Preface ........................................................ xv
Acknowledgments ............................................... xxi
The Author ................................................... xx»i
Units and Conversion Factors .................................. xxv
Chapter 1 Ethanol as the Leading "First-Generation" Biofuel .... 1
1.1 Introduction ............................................... 1
1.2 Historical Development of Ethanol as a Fuel from
Neolithic Times to the Twentieth Century ................... 1
1.3 Oil Supply and Oil Price in the Twentieth Century:
Necessity and Alternative Fuel Programs .................... 6
1.4 Case Study 1: Brazil and Sugarcane Ethanol ................ 10
1.5 Case Study 2: Starch-Based Ethanol in the United States ... 18
1.6 Thermodynamic and Environmental Aspects of Ethanol as
a Biofuel ................................................. 31
1.6.1 Net Energy Balance ................................. 31
1.6.2 Effects on Emissions of Greenhouse Gases and
Other Pollutants ................................... 37
1.7 Summary ................................................... 41
References ..................................................... 41
Chapter 2 Cellulosic Ethanol as a "Second-Generation"
Biofuel ............................................. 45
2.1 Introduction .............................................. 45
2.2 Bioethanol and Cellulosic Ethanol: The Rise of Biomass-
Based Biofuels ............................................ 45
2.3 Structural and Industrial Chemistry of Cellulosic
Biomass ................................................... 46
2.3.1 Cellulose, Hemicelluloses, and Lignin .............. 46
2.3.2 Lignocellulose as a Biochemical Resource ........... 51
2.3.3 Pretreatment of Lignocellulosic Materials .......... 53
2.3.3.1 Physical and Chemical Pretreatment
of Lignocellulosic Biomass ................ 53
2.3.3.2 Acid Hydrolysis of Pretreated
Lignocellulosic Biomass ................... 59
2.4 Cellulases: Biochemistry, Molecular Biology, and
Biotechnology ............................................. 61
2.4.1 Enzymology of Cellulose Degradation by
Cellulases ......................................... 61
2.4.2 Cellulases in Lignocellulosic Feedstock
Processing ......................................... 65
2.4.2 and the CRC Press Web site at
http://www.crcpress.com
2.4.3 Molecular Biology and Biotechnology of Cellulase
Production ......................................... 68
2.4.3.1 Physiological Regulation of Cellulase
Production ................................ 68
2.4.3.2 Regulatory Genes Involved in Cellulase
Production ................................ 69
2.4.3.3 New-Generation Cellulases ................. 70
2.4.3.4 Novel Molecular Features of Cellulases .... 74
2.4.3.5 Immobilized Cellulases .................... 75
2.5 Hemicellulases: New Horizons in Energy Biotechnology ...... 75
2.5.1 A Multiplicity of Hemicellulases ................... 75
2.5.2 Hemicellulases in the Processing of
Lignocellulosic Biomass ............................ 78
2.5.3 Molecular Biology of Hemicellulases ................ 79
2.5.4 Multifunctional Hemicellulases? .................... 79
2.6 Lignin-Degrading Enzymes as Aids to Saccharification ...... 80
2.7 Commercial Choices of Cellulosic Feedstocks for Ethanol
Production ................................................ 81
2.8 Biotechnology and Platform Technologies for Cellulosic
Ethanol ................................................... 82
2.9 Summary ................................................... 83
References ..................................................... 83
Chapter 3 Microbiology of Cellulosic Ethanol Production I:
Yeasts .............................................. 91
3.1 Introduction .............................................. 91
3.2 Traditional Ethanologenic Yeasts .......................... 91
3.2.1 Conventional Yeasts ................................ 92
3.2.2 Nonconventional Yeasts ............................. 99
3.3 Metabolic Engineering of Yeasts for Cellulosic Ethanol ... 100
3.3.1 Increased Pentose Utilization by Ethanologenic
Yeasts by Genetic Manipulation with Yeast Genes
for Xylose Metabolism via Xylitol ................. 100
3.3.2 Increased Pentose Utilization by Ethanologenic
Yeasts by Genetic Manipulation with Genes for
Xylose Isomerization .............................. 106
3.3.3 Engineering Arabinose Utilization by
Ethanologenic Yeasts .............................. 107
3.3.4 Comparison of Industrial and Laboratory Yeast
Strains for Ethanol Production .................... 109
3.3.5 Improved Ethanol Production by Naturally
Pentose-Utilizing Yeasts .......................... 115
3.4 Toward the Perfect Yeast Ethanologen? .................... 116
3.4.1 "Omic" Analyses of Yeast Metabolism during
Ethanol Production ................................ 117
3.4.2 Stress Responses in Yeast Ethanologens ............ 120
3.5 Summary .................................................. 121
References .................................................... 122
Chapter 4 Microbiology of Cellulosic Ethanol Production II:
Bacteria ........................................... 131
4.1 Introduction ............................................. 131
4.2 Assembling Gene Arrays in Bacteria for Ethanol
Production ............................................... 131
4.2.1 Metabolic Routes in Bacteria for Sugar
Metabolism and Ethanol Formation .................. 132
4.2.2 Genetic and Metabolic Engineering of Bacteria
for Cellulosic Ethanol Production ................. 135
4.2.2.1 Recombinant Escherichia coli: Lineages
and Metabolic Capabilities ............... 135
4.2.2.2 Engineering Zymomonas mobilis for
Xylose and Arabinose Metabolism .......... 143
4.2.2.3 Development of Klebsiella Strains for
Ethanol Production ....................... 146
4.2.2.4 Other Bacterial Species .................. 148
4.3 Thermophilic Species and Cellulosome Bioproduction
Technologies ............................................. 149
4.4 "Designer" Cells and Synthetic Organisms ................. 150
4.5 Summary .................................................. 151
References .................................................... 152
Chapter 5 Biochemical Engineering of Cellulosic Ethanol ...... 159
5.1 Introduction ............................................. 159
5.2 Case Study: The logen Corporation Process with Wheat
Straw .................................................... 159
5.3 Biomass Substrate Pretreatment Strategies ................ 162
5.3.1 Wheat Straw ....................................... 163
5.3.2 Switchgrass ....................................... 165
5.3.3 Corn Stover ....................................... 166
5.3.4 Softwoods ......................................... 170
5.3.5 Sugarcane Bagasse ................................. 173
5.3.6 Other Large-Scale Agricultural and Forestry
Biomass Feedstocks ................................ 174
5.4 Fermentation Media and the Very High Gravity Concept ..... 175
5.4.1 Fermentation Media for Ethanol Production ......... 176
5.4.2 High-Concentration Media Developed for Alcohol
Fermentations ..................................... 177
5.5 Fermentor Design and Novel Fermentor Technologies ........ 182
5.5.1 Continuous Fermentations for Ethanol Production ... 182
5.5.2 Fed-Batch Fermentations ........................... 187
5.5.3 Immobilized Yeast and Bacterial Cell Production
Designs ........................................... 189
5.5.4 Contamination Events and Buildup in Fuel
Ethanol Plants .................................... 192
5.6 Simultaneous Saccharification and Fermentation and
Consolidated Bioprocessing ............................... 192
5.7 Downstream Processing and By-Products .................... 196
5.7.1 Ethanol Recovery from Fermented Broths ............ 196
5.7.2 Continuous Ethanol Recovery from Fermentors ....... 198
5.7.3 Solid By-Products from Ethanol Fermentations ...... 199
5.8 Summary .................................................. 202
References .................................................... 203
Chapter 6 The Economics of Fuel Ethanol ...................... 217
6.1 Introduction ............................................. 217
6.2 Market Forces and Incentives ............................. 217
6.2.1 The Impact of Oil Prices on the Future of
Biofuels after 1980 ............................... 217
6.2.2 Production Price, Taxation, and Incentives in
the Market Economy ................................ 218
6.3 Cost Models for Fuel Ethanol Production .................. 221
6.3.1 Early Benchmarking Studies of Corn and
Lignocellulosic Ethanol in the United States ...... 222
6.3.1.1 Corn-Derived Ethanol in 1978 ............. 222
6.3.1.2 Wheat-Straw-Derived Ethanol in 1978 ...... 224
6.3.1.3 Fuel Ethanol from Sugarcane Molasses ..... 226
6.3.1.4 Farm-Scale Ethanol Production ............ 226
6.3.2 Corn Ethanol in the 1980s: Rising Industrial
Ethanol Prices and the Development of the
Incentive Culture ................................. 228
6.3.3 Western Europe in the Mid-1980s: Assessments of
Biofuels Programs Made at a Time of Falling Real
Oil Prices ........................................ 231
6.3.4 Brazilian Sugarcane Ethanol in 1985: After the
First Decade of the PROÁLCOOL Program to
Substitute for Imported Oil ....................... 234
6.3.5 Economics of U.S. Corn and Biomass Ethanol
Economics in the Mid-1990s ........................ 234
6.3.6 Case Study: The View from Sweden .................. 236
6.3.7 Subsequent Assessments of Lignocellulosic
Ethanol in Europe and the United States ........... 240
6.3.7.1 Complete Process Cost Models ............. 240
6.3.7.2 Reviews of "Gray" Literature
Estimates and Economic Analyses .......... 243
6.4 Pilot Plant and Industrial Extrapolations for
Cellulosic Ethanol ....................................... 245
6.4.1 Near-Future Projections for Cellulosic Ethanol
Production Costs .................................. 245
6.4.2 Short- to Medium-Term Technical Process
Improvements and Their Anticipated Economic
Impacts ........................................... 246
6.4.3 Bioprocess Economics: A Chinese Perspective ....... 250
6.5 Governmental and Macroeconomic Factors ................... 253
6.5.1 Mandatory Biofuels Targets ........................ 253
6.5.2 Impact of Fuel Economy on Ethanol Demand
for Gasoline Blends ............................... 257
6.5.3 Biofuels Pricing in the Era of Carbon Taxation .... 258
6.6 Summary .................................................. 259
References .................................................... 260
Chapter 7 Advanced Biofuels: The Widening Portfolio of
Alternatives to Ethanol ............................ 265
7.1 Introduction ............................................. 265
7.2 Biobutanol and ABE ....................................... 265
7.3 Bacterial Production of C3-C7 Alcohols and Related
Compounds ................................................ 268
7.4 Glycerol ................................................. 271
7.5 The MixAlco Process ...................................... 272
7.6 Biohydrogen .............................................. 273
7.6.1 The Hydrogen Economy and Fuel Cell Technologies ... 273
7.6.2 Bioproduction of Gases: Methane and H2 as
Products of Anaerobic Digestion ................... 276
7.6.2.1 Heterotrophic Microbes Producing H2
by Hydrogenase Activity .................. 277
7.6.2.2 Nitrogen-Fixing Microorganisms ........... 280
7.6.2.3 Development of "Dark" H2 Production
Systems .................................. 281
7.6.3 Production of H2 by Photosynthetic Organisms ...... 284
7.7 Microbial Fuel Cells: Eliminating the Middlemen of
Energy Carriers .......................................... 291
7.8 Summary .................................................. 293
References .................................................... 293
Chapter 8 Chemically Produced Biofuels ....................... 301
8.1 Introduction ............................................. 301
8.2 Biodiesel: Chemistry and Production Processes ............ 301
8.2.1 Vegetable Oils and Chemically Processed
Biofuels .......................................... 301
8.2.2 Biodiesel Composition and Production Processes .... 303
8.2.3 Biodiesel Economics ............................... 308
8.2.4 Energetics of Biodiesel Production and Effects
on Greenhouse Gas Emissions ....................... 311
8.2.5 Case Study 1: Hydrogenated Plant Oils and "Green
Diesel" ........................................... 315
8.2.6 Case Study 2: Enzymes for Biodiesel Production .... 316
8.3 Fischer-Tropsch Diesel: Chemical Biomass-Liquid Fuel
Transformations .......................................... 318
8.3.1 The Renascence of an Old Chemistry for Biomass-
Based Fuels? ...................................... 318
8.3.2 Economics and Environmental Impacts of FT
Diesel ............................................ 320
8.4 Biodiesel from Microalgae and Microbes ................... 322
8.4.1 Marine and Aquatic Biotechnology .................. 322
8.4.2 Microdiesel ....................................... 325
8.5 Chemical Conversions of Glycerol Produced by
Fermentation ............................................. 326
8.6 Chemical Routes for the Production of Monooxygenated
C6 Liquid Fuels from Biomass Carbohydrates ............... 327
8.7 Biomethanol and Biodimethylether ......................... 328
8.8 Chemistry and the Emergence of the Hydrogen Economy ...... 330
8.9 Summary .................................................. 333
References .................................................... 334
Chapter 9 Sustainability of Biofuels Production .............. 341
9.1 Introduction ............................................. 341
9.2 Delivering Biomass Feedstocks for Cellulosic Ethanol
Production: The Logistics of a New Industry .............. 341
9.2.1 Upstream Factors: Biomass Collection and
Delivery .......................................... 344
9.2.2 Limitations Imposed by Land Availability and
Land Use .......................................... 346
9.3 Sustainable Development and Biomass Production ........... 354
9.3.1 Definitions, Semantics, and Analysis .............. 354
9.3.2 Case Study: Sustainability of Brazilian
Sugarcane Ethanol ................................. 360
9.3.3 Future Horizons for Cane Sugar Ethanol ............ 365
9.4 Bioenergy Crops and Genetically Manipulated Plants ....... 367
9.4.1 Engineering Resistance Traits for Biotic and
Abiotic Stresses .................................. 368
9.4.2 Bioengineering Increased Crop Yield ............... 369
9.4.3 Optimizing Traits for Energy Crops Intended
for Biofuel Production ............................ 371
9.4.4 Genetic Engineering of Dual-Use Food Plants
and Dedicated Energy Crops ........................ 374
9.5 Summary .................................................. 376
References .................................................... 377
Chapter 10 Biofuels as Products of Integrated Bioprocesses
(Biorefineries) .................................... 383
10.1 Introduction ............................................. 383
10.2 The Biorefinery Concept .................................. 383
10.3 Biorefinery Entry Routes ................................. 386
10.3.1 Fermentation of Biomass-Derived Substrates ........ 387
10.3.2 Biomass Gasification .............................. 390
10.4 Biorefinery Pivotal Products ............................. 392
10.4.1 Case Study 1: Succinic Acid ....................... 395
10.4.2 Case Study 2: Xylitol and Rare Sugars as Fine
Chemicals ......................................... 400
10.4.3 Case Study 3: Glycerol ............................ 403
10.5 Central Substrates and Biorefinery Flexibility ........... 405
10.6 When Will the Biobased Economy Be Possible and When
Will It Be Unavoidable? .................................. 407
10.7 Summary .................................................. 413
References .................................................... 413
Index ......................................................... 421
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