They need to initially (and then repeatedly) heat the limestone in order to release and capture the CO2 in it. This way they get some really CO2 hungry sand tha

They need to initially (and then repeatedly) heat the limestone in order to release and capture the CO2 in it. This way they get some really CO2 hungry sand that binds it from the air. I’d expect it’s the rock baking part that takes the most energy.