Effect of air mixing on high-solids anaerobic digestion of cow manure: Performance and mechanism

Abstract

This study aimed to further investigate the effect of air mixing on the performance of a high-solids anaerobic digestion system and reveal its underlying mechanisms via analyses of carbon conversion, microbial communities and key functional genes. When the air mixing intensity was 12.5, 37.5 and 62.5 mL/(L‧min), compared with the anaerobic digestion without air mixing, the methane yield was increased by 6 %, 13 % and 6 %, respectively. The improved performance was partly attributed to the increased hydrolysis rate of macromolecular substances by 5 %–16 % and carbon recovery in the form of methane by 6 %–7% compared with the controls. Functional flora (Magnetospirillum, Synergistaceae) and hydrolytic metabolism-related enzymes (cellulose, α-amylase) demonstrated higher abundance under air mixing condition, thus promoting the degradation of organic matter and methane production. This work provides some new insights into the use of air mixing to improve anaerobic digestion of high-solids waste.