Chemical and biochemical catalysis for next generation biofuels

The development of renewable and sustainable lignocellulosic biofuels is currently receiving worldwide attention and investment. Despite decades of research, there remain significant challenges to be overcome before these biofuels can be produced in large volumes at competitive prices. One obstacle is the lack of efficient and affordable catalytic systems to dissolve and hydrolyze polysaccharides into sugars. These sugars are then fed to microrganisms and fermented into biofuels. The price of these catalysts, be they biological, thermochemical, or chemical in nature, represent one of the largest costs in the conversion process. There are a number of catalytic schemes, each with their own advantages and disadvantages, available. This book presents a general yet substantial review of the most promising processes and the spectrum of biomass pretreatment, enzymes, chemical catalysts, and hybrid approaches of hydrolyzing biomass into fermentable sugars. It is the only currently available book that compares the biochemical, chemical, and thermochemical conversion processes to biofuel production.

Author Notes

Dr Blake Simmons is at the Sandia National Laboratories/Joint BioEnergy Institute, Emeryville, CA, USA.

Blake A. SimmonsJ. Will MedlinDeepti Tanjoie and Jian Shi and Charles E. WymanDeepti Tanjoie and Jian Shi and Charles E. WymanVenkatesh Balan and Bryan Bah and Leonardo da Costa Sousa and Rebecca Garlock and Bruce E. DaleSupratim Datta and Rajat SapraChristopher R. ShaddixTed J. Amundsen and Alexander Katz

Chapter 1 Introduction	p. 1
References	p. 4
Chapter 2 Biomass Availability and Sustainability for BiofuelsDominique Loqué and Aymerick Eudes and Fan Yang
2.1 Introduction	p. 5
2.2 General Land Types	p. 6
2.2.1 Forest Lands	p. 6
2.2.2 Agricultural Lands	p. 7
2.2.3 Desert Lands	p. 7
2.2.4 Tundra Lands	p. 8
2.3 Potential Bioenergy Feedstock Lands	p. 8
2.4 Bioenergy Feedstocks	p. 9
2.5 Degraded and Non-productive Lands	p. 13
2.5.1 Abandoned Lands	p. 14
2.5.2 Dry Lands	p. 15
2.5.3 Land Polluted with Heavy Metals and Other Contaminants	p. 19
2.5.4 Saline Lands	p. 20
2.6 Waste Biomass	p. 21
2.6.1 Forest Land Residues	p. 22
2.6.2 Farmland Residues	p. 23
2.6.3 Urban Land Residues	p. 24
2.7 Conclusions	p. 25
Acknowledgements	p. 26
References	p. 26
Chapter 3 Surface Science Studies Relevant for Metal-catalyzed Biorefining Reactions	p. 33
Chapter 4 Dilute Acid and Hydrothermal Pretreatment of Cellulosic Biomass	p. 64
3.1 Introduction	p. 33
3.2 Surface Science Contributions to Catalyst Design	p. 34
3.2.1 Ethylene Epoxidation	p. 35
3.2.2 Acetylene Hydrogenation	p. 35
3.3 Biorefining Routes: Key Intermediates and Transformations	p. 36
3.3.1 Biomass Gasification Followed by Synthesis Gas Upgrading	p. 36
3.3.2 Catalytic Pyrolysis and Catalytic Upgrading	p. 37
3.3.3 Hydrolysis of Cellulosic Biomass	p. 37
3.3.4 Aqueous Phase Processing of Sugars	p. 38
3.3.5 Upgrading of Fermentation Products	p. 38
3.4 Surface Science Methodology	p. 38
3.4.1 Adsorption and Reaction of Key Functional Groups on Metals	p. 41
3.4.2 Olefins	p. 41
3.4.3 Alcohols	p. 42
3.4.4 Aldehydes and Ketones	p. 43
3.4.5 Ethers and Epoxides	p. 44
3.4.6 Carboxylic Acids and Esters	p. 44
3.4.7 Summary of Adsorption and Reaction Trends	p. 45
3.5 Reactions of Multifunctional Oxygenates on Metals	p. 45
3.5.1 Unsaturated Oxygenates	p. 46
3.5.2 Polyols	p. 51
3.6 Relating Surface Studies to Bioreflning Catalysis:Case Studies	p. 52
3.6.1 Reforming of Polyols and Sugars	p. 52
3.6.2 Hydrogenation of Dicarboxylic Acids	p. 54
3.6.3 Reactions of Hydroxymethylfurfural (HMF)	p. 55
3.7 Summary and Directions of Future Research	p. 56
Acknowledgment	p. 57
References	p. 57
Chapter 4 Dilute Acid and Hydrothermal Pretreatment of Cellulosic Biomass	p. 64
4.1 Introduction	p. 64
4.2 Pretreatment Chemistry	p. 66
4.3 Laboratory Reactors	p. 68
4.3.1 Batch Reactors	p. 68
4.3.2 Continuous Reactors	p. 73
4.4 Reaction Kinetics and Severity Factor	p. 74
4.5 Pretreatment Effects on the Digestibility of Post-pretreatment Solids	p. 78
4.6 Feedstock Considerations	p. 79
4.7 Comparison of Hydrothermal and Dilute Acid Pretreatment Performance	p. 80
4.8 Pretreatment Economics	p. 81
4.9 Conclusions	p. 83
Acknowledgements	p. 84
References	p. 84
Chapter 5 A Short Review on Ammonia-based Lignocellulosic Biomass Pretreatment	p. 89
5.1 Introduction	p. 89
5.2 Alkaline Pretreatment Processes	p. 90
5.2.1 Different Types of Alkali-based Pretreatment Processes	p. 92
5.2.2 Ammonia and its Properties	p. 92
5.2.3 History of Using Ammonia as a Pretreatment Chemicalp92
5.3 Details of the Afex Process	p. 94
5.3.1 Pretreatment Variables	p. 95
5.3.2 Fundamental Understanding of the Alkaline Pretreatment Process	p. 95
5.3.3 Reactions between Ammonia and Lignocellulosic Biomass	p. 97
5.3.4 Afex Degradation Products	p. 97
5.3.5 Waste Streams and Environmental Issues	p. 98
5.4 Enzymatic Hydrolysis	p. 98
5.5 Biomass Composition and Plant Species Classification	p. 99
5.6 Afex Performance on Grasses	p. 101
5.6.1 Afex on Corn Stover	p. 101
5.6.2 Afex on Switchgrass	p. 105
5.6.3 Afex on Rice Straw	p. 105
5.6.4 Afex on Sugarcane Bagasse	p. 106
5.6.5 Afex on Sorghum	p. 106
5.6.6 Afex on Miscanthus	p. 106
5.6.7 Afex on other Grasses and Biomass	p. 107
5.7 Afex Comparison on Grasses versus Hardwoods	p. 107
5.8 Advantages of Afex during Fermentation	p. 108
5.9 Logistics and Regional Biomass Processing Centers	p. 108
5.10 Pellets and Logistics of Transportation	p. 109
5.11 Storage and Stability	p. 109
5.12 Co-producing Animal Feeds and Biofuels using Afex Pretreatment	p. 110
5.13 Economic Considerations	p. 110
5.14 Conclusions	p. 111
Acknowledgements	p. 111
References	p. 111
Chapter 6 Cellulases and Hemicellulases for Biomass Degradation: An Introduction	p. 115
6.1 Introduction	p. 115
6.2 Why is Lignocellulose so Hard to Break Down?	p. 116
6.3 Pretreatment of Cellulose	p. 117
6.4 Cellulases	p. 118
6.4.1 Mechanism of Cellulases	p. 119
6.4.2 Cellulase Architecture	p. 120
6.4.3 Catalytic Domain	p. 121
6.5 Carbohydrate-binding Modules	p. 121
6.5.1 Type A Surface Binding Cbms
6.5.2 Type B Polysaccharide-chain-binding Cbms	p. 122
6.5.3 Type C Small-sugar-binding Cbms	p. 122
6.6 Cbm Functions	p. 123\|3
6.6.2 The Targeting Effect	p. 123
6.6.3 Multiple Cbms	p. 124
6.7 Enzyme Optimization and Engineering	p. 124
6.8 Cellulosomes	p. 125
6.8.1 Non-Catalytic Subunit: Scaflbldin	p. 126
6.8.2 The Cohesin-dockerin Interaction	p. 127
6.9 Hemicellulases	p. 127
6.9.1 Hemicellulose Types and Specificity	p. 127
6.9.2 Depolymerlzation Enzymes	p. 127
6.9.3 Accessory Enzymes	p. 130
6.10 Thermophilic Cellulolytic and Hemicelluloytic Enzymes	p. 130
6.11 Biochemical Conversion of Sugars to Biofuels	p. 131
6.12 Summary	p. 132
Acknowledgements	p. 132
References	p. 133
Chapter 7 Advances in Gasification for Biofuel Production	p. 136
7.1 Introduction	p. 136
7.2 Biomass Feedstocks for Use in Gasifiers	p. 138
7.3 Gasification Technologies	p. 139
7.3.1 Operational Characteristics of Gasifiers	p. 140
7.3.2 Moderate Temperature, Indirect Gasification	p. 142
7.3.3 Oxygen-blown Direct Gasification	p. 146
7.3.4 Plasma Gasification	p. 148
7.4 Gas Cleanup	p. 149
7.5 Conclusions	p. 152
References p. 153
Chapter 8 Bioinspired Catalysts for Biofuels: Challenges and Future Directions	p. 156
8.1 Introduction	p. 156
8.2 Substrate Binding	p. 157
8.2.1 Competitive Aqueous Solvation	p. 158
8.2.2 Positional Requirements	p. 159
8.3 Acyl Transfer	p. 160
8.3.1 Hydrogen Bonding Molecular Receptors	p. 160
8.3.2 Aqueous Hydrogen Bonding Molecular Receptors	p. 162
8.4 Ester Hydrolysis	p. 163
8.4.1 Aqueous Hydrogen Bonding Molecular Receptors	p. 165
8.5 Glycosidic Bond Hydrolysis	p. 166
8.5.1 Intramolecularity	p. 167
8.5.2 Cyclodextrins	p. 170
8.5.3 Catalytic Antibodies	p. 171
8.5.4 Combinatorial Polymer Catalysts	p. 172
8.6 Aldol Condensations	p. 173
8.6.1 Homogeneous Organocatalysis	p. 173
8.6.2 Heterogeneous Amine-functionalized Silica	p. 174
8.7 Ketonization	p. 177
8.8 Dehydration	p. 177
8.9 Lignin Depolymerization	p. 179
8.10 Conclusions and Future Directions	p. 180
References	p. 181
Subject Index	p. 185

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