Iron mined from ore is iron oxide. Much energy for heat from carbon sources convert this to iron during the smelting process. Iron in this state is an energy source to be burned and iron can burn. It is then iron oxide again. To convert it to iron again requires more energy input as original to make it iron which will burn. The greenies do not know much about thermodynamics and they think enthalpy and entropy are a new drug or sexual position, they are idiots. Unless all energy to do this from the original processing is from green energy this is a carbon positive and not carbon negative process.
Well, now we “just” need an efficient solar furnace for smelting rust into iron.