Solvent Pretreatments of Lignocellulosic Materials to Enhance Biogas Production: A Review

Biogas production via anaerobic digestion is a constantly growing technology all around the world. Lignocellulosic materials (LMs) present several features that make them particularly attractive among the organic substrates commonly employed in anaerobic bioreactors. However, their recalcitrance to biological conversion still hinders their application for commercial production of biogas and requires a pretreatment step to improve their microbial degradability. Among the several pretreatments proposed for LMs, cellulose solvents and organosolv pretreatments are arising as the most effective in disrupting the bonds among cellulose, hemicellulose, and lignin, thus increasing the accessible surface area of the biodegradable matter for microbes. Here, the solvents that have been employed as pretreatment to enhance the biogas production yields from the anaerobic digestion of LMs are reviewed, examining the dissolution mechanisms involved, as well as the main advantages and drawbacks for their full-scale application.