Same idea stated differently: the problem is the amount of carbon available at the planet's surface: a huge portion of that carbon will eventually end up as CO2

Same idea stated differently: the problem is the amount of carbon available at the planet's surface: a huge portion of that carbon will eventually end up as CO2, as that is the lowest energy state. Earth's biosphere allows for an equilibrium where part of that carbon will will be present as non-CO2 (i.e. biomass), but as we get more carbon to the surface, we'd have to move the equilibrium point to compensate for the added carbon, which doesn't seem to be a scalable solution. The only scalable solution is to stop bringing up more carbon to the surface :)