We'd only need a large amount of energy if we want to turn it back into a high-energy compound like oil or coal. The method described in the article has CO2 tur

We'd only need a large amount of energy if we want to turn it back into a high-energy compound like oil or coal. The method described in the article has CO2 turning into calcium carbonate, which does not need an energy input (in fact, it releases energy in the form of heat)