Seems like a niche technology, useful if you're sitting on tons of scrap iron for example. I recall some proposals for using this in long-distance cargo shippi

Seems like a niche technology, useful if you're sitting on tons of scrap iron for example. I recall some proposals for using this in long-distance cargo shipping instead of very dirty (and fossil-sourced) bunker fuel, but even there synthetic diesel or methane from atmospheric CO2 + water might be the more versatile solution (and the overall mass of the iron required for say, a trans-Pacific journey is an issue). See: https://swzmaritime.nl/news/2020/02/27/why-iron-could-be-a-suitable-future-marine-fuel/ https://swzmaritime.nl/news/2020/02/27/why-iron-could-be-a-s... > "A disadvantage of iron as a fuel for ships is the relatively high specific mass of iron powder and the increase in the weight of the iron oxide that is produced during combustion. As a result, a ship will lie deeper and deeper during the voyage." They seem to have a prototype in the works c. 2030.