[fy20]

At the time coal deposits formed the bacteria that broke down lingin and cellulose hadn't yet evolved, so just burying trees wouldn't work today as they would decay. You could probably burn the wood to produce charcoal (burning it in a low oxygen environment), and the bury that, but just cutting down a forest and burying it won't work.

[ars]

In a low oxygen, low water environment it would work fine.

For example an old coal mine and then seal it.

Old coal mines are too dangerous for humans to enter so you need some kind of robotics to load them up with trees and other biomatter to bury.

[Method-X]

This would never scale.