Why steel is the target
Conventional steelmaking reduces iron ore with coking coal in a blast furnace, emitting roughly two tonnes of CO₂ per tonne of steel — making steel one of the largest single industrial emission sources and, for builders, typically the biggest line in a structure’s embodied-carbon account after concrete. "Green steel" is any production route that removes most of that: today that means hydrogen direct reduction, recycled scrap in electric arc furnaces on clean power, and — further out — direct electrolysis of ore.
The routes, honestly ranked
Scrap-EAF is available now and genuinely low-carbon on renewable power, limited by scrap supply and some quality constraints for demanding grades. Hydrogen direct reduction (H2-DRI) replaces coal with green hydrogen to reduce ore, then melts in an EAF: HYBRIT in Sweden has delivered pilot fossil-free steel to real customers (Volvo among the first) and Stegra’s Boden plant is the first commercial-scale attempt. Molten oxide electrolysis (Boston Metal) reduces ore directly with electricity — elegant, earlier-stage. The binding constraint on the hydrogen route is cheap clean electricity at enormous scale, which is why the first plants sit next to Nordic hydro and why Australian ore-plus-renewables projects keep being proposed.
The state of supply
Be honest about volumes: genuinely fossil-free primary steel is pilot-to-first-commercial scale, sold out years ahead to anchor customers (automotive first) paying a green premium. Recycled-EAF steel is widely available today and is what most current "low-carbon steel" procurement actually buys. For structural sections and rebar in Australia, the near-term practical play is EAF-route product with an Environmental Product Declaration (EPD) — real reductions, documented, available.
What it costs
Current green premiums for hydrogen-route steel are meaningful at the steel line but small at project level: structural steel is a modest fraction of project cost, so even a 20–30% steel premium moves a building’s cost by well under 1% in most cases. That is why carbon-scored tenders adopt it faster than pure cost logic would predict: the reputational and scoring value outweighs the premium. Premiums for recycled-EAF product with EPDs are smaller again and often negligible.
What builders should do now
Embodied carbon is becoming a quantity surveyed like any other — measured, priced, claimed and audited. The preparation is procedural, not exotic: require EPDs on steel packages; keep delivery-level traceability from mill certificate to the element the steel went into; and be able to report a structure’s carbon account from records rather than estimates. Builders who can trace what steel went into which element, with supplier documentation attached, will win the tenders where carbon is scored — and will be ready when green-steel supply scales.