(90a) Advances in Protic Ionic Liquids for Biomass Conversion into Biofuels and Bioproducts

Authors: 
Simmons, B. A., Lawrence Berkeley National Laboratory
The transformation of biomass into biofuels and bioproducts is of great importance in terms of bolstering the US bioeconomy and meeting national GHG reduction goals. Previous work at the DOE Joint BioEnergy Institute (JBEI, www.jbei.org) has demonstrated the capability of specific ionic liquids (ILs), such as 1-ethyl-3-methylimidazolium acetate ([C2C1Im][OAc]) and cholinium lysinate ([Ch][Lys]), to be effective biomass pretreatment solvents. Using these ILs for an integrated biomass-to-biofuel configuration is still challenging due to a significant water-wash process that is required due to the high toxicity of [C2C1Im][OAc] and pH adjustment prior to saccharification for the highly basic [Ch][Lys]. In this work, we demonstrate, We have developed and demonstrated a process based on the use of a protic IL (PIL), ethanolamine acetate, without pH adjustments, water-wash and solid–liquid separations. After pretreatment, the whole slurry is directly used for simultaneous saccharification and fermentation (SSF) with commercial enzyme cocktails and wild type yeast strains, generating 70% of the theoretical ethanol yield (based on switchgrass). The structure–performance relationships of PILs in terms of lignin removal, net basicity, and pH value are systematically studied. A technoeconomic analysis (TEA) revealed that an integrated biorefinery concept based on this PIL process could potentially reduce the minimum ethanol selling price by more than 40% compared to scenarios that require pH adjustment prior to SSF. Improvement of the economic performance will be made by reducing the dilution and enzyme loading during SSF as identified by TEA. This effort demonstrates the impact of a biocompatible PIL in terms of process optimization and conversion efficiency, and opens up avenues for realizing an IL based efficiently integrated biomass conversion technology.