Operation of a cylindrical bioelectrochemical reactor containing carbon fiber fabric for efficient methane fermentation from thickened sewage sludge

► A bioelectrochemical reactor containing carbon fiber fabric was constructed. ► Flexibility of the technology was investigated using thickened sewage sludge. ► Newly designed reactor maintained stable biogas production from actual waste. ► Composition and diversity of microbiota in this reactor were clarified. A bioelectrochemical reactor (BER) containing carbon fiber fabric (CFF) (BER+CFF) enabled efficient methane fermentation from thickened sewage sludge. A cylindrical BER+CFF was proposed and scaled-up to a volume of 4.0-L. Thickened sewage sludge was treated using three types of methanogenic reactors. The working electrode potential in the BER+CFF was regulated at −0.8V (vs. Ag/AgCl). BER+CFF showed gas production of 3.57LL−1day−1 at a hydraulic retention time (HRT) of 4.0days; however, non-BER+CFF showed a lower gas production rate (0.83LL−1day−1) at this HRT, suggesting positive effects of electrochemical regulation. A stirred tank reactor (without CFF) deteriorated at an HRT of 10days, suggesting positive effects of CFF. 16S rRNA gene analysis showed that the BER+CFF included 3 kinds of hydrogenotrophic methanogens and 1 aceticlastic methanogen. These results demonstrate the effectiveness of the BER+CFF for scale-up and flexibility of this technology.