Ionic Liquid Assisted Lignocellulosic Biomass Fractionation for Renewable Biofuel Production

Abstract

Efficient separation of cellulose, hemicellulose, and lignin is critical for unlocking lignocellulosic biomass as a feedstock for biofuels. This work investigates imidazolium based ionic liquids (ILs) featuring amino acid anions that selectively disrupt hydrogen bonding networks while preserving fermentable sugars. At 120?°C and atmospheric pressure, optimized ILs dissolve >80?% of lignin within 90?min, leaving a cellulose rich pulp with crystallinity index reduced by 35?%, thereby enhancing enzymatic hydrolysis. Recovered lignin exhibits low molecular weight (<2?kDa) and high phenolic hydroxyl content, rendering it suitable for high value additives. A closed loop IL recovery scheme using temperature swing sedimentation demonstrates 94?% solvent recyclability over five cycles. Downstream fermentation of hydrolysates with engineered Saccharomyces cerevisiae achieves ethanol titers of 62?g?L?¹, comparable to starch derived processes. Overall process modeling predicts a minimum fuel selling price of US?$1.85?L?¹ gasoline equivalent at commercial scale.

Keywords: Ionic liquids, Biomass fractionation, Lignocellulose, Bioethanol, Green processing