Plant biomass is attracting increasing attention as a sustainable resource for large-scale production of renewable fuels and chemicals. However, in order to successfully compete with petroleum, it is vital that biomass conversion processes are designed to minimize costs and maximize yields. Advances in pretreatment technology are critical in order to develop high-yielding, cost-competitive routes to renewable fuels and chemicals.

Aqueous Pretreatment of Plant Biomass for Biological and Chemical Conversion to Fuels and Chemicals presents a comprehensive overview of the currently available aqueous pretreatment technologies for cellulosic biomass, highlighting the fundamental chemistry and biology of each method, key attributes and limitations, and opportunities for future advances.

Topics covered include:

• The importance of biomass conversion to fuels
• The role of pretreatment in biological and chemical conversion of biomass
• Composition and structure of biomass, and recalcitrance to conversion
• Fundamentals of biomass pretreatment at low, neutral and high pH
• Ionic liquid and organosolv pretreatments to fractionate biomass
• Comparative data for application of leading pretreatments and effect of enzyme formulations
• Physical and chemical features of pretreated biomass
• Economics of pretreatment for biological processing
• Methods of analysis and enzymatic conversion of biomass streams
• Experimental  pretreatment systems from multiwell plates to pilot plant operations 

This comprehensive reference book provides an authoritative source of information on the pretreatment of cellulosic biomass to aid those experienced in the field to access the most current information on the topic.  It will also be invaluable to those entering the growing field of biomass conversion.

List of Contributors xvii

Foreword xxi

Series Preface xxiii

Preface xxv

Acknowledgements xxvii

1 Introduction 1
Charles E. Wyman

1.1 Cellulosic Biomass: What and Why? 2

1.2 Aqueous Processing of Cellulosic Biomass into Organic Fuels and Chemicals 3

1.3 Attributes for Successful Pretreatment 5

1.4 Pretreatment Options 7

1.5 Possible Blind Spots in the Historic Pretreatment Paradigm 8

1.6 Other Distinguishing Features of Pretreatment Technologies 9

1.7 Book Approach 9

1.8 Overview of Book Chapters 10

2 Cellulosic Biofuels: Importance, Recalcitrance, and Pretreatment 17
Lee Lynd and Mark Laser

2.1 Our Place in History 17

2.2 The Need for Energy from Biomass 17

2.3 The Importance of Cellulosic Biomass 18

2.4 Potential Barriers 18

2.5 Biological and Thermochemical Approaches to the Recalcitrance Barrier 19

2.6 Pretreatment 20

3 Plant Cell Walls: Basics of Structure, Chemistry, Accessibility and the Influence on Conversion 23
Brian H. Davison, Jerry Parks, Mark F. Davis and Bryon S. Donohoe

3.1 Introduction 23

3.2 Biomass Diversity Leads to Variability in Cell-wall Structure and Composition 24

3.3 Processing Options for Accessing the Energy in the Lignocellulosic Matrix 26

3.4 Plant Tissue and Cell Types Respond Differently to Biomass Conversion 28

3.5 The Basics of Plant Cell-wall Structure 29

3.6 Cell-wall Surfaces and Multilamellar Architecture 30

3.7 Cell-wall Ultrastructure and Nanoporosity 31

3.8 Computer Simulation in Understanding Biomass Recalcitrance 32

3.9 Summary 35

4 Biological Conversion of Plants to Fuels and Chemicals and the Effects of Inhibitors 39
Eduardo Ximenes, Youngmi Kim and Michael Ladisch

4.1 Introduction 39

4.2 Overview of Biological Conversion 40

4.3 Enzyme and Ethanol Fermentation Inhibitors Released During Pretreatment and/or Enzyme Hydrolysis 42

4.4 Hydrolysis of Pentose Sugar Oligomers Using Solid-acid Catalysts 50

4.5 Conclusions 56

5 Catalytic Strategies for Converting Lignocellulosic Carbohydrates to Fuels and Chemicals 61
Jesse Q. Bond, David Martin Alonso and James A. Dumesic

5.1 Introduction 61

5.2 Biomass Conversion Strategies 62

5.3 Criteria for Fuels and Chemicals 64

5.4 Primary Feedstocks and Platforms 66

5.5 Sugar Conversion and Key Intermediates 68

5.6 Conclusions 91

6 Fundamentals of Biomass Pretreatment at Low pH 105
Heather L. Trajano and Charles E. Wyman

6.1 Introduction 105

6.2 Effects of Low pH on Biomass Solids 106

6.3 Low-pH Hydrolysis of Cellulose and Hemicellulose 110

6.4 Pretreatment in Support of Chemical Conversion 116

6.5 Models of Low-pH Biomass Reactions 118

6.6 Conclusions 124

7 Fundamentals of Aqueous Pretreatment of Biomass 133
Nathan S. Mosier

7.1 Introduction 133

7.2 Self-ionization of Water Catalyzes Plant Cell-wall Depolymerization 134

7.3 Products from the Hydrolysis of the Plant Cell Wall Contribute to Further Depolymerization 135

7.4 Mechanisms of Aqueous Pretreatment 135

7.5 Impact of Aqueous Pretreatment on Cellulose Digestibility 141

7.6 Practical Applications of Liquid Hot Water Pretreatment 142

7.7 Conclusions 144

8 Fundamentals of Biomass Pretreatment at High pH 149
Rocyo Sierra, Mark Holtzapple and Natalia Piamonte

8.1 Introduction 149

8.2 Chemical Effects of Alkaline Pretreatments on Biomass Composition 150

8.3 Ammonia Pretreatments 157

8.4 Sodium Hydroxide Pretreatments 159

8.5 Alkaline Wet Oxidation 159

8.6 Lime Pretreatment 162

8.7 Pretreatment Severity 165

8.8 Pretreatment Selectivity 165

8.9 Concluding Remarks 167

9 Primer on Ammonia Fiber Expansion Pretreatment 173
S.P.S. Chundawat, B. Bals, T. Campbell, L. Sousa, D. Gao, M. Jin, P. Eranki, R. Garlock, F. Teymouri, V. Balan and B.E. Dale

9.1 Historical Perspective of Ammonia-based Pretreatments 173

9.2 Overview of AFEX and its Physicochemical Impacts 174

9.3 Enzymatic and Microbial Activity on AFEX-treated Biomass 179

9.4 Transgenic Plants and AFEX Pretreatment 187

9.5 Recent Research Developments on AFEX Strategies and Reactor Configurations 189

9.6 Perspectives on AFEX Commercialization 191

9.7 Environmental and Life-cycle Analyses for AFEX-centric Processes 197

9.8 Conclusions 198

10 Fundamentals of Biomass Pretreatment by Fractionation 205
Poulomi Sannigrahi and Arthur J. Ragauskas

10.1 Introduction 205

10.2 Organosolv Pretreatment 206

10.3 Nature of Organosolv Lignin and Chemistry of Organosolv Delignification 214

10.4 Structural and Compositional Characteristics of Cellulose 219

10.5 Co-products of Biomass Fractionation by Organosolv Pretreatment 220

10.6 Conclusions and Recommendations 223

11 Ionic Liquid Pretreatment: Mechanism, Performance, and Challenges 229
Seema Singh and Blake A. Simmons

11.1 Introduction 229

11.2 Ionic Liquid Pretreatment: Mechanism 231

11.3 Ionic Liquid Biomass Pretreatment: Enzymatic Route 234

11.4 Ionic Liquid Pretreatment: Catalytic Route 237

11.5 Factors Impacting Scalability and Cost of Ionic Liquid Pretreatment 239

11.6 Concluding Remarks 240

12 Comparative Performance of Leading Pretreatment Technologies for Biological Conversion of Corn Stover, PoplarWood, and Switchgrass to Sugars 245
Charles E. Wyman, Bruce E. Dale, Venkatesh Balan, Richard T. Elander, Mark T. Holtzapple, Rocyo Sierra Ramirez, Michael R. Ladisch, Nathan Mosier, Y.Y. Lee, Rajesh Gupta, Steven R. Thomas, Bonnie Hames, Ryan Warner and Rajeev Kumar

12.1 Introduction 246

12.2 Materials and Methods 248

12.3 Yields of Xylose and Glucose from Pretreatment and Enzymatic Hydrolysis 251

12.4 Impact of Changes in Biomass Sources 255

12.5 Compositions of Solids Following CAFI Pretreatments 257

12.6 Pretreatment Conditions to Maximize Total Glucose Plus Xylose Yields 260

12.7 Implications of the CAFI Results 261

12.8 Closing Thoughts 262

13 Effects of Enzyme Formulation and Loadings on Conversion of Biomass Pretreated by Leading Technologies 267
Rajesh Gupta and Y.Y. Lee

13.1 Introduction 267

13.2 Synergism among Cellulolytic Enzymes 268

13.3 Hemicellulose Structure and Hemicellulolytic Enzymes 269

13.4 Substrate Characteristics and Enzymatic Hydrolysis 270

13.5 Xylanase Supplementation for Different Pretreated Biomass and Effect of b-Xylosidase 271

13.6 Effect of b-Glucosidase Supplementation 275

13.7 Effect of Pectinase Addition 275

13.8 Effect of Feruloyl Esterase and Acetyl Xylan Esterase Addition 276

13.9 Effect of a-L-arabinofuranosidase and Mannanase Addition 276

13.10 Use of Lignin-degrading Enzymes (LDE) 277

13.11 Effect of Inactive Components on Biomass Hydrolysis 277

13.12 Adsorption and Accessibility of Enzyme with Different Cellulosic Substrates 277

13.13 Tuning Enzyme Formulations to the Feedstock 278

13.14 Summary 279

14 Physical and Chemical Features of Pretreated Biomass that Influence Macro-/Micro-accessibility and Biological Processing 287
Rajeev Kumar and Charles E. Wyman

14.1 Introduction 287

14.2 Definitions of Macro-/Micro-accessibility and Effectiveness 289

14.3 Features Influencing Macro-accessibility and their Impacts on Enzyme Effectiveness 290

14.4 Features Influencing Micro-accessibility and their Impact on Enzymes Effectiveness 295

14.5 Concluding Remarks 299

15 Economics of Pretreatment for Biological Processing 317
Ling Tao, Andy Aden and Richard T. Elander

15.1 Introduction 317

15.2 Importance of Pretreatment 317

15.3 History of Pretreatment Economic Analysis 319

15.4 Methodologies for Economic Assessment 320

15.5 Overview of Pretreatment Technologies 321

15.6 Comparative Pretreatment Economics 322

15.7 Impact of Key Variables on Pretreatment Economics 333

15.8 Future Needs for Evaluation of Pretreatment Economics 337

15.9 Conclusions 338

16 Progress in the Summative Analysis of Biomass Feedstocks for Biofuels Production 341
F.A. Agblevor and J. Pereira

16.1 Introduction 341

16.2 Preparation of Biomass Feedstocks for Analysis 343

16.3 Determination of Non-structural Components of Biomass Feedstocks 344

16.4 Quantitative Determination of Lignin Content of Biomass 346

16.5 Quantitative Analysis of Sugars in Lignocellulosic Biomass 348

16.6 Chemical Hydrolysis of Biomass Polysaccharides 349

16.7 Analysis of Monosaccharides 351

16.8 Gas Chromatography-Mass Spectrometry (GC/MS) 353

16.9 High-performance Liquid Chromatographic Sugar Analysis 353

16.10 NMR Analysis of Biomass Sugars 355

16.11 Conclusions 355

17 High-throughput NIR Analysis of Biomass Pretreatment Streams 361
Bonnie R. Hames

17.1 Introduction 361

17.2 Rapid Analysis Essentials 362

17.3 Summary 372

18 Plant Biomass Characterization: Application of Solution- and Solid-state NMR Spectroscopy 375
Yunqiao Pu, Bassem Hallac and Arthur J. Ragauskas

18.1 Introduction 375

18.2 Plant Biomass Constituents 376

18.3 Solution-state NMR Characterization of Lignin 377

18.4 Solid-state NMR Characterization of Plant Cellulose 387

18.5 Future Perspectives 393

19 Xylooligosaccharides Production, Quantification, and Characterization in Context of Lignocellulosic Biomass Pretreatment 397
Qing Qing, Hongjia Li, Rajeev Kumar and Charles E. Wyman

19.1 Introduction 397

19.2 Xylooligosaccharides Production 400

19.3 Xylooligosaccharides Separation and Purification 403

19.4 Characterization and Quantification of Xylooligosaccharides 408

19.5 Concluding Remarks 414

20 Experimental Pretreatment Systems from Laboratory to Pilot Scale 423
Richard T. Elander

20.1 Introduction 423

20.2 Laboratory-scale Pretreatment Equipment 427

20.3 Pilot-scale Batch Pretreatment Equipment 430

20.4 Pilot-scale Continuous Pretreatment Equipment 433

20.5 Continuous Pilot-scale Pretreatment Reactor Systems 445

20.6 Summary 451

21 Experimental Enzymatic Hydrolysis Systems 457
Todd Lloyd and Chaogang Liu

21.1 Introduction 457

21.2 Cellulases 458

21.3 Hemicellulases 459

21.4 Kinetics of Enzymatic Hydrolysis 460

21.5 Experimental Hydrolysis Systems 466

21.6 Conclusion 471

22 High-throughput Pretreatment and Hydrolysis Systems for Screening Biomass Species in Aqueous Pretreatment of Plant Biomass 477
Jaclyn DeMartini and Charles E. Wyman

22.1 Introduction: The Need for High-throughput Technologies 477

22.2 Previous High-throughput Systems and Application to Pretreatment and Enzymatic Hydrolysis 478

22.3 Current HTPH Systems 479

22.4 Key Steps in HTPH Systems 484

22.5 HTPH Philosophy, Difficulties, and Limitations 488

22.6 Examples of Research Enabled by HTPH Systems 490

22.7 Future Applications 491

22.8 Conclusions and Recommendations 491

23 Laboratory Pretreatment Systems to Understand Biomass Deconstruction 495
Bin Yang and Melvin Tucker

23.1 Introduction 495

23.2 Laboratory-scale Batch Reactors 497

23.3 Laboratory-scale Continuous Pretreatment Reactors 507

23.4 Deconstruction of Biomass with Bench-Scale Pretreatment Systems 509

23.5 Heat and Mass Transfer 511

23.6 Biomass Handling and Comminuting 514

23.7 Construction Materials 514

23.8 Criteria of Reactor Selection and Applications 516

23.9 Summary 519

Acknowledgments 520

References 520

Index