Transformationof Biomass Theory to Practice

EditorAndreas Hornung

Transformation of Biomass

Transformation ofBiomass

Theory to Practice

Editor

ANDREAS HORNUNG

Fraunhofer UMSICHT – Institute BranchSulzbach-Rosenberg, Germany

and

Chair in BioenergySchool of Chemical Engineering

College of Engineering and Physical SciencesUniversity of Birmingham, UK

This edition first published 2014© 2014 John Wiley & Sons, Ltd

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Library of Congress Cataloging-in-Publication Data

Transformation of biomass : theory to practice / editor, Andreas Hornung.pages cm

Includes bibliographical references and index.ISBN 978-1-119-97327-0 (hardback)

1. Biomass chemicals. 2. Biomass. I. Hornung, Andreas.TP248.B55T73 2014662′.88–dc23

2014004300

A catalogue record for this book is available from the British Library.

ISBN: 9781119973270

Set in 10/12pt Times by Aptara Inc., New Delhi, India.

1 2014

Contents

About the Editor xiiiList of Contributors xvPreface xvii

1 Biomass, Conversion Routes and Products – An Overview 1K.K. Pant and Pravakar Mohanty

1.1 Introduction 11.2 Features of the Different Generations of Biomass 21.3 Analysis of Biomass 5

1.3.1 Proximate and Ultimate Analysis of Biomass 61.3.2 Inorganic Minerals’ Ash Content and Properties 8

1.4 Biomass Conversion Routes 91.4.1 Pyrolysis 9

1.5 Bio-Oil Characteristics and Biochar 151.6 Scope of Pyrolysis Process Control and Yield Ranges 16

1.6.1 Moisture Content 181.6.2 Feed Particle Size 181.6.3 Effect of Temperature on Product Distribution 181.6.4 Solid Residence Time 181.6.5 Gas Environment 181.6.6 Effect of Pressure on Product Distribution 19

1.7 Catalytic Bio-Oil Upgradation 191.8 Bio-Oil Reforming 221.9 Sub and Supercritical Water Hydrolysis and Gasification 23

1.9.1 Biochemical Conversion Routes 241.9.2 Microorganisms for Fermentation 251.9.3 Integrating the Bioprocess 25

Questions 25References 28

2 Anaerobic Digestion 31Lynsey Melville, Andreas Weger, Sonja Wiesgickl and Matthias Franke

2.1 Introduction 312.1.1 Microbiology of Anaerobic Digestion 312.1.2 Key Phases 322.1.3 Influence Factors on the AD 34

vi Contents

2.1.4 Sources of Biomass Utilised in AD 362.1.5 Characteristics of Biomass 392.1.6 Pre-Treatment of Biomass 412.1.7 Products of Anaerobic Digestion 452.1.8 Anaerobic Treatment Technology 48

Questions 54References 54

3 Reactor Design and Its Impact on Performance and Products 61Yassir T. Makkawi

3.1 Introduction 613.2 Thermochemical Conversion Reactors 62

3.2.1 Types of Reactors 623.3 Design Considerations 63

3.3.1 Hydrodynamics 643.3.2 Residence Time 693.3.3 Distributor Plate and Cyclone 723.3.4 Heat Transfer Mechanisms 733.3.5 Biomass Conversion Efficiency 75

3.4 Reactions and their Impact on the Products 763.4.1 Devolatization and Pyrolysis 763.4.2 Gasification 77

3.5 Mass and Energy Balance 793.5.1 Mass Balance 793.5.2 Energy Balance 80

3.6 Reactor Sizing and Configuration 823.7 Reactor Performance and Products 85

3.7.1 Moving Beds 853.7.2 Fluidized Bed (FB) 87

3.8 New Reactor Design and Performance 92Nomenclature 94Greek Symbols 95Questions 95References 95

4 Pyrolysis 99Andreas Hornung

4.1 Introduction 1004.2 How Pyrolysis Reactors Differ 1014.3 Fast Pyrolysis 1024.4 Fast Pyrolysis Reactors 102

4.4.1 Bubbling Fluid Bed Reactor 1024.4.2 Circulating Fluid Bed Reactor 1024.4.3 Ablative Pyrolysis Reactor 1024.4.4 Twin Screw Reactor – Mechanical Fluidised Bed 1034.4.5 Rotating Cone 103

Contents vii

4.5 Intermediate Pyrolysis 1034.5.1 Principles 1034.5.2 Process Technology 104

4.6 Slow Pyrolysis 1054.6.1 Principles 1064.6.2 Process Technology 106

4.7 Comparison of Different Pyrolysis Techniques 1064.8 Future Directions 1074.9 Pyrolysis in Application 107

4.9.1 Haloclean Pyrolysis and Gasification of Straw 1074.10 Pyrolysis of Low Grade Biomass Using the Pyroformer Technology 109Questions 110References 110Books and Reviews 112

5 Catalysis in Biomass Transformation 113James O. Titiloye

5.1 Introduction 1135.2 Biomass, Biofuels and Catalysis 1145.3 Biomass Transformation Examples 1165.4 Hydrogen Production 1205.5 Catalytic Barriers and Challenges in Transformation 120Questions 120References 120

Appendix 5.A Catalytic Reforming of Brewers Spent Grain 125Asad Mahmood and Andreas Hornung

5.A.1 Biomass Characterisation 1255.A.2 Permanent Gas Analysis 1275.A.3 Pyrolysis and Catalytic Reforming without Steam 1275.A.4 Pyrolysis and Catalytic Reforming with Steam 130Reference 131

6 Thermochemical Conversion of Biomass 133S. Dasappa

6.1 Introduction 1336.2 The Thermochemical Conversion Process 136

6.2.1 Pyrolysis 1366.3 Combustion 1396.4 Gasification 140

6.4.1 Updraft or Counter-Current Gasifier 1416.4.2 Downdraft or Co-Current Gasifiers 142

6.5 Historical Perspective on Gasification Technology 1436.5.1 Pre-1980 1436.5.2 Post-1980 144

viii Contents

6.6 Gasification Technology 1456.6.1 Principles of Reactor Design 1456.6.2 Two Competing Designs 146

6.7 Open-Top Dual Air Entry Reaction Design – the IISc’s Invention 1496.8 Technology Package 151

6.8.1 Typical Performance of a Power Generation Package 1516.8.2 Engine and Generator Performance 155

Questions 156References 157

7 Engines for Combined Heat and Power 159Miloud Ouadi, Yang Yang and Andreas Hornung

7.1 Spark-Ignited Gas Engines and Syngas 1597.2 Dual-Fuel Engines and Biofuels 1607.3 Advanced Systems: Biowaste Derived Pyrolysis Oils for Diesel Engine

Application 1617.3.1 Important Parameters to Qualify the Oil as Fuel 162

7.4 Advanced CHP Application: Dual-Fuel Engine Application for CHPUsing Pyrolysis Oil and Pyrolysis Gas from Deinking-Sludge 1667.4.1 Fuel Properties: Deinking Sludge Pyrolysis Oil, Biodiesel,

Blends and Fossil Diesel 1677.4.2 Combustion Characteristics 1697.4.3 Conclusions 170

Questions 171References 171

8 Hydrothermal Liquefaction – Upgrading 175Ursel Hornung, Andrea Kruse and Gokcen Akgul

8.1 Introduction 1758.1.1 Product Properties 176

8.2 Chemistry of Hydrothermal Liquefaction 1778.3 Hydrothermal Liquefaction of Carbohydrates 1778.4 Hydrothermal Liquefaction of Lignin 1798.5 Technical Application 1828.6 Conclusion 183Questions 183References 183

9 Supercritical Conversion of Biomass 189Gokcen Akgul

9.1 Introduction 1899.2 Supercritical Water Gasification 1909.3 Supercritical Water Oxidation 1939.4 Water–Gas Shift Reaction under the Supercritical Conditions 193

Contents ix

9.5 Catalysts in the Supercritical Processes 1949.5.1 Alkali Salts in the Supercritical Water 195

9.6 The Solubilities of Gases in the Supercritical Water 1959.7 Fugacities of Gases in the Supercritical Water 1969.8 Mechanism of the Supercritical Water Gasification 1979.9 Corrosion in the Supercritical Water 1979.10 Advantages of the Supercritical Conversion of Biomass 1989.11 Conclusion 199Questions 199References 199

10 Influence of Feedstocks on Performance and Products of Processes 203Andreas Hornung

10.1 Humidity of Feedstocks 20610.2 Heteroatoms in Feedstocks 206References 207

11 Integrated Processes Including Intermediate Pyrolysis 209Andreas Hornung

11.1 Coupling of Anaerobic Digestion, Pyrolysis and Gasification 21011.2 Intermediate Pyrolysis, CHP in Combination with Combustion 21111.3 Integration of Intermediate Pyrolysis with Anaerobic

Digestion and CHP 21211.4 Pyrolysis Reforming 21211.5 The BIOBATTERY 21211.6 Pyrolysis BAF Application 21411.7 Birmingham 2026 21511.8 Conclusion 215References 216

12 Bio-Hydrogen from Biomass 217Andreas Hornung

12.1 World Hydrogen Production 21712.2 Bio-hydrogen 21712.3 Routes to Hydrogen 219

12.3.1 Steam Reforming 21912.3.2 Reforming 21912.3.3 Water Electrolysis 22312.3.4 Gasification 22312.3.5 Fermentation 223

12.4 Costs of Hydrogen 22312.5 Conclusion 224References 224Further Reading 225

x Contents

13 Analysis of Bio-Oils 227Dietrich Meier and Michael Windt

13.1 Definition 22713.2 Introduction 22713.3 General Aspects 228

13.3.1 Before Analysis 22813.3.2 Significance of Bio-Oil Analysis 22813.3.3 Post-Processing Reactions 22913.3.4 Overall Composition 229

13.4 Whole Oil Analyses 23013.4.1 Gas Chromatography 23013.4.2 NMR 23713.4.3 FTIR 23813.4.4 SEC 239

13.5 Fractionation Techniques 24113.5.1 Addition of Water 24113.5.2 Removal of Water (Lyophilization) 24313.5.3 Solid Phase Extraction (SPE) 24613.5.4 Solvent Partition 24913.5.5 Distillation 253

Questions 254References 254

14 Formal Kinetic Parameters – Problems and Solutions inDeriving Proper Values 257Neeranuch Phusunti and Andreas Hornung

14.1 Introduction 25714.2 Chemical Kinetics on Thermal Decomposition of Biomass 25914.3 Kinetic Evaluation Methods 26114.4 Experimental Kinetic Analysis Techniques 26414.5 Complex Reaction 26414.6 Variation in Kinetic Parameters 267

14.6.1 Kinetic Compensation Effect 26714.6.2 Thermal Lag 26814.6.3 Influence of Experimental Conditions 26914.6.4 Computational Methods 270

14.7 Case Study: Kinetic Analysis of Lignocellulosic Derived Materialsunder Isothermal Conditions 27114.7.1 Instrument and Operating Conditions 27114.7.2 Kinetic Evaluation Procedure 27214.7.3 Formal Kinetic Parameters and Some Technical Applications 275

14.8 Conclusion 278Nomenclature 279Subscripts 280Miscellaneous 280

Contents xi

Questions 280References 280

15 Numerical Simulation of the Thermal Degradation of Biomass –Approaches and Simplifications 285Istvan Marsi

15.1 Introduction 28515.2 Kinetic Schemes Applied in Complex Models 288

15.2.1 One-Step Global Models 28915.2.2 Competing Models 28915.2.3 Parallel Reaction Models 29015.2.4 The Broido–Shafizadeh Mechanism 29115.2.5 The Koufopanos Mechanism 29215.2.6 The Distributed Activation Energy Model (DAEM) 293

15.3 Thermal Aspects of Biomass Degradation Modeling 29415.3.1 Single-Particle Models 29515.3.2 Particles in Bed Models 298

15.4 Conclusion 299Questions 299Nomenclature 299Symbols 299Greek 300Indices 300References 300

16 Business Case Development 305Sudhakar Sagi

16.1 Introduction 30516.2 Biomass for Power Generation and CHP 30716.3 Business Perspective 308

16.3.1 Background 31016.4 The Role of Business Models 310

16.4.1 The Market Map Framework 31116.5 Financial Model Based on Intermediate Pyrolysis Technology 313

16.5.1 Pelletisation Process 31416.5.2 Pyrolysis Unit 315

References 318

17 Production of Biochar and Activated Carbon via IntermediatePyrolysis – Recent Studies for Non-Woody Biomass 321Andreas Hornung and Elisabeth Schroder

17.1 Biochar 32117.1.1 Introduction 32117.1.2 Biochar and its Application in the Field 322

References 325Further Reading 326

xii Contents

17.2 Activated Carbon 32717.2.1 Introduction 32717.2.2 Biomass Properties 32717.2.3 Activation of Biochar 32817.2.4 Formation of Granular Activated Carbon 334

References 337Further Reading 337

Index 339

About the Editor

Prof. Dr. rer. nat. Dipl.-Ing Andreas Hornung CEng FIChemE FRSC completed his studiesat the TU Darmstadt in Germany, where he graduated as an engineer in chemistry in 1991.He did his PhD at the TU Kaiserslautern in Germany whilst developing reactor systemsfor the pyrolysis-based recycling of plastics. He continued to work at the TU Karls-ruhe in Germany in developing reactor systems for the recycling of resins and electronicscrap, and expanded his topic to the conversion of biomass from 1996 onward. From2000 to 2002, Hornung worked for companies in Austria and Italy on the developmentof the first prototypes. Such units have been used since 2001 at the Karlsruhe Institute ofTechnology, where he worked until 2007 as head of the pyrolysis and gas treatment division.In 2007, he took over the chair in chemical engineering and applied chemistry at AstonUniversity in Birmingham, UK. In 2008, he founded the European Bioenergy ResearchInstitute EBRI which he led as director until the end of 2013. At the beginning of 2013 hebecame the director of the Institute Branch Sulzbach-Rosenberg of Fraunhofer UMSICHT.Since 2010 he has been a Fellow of the Royal Society of Chemistry (England), a Fellowof the Institution of Chemical Engineers as well as chartered engineer in Britain, and hebecame Green Leader of the West Midlands in 2012. In 2013, his technology received theBritish National Climate Week Award in the breakthrough category. He holds 18 patentsand has published more than 150 scientific publications to date. His institutes employed, in2013, about 120 staff members and are carrying out applied research in various sustainabletopics. In May 2014 he has been appointed as chair in bioenergy at the University ofBirmingham, UK.

xiv About the Editor

The main strategic topic of Hornung’s work today is the development of decentralisedpower providing units combined with pyrolysis, gasification and digestion units – calledthe Biobattery.

In a biogas scenario, a Biobattery installation seeks to use peaks in energy supplyto add to the energy output from a biogas installation and enable the thermochemicaltransformation of the more recalcitrant lignin-based components of digestion feedstocks.The use of digestate solids as feedstock for intermediate pyrolysis means that the amountof digestate for application to land is reduced to the liquid fraction. This is desirable wherethere is an oversupply of nitrogenous materials for application to land, such as in areasof intensive livestock production, since digestates can be a source of both greenhouse gasemissions and nitrogen losses to water bodies. Hence, the Biobattery not only adds to theflexibility of energy supply and storage, it also increases the energy and financial gainachieved from existing biogas infrastructure, while reducing their environmental impact.

The Biobattery concept aims to deliver local integrated system solutions, to capturepeaks in available power from solar and wind sources and convert and store this powerover periods of varying durations (minutes to days), thereby enabling the delivery of on-demand power compensation. The Biobattery concept uses a pool of renewable energytechnologies, that is high and low temperature thermal storage systems, thermochemicalbiomass processes, for example intermediate pyrolysis and gasification, thereby deliveringsolid, liquid and gaseous energy products which can be stored and used to produce eitherenergy on an on-demand basis, or sold as products for other use.

List of Contributors

Gokcen Akgul Department of Energy Systems Engineering, Recep Tayyip ErdoganUniversity, Turkey

S. Dasappa Indian Institute of Science, India

Matthias Franke Fraunhofer UMSICHT – Institute Branch Sulzbach-Rosenberg,Germany

Andreas Hornung Fraunhofer UMSICHT – Institute Branch Sulzbach-Rosenberg,Germany and Chair in Bioenergy, School of Chemical Engineering, College of Engineeringand Physical Sciences, University of Birmingham, UK

Ursel Hornung Karlsruhe Institut fur technologie – Institut fur Katalyseforschung und–Technologie, Germany

Andrea Kruse Universitat Hohenheim, Institut fur Agrartechnik, Konversionstechnolo-gie und Systembewertung nachwachsender Rohstoffe, Germany

Asad Mahmood European Bioenergy Research Institute (EBRI), Aston University, UK

Yassir T. Makkawi European Bioenergy Research Institute (EBRI), Aston University,UK

Istvan Marsi Faculty of Education, Department of Chemical Informatics, University ofSzeged, Hungary

Dietrich Meier Thunen-Institut fur Holzforschung, Germany

Lynsey Melville Centre for Low Carbon Research (CLCR), Birmingham City University,UK

Pravakar Mohanty Department of Chemical Engineering, Indian Institute of Technol-ogy Delhi, India

Miloud Ouadi European Bioenergy Research Institute (EBRI), Aston University, UK

xvi List of Contributors

K.K. Pant Department of Chemical Engineering, Indian Institute of Technology Delhi,India

Neeranuch Phusunti Department of Chemistry, Faculty of Science, Prince of SongklaUniversity, Hat Yai, Thailand

Sudhakar Sagi European Bioenergy Research Institute (EBRI), Aston University, UK

Elisabeth Schroder Karlsruher Institut fur Technologie – Institut fur Kern-und Energi-etechnik, Germany

James O. Titiloye Chemical & Environmental Engineering, College of Engineering,Swansea University, UK

Andreas Weger Fraunhofer UMSICHT – Institute Branch Sulzbach-Rosenberg,Germany

Sonja Wiesgickl Fraunhofer UMSICHT – Institute Branch Sulzbach-Rosenberg,Germany

Michael Windt Thunen Institut fur Holzforschung, Germany

Yang Yang European Bioenergy Research Institute (EBRI), Aston University, UK

Preface

Biomass is seen as a key feed material for the energy and material demands of mankindin the future. New businesses and technologies are therefore developing around biomassand its application. This textbook aims to help create an understanding of such processesrelated to the conversion of biomass into energy, heat and chemical products: processesbased on biological or thermal routes.

The education of new generations of engineers, scientists and technicians is importantto reach such goals. Therefore, this textbook intends to offer first guidelines to students aswell as people transferring from different sectors into the biomass conversion technologies.

The different chapters deal with fundamental details but also recent research and highlightthe possible problems and failures if methods are done wrong.

The textbook also carries two programmes for the evaluation of formal kinetic parametersas well as a calculation of business models.

Very often literature does not offer adequate answers to the questions arising fromresearch, for example how to describe the thermal conversion processes of biomass and theevaluation of data to characterise real reactor systems in terms of temperature and residencetime. The programmes related to this field will help the reader gain their own understanding.They can also be used to analyse data from lab work and therefore help to reach a bettergeneral understanding of the work done.

The business case model aims to enable the reader to compare different markets and theirspecific sensitivities, such as incentives and green subsidies, feed price and product priceimpact as well as general economic frame conditions.

Each chapter starts with a general motivation for the topic and at the end of each chapterthe reader will find some questions which should help in understanding the background ofthe chapter and in building up the mind of the reader to understand the material presentedin the right way.

No direct answers to the questions will be given by this textbook! The questions shouldsharpen the understanding and if the reader is unable to give an answer then the chaptershould be studied again!

The questions highlight the basics and interdependencies and will improve the ability ofthe reader to transfer skills within topics.

For a person in charge of new technologies or working at the front end of researchand development, such skills are of importance to give the right guidance or to find newpathways to better transform biomass.

The first chapter will give the reader a broad overview of biomass and its composition,conversion routes and products. The following chapters deal with specific technologies, suchas anaerobic digestion, pyrolysis and gasification, as well as hydrothermal and supercritical

xviii Preface

conversion. In addition, chapters for analysis and reactor design help to understand howprocesses are designed and how analysis helps to understand the sometimes complexcomposition of the products resulting from biomass. These chapters are very advanced andmight be best read at a later stage of the learning curve.

The same advice is given for the chapters on numerical simulation and formal kineticparameter evaluation. The related programme offers an up-to-date platform for calculations,but the reader will need an already profound understanding to apply them properly.

Finally no product will reach the market if it is not set properly in a business framework.The final chapter of this book gives you an insight into possible future products based

on the solid product from pyrolysis, such as char turned into activated carbon or biochar.The market for biochar particularly is developing all over the world.

I wish you a stimulating time while studying this book!

Best regardsProf. Dr. Andreas Hornung

Fraunhofer UMSICHTInstitute Branch Sulzbach-Rosenberg

Germanyand

Chair in BioenergySchool of Chemical Engineering

College of Engineering and Physical SciencesUniversity of Birmingham

UK

Online Supplementary MaterialPrograms for the evaluation of formal kinetic parameters, as well as the calculationof business models, can be found online. This software, and PowerPoint slides of allfigures from this book, can be found at http://booksupport.wiley.com.

1Biomass, Conversion Routes and

Products – An Overview

K.K. Pant and Pravakar MohantyDepartment of Chemical Engineering, Indian Institute of Technology Delhi, India

1.1 Introduction

The world consumes nearly two barrels of oil for every barrel produced. The depletionof conventional resources and stricter environmental regulations, along with increasingdemand for commercial fuels and chemicals, has led to the need to find the alternatives toconventional fuel and chemical sources. Renewable plant materials are considered as one ofthe most promising alternatives for the production of fuels and chemicals. The conventionalsources for fuels and chemicals are fossil fuels, crude oil natural gas, coal and so on, whichare dwindling rapidly. With the concept of green chemistry, there is every necessity toproduce alternative sources of energy and fuels from renewable biomass. Biomass refers toall organic matter generated through photosynthesis and many other biological processes.The ultimate source of energy this renewable biomass is inexhaustible solar energy, whichis captured by plants through photosynthesis. It includes both terrestrial as well as aquaticmatter, such as wood, herbaceous plants, algae, aquatic plants; residues such as straw,husks, corncobs, cow dung, sawdust, wood shavings, sawn wood, wood based panels, pulpfor paper, paper board, and other wastes like disposable garbage, night soil, sewage solids,industrial refuse and so on [1]. Biomass can provide approximately 25% of our current

Transformation of Biomass: Theory to Practice, First Edition. Edited by Andreas Hornung.© 2014 John Wiley & Sons, Ltd. Published 2014 by John Wiley & Sons, Ltd.Companion website: http://booksupport.wiley.com

2 Transformation of Biomass

Table 1.1 Forest resources, area (ha), year (2010).

Land area Forest area Forest area perName of country (million ha) (million ha) % 1000 people

Africa 2965 674 23 683South America 1756 864 49 2246North and Central America 2110 705 33 1315Asia 3094 593 19 145Europe 2214 1005 45 1373Oceania 849 191 23 5478Caribbean 23 7 30 166World 13010 4033 31 597

energy demand, if properly utilized. Taking into account the production of biomass withrespect to land and forest area, there are 4033 million ha of forests worldwide, as presentedin Table 1.1.

In India 55.2 million ha of waste land is available for a wide range of short period energycrop productions [2]. Tropical and subtropical forests comprise 55% of the world’s forests,while temperate and boreal forests account for rest 45% [3]. The average area of forest andwooded land per inhabitant varies regionally. Production and use of wood fuel, industrialround wood, sawn wood, wood-based panels, pulp for paper, paper board (m3) usage andits production are presented in Table 1.2. The total carbon stored in forest biomass isapproximately 331 Giga tonnes (GT). About 27% of biomass is used directly as carbonfeedstock, for example, sawn wood, wood based panels, pulp for paper, paper and paperboard, mainly in developing countries. However, 33% is used as an industrial raw materialand the remaining 40% is used as primary or secondary process residues, suitable only forenergy production, for example, for production of upgraded biofuels [2,3]. Approximately70–77% of the global wood harvest is either used or is potentially available as a renewableenergy source.

The most efficient utilization of these resources comes when they are converted to liquidand gaseous products by appropriate technologies. Non-commercial biomass (biofuels)is the main source of energy available in the rural areas. An estimation by the Foodand Agriculture Organization (FAO) shows that the global production of wood fuel andround wood reached 3410 million m3 during 2010 [2–4]. Just over half of this was woodfuel, where 90% of that is being produced and consumed in developing countries. On theother hand, industrial round wood production, totaling around 1542 million m3 in 2010, isproduced and consumed both by North and Central America and Europe.

1.2 Features of the Different Generations of Biomass

Broadly, biomass can be categorized as first, second, third, and fourth generation. Firstgeneration biomass refers to traditional plant biomass like sugar and starch crops. Secondgeneration biofuels include bioethanol and biodiesel produced from the residual, non-foodparts of crops, and from other forms of lignocellulosic biomass, such as wood, grasses, andmunicipal solid wastes [5]. Third and fourth generation biofuels include algae-derived fuels,

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4 Transformation of Biomass

such as biodiesel from microalgae oil, bioethanol from micro algae and seaweeds, the finechemicals and H2 from green microalgae, and microbes by sub- and supercritical extractionprocesses. Further these extracted microalgae can be utilized as biomass in thermochemicalor biochemical routes of conversion [6]. “Drop in” fuels like “green gasoline,” “greendiesel,” and “green aviation fuel” produced from biomass are also considered as fourthgeneration biofuels [7]. Efforts are also underway to genetically engineer organisms toopen the secrete of these fourth generation hydrocarbon fuels. In Figure 1.1, both food andnon-food biomass have been integrated in the sequential downward stream for establishment

Crop (food)

Grain (rice, wheat), sugar cane,Potatoes, Corn

Seaweeds, algae, hyacinth

Palm, jatropha

Short rotationwoody

Herbaceous

Dedicated

Grass

Wood

Oilseed plant

Aquatic plant

Starch sugar crop

Energy crop

Biomass

Non-food Biomass

Cellulosicresources

Manure (cattle/fresh)

Industrial waste

Municipal waste

Forest waste

Agricultural waste

Sawdust,pulp waste,

thinned wood

Straw (rice, barley,wheat), bagasses,

corn stover

Food waste, yardwaste, container andproduct packaging

Black liquor frompaper industry,

waste from foodindustry

Animal manure,plant manure,

compost

Figure 1.1 Biomass feedstock distribution in term of food and non-food basis for bio-refinery.

Biomass, Conversion Routes and Products – An Overview 5

Table 1.3 Generation-wise biomass distribution with its features.

1st generation 2nd generation 3rd generation 4th generation

Feedstock Sugar, starch crops,vegetable oil,soya bean,animal fat, straw

Wood, agriculturalwaste, municipalsolid waste,animal manure,landfills, pyrooils,pulp sludge, grass

Micro algae biomass Geneticallymodifiedcrop

Product Biodiesel, sugaralcohol, cornethanol

Hydro treating oil,bio-oil, FT-oil etc.

Algae oil Biofuel

Advantage Environmentallyfriendly,economical andsocially secure

Not competing withfood

Environmentallyfriendly advancedtechnology underprocess to reducethe cost ofconversion

Availability of highvalue protein andnutrients, residualalgae for jet fuelanimal feed

Easily capturesCO2 andconversionto a carbonneutral fuel

Disadvantage Limited feedstock,blended partlywith conventionalfuel

Acidic, viscous,high oxygenates

content inpyrooils

Slow growth of algae,extraction of algaeoil is difficult andcostly

—

of the biorefinery concept towards energy surplus. Generation-wise details of the biomassdiversifications are presented in Table 1.3 [7, 8].

At present, biomass represents approximately 14–18% of the world’s total energy con-sumption [3, 4]. In order to utilize these resources properly, biomass should be convertedto energy that can meet a sizeable percentage of demands for fuel and chemicals. Efficientutilization of biomass as a potential feedstock depends on general information about thecomposition of plant species, heating value, production yields and bulk density. Organiccomponent analysis reports on the kinds and amounts of plant chemicals, including pro-teins, oils, sugars, starches, and lignocelluloses (fibers) required much attention about theirbehavior [1, 7].

1.3 Analysis of Biomass

The main components of biomass are cellulose, hemicelluloses, and lignin:

Cellulose or carbohydrate is the principal constituent of wood and other biomass and formsthe structural framework of wood cells. It is a polymer of glucose with a repeatingunit of C6H10O5 strung together by 𝛽-glycosidic linkages. The 𝛽-linkages in celluloseform linear chains that are highly stable and resistant to chemical attack because of thehigh degree of hydrogen bonding that can occur between chains of cellulose. Hydrogenbonding between cellulose chains makes the polymers more rigid, inhibiting the flexingof the molecules that must occur in the hydrolytic breaking of the glycosidic linkages.Hydrolysis can reduce cellulose to a cellobiose repeating unit, C12H22O11, and ultimately

6 Transformation of Biomass

Table 1.4 Organic components and composition of lignocelluloses biomass (dry basis).

FeedstockCellulose(wt. %)

Hemicelluloses(wt. %)

Lignin(wt. %)

Other(wt. %)

Bagasse 35 25 20 20Bamboo 55 28 17 0Corn stover 53 15 16 16Corncob 32 44 13 11Herbaceous energy crops 45 30 15 10Rice straw 38 25 12 25Short rotation woody crops 50 23 22 5Wheat straw 38 36 16 10Wheat chaff 38 36 16 11Waste paper 76 13 11 0

to glucose, C6H12O6. Heating values for cellulose may be slightly different based uponthe feedstock [8, 9].

Hemicellulose consists of short, highly branched chains of sugars. In contrast to cellulose,which is a polymer of only glucose, a hemicellulose is a polymer of five different sugars.It contains five-carbon sugars (usually D-xylose and L-arabinose), six-carbon sugars(D-galactose, D-glucose, and D-mannose) and uronic acid. The sugars are highly substi-tuted with acetic acid. The branched nature of hemicellulose renders amorphous proper-ties which is relatively easy to hydrolyze to its constituent sugars compared to cellulose.When it hydrolyzed, the hemicellulose from hardwoods releases products which high inxylose (a five-carbon sugar). The hemicellulose that contained in softwoods, by contrast,yields six more carbon sugars [7, 8].

Lignin is the major non-carbohydrate, polypenolic structural constituent of wood andother native plant materials that encrusts the cell walls and helps in cementing the cellsall together. It is a highly polymeric substance, with a complex, crosslinked, highlyaromatic structure and having the molecular weight of about 10 000 derived princi-pally from coniferyl alcohol (C10H12O3) by extensive condensation and polymerization[1, 8, 9].

For the efficient utilization of biomass, feedstock engineers are particularly evaluating thehemicellulosic component and the distribution among cellulose, hemicelluloses, and lignin.Table 1.4 gives an idea of the organic components of some of the dedicated energy crops,common sugar, and starch crops, respectively.

1.3.1 Proximate and Ultimate Analysis of Biomass

Analysis of biomass and its characteristics is generally accomplished by both proximate andultimate analysis. Proximate analysis separates the products into four groups: (i) moisture,(ii) volatile matter, consisting of gases and vapors driven off during torrefaction or pyrolysis,(iii) fixed carbon, the non-volatile fraction of biomass, and (iv) ash, the inorganic residue thatremains after combustion. The remaining fraction is a mixture of solid carbon (fixed carbon)and mineral matter (ash), which can be distinguished by further heating the sample in thepresence of oxygen; the carbon is converted to CO2 and only leaving the ash [9]. Table 1.5

Tabl

e1.

5Th

erm

oche

mic

alpr

oper

ties

ofth

ese

lect

edbi

omas

s(p

roxi

mat

ean

dul

timat

ean

alys

is).

Prox

imat

ean

alys

isU

ltim

ate

anal

ysis

(%w

t.dr

y)(%

wt.,

dry)

Bio

mas

sH

HV

(dry

)M

J/kg

Vol

atile

Ash

FCC

HO

NS

Cl

Ash

Ref

.

Bam

boo

18.7

73.5

63.

5119

.948

.62

5.90

45.1

50.

33—

——

[10]

Cor

nst

over

17.6

575

.17

5.58

19.2

543

.65

5.56

43.3

10.

610.

010.

66.

26[9

]C

orn

grai

n17

.286

.57

1.27

12.1

644

.00

6.11

47.2

41.

240.

14—

1.27

[9]

Coc

onut

shel

l19

.45

——

—47

.97

5.88

45.5

70.

30—

—0.

50[1

1]M

aize

stra

w—

——

—47

.09

5.54

39.7

90.

810.

12—

5.77

[9]

Oliv

ehu

sk—

——

—50

.90

6.30

38.6

01.

370.

032.

80[1

2]Pi

nesa

wdu

st20

.60

——

—50

.30

6.00

43.5

00.

10—

—0.

20[1

3]R

ape

seed

26.7

0—

——

58.5

18.

5723

.46

3.67

——

5.78

[15]

Ric

ehu

ll16

.14

65.4

717

.86

16.6

740

.96

4.30

35.8

60.

400.

020.

1218

.34

[9]

Saw

dust

18.0

6470

.55

0.83

16.3

545

.66

4.86

34.9

41.

380.

06[9

]R

ice

husk

15.6

855

.519

.52

14.9

938

.43

2.97

36.3

60.

490.

070

21.6

8[9

]R

ice

stra

w16

.28

69.3

313

.42

17.2

541

.78

4.63

36.5

70.

700.

080.

3415

.90

[9]

Suga

rca

neba

gass

es17

.33

73.7

811

.27

14.9

544

.80

5.35

39.5

50.

380.

010.

129.

79[9

]Sw

itch

gras

s18

.64

81.3

63.

6115

.03

47.4

55.

7542

.37

0.74

0.08

0.03

3.50

[9]

Wat

erhy

acin

th16

.02

—22

.40

—41

.10

5.29

—1.

960.

41—

—[9

]W

heat

stra

w17

.51

71.3

08.

9019

.80

43.2

05.

0039

.40

0.61

0.11

0.28

11.4

0[9

]

8 Transformation of Biomass

provides both the proximate and ultimate analysis (dry basis) for a wide range of biomassmaterials. Ultimate analysis deals with the determination of the carbon and hydrogen inthe material, are found in the gaseous products after combustion. Using these analysis, themolecular weight analysis becomes simpler. For example, cellulose and starch having thegeneric molecular formula C1H1.7O0.83, hemicelluloses can be represented by C1H1.6O0.8and wood by C1H1.7O0.83. Typical thermochemical properties of some selected biomassmaterials based on proximate and ultimate analysis are given below (Table 1.5) [9–15].

The calorific value of the char and the conversion efficiency based on calorific valueare given in Table 1.5. The higher heating value (HHV) of the biomass is calculated byimplementing the HHVs of lignocellulosic fuels, as the equation given below [16]:

HHV(MJ/Kg) = 0.335(C) + 1.423(H) − 0.154(O) (1.1)

Chaniwala and Parikh [17] have developed an empirical correlation based on elemental andproximate analysis to predict the HHV of raw biomass as stated below:

HHV(MJ/Kg)= 0.3491(C)+ 1.1783(H)− 0.10(S)− 0.0134(O)− 0.0151(N)− 0.0211(A)

(1.2)

Here C, H, S, O, N, and A refer to the weight percent of carbon, hydrogen, sulfur, oxygen,nitrogen, and ash in biomass respectively.

1.3.2 Inorganic Minerals’ Ash Content and Properties

Fuel contains various impurities in the form of incombustible components mainly known asash. Ash itself is undesirable, since it requires purification of the flue gas for particles withsubsequent ash and slag disposal as a result. The ash from wood comes primarily from soiland sand absorbed into the bark. Wood also contains salts thus having the importance to thecombustion process. They are primarily potassium (K), and partly sodium (Na), based saltsresulting in sticky ash, which may cause deposits in the boiler unit. The Na and K contentsin wood are normally so low that they will not cause problems for traditional heating tech-nologies. Typical mineral fractions in wood chips expressed as percentage of the dry matter(DM) of the wood are shown in Table 1.6. Apart from all these individual analysis processes,NREL researchers have developed a very interesting and rapid analysis method for biomass

Table 1.6 Total inorganic components ofplant biomass (dry basis).

Elements % of dry basis

Potassium (K) 0.1Sodium (Na) 0.015Phosphorus (P) 0.02Calcium (Ca) 0.2Magnesium (Mg) 0.04Chlorine (Cl) 0.2 to 2.0Silica (Si) 0.2 to 15

Biomass, Conversion Routes and Products – An Overview 9

composition using near-infrared (NIR) spectroscopy. By applying this technique, the lightreflected off a biomass sample is analyzed to determine the sample’s composition [8, 18].

1.4 Biomass Conversion Routes

By a number of processes, biomass can be converted into solid, liquid, and gaseous fuels.The technologies include thermal, thermochemical, and biochemical conversions. Reac-tions involved during conversion are hydrolysis, dehydration, isomerization, oxidation,de-hydrogenation, and hydrogenation. The actual processes included these technologiesare combustion, pyrolysis, gasification, alcoholic fermentation, liquefaction, and so on [8].A schematic flow diagram for biomass conversion is shown in Figure 1.2. The main productsof conversion technologies are energy (thermal, steam, electricity), solid fuels (charcoal,combustibles), and synthetic fuels (methanol, methane, hydrogen gas, etc.). These can beused for different purposes such as cooking, lighting, heating, water pumping, electric-ity generation, and as industrial and transport fuels. Biomass fuels and residues can beconverted to energy via thermal, biological, chemical, and physical processes.

In a commercial process, biodiesel is produced by the reaction of vegetable oil oranimal fat with methanol in the presence of base or acid catalysts. Concerns over thedownstream processing of the homogeneous transesterification processes have motivatedintense research on the heterogeneously catalyzed transesterification process [18, 19]. Ingeneral, heterogeneous biodiesel production processes have few numbers of unit operations,with simpler separation and purification steps for products as no neutralization process isrequired. There are three types of solid catalysts: acid, base, and enzyme. Solid base cata-lysts, such as alkaline–earth metal hydroxide, oxides, and alkoxides such as Ca(OH)2, CaO,and Ca(CH3O)2 function as effective catalysts for the transesterification of triglycerides[18, 20]. The main advantage of solid acid catalysts is their ability to carry out the esteri-fication of free fatty acids and transesterification of triglycerides simultaneously [20–23].Moreover, these are reactive on esterification and transesterification reactions at relativelylow temperatures (i.e., 80 ◦C), as shown in Figure 1.3 [8].

Lipase has been shown to have a high catalytic reactivity to produce high quality biodiesel[18, 20–23]. As lipases break down natural lipids and oils into free fatty acids and glycerol,therefore this group of enzymes is widely used in the leather and detergent industries.Recent findings show that an alternative acyl acceptor, such as methyl acetate is used toreplace methanol, and it can obtain methyl ester yield up to 92%. In addition, the byproduct(glycerol) has a more expansive market, which can further be used for H2 production,acrolein, or several other chemicals [20].

In thermal conversion, combustion is already practiced widely, where as; gasificationattracts high level of interest as it offers higher efficiencies compared to combustion.Pyrolysis is interesting as it results into liquid product that offers advantages in storage, easytransport and versatility in applications, although it is still at a stage of early development[8, 23].

1.4.1 Pyrolysis

There are different types of pyrolysis carried out under various operating conditions, amongwhich fast, intermediate, flash, and slow having the substantial importance in the conversion

10 Transformation of Biomass

Ethanol, amino acid, bio hydrogen and protein based

chemicals

Ethanol, Gobar gas

Chemical conversion

Physicalconversion

Biochemical conversion

Thermo chemical

conversion

FT oil, syngas,solvents, acids

Bio-hydrogen,Conditioned gas

Direct

Indirect

Fast

Intermediate liquefaction

Flash

Slow

Vacuum

Torrefaction

Direct

Heavy oil

Bio oil, biogas, char, tar

Mechanical extraction

Briquetting

Distillation

Supercriticalconversion

Solventextraction

Hydrolysis

Leaching

Liquid liquid extraction

Acid hydrolysis

Enzymatichydrolysis

Cellulose, hemicelluloses, lignin, sugar

Primary and secondary metabolites

Cellulose, hemicelluloses,lignin

Partly microbial

Various anaerobes

Facultative group

Cyano bacteria

Klebsiella and clostridium

Batch

Fed batch

Continuous

Semi arranged continuous

flow arrangement

Enzyme

Fermentation

Anaerobic

Liquefaction

Pyrolysis catalytic/non-

catalytic

Gasification (partial air)

Combustion (excess air)

Biomass Feedstock

Photosynthesis bacteria

Figure 1.2 Different conversion routes to get end products (liquid and gases). (Adopted fromMohanty et al., 2014 [3])