Optimization of Thermal Hydrolysis Pretreatment of Corn Straw for Enhanced Methane Production
Low hydrolysis efficiency is a core bottleneck in anaerobic digestion (AD) of lignocellulosic agricultural residues, limiting methane production and resource utilization. This study optimized thermal hydrolysis pretreatment (THP) of corn straw (CS) using response surface methodology (RSM) to enhance methane yield. The optimal conditions were determined as solid-to-liquid ratio of 51.0–57.5 mg·mL−1, pretreatment time of 74–81 min, and temperature of 182.5–197.5 °C. Under the optimal combination (52.3 mg·mL−1, 78.4 min, 191 °C), cumulative methane yield increased from 218.0 to 362.9 mL·g−1 VS, a 66.7% improvement over untreated CS. Characterization via XRD, FTIR, and SEM revealed that THP disrupted the lignocellulosic structure, reducing lignin content from 21.5% to 8.3% and crystallinity index (CrI) from 70.83% to 61.95%. Inhibitory derivatives generated during THP included furfural (1.69 mg·mL−1), 5-methylfurfural (2.44 mg·mL−1), and phenol (23.14 mg·L−1), with a theoretical combined inhibition rate of 7.26%. The promotion effect on methane production (66.7%) far exceeded the theoretical inhibition (7.26%), indicating that THP under optimized conditions is effective and environmentally controllable. This study provides a systematic framework for optimizing THP parameters to maximize methane production from agricultural residues.