Abiotic Methane on Earth

The term 'ultramafic' describes rocks that are rich in magnesium and iron.

https://en.wikipedia.org/wiki/Ultramafic_rock

Magnesium-rich rock interacting with water produce MgO (Magnesium Oxide) and free hydrogen.

Mg + H2O -> MgO + H2

The hydrogen, in turn, will react with the CO2 to produce methane and water.

4H2 + CO2 -> CH4 + 2H2O

The latter reaction is also known as the Sabatier reaction, and was discovered in the late 1800s.

"Raney Nickel" is a catalyst that can promote the formation of methane from CO2 and Hydrogen.

https://en.wikipedia.org/wiki/Raney_nickel

Mafic and ultramafic rocks often contain nickel, and/or more specifically nickel aluminum alloys.

The first significance of this is 'methane will always be with us'. This is not a 'fossil' fuel, in that methane is continually regenerating via various processes.

https://www.sciencedaily.com/releases/2009/07/090726150843.htm

https://courses.seas.harvard.edu/climate/eli/Courses/EPS281r/Sources/Origin-of-oil/The Origin of Methane (and Oil) in the Crust of the Earth.pdf

Biotic methane will have elevated levels of Carbon-14, since plant matter takes this up from the atmosphere. One area assumed to be a particularly rich source of abiotic methane are deep sea trenches where mantle rocks are exposed to seawater.

The second significance is that we can produce as much 'natural gas' as we want via solar and wind generated electricity. Hydrogen is so reactive that it easily practically any metallic object it comes in contact with, forming metal hydrides.

https://en.wikipedia.org/wiki/Nickel_hydride

https://en.wikipedia.org/wiki/Iron_hydride

Methane is so stable in comparison that it resists reaction unless some stimulus, such as light or heat, is added in the presence of reactants (oxygen, chlorine, etc.).

To be continued another day. I started reading up on some of this stuff, which is extensive. The 'Harvard Course' above runs 27 pages.

 

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Mg + H2O -> MgO + H2 ????? where are you finding Mg in the metallic form in nature? It does not exist even in Magnesium-rich rock .

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7 hours ago, notsonice said:

Mg + H2O -> MgO + H2 ????? where are you finding Mg in the metallic form in nature? It does not exist even in Magnesium-rich rock .

Ultramafic rocks are 'rich' in magnesium, which means more specifically 'poor' in silicon. Magnesium is in a mineral form. Keyword search 'olivine'. The mineral chemistry is Mg2SiO4.

https://en.wikipedia.org/wiki/Olivine

'Serpentization' means that water reacting with Mg2Si04 turns the mineral into Serpentine.

https://en.wikipedia.org/wiki/Serpentinite

One reaction described above is 18Mg2SiO4 + 6Fe2SiO4 + 26H2O + CO2 → 12Mg3Si2O5(OH)4 + 4Fe3O4 + CH4

Olivine becomes a 'hydroxide' with one atom of the H2O released for another reaction and the remaining OH being incorporated in the rock.

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