Methane Photosynthesis

[Vaktus]

One possible energy-yielding reaction in a reducing atmosphere might be the hydrogenation of multiply-bonded molecules - ideally, all the way to methane. For example, although I haven't done the maths I feel this reaction would be exothermic:

C2H2 + 3H2 = 2CH4

(a triply-bonded compound being fully hydrogenated)

This reaction goes very slowly indeed without catalysis, but enzymes do more difficult things than this.

Perhaps this reaction could be used as a reciprocal metabolism? Plants produce hydrogen and animals use that hydrogen to produce methane for the plants to use.

Also, could this reaction also be used for the muuh biosphere Drashner mentioned? Acetylene exists in Titan's atmosphere as well as hydrogen. Acetylene even exist in it's upper atmosphere, I think.