DEFRA journey based flight methodology

Summary

This methodology represents greenhouse gas emissions associated with typical domestic, short- and long-haul passenger flights. 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

Emissions model

The emissions methodology is based upon emissions factors which describe the rate at which various types of passenger flight emit greenhouse gases in relation to distance travelled. Emissions are calculated by simply multiplying these rates by the typical distances of domestic, short-haul and long-haul flights. The emissions associated with multiple passengers and/or multiple journeys can be obtained by simply multiplying by the appropriate number of passengers and journeys respectively.

Model data

A total of 9 passenger flight scenarios are represented, differentiated by distance categorization (i.e. 'domestic', 'short-haul', 'long haul') and passenger class (e.g. 'economy' versus 'first class'). Each scenario is represented by an illustrative distance which represents the typical flight distance for the associated distance categorization, as well as the following per passenger emissions factors (expressed in terms of kg CO₂e per km), referenced from the an associated DEFRA methodology.

Each passenger transport 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 travel, i.e. fuel combustion
• direct CH₄ emissions: methane emissions produced during travel, i.e. fuel combustion
• direct N₂O emissions: nitrous oxide emissions produced during travel, i.e. fuel combustion
• total direct emissions: 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
• total or 'life cycle': the total of direct and indirect emissions

Activity data required

Calculations are based on the assumed typical distance for the flight type under consideration and the corresponding emissions factors for the flight type and passenger class. If multiple passengers and/or journeys are under consideration, these can be optionally incorporated.

Calculation and result

The following quantities are calculated on the basis of the typical flight distance and associated emissions factors: CO₂, CH₄, N₂O, total direct CO₂e, indirect 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 which would exert the same atmospheric warming effect and the emissions quantity.

This methodology represents per passenger emissions and therefore the returned emissions should be considered - by default - to represent those attributable to single (or multiple, if specified) passengers.

Related methodologies

Other DEFRA methodologies for air travel are available, including those based on known flight distances and Great Circle distance (calculated on the basis of airport IATA codes or latitude and longitude references).

DEFRA also provide other transport methodologies representing road vehicles differentiated by size and market segment, heavy goods vehicles and the transport of freight are also available.