There is only so much biomass we can extract from the biosphere without endangering it. It is limited to the amount what grows naturally. Actually, it is less,

There is only so much biomass we can extract from the biosphere without endangering it. It is limited to the amount what grows naturally. Actually, it is less, as the decaying biomass also plays an important role. But yes, if we could extract the carbon from the cycle, it would be even better and truly CO2-negative. We should bury wood underground where it is not decaying for example.