[hollerith]

But then you have to keep on adding iron, which might be costlier than hydrogen. And you have to keep on removing iron oxide.

[kragen]

well, adding iron and removing iron oxide is what electrowinning iron does, but i think i added that part of my comment after you made yours. but you can still add iron and remove iron oxide with the hydrogen smelting furnace the ethz researchers devised if you like that better