Challenges in Fuel Ethanol Production

Fuel ethanol production still represents many technological challenges, due mainly to the implicit complexity and costs of feedstock and other inputs. However, this process has been implemented at different scales, including the commercial one, through tax exemptions or subsides, which seek to lower production costs. In this article main feedstocks for ethanol production are discussed considering their production, advantages and drawbacks. The importance of conditioning and pretreatment as decisive process steps for conversion of feedstocks into ethanol is highlighted. Main methods for conditioning and pretreatmen are presented as well as the enzymatic procedures for starch hydrolysis. The need of pretreatment of lignocellulosic biomass is analyzed considering the complexity of this type of raw material. Several methods for pretreatment and detoxification of biomass are briefly described. The difficulties related to the enzymatic hydrolysis of cellulose are analyzed considering the enzyme complexes employed and the presence of solid particles in the reaction mixture. Main fermentation and concentration technologies for ethanol production are discussed. Ethanol dehydration technologies, including the most perspective, are disclosed as well. Finally, some environmental aspects of ethanol production are highlighted