Suppression of methanogenesis in cellulose-fed microbial fuel cells in relation to performance, metabolite formation, and microbial population

► Methanogenesis was active in cellulose-fed MFCs but declined on prolonged operation. ► Coulombic efficiencies increased as methanogenesis became undetectable. ► Acetic acid was the main metabolite of cellulose degradation in MFCs. ► Bacterial and archaeal diversities decreased over the 90 day operation. ► Firmicutes, Methanoculleus, and Methanobrevibacter were the most dominant.