Table 2.

The concentration of candidate interspecies electron carriers (IECs) at which their production from CH₄ is no longer thermodynamically possible (ΔG’ = 0) at 0.16 MPa CH₄, 0.2 mM HCO⁻₃ (for H₂) or 1 mM HCO⁻₃ (of the other potential-IECs), 1 mM HS⁻, 30 °C, and a pH of 7

IEC	IEC concentration at which ∆G IEC production = 0	IEC concentration on day 4
Acetate	3.8 × 10−9 M	8.5 × 10−4, 8.6 × 10−4 M
Formate	1.0 × 10−8 M	7.3 × 10−4, 7.2 × 10−4 M
Methanol	1.8 × 10−15 M	9.3 × 10−4, 9.3 × 10−4 M
Carbon monoxide	8.4 × 10−10 kPa	4.9, 4.4 kPa
Methanethiol	8.4 × 10−12 M	9.9 × 10−4 M
Hydrogen	6.6 × 10−4 kPa	3.2 kPa