Enhanced methane production from Taihu Lake blue algae by anaerobic co-digestion with corn straw in continuous feed digesters

► Methane production from Taihu algae succeeded with continuous reactors. ► Ammonia from algae decay inhibited mainly acetate and propionate degradation. ► Co-digestion of algae with corn straw enhanced methane productivity and VS removal. ► Optimal C/N ratio of 20:1 (g/g) was found. ► Rate limiting step is not hydrolysis but acetate and propionate degradation. Anaerobic digestion of Taihu blue algae was tested in laboratory scale, continuous feed digesters (hydraulic retention time 10days) at 35°C and various organic loading rates (OLR). The methane production and biomass digestion performed well at OLR below 4.00gVSL−1d−1 but deteriorated as OLR increased due to the increased ammonia concentration, causing inhibition mainly to acetate and propionate degradation. Supplementing corn straw as co-feedstock significantly improved the digestion performance. The optimal C/N ratio for the co-digestion was 20:1 at OLR of 6.00gVSL−1d−1. Methane yield of 234mL CH4 gVS−1 and methane productivity of 1404mL CH4 L−1d−1 were achieved with solid removal of 63%. Compared with the algae alone, the methane productivity was increased by 46% with less accumulation of ammonia and fatty acids. The reactor rate-limiting step was acetate and propionate degradation.