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Calculating Carbon Emissions

Calculating Carbon Emissions

Calculating the CO2 emitted by flights

There are two different cycles during a flight, the Landing and Takeoff Cycle (LTO) and the Cruise Cycle (CC), and these influence the amount of CO2 emitted during a flight. The LTO consists of all activities undertaken by the plane below 1000m, such as taxiing in and out of the various locations in the airport, takeoff, climb-out and landing. The CC takes into account all activities above 1000m, when the plane is travelling at a relatively constant altitude. A lot more fuel goes into the LTO stage than the CC activities, so short-haul and domestic flights, which have a high LTO to CC ratio, actually consume more fuel per passenger kilometre (pkm) travelled and produce more CO2 per km than long-haul flights.

kgCO2/pkm for Domestic, Short and long haul flights (DEFRA, "Act on CO2")

Flight Type KgCO2/pkm Average Journey Length (km) Total kgCO2 + Uplift Factor of 9% Example Journey
Domestic (B737 – 400 and Dash 8-Q400) 0.158 463 79.74 London - Paris
Short haul (B737) 0.130 926 131.21 London – Milan
Long Haul (B767-300ER and B747-400) 0.105 6482 741.86 London – Kampala (Uganda)

Many of the destinations that our volunteers travel to are reached by multi-stop journeys, which means that several shorter flights are taken instead of a direct one. This affects the total amount of carbon produced by the journey, because there are several LTO Cycles, thus consuming more fuel and releasing more CO2 than a direct one would. For example, the Frontier journey from London to Diego Suarez, Madagascar, involves the following flight plan: London – Marseille – Antananarivo – Diégo Suarez (Antsiranana).

The CO2 emission for this journey is detailed below.

A calculation of the CO2 emission for a straight line trip (17051km return) comes to 1951 kgCO2/pkm, which clearly underestimates the total CO2 emitted for the journey actually taken. Therefore, for the Frontier exclusive projects (Madagascar, Tanzania, Fiji, Nicaragua and Cambodia) we have calculated the precise CO2 emitted for each flight plan. However, for projects where the volunteers organise their own flights, we have had to use the straight line distance between London and the host airport. So that volunteers can accurately calculate their overall carbon footprint, they have the option of adding any other domestic and short-haul flights they may take.

There is also a distinct difference in CO2 emissions between different aircrafts. Unfortunately, we cannot yet factor all the different types of aircraft into our calculation, so we have used an example range of emissions from the most used aircraft types. In addition, these calculations do not take into account any additional, non-CO2-related impacts of flying, as the science is still being developed. Frontier will continue to update their methodologies and will strive to account for all aspects of the impacts of aviation as climate change science progresses.

These calculations are based on DEFRA's Act on CO2 emission calculations, and studies from the European Environmental Agency.

Carbon offset calculation

The tree-planting project aims to offset the carbon dioxide emitted by the flights of our volunteers, by actively reforesting 2 hectares of land in Indonesia, as trees use large amounts of carbon dioxide and stock carbon as they grow. It takes on average 20 years for a newly planted forest to attain maturity, so any trees we plant now will be offsetting carbon for the next 20 years.

The calculation of the amount of carbon stored by the growing forest includes the carbon stored in the trees and soils, minus the release of carbon by the decay of dead organic matter, such as dead wood. However, dead organic matter really only develops once live vegetation is established, grows and dies. In addition, there will be no harvesting for industrial or fuelwood purposes, nor any release of carbon through natural disturbances as yet, so we can reduce the calculation to the amount of carbon stored by the growth of the trees and that associated with changes in soils.

Based on the basic method provided in the IPCC 2006 Guidelines for National Greenhouse Gas Inventories, and using their default tropical rainforest biomass values and emission factors, we estimate a change in carbon stocks of 6.7 tonnes C/year over the 2 hectares for tree growth, and an offset of 0.13 tonnes C/year in soils, amounting to an offset of 6.83 tonnes C/year, equivalent to 25 tonnes CO2 per year, i.e. 12.5 tonnes CO2 per year per hectare.

Averaging the offset over all tree species we aim to plant, one tree can be estimated to take up 10.9 kg CO2/yr. Over the 20 years it takes for a forest to mature, this amounts to 218 kg CO2 taken up per tree.

For more detail on how we have calculated the carbon offset by the trees, refer to our CO2 Offset Programme: Aims, Objectives and Methodologies Manual. For more information on calculating carbon uptake and release from changes in land use, go to the Intergovernmental Panel on Climate Change's publications.

Flight Route Domestic/Short/Long Distance kgCO2/pkm +9% uplift factor (kg)
London to Marseille Short 959 125 136
Marseille to Antananarivo Long 8143 854 921
Antananarivo to Diégo Suarez Domestic 763 121 132
Total (one way) 9865 1100 1189
Total (return) 19730 2200 2378