Biofuels Production E-Book

Vikash Babu

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 572

Veröffentlichungsjahr: 2013

Beschreibung

The search for alternative sources of energy to offset diminishing resources of easy and cost-effective fossil fuels has become a global initiative, and fuel generated from biomass is a leading competitor in this arena. Large-scale introduction of biofuels into the energy mix could contribute to environmentally and economicaly sustainable development on a global scale. The processes and methodologies presented in this volume will offer a cutting-edge and comprehensive approach to the production of biofuels, for engineers, researchers, and students.

Leseprobe

Contents

Cover

Half Title page

Title page

Copyright page

Dedication

Preface

List of Contributors

Chapter 1: Introduction to Biofuels

1.1 Global Scenario of Biofuel Production and Economy

References

Chapter 2: Advances in Biofuel Production

2.1 Introduction

2.2 Advances in the Production of First, Second and Third Generation Biofuels

2.3 Future Trends of Biofuels Development

2.3 Conclusions

Acknowledgements

References

Chapter 3: Processing of Biofuels

3.1 Introduction

3.2 Biodiesel from Algae

3.3 Cellulosic Ethanol

3.4 Syngas

3.5 Conclusion

References

Chapter 4: Bioconversion of Lignocellulosic Biomass for Bioethanol Production

4.1 Introduction

4.2 Bioethanol Production Process

4.3 Genetic Engineering for Bioethanol Production

4.4 Future Perspective

References

Chapter 5: Recent Progress on Microbial Metabolic Engineering for the Conversion of Lignocellulose Waste for Biofuel Production

5.1 Introduction

5.2 Role of Genetic and Metabolic Engineering in Biofuel Production

5.3 Problems with Different Biofuels and Areas of Improvement

5.4 General Process of Metabolic Engineering

5.5 Metabolic Engineering in Different Microorganisms

5.6 Conclusion

References

Chapter 6: Microbial Production of Biofuels

6.1 Introduction

6.2 Types of Biofuels Produced Through Microorganisms

6.3 Future Prospects and Conclusion

References

Chapter 7: Microalgae in Biofuel Production-Current Status and Future Prospects

7.1 Introduction

7.2 Microalgae in Biofuel Production

7.3 Comparison of Cyanobacteria with Microalgae in Biofuel Production

7.4 Applications of Cyanobacteria and Microalgae in Biofuel Production

7.5 Selection of Microalgae for Biofuel Production

7.6 Cultivation of Microalgae for Production of Biofuel and Co-Products

7.7 Harvesting and Drying of Microalgae

7.8 Processing, Extraction and Separation of Microalgae

7.9 Biofuels and Co-Products from Microalgae

7.10 Challenges and Hurdles in Biofuel Production

7.11 Genetic and Metabolic Engineering of Microalgae for Biofuel–Bioenergy Production

7.12 Conclusion and Future Prospectus

References

Chapter 8: Bioethanol Production Processes

8.1 Introduction

8.2 Global Market for Bioethanol and Future Prospects

8.3 Overall Process of Bioethanol Production

8.4 Production of Sugars from Raw Materials

8.5 Characterization of Lignocellulosic Materials

8.6 Sugar Solution from Lignocellulosic Materials

8.7 Basic Concepts of Fermentation

8.8 Conversion of Simple Sugars to Ethanol

8.9 Biochemical Basis for Ethanol Production from Hexoses

8.10 Biochemical Basis for Ethanol Production from Pentoses

8.11 Microorganisms Related to Ethanol Fermentation

8.12 Fermentation Processes

8.13 Ethanol Recovery

8.14 Distillation

8.15 Alternative Processes for Ethanol Recovery and Purification

8.16 Ethanol Dehydration

8.17 Distillers’ Dried Grains with Solubles

8.18 Sustainability of Bioethanol Production

8.19 Concluding Remarks and Future Prospects

References

Chapter 9: Production of Butanol: A Biofuel

9.1 Introduction

9.2 Butanol and its Properties

9.3 Butanol as Fuel

9.4 Industrial applications of Butanol and its Derivatives

9.5 Methods for Production of Butanol

9.7 Future Prospects

References

Chapter 10: Production of Biodiesel from Various Sources

10.1 Introduction

10.2 Sources/Feedstocks for the Production of Biodiesel

10.3 Various Processes of Biodiesel Production

10.4 Determination of Yield, Process Optimization and Biodiesel Standardization

10.5 Conclusion

References

Chapter 11: Bio-Hydrogen Production: Current Scenarios and Future Prospects

11.1 Introduction

11.2 Conventional Methods of Hydrogen Production

11.3 Hydrogen from Renewables Sources

11.4 Methods of Hydrogen Production through Bio-Routes involving Biochemical Processes

11.5 Recent Advancement in Production of Bio-Hydrogen

11.6 Status of Biohydrogen Production

11.7 Conclusions

References

Chapter 12: Biomethane Production

12.1 Introduction

12.2 Features of Biomethane

12.3 Global Scenario of Biomethane

12.4 Biomethane Production – Waste to Fuel Technology

12.5 Biogas Cleaning and Upgrading

12.6 Conclusions

References

Index

Biofuels Production

Scrivener Publishing 100 Cummings Center, Suite 541J Beverly, MA 01915-6106

Publishers at Scrivener Martin Scrivener ([email protected]) Phillip Carmical ([email protected])

Copyright © 2014 by Scrivener Publishing LLC. All rights reserved.

Co-published by John Wiley & Sons, Inc. Hoboken, New Jersey, and Scrivener Publishing LLC, Salem, Massachusetts. Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, [phone], fax [phone], or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, [phone], fax [phone], or online at http://www.wiley.com/go/permission.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.

For general information on our other products and services or for technical support, please contact our Customer Care Department within the United States at [phone], outside the United States at [phone] or fax [phone].

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic formats. For more information about Wiley products, visit our web site at www.wiley.com.

For more information about Scrivener products please visit www.scrivenerpublishing.com.

Library of Congress Cataloging-in-Publication Data:

ISBN 978-1-118-63450-9

For my loving son, Daksh, on his first birthday -Vikash Babu

Dedicated to my Wife, Dev, Subh, Family & Friends -Ashish Thapliyal

For my loving parents -Girijesh Kumar Patel

Preface

“Anybody who has been seriously engaged in scientific work of any kind realizes that over the entrance to the gates of the temple of science are written the words: ‘Ye must have faith.”

Max Planck

The true sign of intelligence is not knowledge but imagination.

Albert Einstein

Biofuels is an emerging area for research now a day because existing fossil fuels are likely to diminish within few years and many governments would like to reduce their dependence on fossil fuels. Hence, developing biofuels and alternative energy sources is among the priority of many nations. In the present scenario, the need of hour is to utilize latest scientific approaches and amalgamate them with proper utilization of natural resources and then the technology can impact the life of common man. New technological intervention requires effective co-ordination between different organizations like Universities, Academic Colleges, Research institutions, Government Agencies, Non-governmental Organization and people participation, the end users of technology. This book is an effort to provide latest information on recent scientific methodologies involving biofuel.

Lots of research papers and review articles are available on the internet covering different type of biofuels. It is difficult to comprehend those developments in a single review article. Therefore, there is a need to collect scattered information in a single book with recent advancements.

Each chapter in this book is contributed by experts of their field. In this book, methods of biofuels production such as biodiesel, biomethane, Bioethanol, Biobutanol and Biohydrogen production have been summarized. Apart from production methods, their global scenario, recent advancements, processing, microbial metabolic engineering for biofuel production and role of micro-organisms in biofuels production, have been well summarized. By all the efforts of contributors, this book will be very helpful for all the graduate, post graduate students and researchers who are working in this area.

The editors are thankful to all the contributors for their cooperation. Finally the authors solicit suggestions for improvement and enlargement of this book from the researchers, students and readers.

Vikash Babu Ashish Thapliyal Girijesh Kumar Patel

List of Contributors

Vikash Babu Department of Biotechnology, Graphic Era University, Dehradun-248002, India

Girijesh Kumar Patel Department of Biotechnology, Graphic Era University, Dehradun-248002, India

Ashish Thapliyal Department of Biotechnology, Graphic Era University, Dehradun-248002, India

M.D. Berni Interdisciplinary Centre of Energy Planning, State University of Campinas – UNICAMP, Brazil.

I.L. Dorileo Interdisciplinary Centre of Energy Planning, Federal University of Mato Grosso - UFMT, Brazil.

J.M. Prado LASEFI/DEA/FEA (School of Food Engineering) / UNICAMP (University of Campinas), R. Monteiro Lobato, 80, Campinas, 13083-862, SP, Brazil

T. Forster-Carneiro LASEFI/DEA/FEA (School of Food Engineering) / UNICAMP (University of Campinas), R. Monteiro Lobato, 80, Campinas, 13083-862, SP, Brazil

M.A.A. Meireles LASEFI/DEA/FEA (School of Food Engineering) / UNICAMP (University of Campinas), R. Monteiro Lobato, 80, Campinas, 13083-862, SP, Brazil

Pramod Kumar Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee-247667 (India)

Divya Gupta Department of Biotechnology, G. B. Pant Engineering College, Pauri Garhwal, Uttrakhand-246001, India.

Ajeet Singh Department of Biotechnology, G. B. Pant Engineering College, Pauri Garhwal, Uttrakhand-246001, India.

Ashwani Sharma Computer-Chemie-Centrum, Universität Erlangen-Nürnberg Nägelsbachstr. 25, 91052 Erlangen, Germany.

Anshul Nigam IPLS (renamed as BUILDER), Pondicherry University, Puducherry-605014, India.

Virendra Kumar Institute of Genomics and Integrative Biology, Mall Road, Delhi-110007, India

Purnima Dhall Institute of Genomics and Integrative Biology, Mall Road, Delhi-110007, India

Rita Kumar Institute of Genomics and Integrative Biology, Mall Road, Delhi-110007, India

Shubhangini Sharma CDL, Intas Biopharmaceutical, Ahmedabad, Gujrat, India.

Reena Institute of Genomics and Integrative Biology, Mall Road, New Delhi, India.

Anil Kumar National Institute of Immunology, New Delhi, India.

Pallavi Mittal ITS Paramedical College, Ghaziabad, UP, India

A.S Panwar Department of Biotechnology, HNB Garhwal University, Srinagar (Garhwal), Uttarakhand, India

J Jugran Department of Biotechnology, HNB Garhwal University, Srinagar (Garhwal), Uttarakhand, India

G.K Joshi Department of Biotechnology, HNB Garhwal University, Srinagar (Garhwal), Uttarakhand, India

Navneet Singh Chaudhary Department of Biotechnology, Sir Padampat Singhania University (SPSU), Udaipur-313001, Rajasthan, India

Mohammad J. Taherzadeh School of Engineering, University of Borås, Borås, Sweden

Patrik R. Lennartsson School of Engineering, University of Borås, Borås, Sweden

Oliver Teichert Lantmännen Agroetanol AB, Norrköping, Sweden

Håkan Nordholm Lantmännen Agroetanol AB, Norrköping, Sweden

Sapna Jain Department of Biotechnology, Institute of Biomedical Education and Research, Mangalayatan University, Aligarh-202145, India

Mukesh Kumar Yadav Department of Biotechnology, Institute of Biomedical Education and Research, Mangalayatan University, Aligarh-202145, India

Ajay Kumar Department of Biotechnology, Institute of Biomedical Education and Research, Mangalayatan University, Aligarh-202145, India

Komal Saxena Department of Biotechnology, Institute of Biomedical Education and Research, Mangalayatan University, Aligarh-202145, Uttar Pradesh, India.

Avinash Kumar Sharma Department of Biotechnology, Institute of Biomedical Education and Research, Mangalayatan University, Aligarh-202145, Uttar Pradesh, India.

Ashish Deep Gupta Department of Biotechnology, Institute of Biomedical Education and Research, Mangalayatan University, Aligarh-202145, Uttar Pradesh, India.

Lalit Agrawal CSIR-National Botanical Research Institute, Rana Pratap Marg, Lucknow, 226 001, Uttar Pradesh, India.

Sumita Srivastav Department of Physics, Government Post Graduate College, Uttarkashi, Uttarakhand

Prashant Anthwal Department of Biotechnology, Graphic Era University, Dehradun, Uttarakhand

Tribhuwan Chandra Department of Biotechnology, Graphic Era University, Dehradun, Uttarakhand

Ruchika Goyal Department of Biotechnology, Graphic Era University, Dehradun-248002, India

CHAPTER 1

Introduction to Biofuels

Pramod Kumar1 and Vikash Babu2,*

1Department of Biotechnology, Indian Institute of Technology Roorkee, Roorkee-247667 (India)

2Department of Biotechnology, Graphic Era University, Dehradun-248002

Biofuels mark their presence since the discovery of fire and have been very profoundly used for ages. The ancient raw material for biofuel is wood, exploited in solid form and having several usages with major applications in cooking and heating. Later on, the evolved form of biofuel came into existence as a form of liquid oil that was used from the time immemorial to light up homes and paths for everyday life. Olive and whale oils are some of the ancient types of biofuels employed for this purpose, mostly derived from plants and animals, they were in use for a very long period of time until the application of kerosene replaced them [1, 2]. Moreover, other forms of biofuel started prevailing from the late eighteen century; ethanol is one of the most exploited biofuels for its remarkable application especially to the transportation sector [3]. Corn derived ethanol was first employed for early transportation, mainly in cars. Subsequently, several other feed stocks were employed as sources for biofuel extraction such as plants like peanuts, hump, grains and potatoes [4]. Biodiesel, a later discovered form of biofuel, came into existence only in the twentieth century [5]. Presently, these two classes are the largest exploited biofuel types.

The twentieth century was an era of exploration and the use of resources with concern to the availability of reserves was not a big question. However, with rising populations and urbanization, finding the energy solution has become an area of prime importance. Major energy thrusts are required from the transportation, industrialization and agricultural sectors. Fossil fuels are key sources to bear the burden of entire need but ever increasing demand and limited stock of such fuels force us to employ alternative approaches for the renewable and sustainable production of energy [6]. Hence, biofuels are considered one of the remarkable solutions for this problem. Fuels that are obtained from biological material and have been recently taken out from their natural growing places or are by-products of living organisms are placed in a class of biofuels contrary to the fossil fuel derived products that are extracted from fossilized organisms buried for millions of years under the earth’s crust and converted to a form of fuel due to high pressure and temperature. Because of renewable nature and the immense possibility of improvement and engineering, biofuels are becoming a promising source of energy contrary to the limited and localized availability of fossil fuels. Moreover, biofuels are a possible solution to the dependence on foreign energy sources and are also suitable to circumvent environmental concerns. There is big hidden potential in biofuel based energy sources, especially when it is combined with efficient agriculture and scientific application that enables it to provide mankind with various raw materials required for food fiber and energy [7].

There are several forms of fuel that can be produced from biomass, referred to in general as biofuel, that cover liquid forms of fuel such as ethanol, methanol or biodiesel and gaseous forms like methane and hydrogen. On the basis of application and feedstock utilization, the biofuel can be summarized in two stages, first generation biofuel and second-generation biofuel [8]. The most predominant types of first generation biofuels are ethanol, fatty acid methyl ester (FAME or biodiesel) and pure plant oil (PPO). The most common form of biofuel exploited worldwide is bio-ethanol with global production increases from 17 thousand million liters in the year 2000 to 68 thousand million liters in 2008 [9, 10]. The key feedstocks for production of ethanol are sugarcane, wheat, sugar beet, rapeseed, soybean and palm oil [11]. Most of ethanol’s worldwide production is contributed by the United States and Brazil by using corn or sugarcane as main feedstock, while Europe produces from potato, wheat or sugar beet. For biodiesel, a major producer is Europe, where Germany is the leader whose production meets 3% of the entire German fuel requirement [12]. Rapeseed is exploited as the most widely used feedstock for an approximate contribution of 70% of European biodiesel production followed by soy that contributes 17% of the production. A smaller portion of production is obtained from sunflower and palm oil [13].

Pure plant oil is a relatively new biofuel resource and it has been gaining importance recently due to early limited local productions. The key features associated with this class are economic value and the feasibility to produce high yield ratios for per hectare production. These properties make it suitable for the markets of developing countries. Some good examples are observed in countries like Malaysia and Indonesia because of the low cost of labor and production in comparison to the countries of Europe and North America. Recently, imports from these countries have gained importance [14]. The main advantages around first generation biofuels are curbing the release of CO2 and domestic energy security. However, the availability of raw material, adverse effects over the biodiversity and competition for farmlands are major setbacks. Furthermore, the major concerns associated with first generation biofuels are the sustainability of resources from which they are produced as well as their direct competition for food crops and environmental threats related to ecosystems.

There is now well established analysis for biofuels that they should be very efficient in terms of reduction of emissions and net life cycle of green house gas (GHG) emissions that should certainly meet the criteria of social and environmental sustainability. Except for bioethanol from sugarcane, none of the first generation biofuels appear to be fruitful for a future transport fuel mix. All these concerns gave rise to the next stage of biofuel production, so-called second generation biofuels [15]. Due to the choice of feedstock and cultivation technology, second generation biofuels have immense advantages like the consumption of waste and the use of abandoned land, so the second generation of biofuels paves the way for immense application in the biofuel generation that can also satisfy the economical, social and environmental criteria. But unjustified use of second generation biofuel can also compete with regular food crops and may lead to unsustainable resources. Hence, it is of the utmost importance to set some benchmarks for their exploitation like minimum life cycle GHG reductions, land use changes and strict limits for social as well as economic standards.

The criteria to exploit non-food biomass is well addressed by second generation biofuels with the application of several strategies like the application of feedstocks having lignocellulose material that can come from bi-products of agriculture, such as rice husk, corn rub, and sawdust and residues that comes from the forest, such as sugarcane bagasse etc. [16]. According to a report from the US EPA in 2009, cellulosic ethanol is far more promising than any of the first generation biofuels, except bioethanol from the sugarcane of Brazil. Moreover, high organic content of the waste and sludge also possess good potential for application as a feedstock due to the presence of a reasonably high proportion of carbohydrates and proteins. The application of anaerobic digestion to sludge makes it very useful for bioenergy production [17]. The slight modification in the processing of waste can yield other compounds like acetic acid and related organic acids, having additional economic advantages [18]. The acetic acid and organic acid are very important industrial intermediaries that act as carbon sources for the growth of several kinds of microbes that can produce a range of biofuels and chemicals. Apart from these sources, with the recent advancement of microbial engineering, the algal derived feedstock is also showing remarkable potential for the production of biofuel [19]. Because of the versatile nature of algal growth condition, it possesses huge potential to grow over almost any kind of stringent environmental condition like saline water, wastewater, coastal sea water and non-arable lands [20]. Moreover, algal biomass is especially suitable for the high yield of lipids required for production of biodiesel [21]. Because algal feedstock production has very limited competition from regular food crops, it makes it further suitable for biofuel generation.

In sum, a cumulative approach involving specific applications regarding based on the sources of feedstock, availability of land, labor, socioeconomic conditions and selecting a suitable kind of biofuel possesses an immense possibility to meet the needs of fuel in an efficient and sustainable way.

1.1 Global Scenario of Biofuel Production and Economy

The possibility lying in biofuel based energy solutions has gained worldwide attention now that it is visible in the form of policies made by several governments to cut their dependency on fossil fuels by using an environmentally friendly approach. Some of the leading nations in line for promotion of biofuel are the United States, Brazil, E.U. member countries, Canada, China and India. The US government has made one of the most ambitious projections of biofuel by advocating the three-fold increase of bioenergy in the duration of the next ten years [22]. Under the name ‘biofuel’ two major commodities lie, these are bioethanol and biodiesel. The feedstocks for bioethanol production are mainly sugar, corn, soybean, wheat and sunflower whereas jatropha, vegetable oil, palm, rapeseed and soybean are raw materials for biodiesel. Bioethanol is the most forward standing type of biofuel that is ready to replace gasoline and is now part of the many government’s policies for biofuel application, as observed from some of the big countries like Brazil with a mandatory use of 22% bioethanol, 10% in several state of USA and China. Moreover, the hydrous bioethanol (96 percent bioethanol with 4% of water) is also promoted in these countries for extensive use [23]. According to the US Energy Independence and Security Act of 2007, it is envisioned that the renewable energy contribution by bioethanol and other biofuels will increase to 36 billion gallons annually by 2022. Moreover, the US EPA (the United States Environmental Protection Agency) is now permitting the mixing of 10% ethanol due to an amendment of the Clean Air Act. The related effects of these policies are visible in the form of increased corn ethanol production in the US market [24]. The impact of policies made for ethanol production and uses is giving positive outcomes observed for last two decades with respect to the social cost and benefits produced by monitoring biofuel related taxes, tariffs and credit effects of the agricultural sector [25]. This is visible in the form of an average price reduction of 14 ¢ per gallon analyzed from data obtained over the period of 1995–2008 [26]. Such policies demonstrate the linkage of the agricultural and energy markets as is visible in the form of exceeding the mandatory level of ethanol due to high petroleum prices and corn yield [24].

The Agricultural Trade Office of São Paulo projected that total ethanol production for the year 2012 will be 25.5 billion liters. That is followed by total production of 21.1 billion liters in 2011 that is approximately 24.9 percent of the total worldwide biofuel despite the crisis phase that appeared due to many reasons [27, 28]. Brazil is an example of setting a competitive market where successful application of bioethanol is commercialized without subsidy using sugarcane as feedstock [29], moreover Brazil is the largest exporter of bioethanol and the second largest producer after the US

The European Union is the third largest biofuel producer implementing the projection of biofuel by a contribution of five percent share by 2015 and a further rise to ten percent by 2020 [30]. The EU2009 directive has an explicit link to correlate the consumption and production of biofuel to make it a sustainable industry [31]. Moreover, the EU has taken a safe way by prioritizing the import of 30 percent of feedstock or biofuel to reduce the price pressure in EU feedstock. For the anticipated biofuel production in 2012, the E.U. requires 10.3 MMT of sugar beet and 9.7 MMT of vegetable oil and animal fat. For bioethanol, in comparison to the US and Brazil, the E.U. is only a minor producer and for volume contribution bioethanol shares 28 percent of the total biofuel market in the road transport sector [32]. While for biodiesel, the E.U. is the largest producer with 60 percent of the market share [33]. In the European Union, Germany is the largest biofuel producer followed by France as the second largest producer [34]. France also has an ambitious goal to reach a biofuel share of 10 percent by 2015 [35].

For Canada, the mandatory renewable fuel content has been shouted to 5 percent by 2010 as per the recommendations of federal legislation in 2008 [36]. Moreover, the federal mandate also implemented a law requiring two percent renewable content in diesel by 2011. For bioethanol production, Canada has reached almost 2 billion liters of production per year [37], where main feedstock for the bioethanol production in Canada is corn and wheat, the biodiesel is preferably made from canola [38]. Canada has also been subsidized to import biodiesel by a tariff of 6.5 percent as most favored nation and three percent by general preferential tariff [36]. The policies made earlier to make bioethnol an energy alternative are now visible in form of reasonable rise of ethanol production and its sustainability. But due to the limited biofuel production for the short as well as the medium term, it appears that Canada may not become a major player for ethanol production in the near future.

China is also enacting mandates for the blending of ethanol up to 10 percent by 2020. With the policy of using non grain based feedstock for second generation biofuel production, there are five Chinese provinces Heilongjian, Jilin, Liaoning, Anhui and Henan working on this mandate [39]. There are a total of five ethanol producing plants in China; out of these, four use grain based feedstock (corn and wheat) and the other one uses tuber of cassava. Grain based ethanol production was 2,103 million liters while the cassava based production was 152 million liters. On the other hand, Chinese biodiesel production was estimated to be 3,408 million liters where the main input materials employed are used/waste kitchen oil and vegetable oil crusher residues [40].

India is producing the anticipated amount of bioethanol sufficient to meet the two percent blending target for the year 2012. The production of biodiesel from the plant jatropha is presently insignificant. As per the national biofuel policy approved by the government of India in 2009, it was promoted to blend 20 percent of biofuel to the fossil fuels by the end of 12th five year plan (2017). Present targets of mixing five percent of bioethanol is in direct relation to the surplus production of sugar for last three years, whereas due to the unavailability of suitable feedstock for biodiesel production, it is improbable to achieve the 20 percent replacement of biodiesel. To meet the need of the 5 percent blending of biodiesel rule for the year 2011–12, 3.21 million tons of biodiesel from 3.42 million hectares of land is required [41]. With an average production of 2.5 tons per hectare the jatropha is considered the most promising feedstock with a 30 percent biodiesel recovery rate. At this rate there is a requirement of 18.6 million hectares of cultivation of jatropha by 2017 to support the 20 percent blending target. Moreover, the biomass based energy production, especially the grid quality power, is working reasonably well at an estimated 31,000 MW with the bagasse surplus contribution of 10,000 MW to fuel factories of sugar, petrochemical, distillery, mills of rice, sugar and textile. With the projection of a 29 percent rise in ethanol production for the year 2012 by giving 2.1 billion liters as a cascading result of higher sugar and related higher molasses production [41], India is achieving reasonable progress towards the sustainable biofuel market.

References

1. A. Arsuf and V. Sussman, “The Samaritan Oil Lamps from Apolonia-Arsuf” T.A. 10, pp. 71–96, 1983.

2. L.S. Russell, A Heritage of Light: Lamps and Lighting in the Early Canadian Home, University of Toronto Press, 2003.

3. N.A. Otto, Apparatus for heating the ignition tube of gas motor engines, US patent 388301, Assigned to N.A. Otto, August 21, 1888.

4. Ford Predicts Fuel from Vegetation, New York Times, Sept. 20, p. 24, 1925.

5. M. Fangrui and M.A. Hanna, Bioresource Technology, 70, 1–15, 1999.

6. B. Kamm, P.R. Gruber and M. Kamm, Biorefinery industrial processes and products. Status and future direction, vols. 1. Weinheim, Wiley-Vch Gmbh and Co KGaA; 2006.

7. C.V. Stevens and R. Verhe, Renewable bib resources scope and modification for nonfood application, Chichester, John Wiley and Sons Ltd, 2004.

8. S.N. Naik, V.V. Goud, P.K. Rout and A.K. Dalai, Renewable and Sustainable Energy Reviews, Vol. 14, p. 578–597, 2010.

9. M. Balat, Energy Exploration and Exploitation, Vol. 25, p. 195–218, 2007.

10. Biofuels Platform, Production of Biofuel in the EU. Biofuels Platform, Lausanne. http://www.biofuels-platform.ch/en/infos/eu-bioethanol.php. 2010.

11. M. Balat, and H. Balat, Applied Energy Vol. 86, p. 2273–2282, 2009.

12. Status Report Biodiesel, Biodiesel Production and Marketing in Germany 2005, Union for the Promotion of Oil and Protein Plant, Berlin, Germany 2005.

13. Biofuels Annual, EU Annual Biofuels Report, Global Agriculture Information Network, GAIN Report Number:NL0019, 2010.

14. S.H. Gay, M. Mueller and F. Santuccio, Analysing the implication of the EU 20–10-20 targets for world vegetable oil production, paper presented in ‘07th EAAE Seminar “Modelling of Agricultural and Rural Development Policies”. Sevilla, Spain, January 29th -February 1st, 2008.

15. E.H.S. Ralph, W. Mabee, J.N. Saddler and M. Taylor, Bioresource Technology, Vol. 101, p. 1570–1580, 2010.

16. G. Chaudhary, L.K. Singh, and S. Ghosh, Bioresource Technology. Vol. 124, p. 111–118, 2012.

17. Y. Chen, J.J. Cheng and K.S. Creamer, Bioresource Technology. Vol. 99, p. 4044–4064, 2008.

18. H. Rughoonundun, C. Granda, R. Mohee and M.T. Holtzapple, Waste Management. Vol. 30, p. 1614–1621, 2010.

19. P. M. Schenk, S.R. Thomas-Hall, E. Stephens, U.C. Marx, J.H. Mussgnug, C. Posten, O. Kruse and B. Hankamer, Bioenergy Research, Vol. 1, Issue 1, 20–43, 2008.

20. A. Singh, P.S. Nigam and J.D. Murphya, Bioresource Technology, Vol. 102, Issue 1, p. 10–16, 2011.

21. L. Yanqn, M. Horsman, N. Wu, C. Lan and N. D. Calero, Biotechnology Progress Vol. 24, p. 815–820, 2008.

22. M.F. Demirbas and M. Balat, Energy Conversion and Management, Vol. 47, p. 2371–2381, 2006.

23. W.D. Walls, F. Rusco and M. Kendix, Energy Policy, Vol. 39, p. 3999–4006, 2011.

24. W. Thompson, S. Meyer and P. Westhoff, Energy Policy, Vol. 37 Issue 2, p. 745–749, 2009.

25. M.S. Luchansky and J. Monks, Energy Economics, Vol. 31, p. 403–410, 2009.

26. X. Du and D.J. Hayes, Energy Policy, Vol. 37, Issue 8, p. 3227–3234. 2009.

27. Renewable Fuels Association, Accelerating industry innovation: 2012, ethanol industry outlook. In: Renewable Fuels Association, http://ethanolrfa.3cdn.net/d4ad995ffb7ae8fbfe_1vm62ypzd.pdf. 2012.

28. R. Colitt and S. Nielsen (2012-03-13). “Brazil Ethanol Drive Falters on Domestic Supply Shortage”. Bloomberg Businessweek. Retrieved 2012-03-22.

29. S. Macrelli, J Mogensen and G. Zacchi, Biotechnology for Biofuels, 5:22, 2012.

30. Directive 2009/28/EC of the European Parliament and of the Council of 23 April 2009 on the promotion of the use of energy from renewable sources and amending and subsequently repealing Directives 2001/77/EC and 2003/30/EC.

31. P. Genovesi, Current Opinion in Environmental Sustainability, Vol. 3, Issues 1–2, p. 66–70, 2011.

32. EU-27 Biofuel Annual. EU biofuel annual 2012.

33. R. Steenblik, BIOFUELS – AT WHAT COST? Government support for ethanol and biodiesel in selected OECD countries, The Global Subsidies Initiative (GSI) of the International Institute for Sustainable Development (IISD), Geneva, Switzerland, 2007.

34. R. Brand, Networks in renewable energy policies in Germany and France, Berlin conference on the human dimension of global environmental change: greening of policies—policy integration and interlinkages, Berlin, 3–4 December, 2004.

35. European Commission (EC). Green Paper, “A European strategy for sustainable, competitive and secure energy”. Brussels, March 8, 2006.

36. Global Subsidies Initiative (GSI-2009), Biofuels-At What Cost? Government support for ethanol and biodiesel in Canada. Available online at: http://www.globalsubsidies.org/files/assets/oecdbiofuels.pdf, verified May 10th 2011.

37. Growing beyond oil delivering our energy future, a report card on the Canadian renewable fuels industry, Canadian renewable fuel association, November 2010.

38. GAIN (Global Agriculture Information Network) report number CA0023, Canada Biofuel Annual 7/13/2010.

39. C.A. Tisdell, Working Paper – “The Production of Biofuels: Welfare and Environmental Consequences for Asia 2009”.

40. GAIN (Global Agriculture Information Network) report number 12044, China-Peoples republic of Biofuel Annual 07/09/2012.

41. GAIN (Global Agriculture Information Network) report number IN2081, India, Biofuel Annual 6/20/2012.

*Corresponding author: [email protected]

CHAPTER 2

Advances in Biofuel Production

M.D. Berni1, I.L. Dorileo2, J.M. Prado3, and T. Forster-Carneiro3,* and M.A.A. Meireles3

1Interdisciplinary Centre of Energy Planning, State University of Campinas – UNICAMP, Brazil. [email protected]

2Interdisciplinary Centre of Energy Planning, Federal University of Mato Grosso - UFMT, Brazil.

3LASEFI/DEA/FEA (School of Food Engineering) / UNICAMP (University of Campinas), R. Monteiro Lobato, 80, Campinas, 13083–862, SP, Brazil

Abstract

The main driving forces for the development of biofuels are the instability of world oil prices, security of energy supply, global warming, and the creation of new opportunities for agriculture. Interest in the commercial production of biofuels for transport was renewed in the mid-1970s, when ethanol began to be produced from sugarcane (Brazil) and corn (United States) for blending mandates, which define the proportion of biofuel that must be used in road transport fuel. Nowadays over 50 countries have adopted blending targets. However, biofuels are still little represented in comparison to fossil fuels. This chapter will discuss the advances in the production of first, second and third generation biofuels, mainly sugar- and starch-based ethanol, conventional biodiesel, biogas and biomethane, cellulosic ethanol, syngas, bio-oil from pyrolysis and hydrothermal process, hydrogen, and the biorefinery concept. The production of biomass for biofuels and the future trends of biofuels development also are discussed in this chapter.

Keywords: Biodiesel, biofuels, biogas, biomass, bio-oil, ethanol, hydrogen

2.1 Introduction

Concerns with the instability of world oil prices, security of energy supply, global warming, and the creation of new opportunities for agriculture, are stimulating the search for sources of energy that are clean, sustainable and competitive with fossil energy. These are the main driving forces for the development of biofuels, which have become some of the most promising forms of energy to ensure a sustainable energy matrix [1, 2].

Biofuels started to be produced in the late 19th century, when bioethanol was derived from corn and Rudolf Diesel’s first engine ran on peanut oil. Until the 1940s, biofuels were seen as viable transport fuels, but falling fossil fuel prices stopped their further development. Interest in the commercial production of biofuels for transport rose again in the mid-1970s, when ethanol began to be produced from sugarcane in Brazil and then from corn in the United States. In most parts of the world, the fastest growth in biofuel production has taken place over the last 10 years, supported by ambitious government policies. Besides energy security and sustainable agriculture concerns, the reduction of CO2 emissions in the transport sector has become an especially important driver for biofuel development. One of the most common support measures is a blending mandate, which defines the proportion of biofuel that must be used in road transport fuel and is often combined with other measures such as tax incentives [3]. Over 50 countries have adopted blending targets or mandates and several more have announced biofuel quotas for future years [4, 5]. Therefore, biofuels are gaining importance among the alternatives to fossil fuels.

However, biofuels are still little represented compared to fossil fuels (Figure 2.1). Their large scale production ultimately depends on advances in productivity, in order to mitigate any negative effects associated with them, such as decreases of indigenous forests or the increase in price of agricultural commodities due to land use. In light of this, a worldwide technological race is taking place to develop biofuels from second and third generations, whose main support programs are carried out by the United States (US) and the European Union (EU).

Figure 2.1 Percentage of sources of energy in year 2010.

Adapted from IEA [6].

Biofuels are derived from renewable biomass sources. The conversion of sunlight into chemical energy is one of the most important processes to sustain life on the planet. The process of converting solar energy into chemical energy responsible for the reproduction of plants involves the consumption of O2 and the production of CO2 and plant resources. The term “biomass” is used to name the vegetable resources used for the production of bioenergy. The main sources of biomass are forests, agricultural crops and residues resulting from agroforestry and livestock industries.

Biomass is classified as modern or traditional, according to its origin and type of processing. Traditional biomass is associated with the production of energy using resources from unsustainable management and techniques that are characterized by low efficiency and high emission of pollutants. Modern biomass is obtained by proper management, using technologies that guarantee high efficiency of production and conversion processes, ensuring biofuels of high quality, such as ethanol, biogas and bio-oil from vegetable oils, reforested wood, industrial and municipal waste, etc. [7].

Biomass is one of the oldest energy resources used by humanity. Although there are no precise figures, it is estimated that one third of the world population depends on traditional biomass as their main source of energy (wood, agricultural, livestock and forestry residues, among other sources), so that about 90% of the world consumption of biomass is of traditional biomass. In some regions of Africa, Asia and Latin America families use traditional biomass to meet their energy needs, mainly for cooking. In these cases, the use of biomass is habitually inefficient, resulting in the depreciation of natural resources and damage to the health of the operators of the cooking systems. The quality of the energy services provided by this type of application is usually poor, and it requires intensive labor to perform the activities of collecting and transporting the fuel. These activities are usually undertaken by women and children. Furthermore, the production of fuels from traditional biomass sources can aggravate the problem of deforestation, increasing the pressure on the local ecosystem and the net emissions of greenhouse gases (GHG). Despite these drawbacks, billions of people still use traditional sources of biomass to supply their energy needs because they are more accessible and less expensive. Dry biomass is easily obtained and stored, and its use has cultural roots in many societies. Moreover, in the absence of this feature, many countries would have to increase their energy imports and many needy families would have to spend more money to acquire other forms of energy [7].

Biofuels are energy vectors produced from modern biomass. Their conversion occurs by means of physical, chemical and/or biological processes. The production of liquid biofuels to replace petroleum (especially diesel and gasoline) has attracted particular interest, and is considered a promising alternative to the energy market. The American National Biofuels Action Plan points to five strategic areas in the biofuels production chain that should have federal investment: production of raw materials; logistics of the distribution of raw materials; the best conversion process; fuel distribution systems; and technologies for the efficient use of fuel. The US Congress passed in 2007 the “Renewable Fuel Standard” (RFS), as part of the Energy Independence and Security Act (EISA). This act aims to reduce gasoline consumption by 20% by 2017. This would be achieved by increasing the domestic production of biofuels. To reach this proposal it would be necessary to have an annual increase of the production of biofuels of 35 billion gallons.

Europe has also stimulated the production of biofuels. The Common Agricultural Policy (CAP), revised in 2003, provides incentives for farmers that select European species for energy purposes, such as rapeseed and sugar beet. The new policy provides a special remuneration of € 45 per hectare to produce bioenergy, and in these areas food crops cannot be grown [8].

Global biofuel production reached 105 billion liters in 2010, which represents an increase of 17% compared to around 90 billion liters in 2009 (Figure 2.2). However, this figure stands far behind the 35 billion gallons increase proposed by the EISA in order to reduce gasoline consumption. Therefore, there is still much to be done to achieve the objective of turning biofuels into viable replacements for oil-based fuels.

Figure 2.2 Global biofuel production in the 2000–2010 period.

Adapted from IEA [9].

The United States leads the production of ethanol, and also is the major producer of biofuels (ethanol + biodiesel) in the world. On the other hand, the European Union is the major biodiesel producer, accounting for about 60% of its world production. Brazil is the second largest ethanol producer in the world, and is the second largest biofuels producer in the world. The Brazilian Alcohol (ethanol) Program (ProÁlcool) was launched in 1975 as a policy to reduce the country’s dependence on oil import. It encouraged the production of ethanol from sugarcane, which today is an important crop for economic development of Brazil, for the substitution of gasoline in transport. Today around 50 % of Brazilian fleets run with flex fuel engines, which run on gasoline, ethanol, or a mixture of them both. Furthermore, sugarcane is a source of residue biomass (bagasse), which is used for electric energy production when burned, but which could also be used in second generation processes for the production of bioethanol [10].

It is estimated that 86 billion liters of ethanol and 19 billion liters of biodiesel were produced worldwide in 2010. Ten years ago, the production of biofuels did not surpass 20 billion liters (Figure 2.2.) [9]. However, despite all the environmental advantages presented by biofuels, the expansion of their production is limited by their high production cost when compared to their competitor: fossil fuels (diesel and gasoline). One of the main factors that makes the production of first generation biofuels more expensive is the cost of the raw material. The raw materials used in the production of biofuels are typically of high added value, such as corn and sugarcane that are used for bioethanol production, and soybeans that are used for biodiesel production. Thus, the cost of the products is usually high. Because of that, with the exception of sugarcane ethanol produced in Brazil, biofuels still require subsidies to enable their production [11].

In 2011, bioethanol was projected to overtake the animal feeding industry as the largest corn consumer in the US, helping the production margins and decreasing the need for subsidies. The Renewable Fuel Standard (RFS), by the US Environmental Protection Agency (EPA) provides a guaranteed market of 50 billion liters in 2012, but the industry nearly matched this goal in 2010, suggesting that the mandate alone would not support the existing market. The corn ethanol mandate increases to 57 billion litters in 2015.

Brazilian sugarcane ethanol would likely become more prevalent in the US if American ethanol subsidies and tariffs were removed. Sugarcane bioethanol is cheaper and more efficient to produce, although there are worries that its production may indirectly lead to deforestation. Brazil has plans to build 100 new sugarcane mills by 2019, increasing capacity by 66 %, to increase Brazilian ethanol production and exports in the coming years.

Considering this entire scenario, there is much to be done in the biofuels field to improve economic feasibility. Technological advances in the production and conversion of biofuels can lead to more competitive fuels. The development of chemical and biological sciences, along with new crops for energy production, new enzymes and artificial simulation of biological processes (anaerobic digestion, fermentation, etc.) can reduce their production [12]. Therefore, heavy investments are being made for the development of these technologies. The objective of this work is to review some of the most recent advances in the production of biofuels.

2.2 Advances in the Production of First, Second and Third Generation Biofuels

The term biofuel refers to liquid and gaseous fuels produced from biomass. There is considerable debate on how to classify biofuels [3]. They are commonly divided into first-, second- and third-generation biofuels, but the same fuel can be classified differently depending on whether technology maturity, GHG emission balance or feedstock is used to guide the distinction. This work uses a definition based on the maturity of a technology, and the terms “conventional” and “advanced” for classification [9].

2.2.1 Conventional and Advanced Biofuels

There are a number of technologies for energy conversion from biomass, suitable for applications in small and large scales. Considering the convention adopted by the International Energy Agency (IEA) for the classification of biofuels, Figure 2.3 presents a summary of the conventional and advanced biofuels, illustrating technologies and processes for obtaining them. It can be noted, by the number of applications, that special attention has been given to liquid fuels [9].

Figure 2.3 Status of main biofuel technologies adapted from IEA [9].

Conventional biofuel technologies include well-established processes that are already producing biofuels at a commercial scale. These biofuels, commonly referred to as first-generation, include sugar- and starch-based ethanol, oil-crop based biodiesel and straight vegetable oil, as well as biogas derived from anaerobic digestion. Typical feedstocks used in these processes include sugarcane and sugar beet, starch-bearing grains like corn and wheat, oil crops like rapeseed, soybean and oil palm, and in some cases animal fats and used cooking oils.

Advanced biofuel technologies are conversion processes that are still in research and development, pilot or demonstration phases, commonly referred to as second or third generation. This category includes hydrotreated vegetable oil (HVO), which is based on animal fat and plant oil, as well as biofuels based on lignocellulosic biomass, such as cellulosic ethanol, biomass-to-liquids (BtL) diesel and bio-synthetic gas (bio-SG). It also includes algae-based biofuels and the conversion of sugar into diesel-type biofuels using biological or chemical catalysts [9, 13].

The second-generation biofuels can be produced from waste materials resulting from industrial production processes, agriculture or agro-forestry. They constitute alternatives to reduce the cost of production of bioenergy and to decrease the competitiveness with food. The production of cellulosic ethanol, which is one of the most promising sources of “clean and cheap energy”, can, in principle, use as input any raw material containing cellulose and hemicellulose (such as bagasses, straws, hulls, etc.). However, significant technological advances are needed in this field, since these technologies are not economically feasible yet. The processes are complex and involve the use of technologies that are still embryonic.

From the third-generation biofuels, the production of biodiesel from microalgae cultures is a promising alternative form of bioenergy at an affordable cost, using soils that are not of high value for food production. However, this technology is still in the laboratory stage. In the near future, it will contribute to the large scale production of biofuel.

The GHG emission balance depends on the feedstock and processes used, and it is important to realize that advanced biofuels performance is not always superior to that of conventional biofuels. Nonetheless, environmental interest propels their development so they can become competitive with both fossil fuels and conventional biofuels.

Next, the main processes used to produce first-, second- and third-generation biofuels are presented in more depth.

2.2.2 First Generation Biofuels

First generation biofuels are those that have currently reached a stage of commercial production. In general, they come from food crops. The first generation biofuels use agricultural feedstocks as inputs to their production, which is the case of ethanol from sugarcane and biodiesel from vegetable oils, for instance. Table 2.1 shows an overview of production technologies of first generation biofuels. Next, the advances in their production are presented.

Table 2.1 Technologies for producing first generation biofuels.

2.2.2.1 Sugar and Starch Based Ethanol

In the sugar-to-ethanol process, sucrose is obtained from sugar crops such as sugarcane, sugar beet and sweet sorghum, and it is subsequently fermented by yeast into ethanol, also generating other metabolic by-products such as carbon dioxide. The ethanol is then recovered and concentrated by a variety of processes. The process of ethanol production from sugarcane includes the following steps (Figure 2.4):

Milling: the biomass is cleaned and milled;

Must preparation: water is mixed to the sugarcane juice and molasse to adjust the concentration of sugar for subsequent fermentation;

Fermentation: yeast is added to the mixture, converting sugars to ethanol and carbon dioxide;

Centrifugation: the liquid and solid fractions are separated;

Distillation: the ethanol contained in the liquid fraction is separated from the water, with a purity of approximately 95.6 % (hydrated ethanol);

Dehydration: the hydrated ethanol goes through a process to remove the remaining water (azeotropic distillation, extractive distillation or molecular sieving), yielding the anhydrous ethanol;

Denaturation: the ethanol to be used for fuel is then denatured with a small percentage of additives, such as methanol, isopropanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, etc., to make it inappropriate for human consumption.

Figure 2.4 Stages of production in sugar mills and distilleries.

Adapted from Prado and Meireles [14].

For the production of first generation bioethanol from corn, the process used for sugarcane needs to be adapted because the starch must undergo a pretreatment so that it is hydrolyzed into sugar prior to fermentation. In the milling step the raw material is comminuted into finer particles. These particles are then blended with water and enzymes (α-amylase), and the mixture is cooked at high temperatures (140–180°C) to liquefy the starch. The mixture goes through saccharification, where a gluco-amylase enzyme is added to convert the starch molecules into fermentable sugars. The fermentation and distillation steps are similar to the ones used in sugarcane processing. The high cooking temperatures imply high operating costs, which makes starch-based ethanol economically less advantageous when compared to sugarcane-based ethanol.

The first generation ethanol can be used as a pure fuel or can be blended with gasoline and other fuels.

The most recent advances in first generation ethanol have come from improving ethanol production by S. cerevisiae, particularly by genome shuffling and global transcription machinery engineering. Among the most significant developments in the fermentation field are the implementation of very high-gravity technology, the use of lignocellulosic hydrolysates as feedstock and the application of high-cell-density continuous processes. Such technologies benefit from the selection and engineering of more robust yeast strains, with tailored properties for each of the processes. [15].

2.2.2.2 Conventional Biodiesel

Several processes are under development aiming to produce fuels with properties very similar to diesel and kerosene, one of which is biodiesel. Biodiesel is defined by the American Society for Testing and Materials (ASTM) as a “synthetic liquid fuel, originating from renewable raw material and consisting of a mixture of alkyl esters of long chain fatty acids derived from vegetable oils or animal fats”. It may also be defined as “derivative from renewable biomass that can replace, partially or completely, fossil fuels in internal combustion engines or for generating another type of energy”.

Conventional biodiesel can be produced from raw vegetable oils derived from soybean, rapeseed, palm oil or sunflower, among others, as well as animal fats and used cooking oil. Vegetable oils transesterified with alcohols are the most common form of biodiesel. Transesterification aims at modifying the molecular structure of the vegetable oil, so that its physicochemical characteristics are similar to mineral oil. The transesterification reaction is the conversion of vegetable oil into methyl or ethyl esters of fatty acids, which constitute biodiesel. The reaction occurs in the presence of an acid, basic or enzymatic catalyst, and a short chain alcohol. The most used alcohols in this type of reaction are methanol, which is toxic and originates from fossil fuels, and ethanol, a GRAS solvent. The fatty acid reacts with the short chain alcohol forming the ester (biodiesel) and water. Furthermore, glycerin is formed as a byproduct; it has application especially in the cosmetics industry. The transesterification reaction may be slow when conducted at room temperature, but it can be accelerated by using heat and/or catalyzers, especially basic, which can be recovered at the end of the reaction and reused. In a typical mass balance, for each 100 kg of crude vegetable oil 10–15 kg of alcohol is required to produce 100–105 kg of biodiesel and 10 kg of glycerol [16].

The great advantage of using the transesterified oil (biodiesel) is the possibility to replace the mineral diesel without the need to modify the engines. Biodiesel is one of the biofuels that has some of the most compatible characteristics with fossil fuels (petroleum diesel). For example, the high heating value of biodiesel (39–41 MJ/kg) is comparable with petrodiesel (43 MJ/kg); and other important parameters like flash point, cetane number and kinematic viscosity are similar to its fossil alternative [17]. Therefore, these fuels are blendable with fossil fuels at any proportion, can use the same infrastructure and are fully compatible with engines in heavy duty vehicles.

Current global biodiesel production, from different fatty raw materials, reaches about 6 billion liters per year and represents 10% of total biofuel production. In Brazil, government mandates for blending biodiesel with gasoline has promoted a production increase from around 100 million m3 in 2006 to more than 1.4 billion m3 in 2009, although the sustainability of biodiesel production is still to be demonstrated [1].

The most recent advances in first generation biodiesel production includes moving from methanol use to ethanol use due to the toxicity of the former; testing new catalysts; and using different raw materials, especially non-edibles. Typically, a more saturated fat allows better biodiesel properties, especially regarding the cetane number and stability, although they present higher melting or dripping points, which can be a problem in colder climates. Therefore, soybean and castor have limited feasibility, whereas tallow and palm oil represent more suitable alternatives [1]. Therefore, there are still a number of approaches to be explored that can lead to the optimization of biodiesel production and thus decrease its cost.

2.2.2.3 Biogas and Biomethane

Biogas can be produced by anaerobic digestion of feedstocks such as organic waste, animal manure and sewage sludge, or from dedicated green energy crops such as maize, grass and wheat. The anaerobic digestion process, or biomethanization, represents an attractive treatment strategy for reducing the contamination of the different biosolid residues and may benefit society by providing a renewable biofuel source from different organic substrates. Basically, the microorganisms are retained in the bioreactor, with separation between the acidogenic and methanogenic bacteria. The biometanization process of biomass is accomplished by a series of biochemical transformations, which can be separated into a first step where hydrolysis, acidification and liquefaction take place and a second step where acetate, hydrogen and carbon dioxide are transformed into methane. The biogas product from biomethanization contains between 60–80% of methane. Biogas is often used to generate heat and electricity, but it can also be upgraded to biomethane by removing CO2 and hydrogen sulfide (H2S), and injecting it into the natural gasgrid. Biomethane can also be used as fuel in natural gas vehicles.

There are a large number of factors that affect biogas production efficiency such as pH, temperature, and inhibitory parameters (like high organic loading) [18]. The recent trends in biogas production focus on optimizing these operational conditions to improve yields and decrease costs.

2.2.3 Second Generation Biofuels

Instead of only using readily extractable sugars, starches or oils as in the previous generation, second generation biofuels do not use edible sources as raw materials. They focus on different feedstocks and their parts in order to explore a broader range of raw materials. One example is bioethanol produced from lignocellulosic biomass from various non-edible sources using all the parts of the biomass. The raw materials can be agricultural residues such as straw and stover, residues from forestry, or biomass crops such as grasses (e.g. switchgrass) and wood from short rotation forestry. All these raw materials can be converted into biofuels via biochemical routes using enzymes and/or microorganisms, including genetically modified microorganisms that have been developed specifically for this purpose [19]. As second generation biofuels use different bioconversion pathways, they apparently avoid the “fuel versus food” dilemma. However, they can compete with the use of agricultural lands which could be used to grow food crops [20].

The main processes for the production of second generation biofuels are shown in Figure 2.5. Biomass conversion is conducted via two generic approaches: thermochemical decomposition including gasification, bio-carbonization, liquefaction and thermal decomposition (pyrolysis) processes; and biological digestion, essentially referring to microbial digestion and fermentation. While biological processing is usually very selective and produces a small number of discrete products in high yield using biological catalysts, thermal conversion often gives multiple and complex products, in very short reaction times, and inorganic catalysts are often used to improve the product quality or spectrum [21].

Figure 2.5 Main processes for production of second generation biofuels.

Adapted from Bacovsky et al. [22].

The term “second generation biofuel” is defined mainly on the basis of the feedstocks and conversion technologies. However, there is no precise definition; therefore, some biofuels cannot be allocated to a particular “generation” (e.g. biomethane), while other products claim to be third generation (fuels from CO2 fixing bacteria). The main second generation biofuels that have been studied in the last years include:

Hydrotreated vegetable oils (HVO): they are not strictly second generation because the raw material is (currently) first generation;

Hydrotreated esters and fatty acids (HEFA) fuels, also referred to as bioJet: also based on HVO, they were first developed for application in aviation, and now they are applied to different biofuels;

Cellulosic ethanol: chemically, there is no difference between cellulosic ethanol and conventional bioethanol; however, the raw material is made of cellulose in second generation, whereas in first generation simple sugars are directly fermented into bioethanol.

For more than three decades, biofuels produced from lignocellulosic sources have been receiving much attention. The extensive database in the literature confirms that the developments in this field have reached a near commercial stage [23]. Next, the main second generation biofuels are presented.

2.2.3.1 Cellulosic Ethanol

Lignocellulosic biomass is considered an important non-edible alternative for the production of cellulosic ethanol. It is also cheap, abundant, and fast-growing. Lignocellulosic biomass consists of a combination of lignin, cellulose and hemicellulose. The lignocellulosic complex provides the structural framework making up most of the plant matter. A wide variety of fuels can be derived from lignocellulosic material via the biological or chemical synthesis of products from the biological or chemical breakdown of cellulose, hemicellulose and lignin. Second generation bioethanol focuses on the production of ethanol via these routes. There is also interest in producing other chemicals and fuel components.

Fermentation of simple sugars from sugar crops and from hydrolysis of starch crops to produce ethanol is a commercial and widely used first generation process. Routes from lignocellulosic materials to ethanol are more complicated than those from sugar and starches, as lignocellulosic materials contain more complex sugar polymers, such as cellulose and hemicellulose, which are more difficult to break down [24]. Because of that, the second generation bioethanol production from biomass requires additional processing steps (Figure 2.6).

Figure 2.6 Processing steps for second generation bioethanol production from lignocellulosic biomass compared to first generation processes.

Reprinted from Biotechnology Advances, 28, S.I. Mussato, G. Dragone, P.M.R. Guimarães, J.P.A. Silva, L.M. Carneiro, I.C. Roberto, A. Vicente, L. Domingues, J.A. Teixeira, Technological trends, global market, and challenges of bio-ethanol production, 817–830, 2010, with permission from Elsevier [15].

The cellulose (source of hexoses such as glucose) as well as hemicellulose (mainly source of pentoses such as xylose) is not accessible to the traditional ethanol producing microorganisms. Therefore, these fractions must be hydrolyzed prior to fermentation. The main purpose of hydrolysis is splitting the polymeric structure of lignin-free cellulosic material into fermentable sugar monomers [22]. To obtain lignin-free cellulosic material a pretreatment is required. The pretreatment aims to separate the biomass into cellulose, hemicellulose and lignin fractions via physicochemical or biochemical routes; this process can also sometimes hydrolyze the hemicellulose into simple sugars. Then the cellulose undergoes hydrolysis to generate fermentable sugars. The sugars derived from hemicellulose and cellulose are then fermented into ethanol using yeasts [25].

The breaking down of the lignocellulosic complex is usually achieved by high energy-consuming biochemical conversions of the cellulose and hemicellulose components of the biomass into fermentable sugars. The cellulose hydrolysis stage can be carried out by chemical routes, using acidic or basic catalysts, or by biological routes, using enzymatic catalysts. Acidic hydrolysis is the most well-known process, and although acid and basic hydrolysis are relatively fast methods that produce high glucose concentrations, they have several drawbacks, such as the need to neutralize the reaction medium after the process, high corrosion of the equipment and the generation of solid wastes. Due to environmental problems posed by acidic and basic hydrolysis, the enzymatic process is more widely used nowadays [26]. The main advantage of enzymatic hydrolysis is that it does not generate fermentation microorganism inhibitors. In contrast, it is a very slow process, which makes it expensive, and the enzymes are difficult to be recovered and reused. Furthermore, the enzymes cannot break down the lignocellulosic complex, so enzymatic hydrolysis requires a pretreatment that allows for the enzymes to access the cellulose and the hemicellulose [27–28].