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Origin of Methane

Methane molecule

Q: As I understand it, methane is normally associated with organic processes and decompostion, and has only recently been synthesised, under pretty extreme conditions:

What I would like to ask you is 'Is there any 100% evidence that methane is or has been produced by purely physical methods in the natural world?' Or, to put in another way, 'What evidence is there that all the methane in the world was not produced by biological processes?'

I do appreciate that evidence is rarely watertight, and that there is always an element of doubt in these things, but if I were to claim that 'It seems that all the methane in the world has come from biological processes', what evidence might someone legitimately offer to prove me absolutely wrong?

From Mr Chas Griffin (June 2010)

Reply by Dr Colin Campbell

My understanding that indeed virtually all methane is of organic origins. You are right, that sources such as mud volcanoes and cathrates are likely to be of conventional organic origin. Coalbed methane is held in the crystal structure of coal, but otherwise it is held in the pore space of rocks in the same way as is oil. Methane is also a major component of Natural Gas although it may contain other hydrocarbon gases such as pentane. Mud volcanoes which I have observed in Trinidad and Colombia are simply seepages of gas from deeper reservoirs which build up a mound of mud and sometimes explode and catch fire. Cathrates are ice-like crystals of methane that are found in cold conditions in deepwater or polar region, again mainly resulting from normal seepages. They occur disseminated in thin laminae are not concentrated enough to be exploited commercially. They can also occur in pipelines and clog them under cold conditions. Methane may also be formed in normal volcanic activity by the impact of hot lavas on the organic content of the sedimentary rocks through which they pass”.

Professor Hilary Downes from the department of Earth Sciences and Planetary Science at Birkbeck College, adds:

“Most of the methane in the Earth is biogenic, but some can form by inorganic reactions which can occur in hydrothermal vents on the ocean floor. Methane has been observed in the atmosphere of Mars, which is almost certainly of abiogenic origin – unless there is life on Mars!”