. 2008 Feb 29;74(8):2424–2432. doi: 10.1128/AEM.02341-07

TABLE 1.

Microbial process in Indiana coal beds and associated free energy changes

Reaction no.	Microbial process	Chemical reaction	ΔG°_P,_T (kJ)^a	ΔG (kJ)^a
1	H₂-utilizing methanogenesis	HCO₃⁻ + 4H_2,aq + H⁺ → CH₄ + 3H₂O	−230.2	−19.8
2	Acetoclastic methanogenesis	CH₃COO⁻ + H₂O → CH_4,aq + HCO₃⁻	−14.7	−4.8
3	Homoacetogenesis	2HCO₃⁻ + 4H_2,aq + H⁺ → CH₃COO⁻ + 4H₂O	−215.6	−15.1

ΔG°_P,_T is a calculated reference state at in situ temperature and pressure conditions (10.5 atm, 17°C) with all reactants and products at an activity of 1.0. ΔG values are derived from ΔG°_P,_T but modified for in situ conditions based on the following average measured concentrations at three wells (INS-P11, INS-P6, and INS-P8): H⁺, 10⁻⁸ M; H_2,aq, 3.76 × 10⁻⁸ M; CH₃COO⁻, 4.3 × 10⁻⁶ M; CH_4,aq, 1.5 × 10⁻² M; and HCO₃⁻, 1.7 × 10⁻² M. All free energy changes represent the values for the reactions as written.