Table 1.

Reactions and free energy yields of the carbon dioxide reduction pathway

No.	Reaction	(kJ/mol)
1	4H2 → 8e− + 8H+
2	CO2 + 8e− + 8H+ → CH4 + 2H2O
3 (Sum of no. 1 and 2)	CO2 + 4H2 → CH4 + 2H2O	−131
4	4CO + 4H2O → 8e− + 8H+ + 4CO2
5	CO2 + 8e− + 8H+ → CH4 + 2H2O
6 (Sum of no. 4 and 5)	4CO + 2H2O → CH4 + 3CO2	−210.4
7	4CO + 4H2O → 4H2 + 4CO2
8	4H2 → 8e− + 8H+
9	CO2 + 8e− + 8H+ → CH4 + 2H2O
10 (Sum of no. 7, 8, and 9)	4CO + 2H2O → CH4 + 3CO2	−210.4
11	2(CH3)2S + 3H2O → 3CH4 + HCO3− + 2H2S + H+	−49.4