ENVIRONMENT: Planes Lead Vehicle Contamination Ranking

By Gustavo Capdevila Reprint | | Print |

Gustavo Capdevila

GENEVA, Nov 28 1996 (IPS) - Q: What is the difference between an old banger, a steaming coffee pot, and a jet zipping through the sky? A: That the jet emits nearly twice the amount of contaminating gases.

The present world fleet of 400,000 commercial planes is responsible for between two and three percent of the air pollution in the world, said Lars Nordberg, of the European Economic Commission for the United Nations (EEC/UN).

The mass of polluting gases left in the sky by planes will have doubled or even tripled by 2015, said Norberg, subdirector of the EEC/UN Environment and Human Settlement section.

Some elements of the phenomenon are constants. One of them is that all internal combustion engines contaminate the air, be it a lawnmower or a transatlantic jumbo jet.

Another rule, at least under the present economic distribution, is that the contaminating chimney of aeroplane emissions stands in the Northern hemisphere.

Some 94 percent of emissions are registered in flights over the Northern hemisphere. Europe produces 30 percent and North America 44.

The burning of aviation fuel releases carbon dioxide, water vapour and sulphur dioxide.

It also generates many contaminants of other types, like carbon monoxide, volatile organic components and other particles.

Meanwhile, the elevated temperatures in the combustion chamber lead to the formation of nitrogen oxides.

The problem of controlling emissions from vehicles has been administered by the Convention on Long Distance Transfrontier Contamination of the Air.

But the protocols of this EEC/UN convention have until now only established recommendations for road vehicles, cars, motorbikes and transport vehicles.

The Convention Executive Council, which ended its 14th session in Geneva Thursday, decided to turn its attention to other sources of emissions, like tractors, construction vehicles, boats, planes and even lawnmowers.

The organism consulted with the International Civil Aviation Organisation and the International Maritime Organisation.

Contamination from these two types of vehicle contribute to acidification, the formation of tropospheric ozone and other environmental and health problems.

In the region covered by the EEC/UN, emissions from non-road vehicles represent between 10 and 20 percent of the total nitrogen oxide emissions. Most of this is down to Diesel engines.

But current technology means it is possible to reduce Diesel motor emissions at a reasonable cost.

Some of the options are: better design of the combustion chamber, the recirculation of the exhaust gases, the electronic operation of the motors and better injection systems.

Estimates indicate that for a 500 km journey, the per passenger/km (pkm) emission of carbon dioxide is lowest in buses, at 22g, and highest in planes, 146g.

High speed trains emit 48g/pkm and private cars 86.

Buses and planes are the main emitters of nitrogen oxide, at 479mg/pkm and 440mg/pkm respectively. Cars and trains are much cleaner in this respect, at between 145 and 279mg/pkm and 87mg/pkm.

On average, the full combustion of a kilogramme of A1 aviation fuel generates around 3.16kg of carbon dioxide, 1.25kg of water and a gramme of sulphur dioxide.

Estimates of the volume of fuel sales to the air companies indicate that worldwide, planes emit half a million tons of carbon dioxide each year and some two million tons of nitrogen oxide.

Most of the plane emissions occur at altitudes of between nine and 13 kilometres. It has been estimated that 44 percent of the fuel is consumed on the border between the troposphere and the stratosphere.

Civil aviation is responsible for the majority of air contamination, but military planes also play a significant role. The effect of light aircraft is only seen in the local area.

The reduction of plane emissions can be achieved via technical measures like the improvement of motors, or operations, related to how the machine works.

Economic decisions can also be made, like environmental taxes or other tariffs which stimulate more ecological attitudes.

The Convention Executive Council propose to reduce emissions by producing motors which pollute less. However, motors have a long life – nearly 30 years for planes – meaning the new technology takes time to take over.