Embodied Carbon
Before a new building uses a single kilowatt-hour of energy, it has already caused emissions — in the cement kiln, the steel furnace, the aluminium smelter, and the lorries that carried it all to site. For a modern, energy-efficient building, those material emissions can outweigh everything the building will emit from heating and power over decades of use. And unlike an energy bill, they cannot be reduced later: they are locked in the moment the material is made.
That locked-in footprint is embodied carbon. Embodied carbon is the greenhouse gas emissions from the materials and construction of a building or product across its life cycle — everything except the operational energy used while it is occupied.
Embodied carbon is the emissions from producing, transporting, installing, maintaining and disposing of the materials in a product or building — everything except operational energy. Embodied plus operational is whole-life carbon; for most companies it is a Scope 3 emission.
Definition — The Carbon Locked in Materials
Embodied carbon is the total greenhouse gas emissions associated with the materials and construction processes of a product or building throughout its life cycle. It captures the carbon released in extracting raw materials, manufacturing them into products, transporting them, installing them on site, maintaining and replacing them over the building’s life, and finally disposing of or recovering them. What it deliberately excludes is operational carbon — the energy used to heat, cool, light, and power the building while it is occupied.
The word “embodied” captures the key idea: this carbon is built into the material itself by the time it arrives, a consequence of how it was made rather than how it is used. A tonne of steel carries its furnace emissions with it whether it ends up in a bridge or a bench. That is why embodied carbon is expressed as an intensity — kilograms of CO₂-equivalent per kilogram, cubic metre, or square metre of material — and why the choice of material and how it was produced matters so much.
Embodied carbon is most often discussed for buildings and construction, where it can dominate a project’s footprint, but the same concept applies to any manufactured product. In corporate greenhouse-gas accounting, the embodied carbon of the materials and assets a company buys shows up in its Scope 3 emissions — purchased goods and services, and capital goods.
Definition at a glance
| What it is | GHG emissions from a building’s / product’s materials and construction, across the life cycle |
|---|---|
| What it excludes | Operational carbon — energy used during occupation (EN 15978 modules B6–B7) |
| Whole-life carbon | Embodied + operational carbon |
| Measured in | kg CO₂e per kg / m³ / m² of material |
| Method | EPDs & coefficients against the EN 15978 life-cycle stages |
| In GHG accounting | Scope 3 — purchased goods and capital goods |
Embodied vs Operational vs Whole-Life Carbon
A building’s total climate impact — its whole-life carbon — has two halves. Operational carbon is the emissions from energy used while the building runs; embodied carbon is everything else, locked into its fabric. For decades operational carbon dominated, so efficiency standards focused on it. But as buildings become highly energy-efficient and grids decarbonise, the operational half shrinks — and embodied carbon, which does not, becomes the larger and more urgent share.
Operational carbon is spread over the building’s life and can be cut later — better controls, a cleaner grid, a retrofit. Embodied carbon is front-loaded: the bulk of it, the modules A1–A5 known as upfront carbon, is emitted before the building is even occupied. It is spent in the critical near-term decade for climate, and once the concrete is poured and the steel is set, it cannot be taken back. That irreversibility is why upfront carbon has become the sharp focus of building decarbonisation.
The Life-Cycle Stages (EN 15978)
Embodied carbon is defined precisely by which life-cycle stages it covers. The European standard EN 15978 divides a building’s life into labelled modules, and embodied carbon is every module except the operational ones:
| Module | Stage | Embodied? |
|---|---|---|
| A1–A3 | Product — raw material supply, transport, manufacturing (cradle-to-gate) | Yes — upfront |
| A4–A5 | Construction — transport to site, installation | Yes — upfront |
| B1–B5 | Use — maintenance, repair, replacement, refurbishment | Yes |
| B6–B7 | Operational energy & water use | No — operational |
| C1–C4 | End of life — demolition, transport, processing, disposal | Yes |
| D | Beyond the boundary — reuse, recovery, recycling benefits | Reported separately |
So upfront carbon is A1–A5, cradle-to-gate is A1–A3 (the most commonly quoted figure for a material), and whole-life adds the operational modules B6–B7. Module D — the recycling or reuse benefit at end of life, such as the -1.11 kg CO₂e per kg [GreenCalculus materials.steel.galvanised.module_d · OEKOBAUDAT 2024] credit for recovering galvanised steel — sits outside the system boundary and is reported as a separate figure, never netted into the total.
The Numbers: Embodied Carbon by Material
Materials differ enormously in their embodied carbon. The cradle-to-gate (A1–A3) intensity per kilogram spans nearly two orders of magnitude — and, tellingly, the same metal can sit at either end depending on whether it is made from primary or recycled feedstock. Live coefficients:
| Material (per kg) | Embodied carbon kg CO₂e / kg, A1–A3 |
|---|---|
| Aluminium — primary | 10.1 |
| Stainless steel (fasteners) | 6.883 |
| Steel — galvanised | 2.48 |
| Cement — CEM I Portland | 0.665 |
| Steel — reinforcement (rebar) | 0.47398 |
| Aluminium — recycled | 0.26 |
| Brick — sand-lime | 0.126 |
Cradle-to-gate (A1–A3) embodied carbon, kg CO₂e per kg (ÖKOBAUDAT, live). Primary aluminium is the outlier — smelting is electricity-hungry — while the same metal recycled is a fraction of it. Note the basis: this is per kilogram. Concrete’s per-kg figure is low, but a building uses it by the tonne, so by volume concrete and steel usually dominate a structure’s total embodied carbon.
Wood products can have a negative cradle-to-gate figure, because growing timber absorbs biogenic CO₂ that is stored in the material: cross-laminated timber is around -660.1 [GreenCalculus materials.timber.clt.module_a1_a3 · OEKOBAUDAT 2024] and sawn hardwood around -1019.3 kg CO₂e [GreenCalculus materials.timber.hardwood_sawn.module_a1_a3 · OEKOBAUDAT 2024] per cubic metre (a volume basis, not per kg — do not compare directly with the table above). That stored carbon is only a lasting benefit if the timber is sustainably sourced and kept out of landfill or the furnace at end of life, where modules C and D would release it again.
A steel frame uses 100 tonnes of hot-rolled sections. Using the live cradle-to-gate factor (snapshot 2026-07-26):
- 100,000 kg × 0.56029 kg CO₂e/kg = 56,029 kg CO₂e ≈ 56 t — the upfront embodied carbon of the frame, emitted before the building opens.
The EN 15978 whole-building LCA calculator assembles a full building across all modules; the masonry & finishes calculator handles element-level build-ups.
Reducing Embodied Carbon
Because embodied carbon is set by material choice and production, it is cut at the design and specification stage — not after construction. The biggest levers:
- Recycled content. Recycled aluminium (0.26 kg/kg [GreenCalculus materials.aluminium.recycled_secondary.module_a1_a3]) carries roughly 97% less embodied carbon than primary (10.1 kg/kg) [GreenCalculus materials.aluminium.ingot_primary.module_a1_a3 · EUROPEAN 2024]. Secondary feedstock is the single largest lever for metals.
- Low-carbon mixes. Replacing Portland cement (CEM I, 0.665 kg/kg [GreenCalculus materials.concrete.cement.cem_i_portland.module_a1_a3 · OEKOBAUDAT 2024]) with blast-furnace-slag blends (CEM III, 0.433 kg/kg [GreenCalculus materials.concrete.cement.cem_iii_blast_furnace.module_a1_a3 · OEKOBAUDAT 2024]) cuts the carbon of the most-used building material on Earth.
- Material efficiency & reuse. Using less material, designing for disassembly, and reusing existing structures avoid the emission entirely — the lowest-carbon material is the one not made.
- Timber substitution. Replacing carbon-intensive materials with sustainably sourced biogenic ones stores carbon rather than emitting it, subject to end-of-life fate.
Common Confusions
- Confusing embodied with operational carbon. Embodied is the carbon in the materials and construction; operational is the energy used in occupation. Together they are whole-life carbon — and in an efficient building, embodied is often the larger share.
- Assuming embodied carbon means only A1–A3. Cradle-to-gate (A1–A3) is the most-quoted figure, but embodied carbon also includes construction (A4–A5), maintenance and replacement (B1–B5), and end of life (C1–C4).
- Comparing per-kg and per-volume figures. A material’s basis matters: aluminium’s per-kg figure is huge but you use little; concrete’s is low but you use tonnes. Compare like with like, and ideally at the element or building level.
- Reading timber’s negative figure as a free pass. The stored biogenic carbon only stays a benefit if the wood is sustainably sourced and not burned or landfilled at end of life, where it would be released.
- Netting the module D recycling credit into the total. The end-of-life reuse/recovery benefit (-1.11 kg/kg [GreenCalculus materials.steel.galvanised.module_d] for galvanised steel) is reported separately, beyond the system boundary — not subtracted from the headline embodied figure.
Dataset — the full factor set behind this term, versioned with source provenance and downloadable as CSV with a citable Zenodo DOI, is published as the Ökobaudat embodied carbon factors dataset.
Frequently Asked Questions
Embodied carbon is the greenhouse gas emissions associated with the materials and construction of a building or product across its life cycle — extracting and manufacturing the materials, transporting and installing them, maintaining and replacing them, and disposing of them at end of life. It excludes operational carbon, the energy used while the building is occupied. Embodied plus operational carbon together make up whole-life carbon. It is measured in kilograms of CO₂-equivalent per unit of material against the EN 15978 life-cycle stages, and for companies it is a Scope 3 emission.
Embodied carbon is the emissions locked into a building’s materials and construction — from making, transporting, installing, maintaining, and disposing of them. Operational carbon is the emissions from the energy used to run the building while it is occupied: heating, cooling, lighting, and power (EN 15978 modules B6–B7). Together they are whole-life carbon. The key practical difference is timing: operational carbon is spread over the building’s life and can be reduced later through efficiency or a cleaner grid, while embodied carbon — especially the upfront portion (A1–A5) — is emitted before occupation and cannot be undone. As buildings get more energy-efficient, embodied carbon becomes the larger share of the total.
Upfront carbon is the portion of embodied carbon emitted before a building is occupied — the EN 15978 modules A1–A5, covering material production (A1–A3, cradle-to-gate) and construction (A4–A5, transport to site and installation). It is the most urgent part of a building’s footprint for two reasons: it is released now, in the critical near-term decade for climate action, and it is irreversible — once the materials are made and installed, that carbon cannot be recovered. This is why building decarbonisation increasingly targets upfront carbon specifically, through material choice, recycled content, low-carbon mixes, and material efficiency at the design stage.
Per kilogram, primary metals are the most carbon-intensive. Primary aluminium is around 10.1 kg CO₂e per kg [GreenCalculus materials.aluminium.ingot_primary.module_a1_a3] cradle-to-gate, and stainless steel fasteners around 6.883 kg [GreenCalculus materials.steel.stainless.module_a1_a3 · OEKOBAUDAT 2024], because smelting and alloying are energy-hungry. Structural steel is much lower (0.47398 [GreenCalculus materials.steel.reinforcement.module_a1_a3 · OEKOBAUDAT 2024]–0.56029 kg/kg) [GreenCalculus materials.steel.sections_hot_rolled.module_a1_a3 · OEKOBAUDAT 2024], and cement around 0.665 kg/kg [GreenCalculus materials.concrete.cement.cem_i_portland.module_a1_a3]. But per-kg figures can mislead: concrete’s intensity is low, yet buildings use it by the tonne, so by volume concrete and steel usually dominate a structure’s total. Recycled feedstock changes everything — recycled aluminium is only about 0.26 kg/kg [GreenCalculus materials.aluminium.recycled_secondary.module_a1_a3]. Timber can even be negative per cubic metre, because it stores biogenic carbon.
For most organisations, yes. The embodied carbon of the materials, products, and assets a company buys falls in its Scope 3 value-chain emissions — specifically Category 1 (purchased goods and services) and Category 2 (capital goods), which covers buildings, plant, and equipment. It is not part of the company’s own Scope 1 or Scope 2, because the emissions occurred upstream, at the material producers and manufacturers. For a construction or real-estate business, embodied carbon is often the single largest part of the Scope 3 footprint, which is why it is measured with Environmental Product Declarations and assessed against standards such as the RICS Whole Life Carbon Assessment.
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