TABLE 1.

Gibbs free energies, enthalpies, and entropies of reactions involved in methanogenesis, homoacetogenesis, and propionate degradation under standard conditions^a

Reaction	kJ/reaction
	ΔG0	ΔH0	ΔS0
Methane production
4 H2 (g) + CO2 (g) → CH4 (g) + 2 H2O (l)	−130.7	−252.9	−0.41
CH3COO− (aq) + H+ (aq) → CH4 (g) + CO2 (g)	−75.7	+17.7	+0.314
Homoacetogenesis
4 H2 (g) + 2 CO2 (g) → CH3COO− (aq) + H+ (aq) + 2 H2O (l)	−55.1	−270.6	−0.723
C6H12O6 (aq) → 3 CH3COO− (aq) + 3 H+ (aq)	−197.5	−185.3	+0.041

^aThat is, 1 M, 10⁵ Pa, 298.14°K.