Aerobic methane production

[2][6][7] Naturally occurring methane is mainly produced by the process of methanogenesis, a form of anaerobic respiration used by microorganisms as an energy source.

[1] Methane may also be produced under aerobic conditions in near-surface ocean water, a process which likely involves the degradation of methylphosphonate.

[9] In 2005, Frankenberg et al. published the findings of a global methane distribution study in which they used space-borne near-infrared absorption spectroscopy.

[10] These findings prompted Keppler et al. to conduct their study to investigate the possibility of methane formation by plant material.

They theorized that "the structural component pectin plays a prominent role in the in situ formation of CH4 in plants"[1] but were unable to identify a chemical mechanism for this CH4 production.

[4] A follow-up study by Keppler et al. reconfirmed their earlier findings and found "unambiguous isotope evidence that methoxyl groups of pectin can act as a source of atmospheric CH4 under aerobic conditions",[3] but again failed to identify the chemical mechanism.

Keppler et al.. observed that the release of CH4 was "very temperature sensitive—concentrations approximately doubled with every 10 °C increase over the range 30–70 °C suggesting a non-enzymic rather than an enzyme-mediated process".

[1] They also remarked that "emission rates were found to increase dramatically, by a factor of 3–5 (up to 870 ng per g (dry weight) h−1), when chambers were exposed to natural sunlight".

[2] A number of follow-up publications presented conflicting data, generating significant uncertainty in the role of terrestrial plants to the global methane budget.

[6] Supersaturation of methane in oxygenated, near-surface water in oceans, lakes and rivers is a phenomenon which has been widely observed, but which is still poorly understood.

In 2022, Perez-Coronel & Beman analyzed methane production in fresh water and found an association with "(bacterio)chlorophyll metabolism and photosynthesis,[25] Keppler and colleagues identified a mechanism through which reactive oxygen species result in the production of methane by potentially organism utilizing oxygen.