Pulsed CO2 feeding promotes methane yield in anaerobic digester by diverting acidogenic pathways

•Effects of CO2 injection strategies on methane yield are explored.•Pulsed CO2 feeding enhanced methane yield by 19.3–27.1%.•About 35–59% of injected CO2 was absorbed and in situ utilized.•CO2 injection reinforced acetate and lactate production and weakened propionate yield.•Improved methane yield attributed to diverted acidogenic pathway.