Efficient methane fermentation from organic solid wastes by using bioelectrochemical system

Organic solid wastes were treated in various types of methanogenic bioelectrochemical reactors, equipped with an external electrochemical system to control electron flow and improve microbial activity. At a high organic loading rate, cathodic bioelectrochemical reactors demonstrated greater decomposition of artificial garbage slurry and higher methane production than both anodic bioelectrochemical reactors and the control reactor without electrochemical control. Higher prokaryotes and methanogens thrived on cathodic electrodes than on anodic or control electrodes since the cathodic reaction could positively control the electron flow and alter the microbial metabolism, which enabled the stabilization of methane fermentation. Furthermore, a carbon fiber fabric was attached to the working electrode in the methanogenic bioelectrochemical reactor to retain more microorganisms, and consequently enhance performance. This improved cathodic bioelectrochemical reactor displayed higher decomposition of a mixture of artificial garbage slurry and rice straw, and concomitantly increased production of methane than the control reactor. The improvement effectively enhanced the reactor performance and led to a higher ratio of methanogens to prokaryotes in the suspended fractions of the cathodic reactor compared to the control. Finally, the working of the improved reactor was investigated at a scaled-up volume of 4.0 L by using actual organic solid waste to determine its universal utility that combined electrochemical control and supporting material. The developed cathodic bioelectrochemical reactor containing carbon fiber fabric was found to achieve better decomposition of thickened sewage sludge and higher production of methane at a short hydraulic retention time than the control reactor containing carbon fiber fabric without electrochemical control. Moreover, at longer hydraulic retention times, the methanogenic reactor of stirred tank type lacking the carbon fiber fabric deteriorated faster. Thus, the universal effectiveness of the technology that combined electrochemical control and use of a modern support material has been demonstrated.