The CO2 is pulled out of the air by plants, during gasification you convert some of this biomass into CO2, water and energy, by burning the syngas; and some you

The CO2 is pulled out of the air by plants, during gasification you convert some of this biomass into CO2, water and energy, by burning the syngas; and some you leave behind as biochar. This biochar gets buried into the soil, creating the equilibrium deficit that you're looking for. Biochar is also estimated to be stable for some 10,000 years...thus its pretty much the only reversal to mining coal that we have. Not using the biomass results in methane, which is estimated to be 86 times worse (as a greenhouse gas compared to CO2 alone) for our atmosphere than CO2 alone.