Comment by chabska
> but it also gets released again
Quite slowly. Lignin, which makes up about 30% of woody biomass, is very difficult to break down biologically. Only a few specialized bacteria and fungi have the enzymes for it.
We don't need to sequester carbon permanently, we just need to bind enough of it into soil carbon to reduce the concentration of CO2 in the atmosphere. The long residence time of carbon in the soil is sufficient for this purpose.
And not completely. That's why we have oil and gas deposits.