Design of a combined ionosolv-organosolv biomass fractionation process for biofuel production and high value-added lignin valorisation

Abstract

IonoSolv pretreatment using protic ionic liquids has shown impressive biomass fractionation performance and ionic liquid recyclability. Lignin condensation during ionoSolov pretreatment can lower its economic value and potentially limit the valorisation of lignin to produce high value materials. Organosolv pretreatment is known for generating a high-quality lignin fraction with a large potential for value-added applications. In this study, a hybrid fractionation process was designed based on ionoSolv and organosolv pretreatments, and was tested on two representative feedstocks, Miscanthus and pine. Compared to ionoSolv processing, the hybrid pretreatment displayed an improved fractionation performance by generating a cellulose-rich pulp which was more enzyme-accessible, and by removing a higher proportion of lignin. Saccharification yields reached 89% and 74% for Miscanthus and pine, respectively. The process was also able to maintain its high fractionation performance up to 50 wt% biomass loading. HSQC spectroscopy and GPC were used to characterise the isolated lignin. Alcohol induced α-alkoxylation took place during lignin fractionation and obstructed the lignin condensation, resulting in an improved quality lignin. A technoeconomic analysis was conducted for this new hybrid pretreatment, showing lower energy consumption for the IL regeneration step at a high organic solvent concentration, suggesting lower environmental impact and higher economic potential. This ionoSolv-organosolv pretreatment could be a milestone for the development of the current ionoSolv pretreatment at commercial scale.