• • Optimal THP conditions for corn straw: solid-to-liquid ratio 51.0–57.5 mg·mL−1, time 74–81 min, temperature 182.5–197.5 °C, yielding a 66.7% increase in cumulative methane production (from 218.0 to 362.9 mL·g−1 VS) compared to untreated straw.
• • THP significantly alters biomass structure: lignin content drops from 21.5% to 8.3% and crystallinity index (CrI) from 70.83% to 61.95%, enhancing cellulose accessibility and microbial degradation.
• • Inhibitory derivatives (furfural, 5-methylfurfural, phenol) are generated at concentrations up to 23.14 mg·L−1, with a theoretical combined inhibition rate of 7.26%—far lower than the 66.7% promotion effect, confirming process viability.
• • Dose-response analysis reveals IC50 values for furfural, phenol, and 5-methylfurfural as 0.0471±0.0092, 0.3201±0.0732, and 0.2788±0.1101 g·L−1, respectively, indicating that derivative inhibition could be further mitigated to enhance methane yields.