Methoxyl stable isotopic constraints on the origins and limits of coal-bed methane

Abstract

Coaling in the deep Despite our current reliance on fossil carbon for energy, the biogeochemical reactions that produce coal and natural gas aren’t entirely understood. Lloyd et al . tested the chemistry and isotope composition in samples ranging from wood to hard, mature coal (see the Perspective by Keppler). Methyoxyl groups in this organic material, which are a potential source of methane, declined with maturity, whereas the carbon-13 fraction increased gradually. The most plausible explanation for this observed pattern is biological demethylation under substrate-limited conditions. These results help us understand the processes that form coal and natural gas on geologic time scales. —MAF