A novel 2d-on/3d-off power stimulation enhances sludge methane production in an MEC-AD system

Microbial electrolysis cell-assisted anaerobic digestion (MEC-AD) has emerged as a promising strategy to enhance anaerobic digestion efficiency. However, recent studies reveal a paradoxical trend: systems operating under continuous power supply exhibit reduced methanogenic performance and elevated energy consumption compared to those employing intermittent voltage application, suggesting that prolonged energization may inhibit methanogenesis. To address this, we proposed a novel intermittent power supply mode with extended deactivation periods (2 days on, 3 days off) to investigate its impact on methane production and system sustainability. Remarkably, the intermittent mode achieved a 14.9 % increase in methane yield and an energy efficiency of 235.5 % relative to continuous operation. Furthermore, this approach significantly enhanced sludge hydrolysis and acidogenesis, enriching the availability of bioavailable organics for methanogenic pathways. Concurrently, it improved the systems electrochemical activity (e.g., higher electron transfer rates) and enzymatic function, and fostered a substantial enrichment of electroactive bacteria ( Geobacter spp.) in the anode biofilm, which was a key driver of exoelectrogenic activity. These findings demonstrate that intermittent energization with prolonged off-phases not only optimizes methane production but also advances energy sustainability, offering a viable alternative to conventional continuous power supply in MEC-AD systems. • A 14.9 % increase in methane yield is achieved by the 2d-on and 3d-off power supply. • WAS hydrolysis and acidogenesis is enhanced by the long-intermittent power supply. • The sludge and anode electron transfer is activated by intermittent power supply. • 2d-on and 3d-off mode enables biogas upgrades for PF + CA assisted fermentation systems.