BACKGROUND: Biogas can be upgraded to biomethane, which can be used as vehicle fuel and natural gas substitute. Bioelectrochemical biogas upgrade is an innovative alternative to energy-consuming physicochemical processes and bio-upgrade methods which require H 2 supply. Bioelectrochemical biogas upgrade is conducted by methanogenic microorganisms that convert CO 2 into CH 4 , in the biocathode of a bioelectrochemical system (BES), using electric current as energy source. The aim of the present work was to study the efficiency of an H-type BES in the conversion of CO 2 into CH 4 , by applying different potentials at the electromethanogenic biocathode.RESULTS: The H-type BES was operated in a three-electrode configuration (working: graphite rod; counter: Pt/Ti; reference: Ag/AgCl) with a potentiostat, which set the biocathode's potential initially at −0.7 V versus a standard hydrogen electrode (SHE) and monitored the current demand. Based on cyclic voltammetry runs, a highly electroactive methanogenic biocathode was developed in a short time. The methane production rate (MPR) at a cathode potential of −0.7 V versus SHE was 31.1 mmol m −2 d −1 , with an electron capture efficiency of 77.6%. The efficiency of the BES was reduced by applying a potential of −0.5 V versus SHE at the biocathode, resulting in negligible CH 4 production. The BES achieved its maximum performance at a potential of −0.9 V versus SHE with a MPR of 53.8 mmol m −2 d −1 and an electron capture efficiency of 86%. The CO 2 consumption rate achieved was 0.8 mmol d −1 .CONCLUSIONS: The H-type BES achieved an effective biolectrochemically driven methane production, while the biocathode electroactive behavior was evaluated during the whole operation of the system.