Mass based fuel combustion by DEFRA
This methodology represents greenhouse gas emissions associated with the stationary combustion of fuels as measured on the basis of fuel mass. The data and calculation methodology originates from the UK government department DEFRA, as published in their most recent greenhouse gas (GHG) conversion factors documentation.
The emissions calculation methodology is based upon emissions factors which relate a mass-based quantity of fuel, with its associated quantity of greenhouse gas emissions. These values vary, depending on factors such as the concentration of carbon and moisture within each fuel type.
Each fuel type is represented by six distinct emissions factors, which differentiate greenhouse gas emissions into the following types:
- 'direct CO2 emissions': carbon dioxide emissions produced during fuel combustion
- 'direct CH4 emissions': methane emissions produced during fuel combustion
- 'direct N2O emissions': nitrous oxide emissions produced during fuel combustion
- 'total direct emissions': sum of all direct emissions, i.e. CO2 + CH4 + N2O
- 'indirect emissions': emissions associated with stages in the fuel production chain such as raw material extraction and fuel delivery
- 'life cycle emissions': the total of direct and indirect emissions
Activity data required
Calculations are based on the amount of mass used during combustion of the chosen type of fuel.
Calculation and result
The following quantities are calculated on the basis of the amount of mass combusted and associated emission factors: CO2, CH4, N2O, total direct CO2e, full life cycle CO2e.
Users should note that all quantities (including the separated CH4 and N2O emissions) are expressed in terms of CO2e - the quantity of CO2 that would exert the same atmospheric warming effect and the emissions quantity.
Other DEFRA methodologies are available for fuel combustion with energy and volume based calculations.
Fuel properties, such as density and calorific values, can be found here.
Renewable Fuel Considerations
Separate Emission factors are provided for diesel, petrol, a diesel+biodiesel blend (= 4.2% by unit mass, 4.0% by unit volume, 3.7% by unit energy), and a petrol+bioethanol blend (= 3.1% by unit mass, 2.9% by unit volume, 1.9% by unit energy). Blended fuel emission factors are a weighted average of those respective fuels provided at UK public refuelling stations as a proportion of the total supply. These estimates have been made based on the most recently available reports on the Renewable Transport Fuel Obligation (RTFO).