I was quite surprised to learn that apparently for every ton of steel produced, something like 1.9 tons of CO2 is produced in a conventional steelmaking process, which was counter intuitive to me because isn't some of the carbon supposed to end up as a part of the steel? I guess a lot of it's just from heating the steel to form the reaction. Looking around it seems like electric arc heated plants produce something like half that amount of CO2 which could be improved by using renewable electricity sources. Coking coal would still be necessary in this case.

Mind you, I feel like steel production is still less bad than say fuel consumption for transport as at least the steel production ends up with some highly durable, useful object at the end of the process. Burned diesel for transport on the other hand is just purely lost to the environment.