Air Freight – what’s the problem?


Air cargo was, until the recession, rising faster than passenger traffic at some airports, and much of the development at ever expanding airport sites is cargo related. 
Air freight has far higher negative environmental impacts, including greenhouse gas emissions, than other modes of transport.  Air freight produces immensely more CO2 equivalent emissions per tonne kilometer than transport by rail or by sea. See calculations below, using the DECC  conversion factors.
Air freight often uses older, more polluting and noisier planes, and much is transported at night.  The aviation industry hopes that, when the recession ends, the freighter fleet will double over the next 20 years, and as larger planes are being built, this will mean a tripling of air cargo.  
Air cargo rose by 30% in the UK between 1997 and 2007.   East Midlands is a key UK cargo airport, with 50 flights a night and with ambitious expansion underway this is expected to double by 2016.  Other UK airports with growing freight operations include Manchester, Kent, Bristol and Belfast.  
Which UK airports handle the most freight? The top 5 are:
 Heathrow  (massively more than other airports, mainly belly freight)                        2  East Midlands      
3  Stansted                                
4  Manchester   
5  Gatwick

Air freight in the UK in 2010

These were the top 11 airports for air freight.   (tonnes)  
Airport Name                    2010 tonnes            % change from
HEATHROW                         1,472,988                     + 15
EAST MIDLANDS                    273,669                     + 7
STANSTED                              202,238                     + 11
MANCHESTER                       115,922                     + 13
GATWICK                                104,032                      + 39
BELFAST INTERNAT               29,716                       0
LUTON                                       28,743                       0
MANSTON (KENT INT)           28,103                      – 6
BIRMINGHAM                            21,605                     + 65
EDINBURGH                             20,357                     – 14
PRESTWICK                             12,163                      – 9
Total of all reporting UK airports in 2008 =  2,324,822 tonnes – (+ 14% more than in 2009)

Air Freight carbon emissions compared to other transport modes

There is a DEFRA /DECC report entitled:

“2011 Guidelines to Defra / DECC’s GHG Conversion Factors for Company Reporting”

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 ari 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.
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).
Page 30  Annexe 7  Freight Transport Conversion Factors
The figures include not only CO2 but also Ch4 (methane) and NOx. Adding all these together gives the total direct Greenhous Gases (GHG) and indirect * GHG as well as Grand Total GHG in kg CO2-equivalents per tonne kilometer.
Using the  Grand Total GHG figures of:
2.079 kg CO2-e per tonne km     for domestic flights
1.596  kg CO2-e per tonne km     for short haul international flights
0.727  kg CO2-e per tonne km    for long haul international flights
0.015  kg CO2-e per tonne km  for a general cargo ship    (Page 31)
      (there is a large range of ship types and sizes)
By comparison, for other modes of freight transport
0.005 kg CO2-e per tonne km  for Diesel / Electric rail
0.834  kg CO2-e per tonne km  average petrol
0.637  kg CO2-e per tonne km  for average diesel    (page 27)
*  Indirect emissions associated with the extraction and transport of primary fuels as well as the refining, distribution, storage and retail of finished fuels

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

Some calculations showing emissions from air freight compared to other modes of transport:

For example,

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

 2,000    x   2.079   x   1.09     =  4,532  kg CO2


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

10,000    x   0.727   x 1.09     =   7,924 kg CO2



Freight by Diesel or electric train:

By comparison, the DECC 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    0.005    =   10  kg CO2    (compared to 4,532 kg CO2 for the plane, as above)



Average cargo ship:

By comparison, the DECC figure for freight carried in an average cargo shipis 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 4,532 kg CO2 for a UK  flight)


2 tonnes carried for 5000 kilometres is:

10,000    x   0.015      =     150 kg CO2 (compared to   7,924 kg CO2 for the plane)



So in Summary:

2 tonnes of freight carried 1,000 km produces:

by air                       –  4,532 kg CO2-e

by diesel train         –    10  kg CO2-e   

by cargi ship        –    30  kg CO2-e 




2 tonnes of freight carried 5,000 km produces:

by air                    –    7,924 kg CO2-e

by container ship   –     150 kg CO2-e