Simultaneous enhancement of methane production and methane content in biogas from waste activated sludge and perennial ryegrass anaerobic co-digestion: The effects of pH and C/N ratio

It is necessary to find an appropriate strategy to simultaneously enhance the methane production and methane content in biogas from waste activated sludge ( WAS) and grass co-digestion. In this study an efficient strategy, i. e., adjusting the initial pH 12 and C/N ratio 17/1, for simultaneous enhancement of methane production and methane content in biogas from WAS and perennial ryegrass co-digestion was reported. Experimental results indicated that the maximal methane production was 310 mL/gVS(add) at the optimum conditions after 30-d anaerobic digestion, which was, respectively, about 1.5- and 3.8-fold of the sole WAS and sole perennial ryegrass anaerobic digestion. Meanwhile, the methane content in biogas was about 74%, which was much higher than that of sole WAS ( 64%) or sole perennial ryegrass ( 54%) anaerobic digestion. (C) 2016 Elsevier Ltd. All rights reserved.