EFFICIENCY OF BIOMASS ENERGY

EFFICIENCY OF BIOMASS ENERGYAn Exergy Approach to Biofuels,

Power, and Biorefineries

Krzysztof J. Ptasinski

Copyright 2016 by John Wiley & Sons, Inc. All rights reserved.

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ISBN: 978-1-118-70210-9

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

Contents

Preface xv

Acknowledgments xix

About the Author xxi

PART I | Background and Outline

Chapter 1 | Bioenergy Systems: An Overview 3

1.1 Energy and the Environment 31.1.1 Global Energy Consumption 31.1.2 Conversion and Utilization of Energy 71.1.3 Fossil Fuel Resources 81.1.4 Environmental Impact of Fossil Fuels Use 91.1.5 Renewable Energy 11

1.2 Biomass as a Renewable Energy Source 131.2.1 Introduction 131.2.2 Historical Development and Potential of Bioenergy 141.2.3 Biomass Resources 161.2.4 Biomass Properties 171.2.5 Environmental Impact of Bioenergy 191.2.6 Economics of Bioenergy 21

1.3 Biomass Conversion Processes 221.3.1 Introduction 221.3.2 Upgrading Technologies 231.3.3 Thermochemical Conversion Processes 241.3.4 Biochemical Conversion Processes 251.3.5 Chemical Conversion Processes 26

1.4 Utilization of Biomass 271.4.1 Introduction 271.4.2 Biofuels 291.4.3 Electric Power Generation 311.4.4 Heat Production 321.4.5 Chemical Biorefinery 33

1.5 Closing Remarks 34References 34

Chapter 2 | Exergy Analysis 37

2.1 Sustainability and Efficiency 372.1.1 Sustainable Development 372.1.2 Sustainability Methods and Metrics 392.1.3 Thermodynamic Approach to Sustainability and Efficiency 40

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2.2 Thermodynamic Analysis of Processes 422.2.1 Introduction 422.2.2 Mass and Energy Rate Balances for a Steady Flow Process – the First Law

of Thermodynamics 422.2.3 Quality of Energy and Materials 432.2.4 Entropy and the Second Law of Thermodynamics 452.2.5 Entropy Production 472.2.6 Entropy Rate Balance for a Steady Flow Process 502.2.7 Maximum Work Obtainable from a Steady Flow Process 51

2.3 Exergy Concept 522.3.1 Defining Exergy 522.3.2 Exergy Reference Environment 542.3.3 Exergy versus Energy 552.3.4 Exergy of Work and Heat Transfer 562.3.5 Exergy of a Stream of Matter 592.3.6 Physical Exergy 602.3.7 Chemical Exergy 62

2.4 Exergetic Evaluation of Processes and Technologies 672.4.1 Exergy Rate Balance for a Steady Flow Process 672.4.2 Internal and External Exergy Losses 682.4.3 Exergetic Efficiency 692.4.4 Cumulative Exergy Consumption 742.4.5 Improvement of Exergetic Performance 762.4.6 Economic and Ecological Aspects of Exergy 78

2.5 Renewability of Biofuels 812.5.1 Introduction 812.5.2 Application of Cumulative Exergy Consumption for Biofuels Production 812.5.3 Renewability Indicators 84

2.6 Closing Remarks 86References 86

PART II | Biomass Production and Conversion

Chapter 3 | Photosynthesis

3.1 Photosynthesis: An Overview 933.1.1 Introduction 933.1.2 Basic Concepts of Photosynthesis 943.1.3 Light Reactions for the Photochemical Oxidation of Water 953.1.4 Dark Reactions for the Synthesis of Sugars 963.1.5 Historical Discovery 973.1.6 Efficiency of Photosynthesis 98

3.2 Exergy of Thermal Radiation 993.2.1 Introduction 993.2.2 Radiation of Determined Surface (the Leaf) 1003.2.3 Energy of Solar Radiation 1013.2.4 Entropy of Solar Radiation 1033.2.5 Exergy of Solar Radiation 1043.2.6 Maximum Theoretical Exergetic Efficiency of Photosynthesis 105

3.3 Exergy Analysis of Photosynthesis 1063.3.1 Model and Mass Balance of Photosynthesis for a Leaf Surface 1063.3.2 Energy Balance of Photosynthesis 1093.3.3 Exergy Balance of Photosynthesis 1123.3.4 Relative Exergy Losses in Subprocesses of Photosynthesis 1133.3.5 Other Exergy Studies on Photosynthesis 116

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3.4 Global Photosynthesis 1163.4.1 Distribution of Exergy Flows above the Earth’s Surface 1163.4.2 Global Biomass Production 119

3.5 Closing Remarks 120References 120

Chapter 4 | Biomass Production 123

4.1 Overview 1234.1.1 Introduction 1234.1.2 Natural Factors 1244.1.3 Biomass Yield 1264.1.4 Fossil Inputs for Biomass Cultivation and Harvesting 1274.1.5 Biomass Logistics 1304.1.6 Environmental Impacts of Biomass Cultivation 1314.1.7 Economics of Biomass Production 132

4.2 Efficiency of Solar Energy Capture 1334.2.1 Major Terrestrial Biomass Crops 1334.2.2 Aquatic Biomass 137

4.3 Fossil Inputs for Biomass Cultivation and Harvesting 1404.3.1 Major Terrestrial Biomass Crops 1404.3.2 Tropical Tree Plantations 1434.3.3 Aquatic Biomass 145

4.4 Fossil Inputs for Biomass Logistics 1464.4.1 Major Terrestrial Biomass Crops 1464.4.2 Aquatic Biomass 148

4.5 Closing Remarks 150References 150

Chapter 5 | Thermochemical Conversion: Gasification 153

5.1 Gasification: An Overview 1535.1.1 Introduction 1535.1.2 Historical Development of Gasification 1545.1.3 Principle of Biomass Gasification 1545.1.4 Gasification Technology 1565.1.5 Biomass Gasification Models 1605.1.6 Gasification Products 1645.1.7 Application of Biomass Gasification 166

5.2 Gasification of Carbon 1715.2.1 Introduction 1715.2.2 Gasification of Solid Carbon with Air 1735.2.3 Gasification of Solid Carbon with Oxygen 1765.2.4 Gasification Using Steam/Oxygen Mixtures 179

5.3 Gasification of Biomass 1835.3.1 Introduction 1835.3.2 Exergetic Efficiency of Gasification with Air 1845.3.3 Exergetic Efficiency of Gasification with Steam and Steam/Air Mixtures 188

5.4 Gasification of Typical Fuels 1915.4.1 Comparison of Gasification Efficiency of Biomass and Coal 1915.4.2 Other Comparative Studies on Exergetic Efficiency 197

5.5 Closing Remarks 198References 198

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Chapter 6 | Gasification: Parametric Studies and Gasification Systems

6.1 Effect of Fuel Chemical Composition on Gasification Performance 2036.1.1 Biomass versus Coal Gasification 2036.1.2 Gasifier Fuel Properties 2046.1.3 Gasification Temperatures and Equivalence Ratio 2066.1.4 Gasification Efficiencies 2076.1.5 Exergy Losses 2096.1.6 Concluding Remarks 211

6.2 Effect of Biomass Moisture Content, Gasification Pressure, and Heat Addition onGasification Performance 2116.2.1 Introduction 2116.2.2 Effect of Biomass Moisture Content 2126.2.3 Effect of Gasification Pressure 2146.2.4 Effect of External Heat Addition 215

6.3 Improvement of Gasification Exergetic Efficiency 2156.3.1 Biomass Torrefaction 2166.3.2 Predrying of Biomass 2236.3.3 Preheating of Gasification Air 226

6.4 Gasification Efficiency Using Equilibrium versus Nonequilibrium Models 2306.4.1 Quasi-Equilibrium Thermodynamic Models 2316.4.2 Comparison of Gasification Efficiency 231

6.5 Performance of Typical Gasifiers 2336.5.1 Comparison of FICFB and Viking Gasifiers 2336.5.2 Fluidized-Bed Gasifiers for the Production of H2-Rich Syngas 2386.5.3 Downdraft Fixed-Bed Gasifier 2416.5.4 Updraft Fixed-Bed Gasifier 242

6.6 Plasma Gasification 2446.6.1 Plasma Gasification Technology 2446.6.2 Plasma Gasification of Sewage Sludge 244

6.7 Thermochemical Conversion in Sub- and Supercritical Water 2466.7.1 Conversion of Wet Biomass in Hot Compressed Water 2466.7.2 Supercritical Water Gasification (SCWG) 2476.7.3 Hydrothermal Upgrading (HTU) under Subcritical Water Conditions 251

6.8 Closing Remarks 253References 253

PART III | Biofuels

First-Generation Biofuels

Chapter 7 | Biodiesel

7.1 Biodiesel: An Overview 2617.1.1 Introduction 2617.1.2 Historical Development 2627.1.3 Chemistry 2637.1.4 Feedstocks 2657.1.5 Production Process 2667.1.6 Biodiesel as Transport Fuel 2687.1.7 Energy, Environmental, and Economic Performance 269

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7.2 Biodiesel from Plant Oils 2727.2.1 Exergy Analysis of Transesterification 2727.2.2 Exergy Analysis of Overall Production Chain 275

7.3 Biodiesel from Used Cooking Oil 2787.3.1 Exergy Analysis of Biodiesel Production 2787.3.2 Exergy Analysis of Overall Production Chain 281

7.4 Biodiesel from Microalgae 2817.4.1 Introduction 2817.4.2 Exergy Analysis of Transesterification of Algal Oil 2827.4.3 Exergy Analysis of Overall Production Chain of Algal Biodiesel 284

7.5 Closing Remarks 286References 286

Chapter 8 | Bioethanol 289

8.1 Bioethanol: An Overview 2898.1.1 Introduction 2898.1.2 Historical Development 2908.1.3 Ethanol as Transport Fuel 2918.1.4 Chemistry 2938.1.5 Bioethanol Production Methods 2958.1.6 Energy, Environmental and Economic Aspects 302

8.2 Exergy Analysis of Ethanol from Sugar Crops 3058.2.1 Introduction 3058.2.2 Ethanol from Sugarcane 3068.2.3 Exergetic Performance of Sugarcane Ethanol Plants for Various

Cogeneration Configurations 3108.2.4 Ethanol from Sugar Beets 3138.2.5 Renewability of Ethanol from Sugar Crops 315

8.3 Exergy Analysis of Ethanol from Starchy Crops 3178.3.1 Introduction 3178.3.2 Corn Ethanol: Exergy Analysis 3178.3.3 Corn Ethanol: Cumulative Exergy Consumption (CExC) and Renewability 3198.3.4 Wheat Ethanol 322

8.4 Exergy Analysis of Lignocellulosic Ethanol (Second Generation) 3238.4.1 Introduction 3238.4.2 Ethanol from Wood (NREL Process) 3248.4.3 Impact of Biomass Pretreatment and Process Configuration 3288.4.4 Comparison of Exergetic Efficiency 3308.4.5 Renewability of Lignocellulosic Ethanol from Tropical Tree Plantations 331

8.5 Alternative Ethanol Processes 3328.5.1 Fossil Ethanol from Mineral Oil 3328.5.2 Ethanol via Water Electrolysis 333

8.6 Closing Remarks 334References 334

Second-Generation Liquid Biofuels

Chapter 9 | Fischer–Tropsch Fuels 341

9.1 Fischer–Tropsch Synthesis: An Overview 3419.1.1 Introduction 3419.1.2 Historical Development 342

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9.1.3 Process Chemistry 3439.1.4 Comparison of F-T Fuels to Conventional Transport Fuels 3459.1.5 Process Design 3469.1.6 Process Performance 348

9.2 Exergy Analysis of Coal-to-Liquid (CTL) Process 3519.2.1 Description of CTL Process 3519.2.2 Mass Balance and Energy Analysis 3539.2.3 Exergy Analysis 354

9.3 Exergy Analysis of Gas-to-Liquid (GTL) Processes 3559.3.1 GTL Process with Tail Gas Recycling: Internal and External 3569.3.2 Impact of Reformer Temperature on GTL Efficiency: External Tail Gas Recycling 361

9.4 Exergy Analysis of Biomass-to-Liquid (BTL) Processes 3659.4.1 Introduction 3659.4.2 Once-Through F-T Process 3669.4.3 Impact of Biomass Feedstock on Process Efficiency 3739.4.4 Reforming and Recycling of F-T Reactor Tail Gas 3779.4.5 Recycling of F-T Reactor Tail Gas to Biomass Gasifier 382

9.5 Closing Remarks 383References 383

Chapter 10 | Methanol 387

10.1 Methanol: An Overview 38710.1.1 Introduction 38710.1.2 Historical Development 38810.1.3 Chemistry 38910.1.4 Methanol as Transport Fuel 39010.1.5 Process Design 39210.1.6 Process Performance 393

10.2 Methanol from Fossil Fuels 39610.2.1 Methanol from Natural Gas 39610.2.2 Methanol from Coal 400

10.3 Methanol from Biomass 40510.3.1 Methanol from Waste Biomass (Sewage Sludge) 40510.3.2 Other Biomass-Based Methanol Processes 413

10.4 Closing Remarks 414References 415

Chapter 11 | Thermochemical Ethanol 419

11.1 Thermochemical Ethanol: An Overview 41911.1.1 Introduction 41911.1.2 Process Chemistry 42011.1.3 Catalysts for Ethanol Synthesis 42211.1.4 Process Design 42311.1.5 Energy, Environmental and Economic Aspects 426

11.2 Exergy Analysis 42711.2.1 Process Description 42811.2.2 Mass and Energy Balances (Rh-Based Catalyst) 43111.2.3 Exergy Analysis (Rh-Based Catalyst) 43311.2.4 Impact of Ethanol Synthesis Catalyst (MoS2-Based Target Catalyst) 43511.2.5 Impact of Gasification Temperature 438

11.3 Closing Remarks 439References 440

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Second-Generation Gaseous Biofuels

Chapter 12 | Dimethyl Ether (DME) 445

12.1 Dimethyl Ether: An Overview 44512.1.1 Introduction 44512.1.2 Historical Development 44612.1.3 Process Chemistry 44712.1.4 DME as Energy Carrier 44812.1.5 Production Technology 44912.1.6 Energy, Environmental, and Economic Aspects 451

12.2 Dimethyl Ether from Fossil Fuels 45212.2.1 DME from Natural Gas 45212.2.2 DME from Coal 45812.2.3 DME from Co-Feed of Natural Gas and Coal 462

12.3 Dimethyl Ether from Biomass 46212.3.1 DME via Indirect Steam Gasification 46212.3.2 Influence of Syngas Preparation Method on Process Efficiency 468

12.4 Closing Remarks 472References 472

Chapter 13 | Hydrogen 475

13.1 Hydrogen: An Overview 47513.1.1 Introduction 47513.1.2 History: from Discovery to Hydrogen Economy 47613.1.3 Chemistry of Hydrogen Production 47713.1.4 Hydrogen Use 47913.1.5 Hydrogen Storage 48013.1.6 Production Methods 48113.1.7 Energy, Environmental, and Economic Performance 482

13.2 Exergy Analysis of Hydrogen from Fossil Fuels 48513.2.1 Hydrogen from Natural Gas 48513.2.2 Comparison of Efficiency for Hydrogen-from-Natural Gas Processes 48913.2.3 Hydrogen-from-Coal Gasification 49013.2.4 Comparison of Efficiency for Hydrogen-from-Coal Processes 493

13.3 Exergy Analysis of Hydrogen from Water Electrolysis 49413.3.1 Process Description 49413.3.2 Mass and Energy Balances 49513.3.3 Exergy Analysis 495

13.4 Exergy Analysis of Future Hydrogen Production Processes 49613.4.1 Thermochemical Cycles 49713.4.2 Geothermal Energy 49913.4.3 Solar Energy 500

13.5 Exergy Analysis of Hydrogen Production from Biomass Gasification 50113.5.1 Exergy Analysis of Hydrogen from Wood 50113.5.2 Influence of Biomass Feedstocks on Exergetic Efficiency 50613.5.3 Influence of Gasification System Configurations on Exergetic Efficiency 50713.5.4 Comparison of Efficiency for Hydrogen-from-Biomass Gasification 511

13.6 Exergy Analysis of Biological Hydrogen Production 51213.6.1 Process Description 51213.6.2 Mass and Energy Balances 514

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13.6.3 Exergy Analysis 51513.7 Closing Remarks 517References 517

Chapter 14 | Substitute Natural Gas (SNG) 523

14.1 Substitute Natural Gas: An Overview 52314.1.1 Introduction 52314.1.2 Historical Development 52414.1.3 Chemistry of Methanation 52614.1.4 Natural Gas as Energy Carrier 52714.1.5 SNG Production Technology 52914.1.6 Energy, Environmental and Economic Aspects 530

14.2 SNG from Coal 53314.2.1 Description of Coal-to-SNG Process 53314.2.2 Process Modeling 53714.2.3 Mass and Energy Balances 53714.2.4 Exergy Analysis 53814.2.5 Overview of Coal-to-SNG Processes 540

14.3 SNG from Biomass Gasification 54014.3.1 SNG via Wood Gasification 54014.3.2 Comparison of SNG Production from Various Biomass Feedstocks 55014.3.3 Overview of Biomass-to-SNG Processes 555

14.4 Closing Remarks 555References 556

PART IV | Bioenergy Systems

Chapter 15 | Thermal Power Plants, Heat Engines, and Heat Production 561

15.1 Biomass-Based Power and Heat Generation: An Overview 56115.1.1 Introduction 56115.1.2 Historical Development 56315.1.3 Technologies for Power Generation from Biomass 56415.1.4 Biofuels in Internal Combustion Engines and Gas Turbines 56715.1.5 Biomass Heating Systems 56815.1.6 Performance and Cost of Power Generation Systems 56915.1.7 Environmental Aspects 571

15.2 Biomass Combustion Power Systems 57115.2.1 Introduction 57115.2.2 Biomass Steam Cogeneration Plant 57215.2.3 Externally Fired Gas Turbine–Combined Cycle 57515.2.4 Biomass-Fired Organic Rankine Cycle (ORC) 580

15.3 Biomass Gasification Power Systems 58415.3.1 Introduction 58415.3.2 Biomass Integrated Gasification Gas Turbine–Combined Cycle (BIG/GT-CC) 58515.3.3 Improving Efficiency BIG/GT-CC Plants 58815.3.4 Biomass Integrated Gasification Internal Combustion Engine–Combined Cycle

(BIG/ICE-CC) 58915.4 Comparison of Various Biomass-Fueled Power Plants 591

15.4.1 Internally and Externally Fired Gas Turbine Simple Cogeneration Cycles 592

CONTENTS xiii

15.4.2 Internally and Externally Fired Gas Turbine: Simple and Combined Cycles 59715.4.3 Comparison of Biomass Combustion and Gasification CHP Plants 602

15.5 Biomass-Fueled Internal Combustion Engines and Gas Turbines 60815.5.1 Ethanol-Fueled Spark-Ignition Engines 60915.5.2 Biodiesel-Fueled Compression-Ignition Engines 61015.5.3 Biofuel-Fired Gas Turbines 612

15.6 Polygeneration of Electricity, Heat, and Chemicals 61515.6.1 Introduction 61515.6.2 Methanol Synthesis 61515.6.3 Ethanol Production 621

15.7 Biomass Boilers and Heating Systems 62415.7.1 Introduction 62415.7.2 Biomass Boilers 62515.7.3 Energy Utilization in Buildings 627

15.8 Closing Remarks 628References 628

Chapter 16 | Biomass-Based Fuel Cell Systems 633

16.1 Biomass-Based Fuel Cell Systems: An Overview 63316.1.1 Introduction 63316.1.2 Historical Development 63416.1.3 Fuel Cell Fundamentals 63516.1.4 Fuel Cell Types 63616.1.5 Fuel Cell Thermodynamics 63816.1.6 Overview of Biomass-Based Fuel Cell Configurations 64016.1.7 Energy Efficiency, Cost, and Environmental Impact 642

16.2 Biomass Integrated Gasification–Solid Oxide Fuel Cell (BIG/SOFC) Systems 64216.2.1 Central Power Production Using BIG/SOFC/GT Systems 64316.2.2 Other Central Power Production Studies Using BIG/SOFC Systems 64716.2.3 Distributed Power Production Using BIG/SOFC Systems 64816.2.4 Integration of Supercritical Water Gasification (SCWG) with SOFC/GT

Hybrid System 65016.3 Biomass Integrated Gasification–Proton Exchange Membrane Fuel Cell (BIG/PEMFC)

Systems 65216.3.1 Distributed Combined Heat and Power Generation Based on Central Hydrogen

Production 65216.3.2 Effect of Hydrogen Quality on Efficiency of Distributed CHP Systems 659

16.4 Fuel Cell Systems Fed with Liquid Biofuels 66016.4.1 Introduction 66016.4.2 Maximum Electricity Obtainable from Various Fuels 66116.4.3 Integrated Fuel Processor–Fuel Cell (FP-FC) System 66316.4.4 Direct Liquid Fuel Cell Systems 668

16.5 Closing Remarks 669References 669

Chapter 17 | Biorefineries 673

17.1 Biorefineries: An Overview 67317.1.1 Introduction 67317.1.2 Historical Development 67417.1.3 Chemical Value of Biomass 675

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17.1.4 Biorefinery Systems 67717.1.5 Biorefinery Technology 679

17.2 Comparison of Various Biomass Utilization Routes 68117.2.1 Biomass Utilization Routes 68117.2.2 Power Generation 68217.2.3 Biofuels Production 68317.2.4 Chemical Biorefinery 683

17.3 Exergy Inputs to Basic Biorefinery Steps 68417.3.1 Biorefinery Model 68417.3.2 Processing Simple Carbohydrates into Fermentable Sugars 68617.3.3 Processing Complex Carbohydrates into Fermentable Sugars 68617.3.4 Processing Fermentable Sugars into Ethanol 68817.3.5 Processing Ethanol into Ethylene 68917.3.6 Fatty Acids Processing 69017.3.7 Amino Acids Processing 69217.3.8 Lignin Processing 69517.3.9 Ash and Residuals Processing 695

17.4 Optimal Biomass Crops as Biorefinery Feedstock 69617.4.1 Biomass versus Petrochemical Route for the Production of Bulk Chemicals 69617.4.2 Cumulative Fossil Fuel Consumption in the Biomass Route 69717.4.3 Cumulative Fossil Fuel Consumption in the Petrochemical Route 69817.4.4 Fossil Fuel Savings 69917.4.5 Optimal Crops for Biorefineries 699

17.5 Closing Remarks 702References 702

Postface 707

Appendixes

Appendix A – Conversion Factors 709

Appendix B – Constants 711

Appendix C – SI Prefixes 713

Glossary of Selected Terms 715

Notation 721

Acknowledgments for Permission to Reproduce Copyrighted Material 729

Author Index 733

Subject Index 745

Preface

Today, fossil fuels (coal, petroleum, and natural gas) are the major primaryenergy sources. Serious global problems related to the use of fossil resources are afast depletion, environmental damage, and global warming. It is widely acknowl­edged that the existing fossil fuels should be replaced in future by renewableenergy such as biomass, solar, wind, and geothermal. At present biomass is thefourth largest energy resource in the world, after oil, gas and coal. Biomass can beconverted into all major energy carriers such as electricity, heat, and transportfuels as well as a wide diversity of chemicals and materials that are at presentproduced from fossil fuels. The key features of biomass are renewability andneutral CO2 impact.

On the other hand, the use of biomass is accompanied by several drawbacks,mainly limitations of land and water and competition with food production.Production of biomass involves high logistics costs due to its low energy density.Moreover, biomass suffers from very low conversion efficiency of sunlight intochemical energy in photosynthesis. For biomass-based systems, a key challenge isthus to develop efficient conversion technologies that can compete economicallywith fossil fuels and other forms of renewable energy.

It is obvious that accurate metrics are required to evaluate the performance ofbiomass energy systems. In practice, various performance indicators are used,usually grounded in thermodynamics, economics, or environmental issues. Thecommonly applied energy-based indicators are less suited for the evaluation ofbiomass energy as they involve only the quantity of energy, not its quality. They arebased on the first law of thermodynamics that considers all energy forms such asheat, electricity and chemical as equal. This leads often to the incorrect evaluation ofenergy systems, for example, energy efficiency of a biomass boiler is high, whilecombustion of the fuel results in destruction of the high-value chemical energy ofbiomass into the low-value heat.

Thermodynamic process indicators based on the exergy concept (the first andsecond laws of thermodynamics) are nowadays commonly accepted as the mostnatural way to measure the performance of various processes, ranging fromenergy technology, chemical engineering, transportation, agriculture, and so on.The exergy (available energy) takes into account not only the quantity but alsothe quality of materials and energy flows involved in the energy systems. In allreal processes, exergy (the quality of energy) is consumed due to entropyproduction, while energy is indestructible and remains constant. This is whyexergy analysis is usually employed to identify inefficiencies and improveprocess performance.

The book provides a systematic and comprehensive overview of the effi­ciency of biomass energy systems using the uniform thermodynamic approachbased on the exergy concept. The efficiency of all major steps involved in biomassproduction and conversion to power, biofuels, and chemicals is discussed.The following topics are covered: photosynthesis, biomass cultivation, gasifica­tion, first-generation biofuels (biodiesel, ethanol), second-generation biofuels(Fischer–Tropsch fuels, methanol, thermochemical ethanol, dimethyl ether(DME), hydrogen, and substitute natural gas (SNG)), power generation involving

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xvi PREFACE

biomass combustion, gasification, and fuel cells, and production of chemicals inbiorefineries.

This text is the first to discuss the efficiency of all main aspects of biomassenergy using the exergy approach. The major features of the book are as follows:

• All bioenergy processes are covered in separate chapters that are organizedin a logical order, starting from photosynthesis and cultivation of biomassfeedstocks and ending with final bioenergy products.

• Each chapter begins with a brief introduction including a historical devel­opment, chemistry, and major technologies, as well as energy, environ­mental, and economic aspects. This way the book can also serve as anintroduction to biomass and bioenergy for students and professionals.

• Case studies and illustrative examples are presented for most topics that willhelp readers understand the practical applications of bioenergy.

• The exergetic efficiencies are compared with the corresponding energyefficiencies and the similarities and differences between these twoapproaches are explained.

• The exergetic efficiencies of fuels production and power generation from thebiomass are compared with efficiencies of the corresponding traditionalfossil fuels-based technologies, which are also extensively covered.

The book is divided into four parts.Part I: Background and Outline (Chapters 1 and 2) presents a general intro­

duction to the main subjects of the book: biomass energy and exergy analyses.Chapter 1 provides an overview of bioenergy in relation to global energy andenvironmental issues, including biomass resources, main conversion processes, andutilization of biomass. Chapter 2 introduces the reader to the exergy concept andanalysis via a refreshment of thermodynamics. Similarities and differences betweenenergy and exergy approaches are also explained. Part I forms the basis for exergyanalyses of biomass conversion processes and technologies involved in bioenergychains which are presented in the remaining three parts.

Part II: Biomass Production and Conversion (Chapters 3 through 6) presentsexergy analyses of the initial steps of bioenergy chains, particularly photosynthesis,biomass production, and the thermochemical conversion—gasification. Chapters 5and 6 are devoted to the analysis of biomass gasification, discussing variousbiomass feedstocks and their properties, effect of operating conditions, improve­ment of gasification performance, and typical and special gasifiers.

Part III: Biofuels (Chapters 7 through 14) deals with exergy analyses of biofuelsproduction, including first-generation liquid (biodiesel and bioethanol), second-generation liquid (Fischer–Tropsch fuels, methanol, and thermochemical ethanol),and gaseous biofuels (dimethyl ether, hydrogen, and substitute natural gas).

Part IV: Bioenergy Systems (Chapters 15 through 17) covers exergy analyses ofintegrated biomass energy systems, namely, heat and power plants, fuel cells, andbiorefineries.

The book is intended for a wide audience in the field of energy, particularlyrenewable energy, biomass, and bioenergy. The content of this book is multi­disciplinary and it can be useful for advanced undergraduate and graduatestudents as well as researchers in Energy, Mechanical Engineering, ChemicalEngineering, Environmental Engineering, and Agricultural Engineering. Thebook can be adopted as a textbook for college courses, which deal with renewableenergy, environmental engineering, and sustainability.

PREFACE xvii

The book is also suitable for energy, fuel and automobile, and agriculturalprofessionals who wish to acquire knowledge in the area of specific bioenergysystems. It is also addressed to government employees, particularly energetic,environmental, agricultural, and economic policy makers, interested in under­standing and evaluation of efficiency of bioenergy systems.

KRZYSZTOF J. PTASINSKI

Acknowledgments

First and foremost I am very much indebted to Professor Jan Szargut of the SilesianUniversity of Technology, Gliwice, Poland, who with his pioneering work con­tributed much to the exergy analysis, for introducing me to the subject, andinspiration in my research. My special thanks also go to Professors Andrzej Zie ̨bik,Andrzej Białecki, and Wojciech Stanek of the Silesian University of Technology,Gliwice, for their friendship and many inspiring discussions over the years thatstimulated me in writing this book.

I wish to express my appreciation to my former coworkers and students fromthe Eindhoven University of Technology, The Netherlands, who have contributedto my research. Special thanks go to Dr. Mark Prins for his work on exergy analysisof biomass gasification, Dr. Martin Juras ̌ ̌cik for his contribution to exergy analysis ofbiomass-to-SNG, and the late Professor Frans Janssen for valuable discussions. Thecontributions of several past Ph.D. students, namely, Lopamudra Devi, Sreejit Nair,Michiel van der Stelt, Ana Sues, and Erik Delsman, and M.Sc. students, namely,Carlo Hamelinck, Harro van der Heijden, Simon van der Heijden, Tamara Loonen,Fernanda Neira d’Angelo, Anke Pierik, Charles Uju, Caecilia Vitasari, and JohanVenter are acknowledged.

I would like to take this opportunity to express my gratitude to all authorswhose work helped me to prepare this book. In particular, my special thanks go toProfessor Richard Petela of Technology Scientific, Canada, Professor Johan Sandersof the Wageningen University, The Netherlands, Dr Benjamin Brehmer of EvonikIndustries, Germany, Dr. Richard Toonssen and Dr. Nico Woudstra of the DelftUniversity of Technology, The Netherlands, and Ryan E. Katofsky, M.Sc., of thePrinceton University.

Finally, I convey my thanks and gratitude to my wife Danka who has partici­pated in every stage of this book’s development, for her motivation, support, andpatience.

xix

About the Author

Krzysztof J. Ptasinski earned his M.Sc. degree in 1969 and a Ph.D. in chemicalengineering from the Warsaw University of Technology, Poland, in 1978. He hasbeen on the faculties of the Warsaw University of Technology and the University ofTwente, The Netherlands, and most recently of the Eindhoven University ofTechnology, The Netherlands. After his recent retirement, he has been appointedas visiting professor at the Silesian University of Technology Gliwice, Poland, in thegroup of Professor Szargut.

He has over 40 years of experience in academic teaching and research inchemical engineering and energy technology, particularly biomass conversion,exergy analysis, reaction engineering, and separations. His pioneering researchon application of exergy analysis to biomass and bioenergy is internationallyacclaimed. For his work in this area, in 2009 he received his D.Sc degree inenergy engineering from the Silesian University of Technology, Gliwice. Inaddition to this book, Dr. Ptasinski is the author or co-author of more than 200publications, including 19 book chapters and 75 research papers. Currently, heserves as a Subject Editor for biomass and bioenergy of Energy, the InternationalJournal.

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P A R T I

Background and Outline

C H A P T E R 1

Bioenergy Systems:An Overview

The use of fossil fuels that are currently our major energy sources leads to undesiredeffects such as global warming, environmental pollution, and health damage.Moreover, an increased consumption of fossil energy results in a fast depletion.Therefore, it is desired that renewable energy sources, such as biomass, solar, andgeothermal, should replace fossil fuels. Biomass was the first fuel used by peoplethat had dominated the global energy supply until the nineteenth century and isstill used mainly in rural areas of developing countries for cooking and heating.However, biomass can be converted into all major energy carriers such as elec­tricity, heat, and transport fuels as well as a wide diversity of chemicals andmaterials that are presently produced from fossil fuels. Biomass as a sustainableenergy source can significantly contribute to the future world energy supply. Thischapter presents a brief introduction to biomass and bioenergy systems. We startthis chapter with a discussion of current energy and environmental problems inSection 1.1. Section 1.2 is an introduction to bioenergy systems, including historicaldevelopment, biomass resources, and their characteristics as well as environmentalimpact and economics. Biomass conversion processes, including pretreatment,thermochemical, biochemical, and chemical conversion, are reviewed in Section1.3. Finally, Section 1.4 is devoted to the utilization of biomass for transport fuels,power generation, heating, and chemicals.

1.1 ENERGY AND THE ENVIRONMENT

1.1.1 Global Energy Consumption

Energy is commonly considered as one of the most essential elements in thedevelopment of human civilization. We need energy for almost all activities,such as food, clothing, shelter, materials, transportation, and communication.The demand for energy has continuously increased since the beginning of humancivilization. In the hunter–gatherer society, man used food as the main energysource. After the fire discovery, energy was also used for heat and light as well ascooking and roasting. About 10,000 years ago, the agricultural technology started

Efficiency of Biomass Energy: An Exergy Approach to Biofuels, Power, and Biorefineries, First Edition.Krzysztof J. Ptasinski. 2016 John Wiley & Sons, Inc. Published 2016 by John Wiley & Sons, Inc.

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4 CHAPTER 1 BIOENERGY SYSTEMS: AN OVERVIEW

FIGURE 1.1World population and primaryenergy consumption, 1890–2010(sources: Klass, 1998; UN, 1999;IEA, 2013).

that increased energy demand for field irrigation, soil cultivation and cropsproduction, and nonagricultural purposes, such as tools made from wood andiron. Since the industrial revolution in the nineteenth century, large amounts ofenergy have been required for new applications, such as steam and internalcombustion engines and various electrical equipment.

Figure 1.1 illustrates the change of world population and primary energyconsumption from 1890 to 2010. In this period, the world population has increasedby a factor of more than 4, from 1.6 to 6.8 billion people. On the other hand, theglobal primary energy consumption has increased by a factor of more than 17, from31 to 539 EJ/year. Between 1890 and 2010, the per capita consumption of primaryenergy (expressed as power expenditure) has quadrupled from 0.61 to 2.52 kW/capita. This amount significantly exceeds the energy of the Western food consump­tion of about 0.2 kW/capita, which is sufficient for the human existence.

However, the regional distribution of energy use is very diverse. Table 1.1summarizes the 2010 population, total primary energy consumption, and primaryenergy consumption per capita (expressed as power expenditure) of several countriesselected from all continents, including developed and less developed countries. Theworld’s highest energy consumption per capita relates to the developed countries inNorth America, such as Canada (12.9) and the United States (10.6), Europe, such asFrance (5.7), Germany (5.7), and the United Kingdom (4.8), and Asia, such as Japan(5.7 kW/cap). On the other hand, major parts of the world population consume muchless energy per capita, particularly in the developing countries such as India (0.63),Bangladesh (0.21), and in Africa, such as Ethiopia (0.053 kW/cap).

The highest energy consumers are China and the United States that use 19.8 and19.3% of the world’s primary energy, respectively. To the world’s 10 highest primaryenergy consumers also belong Russia (5.7), India (4.3), Japan (4.3), Germany (2.7),Canada (2.5), Brazil (2.2), France (2.2), and the United Kingdom (1.7%). The top10 countries consume more than one-third of the world’s total primary energy.

Table 1.1 also presents the energy intensity of economic output that is expressedas a ratio between the primary energy use and the gross domestic product (GDP) (inUS$2005). Generally, more developed countries show lower energy intensity of theireconomy that is mainly due to the higher efficiency of energy conversion. Somecountries, such as Russia, China, and less developed countries consume moreprimary energy per GDP, which is largely due to a less efficient economic system.However, differences in the energy intensity are also caused by other factors, suchas country size, climate, composition of primary energy supply, and differences inan industrial structure (Smil, 2000).

1.1 ENERGY AND THE ENVIRONMENT 5

TABLE 1.1 Energy Characteristics for Several Countries, 2010

Primary Energy Primary Energy Carbon DioxidePopulation Consumption Consumption Per Capita Energy Intensity Emissions

Country (million) (EJ/year) (kW/cap)a (MJ/US$2005) (Mton/year)

The United States 309.3 103.4 10.6 7.92 5,637Canada 33.8 13.7 12.9 11.4 547Mexico 112.5 7.69 2.17 8.33 432Germany 81.6 14.7 5.68 5.01 793France 64.9 11.6 5.71 5.28 389The United 62.3 9.41 4.78 4.04 529

KingdomRussia 142.5 30.9 6.88 34.2 1,642Brazil 195.8 11.9 1.93 10.9 451Argentina 41.3 3.53 2.71 13.9 174China 1,330.1 106.4 2.54 27.7 7,997India 1,173.1 23.1 0.625 18.5 1,601Japan 127.6 23.0 5.71 5.01 1,180Bangladesh 156.1 1.04 0.212 13.4 57.0Saudi Arabia 25.7 8.28 10.2 23.0 469South Africa 49.1 5.90 3.81 20.5 473Egypt 80.5 3.49 1.38 27.8 191Ethiopia 86.0 0.144 0.053 7.16 6.45World 6,863.2 538.7 2.49 10.5 31,502

Source: EIA (2013a).aExpressed by power expenditure.

It is expected that energy consumption will significantly increase in the future.This is mostly due to two effects, namely, the expected population growth in thefuture and the increase of energy use per capita in less developed countries.According to the Shell energy scenarios, the global primary energy consumptionin 2050 can range between 770 and 880 EJ/year, depending on the future pattern ofenergy consumption (Shell, 2008). The United Nations Development Programforesees in 2050 the primary energy consumption in the range of 600–1040 EJ/year and in 2100 in the range of 880–1860, depending on the population andeconomic growth (UNDP, 2000).

Historical energy use shows a very large change not only in the amount ofconsumed energy, as described above, but also in the pattern of energy sources.Human civilization has used biomass (mainly wood fuel) as a primary energysource for a long time until the beginning of the industrial revolution. The fossilfuels era began at the end of the nineteenth century when coal started to replacewood as the primary fuel. Later, other fossil fuels, such as oil and natural gas, wereavailable in large amounts and low cost. Figure 1.2 illustrates the historical primaryenergy consumption pattern for the United States for the years 1850, 1930, and 2010.In 1850, wood was the dominant fuel contributing more than 90% to the primaryenergy consumption in the United States. Eighty years later in 1930, biomass wasreplaced by coal as the main fuel that contributed 58% to the primary energyconsumption. The same year the remaining fossil fuels were oil (25%) and naturalgas (8%), whereas the share of biomass was reduced to 6% only. Eighty years later,in 2010, fossil fuels contributed 83% to the primary energy consumption, whereasthe remaining primary energy was supplied as nuclear electric (8.6%), biomass(4.4%), and other renewables (3.9%). Figure 1.2 also illustrates that over the period

6 CHAPTER 1 BIOENERGY SYSTEMS: AN OVERVIEW

FIGURE 1.2 Historical primary energy consumption patterns (%) for the United States(source: EIA, 2011).

1850–2010, the primary energy consumption in the United States has dramaticallyincreased from 2.5 to 103.1 EJ/year, which is due to the availability of fossil fuels.Over the same period, the primary energy consumption per person has increasedfrom 3.4 to 10.6 kW/capita.

Figure 1.3 illustrates the share of various energy sources in the global primaryenergy consumption for the years 1973 and 2011. For both years, the global energypattern was dominated by fossil fuels that contributed 86.6 and 81.8%, respectively, tothe global primary energy consumption. In 1973, oil (46%) was the main fossil fuel,whereas in 2011 its share was reduced to 32%. Over the period 1973–2011, the share ofcoal increased from 25 to 29% and that of natural gas from 16 to 21%. On the otherhand, the contribution of bioenergy remained almost constant, 10.6% in 1973 and10.0% in 2011. Other energy sources in 2011 were nuclear electric (5.1%) and variousrenewable energy forms (3.3%), such as hydro, geothermal, solar, and wind.

It should be noticed that currently biomass is the fourth fuel in the world that hasan average share of 10% in the global primary energy consumption. However, thedistribution of biomass consumption is very unequally spread between developedand developing countries. The major part of biomass (about 80% of the worldbiomass) is consumed in Africa, Asia, and Latin America where it is used mainlyfor cooking and heating. The largest share of biomass in total primary energyconsumption corresponds to Africa (47%), followed by Asia (25%) and Latin America(19%). In some of the least developed countries in these regions, biomass is thedominant fuel whose share is up to 80% of a country primary energy consumption(FAO, 2010).

On the other hand, in the developed countries, biomass is mainly consumed forproduction of power, fuels, and chemicals, which is the main subject of this book.

FIGURE 1.3Share of energy sources in theglobal primary energy supply(source: IEA, 2013).