Production of ethanol from lignocellulosic biomass

Abstract

Ethanol fuel is leading the transition towards a post-petrol era in the transport sector worldwide. Ethanol is produced via sugar fermentation processes by yeasts or bacteria. Although the current industrial production of ethanol mainly involves the use of starch- and sugar-based feedstocks, lignocellulosic biomass is expected to play a key role as renewable, carbohydrate-rich raw material. With the aim of placing lignocellulosic ethanol into the market, the scientific community has made great efforts to develop and implement efficient conversion technologies. Prior to fermentation, lignocellulosic biomass must be pretreated and hydrolysed to obtain the fermentable sugars. Biomass processing is, however, a major limiting step since it is hindered by the native structure of lignocellulose and generates different biomass-derived compounds that are inhibitors of the subsequent microbial conversion. In this context, different pretreatment, delignification and detoxification methods have been investigated to produce less inhibitory pretreated materials. Furthermore, several strategies such as working at high gravity conditions, high temperatures and/or different process configurations, have been shown to maximize ethanol production from lignocellulosic materials. The development of robust microbial strains tolerant to inhibitory compounds and capable of converting sugar mixtures is also needed for cost-effectiveness of the process. This chapter compiles recent advances in lignocellulosic ethanol production processes, from novel raw materials or fermenting microorganisms to new processing technologies addressed to commercialization.