still a niche product in the total US diesel fuel market of 63 Bgy, representing only about 1.1%. From April 2007 to March 2008 the US held a 17% market share of Europe’s biodiesel imports; exports of US biodiesel to Europe amounted to 1 Mt in 2007. If the current high volume of export of biodiesel to Europe is cut back, the US might still be able to meet the RFS2 mandate of 500 Mgy biodiesel for 2009. In a steady growth scenario, expectations range from 0.5 to 1 Bgy of biodiesel production by 2010 [166] and 3 Bgy in 2012. In fact, the US is positioned by some to become the world’s largest biodiesel market by 2012, with a 19% share of the world’s biodiesel consumption, followed by Germany and France [167]. In a heavy investment scenario, 5 Bgy (or 8% of current total US diesel fuel usage) could be supplied by biodiesel in 2010, using 40 M acres of fallow land for oil producing crops. In an emergency scenario, 10–15 Bgy of biodiesel needs to be produced using high-yield oilseed crops cultivated on 50–100 M acres of cropland currently used for growing commodity export crops. In order to replace the equivalent of 140 Bgy of transportation fuel by biodiesel roughly 19 quads are required (1 quad is equivalent to 7.5 billion gallons or 28 billion litres), corresponding to a cultivated land mass of 15 000 square miles. If US land now idle (e.g. highway roadsides) were used to grow biodiesel feedstocks such as soybean or canola, some 5 Bgy of biodiesel (8% of US total diesel fuel usage) could be produced. The Energy Information Administration (EIA) lower-bound demand projection for biodiesel fuel in the US, based on an assessment of potential fleet demand for biodiesel to comply with the Energy Policy Act (EPAct) of 1992, gives only 6.5 Mgy in 2010 and 7.3 Mgy in 2020. In fact, EPAct requirements are unlikely to increase in the next 20 years. On the other hand, EIA’s upper-bound projection, which takes into account biodiesel’s potential use as a lubricity additive at 1 vol% in ULSD, is as high as 470 Mgy in 2010 and 630 Mgy in 2020. The ultra-low sulphur diesel programme will offer an opportunity for biodiesel as a lubricity additive and perhaps as a cetane booster as well. Biodiesel may also be marketed for applications in which reducing emissions of particulates and unburnt hydrocarbons is a priority, as in school and transit buses. Because additives improving diesel fuel properties can sell for a higher price than diesel fuel, the cost disadvantage for biodiesel would not be as great in the additive market. Biodiesel markets in both the US and Europe are currently characterised by a high over-capacity (at least 50%). For comparison, for most manufacturing industries the productive utilisation norm is 80–84%; for petroleum refiners more than 90%. The current excess production capacity for vegetable oil

694

Biodiesel science and technology

methyl esters in the US derives from dedicated biodiesel plants and from the 200 Mgy methyl ester capacity available from oleochemical producers, such as Procter and Gamble. Biodiesel producers will produce up to 80 Mgy at a price just high enough to cover variable costs. The capacity in the oleochemical industry will not come on stream unless the price of biodiesel is sufficiently high to draw methyl esters out of other uses. Federal Canadian mandates require including 5% renewable content in gasoline by 2010 and 2% renewable content in diesel fuel by 2012. Approximately 600 MMLy (159 MMgy) of biodiesel will be needed to meet the standard. Canada’s Climate Change Action Plan has set itself a 500 MMLy target by 2010. Canadian biodiesel will be based on virgin vegetable oils (mainly canola, but also SNO), recycled bio-oils and rendered animal fats, fish oils and seafood wastes. Canadian canola acreage has hit a record high of 15.5 million acres in 2008 (with expected average yield of 1300 lbs/ acre). Biodiesel is at an early stage of market development in Canada. A first large-scale demonstration plant, based on technology developed by the University of Toronto, went into operation in April 2001. Biodiesel was not a commercial fuel product until 2004. In the meantime, commercial biodiesel activities have developed in several provinces (AB, BC, MB, NS, ON, QC and SK). As of 16 March 2009, the total Canadian biodiesel operating capacity (5 plants) is 135 MMLy, with an unconfirmed capacity (4 plants) of another 106 MMLy. At present, the largest biodiesel producer in Canada, Biox Corp. – a technology development company, joint venture of the University of Toronto Innovations Foundation and Madison Ventures Ltd – in Hamilton, ON, with 60 MMLy installed capacity, uses multiple feedstocks and proprietary process technology that can handle high FFAcontaining feeds (UCO, TLW) without pre-treatment. Two major project developments (370 MMLy) will be canola based. Canadian Green Fuels, Inc. (Regine, SK) is constructing a 240 MMLy multi-feedstock plant (canola, flax, sunflower and soybeans). British Columbia is the only Canadian province with a biodiesel mandate (B5 by 2010, meaning 183 MML of biodiesel). British Columbia focuses on the potential to produce 125 MMLy biodiesel (B100), from recycled biooils (yellow and brown greases) and rendered animal fats in smaller urban communities, representing 4.5% of British Columbia’s total diesel usage and 11.4% of the total on-road diesel market. If a 5% biodiesel mixture (B5) is used, blended with around 2.5 billion litres of low-sulphur petrodiesel, this would enable locally produced biodiesel to be incorporated into its entire annual diesel supply [168]. The potential supply of waste yellow grease in British Columbia is estimated at 21.4 MMLy; brown grease potential around 9.3 MMLy. When yellow grease is used as a feedstock for biodiesel production, filtering and dewatering are required.

Sustainability and use of biodiesel

695

With US federal and state subsidies, a litre of biodiesel can be imported and sold in Canada for approximately 85 cents, compared with local production costs of US$1.60/L (2008). Another potential key weakness that might impede biodiesel development in Canada is winter operability, which may be overcome (at a price) by additives or special blending fuels. The Canadian export business to Europe has boomed since the EU improved high countervailing duties on US biodiesel.

14.6.4 Emerging markets Australian biodiesel production is small (50 kt in 2004). Current production originates from recycled frying oil (formerly exported to Asia for soap production) and animal fats (e.g. BTW). A multi-feedstock blend (RSO, SNO, SBO) is also used for biodiesel production. Despite a production capacity of 500 kt Australia produced only 60 kt of biodiesel in 2008 due to an unfavourable tax regime and rising feedstock prices. With the current high vegetable oil prices, the biodiesel industry is lame in many developed countries. Australian Renewable Fuels Ltd closed its two 12 MMgy biodiesel plants in Picton and Adelaide, which had started production in 2006, due to a 50% increase in feedstock costs, and unfavourable changes to Australia’s biodiesel tax credit programme. Emerging countries (Brazil, India, China, Argentina, South-East Asia) with favourable climatic conditions are feedstock-driven and building up biodiesel capacity at strong pace. The biodiesel market in Brazil, India and China was already composed of some 35 plants in 2007, while 33 additional companies are in the process of establishing biodiesel plants that could be on line by the end of 2012. As shown in Table 14.38, renewable energy sources represent almost 50% of Brazil’s energy supply, and biomass has become the second most important energy source in the country. Brazil is the global leader in bioethanol production. The country reached motor-fuel self-sufficiency in 2006. Diesel consumption in Brazil (40% of total fuel consumption) stands at approximately 40 BL/yr (2007) with a current (2008) potential market for biodiesel of 800 ML (mandatory B2 blend) up to 2 BL/yr by 2013 (mandatory B5 blend) [169]. Federal Law 11.097 (13 Jan. 2005) has established the Brazilian Table 14.38 Brazilian energy balance (2005) (after ref. [170]) Petroleum Sugarcanea Hydroelectricity Timber/vegetable coal a

Ethanol, bagasse.

42% 16% 14% 14%

Natural gas Uranium Coal Other renewables

9% 1% 1% 3%

696

Biodiesel science and technology

Biodiesel Production and Utilization Program, and Federal Law 11.116 (18 May 2005) has defined federal taxes for biodiesel (www.biodiesel.gov.br). Drivers for biodiesel development in South America are summarised in Table 6.12. One of the main objectives of the Brazilian biodiesel programme is to promote social and regional development in the most economically depressed areas, like the north-east semi-arid and Amazonian regions. Government policy is to provide social inclusion, by including familiar agriculture as a partner to biodiesel producers [169]. A regulatory framework for biodiesel development and production, formulated in 2002 (Probiodiesel programme), provides for tax incentives to biodiesel producers who buy raw materials from local poor family farmers. However, it is not certain that familiar agriculture will be able to compete with agribusiness (e.g. Argentinian style) to ensure the supply of raw materials. Brazil possesses an impressive farming land potential largely in tropical climatic conditions. The country is a major oil crop producer, in particular of SBO, PMO, CNO, SNO, CAS and CSO (see Section 6.4.4). The many biodiesel feedstock options of Brazil (per region) are listed in Table 6.10. The national biodiesel strategy aims at increasing soy production and promotes planting of castor beans, but many other energy crops would qualify as biodiesel feedstock; animal fats (700 kt/yr) are another important resource. Allegations of biofuels-related deforestation in Brazil have forced stakeholders to look more closely at biofuels and question their sustainability. Biodiesel in Brazil is an emerging industry, but has recently made a big start with prospects for soy, jatropha, castor oil and tallow [171, 172]. The first Brazilian biodiesel operation was installed in Mato Grasso State in Nov. 2000, producing 50 t/d of soybean ethyl ester [173], while the first commercial scale industry (in Cássia, MG) has been operating since 2005. Installed capacity has increased rapidly from 50 kt/yr (2005) to 600 kt/yr (2006) and 2058 kt/yr (2008). At the same time, the number of plants has increased from 35 (2007) to 51 (2008). Brazil is expected to surpass EU and US biodiesel production by the year 2015. Table 14.39 shows the expected Table 14.39 Brazilian biodiesel plants (2008–09) Region

Operation



No.

North North-East Central-West South-East South Total Source: ANP.

Construction

Projected

ML/yr

No.

ML/yr

No.

ML/yr

3 6 8 8 6

137 391 355 253 523

3 9 17 18 8

10 223 972 682 209

2 5 11 10 10

130 351 868 214 762

31

1659

55

2096

38

2325

Sustainability and use of biodiesel

697

developments; for Brazilian biodiesel plant size growth, see Fig. 11.1. Brasil Ecodiesel, Granol, Biocapital, Agrenco, ADM, Fiagril, Caramuru, BSBios, Bertin and Oleoplan account for over 70% of Brazilian biodiesel production (1037 kt in 2008), mainly concentrated in Central-West and South Brazil. Petrobras will expand its biodiesel production to 169 MMgy by 2013. In 2007 more than 4000 gas stations were distributing B2. Barros et al. [174] estimated the overall production costs for biodiesel obtained from various raw materials by each Brazilian region, considering raw material production costs, oil production costs and biodiesel production costs (Table 14.40). In Brazil, biodiesel (B2) is competitive with petrodiesel (both at R$2.05/L in Sept. 2008; 71 = R$2.45), compared with bioethanol at R$1.75/L. Brazil will be a dominant biodiesel exporter, competing against Argentina, Malaysia, and even the US for global market share. Although Brazil can sustainably produce several vegetable oils, soybeans will continue to be the main crop up to the 2020s. Brazil has enough production capacity to process biodiesel for domestic consumption (at present) and for export (in the future) and will continuously expand this capacity. Brazil and Argentina will be key players to support nutritional and energy vegetable oil and animal fats in the next decade. Brazil will be the key player after the 2020s, possibly alongside African countries, like Zaire and Mozambique. Argentina is a major agribusiness player and a main producer of vegetable oils. Being the world’s third largest soybean producer, the country has recently developed into an important soy oil and biodiesel exporter. Figure 2.1 shows the spectacular growth in soybean production (now 100% GMO, no-till farming) in Argentina, in particular after the introduction of GM soy in the 1996–97 season. Today, over 53% of the entire agricultural land surface in Argentina is utilised for soybean production (6 Mt/yr SBO on 15 Mha). A principal criticism is related to deforestation (on 600 kha) associated with soy cultivation in forested areas such as the Humid Chaco [175]. Argentina’s approved Law 26.331 (26 Dec. 2007) is a measure to curb illegal deforestation of native forests. In Argentina, soybean is readily available and cheap, and milling capacities are sufficient; consequently, the Table 14.40 Estimated biodiesel production costs (US$/L) in Brazil (after ref. [174]) Region

Feedstock



SBO

North North-East Central-West South-East South

0.575 0.607 0.824 0.351 0.782 0.435 0.481 0.615 0.794 0.881

PMO

CSO

CAS

SNO

0.510 0.757 0.813

698

Biodiesel science and technology

vegetable oil companies have a strong interest in large-scale production of biodiesel. Vertical integration of vegetable oil and biodiesel producers (e.g. AGD and Vicentin) is quite common. In Argentina, there is a differential export tax structure that favours exporting soybean oil over exporting soybeans, and exporting biodiesel over exporting soybean oil. The export tax for biodiesel is around 12% lower than for vegetable oil. That investment incentive is driving growth in the Argentine biodiesel industry, with Europe as the target market. Until 2004–05 only small-scale production existed, with the neat fuel (B100) being designated for autoconsumption and local distribution. However, recently many large-scale plants (up to 300 kt/yr) have been launched and 17 more are under construction, mainly along the Paraná river. Most biodiesel projects are located in Santa Fé province, where Rosario is emerging as a world centre for soy biodiesel production. Figure 14.11 shows the evolution of Argentina’s biodiesel production capacity. Total capacity of 1080 kt/yr (2007–08) is set to increase to 3697 kt/yr in 2010 with 33 projected production plants and eventually up to 5.2 Mt/yr. Currently, there is practically no investment in biodiesel production plants focused on supplying the local market. Argentina has become the fifth-largest biodiesel producer by the end of 2008 (960 kt or >10% global production) behind Germany, the US, France and Brazil, while operating at 50% of tatal installed capacity [176]. A cost calculation indicates that Argentinian-produced biodiesel from soybean oil is very cost competitive – even on a global scale – and almost price competitive with current diesel prices at the pump [177]. Biodiesel production in Argentina is facilitated by the levy of differential export taxes. Argentina’s biodiesel production (forecast 2009: 1.2 Mt) is likely to supply the international markets (mainly Europe through Rotterdam) up to 2010, but the country faces increasing domestic (bio)diesel demand in the medium term (post-2010) [178]. Currently, Argentina is a net diesel importer, consuming 10 Mt/yr of diesel. The Argentine Biofuels Law (Law 26.093) is likely to create a domestic demand for 650–800 ML biodiesel (B5) by 2010 [111]. Argentina’s competitive position in the production of vegetable oil, the high efficiency throughout the whole value chain from crop production to oil milling, the existing infrastructure to transport, store and also export the vegetable oil, as well as the secure and diverse feedstock options make biodiesel a very attractive option to supply the international market – at least in the short run. However, in order to ensure only B5 in the Argentinian transport system, 12% of the current soybean cultivation area would have to be devoted in 2010 and 14% in 2015 [178]. In other words, Argentina cannot become diesel self-sufficient through soybean-derived biodiesel if the cultivation area is not extended significantly. An extension for this purpose is not seen as a desirable option. A diversification of feedstock crops (secondgenerations) will be necessary for a sustainable biodiesel market.

Sustainability and use of biodiesel

699

3.947

4

3.697

3

Mt

2.407 2 1.425

1 0.585 0.155 0

2006

2007

2008

2009

2010

2011

Year

14.11 Evolution of Argentina’s biodiesel production capacity (Source: Argentine Renewable Energies Chamber).

Unlike Brazil, the focus in Argentina lies solely on (very) large-scale production (150 kt/yr on average), derived exclusively from soybean oil, despite the fact that the country is also a main producer of SNO, RSO, SFO and PNO. Argentina and Brazil also have interest in using waste cooking oil. A life cycle assessment of Argentinian soy biodiesel is available [179]. Argentina still needs to put quality standards in place. In contrast to Brazil, in Argentina bioethanol plays only a very minor role. Until 2006, ethanol production was about 250 ML/yr. The corn-based bioethanol industry is likely to grow [180]. Mexico has an important bioenergy potential (estimates range from 2635 to 3771 PJ/yr). Sugarcane and wood currently supply 8% of Mexico’s primary energy consumption. Biodiesel production is still in its infancy. A small plant in Nuevo León (2005) produces biodiesel from fat waste from slaughterhouses. In Colombia, the largest palm oil producer in the Americas (from 180 kha in 2003 to 300 kha in 2008), 35% of the output is used for biodiesel fuel. Colombia’s production is exploding. New and large markets for biodiesel are expected to emerge in China and India, since the governments of both countries have announced major biodiesel initiatives. P.R. China is the world’s second largest consumer

700

Biodiesel science and technology

of transportation fuels and is developing coal-to-liquids (CTL) as the main domestic alternative in the long term. China’s total consumption of fossil diesel is constantly rising (95.5 Mt in 2004). With renewable energy legislation in place in 2006, P.R. China aims at a renewable energy share of 15% by 2020. China is the world’s biggest importer of PMO, RSO and SBO (totalling 18% of the country’s global trade volume). Palm oil consumption is expected to increase annually by 10%. Biofuel production is very limited, with 3800 ML bioethanol (2005) and 38–60 kt biodiesel (2004); biodiesel output has recently increased (to about 250 kt in 2008) with prospects of 5 Mt by 2020. Although RSO is considered a suitable raw material in the short term, China is committed to using non-food feedstocks. The current irregular production (due to supply problems) is based on imported vegetable oils, offal, UCO, TLW and some domestic jatropha oil. Leading producers are Gushan Environmental Energy Ltd, which operates several facilities (330 kt, and expanding) using mainly vegetable oil offal and UCO, and China Biodiesel International Holding (with two production bases), which exploits virgin vegetable oils, UCO and TLW (Table 14.41). A recently established 50 kt/yr MFT biodiesel facility in Hainan province operates with imported palm oil and domestic jatropha oil. Table 6.9 shows a cost comparison of Chinese biodiesel made from different local raw materials. While China’s pro-capita agricultural potential is limited, the country is undertaking massive efforts to cultivate energy crops on marginalised land and to grow bio-energy forests of perennial shrubs and trees (see Section 6.4.3). Indian energy policy is driven by diversification of energy sources. The Indian biodiesel industry languishes in the absence of clear-cut government policy. India favours use of non-edible oils and fats for biodiesel purposes. In the medium term (2020) India intends replacing 20% of diesel fuels (i.e. at least 8 Mt/yr) with jatrodiesel. The country is building up 11.2 Mha of jatropha plantations (main feedstock target) by 2012. India possesses Table 14.41 Developing biodiesel industry in P.R. China (2007) Production facility Location

Production capacity (kt)

Beijing Gushan Sichuan Gushan Handan Gushan Fujian Gushan China Clean Energy Inc. Shanghai Gushan Chongqing Gushan Hunan Gushan Xiamen Zhuoyue Biomass Energy   Co., Ltd. Longyan Zhuoyue New Energy   Development Co., Ltd.

Beijing Mianyang (Sichuan prov.) Handan (Hebei prov.) Fuzhou (Fujian prov.) Jiangyin (Jiangsu prov.) Shanghai Chongqing Hunan Xiamen (Fujian prov.)

240 60 30 100 110 n.g. n.g. n.g. n.g.

Longyan (Fujian prov.)

n.g.

Sustainability and use of biodiesel

701

abundant, but still largely underexploited, resources with a wide range of plants and oilseeds of high volume potential (see Section 6.4.1) and could develop into a leading world producer of biodiesel. India operates a 100 kt/ yr crude palm/PFAD biodiesel plant. In January 2006 BioEnergies India has commenced commercial production of biodiesel near Ganapathipalayam (Pollachi district, Tamil Nadu) using rubber seed oil. For future prospects for Indian biodiesel, see ref. [128]. South-East Asian countries, in particular Malaysia, Indonesia and Thailand, possess surplus palm crops. Malaysia and Indonesia are the globally leading palm oil producers (86% of total palm oil production at 7.85 Mha). Both countries currently still produce palm diesel for domestic use, but have considerable export potential. In particular, Malaysia aims at becoming the world’s biggest producer/exporter of biodiesel. However, major Malaysian plantation companies have refused to invest in biodiesel or to invest in creating a market for biofuels. In an effort to diversify energy sources, Indonesia has already built up a sizeable palm biodiesel production capacity (820 kt/yr, 2007), to be extended to 9.2 Mt/yr (2025). At present, biodiesel production in Indonesia is facilitated by the levy of differential export taxes. Malaysia has licensed 16 palm oil biodiesel plants, building up a 9 Mt/yr production capacity (2008 production: 420 kt). Allegations of biofuels-related deforestation in South-East Asia (record setting in Indonesia) have forced stakeholders to look more closely at biofuels and question their sustainability. Palm oil from ex-forest plantations is not a green fuel. The Malaysian government is determined to develop the palm oil industry sustainably. Plantation companies no longer resort to slash-and-burn; degraded forests are cleared and re-planted in a sustainable manner. The main thrust of the oil palm industry today is to increase the supply through yield improvement – from 4 t/ha to 6 or 8 t/ ha – by better clones and seeds and advanced pest control systems, while reducing the levels of chemicals through organic compost. With NExBTL production from Neste Oil, technology-driven Singapore is profiling itself as a major renewable (non-ester) diesel producer/exporter. The outcome of the biodiesel industry’s first global crisis and shakeout is likely to accelerate a shift in production from north to south, driven by the availability of feedstock, lower feedstock prices, modern technology and more affordable labour, and the ability to generate Kyoto Protocol carbon credit income. For a biodiesel global market survey 2020, see ref. [181].

14.7

Bibliography

W. Thurmond, Algae 2020: Next Generation Biofuels Markets and Commercialization Outlook, Emerging Markets Online, Houston, TX (2009).

702

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F. Cavani, G. Centi, S. Perathoner and F. Trifirò (eds), Sustainable Industrial Chemistry. Principles, Tools and Industrial Examples, Wiley-VCH, Weinheim (2009). D.J.C. MacKay, Sustainable Energy-Without the Hot Air, UIT, Cambridge (2009); www.withouthotair.com J.H. Clark and F. Deswatre (eds), Introduction to Chemicals from Biomass, John Wiley & Sons, Ltd., Chichester (2008). W. Thurmond, Biodiesel 2020: A Global Market Survey, Emerging Markets Online, Houston, TX (2008). A. Demirbaş, Biodiesel: A Realistic Fuel Alternative for Diesel Engines, Springer-Verlag, London (2008). Global Biofuels Center, Global Ethanol and Biodiesel Outlook, 2008–2015, Hart Energy Publishing, Houston, TX (2008). National Biodiesel Board, Biodiesel – A Sustainable Choice, Jefferson City, MO (2008); www.biodiesel.org/resources/sustainability. National Research Council of the National Academies, Water Implications of Biofuels Production in the United States, National Academies Press, Washington, DC (2008). The Royal Society of Chemistry, Sustainable Biofuels: Prospects and Challenges, London (2007); www.royalsociety.org/displaypagedoc. asp?id=28632. J. Van Gerpen, R. Pruszko, D. Clements, B. Shanks and G. Knothe, Building a Successful Biodiesel Business, AOCS Press, Urbana, IL (2006). Worldwatch Institute, German Agencies for Technical Cooperation (GTZ) and Renewable Resources (FNR), Biofuels for Transportation: Global Potential and Implications for Sustainable Agriculture and Energy in the 21st Century, Washington, DC/Eschborn/Gülzow (2006). HB International SAS, Biodiesel and Related Products Market Prices, Montmorency (2006); http://www.oleoline.com. G. Knothe, J. Van Gerpen and J. Krahl (eds), The Biodiesel Handbook, AOCS Press, Urbana, IL (2005). K.S. Tyson, Biodiesel Handling and Use Guidelines, DOE, Office of Energy Efficiency and Renewable Energy (2004). A. Munack and J. Krahl (eds), Biodiesel. Potenziale, Umweltwirkungen, Praxiserfahrungen, Landbauforschung Völkenrode, Sonderheft 239, Braunschweig (2002). Organisation for Economic Co-operation and Development (OECD), The Application of Biotechnology to Industrial Sustainability. A Primer. OECD Publishing, Paris (2001). G.A. Reinhardt and G. Zemanek, Ökobilanz Bioenergieträger. Basisdaten, Ergebnisse, Bewertungen (LCA of Bioenergy Sources. Data, Results, Evaluations), Erich Schmidt Verlag, Berlin (2000). United Nations Development Programme, World Energy Assessment 2000

Sustainability and use of biodiesel

703

– Energy and the Challenge of Sustainability, UNDP, New York, NY (2000). M. Kaltschmitt and G.A. Reinhardt (eds), Nachwachsende Energieträger: Grundlagen, Verfahren, ökologische Bilanzierung (Biobased Energy Sources: Basics, Procedures, Ecological Assessment), Vieweg Verlag, Braunschweig/Wiesbaden (1997). G. Boyle (ed.), Renewable Energy – Power for a Sustainable Future, Oxford University Press, Oxford (1996). M. Curran (ed.), Environmental Life-Cycle Assessment, John Wiley & Sons, Inc., New York, NY (1996). W. Körbitz, The Technical, Energy and Environmental Properties of BioDiesel, Körbitz Consulting, Vienna (1993). Society of Environmental Toxicology & Chemistry, A Technical Framework for Life Cycle Assessments, SETAC, Washington, DC (1991). http://www.rsc.org/ScienceAndTechnology/Policy/Documents/FSA_ sustainable_development.asp

14.8

References

[1] D.S. Shreshta and J. Van Gerpen, The biodiesel energy balance, Biodiesel Mag. 4(10) (2007) 112–16. [2] J. Sheehan, V. Camobreco, J.A. Duffield, M. Graboski and H. Shapouri, Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus, NREL/ SR-580-24089, Golden, CO (1998). [3] D. Pimentel and T.W. Patzek, Ethanol production using corn, switchgrass, and wood; biodiesel production using soybean and sunflower, Nat. Resourc. Res. 14(1) (2005) 65–76. [4] P. Ahmed, J. Decker and D.S. Morris, How Much Energy Does it Take to Make a Gallon of Soydiesel? National Soydiesel Development Report, Jefferson City, MO (1994). [5] J. Hill, E. Nelson, D.S. Tilman, S. Polasky and D. Tiffany, Environmental, economical and energetic costs and benefits of biodiesel and ethanol biofuels, Proc. Natl. Acad. Sci. 103(30) (2006) 11206–10. [6] J. Van Gerpen and D. Shreshta, Updating the energy balance for producing soybean biodiesel in the United States, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [7] E. Poitrat, Ecological assessment of rapeseed methyl ester in comparison with mineral fuel (life cycle analysis), Proc. 8th European Biomass Conf., Vienna (3–5 Oct. 1994), Vol. 2, pp. 1081–93. [8] R. Tan, A.B. Culaba and M.R.I. Purvis, Application of possibility theory in the life-cycle inventory assessment of biofuels, Intl. J. En. Res. 26 (2002) 737–45. [9] S.E. Batchelor, E.J. Booth and K.C. Walker, Energy analysis of rape methyl ester (RME) production from winter oilseed rape, Ind. Crop Prod. 4 (1995) 193–202. [10] V. Makareviciene, E. Sendzikiene and P. Janulis, Solubility of multicomponent biodiesel fuel systems, Bioresour. Technol. 96 (2005) 611–16.

704

Biodiesel science and technology

[11] S. Grass and T. Heim, Ökologische Risikoanalyse und Wirtschaftlichkeitsberechnungen der landwirtschaftlichen Rapsmethylester-Produktion sowie zweier alternativer Anbau-szenarien (‘Carbotech – Study’), Carbotech AG, Zürich (in charge of WWF Switzerland), Zürich (1991). [12] K. Scharmer and G. Gosse, Energy Balance, Ecological Impact and Economics of Vegetable Oil Methyl Ester Production in Europe as Substitute for Fossil Diesel, EU-Study ALTENER 4.1030/E/94-002-1 (1995). [13] S. Becher, T.-U. Eden, M. Kaltschmitt, H.-J. Nagel, A. Patyk, J. Radtke, G.A. Reinhardt and T. Stelzer, Lebenswegvergleiche: Energie und Emissionen in die Atmosphäre, in Nachwachsende Energieträger (M. Kaltschmitt and G.A. Reinhardt, eds), Vieweg, Braunschweig/Wiesbaden (1997), pp. 289–429. [14] M. Kaltschmitt, G.A. Reinhardt and T. Stelzer, Life cycle analysis of biofuels under different environmental aspects, Biomass. Bioen. 12 (1997) 121–34. [15] J. Connemann and J. Fischer, Biodiesel in Europe 1998, Paper presented at Intl. Liquid Biofuels Congress, Curitiba, PR (19–22 July 1998) http://www. biodiesel. de. [16] K. Scharmer, Biodiesel-Energie – und Umweltbilanz Rapsölmethylester, UFOP, Bonn (Nov. 2001). [17] R.E. Horne, N.D. Mortimer and M.A. Elsayed, Energy and carbon balances of biofuels production: biodiesel and bioethanol, Proc. Intl. Fertiliser Society 510 (3 Apr. 2003) 1–55. [18] J. Sheehan, V. Camobreco, J.A. Duffield, M. Graboski and H. Shapouri, An Overview of Biodiesel and Petroleum Life Cycles, NREL/TP-580-24772, NREL, Golden, CO (1998). [18a] D.S. Shrestha, A. Pradhan, A. McAloon, M. Haas, W. Yee, J.A. Duffield and H. Shapouri, unpublished results (2009). [19] A.A.A. Süß, Wiederverwertung von gebrauchten Speiseölen/fetten in energetischtechnischen Bereich, Fortschr.-Ber. VDI, Reihe 15: Umwelttechnik, VDI Verlag, Düsseldorf (1999) 219. [20] A. Groschen, Energie Balance/Life Cycle Inventory for Ethanol, Biodiesel and Petroleum Fuels, Minnesota Dept. of Agriculture (n.d.); www.mda.state.mn.us/ cgi-bin/MsmFind.exc?query=biodiesel+energy+yield. [21] R.R. Tan, A.B. Culaba and M.R.I. Purvis, Carbon balance implications of coconut biodiesel utilization in the Philippine automotive transport sector, Biomass Bioen. 26 (2004) 579–85. [22] K.Y. Cheah, Y.M. Chou, A.N. Ma and Y. Basiron, Production technology of palm diesel, Proc. 1998 PORIM Intl. Biofuel and Lubricant Conference, Bangi/ Malaysia (4–5 May, 1998). [23] S.E. Batchelor, E.J. Booth, K.C. Walker and P. Cook, The Potential for Bioethanol Production from Wheat in the UK, The Home-Grown Cereals Authority, London, Res. Rev. 29 (1995). [24] Deutsches Institut für Normung (ed.), DIN EN 14040 ff: Umweltmanagement – Produkt-Ökobilanz, Beuth-Verlag, Berlin (1997–99). [25] W.M.J. Achten, P. Vandenbempt, P. Lemaître, E. Mathys and B. Muys, Proposing a life cycle land use impact calculation methodology, Proc. 6th Intl. Conf. on LCA in the Agri-Food Sector, Zürich (12–14 Nov. 2008). [26] S.O. Gärtner and G.A. Reinhardt, Environmental implications of biodiesel (LifeCycle Assessment), in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 219–30.

Sustainability and use of biodiesel

705

[27] J. Fargione, J. Hill, D. Tilman, S. Polasky and P. Hawthorne, Land clearing and biofuel carbon debt, Science 319 (29 Feb. 2008) 1235–8. [28] T. Searchinger, R. Heimlich, R.A. Houghton, F. Dong. A. Elobeid, J. Fabiosa, S. Tokgoz, D. Hayes and T.-H. Yu, Use of US croplands for biofuels increases greenhouse gases through emissions from land-use change, Science 319 (29 Feb. 2008) 1238–40. [29] D. Tilman, J. Hill and C. Lehman, Carbon-negative biofuels from low-input highdiversity grassland biomass, Science 314 (2006) 1598–1600. [30] Levelton Engineering and (S&T)2 Consulting Inc., Assessment of Biodiesel and Ethanol Diesel Blends. Greenhouse Gas Emissions, Exhaust Emissions, and Policy Issues, Ottawa, ON (2002). [31] G. Zemanek and G.A. Reinhardt, Notes on life-cycle assessments of vegetable oils, Fett/Lipid 101 (1999) 321–7. [32] G.A. Reinhardt, Life cycle assessments (LCAs) of liquid biofuels: latest results, Proc. 2nd European Motor Biofuels Forum (22–25 Sept. 1996), Joanneum Research Forschungsgesellschaft, Graz (1996), pp. 297–303. [33] G.A. Reinhardt and G. Zemanek, Ecobalance ‘RME versus diesel fuel’. Present state of discussions, Landbauforsch. Völkenrode (Braunschweig) 48(3) (1998) 107–17. [34] H. Helms, G.A. Reinhardt and N. Rettenmaier, Bioenergie aus Palmöl: Ökologische Chancen und Risiken, Energiewirtsch. Tagesfragen – Ztschr. f. Energiewirtsch., Recht, Techn. & Umwelt 56 (11) (2006) 70–3. [35] N. Rettenmaier, Life-cycle assessment of palm oil biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [36] M. Mittelbach and C. Remschmidt, Biodiesel – The Comprehensive Handbook, Boersedruck Ges., Vienna (2004). [37] B. Franke and G.A. Reinhardt, Environmental Impacts of Biodiesel Use; www. biodiesel.org./resources/reportsdatabase/reports/gen/gen-110.pdf. [38] T.-U. Eden and G.A. Reinhardt, Environmental implications of biodiesel use. An assessment, in Biomass for Energy, Environment, Agriculture and Industry, Proc. 8th European Biomass Conference (P. Chartier, A.A.C.M. Beenackers and G. Grassi, eds.), Vienna (3–5 Oct. 1994), Elsevier, Oxford (1995), pp. 1141–8. [39] M. Patel, G.A. Reinhardt and G. Zemanek, Vegetable oils for biofuels versus surfactants. An ecological comparison for energy and greenhouse gases, Fett/ Lipid 101 (1999) 314–20. [40] J. Olthoff, Biodiesel: deutsche und europäische Perspektiven, in Biodiesel. Potenziale, Umweltwirkungen, Praxiserfahrungen (A. Munack and J. Krahl, eds), Landbauforschung Völkenrode (Braunschweig) 239 (2000), pp. 2–8. [41] National Research Council of the National Academies, Water Implications of Biofuels Production in the United States, National Academies Press, Washington, DC (2008). [42] O. Syassen, Chancen und Problematik nachwachsender Kraftstoffe, Motortechn. Ztschr. 53 (1992), Hefte 11 and 12. [43] S.J. Clark, J. Wagner, M.D. Schrock and P.G. Piennaar, Methyl and ethyl soybean esters as renewable fuels for diesel engines, J. Am. Oil Chem. Soc. 61 (1984) 1632–8. [44] M.S. Graboski and R.L. McCormick, Combustion of fat and vegetable oil derived fuels in diesel engines, Progr. En. Combust. Sci. 24 (1998) 131–2. [45] S.H. Stoldt and H. Dave (to Lubrizol Corporation), Esters derived from vegetable oils used as additives for fuels, US Pat. No. 5,730,029 (24 March 1998).

706

Biodiesel science and technology

[46] L. Schumacher, Biodiesel lubricity, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 137–44. [47] B. Hertz, R. Button, F. Coxworth and R. Gray, Biodiesel Fuel Additives/Lubricants to Improve Diesel Fuel Use Effeciency and Reduce Engine Wear, Prairie Sustainable Agriculture and Rural Development Project, Saskatoon, SK (2001). [48] H. Chesneau, Overcoming microbiological contamination, material compatibility, Biodiesel Mag. 5(6) (2008) 116–19. [49] C.L. Peterson and G. Möller, Biodiesel fuels: biodegradability, biological and chemical oxygen demand, and toxicity, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 145–60. [50] G. Knothe, Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters, Fuel Proc. Technol. 86 (2005) 1059–70. [51] N.U. Soriano Jr, V.P. Migo and M. Matsumura, Ozonized vegetable oil as pour point depressant for neat biodiesel, Fuel 85 (2006) 25–31. [52] T. Weyenberg, Improving biodiesel handling and operability in cold weather, Biodiesel Mag. 4(10) (2007) 102–6. [53] M. Wörgetter, H. Prankl and J. Rathbauer, Eigenschaften von Biodiesel, Landbauforschung Völkenrode (Braunschweig), Sonderheft 190 (BiodieselOptimierungspotentiale und Umwelteffekte) (1998), pp. 31–43. [54] J.A. Kinast, Production of Biodiesels from Multiple Feedstocks and Properties of Biodiesels and Biodiesel/Diesel Blends, NREL/SR-510-31466 (March 2003). [55] V.T. Wyatt, M.A. Hess, R.O. Dunn, T.A. Foglia, M.J. Haas and W.N. Marmer, Fuel properties and nitrogen oxide emission levels of biodiesel produced from animal fats, J. Am. Oil Chem. Soc. 82 (2005) 585–91. [56] Minnesota Star Tribune (6 Jan. 2009). [57] R.O. Dunn, Cold weather properties and performance of biodiesel, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 83–121. [58] W. De Greyt, J. Maes, F. Soragna and M. Kellens, Processing pathways to an improved yield and quality of biodiesel from vegetable oils and animal fats, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [59] P.F. Bondioli, M.N. Ravasio and F. Zaccheria (to CNR/Università degli Studi di Milano), A method for the production of biodiesel, starting from high iodine number fatty substances, PCT Int. Publ. No. WO 2006/111997 A1 (26 Oct. 2006). [60] N.A. Bringe, Soybean oil composition for biodiesel, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 161–4. [61] R. Sarin, M. Sharma, S. Sinharay and R.K. Malhotra, Jatropha-palm biodiesel blends: an optimum mix for Asia, Fuel 86 (2007) 1365–71. [62] G. Knothe and R.O. Dunn, recent results from biodiesel research at the National Center for Agricultural Utilization Research, Landbauforschung Völkenrode (Braunschweig), Sonderheft 190 (Biodiesel-Optimierungspotentiale und Umwelteffekte) (1998), pp. 69–78. [63] G. Knothe and R.O. Dunn, Biofuels derived from vegetable oils and fats, in Oleochemical Manufacture and Applications (F.D. Gunstone and R.J. Hamilton, eds), Sheffeld Academic Press, Sheffield (2001), pp. 106–63. [64] X. Lang, A.K. Dalai, N.N. Bakshii, M.J. Reaney and P.B. Hertz, Preparation and characterization of biodiesels from various bio-oils, Bioresour. Technol. 80 (2001) 53–62.

Sustainability and use of biodiesel

707

[65] G. Knothe, A.C. Matheaus and T.W. Ryan, Cetane numbers of branched and straight-chain fatty esters determined in an ignition quality tester, Fuel 82 (2003) 971–5. [66] I. Lee, L.A. Johnson and E.G. Hammond, Use of branched-chain esters to reduce the crystallization temperature of biodiesel, J. Am. Oil Chem. Soc. 72 (1995) 1155–60. [67] T.A. Foglia, L.A. Nelson, R.O. Dunn and W.N. Marmer, Low-temperature properties of alkyl esters of tallow and grease, J. Am. Oil Chem. Soc. 74 (1997) 951–5. [68] G. Demmering, K. Schmidt, F. Bongardt and L. Wittich (to Henkel KGaA), Mischungen von Fettsäureniedrigalkylestern mit verbesserten Kältestabilität, Germ. Pat. DE 4,040,317 A1 (17 Dec. 1990). [69] R.O. Dunn, M.W. Shockley and M.O. Bagby, Improving the low temperature properties of alternative diesel fuels: vegetable oil-derived methyl esters, J. Am. Oil Chem. Soc. 73 (1996) 1719–28. [70] R.O. Dunn and M.O. Bagby, Low-temperature properties of triglyceride-based diesel fuels: transesterified methyl esters and petroleum middle distillate/ester blends, J. Am. Oil Chem. Soc. 72 (1995) 895–904. [71] G. Hillion, B. Delfort and I. Durand (to IFP), Procédé de fabrication de biocarburants. Transformation de triglycerides en deux familles de biocarburants: monoesters d’acides gras et ethers solubles du glycerol, Fr. Pat. Appl. 2,866,653 (26 Aug. 2005). [72] B. Delfort, G. Hillion and I. Durand (to IFP), Procédé de fabrication de biocarburants. Transformation de triglycerides en deux familles de biocarburants: monoesters d’acides gras et acetales solubles du glycerol, Fr. Pat. Appl. 2,866,654 (26 Aug. 2005). [73] H. Noureddini (to Board of Regents of University of Nebraska), System and process for producing biodiesel fuel with reduced viscosity and a cloud point below thirty-two (32) degrees Fahrenheit, US Pat. No. 6,174,501 (16 Jan. 2001). [74] T.A. Isbell, M.R. Edgcomb and B.A. Lowery, Physical properties of estolides and their ester derivatives, Ind. Crops Prod. 13 (2001) 11–20. [75] S.C. Cermak, K.B. Brandon and T.A. Isbell, Synthesis and physical properties of estolides from lesquerella and castor fatty acid esters, Ind. Crops Prod. 23 (2006) 54–64. [76] M. Scherer and J. Souchik (to Rohmax Additives GmbH), Copolymers which can be obtained using ATRP methods, and method for producing and using the same, PCT Int. Publ. No. WO 01/40334 A1 (7 June 2001). [77] M. Scherer, J. Souchik and J.M. Bollinger (to Rohmax Additives GmbH), Block copolymers and method for the production and utilization thereof, PCT Int. Publ. No. WO 01/40339 A1 (7 June 2001). [78] Lubrizol (Wickliffe, OH), BioQualified™ fuel additives; www.bioqualified. com. [79] Evonik RohMax Additives GmbH (Darmstadt), VISCOPLEX® Cold Flow Improvers; [email protected]. [80] M. Matsumura (to Sun Care Fuels Corp.), Modifier for biodiesel fuel, fuel, methods relating to those, Eur. Pat. Appl. EP 1,681,338 A1 (29 Sept. 2004). [81] I. Lee, L.A. Johnson and E.G. Hammond, Reducing the crystallization temperature by winterizing methyl soyate, J. Am. Oil Chem. Soc. 73 (1993) 631–6. [82] M.E. González-Gómez, R. Howard-Hildige, J.J. Leahy and B. Rice, Winterization

708

[ 82a] [83] [84]

[85] [86]

[87]

[88]

[89] [90]

[91]

[92]

[93]

[94]

[95] [96] [97] [98]

[99]

Biodiesel science and technology of waste cooking oil methyl ester to improve cold temperature fuel properties, Fuel 81 (2002) 33–9. S.R. Schill, B100 to the Arctic circle, Biodiesel Mag. 6(6) (2009) 36–40. P. Bondioli, A. Gasparoli, A. Lanzani, E. Fedeli, S. Veronese and M. Sala, Storage stability of biodiesel, J. Am. Oil Chem. Soc. 72 (1995) 699–702. BIOSTAB, Stability of Biodiesel Used as a Fuel for Diesel Engines and Heating Systems, Bundesanstalt für Landtechnik (BLT), Wieselburg (2003); http://www. biostab.info. H. Prankl, Stability of biodiesel, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 127–36. United States Environmental Protection Agency, A Comprehensive Analysis of Biodiesel Impacts on Exhaust Emissions, Draft Technical Report, EPA420-P-02011 (2002). J. Krahl, A. Munack, O. Schröder, H. Stein and J. Bünger, Influence of biodiesel and different petrodiesel fuels on exhaust emissions and health effects, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 175–82. R.L. McCormick and T.L. Alleman, Effect of biodiesel fuel on pollutant emissions from diesel engines, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 165–74. K.S. Tyson, Biodiesel Handling and Use Guidelines, National Renewable Energy Laboratory, Golden, CO (2001). G. Knothe, C.A. Sharp and T.W. Ryan, Exhaust emissions of biodiesel, petrodiesel, neat methyl esters, and alkanes in a new technology engine, En. Fuels 20 (2006) 403–8. M. Mittelbach and P. Tritthart, Diesel fuel derived from vegetable oils: III. Emission tests using methyl esters of used frying oil, J. Am. Oil Chem. Soc. 65 (1988) 1185–7. A. Boehman, J. Song, J. Szybist, K. Al-Qurashi and Y. Zhang, Impacts of biodiesel on combustion and emissions of NOx and particulate, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). R.L. McCormick, M.S. Graboski, T.L. Alleman, A.M. Herring and K.S. Tyson, Impact of biodiesel source material and chemical structure on emissions of criteria pollutants from a heavy-duty engine, Environm. Sci. Technol. 35 (2001) 1742–7. L. Canoira, R. Alcántara, S. Torcal, N. Tsiouvaras, E. Lois and D.M. Korres, Nitration of biodiesel of waste oil: nitrated biodiesel as a cetane number enhancer, Fuel 86 (2007) 965–71. R.L. McCormick, J.R. Alvarez and M.S. Graboski, NOx Solutions for Biodiesel, NREL/SR-510-31465, Golden, CO (2003). K. Corkwell, Diesel fuel injector performance: the difference is in the additives, Biodiesel Mag. 5(12) (2008) 104–7. P. Bondioli, From oil seeds to industrial products: present and future oleochemistry, J. Synth. Lubr. 21 (2005) 332–43. J. de A. Rodrigues Jr., F. de P. Cardoso, E.R. Lachter, L.R.M. Estevão, E. Lima and R.S.V. Nascimento, Correlating chemical structure and physical properties of vegetable oil esters, J. Am. Oil Chem. Soc. 83 (2006) 353–7. Y.M. Choo, F.S. Cheng, C.L. Yung, H.L.N. Lau, A.N. Ma and Y. Basiron, Palm diesel with low pour point for cold climate countries, MPOB Techn. Note No. 146 (May 2002).

Sustainability and use of biodiesel

709

[100] Y.M. Choo, S.F. Cheng, C.L. Yung, H.L.N. Lau, A.N. Ma and Y. Basiron, Low pour point palm diesel, Malaysian Pat. SG 142118 (28 May 2008). [101] M. Mittelbach and H. Enzelsberger, Transesterification of heated rapeseed oil for extending diesel fuel, J. Am. Oil Chem. Soc. 76 (1999) 545–50. [102] A. Serdari, E. Lois and S. Stournas, Impact of esters of mono- and dicarboxylic acids on diesel fuel quality, I&EC Res. 38 (1999) 3543–8. [103] E.N. Frankel, Lipid Oxidation, The Oily Press, Dundee (1998). [104] G. Knothe and R.O. Dunn, Dependence of stability index of fatty compounds on their structure and concentration and presence of metals, J. Am. Oil Chem. Soc. 80 (2003) 1021–6. [105] T. Buhr, S. Sato, F. Ebrahim, A.Q. Xing, Y. Zhou, M. Mathiesen, B. Schweiger, A. Kinney, P. Staswick and T. Clemente, Ribozyme termination of RNA transcripts down-regulate seed fatty acid genes in transgenic soybean, Plant J. 30 (2002) 155–63. [106] M.E. Tat, P.S. Wang, J.H. Van Gerpen and T.E. Clemente, Exhaust emissions from an engine fueled with biodiesel from high-oleic soybeans, J. Am. Oil Chem. Soc. 84 (2007) 865–9. [107] I. Debruyne, Biodiesel blends based on an optimal choice of raw materials – Matching costs with high quality standards, in 8th AOCS Practical Short Course on Biodiesel: Processing, Chemistry and Production, Vienna (4–5 Nov. 2007). [108] J.A. Weber, The Economic Feasibility of Community-based Biodiesel Plants, M.Sc. Thesis, University of Missouri, Columbia, MO (1993). [109] Y. Zhang, M.A. Dubé, D.D. McLean and M. Kates, Biodiesel production from waste cooking oil: 2. Economic assessment and sensivity analysis, Bioresour. Technol. 90 (2003) 229–40. [110] M. Kleber, Economics of a Biodiesel Plant, Presentation at AOCS Annu. Mtg. 2004; http://www.lurgipsi.com/files/Lurgi%20AOCS%202004%20Presentation. PDF. [111] J.A. Mathews and H. Goldsztein, Capturing latecomer advantages in the adoption of biofuels: the case of Argentina, En. Policy 37 (2009) 326–37. [112] W.K. Jaeger and R. Siegel, Economics of Oilseed Crops and Their Biodiesel Potential in Oregon’s Willamette Valley, Oregon State University Special Rept. 1081 (May 2008). [113] G.A. Shumaker, A. Luke-Morgan and J.C. McKissick, Economic Analysis of Biodiesel Production in Georgia, Center for Agribusiness and Economic Development, University of Georgia, Statesboro, GA (2007), FR-07-03; http:// caed.uga.edu/publications/2007/pdf/FR-07-03-pdf. [114] Energy Information Administration, Office of Integrated Analysis and Forecasting, Petroleum Diesel Cost From National Energy Modeling System Run AEO 2004. D101703E, Washington, DC (2003). [115] R. Teall, Study to Evaluate the Feasibility of Biodiesel Production Facilities in Nevada and Califorina Utilizing Grease Trap and Waste Cooking Oils as Feedstock, Biodiesel Industries, Las Vegas, NV (19 March 2002), Appendix #3 – Feasibility Study, pp. 38–42. [116] Energy Information Administration, Annual Energy Outlook 2004, DOE/EOA0383, Washington, DC (2004). [117] USDA Foreign Agricultural Service, Oilseeds: World Markets and Trade, USDA, Washington, DC (Sept. 2008). [118] A. Cave, Biofuel boom pushing up prices, Oils & Fats Intl. 23(7) (2007) 21–2.

710

Biodiesel science and technology

[119] A. Ramli, Price prospects for selected oils and fats in 2005, Palm Oil Dev. 42 (June 2005) 43–5. [120] H.W. Lüke, BTL – Kraftstoffe: Eine vielversprechende Option für die Zukunft, Erdoel, Erdgas & Kohle 121 (2005) 3–14. [121] X. Lang, A.K. Dalai, N.N. Bakshii, M.J. Reaney and P.B. Hertz, Preparation and characterization of biodiesels from various bio-oils, Bioresour. Technol. 80 (2001) 53–62. [122] G. Antolín, F.V. Tinaut, Y. Briceño, V. Castaño, C. Pérez and A.I. Ramirez, Optimisation of biodiesel production by sunflower oil transesterification, Bioresour. Technol. 83 (2002) 111–14. [123] J.W. Kram, No need to splash, Biodiesel Mag. 5(2) (2008) 56–61. [124] W. Schulz, The costs of biofuels, C&EN 85(51) (17 Dec. 2007) 12–16. [125] M. Johnston and T. Holloway, A global comparison of national biodiesel production potentials, Environm. Sci. Technol. 41 (2007) 7967–73. [126] C. St. James, Argentina’s burgeoning biodiesel industry, Biodiesel Mag. 5(9) (2008) 86–9. [127] Y.M. Choo, A.N. Ma, K.Y. Cheah, A.M. Rusnani, A.K.C. Yap, H.L.N. Lau, S.F. Cheng, C.L. Yung, C.W. Puah, M.H. Ng and Y. Basiron, Palm diesel: green and renewable fuel from palm oil, Palm Oil Dev. 42 (2005) 3–7. [128] B.K. Barnwal and M.P. Sharma, Prospects of biodiesel production from vegetable oils in India, Renew. Sustain. En. Revs. 9 (2005) 363–78. [129] M.J. Haas, A.J. McAloon, W.C. Yee and T.A. Foglia, A process model to estimate biodiesel production costs, Bioresour. Technol. 97 (2006) 671–8. [130] J.W. Kram, Improving the bottom line on the front end, Biodiesel Mag. 5(9) (2008) 80–4. [131] G.G. Pearl, Biodiesel production in the US, Render Mag. (Aug. 2001); http:// www.rendermagazine.com/August2001/TechTopics.html. [132] S. Ghosh, D.K. Bhattacharya and P. Dey, Acid oils as raw materials for biodiesel, J. Oil Technol. Assoc. India 30 (1998) 8–9. [133] M.J. Haas, Improving the economics of biodiesel production through the use of low value lipids as feedstocks: vegetable oil soapstock, Fuel Proc. Technol. 86 (2005) 1087–96. [134] R.G. Nelson, S.A. Hower and J.A. Weber, Potential feedstock supply and costs for biodiesel production, in Bioenergy ’94, Proc. 6th Natl. Bioenergy Conf., Reno/ Sparks, NV (1994). [135] M. Noordam and R. Withers, Producing biodiesel from canola in the Inland Northwest: an economic feasibility study, Idaho Agricultural Experimental Station Bulletin No. 785, University of Idaho College of Agriculture, Moscow, ID (1996). [136] M. Bender, Economic feasibility review for community-scale farmer cooperatives for biodiesel, Bioresour. Technol. 70 (1999) 81–7. [137] R.A. Korus, D.S. Hoffman, N. Bam, C.L. Peterson and D.C. Drown, Transesterification process and manufacture of ethyl ester from rapeseed oil, in Proc. 1st Biomass Conf. of the Americas: Energy, Environment, Agriculture and Industry, Burlington, VT (1993), Vol II, pp. 815–26. [138] J.M.N. Van Kasteren and A.P. Nisworo, A process model to estimate the cost of industrial scale biodiesel production from waste cooking oil by supercritical transesterification, Resour. Conserv. Recycl. 50 (2007) 442–58. [139] C.V. McNeff, L.C. McNeff, B. Yan, D.T. Nowlan, M. Rasmussen, A.E. Gyberg,

Sustainability and use of biodiesel

711

B.J. Krohn, R.L. Fedie and H.R. Hoye, A continuous catalytic system for biodiesel production, Appl. Catal. A: Gen. 343 (2008) 39–48. [140] A.H. West, D. Posarac and N. Ellis, Assessment of four biodiesel production processes using HYSYS. Plant, Bioresour. Technol. 99 (2008) 6587–601. [141] Y. Zhang, M.A. Dubé, D.D. McLean and M. Kates, Biodiesel production from waste cooking oil: 1. Process design and technological assessment, Bioresour. Technol. 89 (2003) 1–16. [142] E. Lotero, Y. Liu, D.E. Lopez, K. Suwannakarn, D.A. Bruce and J.G. Goodwin Jr, Synthesis of biodiesel via acid catalysis, I&EC Res. 44 (2005) 5353–63. [143] M. Frondel and J. Peters, Biodiesel. A new eldorado?, En. Policy 35 (2007) 1675–84. [144] D. Coltrain, Biodiesel: Is it worth considering? in Proc. Risk and Profit Conf., Manhattan, KS (15–16 Aug. 2002). [145] A. Demirbaş, Biodiesel production from vegetable oils via catalytic and noncatalytic supercritical transesterification methods, Progr. En. Combust. Sci. 31 (5–6) (2005) 466–87. [146] Y. Basiron, Biofuel, an alternative fuel in the Malaysian scenario, Palm Oil Dev. 42 (June 2005) 1–2. [147] M.J. Haas and K.M. Scott, Diesel fuel as a solvent for the lipase-catalyzed alcoholysis of triglycerides and phosphatidylcholine, J. Am. Oil Chem. Soc. 73 (1996) 1497–504. [148] G. Üstün, Separation of fatty acid methyl esters from tall oil by selective adsorption, J. Am. Oil Chem. Soc. 73 (1996) 203–10. [149] D. Tapasvi, D. Wiesenborn and C. Gustafson, Process model for biodiesel production from various feedstocks, Trans. ASAE 48 (2005) 2215–21. [150] G. Knothe, Other uses of biodiesel, in The Biodiesel Handbook (G. Knothe, J. Van Gerpen and J. Krahl, eds), AOCS Press, Urbana, IL (2005), pp. 229–40. [151] J.W. Kram, Gallons of megawatts, Biodiesel Mag. 5(5) (2008) 76–80. [152] R. Talley, Biodiesel: a compelling business for the rendering industry, Render Mag. (Feb. 2004); http://www.rendermagazine.com/February2001/TechTopics. html. [152a] Pike Research LLC, Biofuels Markets and Technologies, Boulder, CO (2009). [153] F. Gunstone, Oils and fats: supply, demand and biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [154] R. Garofalo, European perspective: overview of the biodiesel industry in Europe, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [155] United States Department of Agriculture, Production Estimates and Crop Assessment Division of Foreign Agricultural Service, EU: Biodiesel Industry Expanding Use of Oilseeds, USDA, Washington, DC (2003); http://www.biodiesel.org/resources/ reportsdatabase/reports/gen/20030920_gen330.pdf. [156] J. Evans, Taxing time for European biodiesel, Biodiesel Mag. 5(6) (2008) 87–91. [157] C. Bomb, K. McCormick, E. Deurwaarder and T. Kåberger, Biofuels for transport in Europe: lessons from Germany and the UK, En. Policy 35 (2007) 2256–67. [158] German Government, Die Kraftstoffstrategie: Alternative Kraftstoffe und Innovative Antriebe (2004); http://www.bmvbw.de/. [159] British Government, UK Report to the Commission on Biofuels (2004); http:// europa.eu.int/. [160] Mineralölwirtschaftsverband (MWV), Möglichkeiten und Grenzen alternativer Kraftstoffe, Berlin (2004); http://www.mwv.de.

712

Biodiesel science and technology

[161] UK Petroleum Industry Association (UKPIA), Biofuels in the UK, London (2005); http://www.ukpia.com. [162] A. Fröhlich and B. Rice, Evaluation of recovered vegetable oil as a biodiesel feedstock, Irish J. Agr. Food Res. 44 (2005) 129–39. [163] M.-C. Hénard, GAIN Report-FR6005, USDA Foreign Agricultural Service, Paris (2006). [164] J.W. Kram, The end of the ‘splash and dash’? Biodiesel Mag. 4(10) (2007) 82–7. [165] C.A. Johnson, Biodiesel production trends survey 2008, Biodiesel Mag. 5(5) (2008) 38–42. [166] J. Tickell, Biodiesel America, Yorkshire Press, Ashland, OH (2006). [167] M. Blagoev, S. Bizzari, R. Gubler, C. Funada and Z. Yi, Biodiesel Report 2008, SRI Consulting, Stanford, CA (Sept. 2008). [168] M. Boyd, A. Murray-Hill and K. Schaddelee, Biodiesel in British Columbia. Feasibility Study Report, WISE Energy Co-op/Eco Literacy Canada (2004). [169] G.P.A.G. Pousa, A.L.F. Santos and P.A.Z. Suarez, History and policy of biodiesel in Brazil, En. Policy 35 (2007) 5393–8. [170] Ministry of Mines and Energy, Brazilian Energy Balance, Brasilia (20 Dec. 2006). [171] R. Hirsch, Biodiesel in Brazil: An Energy Industry. Rabobank Industry Note 1832006, Rabobank International, The Netherlands (2006). [172] A.C. Pinto, L.L.N. Guarieiro, M.J.C. Rezende, N.M. Ribeiro, E.A. Torres, W.A. Lopes, P.A.P. Pereira and J.B. Andrade, Biodiesel: an overview, J. Brazil Chem. Soc. 16 (2005) 1313–30. [173] J.P. Sant’anna, Biodiesel alimenta motor da economia, Quim. Deriv. 416 (2003) 8–18. [174] G.S.C. Barros, A.P. Silva, L.A. Ponchio, L.R.A. Alves, M. Osaki and M. Cenamo, Custo de produção de biodiesel no Brasil, Rev. Polit. Agríc. 15(3) (2006) 36– 50. [175] H.R. Gran, N.I. Gasparri and T.M. Aide, Agriculture expansion and deforestation in reasonably dry forests of north-west Argentina, Environm. Conserv. 32(2) (2005) 140–8. [176] C. St. James, Estado de la industria argentina de biodiesel, www. argentinarenovables. org (Sept. 2009). [177] S. Asal, R. Marcus and J.A. Hilbert, Opportunities for and obstacles to sustainable biodiesel production in Argentina, En. Sustain. Developm. 10(2) (2006) 48–58. [178] P. Lamers, K. McCormick and J.A. Hilbert, The emerging liquid biofuel market in Argentina: implications for domestic demand and international trade, En. Policy 36 (2008) 1479–90. [179] L. Panichelli, Análisis de ciclo de vida (ACV) de la producción de biodiesel (B100) en Argentina, Graduate School of Agronomy, University of Buenos Aires, BA (2006); http://www.inta.gov.ar/iir/info/documentos/energia/panichelli2006.pdf. [180] http://www.maizar.org.ar/vertext.php?id=214. [181] W. Thurmer, Biodiesel 2020: A Global Market Survey, Emerging Markets Online, Houston, TX (2008).

15

Evolution of biodiesel and alternative diesel fuels

Abstract: First-generation liquid biofuels such as biodiesel (via transesterification) and bioethanol suffer from various limitations, foremost limited access to foodstocks. Second-generation biodiesel and renewable diesel substitutes require alternative feedstocks, which can be produced without interference with edible agricultural crops. Development of these energy crops in commercial quantities still requires at least five years. Breakthrough catalyst technologies are already available. Technological developments based on hydroprocessing have led to commercialisation of second-generation alkane-based renewable diesels based on the same feedstocks as biodiesel, namely vegetable oils and animal fats. Nextgeneration renewable diesels will be biomass-based without the present supply limitations. Gas-to-liquid (GTL) and biomass-to-liquid (BTL) technologies are still under development. Key words: Renewable synthetic diesels, breakthrough catalyst technologies, hydroprocessing, gas-to-liquid (GTL) technologies, biomass-to-liquid (BTL) technologies.

15.1

Introduction

The need for new fuel technologies and feedstock in diesel production derives from the growing number of diesel vehicles, the increased demand for cleaner diesel fuels and finite diesel fuel resources. To enable and encourage growth of the renewable fuel industry, many national, federal and state governments are assisting in the effort in the form of incentives and policies (see Chapter 1). Until recently, there has been only one chemistry available for renewable diesel, namely transesterification (see Chapter 7), but more options are now available. Figure 15.1 shows chemistry in transition. During the last century the chemical industry has made great strides to turn hydrocarbons into more functionalised, and therefore more useful, chemicals. Catalytic oxidation is the basis of most bulk and fine chemicals and is generally a difficult process step. This process step is no longer required for a feedstock such as biomass with its added oxygen functionality. The industrial metamorphosis from hydrocarbons to carbohydrates (biomass) as raw material requires a rethinking of process technology. The transformation requires new catalysts (biocatalysts such as enzymes, bacteria and other microorganisms). Here, 713

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Chemical feedstock

Coal

Oil/gas

C

C, H

Biomass

C, H, O

Cat -refi

oxi dat

Refining

Bio

tic

nin

g

aly

UCG

ion Bulk and fine chemicals Energy carriers

Syngas

Fossil fuels

Transesterification

Gasification

Reforming Renewable fuels

Hydrogen

15.1 Chemistry in transition.

just as much as in the development of crops specific to biofuels production, genomics will play a central role. There is also a need to improve fermentation technologies, to develop larger-scale bioreactors, and to integrate these in biorefineries. Bioprocesses hold promise of cleaner and safer production as they can be used at atmospheric pressure and room temperature in aqueous environments. The transition from oil/gas to biomass as a chemical feedstock will be comparable to that of coal to oil/gas. Figure 15.1 also implicitly describes the history of energy systems and denotes that they are becoming ever more chemical. Conventional energy systems can still be greatly improved but their conversions require planning at a time scale of 20–50 years. During the 21st century the world is likely to witness a reversal of the trends observed in the 20th century, whereby (non-renewable) fossil-based hydrocarbons took over from (renewable) biomass-based carbohydrates (both for chemical and fuel applications). This happened in a matter of decades. The same is likely to occur with the bioeconomy. Mankind consumes about 13 TW of energy per year, with approximately 80% being provided by fossil fuels. Out of the total incident solar energy reaching the earth’s surface (~ 173 000 TW) photosynthesis captures about 140 TW of energy as biomass. Figure 15.2 illustrates modern technologies for biomass conversion. Biomass is comprised primarily of carbohydrates (e.g. starch and cellulose), and one method to convert these compounds to liquid fuels is by fermentation to produce liquid alcohols, such as ethanol and butanol. The technology to convert grain-derived starches to ethanol by the combination of hydrolysis, fermentation and distillation is well established [1, 2], and advances are being made in the cost-effective conversion of

Evolution of biodiesel and alternative diesel fuels Herbaceous cultivation

Annual

715

Arboreous cultivation

Perennial

Lignocellulosics

Thermochemical conversion Gasification, pyrolysis, combustion

Carbohydrates

Biochemical conversion Bio-gasification, fermentation, enzymatic hydrolysis

Vegetable oils

Chemical conversion Transesterification, hydrotreatment

15.2 Technologies for biomass conversion. Table 15.1 First-generation (conventional) biofuels Biofuel type

Specific name

Biomass feedstock

Production process

Pure vegetable Pure plant oil (PPO) Vegetable oil crops Cold pressing/extraction oil Bioethanol

Conventional bioethanol

Bio-ETBE

Sugar beets, grains

Hydrolysis and fermentation

Bioethanol

Chemical synthesis

Biodiesel

Biodiesel from Vegetable oil crops Cold pressing/extraction energy crops and transesterification Fatty acid methyl/ ethyl ester (FAME/FAEE), e.g. rapeseed methyl ester (RME)

Biodiesel

Biodiesel from waste Waste/cooking/frying Esterification and FAME/FAEE oil transesterification

Biogas

Upgraded biogas

(Wet) biomass

Digestion

lignocellulosics to ethanol [3]. The current high cost of cellulase enzymes is the key barrier to economical production of bioethanol from lignocellulosic material. There exists a range of biofuels with different feedstocks and conversion processes (Table 15.1 and Fig. 15.3). At present, the only biofuels that can be supplied in considerable amounts are first-generation bioethanol (from sugarcane and corn) and biodiesel. Current concerns regarding many firstgeneration biofuels are that they:

716

‘Sugary’ plantsb

‘Amylaceous’ plantsc

Lignocellulosic materiald

Pre-treatment

Extraction

Extraction

Purification

(Trans)esterification

Purified oil

Biodiesel

Hydrolysis

Gasification

Fermentation (enzymatic)

Purification

Distillation/dehydration

Catalytic synthesis

Bioethanol

Biomethanol

15.3 Biofuel production processes (a = soy, rape, palm; b = beet, sugarcane; c = corn, wheat, sweet potato; d = grass, wood).

Biodiesel science and technology

Vegetable oils and fatsa

Evolution of biodiesel and alternative diesel fuels

∑ ∑ ∑ ∑ ∑ ∑ ∑

717

do not meet their claimed environmental benefits unless the biomass feedstock is produced sustainably; are accelerating deforestation (with other negative indirect land-use effects); have a potentially negative impact on biodiversity; compete for scarce water resources; provide only limited greenhouse gas (GHG) reduction benefits (except for sugarcane ethanol) at high costs; are an expensive option for improving energy security; and contribute to higher food prices.

In particular, some much acclaimed negative environmental impacts of sourcing biodiesel from large-scale virgin feedstock cultivation include use of destructive land-use practices, fertilisers and pesticides, ravage to (marine) ecosystems, and GHG and toxic air emissions resulting from onfarm operations. First-generation liquid biofuels are characterised by limited biomass conversion efficiencies (only partial use of plant matter, much waste production and modest yield per cultivated area), limited energy efficiency, high production costs, food-crop derived and non-fuel by-products. In particular, conventional biodiesel production suffers from: ∑ high costs (70.4–0.7/L); ∑ limited productivity; ∑ stability and storage problems (presence of oxygenated groups); and ∑ glycerol co-formation. The presence of the co-product glycerol (10 lbs per 100 lbs conventional biodiesel) poses severe problems. With the current overcapacity of this product, it is mandatory to convert glycerol to fuels or to bulk chemicals (alcohols, glycols, etc.) (see Chapter 13). The overall energy balance for production of bioethanol (except for sugarcane ethanol) is not very favourable, and it has been estimated that the amount of energy required to produce bioethanol is approximately equal to (or greater than) the energy content of the ethanol produced [1, 2, 4]. Moreover, production of bioethanol creates more CO2 than is saved when it is substituted for petrol. Although biodiesel is the most sustainable heavy-duty transportation fuel in the world, the industry is under attack by issues related to food price rises and indirect land use. Quantifying indirect land use presents two significant challenges: determining how much production would rise from increased land use and evaluating the yield potential of more efficient farming practices. It should be acknowledged that using the most advanced farming practices on a global scale could generate some 7 Bgy (or 23 Mt) of vegetable oil without introducing new acres into production to the benefit of food/feed/fuel/applications alike. At the same time, intensive farming

718

Biodiesel science and technology

requires a combination of systems and methods for efficient and sanitary disposal of agricultural waste, producing usable energy and products. In US Pat. Appl. No. 2003/0111410, Branson [5] describes an integrated system for the transformation of general farming waste streams (including animal carcasses, vegetation and animal waste) into syngas, electricity and liquid feedstock products (methanol, methyl esters, glycerol), based on conventional technology (Fig. 15.4). The methyl esters, obtained as a green product, may find application as an additive for the petrochemical or plastics industries or as biodiesel. More generally, Fig. 15.5 illustrates the biorefinery concept with biochemical and (thermo)chemical processing. Biorefineries may be designed to produce a range of co-products, some being low-volume, high-value products, and others, like biofuels, being high-volume, low-value. In the early stages of a biorefinery, value-added chemicals may be extracted from the biomass before focusing on further processing into feedstocks for biofuels. Figure 15.6 shows oil seeds in a biorefinery context. Agricultural waste

Anaerobic digestion

Biogas (CH4, CO2)

Steam reforming

Fertiliser

Syngas

MeOH

Electricity

Fats oils

FAME

Glycerol

15.4 Integrated system for transformation of agricultural waste to liquid feedstock products. Sugars

Biomass

Collection

Separation and pre-treatment

Carbohydrates ∑ Starch ∑ Cellulose ∑ Hemicellulose

Fermentation Alcohols (EtOH, BuOH) Enzymatic hydrolysis

Lignin

Cyclic hydrocarbons

Lipids

FAME Linear alkanes

Thermal processing

Pyrolysis oil

Syngas

15.5 General scheme of a biorefinery.

Hydrocarbons

Alcohols, FT fuels

Evolution of biodiesel and alternative diesel fuels

719

Oil seed Extraction

De-oiled cake (DOC)

Extract Lecithin Minor components Tocols Carotenoids Sterols

Proteins Concentrates Isolates Hydrolysates Anti-nutritional factors (pharma applications)

Oil Polysaccharides/starch Edible oils

‘Transformed oils’

Derived products

15.6 Oil seeds in a biorefinery context.

15.2

Second-generation biofuels

First-generation biofuel technologies have reached a high degree of maturity. Many of the concerns associated with first-generation biofuels can be addressed by production of biofuels manufactured from agricultural and forest residues and from non-food crop feedstocks. These second-generation biofuels, which are relatively immature and still face considerable technical barriers, present greater cost reduction potential in the longer term [6]. While the focus of first-generation biofuels has been mainly on resources, for the second generation it will shift to developing new technology. Secondgeneration technologies will maximise the use of existing infrastructure, use low-cost and sustainable feedstocks, reduce dependence on food crops as fuel feedstocks, and minimise the carbon footprint. In particular, secondgeneration biofuels are characterised by: ∑

use of non-food crops (agricultural and urban waste) and lignocellulosic mass; ∑ development of innovative energy crops; and ∑ improvement of energy and carbon balance of existing technologies. Advanced biofuels are thus expected to be derived largely from energy crops grown on marginal land (e.g. jatropha, switchgrass), short-rotation woody crops (e.g. willow, poplar), unused or new agricultural and forestry residues (wood chips, corn stover, wheat straw), as well as waste products (algae, sewage) not required for food. The goal is to develop next-generation renewable sources that are viable over the long term, both economically and

720

Biodiesel science and technology

environmentally. Mid-GHG biofuels are based on best current technologies. Low-GHG biofuels (cellulosic ethanol based on poplar, switchgrass, or mixed prairie grasses, residues, wastes) are in development or pilot phase. In more advanced technologies conversion of all parts of the biomass, including the lignocellulosics, is considered as a source for energy, biofuel and materials. A variety of bio-based fuels are possible products of these routes (hydrogen, methanol, ethanol, butanol, 2,5-dimethylfuran, dimethylether) (Table 15.2). Total (France) investigates the feasibility of using DME as a fuel. The compound will be made by gasifying black liquor – a waste product of pulp manufacturing. DME can also be made from other forms of biomass, as well as from coal or natural gas. DME is easier and cheaper to produce than biodiesel, and engines only require minor modifications to run on the fuel. Avantium (Shell spin-off, Amsterdam) is developing a novel furan-based biofuel (called Furanics) derived from hydroxymethylfurfural (HMF) [7, 8]. Furanics (hetero-aromatics) is considered as a next-generation biofuel with superior characteristics (including miscibility with fossil diesel). Furfural and HMF can serve as a building block for other transportation fuels, such as dimethylfuran and ethyl levulinate. Biomass (fructose or glucose)derived 2,5-dimethylfuran (DMF) is a promising fuel agent with a 40% higher energy density than ethanol [9]. Biomethanol is methanol produced from biomass (wood waste, black liquor, methanol gas from animal waste Table 15.2 Second-generation biofuels Biofuel type Specific name Biomass feedstock Production process Bioethanol Cellulosic bioethanol Lignocellulosics

Advanced hydrolysis and fermentation

Synthetic biofuels Biomass-to-liquids (BTL) Lignocellulosics Fischer–Tropsch (FT) diesel Fischer–Tropsch (FT) gasoline Synthetic (bio)diesel Biomethanol Heavier (mixed) alcohols Biodimethylether (Bio-DME)

Gasification and synthesis

Biodiesel NExBTL

Hydrogenation, isomerisation

Biogas

Vegetable oils and animal fats

SNG (Synthetic Natural Lignocellulosics Gas)

Gasification and synthesis

Biohydrogen Lignocellulosics

Gasification and synthesis or biological process

Evolution of biodiesel and alternative diesel fuels

721

and landfill, sugar beet pulp and glycerol). Biobutanol (test production from sugar beet for 2009–10) is poorly soluble in water and highly compatible with conventional engines. It is of interest to notice that a strain of E. coli is able to produce various long-chain alcohols (C5-C8) via a non-natural biosynthetic pathway [10]. Biogas is a fuel from organic substances by biological processes. Most biogas is used for heating or co-generation purposes. Few countries (mainly Sweden, France) use biogas in transportation. For the purpose of powering motor vehicles all undesirable chemicals (CO2, H2S, etc.) must be removed. Refining biogas (from sludge or water treatment plants, waste disposal sites, industrial wastewater and co-fermentation stations) to the quality of natural gas is costly. Future biofuel technology developments comprise: ∑ ∑ ∑ ∑

Optimisation of existing technologies – Process improvements (catalysts, separation units, reactors, etc.) – More efficient processes (energy, water) – Better integration in the territory – Variation of feedstock. New renewable diesel technologies – Hydroprocessing – Biotechnological production processes – Integration with existing processes. Ethanol from cellulose – Use of lignocellulosic materials – Combinations of biological and thermochemical routes. Synthetic fuels from biomass.

Processes under development for next-generation biofuels include: ∑

gasification of biomass, followed by Fischer–Tropsch (FT) and mild hydrocracking (‘biomass-to-liquids’, BTL); ∑ enzymatic production of bioethanol from sugar components of plants and from (hemi)cellulose; and ∑ enzymatic generation of more suitable biofuels than bioethanol, e.g. biobutanol. R&D focus is on gasification of biomass, genetic optimisation of plants and biocatalysis. Thermochemical (pyrolysis/gasification) technologies, which produce syngas from which a wide range of long carbon chain biofuels such as synthetic diesel or aviation fuel can be reformed, are essentially energy wasteful processes. Hydrothermal upgrading (HTU) allows the use of high moisture content organic waste material; HTU typically uses 25% biomass in liquid water at 573–628 K and 12–18 MPa, to yield 45% biofuel, 25% gas (>90%

722

Biodiesel science and technology

CO2), 20% water and 10% dissolved organics with a thermal efficiency of 70–90%. Fermentation of syngas to alcohol is slow and inefficient. By replacing biological processes such as fermentation with more conventional catalytic methods, the conversion of sugars to fuel might be greatly accelerated. Thermochemical and biochemical routes have different optimum plant sizes, feedstock costs, by-products (which may add value), output fuels, and relationships to existing industry. The economics and sustainability of the two core technologies – biochemical and thermochemical routes – for nextgeneration biofuels are contentious. Gasification appears to be the cheaper system. However, fermentation can better exploit the full economic value of the wide range of substances within biomass. Fermentation works best for biofuel production from single streams. Second-generation technologies for the conversion of plant biomass are of great importance when it comes to striking the proper balance between food production, chemicals development and bio-energy. The focus is shifting from food-crop derived biofuels to a generation of fuels derived from agricultural and urban waste material. Steam reforming of all the US solid waste would secure some 66% of the nation’s total oil supply. Second-generation biofuels offer a number of advantages: ∑

use of a wider range of raw materials than just oilseeds, especially waste (with significantly lower feedstock costs and geographical restrictions); ∑ high-quality and clean-burning fuels, with potentially a much lower well-to-wheels CO2 profile than other liquid fuel options; ∑ less intensive cultivation process (if any) than for ordinary agricultural crops, resulting in lower GHG emissions; and ∑ co-production with electricity. The return-on-investment (ROI) point of second-generation bioethanol (from cellulose) and biodiesel (from vegetable oils) is approaching. A first commercial second-generation bioethanol plant (Range Fuels) from lignocellulosic waste will be operating in Soperton, GA, as from 2010. In the US some 20 cellulosic ethanol plants are now under construction despite the fact that the technology has not yet been optimised. Meanwhile, the US Department of Energy (DOE) is investing in three bioenergy centres (located in Oak Ridge, TN; Madison, WI; and Berkeley, CA; operational by 2009), which will work on converting cellulose in different plant crops to fuels. The Obama administration is strongly focusing on the development of second-generation technologies. Figure 15.7 shows the EU roadmap for development of biofuels for the 2005–50 period. Also the EU biomass fuel action plan heavily focuses on second-generation biofuels. On the basis of the principal biomass resources (agricultural, forestry) and additional secondary resources (waste products

Evolution of biodiesel and alternative diesel fuels

723

2050

2020 Integrated biorefining complexes 2010 EtOH, Syn Diesel, DME (Second generation) From lignocellulosic biomass 2005 Improving present processes (First generation) EtOH, ETBE, FAME, FAEE

15.7 Roadmap for the future development of biofuels (Source: European Commission, 2006).

of agro, food and wood transformation industries, organic waste) of the EU28, an estimated potential biofuel production capacity of 174 Mt (import included) may be envisaged by 2030. Among the objectives of the Bioenergy Implementing Agreement of the International Energy Agency (IEA/BA) Task no. 39 (Liquid Biofuels from Biomass) for the 2004–06 period was identification of technological barriers to the development of biofuels, in particular the ‘second generation’. Biodiesel equivalents can be derived from (trans)esterification, vegetable oil hydrogenation, pyrolysis, or by biomass-to-liquid (BTL) processes. It is likely that BTL diesel, which is chemically different from vegetable oil biodiesel, will see the most attention over the coming years, especially in Europe. Huge initial investments are required. A whole crop biorefinery will optimise the production of biofuels to lower production costs. With increasing fossil fuel prices and as a result of better enzymatic hydrolysis and ethanol processing, bioethanol prices might become competitive with gasoline by 2010. The transition to second-generation biofuels will require one or two decades. Once second-generation biofuel technologies are fully commercialised (after 2020), it is likely that they will be favoured over many first-generation alternatives. This may lead to lower levels of investment into first-generation technology and production plants. However, sugarcane ethanol and soy biodiesel are expected to play a continuing role in future biofuel demand. In the mid to long term the global biofuels market will thus be characterised by a balance between first- and second-generation technologies. Although wider deployment of commercial-scale second-generation biofuels operations are expected between 2015 and 2020, their contribution to the global transport fuel demand by 2030 is expected to be still rather modest. In this chapter we will consider several recent noteworthy industrial developments such as the optimisation of solid-catalyst transesterification

724

Biodiesel science and technology

technology and renewable diesel by hydroprocessing. The current status of biomass-to-liquid (BTL) fuels via gasification technologies will be outlined. Finally, the prospects for production of biodiesel equivalents by microbial biosynthesis of renewable plant materials will be considered. Similarly, other developments, such as the production of biobutanol from lignocellulosic biomass by hydrolysis and fermentation (BP/DuPont and British Sugar) of sugar beet are still immature. Potential breakthroughs are the cultivation of energy-only crops (e.g. Jatropha curcas in India/Indonesia, switchgrass in the US) and production of diesel from algae.

15.3

Biodiesel: the next generations

The technologies and systems for conventional first-generation biodiesel, based largely on refined edible oils from traditional farming of soil-based crops and homogeneous catalysts, are relatively mature [11]. There are possibilities for incremental improvements through economies of scale and learning effects. The main production cost is the price of the feedstocks, mainly agricultural crops. A strategy to achieve cost/price developments is to focus production in favourable climates, which for Europe translates to imports from Brazil (future) and Argentina. However, many member states have adopted policies that restrict imports of biofuels from favourable climates. Consequently, in order to achieve reductions in costs/prices, investment in more advanced biodiesel technologies is required. Table 15.3 shows various generations of biodiesel transesterification technology. More advanced second-generation transesterification processes have recently been introduced, variously using lower-cost feedstocks and/or optimised processing modes. The long-term viability of the biodiesel industry needs to extend the range of feedstocks beyond valuable agricultural crops in order to avoid interference with the food chain. The demands for biodiesel Table 15.3 Generations of biodiesel transesterification technologya Generation

Resources

Technology

First

Refined edible oils, animal fats Homogeneous catalysts

Second Non-refined, high FFA oils, multi-feedstock

Breakthrough catalyst developments Heterogeneous transesterification Solid esterification Selective hydrogenation Technological breakthroughs New reactor concepts Process optimisation

Third

As above

a

Innovative non-food energy crops

Product: FAME.

Evolution of biodiesel and alternative diesel fuels

725

create new opportunities and stimulate fresh investment in the production of lower-cost, alternative feedstocks such as used vegetable oils and tallow, and high-yield feedstocks, such as jatropha and algae, which will be available in commercial quantities in the near or more remote future. Next-generation biodiesel will thus probably be based increasingly on innovative non-edible feedstock, i.e. non-food crops and aquatic resources. Alternatively, Sweden is looking at producing biodiesel from wood extractives; a 50 kt/yr plant is being designed. This is a new feedstock almost entirely based on free fatty acids. Consequently, in this case little glycerol is produced and the major by-product is resin acids, which is a valuable base chemical. Limits of the current biodiesel processes are several, comprising participation of alkaline catalysts in the esterification reaction, occurrence of side-reactions and of impurities in the product stream, and the need for complex purification steps (especially in the glycerol path). Although biodiesel is a green product, it is currently not being manufactured in a green process. Next-generation biodiesel is inherently stable at cold temperatures and does not break down during storage and transport like conventional biodiesel. Biodiesel process intensification may be achieved by: (i) innovative catalyst developments; and (ii) technological breakthroughs. Recent advanced catalyst technology is described in Section 15.3.1. It is apparent that highperformance heterogeneous catalysts are now available industrially for (trans) esterification of low-quality, high FFA content feedstocks (see Table 15.6) and allow important simplification of the production schemes. Advanced biodiesel process technology also takes advantage of new reactor concepts, such as STT technology or the ShockWave Power™ reactor, which drives the transesterification reaction toward completion in seconds and provides the ability to achieve total glyceride levels of less than 0.05% in the final biodiesel product (see Section 7.3.2, pp. 303–4). The ShockWave Power reactor SPR BD50 is designed to produce 50 Mgy of biodiesel. The in-situ transesterification reaction is an interesting alternative to obtain biodiesel and decrease costs. Reactive extraction avoids the extraction, degumming, neutralisation, oil washings and pre-treatment steps. Portable biodiesel plants will contribute to biodiesel process intensification. Other recent, technologydriven, developments are described in Sections 7.3.2, 11.2 and 11.2.4. Whereas ester biodiesel is maturing, the bio-based diesel industry is essentially still in its infancy, as shown in Table 15.4. Technologies for non-ester renewable diesel (NERD) fuels fall into three broad categories: hydrotreating, gasification/Fischer–Tropsch (thermal depolymerisation) and enzymatic biotechnological (Fig. 15.8). While many fungi are known to produce octane, 1-octene and lower molecular mass hydrocarbons [12, 13], it was only recently discovered that the endophytic fungus Gliocladium roseum (NRRL 50072) is able to convert substrates such as cellulose directly into a diesel-like mixture of medium-chain hydrocarbons (termed ‘myco-diesel’) [14]. These

726

Biodiesel science and technology

Table 15.4 Alternative renewable diesel fuel generationsa Generation Resources

Technology

First Vegetable oils, animal fats Transesterification Second Vegetable oils, animal fats Hydroprocessing Third Lignocellulosics Gasification/FT Fourth Cellulosics Enzymatic a

Diesel fuel composition Fatty acid esters Paraffins Paraffins Fatty acid estersa, hydrocarbonsb

Microdiesel (see Section 15.3.3). Myco-diesel.

b

developments, which enable generation of products that fit into the existing infrastructure, provide alternatives to biodiesel. Table 15.5 [15] shows the time-frame of the more mature bio-based diesel fuel technologies. The term ‘biodiesel’ is restricted to transesterified vegetable oils. Consequently, hydrodiesel or biomass-derived Fischer–Tropsch diesels are bio-based diesel fuels, which do not qualify as biodiesel (Table 15.5). Some jurisdictions have inadvertently limited renewable diesel to the existing ester chemistry. Advanced bio-based diesels, such as hydrodiesel, allow a transition from mid-GHG to low-GHG (See Section 15.4.1). At present, hydrodiesel is competing with biodiesel for the same vegetable oil feedstock (see Section 15.4).

15.3.1 Breakthrough catalyst technologies While traditional homogeneous catalysis in biodiesel production offers a series of advantages, its major disadvantage is the fact that the catalyst cannot be reused. Moreover, catalyst residues have to be removed from the ester product, usually necessitating several washing steps that increase production costs. There are various successful developments at simplifying product purification by applying heterogeneous catalysts that can be recovered or are used in fixed-bed arrangements (Table 15.6). Requirements of heterogeneous catalysts are slow decrease in efficiency after reuse, and no negative effects by common impurities originating from the oily feedstock (which would require costly feedstock purification). Various commercial biodiesel technologies operate using solid-phase catalysts (e.g. IFP-Axens, NCL, Rohm & Haas). Esterfip-HTM (IFP-Axens) is the world’s first solid-catalyst technology (see below). In PCT Int. Publ. No. WO 2008/135665 to Lecocq et al. [16], IFP has recently disclosed improved heterogeneous catalysts of the phosphate type (such as Zr(O3POK)2) or organophosphorated compounds of Group IV metals (Zr, Hf, or Ti) for transesterification reactions of acidic feedstocks (up to AV = 10 mg KOH/g at 423–453 K and 1–7 MPa) or coupled esterification-transesterification (AV > 10 mg KOH/g), leading to on-spec biodiesel and glycerol of 98–99.9% purity.

Non-ester renewable diesel NERD

Fatty acid monoalkyl esters FAME

Transesterificationa

Batch

Biotechnologicalb

Continuous

Thermal depolymerisation

Hydrotreatingc

Biotechnologicale

Fischer–Tropschd

15.8 Established and new technologies to process renewable diesel substitutes (a = Biodiesel (FAME); b = Microdiesel; c = Hydrodiesel; d = FT-diesel; e = Myco-diesel).

Evolution of biodiesel and alternative diesel fuels

Renewable diesel substitutes

727

728

Biodiesel science and technology

Table 15.5 Different technologies for bio-based diesel fuels (after ref. [15]) Large-scale Process Product Feedstocksa Product Production production quality plant investment > 1995 Transesterification Biodiesel (FAME) – > 2007 Hydrotreating Renewable diesel + (CnH2n+2) > 2015 Gasification + FT-BTL (CnH2n+2) +++ Fischer–Tropsch

– +++

+ –

+++

–––

a

Volume, availability and price. + = benefit – = disadvantage. Table 15.6 Advanced commercial (trans)esterification catalyst technology

Process

Technology provider

Trade mark

Feedstock

Heterogeneous transesterification

IFP-Axens

Esterfip HTM

Refined and used oils/fats

Proprietary

BDI

RepCat

Multi-feedstock (high FFA)

Solid esterification/ Rohm & Haas transesterification

Amberlyst BD20

Solid-phase transesterification

ENSELTM

NCL

TM



High FFA feedstock (up to 100% FFA) Multi-feedstock (high FFA)

Benefuel, Inc. (Mt. Prospect, IL) uses a new, solid-phase catalytic process for transesterification of triglycerides (ENSEL™), followed by conversion of glycerol into glyceryl polyethers in a second process [17]. The dual metal catalyst (DMC) effectively refines a wide range of oil feedstocks, including both vegetable oils and animal fats with high FFA levels. The ENSEL™ process produces the highest quality by-product glycerol in the biodiesel market (97.0–99.9%, depending on the fatty acid content of the triglyceride feedstock). At this level of purity, ENSELTM process glycerol is directly available for further processing steps, such as short-path distillative purification to the highest USP grades, alkylation with solid catalysts to alkylpolyethers, or conversion to propylenediols, epichlorohydrin, etc. As the DMC catalyst is not consumed during transesterification, fuel washing is not needed. In the absence of mineral leaching into the glycerol phase no water at all is required to process the effluent from the continuous-flow reactors. This compares favourably with conventional biodiesel plants which typically require up to five volumes of water per volume of oil feedstock to wash out spent reactants. Mcgyan process technology (see Section 9.3.1) uses a highly efficient heterogeneous metal oxide-based catalyst for conversion of plant oils and

Evolution of biodiesel and alternative diesel fuels

729

animal fats into biodiesel. Catalin Inc. (Ames, IA) is developing a slurry catalyst (T300) based on a non-toxic, common mineral [16a]. Esterfip-HTM technology The Esterfip-H™ process, developed by the French Institute of Petroleum (IFP) [18, 19] and designed and commercialised by Axens, uses a heterogeneous catalyst (the ‘H’), namely a spinel mixed metal oxide (see Section 8.4.1). Esterfip-H™ is a highly efficient, continuous process that produces high-purity biodiesel and glycerol of unequalled purity, while generating practically no waste products [20, 21]. This optimisation of technology combines important product improvements with process innovation, resulting in considerable economical advantages (lower investment costs). Details about production costs are not publicly available. Comparison of the reactions in Figs 15.9 and 13.3 shows greatly simplified heterogeneous transesterification in comparison with homogeneous alcoholysis. The process requires neither catalyst recovery nor aqueous treatment steps. As a consequence also the process scheme is greatly simplified (compare Figs 15.10 and 15.11 with Fig. 11.14). In the continuous Esterfip-H™ process, transesterification is performed at a higher temperature than in the homogeneous-catalysed process, with an excess of methanol. This excess is removed by vaporisation, recycled to the process and combined with fresh methanol. The chemical conversion is reached with two successive fixedbed reactor stages, with glycerol separated to shift the equilibrium. Excess methanol is removed after each reactor by a partial flash. Esters and glycerol are then separated in a settler. Biodiesel is produced after final recovery of methanol by vaporisation under vacuum, then purified to remove traces of glycerol. The purity of methyl esters exceeds 99%, with yields close to 100%. Glycerol phases are joined and the last traces of methanol are removed. Esterfip-H™ directly produces salt-free glycerol at purities exceeding 98%, as compared to about 80% from homogeneous catalyst routes. The quality of the glycerol yield adds to the economics of the process. RCOOCH3

RCOOCH2 Heterogeneous

RCOOCH RCOOCH2 + CH3OH

catalyst

Biodiesel

CH3OH CH2OH CHOH

Glycerol

CH2OH

15.9 Reactions in heterogeneous-catalysed transesterification of vegetable oils (Esterfip-HTM technology).

730

Biodiesel science and technology

Methanol Mineral acid Partially refined vegetable oil

Reactor

Settler

Neutralisation washing

Evaporation

Biodiesel (Diester®)

Catalyst Glycerol purification

Mineral acid

Glycerol

Fatty acids (a) Methanol

Partially refined vegetable oil

Reactor

Settler

Evaporation

Glycerol purification

Biodiesel (Diester®)

Glycerol

(b)

15.10 (a), (b) Heterogeneous transesterification of Esterfip-HTM process.

Esterfip-H™ represents a major advance in the area of biofuels as it ensures the production of biodiesel meeting European specification EN 14214 and US specification ASTM D 6751. The fixed-bed solid-catalyst process enables a significant reduction in waste streams, which are drawbacks of the conventional homogeneous catalytic processes. Table 15.7 summarises the main highlights of the new biodiesel technology. IFP-Axens Esterfip-HTM technology is in principle suitable for refined oils, used frying oils, animal oils and fats and permits producing a biodiesel based on ethyl esters of vegetable oils. The activity of the catalyst is strongly reduced in the presence of water and a water concentration of < 1000–1500 ppm is recommended [22]. No details on catalyst lifetime are available. Esterfip-HTM heterogeneous catalyst technology was released commercially in 2006 and has been licensed first by Diester Industrie (a large farmer-owned biodiesel company) in Sète, France (2006) and a Swedish biodiesel plant (2007). Several more plants are in design or under construction worldwide

Evolution of biodiesel and alternative diesel fuels

731

Partial evap.

Partial evap.

Full MeOH evap.

R1

Purification

R2

Methanol GL

GL

Vegetable oil Glycerol (> 98%)

15.11 Simplified dual-reactor Esterfip-HTM process flow diagram. Table 15.7 Esterfip-HTM process highlights ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Continuous technology based on solid catalyst Simplified process scheme Very high biodiesel (EN 14214, ASTM D 6751) yield (~100%) Exceptional glycerol purity (> 98%) No soap formation or waste production of low-value fatty acids No need for catalyst recovery and washing steps No associated waste saline streams requiring disposal No handling/consumption of hazardous acid/base chemicals Much lower catalyst requirements (per tonne of biodiesel) compared with other processes Allows use of a variety of plant oils: rape, palm, sunflower, soy

(Table 15.8). Axens received the 2007 Kirkpatrick Award for Chemical Engineering Achievement from Chemical Engineering magazine. RepCat technology In 2005 BDI-Biodiesel International AG (Grambach/Graz, Austria) has successfully developed a new (undisclosed) catalyst (presumably Mg stearate, see Section 8.2.1) for industrial-scale production of highest-quality biodiesel which can be reused, avoids residues in the production phases and thus reduces production costs [23, 24]. US Pat. Appl. 2008/0227994 to Glasl et al. [25] to BDI-Biodiesel International relates to a process for the production of fatty acid

732

Biodiesel science and technology

Table 15.8 Axens Esterfip-HTM biodiesel plants Producer

Location, commissioning date

Capacity Feedstock(s) (kt/yr)

Diester Industrie Diester Industrie Diester Industrie Diester Industrie Diester Industrie/Cargill Diester Industrie Perstorp Oxo Beatrice Biodiesel LLCb Mission New Energy Ltd

Sète (F), 2006–08 Montoir-de-Bretagne (F), 2006 Venette/Compiègne (F), 2006 Grand-Couronne (F), 2007 St. Nazaire (F), 2007–08 Le Meriot (F), 2007–08 Stenungsund (S), 2007 Beatrice (Gage County, NE), 2006 Kuantan Port (MAL), 2009

200 250 200 260 250 250 160 165

RSO, RSO, RSO, MFT RSO, RSO RSO, SBO

250

Undisclosed

a

SNO SNO SNO SNOa SNO, SBO

Supplied by Cargill RSO/SNO crushing plant. Recently (autumn 2008) filed for bankruptcy for facility under construction.

b

Table 15.9 Advantages of RepCat technology ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Reusable catalyst system No catalyst residues in products No wastes, no waste water disposal Simplification of product purification Lower production costs Suitable for multi-feedstock use Upgraded biodiesel quality Salt-free, technical-grade glycerol (>96%)

alkyl esters (FAAEs) in high yield by esterification of carboxylic acids and/ or transesterification of carboxylic acid esters with alcohols in the presence of alkaline earth metal salt of a carboxylic acid (typically: Mg stearate) at T = 423–473 K and p < 2 MPa. RepCat catalyst technology allows the use of animal fats and used cooking oils with FFA content even in excess of 20% without the need for blending with clean vegetable oils and without losing the FFA content. BDI claims higher biodiesel quality at lower production cost for multi-feed operations with improved glycerol quality (>96%; cf. >80% for classical homogeneous catalysts for MFT). By complete recycling of the catalyst the by-product is absolute salt free. Advantages of RepCat technology are listed in Table 15.9. Figure 15.12 shows the process flow for a RepCat multi-feedstock plant. The technology is now used industrially in BDI’s 25 kt/yr MFT plant in Arnoldstein (Austria) and elsewere. AmberlystTM BD20 esterification/transesterification technology Standard biodiesel processes are not compatible with high FFA feedstocks. This is because of saponification of the FFAs in the transesterification stage

Animal fat

Used cooking oil

Evolution of biodiesel and alternative diesel fuels

733

Methanol

Fat preparation

Recycle methanol Trans- and esterification

FAME/Glycerol separation

Quality control

Recycled catalyst Fresh catalyst

Biodiesel EN 14214

Bio-heating oil

Techn. glycerol > 96%

15.12 Process flow scheme of a RepCat multi-feedstock biodiesel plant (after ref. [24]).

+ CH3OH

+ KOH

FAME + H2O (biodiesel)

Transesterification: saponification

Direct esterification

Free fatty acid

Potassium fatty acid salt + H2O (soap)

Soap recovery route Amberlyst™ BD20 technology

15.13 Esterification/transesterification of high FFA feedstocks using AmberlystTM BD20 (Rohm & Haas) technology.

which causes difficulties in separation and yield loss. However, FFAs can be converted to methyl esters via esterification (Fig. 15.13). Patent-pending Amberlyst™ BD20 (Rohm & Haas) is a novel polymeric catalyst technology for converting high FFA feedstocks (crude vegetable oils, soapstock, animal fats, recycled oils and greases, fatty acid distillate and recovered soaps) into biodiesel by esterification that runs under mild reaction conditions (T < 373 K, p < 0.7 MPa, MeOH/VO < 25 : 1) in both

734

Biodiesel science and technology

continuous and batch operations. The technology outperforms all standard esterification catalysts (including H2SO4) for FFA > 5% and works well with all feedstock streams (up to 100% FFA). AmberlystTM BD20 is claimed to show the fastest solid-catalyst esterification kinetics. The esterification process can be deployed in a stand-alone mode or followed by a transesterification stage to convert triglycerides. Figure 15.14 shows the application of Amberlyst™ BD20 technology to transesterification of high FFA feeds. The AmberlystTM BD20 catalyst is resistant to triglycerides, glycerol and FFA. Eventually, impurities such as salts, phosphorus compounds and proteins should be removed by a pretreatment process as they can have a negative effect on the downstream transesterification unit, catalyst lifetime, and quality of biodiesel. Figure 15.15 and Table 15.10 illustrate the considerable advantages of the solid-catalyst technology over mineral-acid esterification processes. Using a heterogeneous catalyst the need for downstream processing is reduced. The technology is fully compatible with standard water-wash purification processes or purification with Amberlite™ BD10Dry™ (Rohm & Haas). Amberlyst™ BD20 technology is extremely effective at treating a variety of inexpensive, low-quality, high FFA feedstocks without sacrificing the purity needed in the end product. Feedstocks tested have comprised unrefined Methanol

Pre-treatment (optional)

Vacuum evaporator

AMBERLYST BD20 Stage 2 reactor (optional)

Feedstock: Oil + FFA

AMBERLYST BD20 Stage 1 reactor

Methanol

Distillation

Water

Purification with Amberlite™ BD10Dry™ Pure biodiesel

Transesterification reactor

15.14 AmberlystTM BD20 biodiesel process (after ref. [26]).

Feedstock: Oil + FFA

CH3OH

NaOH

Mineral acid esterification

Neutralisation

CH3OH/H2O

Separation/ filtration

Na2SO4 waste

CH3OH/H2O

Amberlyst BD20 esterification process

Feedstock: Oil + FFA

CH3OH

Amberlyst BD20

Transesterification

15.15 Mineral-acid and AmberlystTM BD20-based esterification processes.

Distillation

Transesterification

Evolution of biodiesel and alternative diesel fuels

Typical mineral acid esterification process

H2SO4

735

736

Biodiesel science and technology

Table 15.10 Disadvantages of using mineral-acid catalysis for high FFA feeds ∑ Need for downstream washing or neutralisation of acid to meet specifications and to protect the transesterification reactor ∑ Significantly lower conversion and slower reaction times than Amberlyst™ BD20 for FFA > 5 wt% ∑ Potential presence of organic sulphur compounds in the biodiesel product ∑ Complex safety, handling and corrosion issues Table 15.11 Advantages of solid-catalyst AmberlystTM BD20 (trans)esterification technology ∑ ∑ ∑ ∑ ∑

Lower feedstock cost Increased process flexibility Increased biodiesel yield Improved biodiesel and glycerol purity Simple and safe process

vegetable oils (RSO, CO, CPO, SBO), fats and greases (chicken fat, beef tallow, inedible oils) and recycled products (yellow grease, trap grease and sewer grease) [26]. The technology converts feedstock with any FFA content to achieve < 0.1% FFA. The process can also be used to boost yield by the recovery of soaps that are generated in the transesterification process, even when a refined vegetable oil feedstock is used. The process economics are very favourable compared to the use of both refined vegetable oil feedstocks and high-fat feeds processed with homogeneous catalysts. Rohm & Haas Amberlyst™ BD20 esterification technology reduces biodiesel production costs [27, 28]. The advantages of the proposed solid-phase transesterification technology are summarised in Table 15.11.

15.3.2 Selective hydrogenation The aim of partial hydrogenation of fatty acid esters is a certain reduction in the amount of polyunsaturates, while generally avoiding formation of saturates or trans products. In particular, selective hydrogenation of vegetable oils may be carried out with the purpose of obtaining low trans isomer formation [29], high conjugated linoleic acid (CLA) formation [30], reduction of undesirable flavour properties (in relation to linolenic constituents) [31, 32], production of biodiesel quality [33, 34], or still otherwise. Partial hydrogenation of trans isomers of fatty acids below 8% is of declared interest to the food industry [30]. However, although trans isomers in certain fatty foodstuffs may increase blood cholesterol levels, no causal relation between high cholesterol levels and heart disease has ever been established [35]. Recently, selective hydrogenation as a value tool for the production of high-quality diesel has become a popular industrial research topic [36].

Evolution of biodiesel and alternative diesel fuels

737

Hydrogenated oils with different physical and chemical properties, whenever needed, are produced by applying various hydrogenation conditions. Reaction conditions (catalyst types and amount, reaction temperature, agitation rate, hydrogen pressure, etc.) greatly affect the mix of fatty acids in hydrogenated vegetable oils [37–39]. One of the most important hydrogenation rate determining factors is the mass transfer of hydrogen gas to liquid oil near the catalyst surface. Industrial hydrogenation reactions are usually carried out in batch reactors [40], and nickel is still the most commonly used catalyst, as in the original invention [41]. Ni catalysts offer high activity, tailored linoleic and linolenic acid selectivity, low cost, and easy removal from oils by filtration. The nickel catalyst isomerises the natural cis double bonds to trans double bonds during hydrogenation. As Ni catalysts are not very active below 393 K, conventional hydrogenation is carried out at higher temperatures (413–503 K), which leads to high trans fatty acid contents in the hydrogenated oils. A low-temperature electrocatalytic hydrogenation, using an electrically conducting catalyst such as Raney nickel or platinum black as electrode, produces hydrogenated edible oils low in trans fatty acids [42–44]. On the basis of the hydrogenation mechanism, catalytic partial hydrogenation of triacylglycerols will invariably generate some trans isomers. If a certain but low trans-isomer content is acceptable (more so for biodiesel applications than for perceived nutritional requirements), operating existing autoclaves at low temperature with an increased amount of standard catalysts [45] will lower the trans-isomer content of the partially hydrogenated product; however, at the same time the content of saturated fatty acids increases. For selective partial hydrogenation leading to a moderate increase in saturated fatty acids and also a low trans-isomer content, various other solutions are open, namely use of: a dilute solution of the oil in a solvent at near- or supercritical conditions [46, 47], zeolites [46–50], precious metal catalysts [51] or copper catalysts [52, 53]. By providing a good homogeneous phase the supercritical fluid state improves hydrogen transfer to the catalyst surface and trans-isomer formation is minimised [54, 55]. In supercritical fluid state hydrogenation over both nickel and precious metal catalysts of all the polyunsaturated fatty acids of RSO to mono-unsaturated fatty acids, no trans fatty acids and no saturated fatty acids were formed [47, 56]. However, the process requires high investment and variable costs. Using structured catalytic packings as support for hydrogenation catalysts takes advantage of the shapeselectivity effect [29, 48, 57]. Selective hydrogenation of trans isomers of fatty acids over Na-ZSM-5 zeolites may eventually reach the commercial stage. Precious metal catalysts are active at the low temperature of 343 K and trans hydrogenated fatty acids are lower, in particular for Pt catalysts [58]. The most active noble metal catalysts (Pd > Rh > Pt >>Ir > Ru >> Os), which are all more active than nickel, are also the most selective ones.

738

Biodiesel science and technology

Copper catalysts are active in hydrogenation reactions of conjugated double bond systems [59] but do not catalyse the saturation of oleic acid to stearic acid [60]. Catalyst performance of copper catalysts has been studied mainly in relation to the high linolenic acid selectivity [52, 53] and thus as a means to increase soybean oil stability. Recent patents [33, 61] reflect renewed interest in the use of copper catalysts. Selective hydrogenation is a valuable tool for feedstock normalisation and may be used profitably for the production of high-quality biodiesel [33, 34]. Reduction of the degree of unsaturation of highly unsaturated fatty substances by catalytic hydrogenation can easily lead to derivatives that are unsuitable to the manufacture of biodiesel, in particular when the treatment leads to production of significant quantities of high melting point saturated fatty acids, which prejudice the cold-weather behaviour of the product obtained. In fact, in order to preserve the fluidity of the oil, it is essential not to increase the melting point, which depends on the content of the saturated component (mainly C16 : 0 and C18 : 0) and the quantity of trans and positional isomers (see Table 14.10), the formation of which is inevitable during the hydrogenation process. Selective hydrogenation of high IV fatty acid alkyl esters for the forced removal of conjugated polyene, triene and diene systems and reduction of the linoleic acid alkyl ester content is meant to lead to formation of monoenes, without in any way achieving complete saturation of the molecule, resulting in an overall decrease of IV to less than the 120 g I2/100 g limit. It is essential to use a hydrogenation catalyst which reduces the degree of unsaturation as much as possible but without increasing the stearic acid content and limiting cis-trans and functional isomerisation. In PCT Int. Publ. No. 2006/111997 A1 to Bondioli et al. [33], biodiesel (liquid at T > 253 K) is produced from fatty substances with high iodine number (typically IV > 152 g I2/100 g) by esterification of fatty acids or transesterification of triglycerides, followed by partial hydrogenation with good selectivity and activity of the FAAEs resulting in a degree of unsaturation of the fuel product of less than or equal to 120 g I2/100 g (see Tables 15.12 and 15.13), as follows: (Trans) (T (Tra rans ns)) esteri esterification este rifi fication cation Selective Selective TGs, FFAs æ æææ ææ Æ FAAEs æ æææ Æ Biodiesel hydr hydrogenation ogenation

(IV > 150 g I2/100 g)

15.1

(IV ≤ 120 g I2/100 g)

Catalytic hydrogenation is preferably carried out with a hydrogen pressure of about 0.1–0.6 MPa at 433–453 K for 1–3 h. During the process all the water formed must be removed under vacuum. In case tall oil is used as the starting vegetable oil in the above described process, an additional intermediate step involves separation of FAAEs from the non-esterified resin acids (see

Evolution of biodiesel and alternative diesel fuels

739

Table 15.12 Selective catalytic hydrogenation of fatty acid methyl esters (after ref. [33]) Feedstock compositionb ————————————————————— C18:3 C18:2 C18:2cc C18:1 C18:0

IVd



Hydrogenation conditionsa Catalyst t

Tall oil Linseed oil

– a – a

– – 52.0 2.0

145 112 168 111

Oil



– 80 – 860

42.6 15.9 14.0 38.0

9.5 1.0 – –

34.9 64.2 22.0 47.0

0.4 1.3 4.0 5.0

a

Cu/SiO2 catalyst at 453 K and 0.6 MPa; t, hydrogenation time (min). Composition in mol%. c Conjugated dienes. d g I2/hg. b

Table 15.13 Selective catalytic hydrogenation of high unsaturated fatty acid methyl esters (after ref. [34]) Oil





Hydrogenation Feedstock compositionb CNc IVd conditionsa ————————————————— Catalyst t C18:3 C18:2 C18:1 C18:0 C16:0

Sacha inchi oil – a Hempseed oil – a Tobaccoseed oil – a Grapeseed oil – a

– 30 – 100 – 120 – 60

50.4 – 17.3 – – – – –

33.9 36.1 57.0 40.0 79.2 33.0 72.5 39.0

9.3 57.7 13.2 50.0 11.6 57.0 16.7 50.0

2.7 3.0 2.8 2.9 2.4 3.0 3.9 3.6

3.7 3.8 6.4 6.3 6.7 6.5 6.9 6.9

35 52 43 51 46 52 48 52

202 115 164 118 145 111 142 108

PPe

248 260 253 260 256 263 255 261

a

Cu/SiO2 catalyst at 433 K and 0.4 MPa; t, hydrogenation time (min). Composition in mol%. c Calculated. d g I2/hg. e Kelvin. b

Fig. 9.5). It is essential to reduce the resin acid content, which results in increased Conradson carbon residue. Selective hydrogenation of non-edible oils such as fish oils, linseed oil, castor oil and tall oil fatty acids or animal fat, might make available important quantities of feedstock for biodiesel production. Feedstocks which have been modified successfully by the aforementioned procedure are tall oil (IV = 170 g I2/100 g), vegetable oils (e.g. linseed oil, IV = 184; burdock oil, IV = 153; hemp oil, IV = 160; walnut oil, IV = 145; poppy oil, IV = 140; perilla seed oil, IV = 204; camelina seed oil, IV = 135; and tung oil, IV = 168 g I2/100 g) and fish waste oils (e.g. shad oil, IV = 175; cod liver oil, IV = 160; herring oil, IV = 140; salmon oil, IV = 161; and sardine oil, IV = 185

740

Biodiesel science and technology

g I2/100 g). These feedstocks are generally unsuitable for the preparation of biodiesel meeting international reference standards. For example, linseed oil is characterised by a high C18:3 content, and fish oils by high polyene content (C18:4, C20:4, C20:5, C22:5, C22:6, etc.; see Section 5.6). Selective hydrogenation may also profitably be considered for biodiesel from algae. Heterogeneous hydrogenation of vegetable oils has been reviewed frequently [30, 39, 62–64]. Partially hydrogenated SBO methyl esters (PHSME, IV = 116 g I2/hg) have superior oxidative stability, but inferior low-temperature performance, kinematic viscosity, and lubricity in comparison to soybean oil methyl esters (SBME, IV = 120 g I2/hg). The production of PHSME from refined SBO (not qualifying as a potential feedstock according to EN 14214) increases biodiesel production costs by US$0.04/L [65]. Mutation breeding and gene-technological improvements of plants with maximum potential for desirable oil qualities would eliminate the need for selective catalytic hydrogenation of unsaturated oils and thus avoid contamination by isomerised cis- and trans-fatty acids.

15.3.3 Microbial FAEE biosynthesis for microdiesel production A broader use of biodiesel will be possible if production processes are developed that are not based solely on oilseeds but on cheap and readily available renewable bulk plant materials like sugars, starch, cellulose or hemicellulose (see Table 15.4). Expression of wax ester synthase/acyl-coenzyme A: diacylglycerol acyltransferase (WS/DGAT) in different recombinant hosts has been exploited to synthesise various fatty acid esters in vivo. Examples of these recombinantly synthesised fatty acid esters are fatty acid butyl esters (FABEs) in recombinant Escherichia coli [66], and triacylglycerols (TAGs), fatty acid ethyl esters (FAEEs) and fatty acid isoamyl esters (FAIEs) in recombinant Saccharomyces cerevisiae [67]. Although only trace amounts were produced, recombinant biosynthesis of FAEEs and FAIEs in yeasts as well as FABEs in E. coli indicate that production of biodiesel-appropriate fatty acid monoalkyl esters is in principle feasible by using recombinant WS/DGAT-expressing microorganisms. Recently, Kalscheuer et al. [68] have developed a microbial process for the production of biodiesel-adequate FAEEs, referred to as Microdiesel, from simple and renewable carbon sources. This was achieved by heterologous expression in E. coli of the Zymomonas mobilis pyruvate decarboxylase and alcohol dehydrogenase and the unspecific acyltransferase with the WS/DGAT gene from Acinetobacter baylyi strain ADP1. By this approach efficient ethanol biosynthesis was combined with subsequent esterification of the ethanol with the acyl moieties of coenzyme A thioesters of fatty acids if the cells are cultivated under

Evolution of biodiesel and alternative diesel fuels

741

aerobic conditions in the presence of glucose and oleic acid (Fig. 15.16). Ethyl oleate was obtained as the major constituent of the FAEEs with minor amounts of ethyl palmitate and palmitoleate. Although the yields obtained (26% of the cellular dry mass) in this novel process are still far below the needs of an industrial process, at least the feasibility of the production of biodiesel equivalents from renewable resources by employing engineered microorganisms has been indicated. Substantial FAEE biosynthesis was strictly dependent on supplementation of exogenous fatty acids. This indicates that de novo fatty acid biosynthesis, in contrast to fatty acid b-oxidation, cannot provide sufficient intracellular acyl substrates for WS/DGAT-mediated FAEE synthesis. E. coli is not ideal for Microdiesel production. Optimised Microdiesel production by engineered microorganisms could offer some major advantages over established conventional production processes. Biotechnological Microdiesel production could be significantly less expensive than conventional biodiesel production if plant products like starch or lignocellulose are used for its production. These plant polymers are much cheaper than plant oils, and also much more abundant. Microdiesel production will then no longer be restricted to oilseed producing regions of the world, in contrast to conventional FAME-based biodiesel. At the present Glucose

Oleic acid

Glycolysis O

OH Fatty acid b-oxidation

O Pdc O AdhB

O OH

S

WS/DGAT

CoA

O O

15.16 Pathway of FAEE biosynthesis in E. coli. FAEE formation was achieved by co-expression of the ethanolic enzymes pyruvate decarboxylase (Pdc) and alcohol dehydrogenase (AdhB) from Z. mobilis and the unspecific acyltransferase WS/DGAT from A. baylyi strain ADP1 (after ref. [68]).

742

Biodiesel science and technology

time, use of bioethanol for production of FAEE-based biodiesel would result in a fully sustainable fuel, but only at the expense of very high production costs (see Section 7.2.2). Microdiesel is a fully sustainable biofuel completely derived from renewable materials, avoiding the use of highly toxic methanol (green product, green process) or biomethanol. Technical advantages of FAEE-based biodiesel include lower cloud and pour points than methyl esters, favouring cold starts, and higher heat content and cetane number. A Spanish start-up (Ecofa SA) has developed a biochemical process to turn urban solid organic waste into a fatty acid biodiesel feedstock [69]. In a different development, biopolyesters (based on w-hydroxy fatty acids derived from SBO) at the end of their life cycle may be transformed into biodiesel by liquid suspension in the presence of the enzyme cutinase (see Section 10.3).

15.4

Hydroprocessing technology

As already indicated in Section 1.3, transesterification is not the only process used to produce a biofuel from triglyceride feedstocks (vegetable oils, treeborne oils and animal fats). A competing approach involves hydroprocessing, which is a generic term encompassing a number of catalytic processes using hydrogen, e.g. hydrogenation, hydrocracking and hydrotreating (Fig. 15.17). Hydroprocessing of natural lipids occurs in stages, from saturation of double bonds, stripping off the triglycerides attached to the fatty acid chains and removal of all other oxygen-containing compounds, to cracking with formation of a diesel fuel. Careful selection of the hydrogenation catalyst can result in a diesel fuel directly without the need for a separate hydrocracking step. During the last century the chemical industry has turned hydrocarbons into a variety of functionalised chemicals, mainly by catalytic oxidation (see Fig. 15.1). Preparation of under-functionalised renewable diesel fuels, essentially alkanes, from overfunctionalised vegetable oils by catalytic hydroprocessing Feedstock

Process

Product(s)

Methanol Transesterification

Biodiesel

Vegetable oil Glycerol

H2 Hydroprocessing

Hydrodiesel

Vegetable oil

15.17 Transformation processes of natural lipids.

Evolution of biodiesel and alternative diesel fuels

743

is essentially the opposite and chemically less appropriate. Yet, marrying refining and renewable fuels provides a potentially lucrative opportunity to create ‘green’ fuel with attractive refining economics. Developing petroleum-like fuels from renewable sources is an ingenious idea. An early process for simultaneous hydrogenation and cracking of vegetable and tree oils was developed at the Saskatchewan Research Council (SRC). The technology has been licensed to Arbokem, Vancouver (BC). One of the feedstocks successfully used in the development of a biofuel called ‘SuperCetane’ is tall oil, a by-product from the Kraft pulping process from pine and Douglas fir. From an economic perspective the total cost of SuperCetane would range between 18 and 32 cents per litre (1998), as compared to 66 cents using vegetable oils [70]. Expired Canadian patents from the 1980s using tall oil, never commercialised, have indicated that hydrogenation of natural oils can result in very high cetane number diesel fuel of very high purity (e.g. zero sulphur and aromatics). US Patents No. 4,992,605 to Craig and Soveran [71] and No. 5,705,722 to Monnier et al. [72] disclose production of high cetane number additives for diesel fuels (mainly C15 to C18 paraffins) by hydroprocessing of biomass feedstock, selected from canola oil (CO), sunflower oil (SNO), rapeseed oil (RSO), palm oil (PMO) and fatty acid fractions of crude tall oil, at 623–723 K and at 4.8–15.2 MPa. Recent renewed interest in vegetable oil hydroprocessing technology by the oil industry has probably been triggered by tax and other ‘breaks’ made available to the biofuels industry, as well as by the lack of sufficient product quality control by (part of) the biodiesel industry (see Section 12.4), especially with respect to oxidative stability in summer and cold-flow properties in winter. The oil industry, which supplies the dominant ultra-low sulphur diesel (ULSD) component of biodiesel blends, is in a position to supply a renewable diesel itself and probably with better product quality control than many small biodiesel producers. Almost any petroleum refiner that produces low-sulphur diesel fuel or gasoline has sufficient surplus hydrogen available to manufacture a hydrodiesel. The biodiesel industry thus faces a new challenge in the growing interest by the oil industry in producing a consistent and reliable diesel fuel by hydrogenating the same natural feedstocks (vegetable oils and the like) to make a product variously called renewable synthetic diesel, green diesel, hydrodiesel, hydrotreated vegetable oil (HVO), hydrogenation-derived renewable diesel (HDRD), or bio-hydrogenated diesel (BHD). Petrodiesellike fuels from agricultural lipids have sometimes also been referred to as ‘synthetic biodiesel’ or ‘second-generation biodiesel’ but these terms are misnomers as they do not meet the definition of biodiesel, which is, according to ASTM D 6751: ‘mono-alkyl esters of long-chain fatty acids derived from vegetable oils or animal fats’.

744

Biodiesel science and technology

The projected manufacturing capacity of this new renewable diesel alternative (670 kt in 2006) is sizeable in biodiesel industry terms but is a very small product volume for any major oil refiner. However, if the petroleum industry seriously moves into hydrotreating of natural lipids, it is likely that the supply side (vegetable oil feedstock) will even more rapidly become the primary growth-limiting factor for both biodiesel and hydrodiesel. At the same time, it is equally likely that neither biodiesel produced by methanolysis of natural lipids nor hydrodiesel can shortly become mainstream energy sources, but they will be very attractive additives for ULSD fuel because of their important contributions to lubricity, engine performance and combustion emissions control. Since HVOs are hydrocarbons, they largely meet conventional diesel fuel requirements (EN 590, ASTM D 975, Worldwide Fuel Charter Category 4), but not ester specifications (EN 14214, ASTM D 6751). Hydrotreated fuels present both advantages and disadvantages with respect to biodiesel, which are mainly on account of differences in chemical nature, namely saturated hydrocarbons vs. partially unsaturated fatty acid alkyl esters, respectively (Table 15.14). While vegetable oils with low saturation level are preferred for biodiesel applications, higher saturation in the oils is preferred for hydrodiesel in view of lower hydroprocessing costs. On the whole, renewable feedstock costs are comparable. Hydroprocessing of low-quality feedstocks (high FFA content) gives no problems. The synthetic diesel fuels resulting from natural lipid hydrotreatment have very attractive properties, including a high cetane number (no need for additives to meet fuel specifications), very low NOx emissions, and zero aldehyde emissions (a problem with biodiesel). The heating value is about 11% higher. As hydrodiesel is a fuel very similar to traditional petrodiesel, existing engines can be used without modifications. Table 15.14 Characteristics of hydroprocessed bio-based alkane fuels Advantages over biodiesel: ∑ Flexible cold-flow properties and better oxidative/storage stability (more fossil diesel-like) ∑ More combustible energy content per unit mass (11%) ∑ High cetane number ratings ∑ Lower NOx exhaust emissions ∑ Fewer obstacles in gaining acceptance by engine manufacturers ∑ Co-production of propane, naphtha and jet fuel ∑ No low-value liquid by-product (waste water, soaps) ∑ Require no special tank storage ∑ Can be sent by pipeline to blending sites or retail distribution centres Disadvantages over biodiesel: ∑ Less environmentally friendly in terms of CO and soot ∑ Poor fuel lubricity ∑ Slower biodegradability ∑ Poor safe handling properties (flammability, toxicity)

Evolution of biodiesel and alternative diesel fuels

745

The low lubricity is easily (and inexpensively) corrected by means of lubricity additives. Hydrodiesel avoids the glycerol glut problem. However, many of the typical biodiesel advantages are lost when using vegetable oilbased alkane fuels. Among these are excellent fuel lubricity characteristics, safer handling properties due to being non-flammable, non-toxicity, much faster biodegradabilities and reduced exhaust emissions, including CO and particulate matter. By transforming vegetable oils into hydrocarbons all benefits linked to the biodegradability of the product are lost. The energy balance of hydrodiesel from biological sources is less favourable than that of biodiesel since its production requires higher T, p, higher investment and operating costs. Moreover, conversion of the feedstock is lower (<90%) as compared to biodiesel (98%). Consequently, the use of agricultural lipids for this purpose could be a waste of these feedstocks. Table 15.15 summarises the main features of hydroprocessing biodiesel/diesel substitute production methods. High investments are required for high-pressure hydrogenation units (7100 million per unit). Hydroprocessing is a preferred refinery operation. Two alternative vegetable oil hydroprocessing routes can be considered, namely co-processing in an existing distillate hydroprocessing unit, or a stand-alone unit (Fig. 15.18). Problems connected with co-processing of vegetable oils are several: ∑ reduction of HDS catalyst activity (due to oxygen); ∑ high exothermicity of hydrotreatment of vegetable oils; ∑ co-production of CO, CO2 and H2O (impacting on H2 recycling); and ∑ need for a pre-treatment reactor (removal of Na, Ca, P and other metallic contaminants). Co-processing tends to produce paraffinic diesel with a high cloud point and is of variable quality. This is because traditional refineries are not built to handle Table 15.15 Hydroprocessing biodiesel/diesel substitute production methods Advantages: ∑ Proven technology ∑ Allows processing of non-refined oils (TGs, FFAs) ∑ Feedstock flexibility ∑ No glycerol marketing problems Disadvantages: ∑ High investment and production costs ∑ High T, moderate to high p ∑ Pre-treatment/post-treatment (isomerisation) ∑ Low reaction yield ∑ Eliminates beneficial properties (see Table 15.14) ∑ Catalyst coking, poisoning, regeneration ∑ By-products

746

Biodiesel science and technology H2

Pre-treat and co-process Diesel H2 Vegetable oil

DHT

Hydrodiesel

Remove contaminants

Pre-treater

H2 Stand-alone unit

Vegetable oil

H2

Diesel

DHT

Hydrodiesel

Hydrodiesel unit

15.18 Alternative vegetable-oil hydroprocessing routes to transportation fuels. Key: DHT = diesel hydotreater.

CO2 and oxygenated feedstock, intrinsically associated with hydrotreatment. Therefore, it is better to have a dedicated facility for making green diesel. A renewable diesel unit is a separate unit integrated with an oil refinery, which uses existing logistics, energy, hydrogen, quality control laboratory and other facilities. A separate unit avoids diesel hydrotreater (DHT) catalyst life issues and increases flexibility. In a stand-alone unit there is no co-feed of the bio-component with crude oil. A stand-alone unit needs access to a hydrogen supply or a dedicated hydrogen plant. Hydrogen required for HVO production can come from a variety of sources, including a conventional H2 plant, a typical naphtha-to-gasoline PlatformingTM unit, or steam reforming of the light fuel by-products of the HVO process; the latter option decreases the overall fossil fuel consumption. From a petroleum refiner’s perspective, a fully deoxygenated renewable diesel is considered a premium diesel blending component. The boiling range is comparable to typical diesel products, with substantially higher cetane and lower density. These are very valuable properties that enable refiners to optimise the amount of lower value refinery streams that can be blended into the refinery diesel pool while still meeting all of the required EU diesel specifications. Furthermore, cold-flow properties can be regulated by adjusting process conditions, thus making the process more flexible than biodiesel with respect to feedstock selection and plant location. In contrast to FAMEs, where fuel properties depend on feed origin and process configuration, paraffinic diesel products (NExBTL, Green Diesel, etc.) are independent of feed origin. A recent Canadian operability test of low-level

Evolution of biodiesel and alternative diesel fuels

747

blends, namely B2 (CME; HDRD) in winter (T > 233 K) and B5 (CME/ TME = 3/1; HDRD) in summer was successful [73]. Life cycle GHG emissions of renewable diesel are 40–60% lower than for those of fossil diesel fuel. Yet, the total GHG values are comparable to FAME, since farming and feedstock production, including the use of fertilisers, limestone and other materials, are major contributors to GHG emissions. The renewable diesel process itself, including hydrogen production, makes only a minor contribution to GHG emissions. Life cycle analyses of hydrodiesel and biodiesel need further comparison, in particular in terms of energy efficiency and the effects of the hydrogen production process. The social impact of the geographically dispersed biodiesel production and of centralised bio-based alkane fuels production will be quite different, with potential benefits of energy crops for rural and urban communities versus large petroleum companies. Several petroleum companies are now operating small incremental hydrogenation facilities at their refineries to produce hydrodiesel in dedicated or co-processing mode (Table 15.16). EU hydrodiesel capacity is under development in Finland, Ireland, Italy, Portugal, The Netherlands and Austria. Dedicated NExBTL and EcofiningTM facilities are located inside existing refineries. ConocoPhillips is focusing its resources on conversion technologies that will enable large-scale biofuel production. Current technologies seem likely to fail if their scale is expanded too greatly. Although ConocoPhillips buys biodiesel for its terminals as part of normal commercial activities, its technology development is entirely on second- and third-generation fuels, primarily through thermochemical pathways. The focus of the research is finding ways of making processes sustainable while reducing CO2 emissions and using cost-effective feedstocks. Target products are hydrocarbon fuels that will fit within the existing distribution system (pipelines and terminals) Table 15.16 Vegetable oil hydrogenation facilities Stakeholder

Technology

Feedstock

SRC/Arbokem Dedicated Tall oil Neste Oil Dedicated (NExBTL) PMO, RSO, TLW UOP LLC/Eni Dedicated (EcofiningTM) SBO, PMO, RSO Petrobras Co-processing (H-BIO) SBO, CAS ConocoPhillipsa Co-processing SBO Tyson Renewable Co-processing TLW   Energyb BP Co-processing TLW Cetane Energy Proprietory Undisclosed a

Product SuperCetane Renewable Synthetic Diesel Green Diesel Renewable diesel Hydrocarbon fuel Renewable diesel Renewable diesel Renewable diesel

Whitehead refinery (County Cork, Ireland). Full-scale commercial operations (175 MMgy) as from spring 2009.

b

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Biodiesel science and technology

and vehicles without retrofit. Infrastructure is considered as the key element in successfully implementing large-scale sustainable biofuels. ConocoPhillips has technologies that convert triglycerides into fuels and currently uses this technology position to make renewable diesel commercially for soybean oil and tallow. Activities comprise co-processing of SBO (Whitegate refinery, County Cork, Ireland; 50 kt/yr as from December 2006) and of TLW (Tyson Renewable Energy joint venture; 175 MMgy as from 2009). ConocoPhillips is also committed to renewable fuel from algae. Similarly, Petrobras (Brazil) has developed its proprietary H-BIO co-processing technology (see Section 15.4.3). In Australia, BP intends producing 110 kt/yr biofuel from animal fat at its Bulwer Island (Queensland) refinery by 2008 using proprietary coprocessing technology that uses hydrogen to convert heated tallow (at least 50% of the feedstock). PTT/Toyota Thailand is developing bio-hydrogenated diesel (BHD). Hydrodiesel is very similar to synthetic diesel obtained (at much higher cost) by converting carbonaceous feedstocks into syngas and finally into a hydrocarbon product using Fischer–Tropsch technology (see Section 15.5). Future processes (BTL technologies), which enable utilisation of residual biomass (cheaper feedstock) instead of lipids (expensive foodstock) to produce liquid hydrocarbons, are of great interest. Cetane Energy LLC (Carlsbad, NM) has recently developed small-scale (3 MMgy) hydroprocessing technology.

15.4.1 NExBTL Renewable Synthetic Diesel To be able to blend a year-round renewable fuel for the diesel pool requires an improved synthetic diesel over FAME. Neste Oil Corporation has proposed a different renewable diesel and has developed the corresponding biofuel technology, called Next generation Biomass To Liquid diesel technology. The novel NExBTL diesel component (GTL-like) utilises a proprietary conversion process for vegetable oils and animal fats [15, 74, 75]. NExBTL Renewable Synthetic Diesel is a biofuel of superior quality. The feedstock for the traditional biodiesel esters and Neste Oil’s NExBTL product is the same, namely natural organic esters contained in vegetable oils and animal fats. The difference is in the processing and chemical nature of the end products. Whereas FAMEs are chemically methyl esters of long-chain fatty acids carrying oxygen in their ester group, NExBTL is a hydrocarbon diesel (linear and/or branched C10-C22 alkanes) containing no oxygen (see Fig. 15.19). Vegetable oils and animal fats may be processed to decompose the ester and/or fatty acid structure and to saturate the double bonds of the hydrocarbon chains, thus yielding about 80–85% of n-paraffin product relative to the mass of the starting material. This product, admixed with a diesel fuel, shows poor

Evolution of biodiesel and alternative diesel fuels R¢—CH2CH3 + 2H2O

RCOOCH2 RCOOCH RCOOCH2 Triglyceride, R = nC

749

H2 Catalyst

R¢—CH3 + CO2 R¢—CH3 + CO + H2O NExBTL biodiesel, R¢ = (n–1)C CH3CH2CH3 Propane (fuel gas)

15.19 Simplified NExBTL process chemistry. Oils/fats Acid Caustic Water

Pre-treatment (optional)

Solids Water

Triglycerides Water Hydrogen

NExBTL unit

Bio fuel gas Biogasoline

NExBTL diesel ULSD pool

15.20 Simplified Neste Oil’s NExBTL process scheme.

performance at low temperatures. In addition, n-paraffins having a carbon number of fatty acids are waxy with a high solidification point, typically above 283 K, thus limiting the use of these compounds in diesel fuels at least at low temperatures. PCT Int. Publ. No. WO 2004/022674 A1 to Jakkula et al. (to Fortum Oyj) [76] discloses a diesel fuel composition obtained by hydrotreating of vegetable oils, animal fats and/or fish oil, and optionally by isomerising the hydrocarbon, typically waxy n-paraffins, to give branched hydrocarbon chains, thus improving the low-temperature properties of the paraffin. In the NExBTL Renewable Synthetic Diesel process technology, the fatty acid feedstock is ‘hydrotreated’, that is, it is reacted with hydrogen (produced at a refinery), as shown in Fig. 15.20. Side products include propane and gasoline-premium fuels which are also produced from the renewable, biological feedstock. While NExBTL technology is not afflicted by the glycerol by-product problem, the process produces considerable amounts of

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Biodiesel science and technology

CO and CO2 (see Fig. 15.19). The NExBTL process generates only products for the fuel market, shows good energy efficiency and is fully integrated with a refinery. The NExBTL process allows conversion of vegetable oils to GTL-like biodiesel by: ∑ ∑ ∑

mild pre-treatment for removal of insaturations; hydrogenolysis of the fatty acid ester bond with production of paraffins and formation of CO2 and H2O; and hydro-isomerisation of linear paraffins for improvement of cold properties without loss of cetane number.

Table 15.17 compares NExBTL synthetic diesel and FAME manufacturing. NExBTL is made from renewable biomass sources, namely fatty acids from vegetable oils and animal fats. With only 2–3 wt% addition of hydrogen, NExBTL is 97–98% renewable (‘green’ product). NExBTL contains no sulphur, oxygen, nitrogen or aromatics and has a very high cetane number compared to FAME-based compositions (see Table 15.18). Renewable diesel satisfies ASTM D 975 diesel standards either as a neat component or when blended with other typical diesel-fuel components. The absence of sulphur, aromatics and oxygenates allows NExBTL to be used in the world’s most stringent diesel fuel formulations like California’s CARB diesel, Swedish MK1 diesel and the ultra-clean burning World Wide Fuel Charter (WWFC) Category 4 diesel. The high cetane value of between 84 and 99 means that NExBTL can be used to improve the quality of conventional diesel or to upgrade off-spec diesel fuel. Advantages of this diesel fuel composition are superior performance at low temperature. Cold properties are flexible by modulation of the hydroTable 15.17 Comparison between NExBTL synthetic diesel and FAME manufacturing (after ref. [77]) Feature

NExBTL diesel

FAME

Raw material Flexibility in use of several More restricted to specific   origin   vegetable oils and animal fats   feedstock Additional feeds Hydrogen Methanol Product quality Excellent blending properties; Limitations with blending,   no real restriction   stability and cold   properties By-products Handled in refinery Glycerol NOx emission Reduced Increased CO2 balancea 0.5–1.5 1.4–2.0 Logistics Refinery logistics Separate logistics Plant size Large units integrated with oil Small to large independent   refinery   units a

kg CO2/kgoe fuel.

Evolution of biodiesel and alternative diesel fuels

751

Table 15.18 Characteristics of Neste Oil’s NExBTL Renewable Synthetic Diesel ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Very high cetane value (84–99) Flexible cold properties (CP as low as 239 K) Excellent storage stability No sulphur, no aromatics, well-balanced distillation curve Less emissions than ultra-low sulphur diesel fuel Renewable content exceeding 97% (‘green’ product) Exploits existing fuel infrastructure Superior fuel properties that can be used to upgrade the diesel pool Blending with diesel in high ratios (up to 60%) Rather low density No need for engine modifications Registered product (conforms with European norm 2003/30/EC)

isomerising capacity of the process. Cloud point of NExBTL can be adjusted in production from 268 K to 239 K to meet the needs of various climatic conditions. Heating value is similar to the EN 590 hydrocarbon fuel. NExBTL is a stable hydrocarbon without unsaturated components and can be stored for extended periods. The hydrocarbon molecular structure makes solubility of the synthetic diesel product into water very low. NExBTL synthetic diesel is compatible with the existing vehicle fleet as well as with the diesel fuel logistic system and is technically easy to blend in petrodiesels in all ratios. NExBTL in diesel blends decreases both regulated and unregulated (e.g. aldehydes) exhaust emission components. Decrease in emissions is dependent on the proportion of NExBTL. When compared with emissions from the ‘clean’ European sulphur-free EN 590 diesel, NExBTL Renewable Synthetic Diesel shows positive environmental benefits with considerable reductions in tailpipe emissions: life cycle GHG, >60%; NOx, 7–14%; PM, 28–46%; HC, >20%; and CO, >5%. An assessment of energy and GHG of NExBTL from rapeseed oil and palm oil is available [78]. The non-oxygenated NExBTL synthetic, produced in a conventional hydrogenation process using vegetable oils and animal fats as a raw material, has similar chemistry and fuel properties as the present GTL and BTL diesel fuels, but higher raw material costs (closer to conventional biodiesel). NExBTL and most GTL-type hydrocarbon fuels have different chemistry compared to conventional biodiesels (FAMEs). Table 15.19 compares the properties of the isomerised biological NExBTL component, GTL diesel, RME and a commercial diesel fuel. Properties of the high-quality NExBTL synthetic diesel, which is basically a mixture of n- and iso-paraffins, are comparable to the best existing premium hydrocarbon diesels available today, such as GTL distillate fuels. In theory, NExBTL can be used neat. NExBTL biofuel meets the requirements of both the European diesel fuel standard EN 590 and the automotive and engine manufacturers WWFC Category 4

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Biodiesel science and technology

Table 15.19 Comparison of some key fuel properties of diesel fuels (after refs [15, 74, 79]) Fuel property

NExBTL biofuel GTL diesel FAME (RME) EN 590/2005

Density @ 288 K (kg/m3) Viscosity @ 313 K (mm2/s) Cetane number Distillation 10 vol% (K) Distillation 90 vol% (K) Cloud point (K) Energy density (MJ/kg) Energy content (MJ/L) Total aromatics (wt%) Polyaromatics (wt%) Oxygen content (wt%) Sulphur content (ppm) Lubricity Oxidative stability

775–785 2.9–3.5 84–99a 533–543 568–573 268–239 ~ 44 ~ 34 0 0 0 ~ 0 < 460b Good

770–785 3.2–4.5 73–81 ~ 531 598–603 273–248 ~ 43 ~ 34 0 0 0 < 10 < 460b Good

~ 885 ~ 4.5 ~ 51 ~ 613 ~ 608 ~ 268 ~ 38 ~ 34 0 0 ~ 11 < 1 < 460 Challengingc

820–845 ~ 3.5 ~ 53 ~ 473 ~ 623 273–258 ~ 43 ~ 36 ~ 25 ~4 0 < 10 < 460b Good

a

Measured as blending cetane number. Lubricity additive required. c Additive requirement. b

fuel specification, except for density, which is ~ 780 kg/m3 (EN 590: 835 kg/m3). The density value is the only blending constraint limiting blending of the synthetic diesel product to about 65 vol%, which of course is not a real restriction in refinery operations. NExBTL technology proves that no compromise is necessary with renewable fuel products and product quality for transportation fuels. Although biomass-based renewable fuels are usually produced outside of refineries, the NExBTL technology shows profitable opportunities to incorporate biomass-based materials into the refining industry [77]. In fact, there exists a clear commercial driver to integrate synthetic diesel production within a refinery and use the existing utility and quality systems as well as diesel oil logistics systems. The first 170 kt/yr NExBTL production plant at Porvoo refinery in Finland, which started operating in the first half of 2007, runs on a mixture of PMO (80%), RSO and animal fat and is producing a product that meets ASTM D 975 standards with a 253 K cloud point. A second, similar plant, again in Porvoo, is scheduled for 2009. Albemarle Corp. supplies the catalysts for Neste Oil’s renewable diesel. Neste Oil has recently started construction of the world’s largest (800 000 MT/yr, 271 MMgy) renewable diesel production facility in Tuas, Singapore (scheduled late 2010; 7550 million), based on NExBTL technology, using primarily RSPO certified palm oil from Malaysia and Indonesia (when available in sufficient volumes) and animal fats. Similary, in May 2009 Neste Oil also broke ground for a 7670 million, 800 kt/yr capacity hydrodiesel plant in Rotterdam, The Netherlands, to be run on a

Evolution of biodiesel and alternative diesel fuels

753

variety of feedstocks. Investment costs per installed gallon (72.85) are higher than for biodiesel plants. On the other hand, hydrogen production requires far less energy than methanol. Another NExBTL unit (200 kt/yr) is expected in Austria. Also a large-scale NExBTL plant adjacent to one of Total’s oil refineries has been designed for a wide range of VOs and animal greases. The technology could also find application for the conversion of algal oil [80] and jatropha oil (both not yet available in commercial quantities), although saturated oils are better feedstocks in terms of hydrogen consumption. The NExBTL Renewable Diesel process was honoured with the Cleantech Finland award (Sitra Innovation Fund).

15.4.2 Ecofiningtm hydroprocessing technology Ecofining™ from UOP LLC/Eni is another feedstock-flexible catalytic hydroprocessing technology that converts a wide range of vegetable oils and other biologically-derived feedstocks (waste) into a Green Diesel fuel with high cetane values (80–90 range), good cold-flow properties and low emissions [81–83]. The Green Diesel process is a two-stage process: (i) hydrodeoxygenation (HDO) of vegetable oils (using a UOP (Ni, Mo) catalyst); and (ii) isomerisation of n-paraffins (using an Eni PMG catalyst). Figure 15.21 shows a simplified process flow diagram. Feedstock is routed to the catalytic reactor where it is combined with hydrogen, brought to reaction Vegetable oil

Make-up hydrogen

Recycle H2 purification

Reactor

CO2

Propane and light ends

Separator

Water

Naphtha or jet fuel

Diesel

15.21 Simplified EcofiningTM Green Diesel process flow diagram.

754

Biodiesel science and technology

temperature, and then converted by a series of optimised hydrodeoxygenation, decarboxylation and hydroisomerisation reactions to a branched paraffin-rich diesel fuel. Water and COx formed by deoxygenation according to catalyst Triglycerides + H2 æ æÆ paraffins + H2O + COx

15.2

are separated from the fully deoxygenated liquid hydrocarbon product, which is then fractionated to remove a small amount of light-fuel by-product. Excess hydrogen provided to the reactor is recovered and recycled to the reactor to maintain a minimum required hydrogen partial pressure. Makeup hydrogen is added to the process to balance both chemical consumption and solution losses. Process hydrogen requirements and product yields are shown in Table 15.20. The primary product is paraffinic diesel and coproducts include propane and naphtha. Product carbon number distribution and selectivity of oxygenate conversion to H2O and COx is controlled by the choice of catalyst and reaction conditions. Diesel yield depends on both feedstock type and operating severity and varies from 88 to about 99 vol% depending on the level of hydroisomerisation required to achieve product cloud point specification. A range of vegetable oil feedstocks has been processed in pilot plants, including SBO, RSO and PMO, while other potential feedstocks such as tallow and greases are under evaluation. Palm oil requires substantially less hydrogen than rapeseed or soybean oil due to the lower olefin content. Pilot-plant tests have shown that there is no measurable catalyst deactivation after over 2000 h on-stream. Table 15.20 shows some performance parameters of the Green Diesel Table 15.20 Performance parameters of Green Diesel process (after ref. [83]) Feedstock: ∑ Vegetable oil ∑ Hydrogen

100 wt% 1.5–3.8 wt%

Products: ∑ Naphtha/kerosene ∑ Propane ∑ Green diesel

1–10 vol% 8–9 vol% 88–98+ vol%

Product properties: ∑ Density @ 288 K ∑ Oxygen content ∑ Cetane number ∑ Cloud point ∑ Distillation ∑ Lower heating value ∑ Sulphur ∑ Stability

780 kg/m3 0% 70–90 263–293 K 538–593 K 44 MJ/kg < 1 ppm Good

Evolution of biodiesel and alternative diesel fuels

755

process. Green Diesel has excellent fuel properties, and is very similar to diesel produced via Fischer–Tropsch processes. On the basis of an LCA study [83] the product is superior to both petrodiesel and biodiesel and an excellent blending component. Green Diesel has a lower environmental impact and lower climate active CO2 production than FAME. The eco-compatibility in terms of kg active CO2/kg fuel is more favourable for Green Diesel (0.9 kg/ kg) than for biodiesel (1.6–2.3 kg/kg) or petrodiesel (3.8 kg/kg) (see also Fig. 14.8). The environmental impact of FAME production is higher due to the methanol feedstock requirement. Methanol is produced from natural gas through a very energy intensive process with high environmental burdens. Fossil energy consumption in the Ecofining™ process is reduced by 84–90% for green diesel produced from SBO or PMO, respectively, when H2 is produced internally from the light-fuel by-products rather than from fossil resources. Green Diesel thus has the potential to displace more petroleum resources per energy content in the fuel compared to biodiesel. As in all refinery processes, the primary factor in the Green Diesel process economics is the feedstock costs. The process is economically competitive and sustainable. Process economics is assured for palm and soy oil (at US$420/ MT and US$560/MT, respectively; May 2007) for crude oil prices of US$52 and US$67/bbl, respectively. With the provision of a US$1/gal subsidy for renewable diesel produced in the US, a new unit processing soybean oil can be paid back in 1 year at a crude oil price of US$39/bbl. UOP LLC’s Ecofining™ process has been licensed to Eni SpA, Livorno (Italy), Ecofining’s co-developer, and to Galp Energia (Sines, Portugal). Both 330 kt/yr plants are expected to be on stream by early 2010. UOP LLC/DARPA have developed renewable energy technology to convert vegetable and algal oils to fuels for military jets (Jet Propellant 8 or JP-8).

15.4.3 H-BIO process Petrobras technology for diesel production from vegetable oils (H-BIO process) involves catalytic hydrogenation of a blend of diesel fractions and vegetable oil in a hydrotreating (HDT) reactor under controlled conditions of high temperature and hydrogen pressure taking advantage of existing plants. Petrobras H-BIO technology is operating in five Brazilian refineries at the end of 2008 with vegetable oil (SBO, CAS) consumption of 425 000 m3/yr, equivalent to 16% of the country’s soybean oil exports in 2005. By 2008, the H-BIO process will cut down 25% of Brazil’s diesel imports. The most important aspect of the H-BIO process is the very high conversion yield, at least 95% v/v to diesel, without residue generation and a small propane production as a by-product. The converted product contributes to improving the diesel pool quality in the refinery, mainly increasing the cetane

756

Biodiesel science and technology

number, reducing the sulphur content and density. The diesel pool quality upgrade will be a consequence of the vegetable oil percentage used in the H-BIO process. Figure 15.22 shows the H-BIO process schematically.

15.5

Perspectives of biomass-to-liquid fuels

Biofuels are a feasible tool to achieve EU policy goals, namely securing and diversifying the energy supply for road transport in an environmentally friendly way. Biomass growth for the current vegetable oil-based diesel technologies (FAME and HVO) is not able to keep pace with growth in fuel demand. Indeed, the production potential of conventional biofuels (bioethanol and biodiesel), based on agricultural feedstock, is insufficient to meet the 2010 policy targets. Hence clean alternative biofuel production pathways need to be investigated, which aim at the integral valorisation of biomass. With a volume of some 700 billion tonnes, cellulose is globally the most widespread organic chemical and therefore highly important as a bio-renewable resource. Only a minor fraction (0.1–0.2 billion tonnes) is used every year as feedstock for further processing. As biomass is highly functionalised, it is preferable to convert biomass into highly valued chemicals rather than under-functionalised and cheap biofuels (essentially alkanes). However, producing biofuels from lignocellulosic material via gas-to-liquid (GTL) technologies – biomass-to-liquid (BTL) fuels – could potentially overcome the aforementioned feedstock limitations. This production pathway is based on a fuel synthesis from gaseous feedstocks (syngas, i.e. CO and H2). Syngas can be obtained from hydrocarbon feedstocks (natural gas, coal) or from biomass (including municipal waste). BTL plants apply the known technology of the Hydrogen

Oilseeds

Crusher/ extractor

Vegetable oil

Diesel fractions

Refinery

Diesel

Methanol

Transesterification

Biodiesel

Glycerol

15.22 Renewable diesel production routes.

Distribution

Fuel station

Evolution of biodiesel and alternative diesel fuels

757

CTL and GTL plants with minor modifications. Many biomass conversion technologies are currently being pushed simultaneously and many of them will probably be used commercially in the long run in order to ensure a reasonable energy mix. Biomass is expected to contribute 10% of the world’s energy demand in the medium term. The biggest contribution will come from biomass-toelectricity, especially when used in combined heat and power generation plants. Algal power plants are now being commissioned in Europe (e.g. Enalg, Venice). Figure 15.23 shows the alternatives to production of energy (in various forms) from biomass and waste. Estimates of global potential of biomass resources range from 3250 Mtoe/ yr (2025) to 5650 Mtoe/yr (2050). At an annual global yield of 13 billion tonnes plant material for food/feed purposes, 8 billion tonnes waste material is generated with an energy content equal to the total global energy needs. Consequently, in principle there is no problem in the use of biomass for energy and materials applications. Local problems may arise though, such as food/energy competition, biodiversity, erosion, water use, etc. The estimated EU 25 potential is 600 Mtoe/yr (2050). Reaching the target of a 12% share of renewables in total domestic energy consumption by 2010 requires around 130 Mtoe of biomass (EU15). A renewables share of 20% of total energy in 2020 necessitates about 210–250 Mtoe of primary energy for the EU25.

Purification and combustion

Electrical energy

Heat

Extraction and transesterification

Biodiesel

Fermentation

Bioethanol

Biomass and waste

FT Diesel

Methanol

Gasification

CO/H2

Reforming/CPO

H2 Pyrolysis

15.23 Biomass-to-energy.

Pyro-oil

DME

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Biodiesel science and technology

The recent EU Biomass Action Plan [84] aims at increasing the biomass contribution to primary energy (1486 Mtoe/yr) from 57 Mtoe/yr in 2001 (or about 4%) to 188 Mtoe/yr in 2010 and 227 Mtoe/yr in 2020. There is sufficient biomass potential in the EU25 to support ambitious renewable energy targets in an environmentally responsible way [85]. 6.4 Mt of biomass are used as a raw material option for the production of chemicals in Europe, representing 8–10% of the industry’s total feedstock. Compared to energy generation, material use of biomass still plays only a minor role. In the United States, a Billion-Ton Vision study [86] identified a potential 1.3 billion tonnes biomass (1 t biomass = 0.43 toe) that could be used as a resource to produce transportation fuels. US expectations are that 90 Bgy of sustainable bioethanol (starch-based and cellulosic) from agricultural residue (corn stover, wheat straw), forestry waste, dedicated energy crops (including switchgrass) and short-rotation woody crops (such as willow and poplar trees) will replace about one-third (or 60 Bgy) of domestic gasoline requirements by 2030 (estimated as 180 Bgy); 15 Bgy would be corn-derived and 75 Bgy from non-food cellulosic feedstocks [87]. It appears that 21 Bgy of cellulosic ethanol could be produced by 2022 without displacing current crops. The Renewable Fuels Standard (see Section 1.2.1) calls for 36 Bgy by 2022. The national goal of 60 Bgy cellulosic biofuels production by 2030 requires a capital investment of US$300 billion. During processing of biofuels, considerable amounts of by-products are generated and their economic use has to be ensured. The possibility to fully use not only the already naturally highly-refined molecular structure of biogene oils but also the 50–80% remainder of the plant for use as fuel will at least double the yield per hectare to 3–4 t (ester + BTL rapeseed plant) and 8–10 t/ha (ester + BTL from palm FFA). ‘Co-generation of biofuels’ faces an even bigger future than second-generation biofuels. Waste materials have high water content that reduces their potential for combustion processes because the energy required to dry the materials exceeds the value of the energy recoverable through combustion. Anaerobic digestion reduces both the volume and mass of the waste materials and typically produces a product that is readily dewatered. Superheated steam drying is another biomass drying technology.

15.5.1 GTL technologies Gas-to-liquid (GTL) technology for transformation of natural gas and other hydrocarbon gases into liquid fuels comprises three processing steps: ∑ ∑

generation of syngas (CO/H2) from any source (coal, NG or biomass) through catalytic steam reforming or partial oxidation; syngas conversion by Fischer–Tropsch (FT) synthesis into n-alkanes; and

Evolution of biodiesel and alternative diesel fuels

∑

759

hydroprocessing by mild hydrocracking of these substances.

Because it is impossible to produce finished products directly from the FT reaction, the key factor is the production of high molecular weight paraffins, namely FT wax, to be hydroprocessed into lighter products (e.g. Syntroleum’s Synfining®). For GTL technology the final product destinations are the automotive fuel market, and the chemical and electrical markets. The main GTL technologies are the production of oxygenate liquid components (MeOH, DME) and the Fischer–Tropsch synthesis for production of highquality middle distillates (i.e. jet, kerosene and diesel fuel), base-oil or waxes. However, many other valuable organic products can be manufactured by selective syngas conversion reactions, such as linear alpha olefines, methane and hydrogen [88]. Unfortunately, GTL is a capital intensive process, where the greater part of the total costs is incurred in the first step. While frontend steps for efficient biomass gasification still need further development, tail-end steps are state-of-the-art. Different gasification technologies are under development. Pyrolytic conversion with entrained flow gasification of biomass into syngas followed by FT synthesis to produce liquid fuels is being run on an experimental scale (see Bioliq® process in Section 15.5.2). Fluidised bed technology (biomass power plant in Güssing, Austria) transforming wood chippings blended with straw and other plant residues, operated in air, produces gas composed of 35–45% H2, and 10% CH4. Dry-ash gasification (British Gas/ Lurgi, Schwarze Pumpe, Germany) of 20% lignite and 80% organic material (shredded plastics, tars, slag, etc.) requires pure oxygen for the generation of syngas composed of 20% CH4, 14% H2 and 32% CO with several minor by-products. Despite the fact that the GTL technology has been around for decades and although many major oil companies have developed FT-GTL technology (including BP, ConocoPhillips, Eni/IFP-Axens, ExxonMobil, Rentech, Sasol, Shell, Statoil, Syntroleum), commercially operated or projected plants (based mainly on coal and natural gas) are currently still rather few (a.o. PetroSA, Mossel Bay, South Africa, 1992; Shell, Bintulu, Malaysia, 1993; Eni/IFPAxens, Sannazzaro, Italy, 2005; Oryx, Qatar, 2006), but more are under development. Natural gas-to-global market options are several: ∑ high-pressure pipelines; ∑ liquefaction and regasification (LNG); ∑ electric power generation and wire transportation (gas-to-wire); and ∑ gas conversion into transportable liquid hydrocarbons (GTL). Improvements in catalyst and reactor technologies are making GTL conversion nowadays an economical prospect for processing cheap ‘stranded’ natural

760

Biodiesel science and technology

gas from reserves located in areas remote from existing markets. Gas is considered stranded if it cannot be injected back into the producing well, or flared, or brought to market economically. Unwanted natural gas (NG) flares burn off the energy equivalent of 1.7 Mbd. Reserves of stranded NG are around 2500 trillion cubic feet, which would make 250 billion barrels of synthetics (from diesel to jet fuel). GTL processing can convert the stranded gas into liquid hydrocarbons such as LPG, naphtha, middle distillates, synthetic crude oil, etc., which can be piped or shipped. Some seven proposed GTL projects (462 750 b/d, primarily to diesel, some lubricating oil or gasoline) are expected by 2010 (Shell, ExxonMobil, Sasol, Conoco) and 13 more projects (Shell, Sasol, Syntroleum, Ivanhoe, Statoil, etc.) would generate an additional 888 250 b/d (source: FACTS, Inc.). The typical fuels which can be obtained from GTL processing and which are suitable for use in road transport are FT naphtha, FT diesel, methanol, dimethylether (DME) and hydrogen. Their main properties are listed in Table 15.21, in comparison with oil-derived analogues. Among the different FT-GTL products, in particular the diesel fraction is highly valued in the downstream market because of its excellent properties that meet environmental regulations. In the long term, FT diesel and DME may compete for compression ignition engine markets. GTL products consist almost entirely of linear paraffins, with less than 5 wt% aromatics, compared to 10–30 wt% aromatics for oil derivates. All GTL products are virtually sulphur free (sulphur content below 1 ppm), since a large part of the sulphur compounds is removed during the syngas production step. GTL diesel has physical and chemical properties similar to oil-derived diesel, but cetane number is higher (Table 15.19). GTL diesel production costs are high. GTL fuel production via the FT route is expected to reach about 3–4% of total diesel demand by 2020 [89].

Table 15.21 Main properties of automotive fuels Fuel

Chemical formula

Net calorific value, MJ/L

Octane number

Cetane number

Oil petrol Oil diesel Oil naphtha FT naphtha FT diesel Biodiesel Methanol DME Hydrogen

C4–C12 C15–C20 C5–C9 C5–C9 C12–C20 C12–C22 CH3OH CH3OCH3 H 2

31.2–32.2 35.3–36.0 31.5 31.5 33.1–34.3 32.8 15.4–15.6 18.2–19.3 8.9

90–95a – 50 40 – – 110–112 – 106

– No 45–53 No – Yes – Yes 70–80 No 51–58 Yes 5 Yes 55–60 Yes – Yes

a

Regular.

Chemical feedstocks

Evolution of biodiesel and alternative diesel fuels

761

15.5.2 BTL technologies In the future, renewable fuels will increasingly be produced from cellulosic or waste materials. There is, however, the question of the economic availability of biomass. Harvesting, treating, transporting, storing and delivering large volumes of biomass feedstock, at a desired quality, all year round, to a (highvolume, low-value) biofuel processing plant raises considerable supply chain issues and requires careful logistical analysis in order to ensure economic viability [90]. Biomass plants based on agricultural residues are to be operated decentrally in order to minimise transport costs. Funding for municipal solid waste (MSW) exploitation for liquid biofuels is minimal compared to that for agricultural wastes. As already mentioned in Section 15.2, converting lignocellulosic biomass (including cereal straw, bagasse, forest residues, and purpose-grown energy crops such as vegetative grasses and short-rotation forests) into biofuel can be accomplished using one of three primary routes: gasification, pyrolysis and hydrolysis. The gasification product is syngas, which is a fuel itself but can also be converted into liquid biofuel via a Fischer–Tropsch (FT) process. The product of pyrolysis is a condensed hydrocarbon liquid or bio-oil. Cellulosic feedstock can be broken down through hydrolysis to simple sugars and fermented to produce cellulosic ethanol (so-called second-generation ethanol). It should be realised, however, that transformation of one energy form into another is always accompanied by losses. If biomass is initially gasified, then turned into diesel fuel through the FT process, and this diesel fuel is then utilised to drive the motor in a vehicle, only a relatively small part of the energy which is contained in the biomass is actually used for the intended purpose. Various technologies are nowadays being proposed for biomass-to-liquid (BTL) processes to renewable diesels and other fuels, which differ in the type of biomass used and in their conversion process. Plant oils are readily accessible for conversion to biofuels. The first technology, already described previously (see Section 15.4), consists in hydrotreatment of vegetable oils and fats (e.g. NExBTL). In a fat-to-liquids project, Dynamic Fuels LLC (a Syntroleum Corp./Tyson Foods Inc. joint venture) will produce 75 MMgy renewable synthetic diesel and (military) jet fuel in Geismar, LA, as from 2010 using Tyson’s low-grade flexible feedstocks (beef tallow, pork lard and poultry fats, greases and oils) and Syntroleum (Tulsa, OK)’s patented BiofiningTM technology (derived from its core FT technology) (see Fig. 15.24). BiofiningTM synthetic fuel is not biodiesel. The product is superior to petro- and biodiesel (Table 15.22) and reduces GHG emissions by 74% compared to the former. The long-term goal is cellulosic diesel and jet fuel via BTL. In this context, it is of interest to notice that Imperium Renewables, Inc. (Seattle, WA) has developed a jet fuel containing 20%

762

Biodiesel science and technology

Natural gas Coal Biomass

Gasification

Syngas

Fischer–Tropsch

FT wax Product upgrading

Diesel and jet

Fats greases oil

Diesel and jet

Biofining™

15.24 Any Source-to-Liquids (XTL) core technology (X = G, gas; X = C, coal; X = B, biomass). Table 15.22 BiofiningTM synthetic fuel properties Fuel property

BiofiningTM diesel

High cetane number Low cloud point Low freeze point Low sulphur (<1 ppm) No aromatics

3 3 3 3 3 3 3

Refined crude diesel

Biodiesel

3

biofuel (babassu- and coconut oil-based) and 80% standard jet fuel. Sunrise Renewables, Inc. (Grand Forks, ND) is to use EERC (University of North Dakota)’s proprietary thermal-cracking technology to convert vegetable oils to aviation fuels, advanced fuels, chemicals and polymers [91]. A 1 : 1 blend of hydroprocessed camelina/jatropha/algal oil (84 : 16 : 1 ratio) and Jet-A fuel satisfies jet fuel performance. In a different development, Choren/Shell technology is based on gasification of solid biomass (agricultural waste and lignocellulosics) by partial oxidation in two stages (at low and high T) and subsequent Fischer–Tropsch conversion (Fig. 15.24). The application of syngas from biomass in GTL production, biomass-toliquid, is quite recent. The main steps in BTL production of fuels are biomass gasification (typically at 1473–1673 K under high pressure) followed by variations of the catalytic Fischer–Tropsch process [92] (see Fig. 15.25). Production of renewable diesel from biomass (wood chips, grass, hay) using gasification (purification)/FT technology is the panacea for the bio-based diesel industry. The technological problem is getting really clean gas without sulphur and metallic impurities, which poison the FT catalyst. In addition, a huge amount of biomass is necessary for one unit of paraffin and the process generates a large amount of heat and steam. All cellulosic BTL technologies are at an early stage of development. There are two types of biomass feedstock that can be employed to produce

Off-gas

Power plant Electricity (for use in plant)

Biomass Light product

FT diesel

Pre-treatment

15.25 Integrated BTL plant.

Gasification

Gas conditioning

Fischer–Tropsch synthesis

Evolution of biodiesel and alternative diesel fuels

Biosyngas

763

764

Biodiesel science and technology

such BTL fuels – woody (wood chips, wood powder and sawdust, wood residues and wood waste) and herbaceous (chaffed dedicated energy crops and straw). Woody feedstock is better suited for energy applications than herbaceous feedstock and also has by far the biggest sustainable mass potential (energy crops and residues) and thus a larger production potential for energy (including BTL) application. Which trees will produce the most reliable feedstock is still a matter of debate. In BTL production the gas is used as a chemical feedstock (syngas) to obtain other products, whereas in power and heat generation the gas obtained from gasification is used as a fuel (product gas). The gasification concepts are therefore different. Whereas the calorific value of the gas is the prime factor for power generation (biomass-to-electricity), for BTL production only the amount of CO and H2 is important, while the calorific value is irrelevant. The biomass gasification step (production of syngas) is the most challenging part of the BTL chain. A hurdle to BTL is that gasifiers can be choosy about feedstocks. The most appropriate gasification concept for BTL ensures a BTL yield that is higher than the electricity yield from biomass. The highest syngas efficiency is achieved when 1 mm wood particles are fed. For herbaceous feedstock, the intermediate transformation into pyrolysis slurry appears to be the optimum solution. The first commercially operated BTL plants are about to come on stream. Some significant EU developments are due to Choren Industries GmbH (Freiberg, Germany): three-phase Carbo-V“ gasification process (clean wood, agricultural waste, coals, herbaceous biomass, wood chips) [93]; Chemrec AB (Sweden): BTL fuel production (methanol, DME, hydrogen) via gasification of black liquor (residual product from the production of chemical pulp and paper); and Värnamo demonstration Integrated Gasification Combined Cycle (IGCC) plant: DME, methanol, hydrogen and FT fuels from woody biomass. Shell is developing biofuels in industrial and academic co-operation (B-Basic, Iogen Corp., Choren). Although cellulosic BTL fuels are gaining an increasing interest, significant quantities of such fuels are not expected to reach the EU automotive market before 2010. The first industrial cellulosic Fischer–Tropsch plant for manufacturing 13.5 kt/yr BTL fuels (SunDiesel‚) using Choren’s gasification technology and Shell’s Middle Distillate Synthesis technology for GTL production has been constructed (end 2007). A full-size prototype plant (200 kt/yr) should be operational by 2012. The world’s first commercial synthetic biofuel production plant (Choren), using wood from forests and commercial waste as wooden fruit crates, will be fully operational by 2013. A novel technology (called Bioliq®) is being developed by KIT/Lurgi to produce a range of different types of liquid fuel and chemicals (such as MeOH) from plant material such as wood and straw [90]. This biosyncrude gasification process involves fast pyrolysis at 773 K yielding a thick oily

Evolution of biodiesel and alternative diesel fuels

765

liquid or biosyncrude (see also Table 1.6), which is then exposed to a stream of oxygen and gasified at high pressure (> 6 MPa) and temperature (1673 K) forming syngas. A fully operating Bioliq® pilot plant is scheduled for 2012. A central 1 Mt/yr biosynfuel plant could produce liquid fuel for about 70.56–1.04/L provided an adequate decentralised infrastructure for pyrolysis to liquid biosyncrude is set up, which minimises biomass transportation. Forestry is potentially more promising than biofuels from crops. Globally 125 Mha of industrial forestry plantations, or 3.5% of the total forest area, would suffice [94]. The impact of forestry biofuels – still some 10 years off – will probably be most pronounced in countries with intense forestry industries (Scandinavia, Scotland, Austria). Widespread use of wood-based transport biofuels in liquid form is foreseen in Scandinavia by 2018. Woodbased biofuels make good use of forestry waste while avoiding the use of farm land, and the damaging NOx emissions from agricultural biofuels. As between two and nine times more carbon emissions are avoided by capturing carbon in trees and forest soil than by cultivating agricultural biofuels to replace fossil fuels, waste biomass from forestry, such as black liquor or lignin, provides an ideal solution. Black liquor is the watery solution left over once the cellulose has been extracted from the pulping waste and is made up of lignin remains and inorganic chemicals. Choren Industries GmbH has partnered with the Norwegian paper company Norske Skog to explore building full-scale, renewable diesel production facilities in Norway, using woody biomass as a feedstock. Neste Oil (Varkaus, Finland) is developing a similar alkane bio-based diesel plant from biomass using gasification/FT technology in partnership with Stora Enso (commercial sales by 2014–15). Installation of 1 Mt/yr BTL capacity in Germany is foreseen in the medium term. Demonstration plants based on Chemrec’s technology are installed at the Kappa Kraftliner mill in Piteå (Sweden) and at the New Bern mill in North Carolina (USA). The synthesis of FT fuels in Värnamo was due in 2007–08 [95], but a large-scale commercial operation is not expected before 2011–12. BiofiningTM/BTL integration (using cellulosic biomass) is targeted for 2012. Both cost and CO2 emission profile from these processes depend on the process technology and biomass source (waste product or energy crop; alone or in combination with an external energy source). The expected well-to-wheels net CO2 emission of the Choren process is about 10% of petrofuels, while coal-to-liquids is apparently about 200%. FT diesel is the only BTL fuel that is ready for a large-scale application in diesel engines even today, preferably blended with oil-derived diesel. Bioethanol can be obtained via conventional thermal gasification of biomass to syngas combined with catalytic processes. Alternatively, fermentation processes are used which can only deal with one feedstock type at a time. The accessibility to biochemical hydrolysis and sugar release is restricted by the cell wall structure. Energy-intensive chemical and physical pre-treatments,

766

Biodiesel science and technology

or thermochemical routes, are used to open up the walls for enzymatic hydrolysis. Pre-treatment of biomass with steam or acid releases cellulose from lignin. Hydrolysis using costly cellulase enzymes is then needed to free the sugars. Cyanobacterial cellulose is easier to convert into biofuels than cellulose produced in plants [96]. In a recent advance in cellulosic fuel technology, gentle hydrolysis of cellulose in wood and inedible plant material has been achieved by combining ionic liquids (e.g. BMIMCl) and solid catalysts (Amberlyst®15Dry), thereby easing the crucial first stage in converting waste biomass [97]. The reaction products, cellulose oligomers and sugars, can be transformed enzymatically into fuels or chemical feedstocks. While the US is favoured in terms of cellulosic feedstock availability (corn belt), Europe needs to focus on waste feedstocks. This affects the technological options. As fermentation works best for biofuel production from single waste streams (such as corn stover), production of advanced biofuels in the UK and Europe is more likely to prefer thermochemical routes. No cellulosic technologies have been commercialised and the technology is still unproven on a large scale. While cellulosic ethanol is considered being some five years away from significant production, many commercial plants are already being planned. There are several examples of ongoing industrial processes. The UK’s first cellulosic ethanol demonstration-scale facility (TMO Renewables, Guildford) has been running for several years converting various sources of feedstock (corn stover, corn cobs, straw, distiller’s grain, brewery waste, agricultural waste, MSW) using a thermophilic bacterium (TM242). Pilot plants in Sweden and Norway use waste streams of cellulose-based material. Verenium Corp. (Cambridge, MA) is operating a 1.4 Mgy demonstration unit in Jennings, LA, to produce ethanol from non-food cellulosic biomass. A lignocellulosic bioethanol demonstration plant (3 ML/yr) in Ottawa is run by Iogen Corp. with separate hydrolysis and fermentation by yeast using wheat, oat and barley as feedstock. Iogen Energy Corp. (Ottawa), Royal Dutch Shell (The Hague) and Sekab (Örnsköldsvik, Sweden) are partnering in the development of ethanol using lignocellulosic sources (plant waste and wood). Efforts are also under way to enhance the efficiency of biocatalysts used in the Iogen cellulosic ethanol production process (co-operation with Codexis, Inc., Redwood City, CA). Also the French Futurol project aims at making bioethanol by fermenting lignocellulosic biomass. Dow and the US National Renewable Energy Laboratory (NREL) are to jointly develop a process using a chemical catalyst to convert non-food biomass such as corn plant leaves and wood waste. A joint venture between BP and Verenium is planning a commercial-scale production unit (36 Mgy) of cellulosic ethanol from ‘energy grasses’ (including sugarcane and miscanthus) in Highlands County, FL, by 2012. Similarly, a

Evolution of biodiesel and alternative diesel fuels

767

DuPont (Wilmington, DE)/Danisco (Copenhagen) joint venture pilot-scale refinery will convert the high cellulose content of switchgrass (Panicum virgatum) fuel crops into bioethanol as from 2010. Biofuels derived from low-input high-diversity (LIHD) mixtures of native grassland perennials can provide more usable energy, greater GHG reductions, and less agrichemical pollution per hectare than soy biodiesel or corn grain ethanol [98]. LIHD biofuels are carbon negative; they can be produced on agriculturally degraded lands and thus need to neither displace food production nor cause loss of biodiversity via habitat destruction. Switchgrass is being developed as a perennial bioenergy crop. DuPont/Genencor joint venture is developing a low-cost technology to make cellulosic ethanol from corn and sugarcane waste (pilot 2009; commercial production 2012). Most bioethanol producers use either gasification or fermentation technology. Recently, thermochemical and biochemical processes were coupled in waste-to-ethanol conversion. Ineos Bio (UK) claims to be ready to convert a wide range of different wastes (biomass, MSW) to ethanol and renewable power on a commercial scale by gasification to syngas followed directly by fermentation with anaerobic Clostridium ljungdahlii bacteria. This eliminates the need for the hydrolysis step to break up the (hemi)cellulose fractions of the biomass. Second-generation bioethanol (from the biodegradable portion of household and commercial waste) is a capital-intensive technology compared with first-generation bioethanol. In Nov. 2008 a joint venture between Amyris Biotechnologies (Emeryville, CA) and CrystalSev Biofuels (Ribeirão Preto, SP/Brazil) has opened a plant to produce renewable diesel from sugarcane. This diesel substitute, obtained by a large-scale fermentation process, is forecast to achieve lower costs on a much greater scale than vegetable oil-based biodiesels [99]. California-based companies BioGold Fuels Corp. and Energy Dynamics Corp. Intl. intend producing renewable diesel from municipal solid waste streams (waste-todiesel). Coal can be transformed into liquid fuels in two ways: gasification with water vapour and oxygen into syngas, followed by FT and mild hydrocracking (see also Fig. 15.1), and direct liquefaction using hydrogen under high pressure. Selexol technology (UOP LLC, Des Plaines, IL) is available to remove contaminants from syngas made from coal. Thermochemical CTL (coal-to-liquid) technologies were applied in Germany during World War II (with production of 0.6 Mt/yr in 1944). At present, Sasol (Secunda, South Africa) is operating large CTL plants (6 Mt/yr) for transportation fuel production and is planning coal liquefaction plants in Indonesia by 2015 for the production of more than 1 Mbd of gasoline and oil products. As with natural gas, coal can be converted into liquid synthetic fuels with a much higher quality than conventional oil-derived fuels. These synfuels are sulphur free. CTL and GTL synfuel technology based on syngas (CO/H2) are more

768

Biodiesel science and technology

complex and expensive than an oil refinery. The technologies will become competitive when the raw materials, coal and gas, are considerably cheaper than oil. CTL fuel projects compete for coal supplies for other uses (e.g. coal power stations), much in the same way as biodiesel and food compete for vegetable oils. Sasol is also looking into co-feeding coal with biomass. Commercial development progression of proven Fischer–Tropsch technology can be summarised as follows: gas-to-liquids (GTL) technology: fully demonstrated; coal-to-liquids (CTL) applications: ongoing; and cellulosic biomass-to-liquids (BTL) applications: developing. Table 15.23 summarises Big Oil’s renewable biofuels interests. Bioenergy clearly contributes to the security and diversity of energy supply since its production and supply patterns differ from those of fossil fuels. BTL fuels have a greater potential than conventional biofuels to contribute to the EU policy objective of replacing traditional oil-based automotive fuels (petrol and diesel), owing to larger feasible land availability for woody and herbaceous biomass than that for agricultural feedstocks, and higher biofuel yield per hectare than that of conventional biofuels and of biodiesel in particular (Table 15.24). In fact, since in BTL fuels the entire plant can be used rather than seeds only, as for first-generation biofuels, a much Table 15.23 Big Oil’s renewable biofuel projects Company Focus Activities

Commercialisationa

BP Amoco

2008 2012 2012

Biodiesel from animal fat TLW hydrotreating Jatropha oil (biodiesel) D1 Oils (plantations)b ‘Energy grasses’ Cellulosic bioethanol

Chevron Corp. Second/third-generation   non-food feedstocks

Cellulosic bioethanol Algae-to-biodiesel

ConocoPhillips Second/third-generation SBO hydrotreating   (Whitegate)   hydrocarbon fuels TLW hydrotreating   (Tyson jv) Biofuel-from-algae Royal Dutch Biodiesel-from-algae Cellana (HI)   Shell BTL from biomass Choren (Germany)   feedstocks Biogasoline from Virent (WI)   biomass Cellulosic ethanol Iogen Corp./Sekab jv ExxonMobil Hydrocarbons-from- Synthetic Genomics   algaec   (SGI) a

Planned. Joint venture dissolved 2009. c Continuous production. b

n.d. n.d. 2006 2009 n.d. 2012 2013 n.d. n.d. n.d.

Evolution of biodiesel and alternative diesel fuels

769

Table 15.24 Feasible biofuel yield per hectare from various feedstocks and conversion routes (after ref. [100]) Feedstock

Minimum yield (GJ/ha)

Maximum yield (GJ/ha)

Sunflower biodiesel Rapeseed biodiesel Wheat bioethanol Potato bioethanol Sugar beet bioethanol BTL diesel OFa BTL diesel SRFb BTL diesel HECc

26d 38 46 81d 123 29 46 27

26d 46 58 81d 144 69 85 81

a

Ordinary forestry. Short-rotation forestry. c Herbaceous energy crops. d Expected yields. b

higher efficiency per area is achieved with typically an output per ha of about 4000 L of BTL fuels compared to 1500 L of conventional biodiesel. This allows the targeted growth rate in EU biofuel production to be met. Advanced biofuel technologies, based on lignocellulosic biomass, have the potential to decouple the competition between biofuel and food production and make the UK’s Renewable Transport Fuels Obligation (RTFO) of 10% by 2015 sustainable. In the medium term BTL fuels could compensate to a large extent the middle distillate imports for transport in the EU. However, at present, transport fuel consumption grows faster than the feasible supply of BTL fuels. Challenges for bio-based diesel fuels are several. FAME is limited by vehicle technology requirements and feedstock volumes. HVO is limited only by feedstock volumes, which, however, are more extensively available than for FAME. Challenges of FT-BTLs are immature technology and investment costs. Various estimates have been made concerning the feasible potential of BTL fuels to replace automotive fuels and in particular diesel in the EU by 2010–20. Figure 15.26 shows a market penetration estimate for FAME, HVO and FT-BTL. Without substantial changes in land-use patterns, the feasible annual production of bio-based diesel could meet 10% of the projected automotive diesel demand in the EU25 some time after 2010 (58% from agricultural surplus, 27% from crops grown on set-aside land and 15% from wood waste and residues) (see also Table 15.5). With changes in land-use patterns, the substitution potential of BTL fuels may reach 20% of all transport fuels by 2010–20. According to other predictions of the expected production of various biofuels in the EU27, second-generation bioethanol would be introduced by 2012 whereas first-generation bioethanol would disappear by 2015; biodiesel might peak at 2025 at the start of bio-FT-diesel [101]. As

770

Biodiesel science and technology 12 FT-BTL

Bio in diesel fuel pool (%)

10

HVO FAME

8 6 4 2 0 2006

2010

Year

2014

2018

15.26 Market penetration estimate for bio-based fuels (after ref. [15]).

BTL technology is commercialised, current biodiesel production will not necessarily be shut down but is expected to continue serving markets that value its biodegradability and non-toxicity (Health, Safety and Environment (HSE)-sensitive fuelling). BTL fuels are more energy-intensive than conventional diesel and petrol and natural gas-based fuels. Therefore, from an energy efficiency point of view, the application of BTL fuels for transport would not appear to make much sense, because it will further increase the energy demand of transport and, thus, the total final energy consumption. Nevertheless, due to different production patterns of fossil (oil and natural gas) and biomass fuels, the application of BTL fuels at higher gross energy cost can be justified by security and diversity of energy supply benefits (lower energy import dependence of the EU beyond 2010), and improved environmental performance. The net energy consumption of BTL fuels is lower than that of oil-derived petrol and diesel, owing to the closed carbon/CO2 cycle of biomass. The energy demand of BTL fuel chains is also lower than that of conventional bioethanol and biodiesel, produced from agricultural feedstock. For proven technology (transesterification and hydrotreating), the production costs and GHG benefits are fairly close. The net GHG emissions of BTL fuels are substantially lower than those of conventional diesel and petrol and of all natural gas-based fuels. BTL fuels also offer GHG savings over conventional biofuels. Hence, BTL fuels appear to be the most promising option to reduce the CO2 emissions from transport. Industry does not yet know how to convert biomass to fuels on a large scale at an acceptable cost to the consumer. For various reasons (immature

Evolution of biodiesel and alternative diesel fuels

771

technologies, more sophisticated transformation process, etc.), BTL fuels will initially be 2–3 times more expensive than conventional oil-derived automotive fuels, but with prospects for improvement due to economies of scale, learning curve, synergies, etc. Table 15.25 compares diesel cost from selected technologies (transesterification, hydrotreating and Fischer–Tropsch). The main components of BTL production costs are feedstock costs and direct capital costs, as well as logistics costs. As the complexity of the BTL process requires large-scale plants to fully exploit the economies of scale, the availability and logistics of the biomass are crucial. Biomass resource is far more dispersed than oil. A key consideration for next-generation biofuels is thus the availability of sufficient biomass resources, preferably within 60 km of a production plant. A disadvantage of biorefineries is transportation cost of highly voluminous vegetable matter of high water content. BTL fuels have the potential to become cheaper than conventional bioethanol and biodiesel. Besides the mutual competition amongst different BTL fuels (BTL diesel, DME, methanol, BTL naphtha and hydrogen), their automotive application faces strong competition from conventional oil-derived fuels (see Table 15.26). Conventional biofuels do not appear strong opponents, since their feasible production potential is lower, while their production costs are similar to or even higher than those of BTL fuels. Beyond the transport sector, BTL fuels compete with other non-energy applications of BTL semi-finished materials and end products, with other energy applications of the available biomass resource and with non-energy uses of land and biomass. Land availability is the core factor that limits the biomass potential. BTL fuels are in mutual competition for the use of the prospective bio-syngas. Hence, the selection of potentially promising market niches for BTL fuels should take into account a number of inter-related factors and trade-offs in pursuing a sustainable energy system. At present, different national approaches favour biomethanol and DME in Sweden, and BTL diesel in Germany. The production potential of black liquor is strongly concentrated in pulp and paper producing countries (Sweden, Finland, Austria). The optimum positioning of different BTL fuels is a challenging task [100]. Table 15.25 Comparison of diesel cost from selected technologies (after ref. [102]) Technology Feedstock

Feedstock input (kt/yr)

Feedstock Production Production cost (MMgy) cost (US$) (US$/gal)a

Transesterification Soy oil Hydrotreating Soy oil FT Hardwood

200 500 700

0.35/lb 0.35/lb 50/dry ton

a

52 128 28

2.98 3.00 3.66

Biofuel production costs do not include cost of transportation to terminal or enduser.

772

Biodiesel science and technology

Table 15.26 Relative ranking of BTL fuels vs. fossil fuels (after ref. [100])

FT naphtha FT diesel

Methanol DME Hydrogen

Security and diversity   of supply Energy efficiency GHG emissions Local-polluting emissions Costs

++

++

++

++

++

– –/– ++ ++ – –/–

– –/– ++ ++ – –/–

– –/– ++ ++ – –/–

– –/– ++ ++ – –/–

–/0 ++ ++ – –/–

Key: (++) Significant benefits; (0) No impact/similar performance; (–) Moderate penalities; (– –) Significant penalties.

15.6

Renewable energy and biomass

Worldwide biomass ranks fourth as an energy resource, providing about 13% of the world’s energy needs. Biomass now accounts for only 3% of the primary energy consumption in industrialised countries, but for over 50% in South Asia and Africa (exceeding 90% in Burundi and Uganda), mainly in the form of wood, for fuel. World production of biomass, mostly wild plant growth, is estimated at 146 Bty [103]. Biomass is currently the most used renewable energy source and will continue to be so in the foreseeable future. For biomass resources several potential sources may be used: agricultural and forest residues, algae and grasses, animal manure, organic waste and biomaterials. The biomass-intensive future energy supply scenario includes 385 Mha of biomass energy plantations globally in 2050 [104]. In industrialised countries, the main biomass processes used in the midterm future are expected to be direct combustion of residues and wastes for electricity generation, biodiesel and bioethanol as liquid fuels, and combined heat and power generation from energy crops. Biomass will be of increasing importance as a feedstock to the chemical industry. Biomass provides local environmental benefits and contributes to sustainability. Crops can be grown to satisfy changing end-use needs [105]. Biofuels for the transport sector (biodiesel, bioethanol, BTL, MtS), produced from biomass, are meant to replace fossil-based fuels and are expected to reduce undesired dependence on imported petroleum. This is all the more necessary as the declining availability of fossil fuels (in quantity and price) will affect national security of energy supplies. In the long term, countries with surplus biomass potential (in particular tropical areas, including Africa) could become exporters of various forms of bioenergy. Table 15.27 indicates reasonable expectations for biofuels. The biomass conversion processes of Fig. 15.27 summarise the organic chemical industry of the future. Table 15.28 shows the global renewable energy expectations by 2040 when approximately half of the global energy supply could be on account of renewables [106]. In the future, biomass has the potential to provide

Fuel Feedstock Production areas GHG reductiona,b Productionb Biofuels yieldb cost per ha

Land use

Ethanol Wheat, maize Sugar cane Cellulose, residues Biodiesel RSO, SBO, SNO PMO Jatropha Algae Biogas (CNG) Wastes, crops (SNG, GTL) Biomass, residues a

US, EU, (PRC) Brazil, India Thailand Nonec US, EU, South America South-East Asia South-East Asia, Africac US, EU, Asiac Sweden, India Allc

+/++ +++

++ +/++

++ +++

Cropland Cropland

+++ +/++ ++ +++ +++ +++ +++

++/+++ +/++ +/++ ++/+++ ++++ ++/+++ +++

+++ + ++/+++ +/++ ++++ +++ +++

Cropland, wastelands Cropland Coastal lands Degraded lands Marginal, marine waters All land All land

In comparison to fuel (petroleum). +, low; ++, moderate; +++, high; ++++, very high. c Feedstocks for next-generation biofuels not yet commercially available. b

Evolution of biodiesel and alternative diesel fuels

Table 15.27 First- and next-generation biofuels

773

774

Biodiesel science and technology Syngas platform Thermochemical

Conditioned gas

Clean gas

Fuels, chemical and materials

Combined heat and power

Biomass

Residues Sugar platform Biochemical

Sugar feedstocks

15.27 Co-generation of a marketable biomass-derived mix.

Table 15.28 Global renewable energy scenario by 2040

2001

2040

Total consumption (Mtoe) Biomass Geothermal Hydro (SHP, MHP, LHP) Wind Solar thermal (electricity) Photovoltaics (solar cells) Marine (tidal/wave/ocean) Total renewable energy sources Renewable energy source contribution (%)

10 038 1280 43.2 32.2 4.7 4.2 0.2 0.05 1365.5 13.6

13 310 3271 493 547 688 548 784 20 6351 47.7

Source: EUREC (2006).

a cost-effective and sustainable supply of energy while at the same time meeting GHG targets. Limited availability of fossil fuels and renewable energy sources on a local scale may determine the sustainability of future energy supplies. Renewable energy sources that use indigenous resources have the greatest potential to provide the sustainable energy sources. Very significant contributions to the global energy provision are expected to derive from photovoltaics (PV) and wind energy (see Table 15.28). Sunlight, the most abundant energy source on earth, at present makes up only a very small direct contribution (<< 1%) to the world total primary energy supply. Solar PV energy as a renewable energy source has the greatest potential worldwide but its further development requires substantial support. Photovoltaics

Evolution of biodiesel and alternative diesel fuels

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is expected to be the largest renewable electricity source in 2040 with a production of 25% of global power generation. However, solar power is site specific, intermittent and less suitable for immediate supply. Wind energy is another form of indigenous supply almost permanently available and widely distributed, with limitations based on geography, meteorology and environmental pollution (particularly when concentrated on a large scale). An EU directive is to boost wind energy capacity from 65 GW (2008) to 230 GW (2020). Shell has expressed doubts on the economic viability of renewable energies such as wind, solar and hydroelectric power, and concentrates on biofuels.

15.7

Bibliography

K. Waldron (ed.), Bioalcohol Production: Biochemical Conversion of Lignocellulosic Biomass, Woodhead Publishing Ltd, Cambridge (2009). D.M. Mousdale, Biofuels. Biotechnology, Chemistry, and Sustainable Development, CRC Press, Boca Raton, FL (2008). E. Furimsky, Carbons and Carbon Supported Catalysts in Hydroprocessing, RSC Publishing, Cambridge (2008). J.H. Clark and F. Deswatre (eds), Introduction to Chemicals from Biomass, John Wiley & Sons, Ltd, Chichester (2008). Verkenningscommissie Energieconversieonderzoek (KNAW), Duurzaamheid duurt het langst, Koninklijke Nederlandse Akademie van Wetenschappen, Amsterdam (2007). Nexant Inc./ChemSystems, Liquid Biofuels: Substituting for Petroleum (Multiclient Study), White Plains, NY (2006). Biofuels Research Advisory Council (BIOFRAC), Biofuels in the European Union: A Vision for 2030 and Beyond, European Commission, DirectorateGeneral for Research Sustainable Energy Systems, Luxembourg (2006), EUR 22066; http://europa.eu.int/comm/research/energy/. B. Kavalov and S.D. Peteves, Status and Perspectives of Biomass-to-Liquid Fuels in the European Union, EUR 21745 EN, European Commission, Directorate-General Joint Research Centre, Institute for Energy, Petten (2005). B. Kavalov, Biofuel Potentials in the EU, European Commission, DirectorateGeneral Joint Research Centre, Institute for Prospective Technological Studies, Petten (2004). J. Goldemberg and T.B. Johansson, World Energy Assessment Overview: 2004 Update, UNDP, New York, NY (2004). B. Kavalov and S.D. Peteves, Impacts of the Increasing Automotive Diesel Consumption in the EU, European Commission, Directorate-General Joint Research Centre, Institute for Energy, Petten (2004). E van Thuij, C.J. Roos and L.W.M. Beurskens, An Overview of Biofuel

776

Biodiesel science and technology

Technologies, Markets and Policies in Europe, Energy Research Centre of the Netherlands, Petten (2003). J. Goldemberg, World Energy Assessment: Energy and the Challenge of Sustainability, UNDP, New York, NY (2000). International Energy Agency, Automotive Fuels for the Future – The Search for Alternatives, IEA, Paris (1999). D.L. Klass, Biomass for Renewable Energy, Fuels and Chemicals, Academic Press, San Diego, CA (1998). N. Martini and J. Schnell (eds), Plant Oils as Fuels. Present State of Science and Future Developments, Springer-Verlag, Berlin (1998). EUREC Agency, The Future for Renewable Energy, Prospects and Directions, James and James Science Publisher, London (1996). T.B. Johansson, H. Kelly, A.K.N. Reddy and R.H. Williams (eds), Renewable Energy: Sources for Fuels and Electricity, Island Press, Washington, DC (1993). R.B. Anderson, The Fischer–Tropsch Synthesis, Academic Press, New York, NY (1984).

15.8

References

[1] A.E. Farrell, R.J. Plevin, B.T. Turner, A.D. Jones, M. O’Hare and D.M. Kammen, Ethanol can contribute to energy and environmental goals, Science 311 (2006) 506–8. [2] H. Shapouri, J.A. Duffield and M. Wang, The Energy Balance of Corn Ethanol: An Update, US Dept. Agriculture, Agricultural Economic Report No. 814 (2002) 1–15. [3] P.O. Ward and A. Singh, Microbial technology for bioethanol production from agricultural and forestry wastes, in Microbial Biotechnology in Agriculture and Aquaculture (R.C. Ramesh, ed.), Science Publishers, Inc., Enfield, NH (2005). [4] D. Pimentel and T.W. Patzek, Ethanol production using corn, switchgrass, and wood. Biodiesel production using soybean and sunflower, Natl. Resour. Res. 14 (2005) 65–76. [5] J.D. Branson (to Best Biofuels), System and method for extracting energy from agricultural waste, US Pat. Appl. 2003/0111410 A1 (17 Dec. 2002). [6] R. Sims, M. Taylor, J. Saddler and W. Mabee, From 1st- to 2nd- Generation Biofuel Technologies, OECD/IEA, Paris (Nov. 2008). [7] J. Ebert, Furfural: future feedstock for fuels and chemicals, Biomass Mag. (9)2008 31–4. [8] E. de Jong, Furanics: next generation biofuels with superior characteristics, Proc. 6th European Motor Biofuels Forum, Rotterdam (9–10 Jan. 2008). [9] Y. Román-Leshkov, C.J. Barrett, Z.Y. Liu and J.A. Dumesic, Production of dimethylfuran for liquid fuels from biomass-derived carbohydrates, Nature 447 (2007) 982–5. [10] K. Zhang, M.R. Sawaya, D.S. Eisenberg and J.C. Liao, Expanding metabolism for biosynthesis of nonnatural alcohols, Proc. Natl. Acad. Sci. (USA) 105 (2008) 20653–8.

Evolution of biodiesel and alternative diesel fuels

777

[11] Biofuels Research Advisory Council (BIOFRAC), Biofuels in the European Union: A Vision for 2030 and Beyond, European Commission, DirectorateGeneral for Research Sustainable Energy Systems, Luxembourg (2006), EUR 22066. [12] B.J. McAfee and A. Taylor, A review of the volatile metabolites of fungi found on wood substrates, Nat. Toxins 7 (1999) 283–303. [13] A.-L. Sunesson, W.H.J. Vaes, C.A. Nilsson, G. Blomquist, B. Andersson and R. Carlson, Identification of volatile metabolites from five fungal species cultivated on two media, Appl. Environ. Microbiol. 61 (1995) 2911–18. [14] G.A. Strobel, B. Knighton, K. Kluck, Y. Ren, T. Livinghouse, M. Griffin, D. Spakowicz and J. Sears, The production of myco-diesel hydrocarbons and their derivatives by the endophytic fungus Gliocladium roseum (NRRL 50072), Microbiol. 154 (2008) 3319–28. [15] S. Mikkonen, Second-generation renewable diesel offers advantages, Hydrocarb. Proc. (Feb. 2008) 63–8. [16] V. Lecocq, S. Maury and D. Bazer-Bachi (to IFP), Method for producing alcoholic esters from triglycerides and alcohols using heterogeneous catalysts containing phosphate, or an organophosphorated compound of a Group 4 metal, PCT Int. Publ. No. WO 2008/135665 A1 (13 Nov. 2008); FR Pat. 2008/000389 (21 Mar. 2008). [16a] S.R. Schill, A solid catalyst unlike the rest, Biodiesel Mag. 6(7) (2009) 44–8. [17] W.A. Summers, An effective solution to the glycerin glut, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [18] R.G. Stern, G. Hillion, J.-J. Rouxel and S. Leporq (to IFP), Process for the production of esters from vegetable oils or animal oils and alcohols, US Pat. 5,908,946 (1 June 1999). [19] G. Hillion, B. Delfort, D. LePennec, L. Bournay and J.-A. Chodorge, Biodiesel production by a continuous process using a heterogeneous catalyst, Prepr. Symp. ACS, Div. Fuel Chem. 48(2) (2003) 636–8. [20] C. Baudouin, Biodiesel 2nd generation technology, Paper presented at WRA 2005 – 6th European Fuels Conf., Paris (14–16 Mar. 2005). [21] L. Bournay, D. Casanave, B. Delfort, G. Hillion, J.-A. Chodorge, New heterogeneous process for biodiesel production: a way to improve the quality and the value of the crude glycerin produced by biodiesel plants, Catal. Today 106 (2005) 190–2. [22] L. Bournay, G. Hillion, P. Boucot, J.-A. Chodorge, C. Bronner and A. Forestiere, Process for the production of alkyl esters from vegetable or animal oil and aliphatic monohydric alcohol, Eur. Pat. 1,352,893 A1 (15 Oct. 2003). [23] M. Koncar, W. Glasl, M. Mittelbach, M. Siebenhofer, E. Jeitler, W. Hammer and H. Goessler (to BDI – Biodiesel International AG), Production of carboxylic acid alkyl esters, PCT Int. Publ. No. WO 2007/012097 A1 (2 Jan. 2007). [24] E. Ahn and T. Hilber, Experiences with new catalysts for production of high quality biodiesel from vegetable oils and animal fats, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [25] W. Glasl, M. Mittelbach, M. Siebenhofer, E. Jeitler, W. Hammer, H. Gossler and M. Koncar (to BDI – Biodiesel International AG), Process for the production of carboxylic acid esters, US Pat. Appl. 2008/0227994 A1 (18 Sep. 2008). [26] AmberlystTMBD20 Solid Catalyst FFA Esterification Technology, Rohm & Haas Co. Technical Bulletin (Nov. 2007); www.amberlyst.com.

778

Biodiesel science and technology

[27] R.M. Banavali, T.L. Hanlon, G. Pierce and A.K. Schultz, The use of polymeric resins in biodiesel processing, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [28] M. Pell, AmberlystTM BD20 technology: A solid-catalyst process for converting high free-fatty acid feedstocks to biodiesel by esterification, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [29] C.H. Riesz and H.S. Weber, Catalysts for selective hydrogenation of soybean oil. III. Hydrogenation catalysts prepared on molecular sieves and other supports, J. Am. Oil Chem. Soc. 41 (1970) 464–8. [30] E.S. Jang, M.Y. Jung and D.B. Min, Hydrogenation for low trans and high conjugated fatty acids, Comp. Rev. Food Sci. Saf. 4 (2005) 22–30. [31] C.H. Riesz and H.S. Weber, Catalysts for selective hydrogenation of soybean oil. I. An experimental method for evaluating selectivity, J. Am. Oil Chem. Soc. 41 (1970) 380–3. [32] C.H. Riesz and H.S. Weber, Catalysts for selective hydrogenation of soybean oil. II. Commercial catalysts, J. Am. Oil Chem. Soc. 41 (1970) 400–6. [33] P.F. Bondioli, M.N. Ravasio and F. Zaccheria (to CNR and Università degli Studi di Milano), A method for the production of biodiesel, starting from high iodine number fatty substances, PCT Int. Publ. No. WO 2006/111997 A1 (26 Oct. 2006). [34] N. Ravasio, Workshop on Bioraffineria, Carburanti e Materie Prime da Fonti Rinnovabili per uno Sviluppo Sostenibile, Milan (19 Nov. 2008). [35] U. Ravnskov, The Cholesterol Myth Exposing the Fallacy that Saturated Fat and Cholesterol Cause Heart Disease, New Trends Publishing, Inc., Washington, DC (2000). [36] M.N. Ravasio, F. Zaccheria, P.F. Bondioli and L. Della Bella, Selective hydrogenation as a value tool for the production of high quality biodiesel, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). [37] M.O. Jung, S.H. Yoon and M.Y. Jung, Effect of temperature and agitation rate on the formation of conjugated linoleic acids in soybean oil during hydrogenation process, J. Agric. Food Chem. 49 (2001) 3010–16. [38] M.O. Jung, J.W. Ju, D.S. Choi, S.H. Yoon and M.Y. Jung, CLA formation in oils during hydrogenation process as affected by catalyst types, catalyst contents, hydrogen pressure, and oil species, J. Am. Oil Chem. Soc. 79 (2002) 501–10. [39] A.J. Dijkstra, Revisiting the formation of trans isomers during partial hydrogenation of triacylglycerol oils, Eur. J. Lipid Sci. Technol. 108 (2006) 249–64. [40] M.J. Kokken, Hydrogenation in practice, in Proc. World Conference on Oilseed Technology and Utilization (T.H. Applewhite, ed.), AOCS Press, Champaign, IL (1993), pp. 173–9. [41] W. Normann, Process for converting unsaturated fatty acids or their glycerides into saturated compounds, British Pat. 1,515 (21 Jan. 1903). [42] G. Yusem and P.N. Pintauro, The electrocatalytic hydrogenation of soybean oil, J. Am. Oil Chem. Soc. 69 (1992) 399–404. [43] G. Yusem, P.N. Pintauro, P.C. Cheng and W. An, Electrocatalytic hydrogenation of soybean oil in a radial flow-through Raney nickel powder reactor, J. Appl. Electrochem. 26 (1996) 989–97. [44] K. Mondal and S.B. Lalvani, Electrochemical hydrogenation of canola oil using hydrogen transfer agent, J. Am. Oil Chem. Soc. 80 (2003) 1135–41. [45] H. van Toor, G.J. van Rossum and M. Kruidenberg, Low trans-fatty acid fat

Evolution of biodiesel and alternative diesel fuels

[46]

[47]

[48]

[49]

[50]

[51] [52] [53] [54]

[55] [56]

[57]

[58] [59]

[60]

[61] [62]

[63]

779

compositions; Low-temperature hydrogenation, e.g., of edible oils, US Pat. Appl. 2005/0027136 A1 (3 Feb. 2005). M. Härröd, M.-B. Macher, S. Van den Hark and P. Møller, Hydrogenation at supercritical single-phase conditions, in High Pressure Process Technology: Fundamentals and Applications (A. Bertucco and G. Vetter, eds), Elsevier, Amsterdam (2001), pp. 496–508. M. Härröd, A. Holmqvist and S. Van den Hark, Selective hydrogenation of functional groups in substrates and partially hydrogenated fatty acids and fatty acid derivatives, PCT Int. Publ. No. WO 2005/095306 A1 (13 Oct. 2005). P.A. Jacobs, P.J.A. Maes, S.J. Paulussen, M. Tielen, D.F.E. Van Steenkiste and L.K. Van Looveren, Elimination of trans-unsaturated fatty acid compounds by selective adsorption with zeolites, PCT Int. Publ. No. WO 98/54275 (3 Dec. 1998); US Pat. 6,229,032 B1 (8 May 2001). A.F. Pérez-Cadenas, F. Kapteijn, M.M.P. Zieverink and J.A. Moulijn, Selective hydrogenation of fatty acid methyl esters over palladium on carbon-based monoliths. Structural control of activity and selectivity, Catal. Today 128 (2007) 13–7. T. Boger, M.M.P. Zieverink, M.T. Kreutzer, F. Kapteijn, J.A. Moulijn and W.P. Addiego, Monolithic catalysts as an alternative to slurry systems: hydrogenation of edible oil, I & EC Res. 43 (2004) 2337–44. A.E.W. Beers and G. Mangnus, Hydrogenation of edible oils for reduced transfatty acid content, Inform 15 (2004) 404–5. A. de Jonge, J.W.E. Coenen and C. Okkerse, Selective hydrogenation of linolenate groups in soybean oil, Nature 206 (1965) 573–4. S. Koritala and H.J. Dutton, Selective hydrogenation of soybean oil. II. Copperchromium catalysts, J. Am. Oil Chem. Soc. 43 (1966) 556–8. J.W. King, R.L. Holliday, G.R. List and J.M. Snyder, Hydrogenation of vegetable oils using mixtures of supercritical carbon dioxide and hydrogen, J. Am. Oil Chem. Soc. 78 (2001) 107–13. M.-B. Macher and A. Holmqvist, Hydrogenation of palm oil in near-critical and supercritical propane, Eur. J. Lipid Sci. Technol. 103 (2001) 81–4. M. Härröd, S. Van den Hark, A. Holmqvist and P. Møller, Selective hydrogenation of triglycerides at supercritical single-phase conditions, Abstr. 3rd Euro. Fed. Lipid Congress, Edinburgh (2004), p. 85. N.-H. Schöön, Is a low trans content attainable by conventional hydrogenation of vegetable oils?, in Oils – Fats – Lipids 1995 (W.A.M. Castenmiller, ed.), P. J. Barnes & Associates, Bridgwater (1995), pp. 155–8. F. Zaera, unpublished results (2008). S. Koritala, Hydrogenation of unsaturated fatty esters with copper-chromite catalyst: kinetics, mechanism and isomerization, J. Am. Oil Chem. Soc. 47 (1970) 463–6. C. Okkerse, A. de Jonge, J.W.E. Coenen and A. Rozendaal, Selective hydrogenation of soybean oil in the presence of copper catalysts, J. Am. Oil Chem. Soc. 44 (1967) 152–6. R.T. Sleeter (to ADM Co.), Copper-chromium catalyzed hydrogenation of polyunsaturated oils, US Pat. Appl. 2003/0158433 A1 (21 Aug. 2003). J.W. Veldsink, M.J. Bouma, N.-H. Schöön and A.A.C.M. Beenackers, Heterogeneous hydrogenation of vegetable oils: a literature review, Catal. Rev. Sci. Engng. 39 (1997) 253–318. W.T. Koetsier, Hydrogenation of edible oils. Technology and applications, in

780

[64]

[65]

[66]

[67]

[68] [69] [70] [71] [72]

[73] [74] [75]

[76]

[77] [78]

[79] [80] [81]

[82]

Biodiesel science and technology Lipid Technologies and Applications (F.D. Gunstone and F.B. Padley, eds), Marcel Dekker, New York, NY (1997), pp. 265–303. W.E. Farr, Hydrogenation: processing technologies, in Bailey’s Industrial Oil and Fat Products, 6th edn, Vol. 5 (F. Shahidi, ed.), John Wiley & Sons, Inc., Hoboken, NJ (2005), pp. 385–96. B.R. Moser, M.J. Haas, J.K. Winkler, M.A. Jackson, S.V. Erhan and G.R. List, Evaluation of partially hydrogenated methyl esters of soybean oil, Proc. Intl. Congress on Biodiesel, Vienna (5–7 Nov. 2007). R. Kalscheuer, T. Stöveken, H. Luftmann, U. Malkus, R. Reichelt and A. Steinbüchel, Natural lipid biosynthesis in engineered Escherichia coli: jojoba oil-like wax esters and fatty acid butyl esters, Appl. Environm. Microbiol. 72 (2006) 1373–9. R. Kalscheuer, H. Luftmann and A. Steinbüchel, Synthesis of novel lipids in Saccharomyces cerevisiae by heterologous expression of an unspecified bacterial acyltransferase, Appl. Environm. Microbiol. 70 (2004) 7119–25. R. Kalscheuer, T. Stölting and A. Steinbüchel, Microdiesel: Escherichia coli engineered for fuel production, Microbiol. 152 (2006) 2529–36. F. Angulo, unpublished results (5 Nov. 2008). E. Archambault, Towards a Canadian R&D Strategy for Bioproducts and Bioprocesses, Science-Metrix, Montreal (Apr. 2004). W.K. Craig and D.W. Soveran, Production of hydrocarbons with a relatively high cetane rating, US Pat. 4,992,605 (12 Feb. 1991). J. Monnier, G. Tourigny, D.W. Soveran, A. Wong, E.N. Hogan and M. Stumborg (to National Resources Canada), Conversion of biomass feedstock to diesel fuel additive, US Pat. 5,705,722 (6 Jan. 1998). Alberta Renewable Diesel Demonstration (16 Dec. 2007–15 Apr. 2008; 16 Apr. 2008–30 Sept. 2008); cf. A. Austin, Biodiesel Mag. 6(4) (2009) 18. L. Rantanen, R. Linnaila, P. Aakko and T. Harju, NExBTL–biodiesel fuel of the second generation, SAE Techn. Paper 2005-01-3771 (2005). D. Rothe, J. Lorenz, R. Lämmermann, E. Jacobi, L. Rantanen and R. Linnaila, New BTL diesel reduces effectively emissions of a modern heavy-duty engine, Kolloquium ‘Fuels’ der Technischen Akademie Esslingen (TAE) (Jan. 2005). J. Jakkula, P. Aalto, V. Niemi, U. Kiiski, J. Nikkonen, S. Mikkonen and O. Piirainen (to Fortum Oyj), Diesel fuel composition, comprising components based on biological raw material, obtained by hydrogenating and decomposition of fatty acids, PCT Int. Publ. No. WO 2004/022674 A1 (18 Mar. 2004). M. Koskinen, M. Sourander and M. Nurminen, Apply a comprehensive approach to biofuels, Hydrocarb. Proc. 85 (2006) 81–6. Institute for Energy and Environmental Research, An Assessment of Energy and Greenhouse Gases of NExBTL from Rape Seed Oil and Palm Oil, IFEU, Heidelberg (2006). C. Hodge, What is the outlook for renewable diesel? Hydrocarb. Proc. (Feb. 2008) 85–92. M.P.A. Patajoki, Algae oil as potential feedstock for NExBTL renewable diesel, Presentation at Intl. Algae Congress, Amsterdam (3–4 Dec. 2008). J. Holmgren, C. Gosling, R. Marinangeli, T. Marker, G. Faraci and C. Perego, New developments in renewable fuels offer more choices, Hydrocarb. Proc. (2007) 67–8. J. Holmgren, C. Gosling, T. Marker, P. Kokayeff, G. Faraci and C. Perego, Green

Evolution of biodiesel and alternative diesel fuels

[83] [84] [85]

[86]

[87] [88]

[89] [90] [91] [92] [93]

[94] [95]

[96] [97] [98] [99] [100]

[ 101] [102]

[103]

781

diesel production from vegetable oil, Proc. AIChE Spring Natl. Mtg., Houston, TX (22–27 Apr. 2007). T. Kalnes, T. Marker and D.R. Shonnard, Green Diesel: a second-generation biofuel, Int. J. Chem. Reactor Engng. 5 (2007), Art. A48. Commission of the European Communities, Biomass Action Plan, Brussels (2005), COM/2005 628. European Environment Agency (EEA), How Much Biomass Can Europe Use Without Harming the Environment? Copenhagen (2005), EEA Briefing 02; http:// www.eea.eu.int. R.D. Perlack, L.L. Wright, A.F. Turhollow, R.L. Graham, B.J. Stokes and D.C. Erbach, Biomass as Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply, DOE/USDA Rept. DOEGO-102995-2135 and ORNL/TM 2005-66 (Apr. 2005). Sandia Corp., 90-Billion Gallon Biofuel Deployment Study, Albuquerque, NM (2009); http://HITECtransportation.org/news. M.E. Dry, The Fischer–Tropsch process: 1950–2000, Catal. Today 71 (2002) 227–41; Present and future applications of the Fischer–Tropsch process, Appl. Catal. A 276 (2004) 1–3. R. Jory, GTL fuel: driving the growth of the GTL market, Presentation at 23rd World Gas Conference, Amsterdam (5–9 June 2006). E. Henrich, N. Dahmen and E. Dinjus, Cost estimate for biofuel production via biosyncrude gasification, Biofuels Bioprod. Bioref. 3 (2009) 28–41. R.C. Christiansen, Aerospace industry continues biodiesel-related testing, Biodiesel Mag. 6(4) (2009) 20–21. T. Alleman and R. McCormick, Fischer–Tropsch diesel fuels – Properties and exhaust emissions: a literature review, SAE Techn. Paper 2003–01-0763 (2003). M. Rudloff, Biomass-to-liquid (BTL) from Carbo-V® process: technology and latest developments, Proc. 2nd World Conf. Techn. Exhib. Biomass for Energy, Industry and Climate Protection, Rome (10–14 May 2004), p. 1875. The Royal Society of Chemistry, Sustainable Biofuels: Prospects and Challenges, RSC, London (2008). K. Ståhl, L. Waldheim, M. Morris, U. Johnsson and L. Gårdmark, Biomass IGCC at Värnamo, Sweden – past and future, GCEP Energy Workshop, Stanford (27 Apr. 2004). R.M. Brown and D. Nobles Jr, unpublished results (2008). R. Rinaldi, R. Palkovits and F. Schüth, Depolymerization of cellulose using solid catalysts in ionic liquids, Angew. Chem. Intl. Ed. 47 (2008) 8047–50. D. Tilman, J. Hill and C. Lehman, Carbon-negative biofuels from low-input highdiversity grassland biomass, Science 314 (2006) 1598–600. http://www.amyrisbiotech.com/projects_biofuels.html. B. Kavalov and S.D. Peteves, Status and Perspectives of Biomass-to-Liquid Fuels in the European Union, EUR 21745 EN, European Commission, DirectorateGeneral Joint Research Centre, Institute for Energy, Petten (2005). http://www.refuel.eu/fileadmin/refuel/user/docs/REFUEL_final_road_map.pdf. E. Gray and A. Schmidt, Strategic assessment of bioenergy potential in the West, Western Governors’ Association Alternative Transportation Fuels Workshop, Denver, CO (10–12 Oct. 2007). D.J. Cuff and W.J. Young, US Energy Atlas, Free Press/Macmillan Publishing Co., New York, NY (1980).

782

Biodiesel science and technology

[104] S. Kartha and E.D. Larson, Bioenergy Primer: Modernised Biomass Energy for Sustainable Development, United Nations Development Programme (UNDP), New York, NY (2000). [105] A. Demirbaş, Global biofuels strategies, En. Educ. Sci. Technol. 17 (2006) 32–63. [106] European Renewable Energy Council, Renewable Energy Scenario 2040, EUREC Statistics, Brussels (2006).

16

Epilogue: outlook for biodiesel science and technology

Abstract: Biodiesel is now a reality but not a product without challenges: sustainable feedstock sources and regularity of supplies, fuel quality assurance, international quality standards, oxidative stability, energy policy and regulatory issues, taxation, production costs, overcapacity, utilisation of by-products, marketing, etc. The current state of the biodiesel industry is illustrated. First-generation batch biodiesel technology is transiting to continuous processing and second-generation technology heterogeneous catalysts are overtaking homogeneous catalysts; more advanced processing modes are gradually being introduced. Emerging feedstocks (e.g. jatropha, algae) are on the verge of partially replacing traditional foodstocks (rapeseed, soy, palm). Biodiesel production processes conform to ever more advanced green chemistry principles. Key words: Current state of biodiesel industry; future challenges; nextgeneration technology; foodstocks vs. feedstocks; biodiesel economy.

16.1

Introduction

Biodiesel has become a worldwide reality and constitutes a growth area. This chapter reflects current status and formulates forward-looking statements. Although we believe that the expectations reflected in these statements are reasonable, they involve risks and uncertainties. Future achievements may differ as to the schedule of development, technological problems, the impact on plant economics (including raw material prices, tax credits and energy prices), etc. Production-related biodiesel R & D issues (defined as an oxygenated diesel fuel made from vegetable oils and animal fats by conversion of triglycerides to esters via transesterification) include consideration of feedstocks (effective use of all available environmentally sustainable resources, including agricultural crops, waste oils and other underutilised biomaterials) and logistics. At the present time, research has concentrated mainly on biodiesel production from rapeseed (canola), soybean, sunflower and palm oils, used cooking oils and tallow, but other (local) options are open and are being pursued (specifically coconut, jatropha and algae). Nevertheless, vegetable oils will be unable to completely displace petroleum as a source of diesel fuel. Future aims in biodiesel fuel research are reduction of the production costs of plant oil by plant breeding, selection and biotechnology, and 783

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improvement in sustainable production technology. In particular, there needs to be improvement in bioproduct yield, price and performance compared to petroleum-derived products, and quality assurance at each stage of the production cycle. Processing-related R&D issues include further development of efficient and inexpensive conversion technologies, in particular improved catalytic and chemical conversion technologies. The low-temperature properties and stability of biodiesel fuel can be improved by additives and by genetic engineering of oil plants. Market-related issues include analysis of performance characteristics among various biodiesel feedstocks and market development for co-products.

16.2

State of the biodiesel industry

The current state of the biodiesel industry is best illustrated by the following statements: ∑

∑ ∑ ∑

∑ ∑ ∑ ∑ ∑ ∑ ∑

Commercial processes for converting vegetable oils and animal fats to biodiesel are not for the most part cost-competitive with current petroleum-based diesel fuel production methods except with favourable fiscal policies and tax incentives. At present, economic problems for biodiesel are greater than agronomic and technological ones. Global market conditions for the biodiesel industry 2010 are generally unfavourable (survival-of-the fittest scenario). The subsidised use of vegetable oils for bioenergy and biofuel production is completely contradictory to their established use in nutrition and to future industrial developments of high value-added oleochemical-based products. Biodiesel is not merely a question of subsidies, set-aside areas or last aid to farmers. It is a serious mistake to consider biodiesel merely as a clean energy myth. Biodiesel contributes to providing a solution to some of the most pressing global resource and environmental problems. Biofuels are not a panacea for climate change. The overall life cycle analysis of greenhouse gas (GHG) emissions for biofuels made the right way from a responsible source is more favourable than for oil-derived fuels. Sustainable biodiesel for transport contributes to ensuring ‘energy security’ and in appropriate conditions fits into a low-carbon economy. Carbon emissions can be minimised throughout the life cycle of bioenergy production by application of sound science and engineering, agricultural best practice, maximising the use of biomass co-products (either for chemical or energy production) and by minimising transportation.

Epilogue: outlook for biodiesel science and technology

∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

∑ ∑ ∑

∑ ∑ ∑ ∑ ∑ ∑

785

Otherwise, reforestation of fallow lands gives a greater contribution to CO2 abatement than use for biodiesel production. Biodiesel is consolidating its position of first biofuel produced in the EU and is the fastest growing alternative fuel in the US today (though mainly for export purposes). The US biodiesel market should not be based on exports. A domestic US biodiesel market could be stimulated through mandatory blending. Growing biodiesel as the cure for petroleum addiction is unrealistic hype. Biodiesel and petrodiesel are complementary rather than competing products. The break-even point of biodiesel cost with respect to petrodiesel is a moving target as the prices of vegetable oils and crude oil are highly correlated. In the short and long term, biodiesel will only be able to make a modest contribution to the diesel pool; biodiesel production is as yet a minor fraction (< 1 %) only of the overall world consumption of petrodiesel. At present the best alternative to petrodiesel as an automotive fuel is biodiesel, a very versatile transport fuel which does not require infrastructural changes and can be used in existing diesel engines with no modification. Biodiesel also classifies as an economically viable energy source in remote areas. On the assumption that no new oil refineries will be built in Europe in the short term, the resulting fossil diesel fuel scarcity will increasingly be offset by biodiesel (first and second generation). Biodiesel production projections remain highly speculative but in the medium term a considerable increase might be expected due to concerns about energy independence and a growing demand (9–15%) for fuels from renewable sources. For an evaluation of the attainable biodiesel production it is necessary to use realistic estimates of available raw materials. Best-case estimates indicate a future maximum fossil diesel replacement by biodiesel based on edible and non-edible vegetable oils (using current agricultural practices) and animal fats of about 10%. Excessive expectations of biodiesel have been tempered. The market potential of biodiesel originating from currently available agricultural feedstock is limited because of tight supply base and very high production costs. There is more capacity than feedstock availability in the biodiesel industry. Biofuels are attracting criticism due to inefficient production methods and the increase in food prices.

786

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Biodiesel science and technology

The key to biodiesel is not technology but feedstock availability. Biodiesel can be made anywhere oilseed crops are grown or used cooking oil is being produced. Cultivation of current energy crops (mainly soy, rape, palm, sunflower and coconut) is geographically and (partly) seasonably restricted; therefore, biodiesel is a seasonal activity. EU production of oilseeds does not follow the increase of biodiesel production and domestic demand. New feedstock oilseeds for biodiesel are being considered in countries beyond their origin (e.g. palm oil in Europe), implying importation. Biodiesel from current total oilseed production is lame. The impact of large-scale farming for biofuels depends on what is grown. Biodiesel depends nowadays greatly on dangerous monocultures. Not all biodiesel is created equal; some types are more sustainable than others. Biodiesel is not a fungible product. The sustainability of crops used for biofuel production needs to consider competition for land and usage of biomass, intensity of cultivation, crop rotation and use of water and pesticides. Each feedstock has its own ecological footprint. Mass production of vegetable oils with indiscriminate use of pesticides and water damages the environment. Broader use of biodiesel is hampered by the extensive acreage required for sufficient production of oilseed crops. Use of biofuels as transport fuels is especially interesting for countries lacking crude oil resources, but with sufficient arable land to reduce their dependence on oil imports. Biodiesel is best as a regional solution to a global energy crisis. Until 2005 biodiesel was conceived largely in the context of local agroclimatic conditions or national fuel needs, but is now emerging as a global industry. Similarly, agricultural lipids are recently globally traded as significant energy commodities rather than as conventional soft food commodities. Demand for biofuels is absolutely essential to ensure remunerative prices for edible oils. Biodiesel needs more feedstock, less foodstock. Non-food feedstocks are not yet playing a vital role in the biodiesel industry. Biodiesel offers long-term sustainable domestic liquid-fuel production in many countries. Given the different climatological conditions globally, it is not possible to define an ‘ideal biodiesel’ composition; consequently, there is no ideal fatty acid profile for a biodiesel feedstock.

Epilogue: outlook for biodiesel science and technology

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787

No universal crop or process exists for biodiesel production. No single feedstock or technology will be sufficient to satisfy the enormous demand for liquid fuels. A wide range in suitable fatty acid profiles is important in relation to the flexibility in multi-feedstock supply for biodiesel production. The source of biodiesel is determined mainly by the predominant climate and infrastructure as well as by local political priorities. Feedstock represents the main factor (80%) for cost evaluation of biodiesel. Cost reduction potential of biodiesel processing from virgin triglycerides is very limited. Return-on-investment (ROI) is better for biodiesel plants based on unrefined multi-feedstocks than on refined vegetable oils. The contribution of used frying oils to total biodiesel production is necessarily small and limited by the use of virgin origin oils for cooking. Other waste materials as biodiesel feedstock (e.g. TLW) are similarly only available in restricted quantities, limiting biodiesel production capacity. The need for alternative uses of animal-derived fats and the development of new technology to convert cheap feedstocks such as yellow and brown grease make biodiesel production economically more attractive. Use of waste products requires higher investment costs and more robust catalysts. Vegetable oils containing unusual fatty acids in economically profitable quantities should preferably be used for oleochemical rather than fuel purposes. The cost of biomass transport determines the supply area of a biodiesel processing facility and thus its scale and economics. Producing biofuels is carbon neutral provided feedstock production is sustainable and transportation is minimised. Biodiesel performs best in a dedicated market close to the producer. Industrial-scale biodiesel production is primarily geographically and seasonably of interest (but not exclusively restricted) to oilseed producing areas. Import of biodiesel (feedstocks) is recommended only for countries without adequate local vegetable oil resources (e.g. Japan, Northern Europe). There are no technical hindrances for manufacturing biodiesel using common feedstocks. Biodiesel technologies need to be sufficiently robust to accommodate a diversity of needs around the globe. The biodiesel industry is slowly maturing and shifting from construction

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Biodiesel science and technology

and growth to consolidation, operation (and modification) of existing plants. For cost reasons, it is useful to employ improved continuous processing technologies rather than batchwise processing and to replace current homogeneous by heterogeneous catalysts. The potential of solid acid-catalysed transesterification of triglycerides requires more attention. Economically viable processes for biodiesel production, which can compete commercially with petroleum-based diesel fuel, ideally need to use robust heterogeneous catalysts which can tolerate higher levels of impurities, are effective for a broad range of reactants, have few reaction steps and a limited number of separation steps. Molecular plant genetics is important in supporting raw material supply. Very few plants produce the desirable short-chain triglycerides (SCT) tricaprin (C10:0), tricaprylin (C8:0) and tricaproin (C6:0) in industrially interesting quantities. Food, fuel and forest compete for use of biomass resources. Jatropha and algal oils are considered as the most promising and sustainable biodiesel feedstocks of the medium- to long-term future, respectively. Biofuels from algae are pre-commercial. Microalgae appear to be the only source of biodiesel capable of meeting the global demand for transport fuels with the potential of completely displacing fossil diesel in the foreseeable future without impacting on the food market. Microalgae do not compete for land like other energy crops. Using microalgae to produce biodiesel will not compromise production of food, fodder and other crop-derived products. Algal biodiesel technology provides a means for recycling waste carbon from fossil fuel combustion. Current (commercial) biodiesel technology from refined anhydrous oils is based mainly on alkaline catalysis; unrefined oils (CCNO, CPO, CPKO, CSO, SBO) and animal oils and fats (BTW, lard, fish oil) require preesterification (acid catalysis) followed by alkaline transesterification. Transesterification employing strong soluble acid and base catalysts is incompatible with modern synthetic industrial chemistry that desires to be highly efficient, selective, ecofriendly and preferably catalytic. Biocatalysis by immobilised lipases is as yet an immature and expensive technology to produce biodiesel. First-generation transesterified biodiesel (FAME) is not a truly renewable product since the alcohol component is of fossil origin (see Table 16.2). Green synthetic diesel products such as hydrotreated vegetable oil

Epilogue: outlook for biodiesel science and technology

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789

(HVO) are serious competitors to biodiesel (FAME) using the same feedstock. On the basis of green chemistry principles, synthetic diesel processing ranks in the order HVO, microbial FAEE > heterogeneous transesterification (e.g. Esterfip-HTM) > conventional base-catalysed transesterification (e.g. Esterfip). Using wastes and residue feedstocks for biodiesel production results in higher environmental benefits; the challenge here lies mainly in the high cost of collection and transport (logistics). High reaction yields, reduction in feedstock costs and security of supply are all important in terms of profitability of a biodiesel enterprise. While the science behind the use of oil and fat sources for energy supply as biodiesel is maturing fast, the technology for being economically competitive with fossil fuels has recently been improved by alternative value-added use of a co-product (glycerol). The cost of producing biodiesel can further be reduced substantially with technological advancements making use of all biomass components (biorefinery concept). In the medium term biodiesel can sustain the automotive transportation sector but does not represent the ultimate structural answer to increasing market needs. Bio-based diesel production is not restricted to oilseed producing regions of the world, in contrast to conventional FAME-based biodiesel. A biofuel backlash is in full swing as a result of a rush to agricultural crops with consequent high feedstock prices, rising food prices and suspicious farming and blending subsidies.

16.3

Challenges for the global biodiesel industry

After rapid growth in the past few years, the global biodiesel industry is now facing a number of important challenges (Table 16.1), which will be influential to the future. Biodiesel markets in 2008–09 are characterised by high turbulence. Some short- and long-term challenges for biodiesel producers are common to the whole industry, while others are more regionally specific. The highly competitive biodiesel industry is transiting to alternative feedstocks, emerging technologies, and revised government policies favouring sustainable feedstocks and fuels. There is a need to improve cost efficiencies in new technologies, to improve logistics and infrastructure, and to encourage effective collaboration with automotive and agricultural industries. Advanced feedstock production technologies are being pursued, including use of crop selection optimisation, growing of dedicated energy crops such as jatropha on marginal lands, and eventually use of algae-based oils which do not compete for fresh water or farm land. Until these more efficient modes

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Biodiesel science and technology Table 16.1 Challenges to the biodiesel industry ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑ ∑

Sustainability Cost efficiency Feedstock sources and supply Energy policy/regulatory issues Social and environmental impact Manufacturing technologies Next-generation biodiesel Biodiesel fuel quality International quality standards Industrial and customer acceptance/awareness Production capacity Marketing Utilisation of by-products Plant economics Financial crisis 2008 

of crop production become commercialised, the ad hoc nature of current biodiesel growth will eventually impact global food supplies and long-term sustainability of agricultural production. With the possibility of large gains in crop yields alone, it may be possible to significantly increase biodiesel production without requiring additional land or sacrificing food supply. A successful biodiesel economy depends on a number of factors as detailed below.

16.3.1 Sustainability Sustainable food, energy and waste are competing priorities. A common platform for sustainable agriculture and responsible energy is needed. A standard definition of energy balance is required to allow comparisons. Biofuels can never be made entirely risk free, but the risk can be reduced by developing and introducing credible sustainability criteria as soon as possible. A consistent and transparent sustainability certification scheme for biodiesel is necessary to maintain confidence in its performance from environmental and social perspectives. Biofuels production has caused various social and environmental problems but biodiesel can be and should be produced in a sustainable way. The use of non-sustainable agricultural practices worldwide in biodiesel production should be discouraged. Intensive, large-scale cultivation of biofuel crops requires adequate domestication to a point of human/animal safety. Energy crops (such as palm tree) should be cultivated in a responsible way. Intensive single-crop farming for fuel (e.g. US corn for bioethanol) is environmentally unsustainable. Water efficiency is becoming ever more important. Justifying biodiesel as a superior fuel requires looking at the entire environmental

Epilogue: outlook for biodiesel science and technology

791

impact including use of scarce land and water resources, effects on sensitive ecosystems and biodiversity, air pollution and emissions (in particular CO2 and NOx). Real GHG benefits over the entire life cycle (now still controversial) should finally be proven. Deforestation and land erosion for oilseed crops (by slash-and-burn agriculture) should be avoided. Sustainability needs to take into account all potential impacts of biofuel processes, including the effects on deforestation, environmental degradation, soil quality, fuel security, competition with food production, import trade and costs of distribution. Meanwhile, modern plant breeding techniques and biotechnology can increase the productivity of currently cultivated land. Legitimate concerns about sustainability should not derail the biodiesel enterprise. Lessons learned from sustainable biofuel production could profitably also be extended to food production. Biodiesel made from recycled resources, such as waste cooking oil, is extremely sustainable and far better for the planet than petroleum and even some other types of biofuels.

16.3.2 Feedstock sources and supply Availability of economical feedstock, feedstock flexibility and security are essential. Globally, though not regionally, supplies are insufficient for domestic biodiesel production. Strong partnership with the vegetable oil industry (preferably with on-site crushing facilities) is critical to producer survival. No one feedstock provides the ultimate solution to the biodiesel industry’s challenges. A diverse portfolio of agricultural products for biodiesel is needed. Diversification of the feedstock basis is an ambitious goal. There are rising demands for lower-cost feedstocks (used vegetable oils, tallow), posing collection problems. The use of human food/animal feed for production of biodiesel is a short-term solution only. Investment in exploration and cultivation of alternative, large-volume, high-yield, nonfood, non-rainforest-based lipid feedstocks (e.g. jatropha, pongamia, algae) is required. Development of additional feedstock sources with relatively low input requirements (e.g. crops growing in a dryland farming setting) is much needed as well as recultivation of degraded land, waste land and white deserts by oil-bearing plants. The answer to the supply problem, crucial for the success of the biodiesel strategy, is more beans, more means, change genes. Transgenics are imperative for biofuel crops. It is important to use green gene technology for developing better energy plants. Increased adoption of hybrids, high-yielding genetics, new traits and improved production practices will create more value through higher yields and better stress tolerance. Obvious approaches to easing the supply response are dramatic improvements in agricultural (oilseed) yields and oil content of conventional crops, introduction of additional crops into crop rotation schemes and/or increasing the acreage of land farmed. Increasing inter-crop competition

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for acreage has recently been observed, notably in the US. Increased crop yields are of particular importance because they affect the amount of land needed to meet food, feed and fibre demands. Short-term development is desired for oilseed crops having desirable agronomic traits (e.g. mustard, crambe, cardoon, camelina, moringa, Lesquerella and Cuphea). Innovative plant design via accelerated plant domestication programmes is required for a sustainable biomass production; in particular, greater domestication efforts should be directed to perennial species as a renewable feedstock for conversion of fuels. Additional measures needed include lowering the input costs of cultivation, increase in seed oil content with concomitant reduction of seed protein, and increase in protein value. Protein engineering should contribute in optimisation of specific enzymes in oil biosynthesis. A step-change in the (modest) yield of plant oil per hectare is necessary in order to satisfy the demand from the emerging biodiesel sector. More attention should be paid to oil in leaves of plants. Potentially, microalgae provide such a step-change solution in lipid feedstock supply. Renewable algae diesel has high potential. Knowledge of the metabolism of high oilproducing algae, their processing technology and technical potential deserve further development. Bioengineering microalgae constitutes a promising route to biodiesel production. Development of advanced biofuels by the chemical industry by increased use of oils and fats as renewable raw materials requires a multidisciplinary effort involving chemists, biologists, biotechnologists, agronomists, plant breeders, chemical engineers, fuel specialists and social scientists. Long-term strategies can be approached by a combination of traditional breeding, genetic engineering (quality and quantity of fatty acids exhibiting a combination of improved fuel properties) and materials science. Biotechnologies are vital in addressing the growing demand for fuel. Thorough working knowledge is required of oil biosynthesis in plants that produce high amounts of industrially important fatty acids in order to elucidate metabolic mechanisms and identify genetic tools for oil production. Detailed characterisation of genomic, proteomic, metabolic, cellular and regulatory aspects of oil production is needed. Application of biotechnology may enhance agronomic traits such as seed yield, oil content, disease resistance, and pod shatter that currently limit wider use of many plants. Further breeding programmes and continued improvement of selected plant germplasm are wanted. Industrial biotechnology (biocatalysis, bioprocessing, fermentation technology, in combination with molecular genetics and metabolic engineering) will revolutionise the production of industrial chemicals from biomass in the 21st century. Sufficient focus on the production of biomass and improved agro-forestry management may cover the global energy provision from biomass. Available land, potential environmental degradation, habitat destruction,

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and competition with food production are the major limitations for biofuels. Conflicting demand for vegetable oil commodities between food, bioenergy and chemicals development raises both ethical questions and practical problems, requires critical consideration, and anyhow is currently causing a biodiesel backlash. Technology whereby (scarce) food crops are converted into biofuels has a serious impact on global food supplies and has (partly) caused the high spot market prices. Use of edible feedstock, including palm oil, for biodiesel production is just a transition phase of the industry. Biodiesel focus should change from foodstock to (non-edible) feedstock. Non-food source feedstocks for biodiesel will make foodstocks for biodiesel less needed. However, cultivation of non-food oil crops is not a panacea for biofuels. It is noticeable that some alternative diesels developed by the petro industry, such as hydrodiesel, are currently based on the same renewable natural lipid feedstocks as biodiesel, thus increasing feedstock rivalry. Increasing prices and environmental consciousness are thus rendering alternatives to conventional fuels even more interesting and pressing. The best sources of biodiesel are waste (waste vegetable oils) and other rotational crops (such as mustard) and non-foodstock oils. In the future, both biodiesel and hydrodiesel could benefit from the availability of highly unsaturated algal oil using (selective) hydrogenation processes. Next-generation biodiesel needs to be feedstock rather than foodstock based.

16.3.3 Energy policy/regulatory issues Energy is the only crop that never grows in surplus. Growth in demand for energy will accelerate. Concerning national energy security, military assets are not required to protect domestic biomass, as opposed to oil supply lines. While biofuels are nowadays popular in helping countries to achieve energy targets, concerns over the environmental impacts of dedicating yet more land to agriculture mean that other (older) technologies need to be investigated as well in order to mature and realise fully their initial potential. To meet the increasing energy needs, development of a broad spectrum of renewables is required. Energy conservation and development of renewable energy sources, such as lower cost solar cells with higher efficiencies, should have high priority. Without legislation in place, the biodiesel industry is not feasible. Almost all 52 US states and 27 EU member states have implemented (or are implementing) federal or EU biofuel directives, legal measures and (voluntary) regulations, though frequently in different ways. Harmonisation is much required here. Europe needs an EU-wide tax policy; the US needs increasing mandates on biodiesel. Governments need to proactively support development of sustainable, alternative, lower-cost feedstocks (algae, jatropha,

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castor, UCO, TLW) and next-generation technologies (renewable diesel, BTL, cellulosic diesel). Shifting government policies towards biodiesel have recently been observed and are urgently required to eliminate devastating distortions, such as the US dumping competition in B99 blends. Splash-and-dash biodiesel is partly responsible for the present decline of Europe’s biodiesel production. The EU–US trade conflict is not in the interest of the global biodiesel industry. Once each country keeps their biofuels incentives strictly within their borders, applies their own incentives and bases them on the local sale of biodiesel, the product will once again become a regional solution to a global crisis. Legislative priorities should ensure undistorted market competition between Big Oil (subsidised by war and Arab tribute) and Big Agriculture (opening up markets for biofuels to outcompete imported crude oil). Consumers are frequently being denied alternative choices at the pump with sound public policy that calls for unbiased market competition. The growth in biofuels is being driven primarily by government mandates rather than by market forces. The industry needs sound government support until biodiesel can compete economically with petroleum fuels. Energy systems which do not pay for themselves over the medium to long term are not sustainable; market interventions (for example, subsidies or taxes) should be needed only in the short term to achieve essential goals. Improvements in energy efficiency are needed to reduce individual energy needs. An energy policy is only as good as its execution.

16.3.4 Manufacturing technologies The main technological thrust of first-generation biodiesel is transitioning (trans)esterification technology from traditional batch methodology to a continuous process in larger facilities. A considerable challenge for biodiesel is plant scale. Biomass collection makes the size of petrodiesel plants unattainable. The right choice of technology provider in connection with the prospective feedstock use is also very important. Production technology should always lead to the same quality standard, independent of the oils or fats used. Highly flexible multi-feedstock use (including non-food high-energy oils) at the highest yield levels is a technological challenge. More systematic research is wanted on solid-catalyst activity for transesterification of TGs and esterification of FFAs with alcohols. More effective and cheaper manufacturing technologies are welcome; exchange of practical biodiesel experience is precious. Breakthroughs are needed for application of lipase catalysis to unrefined oils. Table 16.2 illustrates the relation between biodiesel production and green chemistry principles. Biodiesel from vegetable oils is not a completely renewable product.

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Table 16.2 Green chemistry and biodiesel production Green chemistry principles

Biodiesel synthesis practice

∑ Prevention of waste

Glycerol as by-product; wastewater; salt formation (fertilisers) Low excess chemicals (recoverable) Simple chemistry; low cost Potentially safe reagents and products; environmentally friendly (see Table 14.6); no VOCs; low toxicity Toxic methanol; co-solvents; wastewater High T, p in non-catalytic processes Edible and non-edible vegetable oils and animal fats; used oils/fats Pre-treatment Wide choice of catalysts and feedstocks; corrosiveness of some catalyst classes Diesel engine compatible product International standards; no hazardous substances Inherently safe chemistry (low T, p) for accident prevention

∑ Atom economy ∑ Chemistry ∑ Environmental impact ∑ Safe solvents and auxiliaries ∑ Energy efficiency ∑ Use of renewable feedstocks ∑ Reduced chemical derivatisations ∑ Catalysis ∑ ∑ ∑

Design for degradation Real-time analysis for pollution prevention Industrial application

While first-generation biofuels are essentially resource-based, the next generations will be mainly technology based. Renewable diesel fuel (e.g. HVO) is an emerging technological threat for first-generation biodiesel and could eventually seize a large slice of its market. Co-generation of biofuels is possible. A broader use of synthetic diesel will be possible if production processes are developed that are not based solely on oilseeds but on cheap and readily available renewable bulk plant materials such as sugars, starch, cellulosic and waste materials. Given their positive environmental assessment, biofuels from residues should be realised if technically and economically viable. Biomass is expected to contribute significantly to renewable energy but at present the efficiency of integral biomass conversion is very limited and technologies are still evolving. Next-generation renewable diesel from biomass cellulose requires at least another decade before full commercialisation. Oleaginous biomass-based renewable fuel production may profitably be integrated in a refinery environment. In the medium to long term, BTL fuel production will become more attractive than biodiesel from (non)edible vegetable oil sources.

16.3.5 Biodiesel fuel quality The very small and fragmented biodiesel industry produces different grades of quality. The biodiesel industry faces an unfavourable quality control history. Priorities are: replacement of splash blending by in-line blending,

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OEM acceptance of biodiesel blends, and quality updates, including continued refinement of ASTM specifications for biodiesel. Current specifications, which are not globally uniform, are hindering the market. Specifications need to be revisited and biodiesel quality standards are to be harmonised worldwide to facilitate global trading of biodiesel and diesel vehicles. There exists an urgent need for creation of an ISO biofuels technical committee. Quality assurance at the highest level has to be addressed given the tremendous diversity of feedstocks and manufacturing practices in use today. Certified quality production is essential. Good product quality control concerns, in particular, two main technical barriers: oxidative stability and other degradation phenomena in summer and cold-flow properties (CFPs) in winter. Storage should be minimised and logistics improved. Different feedstocks yield different biodiesel fuels. Alternative feedstocks have an impact on CFPs (e.g. biodiesel from palm oil, tallow or used cooking oils vs. refined soy and rape biodiesel). Improving cold-weather performance to broaden use of biodiesel requires significant research efforts to develop additives or other technologies that can costeffectively correct biodiesel and its blends.

16.3.6 Industrial and customer acceptance/awareness Fuel quality, OEM acceptance and governmental support are key to production and encouraging consumers to use biodiesel. Quality is absolutely essential for public acceptance. Biodiesel development cannot do without numerous diesel engine manufacturers (OEMs) guaranteeing their own engines (warranties), and integration into the existing blending and diesel infrastructure of the petrochemical industry. Optimising engine design might allow greater flexibility in fuel use, up to opening new horizons for the direct use of native vegetable oils. One of the biggest hurdles in the promotion of renewable fuel use is the lack of available infrastructure (renewable fuel pumps, FFVs). Biodiesel’s perceived social value drives its consumer acceptance and demand. Biodiesel is subject to increased scrutiny from political and consumer groups (public opinion). Lack of quality and the recent hyperinflation and increasing food/fuel competition have contributed to a damaged reputation for biodiesel and biofuels in general. As people have a general feeling of deliberately being misled about the benefits of supposedly green fuels, the industry is reaping what it sowed. It has even become fashionable to blame biofuels for all the problems of mankind.

16.3.7 Production capacity With the recent increase in biodiesel production capacities worldwide, and quite a few large-scale plants, full capacity is no longer assured; in fact, an

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economically unsustainable overcapacity has developed in some countries that will get worse in 2009 (expectations of up to 40%). The underutilised biodiesel capacity worldwide needs to be put back to work. Use of modular units will likely expand.

16.3.8 Marketing Marketing calls for positive campaigning and optimisation of diesel fuel market segments. The biodiesel industry would benefit from increased demand for the product. Biodiesel has recently developed from a local and national product to a globally traded commodity. Production of biodiesel from imported feedstock is now a reality. As more markets are opening up worldwide, improvement of global trade flows of both feedstock and product is required. In this respect, approval of GM varieties for import of oilseeds into Europe is wanted. However, in essence imports of renewable feedstocks to increase availability run counter to the goals of being cost effective and using alternative fuels for increasing energy independence. Because government support is still necessary, the biodiesel industry is developing at a national level, with various protectionist approaches. Meanwhile, production has outpaced demand (boom and bust), in particular in the US and Argentina. The sizeable, subsidised US exports of B99 biodiesel to Europe are not healthy for US and EU taxpayers alike, and is also not in the best interest of the global biodiesel industry. Market fundamentals are camouflaged by biodiesel subsidies.

16.3.9 Utilisation of by-products New markets with value-added industrial use for co-products obtained from plants producing industrial oils, such as seed cake, need to be developed (white biotechnology applications) and further alternative uses for glycerol (glycerol-derivative chemistry) from biodiesel production need to be defined in order to ensure economic operation. New biodiesel processes are wanted which can produce high-purity glycerol. Excess market supply of glycerol could set the biodiesel industry backwards. Obviously, the glycerol problem is resolved as long as vegetable oil prices exceed biodiesel value. Growing energy crops should aim at using all biomass co-products for various purposes (food, feed, fuel, fine chemistry). Jatropha appears to be exemplary (see Table 5.29).

16.3.10 Process economics A critical issue in biodiesel production is economic viability. It is crucial for any biodiesel project to develop relationships with potential stakeholders,

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partners, suppliers, crushers, clients, potential funders and government agencies, to make a project feasible. In the capricious financial climate of 2008–09 the outlook for biodiesel is considerably different from that in 2006. In these times of economic downturn the biodiesel market is confronted with uncertainty and volatility seldom seen before. The biodiesel industry needs to be rebalanced. At present, the most destabilising factors facing the biodiesel industry are rising costs, higher taxes and cheap imports (into Europe). Diesel prices are high but vegetable oil prices are even higher. The economics of the inordinately high feedstock prices (resulting from Asian food oil demands, low commodity stocks due to global weather conditions and increased energy and transportation costs, market speculation and the weak dollar), which cause shrinking margins, is now holding the industry back globally. The current vegetable oil price rises make unsubsidised biodiesel production unviable in most countries. Activity continues in biodiesel development, although primarily in smaller plants. With an over-expanding domestic and global biodiesel production capacity, numerous idle plants and failed biodiesel ventures have been noticed recently in Europe and the US. Nevertheless, the final aim is competitive pricing with petroleum diesel without tax incentives. Production of sustainable biodiesel as cost efficient as petroleum processes requires economy of scale and adequate logistics. Mankind is pressed to develop an adequate ‘food plus biofuels’ scenario.

Appendix I

Acronyms/abbreviations of techniques

AAS AES AgLC AMS ANN APCI-MS

Atomic absorption spectrometry Atomic emission spectrometry Silver-phase LC Accelerator mass spectrometry Artificial neural network Atmospheric pressure chemical ionisation-mass spectrometry ASE Accelerated solvent extraction ATR Attenuated total reflectance BOCLE Ball-on-cylinder lubricity evaluator CGC Capillary gas chromatography CHR Chromatographic separator COC Cool on-column CSF Cold soak filter CSFT Cold soak filtration test CVCA Constant-volume combustion apparatus EIS Electrochemical impedance spectroscopy ELSD Evaporative light scattering detector EP-NIR Encoded photometric near-infrared ESI Electrospray FAAS Flame atomic absorption spectrometry FID Flame ionisation detector FP Full-pressing FTIR, FT-IR Fourier transform infrared FT-NIR Fourier transform near-infrared GC Gas chromatography GPC Gel permeation chromatography (cf. SEC) HFRR High-frequency reciprocating rig HPLC High-performance liquid chromatography HS-GC Headspace gas chromatography HSLC High-speed liquid chromatography HT High temperature HTGC High-temperature gas chromatography IC Ion chromatography ICP Inductively coupled plasma IEX Ion-exchange column IQTTM Ignition quality tester 799

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Biodiesel science and technology

KF(T) LSC LTFT MS NIR NIRS NITS NMR OES PAD PCA PCR PDA PDSC PLS PP/SE PSA PTV QMS RPLC SCD SEC SFC SFE TLC TPI UPLC US USAET UV UVF VFA VIS WDXRF XRF

Karl Fischer (titration) Liquid scintillation counting Low-temperature flow test Mass spectrometry Near infrared Near-infrared reflectance spectroscopy Near-infrared transmission spectroscopy Nuclear magnetic resonance Optical emission spectrometry Pulsed amperometric detection Principal component analysis Principal component regression Photodiode array Pressurised differential scanning calorimetry Partial least squares Pre-pressing/solvent extraction Pressure swing adsorption technology Programmable temperature vaporiser Quadrupole mass spectrometry Reversed-phase liquid chromatography Sulphur chemiluminescence detector Size-exclusion chromatography Supercritical fluid chromatography Supercritical fluid extraction Thin-layer chromatography Temperature-programmable inlet Ultra performance liquid chromatography Ultrasonication Ultrasonically assisted extraction transesterification Ultraviolet Ultraviolet-fluorescence Variable filter array Visible Wavelength dispersive X-ray fluorescence X-ray fluorescence

Appendix II

(Bio)chemical nomenclature

AAT ABE ACCase ACP ACR ACS ADH, AdhB AEOE AET AN AO APR AT ATP ATRP AV AVSO BCO BDF BHD BHT BKF BMA BMI BMIMCl BMT BMZ BSA BTE BTL BTME BTW CAS CCI CCNO

Alcohol acyltransferase Activated bleaching earth Acetyl Co-A carboxylase Acyl carrier protein (1) Aqueous-phase carbohydrate reforming; (2) Acrolein Acyl Co-A synthase Alcohol dehydrogenase Aqueous enzymatic oil extraction Atmospheric equivalent temperature Acid number Antioxidant Aqueous-phase reforming Acyl transferase Adenine triphosphate Atom transfer radical polymerisation Acid value Aloe vera seed oil Bio-crude oil Biodiesel fuel Bio-hydrogenerated diesel Butylated hydroxytoluene 2,2’-Bis(6-t-butyl-p-cresyl)methane (Antioxidant BKF, Bayer) Base-modified alumina 1-Butyl-3-methylimidazole 1-Butyl-3-methyl-imidazolium chloride Base-modified titania Base-modified zirconia Benzene sulphonic acid Bay thioesterase Biomass-to-liquids Beef tallow methyl ester Beef tallow Castor bean oil Calculated cetane index Crude coconut oil 801

802

Biodiesel science and technology

CCS CD CF CFI CFP CFPP CHT CI CJO CLA CLO CME CMFO CN CNG CNME CNO CO Co-A COME CP CPKO CPO CPOo CPOs CPT CRBO CRO CSO CSTR CTER CTL CTO DAG DAGAT DBG DCAS DDG(S) DEG DF DF2 DG

Carbon capture and storage Continuous deglycerolisation Continuous flow Cold-flow improver Cold-flow properties Cold-filter plugging point Calcined hydrotalcite Cetane index Crude jojoba oil Conjugated linoleic acids Cod liver oil Canola methyl ester Crude meadowfoam oil Cetane number Compressed natural gas Coconut methyl ester Coconut oil Canola oil Coenzyme A Curcas oil methyl ester (1) Cloud point; (2) Chemically pure Crude palm kernel oil (1) Crude palm oil; (2) Catalytic partial oxidation Crude palm olein Crude palm stearin Cytidine diphosphate-choline: 1,2-diacylglycerol cholinephosphotransferase Crude rice bran oil Corn oil Cottonseed oil Continuous stirred-tank reactor Continuous trans-esterification reactor Coal-to-liquids Crude tall oil Diacylglycerol 1,2-Diacylglycerol: acyl-CoA acyltransferase Dibutoxyglycerol Dehydrated castor oil Distillers dry grains (with solubles) Diethylene glycol Diesel fuel No. 2 petrodiesel fuel Diglyceride

(Bio)chemical nomenclature

DHA DHT DJO DMC DME DMF DMSO DOC DPF EATPP ECH EFA EG EI EPA ER ETBE EV EVA FA FAAE FABE FAC FAD FAE FAEE FAIE FAME FAR FAS FAT FFA FFAE FO FOG F-T, FT GCO GHG GL GLA GLYAC GLYALD GSO

(1) Docosahexaenoic acid; (2) Dihydroxyacetone Diesel hydrotreater Deodorised jojoba oil Dual metal catalyst Dimethylether 2,5-Dimethylfuran Dimethylsulphoxide De-oiled cake Diesel particulate filter Enzyme-assisted three-phase partitioning Epichlorohydrin Epoxy fatty acid Ethylene glycol Enal isomerase Eicosapentaenoic acid Endoplasmic reticulum Ethyl tert-butyl ether Ester value Ethylene-vinyl acetate copolymer Fatty acid Fatty acid alkyl ester Fatty acid butyl ester Fatty acid composition Fatty acid distillate Fatty acid elongase Fatty acid ethyl ester Fatty acid isoamyl ester Fatty acid methyl ester Acyl-CoA reductase Fatty acid synthase Fatty acid thioesterase Free fatty acid Free fatty acid ester Fish oil Fat, oil and grease Fischer–Tropsch Greenseed canola oil Greenhouse gas Glycerol Gamma linolenic acid Glyceric acid Glyceraldehyde Grapeseed oil

803

804

Biodiesel science and technology

GTB GTBE GTL G3P G3PAT HA HAPS HC HDO HDRD HDS HE HEA HEAR HEBC HERO HFA HLCO HMF HO HOSFO HOSNO HPA 3-HPA HPL HPO Hpy HPYAC HT HTU HV HVO HZ IE ILB IS IV JCO JO JP KAS KCS KME

Glyceryl tributyrate Glyceryl-tert-butyl ether Gas-to-liquids Glycerol 3-phosphate Glycerol 3-phosphate: acyl-CoA acyltransferase High-acid Hybrid algae production system Hydrocarbons Hydrodeoxygenation Hydrogenation-derived renewable diesel Hydrodesulphurisation High erucic High-erucic acid High-erucic acid rapeseed High-erucic B. carinata High-erucic rapeseed oil Hydroxy fatty acid High laurate canola oil Hydroxymethylfurfural High oleic High-oleic safflower oil High-oleic sunflower oil Heteropolyacid 3-Hydroxypropionaldehyde Hydroperoxide lyase Hydrogenated palm oil 3-Hydroxy-2-methyl-4-pyrone Hydroxypyruvic acid Hydrotalcite Hydrothermal upgrading Hydroxyl value Hydrotreated vegetable oil Hydrous zirconia Enzymatic interesterification In-line blending Internal standard Iodine value Jatropha curcas oil Jojoba oil Jet propellant b-Ketoacyl-ACP synthase b-Ketoacyl-CoA synthase Karanja methyl ester

(Bio)chemical nomenclature

LCB LCFA LC-PUFA LDH LE LEBC LME LNG LoLn LOX LPA LPAAT LPG LSO MAG MARS MCF, MCFA MCG MCT ME MESAC MFO MFT MG MO MON MONG MOSNO MSA MSTFA MSW MTBE MtS MUFA MW NERD NG NMHC NN NPO NuSun OFR OIT

Lignocellulosic biomass Long-chain fatty acid Long-chain polyunsaturated acid Layered double hydroxide Low erucic Low-erucic B. carinata Linolenic acid methyl ester Liquid natural gas Low-linolenic Lipoxygenase Lysophosphatidic acid Lysophosphatidic acid acyltransferase Liquefied petroleum gas Linseed oil Monoacylglycerol Microwave accelerated reaction system Medium-chain fatty acid Medium-chain glyceride Medium-chain triglyceride Methyl ester Mesooxalic acid Medium fuel oil Multi-feedstock technology Monoglyceride Mid oleic Motor octane number Matter organic not-glycerine Mid-oleic sunflower oil Methane sulphonic acid N-methyl-N-trimethylsilyltrifluoro-acetamide Municipal solid waste Methyl tert-butyl ether Methanol-to-synfuel Monounsaturated fatty acid Molecular weight Non-ester renewable diesel Natural gas Non-methane hydrocarbon Neutralisation number Neutralised palm oil Mid-oleic sunflower oil Oscillatory flow reactor Oxidative induction time

805

806

Biodiesel science and technology

OIT* OO OOO OOT OSC OSI PA PAH PAO PAP PBR PC PD PDAT Pdc P-FAD PFR PG PGE PGM PGO PGR PHA PHSME PILC PJO PKO PKOo PLA PLPO PM PMF PMG PMME, PME PMo PMO PMZ PNO PO, PMO POo POO POP PP

Oxidative induction temperature Olive oil Triolein Oxidation onset temperature Organic solar concentrator (1) Oxidative stability index; (2) Oil stability index (1) Palmitic acid; (2) Phosphatidic acid Polycyclic aromatic hydrocarbon Palm acid oil Phosphatidate phosphohydrolase Photobioreactor Phosphatidyl choline (1) Petroleum diesel; (2) Propane-diol Phospholipid: 1,2-diacylglycerol acyltransferase Pyruvate decarboxylase Palm fatty acid distillate Plug-flow reactor (1) Propylene glycol; (2) Polyglycerol Polyglycerol ester Platinum group metals Processed waste fryer grease Propylene glycol renewable Polyhydroxyalkanoate Partially hydrogenated soybean oil methyl ester Pillared clay Cold pressed jojoba oil Palm kernel oil Palm kernel olein Poly(lactic acid) Processed liquid palm oil Particulate matter Palm oil mid fraction Precious metal group Palm oil methyl ester Molybdophosphoric acid Periodic mesoporous (2–50 nm) organosilica Phosphate-modified zirconia Peanut oil Palm oil Palm olein (1) Palmitoyldiolein; (2) Palmitate-oleate-oleate (1) Oleodipalmitin; (2) Palmitate-oleate-palmitate Pour point

(Bio)chemical nomenclature

PPD PPP PPT PS pTSA PTT PUFA PUR PV PW RA RB RBD RBDHPOs RBDPO RBDPOo RBDPS RBO RCAS RCO RD RES RFO-ME RHOSNO RJO RME RMFO RON RPO RPOo RPOs RSBO RSO RTP SBEE, SEE SBME, SME SBO SC(F), sc SCM SCO SCR SCT

807

Pour-point depressant (1) Tripalmitin; (2) Palmitate-palmitate-palmitate Poly(propylene terephthalate) Palm stearin p-Toluene sulphonic acid Poly(trimethyleneterephthalate) Polyunsaturated fatty acids Polyurethane (1) Peroxide value; (2) Photovoltaics Tungstophosphoric acid Resin acid Refined and bleached Refined, bleached and deodorised Refined, bleached, deodorised hydrogenated palm stearin Refined, bleached, deodorised palm oil Refined, bleached, deodorised palm olein Refined, bleached, deodorised palm stearin Rice bran oil Refined castor oil Recycled cooking oil Reactive distillation Renewable energy sources Recycled frying oil methyl ester Refined high oleic sunflower Refined jojoba oil Rapeseed oil methyl ester Refined meadowfoam oil Research octane number Refined palm oil Refined palm olein Refined palm stearin Refined soybean oil Rapeseed oil Rapid thermal processing Soybean oil ethyl ester Soybean oil methyl ester Soybean oil Supercritical (fluid) Supercritical methanol Single cell oil Selective catalytic reduction Short-chain triglyceride

808

Biodiesel science and technology

SCW Sub-, supercritical water SEE Soybean ethyl ester SEO Sesame oil SFA Saturated fatty acid SFO Safflower oil SG Steryl glycoside SiW Tungstosilicic acid SME Soybean methyl ester SMR Steam methane reformer SN Saponification number SNG Synthetic natural gas SNME Sunflower oil methyl ester SNO Sunflower oil SOO Sulphur olive oil SPR ShockWave PowerTM reactor SRO Semi-refined rapeseed oil SS Soapstock SSS Tristearin STBE Solketal-tert-butyl ether STO Sulphated tin oxide STR Stirred tank reactor STT Spinning tube-in-tube SV Saponification value SVO Straight vegetable oil TAG (1) Triacylglycerol; (2) Triacetylglycerol TAN Total acid number TARAC Tartronic acid TBD 1,5,7-Triazabicyclo[4.4.0]dec-5-ene TBHQ Mono-t-butyl hydroquinone TCG 1,2,3-Tricyclohexylguanidine TE Acyl-ACP thioesterase TEMPO 2,2,6,6-Tetramethyl-1-piperidinyloxyl TFA Trans fatty acid TG Triglyceride THC Total hydrocarbons THF Tetrahydrofuran TiZ Titania zirconia TL Thermochemical liquefaction TLW Tallow TLW-ME, TME Tallow fatty acid methyl ester TMS Tetramethylsilane TO Tung oil TOC Tocopherol

(Bio)chemical nomenclature

TOFA TORA TPA TPP TriEG UCG UCO UFA UFO UFOME ULSD UMA UMT UMZ UPGO USBO VHO VI VLCFA VLCPUFA VO WCM WCO WFO WGS WOO WPMO WSBO WSNO WVO WZ XSA XTL YI D9DES

Tall oil fatty acid Tall oil rosin acid 12-Tungstophosphoric acid Three phase partitioning Triethylene glycerol Underground coal gasification Used cooking oil Unsaturated fatty acid Used frying oil Used frying oil methyl ester Ultra-low sulphur diesel Unmodified alumina Unmodified titania Unmodified zirconia Unprocessed waste fryer grease Used soybean oil Very high oleic Viscosity index Very long-chain fatty acid Very long-chain polyunsaturated fatty acid Vegetable oil Wax crystalline modifier Waste canola oil Waste frying oil Water-gas shift Waste olive oil Waste palm oil Waste soybean oil Waste sunflower oil Waste (spent) vegetable oil Tungstated zirconia Xylene sulphonic acid Gas/coal/biomass-to-liquid Yellowness index D9-Stearoyl-acyl carrier protein (ACP) desaturase

809

Appendix III

Physical and mathematical symbols

A Å ac a.m.u., amu bbl Bbu Bgy bn b.p. Bpd BTU, Btu Bty bu °C C, c c cP D d Da DL E e e– em eV ex f FT ft G g gpy H h h 810

(1) Absorbance; (2) Area Ångstrom, unit of wavelength; 1Å = 10–8 cm Acre Atomic mass unit barrel; 1 bbl = 42 gal Billion bushels Billion gallons per year Billion Boiling point Barrels per day British thermal unit; 1 BTU = 0.252 kcal Billion tons per year Bushel Degrees Centigrade Concentration or molar concentration Velocity of light Centipoise Number of double bonds (1) Diameter, thickness; (2) Density; (3) Diffusion path length Dalton or atomic mass unit Detection limit Energy (in eV) Electron Unit charge of an electron Emission wavelength used in fluorescence detection Electron volt; 23.06 kcal mol–1 Excitation wavelength used in fluorescence detection (1) Function (general); (2) Flow rate Fourier transform Foot Free enthalpy (Gibbs free energy) Gram Gallons per year Enthalpy Hour Planck’s constant

Physical and mathematical symbols

HR HT Hz hn I I0 i.d. in. J K k k

811

High resolution High temperature Hertz, unit of frequency (cycles per second) Photon energy in eV Intensity Intensity of incident light Internal diameter Inch Joule, a unit of energy Kelvin Kilo (103) (1) Molar absorption coefficient; (2) Reaction rate constant kgd kilogallon per day kgoe kilogram oil equivalent kgy kilogallon per year L Litre L, l Length (column length; chain length) l Pathlength lb pound; 0.453 kg l/d Length-to-diameter LHSV Liquid hourly space velocity LOD Limit of detection LOQ Limit of quantitation LSR Least squares regression M (1) Molarity (mol L–1); (2) Mega (106) M Atomic or molecular weight m (1) Milli; (2) metre m Mass of atom or ion Mbd Million barrels per day Mbu Million bushels MDL Method detection limit mg, mmol, mL Milligram, millimole, millilitre (10–3) Mgy Million gallons per year MMgy Million metric gallons per year MMLy Million metric litres per year MMT Million metric tons m.p. Melting point MPa Mega Pascal MT, Mt Metric tonnes, million tonnes Mtoe Million tonnes of oil equivalent MW (1) Molecular weight; (2) Megawatt MWh Megawatt hour

812

Biodiesel science and technology

MWP m/z N N n n Nd, n.d. ng, nm, nmol p pc Pa PC PCA PCR PDA PJ PLS(R) pmt ppb ppm R R2 r RF, r.f. rms RSD, r.s.d. r.t. S S s, sec SD S/N SPC T Tc Tm t t TEP TOE, toe TRF TW V

Megawatt photovoltaic Mass-to-charge ratio Normal Noise Refractive index (1) Number of components; (2) Number of measurements Not detectable Nanogram, nanometre, nanomole (10–9) Pressure Critical pressure Pascal Personal computer Principal component analysis Principal component regression Principal discriminant analysis PetaJoule Partial least squares (regression) Per metric ton Parts per billion Parts per million (1) Universal gas constant; (2) Resolution Square of the multiple correlation coefficient (1) Reaction rate; (2) Radius Radiofrequency Root mean square Relative standard deviation Room temperature Solubility Solubility coefficient Second Standard deviation Signal-to-noise ratio Statistical process control (1) Absolute temperature (K); (2) Transmittance Critical temperature Melting temperature ton Time ton of petroleum equivalent; 1 TEP = 42 GJ tonne of oil equivalent (or TEP) Theoretical response factor Terawatt (1 TW = 1012 W) Volt

Physical and mathematical symbols

V v v/v W WHSV w/w x,y,z Y% Z z e h q l m mm n r

Volume; molar volume Velocity Volume/volume (solution concentration) Watt, measure of RF power Weight hourly space velocity Weight/weight (solution concentration) Cartesian coordinates Extraction yield Atomic number Ion charge Molar absorption coefficient Viscosity of medium Incident angle Wavelength, unit Å (1) Micro (10–6); (2) Absorption coefficient Micron (1) Frequency (Hz); (2) Velocity Density, g cm–3

813

Appendix IV General abbreviations

AAFC

Antioxidants Aromas & Fine Chemicals (Richards Bay, S. Africa) ABI (1) Austrian Biofuels Institute (Vienna, Austria); (2) Allied Biodiesel Industries (Bangor, UK) ABO Algal Biomass Organization (Preston, MN) ABPR Animal By-Products Regulation ACS American Chemical Society (Washington, DC) ADEME Agence de l’Environnement et la Maîtrise de l’Energie, Agency for Environment and Energy Management (Paris, France) ADM Archer Daniels Midland Co. (Decatur, IL) AFOA American Fats and Oils Association (Columbia, SC) AGD Aceitera General Deheza S.A. (Buenos Aires, Argentina) AGQM Arbeitsgemeinschaft Qualitätsmanagement Biodiesel eV, German Association for the Quality Management of Biodiesel (Berlin, Germany) ANP Agencia Nacional de Petióles, Brazilian National Agency for Petroleum, Natural Gas and Biofuels AOCS American Oil Chemists Society (Urbana, IL) APS Arizona Public Service Company (Phoenix, AZ) AROA American Renewable Oilseed Association (Carrington, ND) ASAE American Society of Agricultural Engineers (St. Joseph, MI) ASG Analytik-Service Gesellschaft (Neusäß/Augsburg, Germany) ASP Aquatic Species Program (DOE) ASTM American Society for Testing and Materials (West Conshohocken, PA) AWI Alfred-Wegener-Institute für Polar und Meeresforschung (Bremerhaven, Germany) BAP Biomass Action Plan (EU) BDI BioDiesel International AG (Grambach/Graz, Austria) BDT BioDiesel Technologies (Vienna, Austria) BERR Dept. for Business, Enterprise and Regulatory Reform (London, UK) BIOFRAC Biofuels Research Advisory Council (EU) BLT Bundesanstalt für Landtechnik, Federal Institute of Agricultural Engineering (Wieselburg, Austria) BRIC Brazil, Russia, India and China BS British Standards 814

General abbreviations

BSE BTAC BUND CAB CAP CARB CCC CCD CDM CEC CEN CER CI CIS CNAP CNBC COA CSP d DARPA DBO DEFRA DI DIN DOE DOT DPT EBB EBI EC EEA EEC EERC EIA EI-IP

815

Bovine spongiform encephalopathy (‘Mad cow disease’) Biomass Technical Advisory Committee (Gaithersburg, MD) Bund für Umwelt und Naturschutz Deutschland, Friends of the Earth in Germany (Berlin, Germany) Commonwealth Agricultural Bureaux Ltd (Wallingford, UK) Common Agricultural Policy (EU) California Air Resources Board (San Francisco, CA) Commodity Credit Corporation (USA) Colony Collapse Disorder Clean Development Mechanism (Kyoto Protocol) Commission of the European Communities (Brussels, Belgium) Comité Européen de Normalisation, European Committee for Standardisation (Brussels, Belgium) Certified Emission Reduction (Kyoto Protocol) Compression ignition Commonwealth of Independent States Centre for Novel Agricultural Products (York, UK) Compania Nacional Bio Combustibles (Costa Rica) Certificate of Analysis Concentrating solar power (1) Domestic; (2) Day Defense Advanced Research Projects Agency (Arlington, VA) Desmet Ballestra Oleo (Rome, Italy) Department of Environment, Food and Rural Affairs (London, UK) Direct injection (1) Deutsches Institut für Normung, German Institute on Standardisation (Berlin, Germany); (2) Deutsche Industrie Normen (German Industrial Standards) US Department of Energy (Washington, DC) US Department of Transportation (Washington, DC) Davy Process Technology, Ltd (London, UK) European Biodiesel Board (Brussels, Belgium) Energy Biosciences Institute (Berkeley, CA) European Community European Environment Agency (Copenhagen, Denmark) European Economic Community Energy & Environmental Research Center (University of North Dakota) Energy Information Administration (Washington, DC) Energy Institute/Institute of Petroleum (London, UK)

816

Biodiesel science and technology

EISA EM(S) EN ENV EPA EPAct EROI ETP ETS EU EUREC EV FAO FB4P FCC FDA FFB FFD FFV FNR GBC GDCh GDP GM GMO GRAS GREET GTZ HECO HEV HSE HYSYS i IATA IBF ID IDI

Energy Independence and Security Act (USA) Effluent management (systems) European Norm European Prestandard Environmental Protection Agency (Washington, DC) Energy Policy Act Energy return-on-investment European Technology Platform Emissions Trading Scheme European Union European Renewable Energy Council (Brussels, Belgium) Electric vehicle Food & Agriculture Organization of the United Nations (Rome, Italy) Federal Biobased Products Preferred Procurement Program (US DOE) Food Chemical Codex Food and Drug Administration (Rockville, MD) Fresh fruit bunch Food or feed use Flex-fuel vehicle Fachagentur Nachwachsende Rohstoffe, German Agency for Renewable Resources (Gülzow, Germany) Global Biofuels Center (TX, USA) Gesellschaft Deutscher Chemiker, German Chemical Society (Frankfurt, Germany) Gross domestic product Genetic modification Genetically modified organisms Generally recognised as safe Greenhouse gases, regulated emissions, and energy in transportation Deutsche Gesellschaft für Technische Zusammenarbeit, German Agency for Technical Cooperation (Eschborn, Germany) Hawaiian Electric Co. (Honolulu, HI) Hybrid electric vehicle Health, Safety and Environment HYprotech SYStem (Aspen Tech, Cambridge, MA) Import International Air Transport Association (Montréal, QC) International Biofuels Forum (UN) Ignition delay Indirect injection

General abbreviations

IEA IFEU IFP IFT IGCC IMF IOC IPCC IRS ISAAA ISHS ISO JES JORF KIT KNAW LCA LCFS LHP LIHD MHP MIU MPOB MUW MWV NACTA NBAC NBB NBS NCL NGB NIST NOVOD

817

International Energy Agency (Paris, France) Institute for Energy and Environmental Research (Heidelberg, Germany) Institut Français du Petrole, French Institute of Petroleum (Rueil-Malmaison, France) International Fuel Technology, Inc. (St. Louis, MO) Integrated Gasification Combined Cycle International Monetary Fund (Washington, DC) Indian Oil Corporation (New Delhi, India) Intergovernmental Panel on Climate Change (Geneva, Switzerland) Internal Revenue Service International Service for the Acquisition of Agri-biotechnology Applications International Society for Horticultural Science (Louvain, Belgium) International Organization for Standardization (Geneva, Switzerland) Jatropha Energy System Journal Officiel de la République Française Karlsruhe Institute of Technology (Karlsruhe, Germany) Koninklijke Nederlandse Akademie van Wetenschappen (Amsterdam, Netherlands) Life cycle assessment, life cycle analysis Low carbon fuel standard Large-scale hydropower Low-input high-diversity Microhydropower Moisture, impurities and unsaponifiables Malaysian Palm Oil Board (Kuala Lumpur, Malaysia) Mitteldeutsche Umesterungswerke (Greppin, Germany) Mineralölwirtschaftsverband, Association of the German Petroleum Industry (Berlin, Germany) North American Camelina Trade Association (Bozeman, MT) National Biodiesel Accreditation Committee (Jefferson City, MO) National Biodiesel Board (Jefferson City, MO) National Bureau of Standards (now NIST) National Chemical Laboratory (Pune, India) New Generation Biofuels Holdings, Inc. (Baltimore, MD) National Institute of Standards and Technology (formerly NBS) (Gaithersburg, MD) National Oilseeds and Vegetable Oils Development Board (Gurgaon, India)

818

Biodiesel science and technology

NRDC NREL NUW OECD OEM ÖN OPEC PBI PH.EUR PORIM PTT QA QC QM R&D R&T RE REA RED REG RES RFS RIN RIRDC RITE RO ROI ROW RSB RSP RSPO RTFO RTR SAE SBA SDA SETAC

National Resources Defense Council (Honolulu, HI) National Renewable Energy Laboratory (Golden, CO) Nordbrandenburger Umesterungswerke (Schwedt/Oder, Germany) Organisation for Economic Co-operation and Development (Paris, France) Original equipment manufacturer Österreichisches Normungsinstitut (Vienna, Austria) Organization of Petroleum Exporting Countries (Vienna, Austria) Plant Biotechnology Institute (Saskatoon, SK) European Pharmacopœia Palm Oil Research Institute of Malaysia (Kuala Lumpur, Malaysia), now MPOB Petroleum Authority of Thailand (Bangkok, Thailand) Quality assurance Quality control Quality management Research & Development Research & Technology Renewable energy Renewable Energy Association (London, UK) Renevable Energy Directive (EU) Renewable Energy Group, Inc. (Ames, IA) Renewable energy sources Renewable fuels standard Renewable identification number Rural Industries Research and Development Corporation (Kingston, Australia) Research Institute of Innovative Technology for the Earth (Kyoto, Japan) Renewables Obligation (UK) Return on investment Rest of the world Roundtable for Sustainable Biofuels (Lausanne, Switzerland) Required selling price Roundtable on Sustainable Palm Oil Renewable Transport Fuels Obligation (UK) Recyclat Tierischer Rohstoffe (Selm, Germany) Society of Automotive Engineers (Warrendale, PA) Sustainable Biodiesel Alliance (Austin, TX) Soap and Detergent Association (Washington, DC) Society of Environmental Toxicology & Chemistry (Washington, DC)

General abbreviations

SFA SHP SI SRC SRI TBK TBO TCI TEC TMC UBA UCS UFOP UKPIA UL UN UNDP UNFCCC US, USA USDA US EPA USP VDB VNBI VTT WEC WEU WFC WHOI WIPO WTO WTW WUR WWF

819

State Forestry Administration (Beijing, PRC) Small hydropower systems Spark ignition Saskatchewan Research Council (Saskatoon, SK) Stanford Research Institute (Stanford, CA) Thész, Boros, Király Tree borne oil(seed) Total capital investment Transatlantic Economic Council (EU/US) Total manufacturing cost Umweltbundesamt, German Environmental Protection Authority (Dessau-Roßlau, Germany) Union of Concerned Scientists (Cambridge, MA) Union zur Förderung von Öl- und Proteinpflanzen eV, Union for Promotion of Oil and Protein Bearing Plants (Berlin, Germany) UK Petroleum Industry Association (London, UK) Underwriters Laboratory, Inc. (Camas, WA) United Nations (New York, NY) United Nations Development Program (New York, NY) United Nations Framework Convention on Climate Change United States of America US Department of Agriculture (Washington, DC) United States Environmental Protection Agency (Washington, DC) United States Pharmacopœia Verband der Deutschen Biokraftstoffindustrie eV, Association of German Biofuel Industry (Berlin, Germany) Vereniging Nederlandse Biodiesel Industrie, Netherlands Biodiesel Industry Association (Rotterdam, Netherlands) Valtion Teknillinen Tutkimuskeskus (Helsinski, Finland) World Energy Council (London, UK) Western Europe Worldwide Fuel Charter Woods Hole Oceanographic Institution (Falmouth, MA) World Intellectual Property Organization (Geneva, Switzerland) World Trade Organization (Geneva, Switzerland) Well-to-wheel Wageningen University Research Centre (Wageningen, Netherlands) World Wildlife Fund (Gland, Switzerland)

Appendix V

Main websites

http://biodieselanalytical.com http://koal.cop.fi/leonardo http://projectbiodiesel.com http://www.agqm-biodiesel.de/ http://www.algaelink.com http://www.amberlyst.com http://www.americanbiodiesel.com http://www.argentinarenovables.org http://www.atlanticbioenergy.ca http://www.basf.com/biodiesel http://www.bbiinternational.com http://www.bdi-biodiesel.com http://www.biodiesel.co.uk http://www.biodiesel.com http://www.biodiesel.com.au http://www.biodiesel.de http://www.biodiesel.it http://www.biodiesel.org http://www.biodieselaustria.com http://www.biodiesel-intl.com/ http://www.BiodieselMagazine.com http://www.biodieselsustainability.com http://www.biodieseltesting.com http://www.biofuels.coop http://www.BiomassMagazine.com http://www.biostab.info http://www.bq-9000.org http://www.BSGBiodiesel.com http://www.caed.uga.edu http://www.crowniron.com http://www.dallasgrp.com http://www.demariabuild.com http://www.desmetballestraoleo.com http://www.dieselnet.com http://www.ebb-eu.org http://www.ecdiesel.com http://www.evonik.com/biodiesel 820

Main websites

http://www.foxpetroli.com http://www.greenfuels.org http://www.griffinind.com http://www.itabia.it/web/biodiesel_nel_web.htm http://www.italbioil.com http://www.jatropha.de http://www.lurgi.com http://www.making-biodiesel-books.com/ http://www.martinisrl.it/biodiesel http://www.regfuel.com http://www.rohmhaas.com http://www.soygold.com/biodiesel.htm http://www.srsbiodiesel.com http://www.therenewablenetwork.com http://www.valcent.net http://www.villesdiester.asso.fr

821

Index

Abbreviations 799 ff, 801 ff, 814 ff Acid-catalysed transesterification 339 ff, 364 ff, 473, 476 ff Benefits 326, 398 Disadvantages 326, 347 Kinetics 339 Mechanism 325, 339 ff Reaction conditions 342, 344 ff, 365 Water concentration 346 Acid oils 205, 666 Transesterification 345, 411, 422, 451 Acidolysis 285 Acid value (AV) 242, 386, 397 Crude vegetable oils 386 Acronyms 799 ff Africa 117, 263 ff Fertiliser program 264 Potential energy crops 262 African pumpkin 263 AGQM (Arbeitsgemeinschaft Qualitätsmanagement Biodiesel) 528 Agricultural industry 50 ff Feed 51 Food 51 Fuel 51, 53 Agroenergy crops 56 Alcoholysis 285 Branched chain 288, 408, 444, 450, 645 Ethanolysis 289, 408, 450 Methanolysis 288 Requirements 287 Algae 168 ff Biosynthesis 70 Cultivation 174 ff commercial developments 179 ff

822

Farm 180 ff Oil production 174 challenges 174 costs 178 fatty acid profile 173 Renewable biofuels 169 Strains 172, 174 Algae-to-biodiesel 171, 414 ff, 690 Aquatic Species Program 170 Economics 418 Prospects 183, 418 ff Technology providers 497 Algal biomass 169 Oil extraction 170, 184 Use 169, 187 Alkali-catalysed transesterification 296, 327 ff, 356 ff Kinetics 296, 337 Mechanism 325, 330 Alkoxides 293, 296, 327, 333 ff Aloe vera 191 ALTENER program (EU) 657 Alternative diesel fuels 713 ff, 726, 728 Amazon 256, 262 Deforestation 633 Palms 257, 259 Amberlite™BD10Dry™ purification technology 472, 734 Amberlyst™BD20 (trans)esterification technology 364, 391, 409, 732 ff Ambersep™BD19 purification technology 388 Ambersep™BD50 glycerin purification technology 578 ff Amide biodiesel 614 Animal fats 64, 197, 200, 202, 665

Index

Biodiesel 202 ff Bovine spongiform encephalopathy 202 Butter 62, 202 Fatty acid profiles 131 ff Fish 62, 163 ff Fractionation 154 Fuel properties 116 Lard 62, 64, 198, 202, 402 Pork 199 Poultry 198, 306, 312 Production 135, 204 Tallow 62, 198, 201, 498, 500, 787 Transesterification 665 Turkey 422 Yellow grease 199 ff, 665 p-Anisidine value 244 Antifreeze 580, 592 Antioxidants 241, 557, 650 Aqueous-phase carbohydrate reforming 597 ff Hydrogen production 596 ff Liquid hydrocarbon fuels 596 Archer Daniels Midland Co. (ADM) 38, 146, 518, 575, 691, 696 Argan (A. spinosa) oil 159 Argent Energy 204, 498 ff Argentina 498, 697 ff Biotech crops 57 Soybean 57 Soy biodiesel 677, 697 export 664, 677, 697 industry 31, 468, 697 ff investment costs 659 producers 498 production 664 Asia 200, 245 ff, 250 ff Biodiesel status 28, 501 Energy policy 16 Australia 694 Biodiesel industry 31, 172, 204, 500, 694 Microalgae 173, 182 Austria 731, 752 BDI – BioDiesel International 400, 420, 493, 495, 498 ff, 731 Biodiesel industry 30 ff, 200, 682 Avantium 720 Avocado 65, 76, 79, 93, 259

823

Babassu (Orbignya spp.) 93, 257 ff Bacteria 187 Balanites (B. aegyptiaca) 263 BASF 334, 591 Bayer 58, 518 B. carinata 80, 147, 243, 266, 272, 534 Transesterification 335 BDI – BioDiesel International 400, 420, 493, 495, 498 ff, 731 Multi-feedstock technology (MFT) 495 RepCat 401, 495 Beef tallow 62, 198, 201 Transesterification 333, 488 Benefuel, Inc. 356, 604, 728 ENSEL™ 356, 604, 728 Bio-based diesel fuels 23 ff, 123 Prospects 768 Bio-based fuels 23 ff, 720 Biobutanol 15, 609, 721, 724 Biocatalysis 434 ff, 768 Biochemical nomenclature 801 ff Biodegradation 74, 639, 641 Biodiesel 7 ff, 26 ff, 52 Additives 642, 646 Advantages 638 ff Aging 557 Analysis chart 541 Analytical methodology 540 ff chromatography 540 ff, 560 ff hyphenated techniques 546, 548 ff oxidation stability 555 ff physical property testing 561 spectroscopy 536 ff, 544, 549 ff titration applications 521, 558 ff trace contaminants 559 ff Asia 28, 501 Availability 27, 140 Biocatalysis 434 ff, 788 Biodegradability 639, 641 Blending technologies 505 ff fuel dispenser 506, 508 hybrid 507 in-line 506, 795 ratio 507 sequential 507 sidestream 507 splash 506, 795 Blends 28, 645, 655 analytics 534, 539, 546, 551, 554

824

Index

seasonal 202, 680 Catalysis 322 ff, 729 Chemical formula range 22 Competitiveness 672 ff, 676, 696, 698 Concept 285, 473 Consumer awareness 796 Cost Optimizer 244, 658 Cost (structure) 253, 310, 411, 474, 658 ff, 666 ff, 696 ff Definitions 22 Disadvantages 640 Distillation 520, 522, 541 Distribution 464, 537 Economic evaluation 466, 666 ff, 672 ff, 679 Environmental effects 59, 144 Enzyme catalysis 434 ff EU Directives 8 ff Exhaust emissions 650 ff Export 15, 36, 40, 664, 677, 785 Feedstock 100, 130 ff, 143 ff, 226 ff, 462, 468, 663 control 466 ff costs 141, 253, 411, 474, 660 ff FFA contents 155, 323, 387, 665, 734 normalisation 738 quality indicators 130, 231 recycled 197 ff, 463 regional 138, 465 structure parameters 231 virgin 100, 322, 463 Global development 26, 500 Global nameplate capacity 500 Global production 500 Governmental support 8 ff, 796 History 26, 30 ff, 33 ff Ignition quality 243, 658 Industry 784 ff by-products 797 challenges 638, 789 ff current state 784 ff energy policy 793 feedstocks 785 ff, 791 ff foodstocks 786, 793 fuel quality 795 legislation 793 manufacturing technologies 787, 794

marketing 797 process economics 797 production capacity 796 regulations 793 sustainability 786, 790 Life cycle assessment 630 ff, 657, 699 Lipase-catalysed production 436, 452 Lubricity additive 22, 640, 677, 693 Macroeconomic effects 637 Mandates 11 Manufacturing technologies 452, 465 ff, 468 batch processing 479 ff continuous-flow processing 482 ff cost comparisons 474, 486, 666 ff hybrid processing 486 multi-step processing 469, 481 ff, 485 semi-continuous processing 481 single-step processing 469, 482 Markets 16, 140, 465 ff, 677 ff, 688 Multi-feedstock 463, 482, 486, 495 Nameplate capacity 678 ff National strategies 10 ff Next-generation 670, 674, 713 ff, 724 ff OEM acceptance 518 ff, 657, 679, 796 ff On-farm 679 Overcapacity 676, 693 Oxidation stability 520, 525, 532, 555 ff Plants 462 ff analytical support 515 design 437, 467 ff location 463 portable 465 size 463 ff, 468, 692 Polyunsaturated fatty acids (PUFAs) 62, 70, 165, 231, 239, 244, 525, 643 ff Processes 437, 462 ff, 473 advanced technology 725, 787 catalysts 322 ff, 434 ff, 469, 472 ff downstream operations 469 ff flow sheets 467 ff, 472 ff intensification 725 limits 725 operating conditions 331, 344, 468, 475, 478, 480

Index phase separation 471 reactor design 468 ff Production 27, 678 community scale 117 ff, 465, 482, 485, 497 ff, 679, 695 EU 30, 676, 680 ff national scale 254, 696 ff, 700 plantation scale 195, 246, 250, 254, 257, 263, 265, 413, 700 regional scale 465 strategic factors 466 USA 36, 688 ff Production capacity 32, 688 ff, 693 Argentina 31, 697 ff Australia 31, 694 Austria 31, 682 Benelux 682, 687 Brazil 696 Canada 693 ff Eastern Europe 687 Europe 680 ff Finland 682, 687 France 682, 685 Germany 681 ff India 700 Indonesia 700 Italy 682, 685 Malaysia 31, 700 ff Netherlands 31, 682, 687 P.R. China 31, 699 ff South-East Asia 505, 700 ff Spain 682, 685 ff UK 682 ff USA 31, 688 ff Properties 552, 637 ff, 654 ff acid value (number) 520, 525 ash content 520, 525 biodegradability 639, 641 boiling point 638 carbon residue 520, 525 cetane number (CN) 231, 234 ff, 520, 525, 532, 551, 639 cloud point (CP) 243, 520, 531, 637 ff, 642 cold-temperature performance 641 ff copper-strip corrosion 520, 525 density 525, 561, 638 distillation temperature 520





825

flash point 520, 525, 561 ff, 638 heating value 638 ignition quality 243, 658 iodine value (IV) 231 ff, 525 kinematic viscosity 121, 520, 522, 525, 638 physical appearance 22 pour point (PP) 638, 642 ff reactivity 640 saponification value (SV) 231, 233 specific gravity 638 storage stability 241, 649 sulphur content 520, 525, 638, 640 thermal stability 525 toxicity 635, 639, 641 viscosity 23, 655 vs. conventional diesel fuel 638 water content 520, 525, 638, 641 Purity 471 Quality 657 Stability 237 ff, 555 ff, 649 BIOSTAB project 650 feedstock source 241 manufacturing process 241 metal contamination 241 stabilisers 242 storage 241, 649 Standardisation 516 ff certified reference materials 517, 560 engine warranties 518 international compatibility 518 specifications 518 Supply chain 38 Sustainability 625 ff Technology providers 467, 487 ff BDI 400, 420, 493, 495, 498 ff, 731 BIOX Corp. 493 CD Connemann 38, 490 ff, 500, 678 Desmet Ballestra 495, 504, 659 Energea 477, 487 IFP-Axens 495 ff, 501 Lurgi 493 ff Pacific Biodiesel 497 Testing protocols 516 ff ASTM D 396-08b (up to B5) 523 ASTM D 975-08 (up to B5) 121, 523

826

Index

ASTM D 6751-08 (B100) 519 ff ASTM D 7467-08 (B6 to B20) 519 ff ASTM D 7501 523 EN 590 (European Automotive Diesel Standard) 526 EN 14214 (B100) 524 ff, 655 European biodiesel standards 517, 524 ff procedures 519 ff, 524 ff Transesterification 22, 285 ff Use 625 ff, 640, 677 ff Biofining™ technology 761 Biofuels 715 ff, 719 ff Biobutanol 15, 721, 724 Biodiesel 52, 773 Biodimethylether 52, 720 Bio-ETBE 52 Bioethanol 15, 26 ff, 35, 52, 169, 256, 290, 630, 677, 692, 695, 699, 716 ff, 722, 765 ff, 773 Biogas 52, 721, 773 Biohydrogen 52, 593, 596 ff, 714 Biomethanol 52, 587, 716, 720 Bio-MTBE 52 Directive (EU) 8 First-generation 715 ff Furanics 720 Jet fuel 678 Next-generation 670, 719 ff, 722 Production 26 ff R&D 19 Sustainability 80, 636, 790 Targets 8 Technologies 125 developments 125, 721 next-generation 722 BioLiq® 759, 765 ff Biomass 714 Cellulose 15, 21, 50, 721, 756 Conversion processes 21, 715 Lignocellulosics 51, 721, 724 Limitations 52 Potentials 52 Production 50 Resources 20 Biomass Action Plan (EU) 757 global 757, 772 USA 54, 758

Transformation 20 ff anaerobic digestion 21, 169, 718 enzymatic hydrolysis 718 fermentation 21, 169, 714 ff gasification 20, 169, 715, 721 pyrolysis 21, 169, 715, 721 thermolysis 21, 715 Use 50 Biomass-to-liquids (BTL) 21, 630, 721, 723, 748 ff, 756 ff, 760 ff Fuels 724, 756 ff Technologies 760 ff, 764 ff BioMethanol Chemie Nederland/BioMCN 575, 587 Biopolyester 454 Biocatalysis 454 Biorefinery 180, 718 ff Bioscopes 547 Biotech crops 57 Argentina 57 Brazil 57 Canada 57 India 57 P.R. China 57 USA 57 Biotechnology 56 Bisphenol-A glycidyl ethers 607 ff Blackcurrant oil (R. nigrum) 82 Enzymatic alcoholysis 441 Black liquor 267, 720 Transesterification 402 Blend ratio 28 Analytics 550, 554 Control 533 ff Blend sensors (on-vehicle) 539 Bovine spongiform encephalopathy 202 BP 19, 724, 747 ff, 759, 766 ff BQ-9000 fuel quality 530 Brassica 76, 80, 82, 143 ff Brazil 37, 204, 695 ff Biodiesel 37 feedstock potential 37, 204, 244 ff, 256 industry 695 ff plant size 464, 482, 696 producers 469, 505, 696 production cost 696 Bioethanol 27, 695 Biotech crops 57

Index Energy policy 16 H-BIO process technology 755 Petrobras 19, 264, 696, 755 Probiodiesel 16, 256, 695 Tallow diesel 204 Breakthrough biodiesel technologies 726 ff Amberlyst™ BD20 (Rohm & Haas) 732 ff ENSEL™ (NCL) 356, 728 Esterfip-H™ (IFP-Axens) 401, 495, 726, 729 ff Mcgyan 358, 402, 728 Nova Biosource Technologies 408, 410 RepCat (BDI) 401, 731 ff Yellowdiesel 469, 579 Breeding technologies 56 British Sugar 724 Brown grease 199, 266 Biodiesel 203, 463 Transesterification 410 Buffalo gourd (C. foetidissima) 259 Butafuel™ 609 Butter 62, 202 Calculated cetane index (CCI) 521 Calendula 78 Camelina (C. sativa) 190, 244, 265, 270, 792 Biodiesel 265 Oil 117 alcoholysis 445, 452 Canada 266, 463, 693 Biodiesel industry 31, 693 ff Biotech crops 57 BIOX Corp. 493 British Columbia 265, 694 biodiesel feasibility study 466 community-scale biodiesel 465 Canola 146, 266, 693 Nova Scotia 167 Potential energy crops 266 ff Candida antarctica 436, 438, 448 Candida rugosa 439 Canola 37, 144 ff, 266 Biodiesel 463, 691, 693 Carbonates 336 Cardoon (C. cardunculus) 189, 267, 272, 291, 792 In-situ transesterification 309

827

Cargill 38, 575, 593, 607 CaroDiesel 251 Castor beans (R. communis) 54, 190 Oil 82, 84, 87, 115, 246, 269 biodiesel 256 transesterification 445 Catalysts 293, 322 ff, 386 ff, 434 ff Metal alkoxides 293, 296, 327, 333 ff Metal hydroxides 293, 296, 327, 332 ff Certification 18, 156, 250, 636 Cetane number (CN) 231, 234 ff, 520, 525, 532, 639 Analytics 551 Ignition Quality Tester™ 235 Chain length 242 Chemical nomenclature 801 ff Chevron 19, 55, 419, 768 Chinese tallow tree (T. sebifera) 255 Chirazyme 451 Chokecherry (P. virginiana) 267 Choren/Shell technology 762, 764 ff Chromatography 540 ff GC 543 ff HPLC 547 ff IC 549, 560 ff SEC 549 SFC 549 TLC 540 Chromobacterium viscosum 441 Climate change 1 Cloud point (CP) 243, 520, 532, 642 Coal-to-liquid (CTL) technologies 699, 762, 767 Coconut (C. nucifera) 158, 265 Oil 115, 386 biodiesel 38, 630, 632 ff Cod liver oil 166, 739 Ethanolysis 451 CO2 cycles 7 CO2 emissions 7, 15, 252, 632, 652 Coffee grounds 163 Cold-climate biodiesel 648 Cold-filter plugging point (CFPP) 243, 642 Cold-flow improvers (CFIs) 642, 645 ff Cold-flow properties 243, 644 ff Cold-soak filtration test (CSFT) 522 ff Cold-temperature performances 641 ff Handling 641 Operability 641 ff

828

Index

Colombia 257 Palm biodiesel 257, 699 Common Agricultural Policy (CAP) 9, 54 Community-scale biodiesel 117 ff, 465, 482, 485, 497 ff, 679, 695 ConocoPhillips 19, 500, 747 ff, 759 ff, 768 Contaminants 98 Analytics 559 ff Antioxidants 98, 388 Catalyst residues 472 FFA 388 Glycerides 483, 522, 525 Glycerol 472, 522, 525 Metal salts 98, 238, 241, 522, 525, 560 Methanol 472, 525 Particulates 98, 388 Phosphorus 98, 388, 525, 560 Residual alcohol 472 Soaps 472, 522 ff, 559 Sterols 522 Steryl glycosides (SGs) 522 ff Sulphur 525, 560 Water 98, 388, 525 Continuous deglycerolisation (CD) 490 ff Continuous stirred-tank reactor (CSTR) 473, 483 Continuous Trans-Esterification Reactor (CTER) 484 Controlled cavitation 469 Coriander (C. sativum) 270 Corn 55, 244 Oil 82, 160 Corn-to-ethanol 35, 54, 692 Cornus wilsoniana 254 Corrosion 334, 347, 364, 473, 640 ff Cosmetics oils 82 Co-solvent blending 124 Cottonseed (G. herbaceum) oil 82, 95, 160, 386 Transesterification 411 C. protothecoides 184 Transesterification 416 Crambe (C. abyssinica) 78, 145, 189, 263, 792 Oil 82, 445, 452 alcoholysis 445, 452 Crop selection criteria 227 Agronomic characteristics 229 Chemical composition data 227

DOE criteria 227, 265 Croton (C. tiglium) 192 Crude oil pricing 29 Crude palm oil 100, 155, 664 Fuel use 122 Crude vegetable oils 386 Contaminants 98 Costs 141, 253, 310, 411, 474, 658 ff Deacidification 100 Refining 98 Transesterification 395, 398 Cryptococcus curvatus 444 Crystallisation fractionation 645, 648 Cuphea 78 ff, 82, 86, 124, 267, 269 ff, 792 Davy Process Technology 592 DDG corn oil 161 Transesterification 410 Deacidification 100, 155, 326, 388 Deforestation 156, 633, 697, 701, 717, 791 Degumming 100, 388 Degussa 303, 334, 573, 589 ff Density 525, 561, 638 Dewaxing 100 Diacylglycerols 72, 286, 291, 327, 483, 614 Diesel 114 Cars 30 Energy content 236 Engines 114, 120 ff Fuel processing 23, 30, 757 blending 23, 505 ff cracking 23 gasification 23 hydrotreating 23, 26, 742 ff microemulsification 23, 124 ozonation 23, 26, 614, 647 pyrolysis 23 transesterification 23, 285 ff, 322 ff Standard (EN 590) 526 Diesel Rudolf 114 Diester® 680 Diester Industrie 38, 498, 659, 730 Diglycerides 72, 286, 291, 327, 483, 614 Distillers dried grains 161 Distribution chain 537 Quality control 537 ff Dow Chemical Co. 363, 368, 575, 593, 607, 766

Index Drying oils 82, 156 DuPont 19, 58, 334, 589, 593, 724, 767 Dynamic turbulence 303 ff, 476 ShockWave Power™ reactor 303, 470, 725 STT technology 304, 470, 725 Ecobalance, See life cycle assessment Ecofining™ hydroprocessing 747, 753 ff Green Diesel 753 ff Edible nuts 262 Edible oils 143 ff, 159 ff Cluster analysis 227 Global production 50 Market segments 50 Energy 1 ff, 772 ff Balance 627 ff coconut biodiesel 630 rape biodiesel 627 soy biodiesel 627 Consumption 3 Crops 51 Europe 54 Independence and Security Act (USA) 14, 36 Needs 53 Policy 3, 12 Act (EPAct, USA) 13 ff, 22, 688, 693 Asia 16 Brazil 17 EU 17 P.R. China 16 USA 17 Security 53, 784 Sources 2 Tax Directive (EU) 8 Engine performance 120 Eni 753 ff, 759 ENSEL™ process 356, 604, 613, 728 Enzymes 435 Denaturation 436 ff Organic solvent tolerance 439 Specificity 438 Transesterification 434 ff characteristics 435 solvent-free 442 Epicerol™ process 605 ff Epichlorohydrin 605 ff

829

Eruca (E. sativa) 271 Escherichia coli 454, 610, 740 Esterfip-H™ 495, 501, 579, 729 ff Esterfip technology 354, 495 ff, 501 Esterification 285, 389 ff, 665 Acid-catalysed 390, 478 Biocatalysts 443 Free fatty acids 389, 442 Liquid acid catalysts 390 Reaction medium 440 Solid-acid catalysts 364, 390 ff Amberlyst™ BD20 364, 391 heteropolyacids 393 ion-exchange resins 391 mesoporous materials 392 mixed-metal oxides 393 superacids 392 ff zeolites 392 Water effect 396, 410 Ester value (EV) 242 Ethanolysis 256, 289, 408, 411, 484 Lipase-catalysed 450, 451 Ethylene glycol 590 Euphorbia 78, 88, 267, 270 Europe (EU) 17 Biodiesel 27 demonstration plants 498 ff investment costs 659 nameplate capacity 678 ff, 682 producers 483, 502 ff, 678, 680 ff production 32, 676 Energy policy 17 Oil crop production 135 ff Rape biodiesel 30 ff, 484, 495, 680 European Biodiesel Board (EBB) 11, 32, 680, 682, 687 Extraction 91 ff, 170, 184 Reactive 310 ExxonMobil 19, 532, 759 ff, 768 Fallow croplands 54 ff, 155, 633 FAME, See Biodiesel Fats 62, 198, 200 ff Market segments 51 Transesterification 476 Fat-to-biodiesel 386 Fat-to-liquids 761 Fatty acids 63 Biosynthesis 65 ff

830

Index

Nomenclature 63, 73 Fatty acid salts 339, 401, 495, 731 ff Feedstock 130 ff Analytics 515 Composition 131 ff product yield 295 Control 466 Cost 253, 310, 474, 658 ff Impurities 293, 388 Normalisation 738 Quality 322 control 515, 533 ff Selection 386, 462, 467 Fermentation 740 Fertiliser program 264 Fertilisers 177 Field pennycress (T. arvense) 266 Finland 682, 752, 765 Fischer Tropsch 596, 725 ff, 748 Diesels 726 FT-BTL 728, 769 FT-GTL 759 Synthesis 596, 758 Fish oil 62, 82, 163 ff Biodiesel 167 Fatty acid profile 164, 166 Transesterification 410 Fish wastes 167, 739 Flash point 561 Setaflash 562 Flax(seed) (L. usitatissimum) 93, 97, 156 Flexible-fueled vehicles 27 Food security 53 Food vs. fuel debate 636, 786, 798 Fossil fuels 3, 699, 714, 758 ff, 767 Consumption 3 Production 3 Fractionation 154, 648 France 172, 685 Biodiesel industry 30 ff, 463, 498, 678, 682 Institut Français du Petrole (IFP) 19, 354, 401, 495 ff, 501, 603, 613, 726, 729 ff, 759 Free fatty acids (FFAs) 155 Contents 386 Lipase-catalysed esterification 442 Pre-processor 396 Fuel economy 641, 653

Fungi 187 Furanics 720 Gas-to-liquid (GTL) technologies 758 ff, 762, 768 Genetic engineering 56, 78 Technology goals 59 Germany 678, 681 ff, 764 ff Biodiesel production 30 ff, 33, 681 ff CD Connemann 38, 490 ff, 500, 678 Potential energy crops 267 Taxation 32, 681 Glyceric acid 586 Glycerine-to-methanol (GtM) 587 ff Glycerol (glycerine) 571 ff, 797 Acetalisation/ketalisation 604 biofuels 604 Analysis (bound, free, total) 543 ff, 553 Animal feed 584 Biodiesel by-product 575 Carbonate 607 Carboxylation 607 Chemistry 576 Chlorination 605 ff epichlorohydrin 605 ff Content 543 ff, 553 Dehydration 593 ff acrolein 593 ff 3-hydroxypropionaldehyde 593 polyglycerols 594 Etherification 602, 613 glycerol polyethers 604 glycerol tert-butyl ethers (GTBEs) 602 polyglycerols 605 solketal tert-butyl ether (STBE) 602 Fermentation 574, 584, 607 biobutanol 609 bioethanol 609 propanediols 610 Fuel additives 586, 602 ff Glut 574, 611 ff, 745 Grades 575 high-purity 410 kosher 577 Heat source 580 Hydrogenolysis 587 ff ethylene glycol 587 methanol 587

Index 1,3-propanediol 587 ff propanol 588 ff propylene glycol 587 ff, 591 Industrial use 579 ff Innovative use 584 ff Oligo/polymerisation 605 polyglycerol esters (PGEs) 605 Production 574 Product value 571, 582 ff Purification 575 ff Ambersep ™BD50 process 579 Pyrolysis/gasification 594 ff aqueous-phase carbohydrate reforming 597 ff liquid alkanes 596 Refinement 472 Selective oxidation 586 Synthesis routes 572 (Trans)esterification 600 ff (poly)glycerol esters 600 Valorisation 571 ff Glycidol 607 GM crops 57, 80 Europe 58 USA 59 Green chemistry 795 Green Diesel 746 Greenhouse gas (GHG) emissions 7, 59, 631 ff, 635, 651, 720, 722, 747, 791 Groundnut, See Peanut H-BIO process technology 755 Heating oil (biodiesel as) 641, 678 Hempseed (C. sativa) 83, 254, 267 Henkel 337, 406, 409, 488 ff Heterogeneous acid catalysis 364 ff Cation-exchange resins 368 Heteropolyacids 369 Mesoporous silica 367 Montmorillonite 368 Nafion 367 ff Pillared clays 369 Superacids 370 Transesterification 364 ff Zeolites 369 Heterogeneous base catalysis 311, 348 ff, 356 ff Anionic-exchange resins 363

831

Carbonates 360 Hydrotalcites 359 Hydroxides 358 Mesoporous catalysts 362 Oxides 358 ff Transesterification 348 ff, 356 ff Zeolites 360 ff Homogeneous acid catalysis 300, 325 ff, 340 Brønsted acids 341 Esterification 346 Organosulphonic acids 341 Reactions conditions 342 ff Transesterification 339, 344 effect of water 346 Homogeneous base catalysis 323, 327 ff, 338, 474 ff Alkali hydroxides 327, 332 ff Alkaline carbonates 336 Alkoxides 327, 333 ff Alkylguanidines 327 Reactions conditions 330 ff, 336 Transesterification 323, 327 ff, 338 Humicola lanuginosa 444 Huntsman Corp. 593, 607 Hybrid diesel fuels 123 ff Hydrodiesel 614, 726, 743 ff Hydrogen economy 4 Hydrolysis-(trans)esterification 308, 313 Hydroprocessing technology 742 ff, 747 Ecofining™ 747, 753 ff H-BIO 748, 755 Hydrodiesel 743 ff Hydrotreated vegetable oil (HVO) 743 ff, 789 NExBTL 747 ff Hydrotalcites 359 Hydroxyl value (HV) 242 IATA 678 Iberian dragonhead (L. iberica) 156 Ignition quality 243 Ignition Quality Tester (IQT™) 235, 521 Immobilised biocatalysts 446 ff Esterification 446 Transesterification 448 Immobilised lipases 446 ff Biocatalysis 446 ff

832

Index

Lipozyme 442 Novozym 442 T. lanuginosa 442 India 245 ff Agricultural policy 56 Biodiesel industry 700 Biotech crops 57 Energy policy 16, 700 Potential energy crops 159, 245 ff Vegetable oils 191, 226, 665 Indonesia 251, 700 Biodiesel industry 700 ff Energy policy 16 Palm oil 250 Industrial crops 130 ff, 226 ff Utilisation 53 Institut Français du Petrole (IFP) 19, 354, 603, 613, 726, 729 ff, 759 Esterfip 495 Esterfip-H™ 401, 495, 501, 579, 729 ff Heterogeneous catalysts 354, 401, 726 Interesterification 286, 442, 581, 612 Intersolubility 298 Iodine value (IV) 232 ff, 525 Ion-exchange resins 363, 368 IR biodiesel analysers 536 ff Isis (Brassica spp.) 268 Italy 270 ff Biodiesel industry 30 ff, 678 Potential energy crops 270 ff Japan 251 Biocatalysis 435 Energy policy 16 Waste vegetable oils 138, 199, 482 Jatropha curcas 117, 192 ff, 246, 254, 411 Biodiesel 412 ff, 655, 700 standards 517 Blends 122 Energy crop 193, 724 Energy system 118 Enzymatic transesterification 441 Multipurpose use 193 Oil extraction 97 Plantation projects 195, 257, 263, 265, 413, 700 Transesterification 331 Jatropha-palm biodiesel blend 645, 655 Jet fuel 419, 678, 755, 761

Jojoba (S. chinensis) 84, 97 Karanja (Pongamia pinnata) 192, 226, 246, 305 Oil 117, 411 Karl Fischer 522 Kenaf (H. cannabinus) 247 Kinetics 295 Acid-catalysed 296, 339 Base-catalysed 296, 337 Intersolubility 298 Process intensification 299 ff Krill oil 84 Kukui nut (A. moluccana) 82, 265 Kyoto Protocol 7, 653 Land use 633 Lard 62, 64, 198, 202 Transesterification 402 Latin America 255 ff Drivers for biodiesel 262 Potential energy crops 255 ff Legislation, biodiesel related 7 ff Lesquerella 76, 78, 87, 267, 269, 791 Life cycle assessment (LCA) 630 ff Land use 631 Palm biodiesel 633 Rape biodiesel 632 Rendered fats 657 Soy biodiesel 699 Limnanthes, See Meadowfoam Linola 156 Linolenic acid 71, 74, 152, 156, 243 Methyl ester 243 analytics 525, 545 Linseed (L. usitatissimum) 156 Oil 82 ff, 644 Lipases 435 ff Catalysis 435 ff esterification of free fatty acids 435 ff transesterification of triglycerides 435 ff Inactivation 437 Inhibition 437 Specificity 443 Lipid biosynthesis 64 ff Environmental factors 74 Lipid metabolism 64 ff

Index Lipozyme 442, 448, 450 Low-cost feedstocks 197 ff Rendered oils and fats 198 Used cooking oils 198 US production 204 Low-viscosity formulations 121 ff Blending 121 Derivatisation 121 Dilution 121 Microemulsification 121 Pyrolysis/gasification 121 Lubricity 22, 640, 677, 693 Lupin (L. mutablis) 83, 271 Macroalgae 185 ff Mahua (Madhuca indica) 192, 226, 246, 411 Transesterification 411 Malaysia 38, 700 ff Biodiesel industry 31, 38, 250, 700 ff Energy policy 16 MPOB (PORIM) 122, 408 Palm oil 250 Petronas 19 Market acceptance 514, 518, 657, 677 ff, 688, 796 ff Fuel quality 514 Mathematical symbols 810 ff “McDiesel” 465 Mcgyan biodiesel process 358, 402 ff, 423, 671, 728 Meadowfoam (Limnanthes spp.) 79, 267 Oil 239 Meal (cake) 92, 95, 151, 164, 665 Metal alkoxides 293, 296, 327, 333 ff, 389 Methanol 288, 291 ff Content 525, 561 Poisoning 436 Supercritical 305, 307, 311 ff Synthesis 587 Tolerance 438 Methanolysis 288 Effect of methanol content 437 Supercritical 305, 311 ff Methyl acetate 440, 611 ff Microalgae 168 ff Classes 169 Growth 175 heterotrophic 175

833

mixotrophic 175 photosynthetic 175 Oil 170, 174, 182 biocatalytic transesterification 445 biodiesel 171, 414 ff content 172 fatty acid profile 172 Technology 174 ff fermentation 175, 184 open ponds 175 ff photobioreactors 175, 177 ff raceways 175 ff Microbial oils 187 Microdiesel 740 ff Microemulsions 23, 124 Microorganisms 187 Microwave Accelerated Reaction System (MARS) 469 Microwave-enhanced reactions 300 ff Milkweed (A. syriaca) 266 Miscibility 122, 327 M. miehei 446 Monoglycerides 286, 291, 327, 333, 483, 600, 614 Monsanto 58 Moringa (M. oleifera) 162, 246, 792 Multi-feedstock 468, 482, 486, 663, 666, 690 ff, 732 Technology (MFT) 388, 495, 732 Mustard 145 ff, 244, 263, 792 Myco-diesel 725 Nahor (Mesua ferrea) 247 Oil 117 Nameplate capacity 465, 500, 678, 680, 682, 688 National Biodiesel Board (NBB, USA) 14, 519, 530, 626 National Chemical Laboratory (NCL, India) 356, 613, 726, 728 ENSEL™ 356, 604, 613, 726, 728 Natural gas 4 Near infrared (NIR) spectroscopy Applications 79 biodiesel 552 ff Technology 533 Neem (Azadirachta indica) 192, 226, 247, 411 Neste Oil 19, 614, 649, 687, 701, 747 ff

834

Index

Netherlands 3, 15, 272, 752 Biodiesel industry 31, 682, 687 NExBTL Renewable Synthetic Diesel 649, 651, 687, 701, 746, 748 ff Nitrogen oxides emissions 76, 233, 236, 635, 651, 653, 655, 658 Nomenclature 801 ff Non-edible oils 143, 188 ff Non-ester renewable diesel (NERD) 725 Non-food crops 52 Industrial use 54 North America 33 ff, 688 ff Potential energy crops 264 Norway 3, 167, 682, 765 Nova Biosource Technologies 408, 410, 691 Novasep 578 Oehlmühle Leer Connemann 38, 490 ff, 500, 678 OEM warranties 518, 524, 657, 796 ff Oilcrops 130 ff, 226 ff Agronomic potential 244 Emerging 268 Production 135 Europe 135 globally 136 Productivities 230 Oil palm 153, 263 Global fruit production 56 Oil processing techniques 90 ff Bleaching 100 Dehulling 91 Deodorisation 100 Enzymatic hydrolysis 91 Extraction 91, 310 Mechanical pressing 93, 170 Mixed mechanical/solvent extraction 96 Novel extraction techniques 97 ff Rendering 90 Solvent extraction 94, 170 Sterilisation (‘cooking’) 91 Supercritical fluid extraction 97, 170 Oilseeds 130 ff Fatty acid variants 148 ff Oleic acid 69 Olein 122, 154 Oleochemical sources 62

Olive (O. europaea) oil 65, 79, 82, 93, 159, 644 Alcoholysis 335 Lipase-catalysed methanolysis 445 Oscillatory flow reactor (OFR) 484 Overcapacity 676, 679, 693 Oxidation stability 237 ff Classification 239 Index (OSI) 238 ff, 558 Storage stability 238 Testing 555 ff PDSC 556 peroxide value 557 PetroOXY test 556 photochemiluminescence 238 Rancimat™ test 238, 556 Yellowness index (YI) 238, 557 Thermal stability 238 Unsaturated fatty acids 239 Ozonation 23, 26, 614, 647 Palatase 20000L 450 Palm fruit 65, 94 In-situ transesterification 309 Palm kernel 93, 95, 153 Palm oil 79, 82, 122, 153 ff Biodiesel 38, 155, 250, 636, 655, 664 Colombia 257 Indonesia 250, 700 Malaysia 38, 156, 700 Ethyl esters 155 Fractionation 154 RSPO 156, 250 Palm olein 122, 154 Pangasius (P. hypophtalmus) oil 167 Paris Exposition 114, 158 Particulate emissions 651 ff Peanut (A. hypogaea) 158, 257, 263, 692 Oil 97, 114, 257 Pecan oil (C. illoensis) 70 ff, 97, 259 Penicillium camembertii 442 Perilla 83 Permaflo biodiesel 648 Peroxide value (PV) 557 Petrobras 19, 264, 696, 747 ff, 755 Petrodiesel fuel 22 Petronas 19, 408 Philippines 38 Coconut biodiesel 251, 630, 637

Index Energy policy 16 Photobioreactors 177 ff Photochemiluminescence 238 Physical symbols 810 ff Physic nut, See Jatropha curcas Pilinut (C. ovatum) 247 Pioneer 58 Pistachio (P. chinensis) 254 Plants 130 ff, 226 ff Biology 76 fatty acid synthesis 65 ff Biotechnology 173 GM techniques 56, 78, 148 ff mutation breeding 77, 148 ff plant breeding 56, 77, 148 ff Economic value 50 Metabolism 64 ff Water supply 790 Plug-flow reactor (PFR) 332, 483 ff Polyglycerol esters 605 Polyunsaturates (PUFAs) 62, 70, 165, 231, 239, 244, 525, 643 ff Analytics 547 Poppyseed (P. somniferum) 163 Potassium hydroxide 293, 296, 327, 332, 334 ff, 338 Pour point (PP) 637, 642 P.R. China 115, 191, 252 ff Algae 419 Biodiesel 31 cost 253 forests 254 industry 252, 699 ff Biotech crops 57 Energy policy 16, 699 Glycerol 574 Oilseed imports 663 Potential energy crops 84, 252 ff Pre-esterification 326, 346, 405, 409 Acid-catalysed 476, 478 Pre-treatment 197, 203, 388, 405, 665, 765, 766 Glycerolysis 408 Prions 202 Probiodiesel 16, 256, 695 Process Control (PC) 532 ff, 535 at-, in-, on-line 533 test kits 533, 538

835

Intensification 299 ff co-solvents 305 dynamic turbulence 303 ff microwave enhancement 300 ff sub/supercritical reaction media 306 ff ultrasonics 302 ff Technology 462 ff Product Quality (PQ) 530 ff control 535 ff Yield 294 feedstock composition 295 1,2-Propanediol 589, 610 1,3-Propanediol 589, 610 Propylene glycol 589 ff Prototec 486 Pseudomonas cepacia 438 ff, 442, 449 Pseudomonas fluorescens 439, 442, 448 Pumpkin seed (C. maxima) 163 Oil 252 Purification technology 471 ff Amberlite™ BD10 Dry™ 472 Dry wash 472 Glycerol refinement 472 Magnesol® D-Sol 472 Pyrolysis 23 ff Oil 121, 718 Quality Assurance (QA) 468, 514 ff Control (QC) 514 ff Indexes 231 anisidine value 231 free fatty acid content 231 peroxide value (PV) 231 phosphorus content 231 Management (QM) 526 AGQM (Germany) 528 BQ - 9000 (USA) 530 ExxonMobil 532 REG® (USA) 532 Surveys 528 ff AGQM 528 NREL 528 ff UFOP 528 WHOI 529 Rancidity 91

836

Index

Rapeseed (Brassica spp.) 144 ff, 664 Biodiesel (RME) 30 ff, 288, 313, 484, 644, 655 aging 557 life cycle assessment 632 storage stability 650 Processing 150 Reactant purity 293 Free fatty acids 293 Phosphorus content 293 Unsaponifiables 293 Water 293 Reactive distillation 371, 410, 469 Recycled oils 37, 197 Biodiesel 251, 449, 657 REG® specification 532 Regulatory agencies 539 Rendering 167 Oils/fats 198, 692 Renewable energy 4 ff, 20, 772 Renewable Energy Act (Germany) 12 Renewable Energy Directive (EU) 11 Renewable Fuels Standard (USA) 13, 692, 758 Renewable Transport Fuels Obligation (UK) 11, 684, 769 RepCat technology 401, 495, 731 ff Rice bran oil 82, 95, 97, 160, 401 In-situ transesterification 309 Methanolysis 341, 401 R. miehei 442, 446 Rohm & Haas Co. 363 ff, 368, 388, 391, 472, 578, 726, 732, 734 R. oryzae 438, 440 Roundtable on Sustainable Palm Oil (RSPO) 156, 250, 752 Royal Dutch Shell 19, 21, 420, 498, 573, 589 ff, 759, 762, 764, 766, 768 R. rhizopodiformis 443 Alcoholysis 443 Rubber seed (H. brasiliensis) oil 189 Rudolf Diesel 114 Sacha inchi (P. volubilis L.) 262 Safflower (C. tinctorius) oil 82, 119, 157 Transesterification 448 Sal (Shorea robusta) 192, 226, 246 Salicornia (S. brachiata) 247 Alcoholysis 450

Salmon (S. salar) oil 166 ff, 739 Saponification number (SN) 231, 233 Sasol 759 ff Scotland 204, 685 Argent Energy 204, 498 ff Biodiesel producers 204, 498 ff Rape biodiesel 627 ff Seashore mallow (K. virginica) 266, 692 Selective hydrogenation 736 ff Fish waste oils 739 Highly unsaturated feedstock 736 Tall oil 739 Sesame (S. indicum) oil 82, 162 Set-aside regulations 54 ShockWave Power™ reactor (SPR) 303, 469, 725 Simarouba (S. glauca) 246 Simultaneous esterification/ transesterification 399 ff, 478 Commercial technologies 400, 410 Critical fluid medium 399 Heterogeneous acid catalysis 399 Homogeneous acid catalysis 399, 478 Singapore 172 ff, 614 Canola biodiesel 251 Energy policy 16 Renewable diesel industry 701, 752 NExBTL diesel 251, 701, 752 Single-cell oils 187, 444 Slurry catalyst 729 Soapstock 97, 205 Biodiesel 666 Lipase-catalysed esterification 452 Transesterification 345, 398, 402, 409, 420 ff Sodium hydroxide 293, 296, 327, 332 ff, 338 Soladiesel 419, 497 Solin 156 Solvay 575, 605 ff Solvent-assisted methanolysis 305 ff Solvent properties (of biodiesel) 640 South-East Asia 250 ff Biodiesel industry 505, 700 ff Deforestation 156, 701 Exports 687 Potential energy crops 250 ff RSPO 156, 250 Southern Europe 267

Index Potential energy crops 267 Soybean (G. max) 54, 57, 95, 97, 151 ff, 664, 697 Acid oil 423 Food use vs fuel use 636 In-situ transesterification 309 Transesterification 337 World production 55 Soy biodiesel (SEE, SME) 33 ff, 37, 54 ff, 256, 297, 644, 655, 664 Spain 682 Biodiesel industry 685 ff Spectroscopy 549 ff Mid-IR 550 ff NIRS 552 ff NMR 555 Raman 555 UV-VIS 544 Splash-and-dash 15, 687 Standards 517, 560 Statoil 167, 759 ff Stearin 154 Steryl glycosides (SGs) 522 ff, 657 Storage stability 238 ff, 649 Additivation 241 Straight vegetable oils 114, 124 Structure indexes 231 ff Cetane number (CN) 231, 234 ff, 520, 525, 532, 551, 639 Hydroxyl value (HV) 231 Iodine value (IV) 231 ff, 525 Oil stability index (OSI) 231, 238 ff, 558 Saponification number (SN) 231, 233 STT (Spinning tube-in-tube) technology 304, 469, 725 Sub/supercritical reaction media 305 ff Enzyme catalysed reactions 441 Supercritical carboxylate esters 308 Supercritical methanolysis 305 ff, 312 Subsidies/tax exemptions 14, 29, 32, 36 Sulphuric acid 300, 341 SunDiesel 764 Sunflower (H. annuus) 76, 96, 122, 150, 310, 664 Biodiesel 150 In situ transesterification 309 Transesterification 335 Super-biodiesel 251

837

SuperCetane 743 Supercritical fluid extraction (SFE) 97 Supermethanol 572, 588 Sustainability 80, 625 ff, 790 Sustainable agriculture 59, 156, 636, 701, 786 Sustainable biodiesel 498 Sustainable Biodiesel Alliance 80, 626 Symbols 810 ff Syntroleum 759 ff Sweden 3, 27, 682, 764 ff Switchgrass 724 TAG, See Triacylglycerol Tall oil 198, 205, 267, 306, 423, 743 Biodiesel 423 ff, 665 Selective hydrogenation 739, 743 Transesterification 402, 423 Tallow 62, 198, 201 ff, 204, 387, 787 Biodiesel (TME) 498, 500, 643 Quality parameters 516 Transesterification 405, 410, 476, 498, 500 Tax incentives 14, 29, 32, 36, 204, 681, 697 ff, 701 TBK biodiesel 581, 611 Tea seed (C. sinensis) oil 163 Technology providers 467, 487 ff, 659 Testing laboratories 539 Test kits 533, 538 Thermal stability 238 Tigernut (C. esculentus) 159, 255, 263 Oil 117, 159 Total 19, 498, 720 Toxicity 635, 639, 641 Traceability 636 Transesterification 22, 285 ff, 322 ff Acid-catalysed 325 ff, 340 ff, 364 ff, 394 ff Acidic feedstocks 394 ff High-FFA oils, etc. 306, 336, 345, 389, 396, 473, 731 ff multi-stage catalytic processes 403 ff simultaneous esterification/ transesterification 399 ff, 732 Alcohol/oil molar ratio 291 ff, 331 Base-catalysed 323, 327 ff, 356 ff, 395, 474 ff

838

Index

Biocatalytic (enzyme catalysed) 435 ff, 443 Catalysts 293, 322 ff, 386 ff, 434 ff Co-solvent effect 305 Critical fluid medium 399 ff Dynamic turbulence 303 ff Heterogeneous catalysis 301, 348 ff, 446 ff Homogeneous catalysis 300, 327 ff In-situ 308 ff Kinetics 295 ff, 337 variables 295 Low-FFA oils 323, 389 Mechanism 327, 330, 341 Metal-based catalysis 338, 352 ff dual-metal catalysts 356 organometallics 353 ff transition metal compounds 354 ff Microwave-enhanced 300 ff, 470 Monophasic 292, 298, 305, 400 Multistage catalytic processes 403 ff Non-catalytic 310 supercritical methanol 311 ff Pre-treatment 388, 395 Process technology 452, 462 ff, 465 ff, 468 BDI 400, 420, 493, 495, 498 ff, 731 BIOX Corp. 493 CD Connemann 38, 490 ff, 500 Desmet Ballestra 495, 504, 659 Henkel 337, 406, 409, 488 ff IFP - Axens 354, 495 ff, 501, 726, 729 ff Lion Corp. 488 Lurgi 493 ff Nova Biosource Technologies 408, 410 Pacific Biodiesel 497 Process variables 287, 331 alcohol/oil molar ratio 291 ff, 331 catalyst (concentration) 292, 332, 336 mixing 294, 332 nature of alcohol 288 ff nature of glyceride 287 pressure 331 product yield 294 ff reactant purity 293 reaction temperature 287, 331

reaction time 331 Reaction media 440 supercritical methanolysis 311 ff Solid-acid catalysis 364 ff cation-exchange resins 368 heteropolyacids 369 mesoporous silicas 367 montmorillonite 368 Nafion 368 pillared clays 369 reaction conditions 365 superacids 370 zeolites 369 Solid-base catalysis 311, 348 ff, 356 ff anionic exchange resins 363 carbonates 336, 360 hydrotalcites 359 hydroxides 358 mesoporous catalysts 362 ff oxides 358 ff reaction conditions 350 zeolites 360 ff Solvent effect 441 Ultrasonication 302 ff, 310, 477 Water effect 441 Trap grease 199 Transesterification 398, 410 Tree-borne oils 245 Transesterification 411 Triacetylglycerol 440 Triacylglycerol 286 Biosynthesis 70 ff Tricaprin 79, 85, 124, 788 Tricaproin 79, 85, 124, 788 Tricaprylin 79, 85, 124, 788 Triglycerides 64, 286 Analysis 515 ff Classification 85 Hydrolysis 312 Hydrolysis-(trans)esterification 313 Transesterification 22, 285 ff, 322 ff, 386 ff, 434 ff Trimethylolpropane triesters 446 Tung (Aleurites spp.) oil 82, 84, 115, 241, 245 Tyson 747 ff, 761 UFOP (Union for Promotion of Oil and Protein Plants) 528, 684

Index UK 33 Biodiesel industry 682 ff Davy Process Technology 592 Potential energy crops 267 Renewable Fuels Agency 18 Ultrasonication 302 ff, 310, 477, 481 Undi (C. inophyllum) 247 Unrefined oils 98 ff, 386 ff Biodiesel 386 ff Unusual fatty acids 85 Biosynthesis 70, 72 Halogenated 87 Oxygenated 87 Unsaturated 87 UOP LLC 747, 753 ff, 767 USA 33, 264 ff, 688 ff Alaska 167 Arizona 179 Biodiesel 31, 33 ff, 36 feedstocks 33 ff, 203, 692 investment costs 659 markets 688 ff nameplate capacity 37, 465 plants 36, 464, 678, 688 ff plant size 464, 468, 497, 688 Bioethanol 26, 692 Biomass 54 Biotech crops 57 Colorado 523 Energy and Tax Extenders Act 688 Energy policy 17 Exports 15, 36, 677, 687, 785 Hawaii 172, 265 Idaho 119 Iowa 689 Minnesota 11, 146, 522 ff, 530, 657, 690 Montana 265 North Dakota 146, 691 Nova Biosource 408, 410, 691 Oregon 673 Pacific Biodiesel 497 Rohm & Haas Co. 363 ff, 368, 388, 391, 472, 578, 732, 734 Selection criteria 265 South Carolina 765 Soy biodiesel 33 ff, 37, 55, 151 ff, 644, 655, 690 Splash-and-dash 15, 687

839



Tax incentives 14 ff, 29, 36, 204, 688 Texas 463, 689 UOP LLC 753 ff, 767 Virent Energy Systems, Inc. 593, 596 ff, 599 Waste cooking oil 37, 690 Used cooking oil 198, 336, 387, 665 Biodiesel 200, 498, 643, 657 exhaust emissions 651 Transesterification 336, 476, 488, 497 ff Vegetable oil/diesel blends 122 Vegetable oils 62 ff, 114 ff, 130 ff, 226 ff Aroma 74 Biofuel technology 125 Biosynthesis 65 ff Catalytic cracking 23 Classification 83 Comparison to mineral oils 52, 119 Cost 141, 253, 310, 474, 658 ff Deacidification 100, 155, 388 Engine performance 120 Fatty acid profiles 131 ff Fuel properties 116 Global trade 136 Homogeneous-catalysed transesterification 293, 327 ff, 340 ff, 578 Hydrogen facilities 747 Hydrotreated (HVO) 742 ff, 789 Industrial use 80 Microemulsions 23, 124 Oil content 92, 515 OSI values 238 Ozonation 23, 26, 614, 647 Processing 90 Producers 142 Production 135 Pyrolysis 23 ff Quality parameters 515 Resources 135 ff Selection criteria 130, 265 Viscosity 23 Verenium Corp. 766 Vernonia (V. galamensis) 78, 80, 88, 263, 267 Vietnam 167 Virent Energy Systems, Inc. 593, 596 ff, 599

840

Index

Virtual acres 58, 136 Viscosity 23, 114 ff, 121 ff, 522, 561, 655

Winterisation processing 645, 648 Winterising agents 646

Waste restaurant grease 200 Biocatalytic transesterification 445 Waste vegetable oils 138, 387 Biodiesel production 482, 497 Transesterification 335 Water supply 790 Plant growth 52 Websites 820 ff Whole-cell biocatalysts 453 Whole-cell microorganisms 434

Yam bean (Pachyrhizus spp.) 259 Yeasts 187 Yellowdiesel process 469, 579 Yellow grease 199 ff, 665 Transesterification 200, 402, 410 Yellowhorn (X. sorbifolia) 254 Yellowness index (YI) 238, 557 Zeolites 360 ff, 367