ABSTRACT
Bioethanol is an attractive and eco-friendly biofuel that can be used as an effective replacement for fossil fuels. It is produced from renewable sources through fermentation of sugars. Over the past several years, sugar and starch-based feedstocks have been widely used for generating ethanol on large scale. However, the ethical issues and rising debate on food versus fuel have led to finding out the promising ethanol feedstock from nonfood sources. As a result, current research efforts extensively focus on ethanol production from lignocellulosic biomasses (LCBs), which are mostly waste materials, inexpensive, abundant and noncompetitive with food, and grown on arable lands. LCBs originate from the nonfood sources such as agricultural wastes, forest biomass and residues, perennial grasses, dedicated energy crops, aquatic plants, municipal solid wastes, and industrial wastes. Ethanol production from LCBs basically includes (1) pretreatment of the biomass to release cellulose and hemicellulose from lignocellulosic complex, (2) hydrolysis of the pretreated biomass to generate fermentable sugars, (3) fermentation of the sugars by yeast to produce ethanol, and (4) recovery of ethanol through distillation. Much improvement has been made in recent years on the 146technological approaches for better conversion efficiency and enhanced ethanol yield. This chapter has been designed to present an overview of the ethanol production from LCBs that covers sources and composition of LCBs, pretreatment, hydrolysis, fermentation, microorganisms, and technological achievements.
