Since the CO2 is an early fraction as you cool air to liquid, it is essentially free, since it has commercial value it is captured instead of vented. The power would be consumed anyways.
This is not much greater than the energy required to haul and use traditional blasting media, but because it is evaporated after use, the energy required to collect and transport the used grit is largely eliminated.
Sure, but until we figure out how to build infrastructure that does not need to be maintained, then something has to be done. Perhaps we can give 100 inmates a wire brush??? but then you'd have to haul them to the job site, erecrt scaffolds, and they'd need more food because they were working harder, and that food production would generate more CO2...