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Emission Factor: The Building Block of Every Carbon Footprint Calculation

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An emission factor is a coefficient that quantifies the greenhouse gas (GHG) emissions associated with a specific activity, material, process, or energy source. It expresses the amount of CO₂e released per unit of input or output — for example, kilograms of CO₂e per kilogram of steel produced, per kilowatt-hour of electricity consumed, or per tonne-kilometre of freight transported. Emission factors are the fundamental building blocks of every carbon footprint calculation: without them, activity data — how much material was used, how much energy was consumed, how far a product was shipped — cannot be converted into GHG emissions.

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Every Product Carbon Footprint (PCF), every Scope 3 inventory, and every LCA depends on the quality, accuracy, and representativeness of the emission factors it uses. The better the emission factors, the more reliable — and more defensible — the resulting carbon calculation.

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How emission factors work

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The basic calculation is straightforward:

GHG Emissions = Activity Data × Emission Factor

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For example: a company ships 1,000 kg of goods by truck over 500 km. The emission factor for road freight might be 0.062 kg CO₂e per tonne-kilometre. The resulting emissions are 1,000 kg × 500 km × 0.062 ÷ 1,000 = 31 kg CO₂e.

The same logic applies across every stage of a product's lifecycle — from the CO₂e intensity of a raw material like aluminium or polypropylene, to the emissions associated with a manufacturing process like injection moulding or welding, to the energy mix of a specific country's electricity grid. Each of these requires a corresponding emission factor, and each factor introduces a degree of uncertainty that compounds across the full life cycle assessment.

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Types of emission factors

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Emission factors vary significantly in origin, scope, and accuracy:

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Activity-based emission factors are tied to a specific physical activity — energy consumption, material use, distance travelled. They are the most common type in GHG Protocol-aligned reporting.

Spend-based emission factors convert monetary expenditure (e.g. euros spent on a category of goods) into estimated CO₂e. They are simple to apply but offer low accuracy and are generally only used as a last resort when no better data is available.

Average or generic emission factors represent industry-wide or process-wide averages, drawn from life cycle databases such as ecoinvent or the European Life Cycle Database (ELCD). They are widely used for secondary data scenarios where supplier-specific data is unavailable.

Supplier-specific or product-specific emission factors are derived from actual production data at a specific facility or for a specific material. They represent primary data and deliver the highest level of accuracy — and are increasingly requested in regulatory contexts such as CBAM and the EU Battery Regulation.

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Why emission factor quality determines PCF quality

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In a PCF calculation, the emission factor is often where the most significant uncertainty resides. A company may know precisely how many kilograms of a given material it uses, but if the emission factor assigned to that material is outdated, regionally unrepresentative, or derived from a low-quality source, the resulting carbon figure will be unreliable — even if the rest of the calculation is methodologically sound.

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This matters particularly for Scope 3 emissions, where companies rely heavily on secondary emission factors for purchased goods, materials, and logistics. The GHG Protocol and ISO 14067 both specify data quality criteria — accuracy, completeness, consistency, timeliness, and geographic representativeness — that emission factors must meet for a carbon calculation to be considered robust and audit-ready.

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For CSRD reporting, these quality criteria are no longer just good practice: they are a compliance requirement, since all disclosures are subject to external assurance. Using verified, regularly updated emission factors is therefore a prerequisite for meeting audit-level expectations.

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Emission factors across the product lifecycle

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In a full LCA or PCF calculation, emission factors are needed at every stage:

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• Raw materials: CO₂e per kg of steel, aluminium, polymer, composite, or other input material — often with differentiation by production route (e.g. primary vs. recycled aluminium) and country of origin
• Manufacturing processes: CO₂e per unit of energy consumed in processes like casting, moulding, welding, or coating
• Energy: CO₂e per kWh of electricity, based on the energy mix of the specific country or region — a factor that varies enormously between, for example, Norway (hydro-dominated) and Poland (coal-dominated)
• Logistics and transport: CO₂e per tonne-kilometre by transport mode (road, rail, sea, air)
• End-of-life: CO₂e associated with recycling, incineration, or landfill scenarios

The system boundary chosen for the PCF — cradle-to-gate, cradle-to-grave, or cradle-to-cradle — determines which of these emission factors are included in the calculation.

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Emission factors and the sustamize database

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Accessing high-quality, up-to-date emission factors at the material and process level is one of the most significant practical challenges in PCF calculation — particularly for companies working across diverse materials, geographies, and supply chains. This is why the choice of CO₂e database matters: databases that are regularly updated, regionally differentiated, and independently validated provide a fundamentally more reliable foundation than static or generic alternatives. For procurement teams comparing materials or suppliers, the difference between a verified emission factor and a generic industry average can significantly change the carbon picture — and therefore the sourcing decision.

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Looking for verified emission factors for your PCF or Scope 3 calculation?

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Explore our CO₂e database covering materials, electronics, logistics, energy, and manufacturing processes, or contact our team to access the sustamizer® and integrate verified emission factors directly into your PCF workflows.

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