Low-Temperature Hydrothermal Modification with Fe/C Catalysts for Enhancing Corn Stover Anaerobic Digestion Performance and Modeling Development for Predicting Biomethane Yield

This study investigated the enhancement of corn stover (CS) anaerobic digestion (AD) performance through low-temperature hydrothermal modification (HM) with Fe/C catalysts and developed two predictive models for biomethane yield (BY). CS was modified with Fe/C at 50 °C and then anaerobically digested. The results indicated that Fe/C significantly improved CS hydrolysis efficiency, indicated by increasing concentrations of glucose, mannose, xylose, and volatile fatty acids (VFAs), which were 1.9, 1.7, 3.0, and 1.8 times higher than those of HM alone, respectively. The enhanced hydrolysis of CS effectively improved AD performance, leading to a BY increase of 25.5% as compared to the control group. The time to reach 90% of the maximum BY (T90) was also reduced by 7 days. Furthermore, the developed GM(1,N) gray system model effectively simulated multi-parameter coupling effects in AD processes under small-sample conditions (n < 20), demonstrating high accuracy (average percentage deviation [APD] = 4.50%) and enabling correlation analysis between modification parameters and BY. The ANN-GA model exhibited superior accuracy in BY prediction. This study demonstrated the effectiveness of low-temperature HM-Fe/C in enhancing BY and the accuracy of two models in predicting BY.