Comparative metagenomics reveals the higher methanogenic potential of fresh corn stalks over dry corn stalks

Crop stalks, typically converted to methane through anaerobic digestion post-drying, suffer from reduced methanogenic efficiency due to nutrient loss during the drying process. Fresh stalks, with a higher organic matter content, have greater methanogenic potential, while research on this topic is scarce. This study compared the methanogenic potential of fresh and dry corn stalks (F-CS and D-CS), both in mono-digestion and co-digestion with cattle manure. Results showed that mono-digestion led to serious acid inhibition in F-CS due to rapid hemicellulose degradation, resulting in lower methane production compared to D-CS. Remarkably, introducing cattle manure significantly bolsters the fermentative capacity of F-CS, with F-CS showing a 23.74% higher cumulative methane yield than D-CS in co-digestion. Flavobacterium was essential for enhancing the buffering capacity in this process. Metagenomics analysis indicated that co-digestion curtailed hydrolysis and acidification rates, fostering methanogenesis pathways reliant on carbon dioxide, CO₂, methylamine, and methanol as substrates, thus mitigating acid inhibition in F-CS and maximizing its methane production potential. This study highlights the enhanced bioconversion efficiency of F-CS in methane production when co-digestion with cattle manure, establishing a theoretical basis for the high-value conversion of crop stalks into methane.