Once you factor in all the processing of certain biomass, specifically I recall a European nation, the UK perhaps, was burning wood product. Wood is significantly less energy dense than coal for instance... If your workers are driving to and from work, if you're cutting it down with two stroke chainsaws, loading it into trucks, packing it into trains... I think these factors were all removed from calculations to conclude it's "carbon neutral".
And for some reason, probably wrongly, I'd like to imagine leaving the trees up is more beneficial (even if the fuel is a byproduct of industry), but I can imagine during a tree's lifecycle there's a "peak sequestration" age/size they're maybe targeting.
