Insights into biomethane production and microbial community succession during semi-continuous anaerobic digestion of waste cooking oil under different organic loading rates

High content of lipids in food waste could restrict digestion rate and give rise to the accumulation of long chain fatty acids in anaerobic digester. In the present study, using waste cooking oil skimmed from food waste as the sole carbon source, the effect of organic loading rate (OLR) on the methane production and microbial community dynamics were well investigated. Results showed that stable biomethane production was obtained at an organic loading rate of 0.5–1.5 g VS L(−1) days(−1). The specific biogas/methane yield values at OLR of 1.0 were 1.44 ± 0.15 and 0.98 ± 0.11 L g VS(−1), respectively. The amplicon pyrosequencing revealed the distinct microbial succession in waste cooking oil AD reactors. Acetoclastic methanogens belonging to the genus Methanosaeta were the most dominant archaea, while the genera Syntrophomona, Anaerovibrio and Synergistaceae were the most common bacteria during AD process. Furthermore, redundancy analysis indicated that OLR showed more significant effect on the bacterial communities than that of archaeal communities. Additionally, whether the OLR of lipids increased had slight influence on the acetate fermentation pathway.