Comprehensive coverage on the growing science and technology of producing ethanol from the world's abundant cellulosic biomass

The inevitable decline in petroleum reserves and its impact on gasoline prices, combined with climate change concerns, have contributed to current interest in renewable fuels. Bioethanol is the most successful renewable transport fuel—with corn and sugarcane ethanol currently in wide use as blend-in fuels in the United States, Brazil, and a few other countries. However, there are a number of major drawbacks in these first-generation biofuels, such as their effect on food prices, net energy balance, and poor greenhouse gas mitigation. Alternatively, cellulosic ethanol can be produced from abundant lignocellulosic biomass forms such as agricultural or municipal wastes, forest residues, fast growing trees, or grasses grown in marginal lands, and should be producible in substantial amounts to meet growing global energy demand.

The Handbook of Cellulosic Ethanol covers all aspects of this new and vital alternative fuel source, providing readers with the background, scientific theory, and recent research progress in producing cellulosic ethanol via different biochemical routes, as well as future directions. The seventeen chapters include information on:

• Advantages of cellulosic ethanol over first-generation ethanol as a transportation fuel
• Various biomass feedstocks that can be used to make cellulosic ethanol
• Details of the aqueous phase or cellulolysis route, pretreatment, enzyme or acid saccharification, fermentation, simultaneous saccharification fermentation, consolidated bioprocessing, genetically modified microorganisms, and yeasts
• Details of the syngas fermentation or thermochemical route, gasifiers, syngas cleaning, microorganisms for syngas fermentation, and chemical catalysts for syngas-to-ethanol conversion
• Distillation and dehydration to fuel-grade ethanol
• Techno-economical aspects and the future of cellulosic ethanol

Readership

Chemical engineers, chemists, and technicians working on renewable energy and fuels in industry, research institutions, and universities. The Handbook can also be used by students interested in biofuels and renewable energy issues.

Preface xvii

Part 1 Introduction to Cellulosic Ethanol 1

1 Renewable Fuels 3

1.1 Introduction 3

1.2 Renewable Energy 6

1.3 Biofuels 7

1.4 Renewable Energy in the United States 14

1.5 Renewable Fuel Legislature in the United States 20

References 25

2 Bioethanol as a Transportation Fuel 29

2.1 Introduction — History of Bioethanol as a Transportation Fuel 29

2.2 Alcohol Fuels 31

2.3 Fuel Characteristics of Ethanol 31

2.4 Corn and Sugarcane Ethanol 34

2.5 Advantages of Cellulosic Ethanol 35

References 40

3 Feedstocks for Cellulosic Ethanol Production 43

3.1 Introduction 43

3.2 Cellulosic Ethanol Feedstock Types 46

3.3 Potential of Agricultural Wastes 46

3.4 Major Crop Residue Feedstock 50

3.5 Forestry Residue, Logging and Mill Residue 68

3.6 Grass Feedstocks 70

3.7 Purpose-Grown Trees as Feedstock 92

3.8 Municipal and Other Waste as Feedstock for Cellulosic Ethanol 101

References 108

Part 2 Aqueous Phase Biomass Hydrolysis Route 131

4 Challenges in Aqueous-Phase Biomass Hydrolysis Route: Recalcitrance 133

4.1 Introduction – Two Ways to Produce Cellulosic Ethanol 133

4.2 Challenges in Aqueous-Phase Biomass Hydrolysis 134

4.3 Structure of Plant Cells and Lignocellulosic Biomass 135

4.4 Major Components of Lignocellulosic Biomass 137

4.5 Cellulose Recalcitrance 140

References 143

5 Pretreatment of Lignocellulosic Biomass 147

5.1 Introduction 147

5.2 Different Categories of Pretreatment Methods 150

5.3 Physical Pretreatment 150

5.4 Physicochemical Pretreatment 153

5.5 Chemical Pretreatment 177

5.6 Biological Pretreatment 190

5.7 Conclusion 191

References 197

6 Enzymatic Hydrolysis of Cellulose and Hemicellulose 219

6.1 Introduction 219

6.2 Enzymatic Actions on Lignocellulosic Biomass 220

6.3 Enzymatic Hydrolysis of Cellulose 221

6.4 Enzymatic Hydrolysis of Hemicellulose 233

6.5 Future Directions in Enzymatic Cellulose Hydrolysis Research 237

References 239

7 Acid Hydrolysis of Cellulose and Hemicellulose 247

7.1 Introduction 247

7.2 Concentrated Acid Hydrolysis 248

7.3 Dilute Acid Hydrolysis 252

7.4 Ionic Liquid-Based Direct Acid Hydrolysis 262

7.5 Solid Acid Hydrolysis 269

References 275

8 Fermentation I – Microorganisms 283

8.1 Introduction 283

8.2 Detoxification of Lignocellulosic Hydrolyzate 284

8.3 Separate Hydrolysis and Fermentation (SHF) 288

8.4 Microorganisms Used in the Fermentation 288

8.5 Fermentation Using Yeasts 289

8.6 Fermentation Using Bacteria 294

8.7 Simultaneous Saccharification and Fermentation (SSF) 300

8.8 Immobilization of Yeast 317

References 322

9 Fermentation II – Fermenter Configuration and Design 339

9.1 Introduction 339

9.2 Batch Fermentation 340

9.2.1 Examples of Batch Fermentation 340

9.3 Fed-Batch Fermentation 340

9.4 Continuous Fermentation 346

9.5 New Directions in Fermenter Configuration and Design 352

References 353

10 Separation and Uses of Lignin 357

10.1 Introduction 357

10.2 Structure of Lignin 359

10.3 Separation of Lignin in the Cellulosic Ethanol Process 360

10.4 Physical and Chemical Properties of Lignin 363

10.5 Applications of Lignin 365

10.5.1 Lignin-Based Phenol Formaldehyde Resins 365

References 373

Part 3 Biomass Gasification Route 381

11 Biomass Pyrolysis and Gasifier Designs 383

11.1 Introduction 383

11.2 Chemistry of the Conversion of Biomass to Syngas 384

11.3 Classifications of Biomass Gasifiers 387

11.4 Fixed-Bed Gasifier 388

11.5 Fluidized-Bed Gasifier 389

11.6 Bubbling Fluidized-Bed (BFB) Gasifier 390

11.7 Circulating Fluidized-Bed (CFB) Gasifier 392

11.8 Allothermal Dual Fluidized-Bed (DFB) Gasifier 392

11.9 Entrained-Flow Gasifier 395

11.10 Syngas Cleaning 396

11.11 Tar Control and Treatment Methods 403

References 403

12 Conversion of Syngas to Ethanol Using Microorganisms 407

12.1 Introduction 407

12.2 Metabolic Pathways 410

12.3 Microorganisms Used in Syngas Fermentation 414

12.4 Biochemical Reactions in Syngas Fermentation 414

12.5 The Effects of Operation Parameters on Ethanol Yield 416

12.6 Syngas Fermentation Reactors 424

12.7 Industrial-Scale Syngas Fermentation and Commercialization 426

References 427

13 Conversion of Syngas to Ethanol Using Chemical Catalysts 433

13.1 Introduction 433

13.2 Homogeneous Catalysts 434

13.3 Introduction to Heterogeneous Catalysts 437

13.4 Heterogeneous Catalyst Types 437

13.5 Rhodium-Based Catalysts 438

13.6 Copper-Based Modified Methanol Synthesis Catalysts 449

13.7 Modified Fischer-Tropsch-Type Catalysts 455

13.8 Molybdenum-Based Catalysts 456

13.9 Catalyst Selection 459

References 461

Part 4 Processing of Cellulosic Ethanol 467

14 Distillation of Ethanol 469

14.1 Introduction 469

14.2 Distillation of the Beer 470

14.3 How Distillation Works 470

14.4 Conventional Ethanol Distillation System 472

14.5 Steam Generation for Distillation Process 475

14.6 Studies on Development of Hybrid Systems for Ethanol Distillation 476

References 479

15 Dehydration to Fuel Grade Ethanol 481

15.1 Introduction 481

15.2 Dehydration Methods 482

15.3 Adsorption Method 482

15.4 Azeotropic Distillation Method 488

15.5 Extractive Distillation Methods 491

15.6 Membrane-Based Pervaporation Methods 494

15.7 Other Dehydration Methods 498

15.8 Comparisons of Common Dehydration Methods 498

References 500

Part 5 Fuel Ethanol Standards and Process Evaluation 507

16 Fuel Ethanol Standards, Testing and Blending 509

16.1 Introduction 509

16.2 Fuel Grade Ethanol Standards in the United States 510

16.3 Quality Assurance and Test Methods 514

16.4 European Fuel Ethanol Standards 517

16.5 Material Safety Data Sheet (MSDS) for Denatured Fuel Ethanol 518

16.6 Gasoline Ethanol Blends 520

16.7 Engine Performance Using Gasoline Ethanol Blends 524

References 528

17 Techno-Economic Analysis and Future of Cellulosic Ethanol 531

17.1 Introduction 531

17.2 Techno-Economic Aspects of Biomass Hydrolysis Process 532

17.3 Techno-Economic Aspects of Biomass Gasification Process 533

17.4 Comparison of Biomass Hydrolysis and Gasification Processes 539

17.5 Some Cellulosic Plants around the World 540

17.6 Challenges in Cellulosic Ethanol 550

17.7 Future Prospects of Cellulosic Ethanol 553

References 554

Appendix 1 557

Index