Comment Lignin (Score 2) 95
It doesn't decay correctly with oxygen inside of it, and there is fungi that eats dead wood. Which results in methane release, among other things.
One would image you wouldn't need to go all the way with turning it into charcoal, but you would need to go far enough to not come back to the mine turning into one gigantic bioreactor for fungi and bacteria.
The argument being made is often that there was a very long period between wood evolving, to the period where wood could be digested by anything. Meaning there was a 60 million year period where all wood would just fall down, where erosion and flood would bury it, and keep tumbling down, and eventually turn to fossile fuel due heat and pressure.
As per wikipedia:
"One theory suggested that about 360 million years ago, some plants evolved the ability to produce lignin, a complex polymer that made their cellulose stems much harder and more woody. The ability to produce lignin led to the evolution of the first trees. But bacteria and fungi did not immediately evolve the ability to decompose lignin, so the wood did not fully decay but became buried under sediment, eventually turning into coal. About 300 million years ago, mushrooms and other fungi developed this ability, ending the main coal-formation period of earth's history."
"The conversion of dead vegetation into coal is called coalification. At various times in the geologic past, the Earth had dense forests[20] in low-lying areas. In these wetlands, the process of coalification began when dead plant matter was protected from oxidation, usually by mud or acidic water, and was converted into peat. "