Release of methane from aerobic soil: an indication of a novel chemical natural process?

Methane (CH(4)) formation under aerobic conditions has been intensely debated, especially since the discovery of CH(4) generation by both dried plant material and living plants. In this study we test the hypothesis that non-microbial CH(4) formation also occurs in soils. All lyophilised soil samples investigated under aerobic conditions released CH(4) at temperatures ranging from 30 to 70°C exceeding that allowing normal enzymatic activity to proceed. No emissions were observed for single mineral soil components such as quartz sand, clay mineral and iron oxide. Methane release rates from the soils investigated were found to increase both with increasing temperature and higher organic carbon content. Addition of water to dried soils increased CH(4) release rates up to 8-fold those observed with the dried material. Our results suggest the existence of a chemical process in soils that produces CH(4) under aerobic conditions, a finding which has not been hitherto reported.