Organosolv Pretreatment of Lignocellulosic Biomass

The utilization of organic solvents or their aqueous solutions in the selective fractionation of biomass feedstocks, commonly referred to as organosolv pretreatments, has undergone extensive and progressive investigation in recent decades, supporting their current industrial deployment. This chapter explores the fundamental understanding of organosolv mechanisms, exploring their intricate relationship with water and solvent properties. The discussion encompasses various process options highlighting the influence of solvent choices, namely, alcohols, organic acids, ketones, ester and ethers, and catalysts, as well as operational conditions such as temperature and pressure. Most noteworthy, the impact of solvent properties, in particular the boiling point and miscibility, on downstream processing is specially addressed. Emphasis is placed on the consequential effects of these factors on lignin and hemicellulose recovery, cellulose digestibility by enzymes, and the overall integrated upgrade of the biomass feedstocks. Finally, this chapter addresses the economic and environmental sustainability of the organosolv processes, considering their full integration into the biorefinery concept.