That's current proven reserves, not theoretical reserves, no? Because as we've seen with oil, the higher the price goes, the more we seem to find.

> but you need the energy to renew it in the first place.

So am I hearing you could create the iron-fuel someplace with excess energy and then ship this stored energy someplace that wants to burn it?

And while Iron loses out to energy density per kilogram, it wins on kilogram per cubic centimeter :D (your math is much appreciated btw)