Challenges and Opportunities for Gamma-Valerolactone in Biomass Pretreatment

Solvent-aided biomass pretreatment strategies for biorefineries need to address several key points including effective biomass valorization, energy demand, and waste minimization. More specifically, solvents' yield, recovery, and recycling are crucial parameters to improve biorefineries' environmental and economic performances. Gamma-valerolactone (GVL) presents significant promise in biomass pretreatment due to its ability to effectively remove hemicellulose and lignin or provide near-complete biomass solubilization and facilitate hydrolysis. However, GVL utilization is challenging due to its higher cost and the difficulty of recycling it as a high-boiling solvent. Herein, we discuss biomass pretreatment with GVL and solvent recovery. GVL recovery, being conceptual at this stage, has to be proven in the field. It could be realized through liquid–liquid extraction. However, most studies do not address the reutilization of GVL, the separation of heavy-boiling impurities, or the solid–liquid separation of the remaining solids, which are significant gaps in the literature and a limitation to industrialization.