[adolph]

> Gas emits so little CO2 compared to coal

At a molecular level this doesn't make sense to me. The fundamental carbon cycle value proposition is to harvest energy released when a carbon atom (re)joins two oxygens. For the same energy, how would methane and coal produce different amounts of CO2?

That said, I can see how the oxygen reaction would be less efficient and create more byproducts (i.e. acid rain) using coal given its less refined nature. How methane would have a better energy to CO2 ratio doesn't seem to have an obvious mechanism.

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

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

Imagination, Physics, Fire & Trees - Richard Feynman (aka Trees grow from air, carbon cycle): https://www.youtube.com/watch?v=DJLMysTpwhg

[bloak]

Coal: C + O2 -> CO2

Gas: CH4 + 2O2 -> CO2 + 2H2O

I don't know off hand exactly how many joules of energy (heat) are produced per mole in each case but it's not surprising that gas gives more joules per mole of CO2: it's a bit like you're burning hydrogen at the same time.

EDIT: It's relevant that O-H bonds are stronger than C-H bonds, presumably.

[988747]

You also need to consider that H2O itself is also a greenhouse gas, much worse than CO2, although much easier to remove from atmosphere.

[nix23]

>H2O

Water...

[adolph]

Thanks, that makes some sense. I wonder how that additional bond works in the hydrolox to methalox comparison of rocket fuels.

[pfdietz]

Coal is more like CH on average.