Carbon emissions of air freight compared to other modes of transport

5th October 2011
DEFRA produced some conversion factors, to estimate the carbon emissions from air freight, and other forms of transport.  There is a difference between estimates for cargo flown in dedicated freighters, compared to cargo flown in the bellies of passenger planes.  The latter creates a difficult exercise in apprortioning the carbon between passengers and load.  
More information on the DEFRA figures below.

Carbon emissions of air freight compared to other transport modes

There is a DEFRA report entitled:
“2008 Guidelines to Defra’s GHG Conversion Factors: Methodology Paper for Transport Emission Factors – July 2008”
This gives the conversion factors used to estimate carbon emissions from various forms of transport, including air freight.  There is a difficulty in calculating the carbon emissions caused by air cargo carried as belly freight, in passenger planes.  The document goes into this in some detail.  Emissions from dedicated air freighters are simpler to calculate.
DEFRA produced some figures in 2005, to estimate the carbon emissions from air freight, giving conversion figures for domestic, short haul and long haul traffic.   These were re-done in April 2008, and a new document produced.  It can be found  at: 

The air freight figures are on Page 15.


The way that total kilograms of CO2 are calculated is by multiplying the total tonne kilometres (eg.  2 tonnes of cargo being transported 3,000 kilometres – 6,000 tonne kilometres) x a figure calculated by DEFRA for the kilos CO2 per tonne kilometre x a kilometre uplift figure (the IPCC requires this, to take account of the fact that planes will not fly in a straight line, my have to stack and circle before landing, and other ways in which more fuel is used – the figure is estimated to be another 9%).  The total gives the kilos of CO2 that have been produced in flying the cargo.


There are different conversion factors for domestic, short haul (under 3,700 kilometres) and long haul flights, to take account of the proportion of the flight that is take-off and landing (when more fuel is used that while cruising at altitude).


                      Total tonne        kg CO2 per      km uplift
km travelled   x   tonne km    x   factor        =  Total kg CO2

Domestic                                                       x 1.898            x 109%      =
Short-haul international                                    x 1.316            x 109%       =
Long-haul international (over 3,700 km)             x 0.606            x 109%       =


Air freight:

So, for example,

2 tonnes carried by air on a domestic flight for 1,000 kilometres within the UK is:

 2,000    x    1.898   x   109 %     =  4,138 kg CO2



2 tonnes carried by air on a long haul flight for 5000 kilometres is:

10,000    x   0.606   x 109%       =   6,605 kg CO2




Freight by Diesel train:

By comparison, the DEFRA figure given for freight carried by a diesel train would be a conversion factor of 0.021 kg CO2 per tonne kilometre. 

Eg.    2 tonnes carried for 1,000 kilometres is:


 2,000    x    0.021    =   42  kg CO2    (compared to 4,138 kg CO2 for the plane, as above)




Small container ship:

By comparison, the DEFRA figure for freight carried in a small container ship (deadweight  2,500 tonnes) is 0.015  kg CO2 per tonne kilometre  (or a small bulk carrier it is 0.011)


So, for example,


Eg.    2 tonnes carried for 1,000 kilometres around the UK is:


 2,000    x   0.015     =  30  kg CO2  (compared to 4,138 kg CO2 for a UK  flight)



2 tonnes carried for 5000 kilometres is:

10,000    x   0.015      =     150 kg CO2 (compared to   6,605 kg CO2 for the plane)





So in Summary:


2 tonnes of freight carried 1,000 km produces:


by air                     –  4,138 kg CO2

by diesel train         –    42  kg CO2   

by container ship    –    30  kg CO2 




2 tonnes of freight carried 5,000 km produces:


by air                    –  6,605 kg CO2

by container ship   –     150 kg CO2