[alephnil]

> You need carbon (coal) to make steel from iron.

Carbon in form of coal is currently used for three purposes in steel production:

1) Heat up the ore to high temperatures

2) Reduce iron oxide to iron.

3) Steel is an alloy of iron and carbon.

Only for the third of these carbon is essential, and that requires some tens of kilos carbon per ton of steel as opposed to more than 2 tons carbon per ton of steel. The two first ones can be replaced by electrical heating and hydrogen respectively. There are currently being built some factories in northern Sweden for doing this, using hydrogen produced by hydropower. Without sufficient tax on carbon or customers willing to pay the extra for "green steel", it is not cost competitive for now.