Combined Dilute Acid and Solvent Based Pretreatment of Agricultural Wastes for Efficient Lignocellulosic Fractionation and Biofuels Production

A true biorefinery for processing lignocellulosic biomass should achieve maximum utilization of all major constituents (cellulose, hemicellulose, & lignin) within the feedstock.  In this work a combined pretreatment process of dilute acid (DA) and N-methyl morpholine N-oxide (NMMO) is described that allows for both fractionation and subsequent complete hydrolysis of the feedstocks (corn stover and sugarcane bagasse).  During this multi-step processing, the dilute acid pretreatment solubilizes the majority (>90%) of the hemicellulosic fraction, while the NMMO treatment yields a cellulosic fraction that is completely digestible within 48 hours at low enzyme loadings.   With both the cellulosic and hemicellulosic fractions being converted into separate, dissolved sugar fractions, the remaining portion is nearly pure lignin. When used independently, DA and NMMO pretreatments are only able to achieve ~80% and ~45% cellulosic conversion, respectively.  Mass balance calculations along with experimental results are used to illustrate the feasibility of separation and recycling of NMMO.