I believe "second most prevalent liquid" but don't know how it's said to be regenerated.

Maybe it's a lot easier if you think in terms of elements? It's carbon, we're carbon. Air's got carbon. Rocks have carbon. It's just an arrangement of the same old C's...

Biomass decomposition seemed likely enough a source to me that I didn't ever look into it. If you're going to store energy in a molecule's shape, that energy has to come from somewhere and an animal body is like an energy sponge/magnet. Hot volcanic rocks could also donate a bunch of energy.

I don't know. Cool idea though.