Emission factor
An emission factor converts an activity into greenhouse gas emissions: kilograms of CO2 equivalent per kilowatt-hour, per kilometer, per tonne of material or per euro spent. Activity data multiplied by the emission factor gives the emissions.
Factors come from public databases. In France, the reference is ADEME's Base Empreinte; internationally, companies use national databases, the IEA for electricity, or commercial databases such as ecoinvent.
Physical factors (per kWh, per tonne) are more accurate than monetary factors (per euro spent), because a price change does not change the emissions. Most companies start with monetary factors for their purchases, then switch to physical data or supplier-specific factors for the items that weigh most.
Go further
- Emission factors: converting data into CO2e
- Physical or monetary method: choose per emission source, not per company