Heavy industry (steel, cement and chemicals)

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The sectors where the emissions are not mainly a fuel choice. Iron and steel and cement each account for something in the region of seven to eight per cent of global carbon dioxide emissions and bulk chemicals for several per cent more, but the composition of those emissions differs from power generation in ways that determine what can be done. Primary steelmaking by the blast-furnace and basic-oxygen route uses coke twice — as the energy source and as the chemical reducing agent that strips oxygen from iron ore — so carbon dioxide is a stoichiometric product of the reaction, not merely a combustion by-product, at roughly one and a half to two tonnes per tonne of crude steel. Cement emits carbon dioxide from the limestone itself during calcination, before any fuel is considered. Both processes also need process heat at temperatures a resistance heater does not comfortably reach at industrial scale: a cement kiln runs at around fourteen to fifteen hundred degrees Celsius, a blast furnace hotter still at the tuyeres. The available answers are therefore not "electrify" but a menu of harder ones — hydrogen direct reduction, more scrap through electric arc furnaces, alternative cement chemistries and clinker substitution, and carbon capture — each of which raises cost in a commodity market with thin margins and international competition, which is why the sector's decarbonisation is a trade-policy problem as much as an engineering one. Not a place.