Conventional steel mills are energy intensive and they depend on fossil fuels, which makes them one of the largest contributors to industrial CO2 emissions (i.e. 7-9% of global emissions).
Furnaces conventionally use coke or hydrogen derived from natural gas to reduce iron ore to iron. Alternatively green hydrogen produced by a large scale electrolyser can be used as the reducing agent, in order to decrease the CO2 emissions of steel production.
In addition, the oxygen by-product from the electrolyser can be used to increase furnace efficiency and so further reduce CO2 emissions.