(619ad) Optimization of Biomass Processing through Physical Fractionation

The nascent cellulosic biofuels industry is struggling due to challenging economics derived from high cost of cellulosic sugars relative to starch and sucrose (and recently the substantial drop in the price of petroleum) with contributions arising from the high capital and operating costs associated with large centralized lignocellulosic biorefineries. Well-recognized, critical challenges include the low bulk density represents an important challenge for the logistics of feedstock transport and storage, the substantial within- and between-feedstock heterogeneity of herbaceous feedstocks such as corn stover and switchgrass that can contribute significant challenges to processing and conversion, and the need for high-value co-products or co-products targeting diverse market sectors to both add value and to improve the economic robustness to fluctuations in both global and local market forces.

Biomass heterogeneity has important impacts on a number of important processing variables. These include differing responses of the biomass to comminution that result in wide particle size distributions, substantial differences in particle hygroscopicity and drainability, a diversity of compositions (including lignin and ash), and a wide range of responses to chemical pretreatments and hydrolysis. This work will, work will assess physical fractionation approaches for corn stover and energy sorghum that mimic industrially relevant fractionations utilizing either manual classification that mimics in-field classification that could be achieved during harvest and combinations of comminution and sieving that could be performed either during harvest or at decentralized processing depots. Employing these approaches in this work, we demonstrate that physical fractionation can yield biomass fractions with diverse properties that include wide ranges for lignin content and hygroscopicity that impact feedstock processability (i.e., response to pretreatment and enzymatic hydrolysis).