well, if you convert it all to biochar (say with a 50% volume fudge factor to account for non-carbon components and packing density), you just have to stack an area the size of pennsylvania with 1 meter of biochar each year to zero emissions.
And the carbon cost of the energy it takes to convert it all to biochar?
The energy and carbon come from burning off the volatile organics from the wood. It impacts the amount of carbon sequestered but it's still a net positive.