Clean fractionation of cell wall components in corn stover and their characterization for biorefinery processes

Organosolv fractionation processes represent convenient methods to separate various biopolymers in the plant cell wall. Clean Fractionation (CF) is a particular type of organosolv process originally developed for woody feedstocks. The original CF process uses methyl isobutyl ketone (MIBK)/ethanol/water with a catalytic amount of sulfuric acid at temperatures ranging from 120°C to 160°C. Understanding the feasibility and applicability of organosolv processes for industrial use will require mass balances on the primary polymers in biomass coupled to detailed understanding of the physical and chemical characteristics of the fractionated components and viable upgrading processes. In this paper, we apply two CF approaches to corn stover at the bench-scale, one with MIBK/ethanol/water and the other with MIBK/acetone/water, with acid. We examine the full mass balance on resulting solid, organic, and aqueous fractions, and apply multiple analytical methods to characterize the three fractions. Total mass yields of the cellulose-enriched, hemicellulose-enriched, and lignin-enriched fractions are near 100% in all cases. For corn stover, the MIBK/acetone/water CF approach was found to perform more effectively relative to the original CF method, mainly based on the enhanced fractionation susceptibility of the aqueous and organic phases. At 140°C with 0.1 M H₂SO₄, 84% of cellulose and 96% of lignin in corn stover were fractionated, meaning that this CF technique can separate the main three components efficiently. This study also provides key inputs, along with optimization of the enzymatic deconstruction of the insoluble carbohydrate fraction remaining, for a techno-economic and life cycle analysis of CF processes based on bench-scale data.