Microaerobic conditions during the co-digestion of manure with straw; effect on process performance and microbial communities

Efficient treatment methods applied during anaerobic digestion (AD) of lignocellulosic substrates can favour the utilisation degree of biomass and subsequently, the sustainability of the whole process. The addition of limited amounts of oxygen to biogas reactors can boost lignocellulose’s deconstruction and increase biomethanation.

In this study, the result of microaerobic conditions on AD process performance and also, on microbiome changes during the co-digestion of cattle manure with wheat straw was evaluated. It was shown that microaerobic conditions managed to improve the methane yield by approximately 7%. Conversely, the pH and volatile fatty acids accumulation were not significantly affected and thus, oxygen injection did not provoke any inhibition to the process performance.

Regarding the microbial communities, a clear shift in the bacterial populations during the limited aeration was not observed. On the contrary, a few members of the archaeal community were found in higher relative abundance due to microaeration. Specifically, methanogens similar to Methanosarcina sp. and Methanobacterium sp. were further enriched and thus, performed more efficiently the methanogenesis step.