Scalable technologies for lignocellulosic biomass processing into cellulosic ethanol

Abstract

Major innovative breakthroughs in lignocellulose biotechnology offer significant opportunities for the utilization of agro-industrial residues like sugarcane bagasse, rice straw, corn stover into renewable fuels and biochemicals. Pretreatment is an inevitable and pivotal step to harness the sugars from the biomass effectively. These cellulosic sugars so-called second-generation (2G) are renewable and have the potential to replace conventional gasoline-derived chemicals and fuel, in a sustainable manner. However, the successful operation at large scale and production cost of cellulosic ethanol and renewable chemicals are two major concerns. Biomass conversion steps, i.e., pretreatment, large-scale enzymatic hydrolysis and fermentation, are critical and the cornerstone is the success of overall lignocellulose biorefineries. Only a handful of biomass pretreatment technologies such as a steam explosion, mild dilute acid pretreatment followed by a steam explosion, and ammonium hydroxide-mediated delignification is scalable and has the potential to be operated at the demonstration or commercial scale. Later, enzymatic hydrolysis using high total solids amounts (pretreated biomass) without any filtration and conditioning steps may provide economic sugars production. Each cellulosic ethanol producer has its technology as it largely depends on the feedstock and the operational conditions. Hence, the pretreatment conditions have to optimize by limiting the plant flexibility, which favors the handling of variant feedstocks in the same premise conditions. This situation necessitates the development of versatile pretreatments to process the variety of biomass feedstock using the minimum facilities and chemicals, eventually making process raw material independent. This chapter summarizes the recent developments made biomass processing (primary pretreatment methods, enzyme hydrolysis, fermentation, and distillation) into cellulosic ethanol.