Processes for Pretreating Lignocellulosic Biomass: A Review

Pretreatment processes including comminution, alkali swelling, acid hydrolysis, steam and other fiber explosion techniques, and exposure to supercritical fluids are reviewed. Discussion focuses on the mechanisms by which different pretreatments act and the influence of biomass structure and composition on the efficacy of pretreatment. This analysis is used to evaluate directions for futureadvanced pretreatment research. In the near term, the potential to achieve further improvements in the existing (NREL) dilute acid hydrolysis process needs to be explored. This can be done using sensitivity analyses to quantify the extent to which additional energy and/or chemical inputs can be used to improve bioconversion rates and yields or to reduce energy requirements. In the longer term,the strategy is to develop pretreatments that produce high yields with no byproduct formation.