The resulting carbonate minerals can't be burned because they are already completely oxidized, the same way you can't burn water (with oxygen). Carbonate miner

The resulting carbonate minerals can't be burned because they are already completely oxidized, the same way you can't burn water (with oxygen). Carbonate minerals are a lower energy compound than their reactants, which is good, because it means the reaction will happen spontaneously without an energy input from us (which would probably be too large to make it economical)