How much energy is used in the process to make powdered iron?
Offhand I don’t know, but if it’s eternally recyclable, it’s probably pretty small over time.
It’s says here that it is on par with hydrocarbons, without any release of carbon in the process.
https://www.cbc.ca/news/technology/scientists-green-fuel-metal-1.4058398
It might be useful for power plants, possibly. A replacement for coal.