It's a cute idea but it can't work as is. It tries to do 2 things, and each is very difficult on its own. It tries to extract steel from aluminum waste, so the amount of waste is reduced, and it wants that steel to be green, so CO2 emissions are reduced. Neither one is close to being economically viable. And it's not just the energy input, it very likely is the capital cost as well.<p>Iron is produced in 2 ways: from scrap iron (i.e. recycling) or from iron ore. If produced from iron ore, the ore needs to contain about 50-60% iron to be economically viable. It goes without saying that in this context we are talking about regular smelting, using coal. That generally happens away from the mines, which is a sign that the capital cost is high; if it weren't they'd build the furnaces right next to the mines to reduce transportation cost.<p>Let's forget about hydrogen or green steel. Can you just start using the "red mud" as iron ore? Very unlikely. You'd need to either move the furnace next to the aluminum mine, or bring the red mud to the furnace. The first is not an option. The steel industry is so cutthroat with margins so low, that you need scale. Huge scale. Aluminum is produced in tiny quantities compared to iron, there's no way you'd have enough scale to justify a steel furnace next to an aluminum mining operation. Bringing the red mud to the furnace is not really an option either: you would need to at a minimum dry it out somehow to make it solid, otherwise the transportation costs balloon. But this red mud is supposedly quite toxic, it does not appear to be so straightforward to dry it out, and that would add to the processing cost too.<p>And then the hydrogen thing. Let's first focus on transitioning the regular steel making to hydrogen. This in itself appears to be an extraordinarily hard nut to crack. If we manage it, it's a huge win. We can then expand to aluminum waste cleanup if we want, after we pop some champagne. But let's stay focused on regular green steel first.