Low-Carbon Steel (Green Steel) in Buildings: Scrap, Electricity and EPDs

Low-carbon steel is not one product. The documents we read describe steel made from scrap in electric arc furnaces, with the electricity, the treatment of scrap and the boundary of the calculation changing the printed number. This profile covers structural sections, hollow sections, reinforcing bar, hot rolled coil and sheet used in construction. It does not cover steel made with hydrogen-based direct reduction: we opened no EPD for it and found no declaration for Stegra, so none is cited. We read EPDs from the International EPD System, IBU, MRPI, EPD Hub, SCS Global Services and UL Environment, a manufacturer web page and the catalogue pages of three standards. For a related metal see recycled aluminium; for the other large embodied-carbon item in a structure see low-carbon concrete.^{[1][3][7][10][12][14]}

What makes steel low-carbon in the documents we read?

Two production routes appear. Nucor's beam EPD describes blast furnace steelmaking as using mined iron ore and metallurgical coal and as producing more than 70 % of the world's steel, and EAFs as using post-consumer scrap as their major feedstock;^[12] ArcelorMittal's hollow-section EPD calls the blast furnace route more carbon intensive than EAF steelmaking with at least 75 % scrap and 100 % renewable electricity.^[11] These are manufacturer statements. SSAB's EPD lets us size one number: it assigns pre-consumer scrap a burden of 0.1 kg CO₂e per kg, which it describes as 5 % of the burden of virgin blast-furnace steel, so the EPD implies about 2 kg CO₂e per kg for virgin steel (0.1 ÷ 0.05; our division, an interpretation, not a printed value).^[1] All the low-carbon products below are EAF steel; three levers separate their numbers: how much scrap and what kind, where the electricity comes from, and how the EPD books scrap and end of life.

The levers are visible in Celsa Huta Ostrowiec's two rebar EPDs for the same Polish plant, using the same 2021 data. The version with a standard supplier electricity mix (0.268 kg CO₂e per kWh, 15.7 % renewable) prints A1–A3 GWP-total of 805 kg CO₂e per 1,000 kg; the version modelled with a guarantee-of-origin certificate for wind, solar, biomass and hydro (0.127 kg CO₂e per kWh) prints 356. Only module A1 differs between them, and the A1–A3 difference is 449 kg CO₂e (our subtraction).^[3][4]

How is scrap counted?

Each EPD declares scrap differently. SSAB's table lists post-consumer scrap 87.0 %, pre-consumer 3.2 %, internal scrap 7.8 % and alloys 2.0 % of the coil, a pre- plus post-consumer total of 90.2 %, and 98.0 % recycled content when internal scrap is added; it says its method is aligned with ISO 14021, and its diagram treats external post-consumer scrap and internal scrap as burden-free and external pre-consumer scrap as carrying a burden.^[1] Celsa Huta Ostrowiec's EPDs list post-consumer 78.0 % and pre-consumer 22.0 % (summing to 100 %) plus 3.1 % internal recycling, and model post-consumer scrap as burden-free; 7 Steel UK prints 85.7 % and 14.3 %, Celsa Nervacero 92.8 % and 7.2 % plus 2.83 % internal recycling.^[3][5][6] ArcelorMittal's coil EPD treats all external scrap, including pre-consumer, as burden-free apart from transport, and its IBU sections EPD reports 1,163.1 kg of scrap used per tonne of product.^[10][7] Nucor's beam EPD says external scrap carries no upstream burden under the polluter-pays principle, and prints secondary material use of 716 kg per tonne for its traditional beam and 1,120 kg for its HiRec beam; those are mass flows as printed, not percentages.^[12] Nucor Seattle's rebar EPD states 99.4 % recycled content in its company description and, in its additional information, that the mill uses 97.4 % recycled scrap; it does not split either figure into pre- and post-consumer scrap, and we do not reconcile the two.^[13] Because pre-consumer scrap is booked differently, a recycled-content percentage is not a carbon result.

How is renewable electricity claimed, and is the steel mass-balanced?

In the documents we read the renewable claim is about electricity, backed by certificates. ArcelorMittal's MRPI and UL documents say its XCarb recycled and renewably produced steel uses 100 % scrap and 100 % renewable energy, with the electricity independently verified and a Guarantee of Origin ensured by purchasing Renewable Energy Certificates, which the text calls a market-based offering.^[8][9] SSAB's EPD says the electricity used at its Iowa slab plant is a mix supported by a contractual document (91.3 % wind and 8.7 % nuclear, 0.0093 kg CO₂e per kWh), while the rolling mills use residual national mixes (0.12 kg CO₂e per kWh in Sweden, 0.59 for external electricity in Finland).^[1] Celsa's renewable version relies on a guarantee-of-origin certificate.^[3] None of the steel EPDs we read describes mass-balance or book-and-claim allocation of the steel itself. Nucor's beam EPD says its high-recycled-content beam is produced separately from traditional beam, with the heat number tracked on the material test report;^[12] it does not describe a certificate-based product. Nucor Seattle's rebar EPD describes Nucor's Econiq line as a net-zero certification that balances emissions with renewable electricity certificates and purchased carbon offsets, and says the certificates are not included in its LCA; that is a certificate and offset claim, not a mass-balance allocation of steel, and the Seattle figures in this profile do not include it.^[13] We did not open a primary document on Stegra's certificates, so we make no statement about them.

How do the carbon declarations compare?

All figures are GWP-total for A1–A3 as printed, in the declared unit each EPD states, with nothing converted between rows. EN 15804+A2 EPDs are in the first two tables, split by declared unit; the third table holds EPDs under other rules, where GWP is printed as GWP100 or without a split, as labelled. Each EPD says comparison needs the same category rules, declared unit and life-cycle scope, and the registry and the PDFs disagree on PCR versions for several rows (see the source notes).

Source notes. Registry pages checked 19 October 2026 show status valid for EPD-IES-0018717:002 and 0018719:002 (SSAB; the registry lists the owner as SSAB EMEA AB, the PDFs as SSAB Europe Oy), 0008503:002, 0008502:002 and 0008498:002 (Celsa; registry PCR 1.3.4, PDFs print 1.11), 0007496:006 (7 Steel UK, version of 11 November 2025; registry PCR 1.3.4, PDF 1.11) and 0011080:003 (ArcelorMittal coil; registry PCR 1.3.4, PDF 1.3.1). We show both and do not resolve the differences. The IBU, MRPI, EPD Hub, SCS and UL registers were not opened: those rows rest on the PDFs. Two ArcelorMittal EPDs for the same sections give 333 and 398 kg CO₂e per tonne for A1–A3; they differ in standard version (EN 15804+A1 and A2), background database (GaBi and ecoinvent 3.8, as the documents print), modules and market, and we do not reconcile them. Module D is not comparable across rows: its sign and size depend on each EPD's scenario. SSAB's 0.57 and 0.83 per kg are 570 and 830 per 1,000 kg only by our multiplication.^{[1][2][3][4][5][6][7][9][10][12][13]}

These EPDs are not directly comparable. They differ in declared unit, programme, PCR version, electricity scenario, treatment of pre-consumer scrap, whether the product is fabricated, and the modules declared. We rank no product and draw no conclusion about which is lower; a figure is meaningful for a project only against an EPD with the same declared unit, boundary and rules.

Which standards apply to the products?

In the documents we read, structural products are described against EN 10025 (hot rolled structural steels), with a declaration of performance and CE marking in the EU, fabrication under EN 1090-2, and design under EN 1993 and EN 1994.^[7] The ArcelorMittal IBU EPD also lists ASTM A36, A572, A588, A913 and A992 as product standards (its UL-hosted and MRPI versions add A709) and AISC 303 and AWS D1.1 for fabrication; Nucor's beam EPD lists ASTM A992, A36, A572, A529, A588, A709, A370 and A6, and Nucor Seattle's rebar EPD ASTM A615.^{[7][8][9][12][13]} We cite ASTM only as the EPDs list it and read none of its text. The BSI catalogue page for EN 10025-1:2004 describes general delivery conditions for flat and long products of hot rolled structural steels, excluding hollow sections, and shows the status as current, under review; for execution, BSI lists EN 1090-2:2018+A1:2024 as current.^[15][16] Rebar: Celsa Huta Ostrowiec's EPD lists weldable classes B500SP, B500C, B500SN, B500B and B600B, yield strength 500 to 750 MPa and diameters 8 to 32 mm; the NBS index title for the general standard is BS EN 10080:2005 (the text was not opened).^[3][17] SSAB's EPD says its compositions follow EN 10025, EN 10149 or customer standards and that the steel may contain small residual elements such as copper and tin; its metal-coated EPD refers to EN 10346 for coated sheet.^[1][2] We opened no ResponsibleSteel or other steel-scheme register, so we make no statement about scheme certification; the ISO 14001 certificate that SSAB lists is a management-system certificate.^[1]

When to specify it, and when not

Where the documents support it

• Structural sections and plate, where a product-specific EPD exists. The ArcelorMittal EPDs name multi-storey buildings, single-storey halls and bridges among applications, in usual structural grades with a declaration of performance to EN 10025-1.^[7][9] Nucor's beam EPD names high-rise gravity columns and long-span trusses.^[12] The documents state these as intended uses; we read no project.
• Rebar. Celsa Huta Ostrowiec, 7 Steel UK and Celsa Nervacero declare EAF rebar made from scrap, in ductility classes B500B and B500C among others, per 1,000 kg.^[3][5][6] The same plant's 356 and 805 show why the electricity scenario must be named in the specification.^[3][4]
• Sheet, coil and hollow sections. SSAB and ArcelorMittal declare coil per kg or tonne, SSAB metal-coated sheet 0.40 to 3.0 mm, and ArcelorMittal hollow sections made to EN 10210 or EN 10219. ArcelorMittal's coil EPD lists construction uses including structural or non-structural welded sections, façade and cladding and roofing; SSAB's metal-coated EPD names building and construction among its uses.^{[1][2][10][11]}
• Specifying for an embodied-carbon target. Our suggestion, not a document's: ask for the product-specific EPD (not the brand name), the declared unit, GWP-total A1–A3 with modules C and D shown separately, the programme and PCR version, the electricity basis (contract, guarantee of origin or residual mix), the treatment of pre-consumer scrap, and the registry number so the status can be checked. Compare only EPDs with the same unit and scope, and convert per-kg or per-tonne values to the member or building level with the project's own quantities. Fabricated and unfabricated results, as in Nucor Seattle's rebar EPD (532 and 413), differ and must not be mixed.^[13]
• Traceability. Nucor's beam EPD says HiRec beam is produced on request, separate from traditional beam, with heat numbers tracked on the test report; ask for the equivalent document for the delivered heat.^[12] ArcelorMittal's UL document describes its renewable electricity as certificate-backed (RECs), so ask which certificates cover the delivery.^[8]

Where it needs care or may not suit

• Same grade, same standard, no special treatment. The ArcelorMittal EPDs describe performance in accordance with the declaration of performance under EN 10025-1, and SSAB's compositions follow national, international or customer standards; none says the route changes design properties, and we read no test of low-carbon against conventional steel.^[7][1] Corrosion protection and fire protection follow the design of the member under the relevant standards; the EPDs we read do not address either, except that ArcelorMittal's MRPI EPD says corrosion protection could be required in some cases to reach its 100-year reference service life.^[9] SSAB states that scrap-based steel may contain residual elements such as copper and tin; check the grade's chemistry and weldability limits with the producer.^[1]
• Availability and range. The documents give size ranges (SSAB coil to 20 mm, ArcelorMittal coil to 12.74 mm, rebar to 32 mm in Celsa Huta Ostrowiec's EPD) but not lead times, section ranges or stock, and Nucor says HiRec is made on customer request only.^{[1][10][3][12]} We have no source on delivered availability.
• EPD age and validity. The UL-hosted ArcelorMittal sections EPD prints validity to 18 July 2026, already passed; the IBU copy prints 18 January 2027. Nucor Seattle's rebar EPD uses 2020 data. Check the register before citing a number.^[8][7][13]
• Different numbers for the same steel. The 333 and 398 for ArcelorMittal's sections and Celsa's 356 and 805 show that a product or a plant can carry several figures; the specification should name the document.^[3][4][7][9]
• Reuse as an alternative. The ArcelorMittal IBU EPD assumes 11 % reuse and 88 % recycling at end of life, and Celsa Huta Ostrowiec's EPDs include a reuse route in module D; these are scenarios, not measured rates.^[7][3] We read no source comparing reused steel members with new low-carbon steel, so this profile makes no such comparison.
• Marketing figures. ArcelorMittal's Constructalia page says its XCarb recycled and renewably produced sections have the lowest carbon footprint available on the market, 333 kg CO₂-eq per tonne for A1–A3, based on the IBU EPD. That is the producer's statement; the MRPI EPD for the same product prints 398, and we read no document comparing producers.^[14][9]

Suppliers whose documents we read

Frequently asked questions about low-carbon steel in buildings

The bottom line on low-carbon steel

In the documents we read, the useful questions about low-carbon steel are which route, which plant, which electricity, which scrap and which declared unit. The same plant prints 356 or 805 kg CO₂e per tonne depending on its electricity scenario, the same ArcelorMittal sections print 333 or 398 in two EPDs, and the documents book pre-consumer scrap, electricity certificates and module D differently. The documents describe usual grades and standards and none says design properties differ, but we read no independent test, no steel certification register and no Stegra declaration, and the figures above are what the named documents state.

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