I was just watching a video where they made the claim that the slag from steel production 100 years ago has more metal than some ores, so it's becoming worthwhile to re-mill slag.
Video games have largely misled us here. Iron ore is incredibly common, it’s not a rare resource at all. The limiting factor for steel production has historically been energy, not ore, and in the modern context the ability to produce pure oxygen for carbon reduction. Historically iron mines were put near forests for fuel, not wherever the richest ore was.
The advantage of re-using slag isn’t that it’s richer in metal, iron oxides being pretty easy to get, it’s that it would take less energy or Oxygen to finish refining.
That or slag is much lighter per lb of refined product, reducing the transit cost. Iron ores are incredibly common, but they’re also very heavy, what with them being literally rocks.
of course I can't find the original video I was watching, but since the slag is directly outside the steel mill, transit is about as low as it could get.
If you search on YouTube for "deskulling slag pot", you'll find a bunch of videos showing slag trains going maybe a couple miles from the mill to a pit to deskull?
The advantage of re-using slag isn’t that it’s richer in metal, iron oxides being pretty easy to get, it’s that it would take less energy or Oxygen to finish refining.
Recommended reading: Bret Devereaux’s blog series about iron & steel production. https://acoup.blog/2020/09/18/collections-iron-how-did-they-...