The carbon for the methane produced during serpentinization comes from the CO2 pool of the mantle, right? I'd say this is a pretty endless source, at least on the timescales of Homo sapiens (or mammals, or Metazoa...). So yes, it should qualify as 'renewable'.

As to me, the term 'juvenile' suits better. Plus, to apply adjective 'fossil' to seeping methane is the same to mention 'fossil' groundwater ))

Yes, of course, Alexander, it's primordial, just like stardust...The climatic discussion about fossilized hydrocarbons and 'renewable energy' and CO2 in the ocean and atmosphere, is for political purposes only. In the real, Natural world, most substances come from the mantle, and were accreted into Earth about 4.5 billion years ago.

If this is methane produced from serpentinisation of mantle rocks ... that still leaves the question of where the carbon came from. If it's CO2 present in the mantle from the construction of the Earth (plus or minus a Giant Impact or two), then you could safely call it primordial. And you'd expect it to have a stable isotope composition similar to a chondrite meteorite. BUT, if the CO2 source is recycled sedimentary carbon from an ancient subduction event, then there is a high chance of it having started with a biogenic isotopic signature, even if it's last major chemical events were not isotopically selective. So measuring the isotopic composition of the seeps wouldn't necessarily tell you the answer to the primordial/ recycled question. Steffen Kiel has assumed the answer to what is really an open question.

From a climatic effects point of view, it really doesn't matter if the carbon is from squished dinosaurs (Sinclair Oil co adverts in the '30s, I think), or methane derived from carbon fixed into a Carboniferous coal swamp 300 million years ago (coal bed methane), or from Miocene sediments off the Norwegian continental shelf. They all put carbon into the atmosphere, and are thus indistinguishable in a climatic effect from the most un-renewable of fossil fuels. Strictly, you could dig diamonds out of a 4.5 billion year old chunk of nickel-iron meteorite and burn them - totally inorganic carbon, never been near a living cell - and as far as climatic effects are concerned, they're still a fossil fuel that produces atmospheric carbon dioxide. It's a bit sloppy to say "fossil fuel" when you mean "a fuel that releases carbon dioxide to the atmosphere", but that is the popular parlance.

If you want to call this material "renewable", perhaps it would be good to work out how it re-cycles into it's original form on a Homo-relevant time scale (say, 100,000 years, like any other atmospheric carbon).

Aidan, while analyzing different carbon sources don't forget about the Archean so-called gray gneisses enriched with graphite that compose vast areas of the continental crust. Plus add HC-conatining fluid inclusions of igneous rocks, alkaline ones in particular.

Martin, if something is seen as renewable or fossil depends upon the balance between the emerging rates or regeneration rates of natural resources and the corresponding human exploitation rates. The distinction of both categories thus follows not epistemic but practical reasons. Regeneration rates of conventional and still emerging (!) natural gas are relatively low w.r.t. its mining and human consumption. It is therefore classified as "fossil". Solar energy in contrast is seen as renewable, which is currently true - but it's emanation is not endless in astronomic timescales ...

Moreover; the distinction between boitic and aboitic origins of matter doesn't help here. Recall that uranium is found as fossil but abiotic ore.

I hope, that helps a bit.

I haven't anything to add from a technical standpoint since the previous answers have addressed many or all of the various technical and semantic parsings that I could think of to your very interesting question.  In biology they seem to have exceptions to every rule.  Perhaps you've simply found a geoscience equivalent.

Thanks a lot, for enlightening this issue! It's pretty complicated, I must say.

Hazarding to simplify the concept of 'fossil' versus 'renewable' origin, I would venture that any carbon from a re-cycling source is renewable. Then it is a question of personal or custom view to decide what is deemed acceptable as th duration of the cycle: days, years, centuries, millenniums, hundreds of millenniums, millions millenniums ... It is up to you to set the cursor.

I hope that helps clarify the concept.

Expulsion of hydrocarbons from sedimentary source rocks to form commercial accumulation of hydrocarbons is scientific but this do nor scientifically prove the biogenic origin of hydrocarbons . pls observe the following paper.

http://www.principia- scientific.org/the-true- origin-of-hydrocarbons.html

Thanks Suresh, but I have trouble opening this site

Ok, I have managed to use this link: www.principia-Scientific.org/the-true-origin-of-hydrocarbons.html

Where they have this very true statement: "Without doubt, sedimentary rocks that have been formed with no involvement of these abiotic hydrocarbons are not suitable to form commercial hydrocarbons deposits and thereby lead to dry holes. So abiotic sources are the major contributor in the commercial accumulations of hydrocarbons. Hence a well-balanced theory is today’s major requirement which will help future hydrocarbon exploration efficiently."

I totally agree, - we need a new conceptual model or theory for the hydrocarbons that fill commercial oil and gas fields. I personally know that some groups of scientists are very near to knowing how it all works. The 'Secret' is the very important world-wide geological process of serpentinization, coupled with understanding how the mantle fluids behave. However, in the mean time (i.e., before we get a well documented theory and model for this) we should start treating natural oil and gas as a renewable energy, especially as we do not know of any oil and gas field that has been totally depleted (emptied) for oil and gas, even though numerous fields have been abandoned on the grounds of commercially being too challenging.