\[\begin{align} & \text{HCOO}^{-} + \text{H}^{+} \longleftrightarrow 0.25 \ \text{CH}_{4} + 0.75 \ \text{CO}_{2} + 0.5 \ \text{H}_{2} \text{O} \\ & \text{H}_{2} + 0.25 \ \text{CO}_{2} \longleftrightar...HCOO−+H+⟷0.25CH4+0.75CO2+0.5H2OH2+0.25CO2⟷0.25CH4+0.5H2OThis pathway is known as carbon dioxide reduction or hydrogenotrophic methanogenesis and most methanogens are thought to be capable of it.