Decarbonizing Steel: The Process and Pathways
- 3 days ago
- 2 min read
Steel manufacturing from raw materials to finished products represents one of the most energy-intensive industrial processes, accounting for 7–8% of GHG emissions. It begins with iron-ore extraction and proceeds through ironmaking, steelmaking, continuous casting, and hot, and sometimes, cold rolling. The final coils, sheets, plates, bars, or structural sections are then transported to downstream manufacturing facilities in various sectors.
Iron ore undergoes crushing, grinding, magnetic separation, and agglomeration into pellets. In the dominant blast-furnace route, iron ore, coke, and limestone are charged into a tall shaft furnace. Hot air is blasted in at the base, creating temperatures up to ~2,000 °C. Coke provides both heat and the reducing agent, carbon monoxide. Molten pig iron collects at the hearth and is tapped periodically, while impurities float and are removed.
Then, pig iron is converted to steel in a basic-oxygen furnace (BOF), a method representing 70% of global primary production, and includes up to 30% scrap. Another method uses an electric-arc furnace (EAF) and primarily scrap metal. This process represents a growing share globally and is dominant in the US. Finished products are then created by casting and rolling liquid steel into hot-rolled coils, cold-rolled sheets, bars, rails, and beams.
Sustainability improvements already in effect include EAF systems which use 100% recycled scrap and achieve 75% lower emissions. Another lower-emission pathway uses natural gas or, increasingly, hydrogen with direct reduction of iron processes. Waste-heat recovery, AI-optimized operations, and top-gas recycling in blast furnaces offer additional opportunities. There are also some early carbon-capture pilots targeting 65% capture.
Frontier technologies include a hybrid system utilizing hydrogen-based direct reduction and EAFs, which replace carbon-based reductants, produce just water vapor, and can achieve 95% emissions reductions when paired with renewable energy. Europe leads with about 2.5 Mt of capacity, with landmark plants such as Stegra in Sweden targeting its first commercial output this year, using renewable-powered electrolysis.
Another method developed by Boston Metal, electrolyzes iron ore directly in a molten-oxide bath and uses inert anodes and renewable electricity. It bypasses coke and hydrogen requirements and produces just liquid iron and oxygen gas with near-zero process emissions. Adaptive technologies that work with existing systems include smelt-reduction with carbon capture utilization and storage, and the use of biomass reductants which replace carbon sources like fossil coke derived from metallurgical coal.
Collectively, these technologies, supported by trillions in projected infrastructure investment, are expected to enable the sector’s alignment with net-zero pathways by mid-century.
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