Ed de Jong Richard J. A. Gosselink2

1Avantium Chemicals, Amsterdam, The Netherlands, 2Food and Biobased Research,
Wageningen UR, Wageningen, The Netherlands
Corresponding author email: ed. dejong@avantium. com

OUTLINE

Introduction 278

Occurrence and Composition of Lignocellulosic

Biomass 278

Storage Carbohydrates 280

Structural Carbohydrates 280

Cellulose 280

Hemicelluloses 280

Glucuronoxylans 280

Glucomannan 282

Xyloglucans 282

Galactoglucomannans 282

Arabinoglucuronoxylans 282

Arabinogalactan 282

Arabinoxylan 283

b-(1/3, 1/4)-Glucans 283

Complex Heteroxylans 283

Conclusions on Carbohydrate Feedstocks 283

Lignin 283

Pretreatment Technologies 286

Steam Explosion 286

Liquid Hot Water 288

Wet Oxidation 288

Dilute and Concentrated Acid Pretreatment 289

Alkaline (Lime) Pretreatment Process 289

Pretreatment Technologies Still at a Laboratory/

Conceptual Stage 290

Ammonia Fiber Explosion/Ammonia Recycle Percolation) 290

Ionic Liquids 291

Sub/Supercritical Treatments 291

Summary of Lignocellulosic Biomass Pretreatments 291

Lignocellulosic Biorefineries—Classification 292

C6 and C6/C5 Sugar Platform 295

Fermentation Products 295

Chemical Transformation Products 296

Lignin Platform 296

Importance of Furans and Aromatics as Building

Blocks for Chemicals and Fuels 297

Carbohydrate Dehydration 298

Introduction 298

Furfural Production and Applications 298

5-Hydroxymethylfurfural Formation from Hexose Feedstock 301

Relevance of 5-Hydroxymethylfurfural as a Platform Chemical 304

Conversion of Technical Lignins into

Monoaromatic Chemicals 305

Base-catalyzed Depolymerization 305

Acid-catalyzed Depolymerization 305

Pyrolysis 305

Oxidative Depolymerization 306

Reductive Hydrodeoxygenation 306

Solvolysis 307

Sub — and Supercritical Water 307

Supercritical Solvents 308

Ionic Liquids 308

Future Perspectives of Lignin Aromatics 308

Conclusions and Further Perspectives 309

References 309

Bioenergy Research: Advances and Applications http://dx. doi. org/10.1016/B978-0-444-59561-4.00017-6

INTRODUCTION

Around the world significant steps are being taken to move from today’s fossil-based economy to a more sus­tainable economy based on biomass. A key factor in the realization of a successful biobased economy will be the development of biorefinery systems allowing highly efficient and cost-effective processing of biological feed­stocks to a range of biobased products, and successful integration into existing infrastructure. The recent climb in oil prices and consumer demand for environmentally friendly products have now opened new windows of opportunity for biobased chemicals and polymers. Industry is increasingly viewing chemi­cal and polymer production from renewable resources as an attractive area for investment. Within the biobased economy and the operation of a biorefinery there are sig­nificant opportunities for the development of biobased building blocks (chemicals and polymers) and materials (fiber products, starch derivatives, coatings, resins, etc.). In many cases this happens in conjunction with the pro­duction of bioenergy or biofuels. The production of bio­based products could generate US$ 10—15 billion of revenue for the global chemical industry. The economic production of biofuels is often a challenge. The copro­duction of chemicals, materials, food and feed can generate the necessary added value.

The world is more and more confronted with the reduction of fossil oil reserves, strong fluctuations of fossil fuel prices and the increase in CO2 emissions and the ensuing problem of the greenhouse gas effect. Recent development on the production of shale gas at various places in the world might change this picture on the short term, but the disadvantages associated with fossil resources stay in place. These environ­mental, social and economic challenges have created the need for sustainable alternatives to fossil fuels and chemicals (Brown, 2003; Kamm et al., 2006). The use of plant biomass as starting material is one of the alternatives to reduce the dependency on fossil oil for transportation fuels and is the main alternative to replace petrochemicals. The biomass can be trans­formed into energy, transportation fuels, various chem­ical compounds and materials such as natural fibers by biochemical, chemical, physical and thermal processes (Brown, 2003; Huber et al., 2006; Gallezot, 2012; Climent et al., 2011a, b; Lichtenthaler and Peters, 2004). The fermentation and the chemical conversion of carbohy­drates into value-added compounds has received increasing interest in the last decade, and in a bio­refinery different advantages may be taken from both processes (Kamm et al., 2006; Gallezot, 2012; Climent et al., 2011a; Lichtenthaler and Peters, 2004; Spiridon and Popa, 2008; Lin and Huber, 2009; Stocker, 2008; Dhepe and Fukuoka, 2008). However, the poten­tial competition with food and feed applications and the consequent rise in feedstock prices is an important aspect to take into consideration. Therefore the use of lignocellulosic feedstocks (often referred to as second — generation feedstocks) is strongly advocated. In addi­tion to carbohydrates also substantial amounts of lignin is produced when using lignocellulosic feedstocks. In this chapter the composition of lignocellulosic biomass is discussed followed by an overview of the most important pretreatment and fractionation technologies. Especially the effect of the different technologies on the subsequent fermentative/chemocatalytic conver­sions is addressed. The importance is illustrated by an overview of the most important commercial as well as anticipated chemical building blocks from car­bohydrates and lignin with a special emphasis on the production of furan-based building blocks from carbo­hydrates and aromatic building blocks originating from lignin.