Depolymerization of corn stover by urea-hydrothermal pretreatment for efficient biomethane production and microbial community analysis of anaerobic digestion

Abstract

The present study investigated the depolymerization products, biomethane production, and microbial community of corn stover (CS) depolymerized with urea using a hydrothermal approach. For the combined depolymerization, urea concentrations of 0%–4%, hydrothermal temperatures of 150 °C, and retention times of 10–50 min were utilized. Hydrothermal depolymerization predominantly converted the solid phase of CS to total volatile fatty acids and oligomers, whereas the addition of urea facilitated the breakage of the ester bonds in the lignocellulose structure, making more components accessible. Additionally, the level of total volatile fatty acid and total phenol increased up to 552.0% and 1559.5% more than the control, which was correlated to the depolymerization of solid components in CS. The urea and hydrothermal parameters had apparent effects on the compositions of the hydrolysate. Accordingly, the depolymerization with 2% urea and 10 min of hydrothermal time produced 22.3% more cumulative biomethane yield with 7 days less T80 (the time required to produce 80% of the total potential biomethane). The microbial community analysis revealed that the combined depolymerization could facilitate the acetate–methane pathway by fostering the growth of Proteiniphilum, DMER64, Sedimentibacter, and Methanosarcina, thereby enhancing biomethane production. These findings demonstrated that the combination of urea and hydrothermal depolymerization could improve the anaerobic conversion efficiency of CS to biomethane.