Yanni Sudiyani, Kiky Corneliasari Sembiring, and Indri Badria Adilina

Contents

20.1 Introduction…………………………………………………………………………………………………… 346

20.2 Lignocellulosic Biomass……………………………………………………………………………………. 346

20.3 Processing of Lignocellulose to Bioethanol…………………………………………………………….. 347

20.3.1 Pretreatment……………………………………………………………………………………… 347

20.3.2 Saccharification………………………………………………………………………………….. 353

20.3.3 Fermentation…………………………………………………………………………………….. 356

20.3.4 Separation and Purification…………………………………………………………………….. 360

20.4 Conclusions and Perspectives……………………………………………………………………………… 361

References ……………………………………………………………………………………………………………. 362

Abstract The demand for ethanol as a substitute of gasoline is rapidly increasing due to the recent increase of imbalance in oil market and interest in environmental issues. First-generation (G1) bioethanol which is currently derived mainly from food crops generate many problems such as net energy losses, greenhouse gas emis­sion, and increased food price. On the other hand, biofuel produced from lignocel — lulosic materials, so-called second-generation (G2) bioethanol, shows environmental advantages in comparison to G1. The development of bioethanol G2 from lignocel- lulosic materials possesses many advantages from energy and environmental aspects. Efficient conversion of lignocellulosic biomass to ethanol and value-added biochemicals is still today a challenging proposition. Basically, four steps are included in the production process of bioethanol G2, composed of pretreatment, saccharification, fermentation, and product separation/purification. In each step, there are several ideas to improve its productivity and benefitability. In this chapter,

Y. Sudiyani (*) • K. C. Sembiring • I. B. Adilina Research Center for Chemistry, Indonesian Institute of Sciences, Kawasan Puspiptek Serpong, 15314 Tangerang, Indonesia e-mail: sudiyani@gmail. com

K. R. Hakeem et al. (eds.), Biomass and Bioenergy: Processing and Properties,

DOI 10.1007/978-3-319-07641-6_20, © Springer International Publishing Switzerland 2014 we describe some details about the production process selection or ideas. New studies such as catalytic conversion of lignocellulosic biomass are also rapidly developing, although they are not yet mature to be utilized for industrial purposes.

Keywords Bioenergy • Lignocellulosic biomass • Pretreatment • Enzymatic saccharification • Catalytic conversion • Fermentation • Bioethanol

20.1 Introduction

Bioethanol, as a liquid fuel by the fermentation of renewable biomass, is important from viewpoint of global environmental protection. Biomass which includes animal and human waste, trees, shrubs, yard waste, wood, grasses, and agriculture residue is a renewable resource that stores energy from sunlight (McKendry 2002). Biofuel produced from lignocellulosic biomass, so-called second-generation (G2) bioetha­nol, shows environmental advantages in comparison to first-generation (G1) bio­ethanol from starch or sugar. However the conversion of lignocellulosic biomass to ethanol is more challenging due to the complex structure of the plant cell wall. The physical and chemical barriers caused by the close association of the main compo­nents of lignocellulosic biomass hinder the hydrolysis of cellulose and hemicellu — lose to fermentable sugars. Pretreatment is needed to alter the structural and chemical composition of lignocellulosic biomass to facilitate the rapid and efficient hydrolysis of carbohydrate to fermentable sugars (Chen et al 2005). The subject of this chapter emphasizes the lignocellulosic biomass in preparation for pretreatment, enzymatic saccharification, and fermentation for bioethanol G2 production and related studies on their catalytic conversion.