[m12k]

Doesn't rotting, or being eaten by microbes or termites that eventually get eaten or die and rot eventually lead to the release of the stored carbon?

AFAIK coal is composed mostly of trees that fell back before microbes evolved that could eat through their cellulose walls, and have had millennia of underground compression to further increase their stability - basically that process isn't available naturally to trees that fall today.

[otterley]

It takes roughly twice as long for a tree to decompose as it does to grow; and trees live a lot longer than that! So over time, the net sequestration should be positive.