You're completely missing the point that you put CO2 into the ground, not unoxidized carbon. So you're ahead by the enthalphy content of those carbon-oxygen bon

You're completely missing the point that you put CO2 into the ground, not unoxidized carbon. So you're ahead by the enthalphy content of those carbon-oxygen bonds. Obviously you need some energy to concentrate the CO2 out of a waste stream and pump it miles below, but that's comparatively trivial.