Performance, interaction, and metabolic pathway of novel dry–wet anaerobic digestion for treating high-solid agricultural waste

Anaerobic digestion (AD) with high-solid content of agricultural waste often leads to the accumulation of volatile fatty acids (VFAs) due to the imbalance of the functions of hydrolytic acidification bacteria and methanogenic archaea. This study developed a novel dry–wet AD of high-solid content was developed to make acidogenic bacteria and methanogenic archaea having higher collaboration ability. The results showed that the dry–wet AD system achieved a dynamic balance and synergistic effect between hydrolytic acidification and the methane production process, which shortened the lag phase to a minimum of 1.21 days. Additionally, the system exhibited a highest volumetric biogas production rate of 1.76 L L−1 d−1 when CM:CS and the initial pH were 6:4, 8.0, respectively. The total VFA concentration reached a maximum of 4.69 g L−1 d−1 and acetic acid (HAc) and butyric acid (HBu) were dominant VFAs (88.75%–93.27%) in the leachate in hydrolytic acidification phase. Metagenomic analysis indicated Pseudomonadales, Clostridiales, Bacteroidales, Spirochaetales, and Methanosaeta were dominant microorganism in hydrolytic acidification phase and methanogenic phase, respectively. The gene abundance of key enzymes in the acetoclastic methanogenic pathway significantly exceeded that of the hydrotrophic methanogenic pathway. This study provides a novel AD technology and insights into the energy conversion of agricultural waste.