Michael P. Garver, Shijie Liu*

Department of Paper and Bioprocess Engineering, College of Environmental Science and Forestry,
State University of New York, Syracuse, NY, USA
*Corresponding author email: sliu@esf. edu

OUTLINE

Introduction 457

Characteristics of Lignocellulosic Biomass 458

An Overview on Biomass Conversion 461

Pretreatment—Biomass Size Reduction by Physical or Mechanical Methods 462

Mechanical Pretreatment—Chipping, Grinding,

Milling, Refining 463

Irradiation Pretreatment by Electron Beam, Gamma Ray, or Microwave 465

Ammonia Recycle Percolation Pretreatment 465

Ozonolysis Pretreatment 465

Organosolv Pretreatment 466

Oxidation Pretreatment 466

Ionic Liquid Pretreatment 467

Sulfite Pretreatment to Overcome Recalcitrance of Lignocelluloses 468

Hot Water 469

Steam Explosion 470

Ammonia Fiber Explosion 473

Supercritical Carbon Dioxide Explosion 473

Biological Pretreatment 474

Acid Hydrolysis 474

Alkaline Hydrolysis 475

Hydrolysis 476

Bioconversion—Converting Sugars to Products 477

Thermochemical Conversion 478

Combustion 478

Gasification 478

Pyrolysis 481

Direct Liquefaction 481

Conclusion 482

References 482

INTRODUCTION

A biorefinery is a complex industrial system to convert raw biologically derived materials into usable and valuable products. The actual design of a bio­refinery depends on the desired product, the raw mate­rials available, and the method of conversion desired.

For the purposes of this chapter, the raw material considered is woody biomass or more generally,
lignocellulosic biomass (LB). LB may originate from for­est, herbaceous plants or organic waste streams such as sewage, food processing waste, or animal manure.

LB is a source of energy that can reduce the consump­tion of fossil fuels. Energy independence is an important economic and political goal. Renewable sources of energy are also critical for a balanced ecological policy.

Biorefineries may be designed to output a specific set of products and by-products. These products include

Bioenergy Research: Advances and Applications http://dx. doi. org/10.1016/B978-0-444-59561-4.00027-9

biofuels, adhesives, surfactants, biochemicals, biopoly­mers, food and medicine. This chapter will focus on some common products such as acetic acid, ethanol, butanol, acetone, hydrogen, and polyhydroxyalka — noates. These products stem from the fermentation of sugars derived from LB or they may be derived from thermochemical conversion processes.

The first objective in any conversion is to reduce the size and increase the surface area of the raw material. This enables subsequent treatment methods to attack and exploit specific properties of LB more effectively to obtain sugars for bioconversion or obtain products from thermochemical conversion.

Secondary treatment or conversion methodologies include some form of hydrolysis, fermentation or any of a variety of thermochemical conversion treatments. The objective of these methods is to break lignin and complex carbohydrates into either simple sugars or intermediate products or even down to CO and H2 (syn­gas) for further fermentation (bioconversion) or thermo­chemical conversion. Fermentation is usually followed by separations or filtrations as final steps in the acquisi­tion of a desired product in a bioconversion.