Enhanced straw fermentation process based on microbial electrolysis cell coupled anaerobic digestion

Abstract Low quality and yield of methane severely hindered the industrial application of straw biogas fermentation and there has been no effective solution found so far. In this study, a novel method has been developed to improve the quality and yield of methane during biogas fermentation. We coupled microbial electrolysis cell (MEC) with normal anaerobic fermentation to enhance the yield and purity of methane. This novel fermentation process achieved the methane purity of more than 85%, which was critically higher than those of previously published reports. With the stimulation from microorganisms and electric current, the degradation of fiber has been greatly enhanced. The MEC system significantly improves the yield and purity of biogas, bringing a new path to synthesize the methane by the carbon dioxide and hydrogen ions in solution under the electron. Electrochemical index analysis showed the extra methane synthesis which was mainly led by the external circuit electron transfer. The result of the gas chromatograph and solid degradation rate showed that the carbon source of extra methane was CO2 produced in normal fermentation and extra volatile solid degradation. These results show that MEC significantly enhanced the quality and yield of methane in a straw fermentation process, giving insights for normal anaerobic fermentation.