Methane production and microbial community acclimation of five manure inocula during psychrophilic anaerobic digestion of swine manure

For small-scale farms, the development of rustic and cheap psychrophilic anaerobic digestion systems appears as an opportunity to treat manure, mitigate gaseous emissions and promote decentralized renewable energy production. However, the development of such processes is limited by our understanding of their start-up. In this research, we tested the ability of one mesophilic digestate and four different manure to be used as inoculum for the start-up of psychrophilic anaerobic digestion of swine slurry at 13 °C. The most efficient inoculum appeared to be a swine manure that had been stored for 2 months in a pit. After 9 months of acclimation, the corresponding reactor produced a maximum methane yield of 42L of CH4/kg Volatile Solidesubstrate/day and a CH4 volume of 125L of CH4/kg-Chemical Oxygen Demandadded. The maximum methane production expressed at 13 °C was between 55% and 68% of that obtained at 37 °C. Monitoring of the microbial community dynamics by high throughput 16S rDNA sequencing showed the smooth adaptation of manure microbial species, underlining the transient dominance of the acetogen syntroph candidatus Cloacimonas during acclimation and the enrichment in the Methanosaeta and Methanosarcina methanogens for an efficient methane production. •Five different manure were acclimated to anaerobic digestion at 13 °C.•Swine manure stored for 2 months was the most efficient inoculum.•A maximum methane yield of 42 L CH4/kg VSsubstrate·day was obtained.•The maximum methane production at 13 °C was 55%–68% that obtained at 37 °C.•Efficient methane production required acetoclastic methanogens.