This document provides an introduction to green energy and biofuels. It discusses biomass feedstocks and their characterization. Various biomass conversion processes are covered, including thermochemical processes like pyrolysis and gasification, which can produce liquid, gaseous and solid fuels from biomass. Specific biofuels like bioethanol and biodiesel are examined in depth. The document also addresses the economics of biofuels and related policy issues.

1. Green Energy and Technology

2. Ayhan Demirbas
Biofuels
Securing the Planet’s Future Energy Needs
123

3. Ayhan Demirbas, Professor of Energy Technology
Sila Science and Energy
Trabzon
Turkey
ISBN 978-1-84882-010-4
e-ISBN 978-1-84882-011-1
DOI 10.1007/978-1-84882-011-1
Green Energy and Technology ISSN 1865-3529
A catalogue record for this book is available from the British Library
Library of Congress Control Number: 2008940429
© 2009 Springer-Verlag London Limited
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4. Preface
Today’s world is facing two critical problems: (1) high fuel prices, and (2) climatic changes. Experts suggest that current oil and gas reserves would suffice to
last only a few more decades. It is well known that transport is almost totally dependent on fossil fuels, particularly petroleum-based fuels such as gasoline, diesel
fuel, liquefied petroleum gas, and natural gas. Of special concern are the liquid
fuels used in automobiles. Hence, there has been widespread recent interest in
learning more about obtaining liquid fuels from non-fossil sources. The combination of rising oil prices, issues of security, climate instability, and pollution, and
deepening poverty in rural and agricultural areas, is propelling governments to
enact powerful incentives for the use of these fuels, which is in turn sparking investment. In fact, the world is on the verge of an unprecedented increase in the
production and use of biofuels for transport. Production of grain-based ethanol and
vegetable-oil-based biodiesel is today facing difficulties due to competition with
food supply. This book unifies the production of various usable liquid fuels from
biomass by using a variety of technologies.
Biofuels appear to be a potential alternative “greener” energy substitute for fossil fuels. They are renewable and available throughout the world. Biomass can
contribute to sustainable development and globally environmental preservation
since it is renewable and carbon neutral.
This book on biofuels attempts to address the needs of energy researchers,
chemical engineers, chemical engineering students, energy resources specialists,
engineers, agriculturists, crop cultivators, and others interested in a practical tool
for pursuing their interests in relation to bioenergy. Each chapter in the book starts
with basic/fundamental explanations suitable for general readers and ends with indepth scientific details suitable for expert readers. General readers will include
people interested in learning about solutions for current fuel and environmental
crises. Expert readers will include chemists, chemical engineers, fuel engineers,
agricultural engineers, farming specialists, biologists, fuel processors, policy makers, environmentalists, environmental engineers, automobile engineers, college
v

5. vi
Preface
students, research faculties, etc. The book may even be adopted as a text book for
college courses that deal with renewable energy and/or sustainability.
The Introduction already comprises one seventh of the book; in these pages
emphasis is laid in detail on global energy sources, fossil fuels, and renewables,
i.e., biomass, hydro, wind, solar, geothermal, and marine energy sources. The
second chapter is entitled “Biomass Feedstocks” and includes main biomass
sources, characterization, and valorization. The third chapter is an introduction to
biofuels. Furthermore, processing conditions are discussed briefly, as well as alternative applications of biorenewable feedstocks in the following chapters. The
fourth and fifth chapters on “Liquid and Gaseous Biofuels”, including main liquid
biofuels such as bioethanol, biodiesel, biogas, biohydrogen, liquid and gaseous
fuels from the Fischer–Tropsch synthesis are addressed in detail. The sixth chapter
on “Thermochemical Conversion Processes” covers the utilization of biorenewables for engine fuels and chemicals. The seventh and eighth chapters include
“Biofuel Economy and Biofuel Policy”.
Trabzon, Turkey, July 2008
Ayhan Demirbas

6. Contents
1
2
Introduction.............................................................................................
1.1
Introduction to Energy Sources .....................................................
1.2
Short Supply of Fossil Fuels..........................................................
1.2.1 Petroleum in the World ....................................................
1.2.2 Natural Gas as the Fastest Growing Primary Energy
Source in the World .........................................................
1.2.3 Coal as a Fuel and Chemical Feedstock...........................
1.3
Introduction to Renewable and Biorenewable Sources .................
1.3.1 Non-combustible Renewable Energy Sources .................
1.3.2 Biorenewable Energy Sources .........................................
References.................................................................................................
1
1
4
4
10
15
18
20
31
43
Biomass Feedstocks.................................................................................
2.1
Introduction to Biomass Feedstocks..............................................
2.1.1 Definitions........................................................................
2.1.2 Biomass Feedstocks .........................................................
2.2
Biomass Characterization ..............................................................
2.2.1 Characterization of Biomass Feedstock and Products .....
2.2.2 Biomass Process Design and Development .....................
2.3
Biomass Fuel Analyses..................................................................
2.3.1 Particle Size and Specific Gravity....................................
2.3.2 Ash Content .....................................................................
2.3.3 Moisture Content .............................................................
2.3.4 Extractive Content............................................................
2.3.5 Element Content...............................................................
2.3.6 Structural Constituent Content.........................................
2.3.7 The Energy Value of Biomass .........................................
2.4
Biomass Optimization and Valorization........................................
2.4.1 Fuels from Biomass .........................................................
2.4.2 Chemicals from Biomass .................................................
45
45
46
54
58
59
60
61
62
62
62
62
63
63
63
65
67
70
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7. viii
Contents
2.4.3 Char from Biomass .......................................................... 72
2.4.4 Adhesives from Biomass ................................................. 74
2.4.5 Valorization of Wood....................................................... 78
References................................................................................................. 81
3
Biofuels ....................................................................................................
3.1
Introduction to Biofuels.................................................................
3.1.1 Economic Impact of Biofuels...........................................
3.1.2 Environmental Impact of Biofuels ...................................
References.................................................................................................
87
87
90
94
99
4
Biorenewable Liquid Fuels ....................................................................
4.1
Introduction to Biorenewable Liquid Fuels ...................................
4.1.1 Evaluation of Gasoline-Alcohol Mixtures
as Motor Fuel Alternatives...............................................
4.1.2 Evaluation of Vegetable Oils and Diesel Fuel Mixtures
as Motor Fuel Alternatives...............................................
4.2
Bioalcohols....................................................................................
4.2.1 Alternate Fuels to Gasoline..............................................
4.3
Bioethanol .....................................................................................
4.3.1 Synthetic Ethanol Production Processes ..........................
4.3.2 Production of Ethanol from Biomass ...............................
4.3.3 Sugars from Biomass by Hydrolysis................................
4.3.4 Bioethanol Production by Fermentation
of Carbohydrates ..............................................................
4.3.5 Bioethanol Feedstocks .....................................................
4.3.6 Fuel Properties of Ethanol................................................
4.4
Biomethanol ..................................................................................
4.5
Vegetable Oils ...............................................................................
4.5.1 Alternatives to Diesel Fuel...............................................
4.5.2 Vegetable Oil Resources..................................................
4.5.3 The Use of Vegetable Oils as Diesel Fuel........................
4.5.4 New Biorenewable Fuels from Vegetable Oils................
4.5.5 Properties of Triglycerides...............................................
4.5.6 Triglyceride Economy......................................................
4.6
Biodiesel........................................................................................
4.6.1 The History of Biodiesel ..................................................
4.6.2 Definitions of Biodiesel ...................................................
4.6.3 Biodiesel from Triglycerides via Transesterification .......
4.6.4 Recovery of Glycerol .......................................................
4.6.5 Reaction Mechanism of Transesterification.....................
4.6.6 Current Biodiesel Production Technologies ....................
4.6.7 Biodiesel Production Processes........................................
4.6.8 Basic Plant Equipment Used in Biodiesel Production .....
4.6.9 Fuel Properties of Biodiesels ...........................................
103
103
104
105
105
106
108
108
109
111
115
119
120
122
126
131
133
137
143
153
156
156
158
160
162
171
173
176
180
185
186

8. Contents
4.6.10 Advantages of Biodiesels.................................................
4.6.11 Disadvantages of Biodiesel as Motor Fuel.......................
4.6.12 Engine Performance Tests................................................
4.7
Bio-oils from Biorenewables.........................................................
4.8
Other Alternate Liquid Fuels.........................................................
4.8.1 Glycerol-Based Fuel Oxygenates for Biodiesel
and Diesel Fuel Blends ....................................................
4.8.2 P-series Fuels ...................................................................
4.8.3 Dimethyl Ether (DME) ....................................................
4.8.4 Fischer–Tropsch (FT) Liquid Fuel from Biomass ...........
4.8.5 Other Bio-oxygenated Liquid Fuels.................................
References.................................................................................................
5
6
ix
193
198
199
211
217
217
220
221
221
222
223
Biorenewable Gaseous Fuels..................................................................
5.1
Introduction to Biorenewable Gaseous Fuels ................................
5.2
Biogas............................................................................................
5.2.1 Aerobic Conversion Processes.........................................
5.2.2 Anaerobic Conversion Processes .....................................
5.2.3 Biogas Processing ............................................................
5.2.4 Reactor Technology for Anaerobic Digestion..................
5.3
Landfill Gas...................................................................................
5.4
Crude Gases from Pyrolysis and Gasification of Biomass ............
5.5
Biohydrogen from Biorenewable Feedstocks................................
5.5.1 Hydrogen from Biorenewable Feedstocks
via Thermochemical Conversion Processes .....................
5.5.2 Biohydrogen from Biorenewable Feedstocks ..................
5.6
Gaseous Fuels from Fischer–Tropsch Synthesis of Biomass ........
References.................................................................................................
231
231
232
233
233
236
242
245
248
249
Thermochemical Conversion Processes ................................................
6.1
Introduction to Thermochemical Conversion Processes................
6.2
Thermal Decomposition Mechanisms of Biorenewables ..............
6.3
Hydrothermal Liquefaction of Biorenewable Feedstocks .............
6.3.1 The Role of Water During the HTL Process....................
6.3.2 HTU Applications ............................................................
6.4
Direct Combustion of Biomass......................................................
6.4.1 Combustion Efficiency ....................................................
6.5
Direct Liquefaction........................................................................
6.6
Pyrolysis Processes........................................................................
6.6.1 Reaction Mechanism of Pyrolysis....................................
6.7
Gasification Research and Development.......................................
6.7.1 Biomass Gasification .......................................................
6.7.2 Biomass Gasification Systems .........................................
6.7.3 Electricity from Cogenerative Biomass Firing
Power Plants.....................................................................
261
261
264
266
270
270
271
273
275
277
281
283
285
287
250
254
255
257
293

9. x
Contents
6.7.4 Fischer–Tropsch Synthesis (FTS) .................................... 296
6.7.5 Supercritical Steam Gasification...................................... 299
References................................................................................................. 302
7
8
Biofuel Economy .....................................................................................
7.1
Introduction to Biofuel Economy ..................................................
7.2
Biofuel Economy...........................................................................
7.2.1 Estimation of Biofuel Prices ............................................
7.2.2 Biodiesel Economy ..........................................................
7.2.3 Bioethanol Economy........................................................
7.2.4 Biorenewable Energy Costs
and Biohydrogen Economy..............................................
References.................................................................................................
305
305
307
309
309
313
Biofuel Policy...........................................................................................
8.1
Introduction to Biofuel Policy .......................................................
8.2
Biofuel Policy................................................................................
8.2.1 Biodiesel Policy ...............................................................
8.3
Global Biofuel Projections ............................................................
References.................................................................................................
319
319
320
321
325
328
315
316
Index ................................................................................................................. 331