This category allows users to calculate greenhouse gas emissions from aeroplane travel using the latest Defra data and advice. The calculation is based on a given emission factor, dependent on the users drill-down choices, and a distance flown. The distance can be calculated in one of three ways: (1) directly, by specifying an actual distance flown; (2) indirectly, by specifying departure and destination locations; or (3) approximately, by using generic distance categories. In all cases, the returned value represents CO2 equivalent emissions attributable to the journey specified, which includes contributions from carbon dioxide, methane and nitrous oxide.
Directly specifying a distance
Users can alternatively specify the distance travelled. To use this method, select either domestic, short haul, or long haul via the type drill down choice and the appropriate passengerClass (unspecified, economy, economy plus, business, first), via the second drill-down. Next, set the distance flown in the distance profile item value. CarbonKit calculates emissions according to this distance and the selected emissions factor (kg CO2e per mass km). In this case it is up to the user to ensure that the correct drill-down options have been chosen for the specified distance travelled. For example, if a distance of 50 miles was entered for a long-haul flight, the result of the calculation will be incorrect. In this example ''domestic'' travel should be specified instead.
Specifying departure and destination locations
Users can enter either the latitude/longitude of the departure and destination locations or IATA codes for the respective airports involved in travel. In both cases, CarbonKit calculates the distance based on a 'great-circle' calculation (using the haversine formula), and inflates by 9% to account for congestion and indirect routing.
To use this method, select the auto category via the type drill choice and the appropriate passengerClass (unspecified, economy, economy plus, business, first), via the second drill choice. Next, enter departure and destination locations by setting one of the following groups of profile item values:
- lat1, long1, lat2, long2 (i.e. a pair of latitude and longitude coordinates)
- IATACode1, IATACode2 (i.e. a pair of airport IATA codes)
Depending on the distance calculated, CarbonKit selects the appropriate CO2e emissions factor (kg CO2e per mass km). A short haul emissions factor is used for flights under 3700 km, while a long haul factor is used for those greater than 3700 km. For flights originating and landing within a single country, the domestic emissions factor is used.
Generic distance categories
If flight distances, or specific freight departure and destination locations are not available, users can calculate flight emissions based on 'typical' distance categories. CarbonKit follows DEFRA in assuming the following typical one way flight distances:
- domestic = 463 km
- short-haul = 1108 km
- long-haul = 6482 km
Other optional parameters
There are four other optional profile item values that can be set: numberOfPassengers, journeys, useRFI and radiativeForcingIndex.
The *numberOfPassengers profile item value can be used if the user wishes to calculate emissions for multiple people. The journeys profile item value can be used if the specified journey has been flown multiple times. In both of these cases the calculated emissions are multiplied by the number of passengers and the number of journeys entered by the user. The number of passengers and number of journeys are set to 1 if nothing is entered.
If users wish to incorporate the effects of radiative forcing, the useRFI profile item value should be set to true (default value is false). The value of the the radiative forcing index can be set using the radiativeForcingIndex profile item value, defaulting to 1.9 otherwise. For an explanation of the radiative forcing index (RFI) see the here.