In historical terms, it took about 60 milion years to form this coal layers. Humanity will burn them in few centuries.
https://en.wikipedia.org/wiki/Carboniferous
From the point of view of energy. The conversion of solar energy into coal is very inefficient, tree need energy to reproduce, only a part of plant is converted into coal, other organisms consuming plant matter, etc.
In historical terms, it took about 60 milion years to form this coal layers. Humanity will burn them in few centuries.
https://en.wikipedia.org/wiki/Carboniferous
From the point of view of energy. The conversion of solar energy into coal is very inefficient, tree need energy to reproduce, only a part of plant is converted into coal, other organisms consuming plant matter, etc.