Steel LCA: BF-BOF vs EAF route comparison and scrap rate

Steel has two main production routes: blast furnace + basic oxygen furnace (BF-BOF) and electric arc furnace (EAF). They produce the same finished product (e.g. IPE structural steel) but their environmental profiles differ dramatically. BF-BOF reduces iron ore with coke/coal — a CO₂-heavy chemical process. EAF melts scrap directly — bound to electricity. GWP differs 2-3×.

BF-BOF route — primary steel

BF-BOF is "primary" production starting from iron ore. Coke reduces iron oxide (Fe₂O₃ + 3CO → 2Fe + 3CO₂); then in the BOF, oxygen blown through removes carbon to yield steel. Typical GWP: 1.8-2.3 t CO₂eq/t of hot-rolled steel. Fuel-intensive — efficiency gains move 5-15%, but the chemical-emission floor is rigid. Scrap input is 10-30% feasible, but not much higher — the heat balance breaks.

EAF route — secondary steel

EAF melts steel scrap with electricity. Scrap + limited DRI (Direct Reduced Iron) + alloying inputs yield high-quality steel. Typical GWP: 0.5-0.8 t CO₂eq/t (drops as low as 0.3 with renewable-heavy grids). The whole GWP rides on grid mix and scrap quality. EAF steel on a Scandinavian grid has 4× lower GWP than BF-BOF steel on the EU average. Turkey reached ~45% renewable share in 2025; TR EAF is becoming competitive.

Scrap rate

Even EAF is not 100% scrap; typically 75-90% scrap + 10-25% DRI or pig iron. Scrap quality (alloyed vs carbon steel, contaminated vs clean) shapes finished-product quality. High-tonnage structural steel often uses lower-grade scrap, while automotive-grade hot-rolled needs careful selection. The EN 15804+A2 EPD must report the scrap rate transparently — it underpins the Module D credit.

Module D — the decisive credit for steel

Steel has one of the highest recycle rates of any material — 85-95% for structural steel. Almost all steel is re-melted after end-of-life; Module D reports this circular gain. The worldsteel methodology calculates the credit via the "value of scrap" approach — substituting future virgin-iron-ore use. A BF-BOF producer's Module D credit is -30% to -50%; an EAF producer is already not primary, so Module D is smaller because they already used scrap. This does not mean "both routes converge to the same net" — EAF retains its head-start advantage.

Practical EPD decision matrix

• Structural steel EPD — BF-BOF route shows higher A1-A3 net; but Module D improves cradle-to-cradle
• EAF route is competitive — especially on renewable-heavy grids
• For hot-rolled steel, worldsteel LCI methodology is preferred
• At 85%+ scrap rate, EAF beats BF-BOF in every scenario
• TR EAF for 2025+ (45%+ renewable grid) is gaining ground fast