Ferrihydrite enhance performance in anaerobic digestion of pig manure: methane production, Feammox and metabolic pathway

High ammonia nitrogen and low electron transfer rate lead to low methane generation efficiency during pig manure anaerobic digestion. This study aimed to find the effect of ferrihydrite on methane production from anaerobic digestion of pig manure, and the mechanism on ferrihydrite influencing methane production. The results showed that 0.1-0.5 g/L ferrihydrite could promote the production of methane, which was 46.9-84.8% higher than that of the control group. It showed high hydrolysis, acidogenesis and methanogenesis rates. Ferrihydrite was beneficial to the continuation of Feammox process. From the microorganism point of view, it showed higher expression of functional genes. These understandings will help to reveal the influence of ferrihydrite affecting mechanism microorganisms and substrates on the biochemical metabolism process of anaerobic digestion of pig manure, so as to provide effective guidance for higher methane conversion.