[Qwertious]

IIRC steelmakers use roughly 2 parts iron to 1 part coke, which means coke would be 33% of the weight, but steel is only 1% carbon - that's an efficiency of only 3%. Metallurgical coal is used primarily because it burns hot enough to efficiently melt iron.

[throwup238]

> Metallurgical coal is used primarily because it burns hot enough to efficiently melt iron.

That’s the historical reason, but now it's used because carbon is a reducing agent that binds to oxygen, preventing it from oxidizing the iron back into iron oxide and because the coke is used as a permeable membrane to let the resulting gasses escape.

If it was just a matter of heat, there's any number of cleaner fuels steelmakers could use but they can't because the coal serves an important role in the chemistry of blast furnaces.