Energy based fuel combustion by DEFRA

Summary

This methodology represents greenhouse gas emissions associated with the stationary combustion of fuels as measured on the basis of energy consumption. 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 methodology

The emissions calculation methodology is based upon emissions factors which relate a quantity of energy yielded by the fuel (and consumed by the user) with its associated quantity of greenhouse gas emissions. These values vary, depending on factors such as the energy content ('heating' or 'calorific' value) of the particular type of fuel as well as its typical concentration of carbon and moisture. The energy content of the fuel can be expressed on either a 'net calorific' basis or a 'gross calorific' basis, the difference depending on whether the latent heat of condensation of water vapour is recovered. Users should check the calorific basis of their energy consumption in order to make accurate emissions calculations.

Model data

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 energy used during combustion of the chosen type of fuel, on either a net or gross basis.

Calculation and result

The following quantities are calculated on the basis of the amount of energy 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.

Related methodologies

Other DEFRA methodologies are available for fuel combustion with mass and volume based calculations.

Fuel properties, such as density and calorific values, can be found here.

Notes

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).