Labs · Steel route lab

Which steelmaking route uses the least energy and emits the least CO₂?

Scrap in an electric furnace. On Cameroon’s grid, Phase 1, with imported direct-reduced iron, would emit about 0.58 t of CO₂ per tonne, against 2.29 t for the blast furnace.

Result

Derived

On a grid at 226 g CO₂/kWh, Cameroon Steel’s Phase 1 would emit about 0.58 t of CO₂ per tonne of product, imported direct-reduced iron included: 75% less than the blast-furnace route (2.29 t). At this level, hydrogen direct reduction beats gas-based reduction; it loses the edge above about 370 g/kWh.

0.58t CO₂/t

Cameroon Steel, Phase 1

2.29t CO₂/t

Blast furnace, same grid

75%

Reduction against the blast furnace

370g/kWh

Threshold where hydrogen beats gas

963kWh/t

Phase 1 electricity per tonne

Four readings of one question

Five routes, three measures, one grid

CO₂ per tonne (t CO₂/t)

Sensitivity to the power grid (t CO₂/t)

Final energy per tonne (GJ/t)

Electricity per tonne (kWh/t)

CO₂ bars: grey is the part the grid does not change (direct and upstream emissions), orange the electricity part. Light tick: worldsteel 2024 world average. Cameroon Steel per tonne of finished product (rolling included); other routes per tonne of crude steel. The scrap row is a world average on worldsteel’s boundary, which also counts reheating fuel and the upstream of purchased inputs such as lime and oxygen; the Cameroon Steel row counts furnace emissions, electricity and imported iron only. The two are not on the same basis.

CO₂ per tonne, Final energy per tonne, Electricity per tonne
Route	t CO₂/t	GJ/t	kWh/t
Blast furnace	2.29	21.4	150
Gas DRI	1.26	17.1	680
Hydrogen DRI	0.87	12.2	3,400
Scrap	0.53	2.1	520
Cameroon Steel P1	0.58	7.1	963

Model assumptions

25 assumptions

Parameter	Value used	Range	Status	Source
Carbon intensity of the Cameroon grid (2024)	226 g CO₂/kWh	200 – 300	Sourced	Ember via Our World in Data, carbon intensity of electricity generation: Cameroon 225.9 g CO₂e/kWh in 2024, when hydropower supplied about 72% of generation; ARSEL reports about 90% hydro for 2025; the 2024 factor is kept as the prudent value
Sensitivity: Cameroon grid at the 2025 mix	85 g CO₂/kWh	74 – 96	Illustrative	Order of magnitude, not a published factor: the 2025 mix reported by ARSEL (7,272.4 of 8,119.9 GWh from hydropower, about 10% thermal) combined with the thermal intensity implied by the Ember 2024 value (225.9 g/kWh with about 28% non-hydro generation); range of White paper 06, Chapter 3: about 74 g/kWh counting combustion only, about 96 g/kWh with life-cycle factors for hydro and solar; the tools use the midpoint
Grid factor implicit in the world averages	538 g CO₂/kWh	450 – 550	Assumption	IEA Iron and Steel Technology Roadmap (2020) world grid factor 538 g/kWh, used here to split the worldsteel averages into an electricity part and the rest
CO₂ intensity, blast furnace (world average)	2.34 t CO₂/t	—	Sourced	worldsteel, Sustainability Indicators 2025 (2024 data)
CO₂ intensity, direct reduction (world average)	1.47 t CO₂/t	—	Sourced	worldsteel, Sustainability Indicators 2025 (2024 data)
CO₂ intensity, scrap electric furnace (world average)	0.69 t CO₂/t	—	Sourced	worldsteel, Sustainability Indicators 2025 (2024 data)
Final energy, blast furnace	21.4 GJ/t	—	Sourced	IEA, Iron and Steel Technology Roadmap (Oct 2020), final energy by route
Final energy, gas DRI and electric furnace	17.1 GJ/t	—	Sourced	IEA, Iron and Steel Technology Roadmap (Oct 2020), final energy by route
Final energy, scrap and electric furnace	2.1 GJ/t	—	Sourced	IEA, Iron and Steel Technology Roadmap (Oct 2020), final energy by route
Purchased electricity, blast furnace	150 kWh/t	50 – 300	Assumption	Planning assumption: integrated works generate most of their own power from process gases
Electricity, gas DRI and electric furnace	680 kWh/t	550 – 800	Derived	EC JRC BREF (2013) EAF 404–748 kWh/t; +14.5 kWh/t per +10% DRI in the charge; Energiron ~73 kWh/t DRI (EC ICIT)
Electricity, hydrogen DRI (electrolysis included)	3,400 kWh/t	3,200 – 3,600	Derived	About 54 kg H₂ per t DRI and 2.4–2.8 MWh/t DRI of electrolysis (Midrex, IEA), plus the electric furnace: 3.2–3.6 MWh/t of steel
Electricity, scrap and electric furnace	520 kWh/t	404 – 748	Derived	EAF 450 kWh/t (IFC EHS 2007, range 347–500) plus 70 kWh/t ladle furnace and auxiliaries (RC-1)
Non-electric emissions, hydrogen DRI	0.10 t CO₂/t	0.05 – 0.15	Assumption	Planning assumption, same order as the electric-furnace direct emissions of RC-1 (0.06–0.15 t/t); IEA near-zero threshold 0.40 t/t
Direct furnace emissions (electrodes, carbon, lime)	0.10 t CO₂/t liquid steel	0.06 – 0.15	Assumption	Cameroon Steel reference configuration RC-1, edition 10 Oct 2026 (planning estimate, not a design figure): 0.06–0.15 t/t
Upstream emissions of imported DRI (gas-based)	0.7 t CO₂/t DRI	0.5 – 0.9	Assumption	Cameroon Steel reference configuration RC-1, edition 10 Oct 2026 (planning estimate, not a design figure): gas-based shaft furnace, 0.5–0.9 t/t
Electric arc furnace electricity	450 kWh/t liquid steel	347 – 500	Sourced	IFC EHS Guidelines for Integrated Steel Mills (2007): 1,250–1,800 MJ/t = 347–500 kWh/t; RC-1 uses 450
Extra electricity per point of DRI above 30%	1.45 kWh/t per point of DRI	1.00 – 2.00	Derived	EC ICIT, Energiron: +14.5 kWh/t per +10% DRI in the charge
Ladle furnace, caster, oxygen, water, compressed air, lighting	70 kWh/t liquid steel	50 – 100	Assumption	Cameroon Steel reference configuration RC-1, edition 10 Oct 2026 (planning estimate, not a design figure): 50–100 kWh/t
Rolling	110 kWh/t product	70 – 140	Sourced	IFC EHS Guidelines (2007): rolling 70–140 kWh/t
Electric billet reheating (induction, partly hot-charged)	300 kWh/t product	150 – 400	Assumption	Cameroon Steel reference configuration RC-1, edition 10 Oct 2026 (planning estimate, not a design figure): 150–400 kWh/t
Casting and rolling yield	0.94 t/t	0.92 – 0.96	Assumption	Cameroon Steel reference configuration RC-1, edition 10 Oct 2026 (planning estimate, not a design figure): 0.92–0.96
Metallic yield of scrap in the furnace	0.90 t/t	0.88 – 0.92	Assumption	Calibrated so that a 70/30 scrap–DRI charge gives the RC-1 melt-shop yield of 0.88 (range 0.85–0.91)
Metallic yield of DRI in the furnace	0.833 t/t	0.800 – 0.870	Assumption	DRI carries 6–8% gangue and unreduced oxide; calibrated with the scrap yield on the RC-1 value 0.88
Natural gas for direct reduction (upstream)	10.0 GJ/t DRI	9.5 – 11.0	Assumption	Midrex ~9.8 GJ/t; Energiron ~10 GJ/t; Suez Steel 9.2 GJ/t (2026)

How this is calculated

For each reference route, the world intensity published by worldsteel (I) is split into an electricity part, E × g_ref, and a remainder R = I − E × g_ref, where E is the electricity used per tonne and g_ref = 538 g/kWh the IEA world grid factor. On a grid g the intensity is R + E × g: at 538 g/kWh the model returns exactly 2.34, 1.47 and 0.69 t CO₂/t. The hydrogen route is computed the same way with 3,400 kWh/t (electrolysis included) and a 0.10 t remainder.

Cameroon Steel’s Phase 1 is built piece by piece from the RC-1 reference configuration, per tonne of finished product: direct furnace emissions (0.10 t per tonne of liquid steel), upstream emissions of imported direct-reduced iron (0.7 t per tonne of DRI), and all site electricity, furnace, ladle, rolling and induction reheating included (963 kWh/t by default), multiplied by g. Each point of DRI above 30% adds 1.45 kWh/t to the furnace. Tonnages follow from the yields: liquid steel = products ÷ 0.94; metallic charge = liquid steel ÷ Y, where Y is the furnace yield of scrap (0.90) and of direct-reduced iron (0.833) weighted by their shares, as in the value-chain explorer. Y is 0.88 at 30% DRI and falls as that share rises (0.833 at 100%), so more DRI is needed per tonne of steel.

Limits. World averages blend very different plants; calculation boundaries (crude steel or finished product, upstream included or not) differ slightly between sources; energy is final energy (IEA), not primary. Indicative results, to be replaced by verified measurements in operation.