The scum layer of straw anaerobic digestion significantly impacts biogas production efficiency. The initial floating of straw after entering the reactor is an important reason for scum layer formation. Improving the settleability of straw particles and reducing the initial floating time of straw are crucial to suppressing the scum layer, and accelerating the water absorption rate of straw entering the reactor is the key to reducing the floating time. Therefore, in this study the corn stalks were kneaded and rolled, and the stalk particles were tested for water absorption and aerobic hydrolysis. The results showed that the water absorption rate of the stalks after conditioning was significantly accelerated, and the water absorption rate was 120% higher than that of the untreated stalks after absorbing water for 12 h. Simultaneously, aerobic hydrolysis destroys the lignocellulose structure to a certain extent, increases the porosity of the stalk particles, and further improves the settleability of the stalk particles. In the subsequent anaerobic digestion process, scum decreased significantly: the scum layer volume ratio was 13% lower than untreated stalks. The methane production efficiency of anaerobic digestion was significantly improved, and the optimal hydrolysis time was 12 h. At this time, the cumulative methane production of the milled treated stalks reached the maximum value of 319.64 mL/g VS, which was 26.59% higher than that of the untreated stalks.

To improve the conversion efficiency of propionic acid in the post-anaerobic fermentation of biogas slurry, the anaerobic fermentation process using biogas slurry with a high acid content was simulated in an anaerobic reactor at 35 ± 0.5 °C using sodium propionate as the sole substrate. The effects of different electron acceptors (NO₃⁻, SO₄²⁻ and Fe³⁺) on propionic acid conversion and the succession of microbial community structures were investigated. The results showed that the experimental group with the electron acceptor NO₃⁻ exhibited the best anaerobic fermentation effect, with a maximum propionate removal rate of 94%, which was 36% higher than the control group without an electron acceptor. The maximum methane production rate was 307.6 mL/g COD, an increase of 30% compared with the control group. Thauera, Aquabacterium, Desulfomicrobium, Clostridium_sensu_stricto_1, and other functional microorganisms were all enriched. The dominant functional genes related to redox reactions, such as K03711, K00384, and K03406, were highly enriched in the reactor when Fe³⁺ and NO₃⁻ were added. The study shows that adding an electron acceptor can enhance interactions between microorganisms, achieve efficient propionate conversion, and improve methane production in the system.