UNUnited Nations Economic Commission for Europe

Press Releases 1996

[Index]
TACKLING AIR POLLUTION FROM LAWNMOWERS TO JUMBO JETS

28 November 1996

Fourteenth session of the Executive Body for the UN/ECE Convention on Long-range Transboundary Air Pollution (25-28 November 1996)

"The world's current fleet of 400,000 aircraft is responsible for 2 to 3% of our planet's air pollution. This share may very well double or triple by the year 2015", says Mr. Lars Nordberg of the United Nations Economic Commission for Europe (UN/ECE). The combustion of aviation fuels gives off carbon dioxide (CO2), water (H2O) in the form of vapour, and sulphur dioxide (SO2). It also generates a number of other pollutants, such as carbon monoxide (CO), volatile organic compounds (VOCs) and particulates. Moreover, the high temperatures in the combustion chamber lead to the formation of nitrogen oxides (NOx). The Executive Body for the Convention on Long-range Transboundary Air Pollution addressed this growing problem, at its fourteenth session from 25 to 28 November 1996.

The Protocols to the UN/ECE Convention on Long-range Transboundary Air Pollution already recommend specific technologies to control the emissions from traffic, but until now these recommendations have dealt almost exclusively with road vehicles, such as cars, mopeds, and lorries.

Now the Executive Body for the Convention is increasingly turning its attention to other sources of emissions, such as tractors, construction equipment, lawnmowers, ships and aircraft. And consultations have been held with the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO). This has become necessary because the pollution that these mobile sources cause is increasingly contributing to acidification, tropospheric ozone formation and other environmental and health problems.

In the ECE region emissions from off-road vehicles and machines account for 10 to 20% of total NOx emissions. Diesel-fuelled engines are the biggest culprit. But it is now technically feasible to cut emissions from diesel engines at reasonable cost. Some of the new technical options for diesel-fuelled engines are: better combustion chamber design, exhaust-gas recirculation, electronic engine management and better injection systems. Emissions from off-road vehicles and machines also account for up to 10% of total emissions of volatile organic compounds (VOCs) in the ECE region. Here, petrol-fuelled two-stroke engines are the biggest polluters.

Estimates have shown that, for a 500-km journey, the emission of CO2 per passenger-kilometre (pkm) is the lowest for buses (22 g/pkm) and the highest for planes (146 g/pkm), while high-speed trains and private cars emit 48 g/pkm and 86 g/pkm, respectively. Buses and planes are the biggest emitters of NOx (479 mg/pkm and 440 mg/pkm); private cars and high-speed trains emit much less NOx (between 145 and 270 mg/pkm and 87 mg/pkm).[Data transmitted by the Government of the Netherlands.]

On average, the complete combustion of 1 kg of jet A1 aviation fuel has been estimated to generate about 3.16 kg of CO2, 1.25 kg of H2O and 1 g of SO2. Estimates of fuel sales to airlines suggest that this would amount to more than half a billion tons of CO2 and some 2 million tons of NOx emitted each year by aircraft worldwide. 94% of these emissions occur in the northern hemisphere, mainly in North America (44%) and Europe (30%). Most occur at an altitude of 9 to 13 km. It has been estimated that 44% of all fuel is consumed above the tropopause - the limit between the troposphere and the stratosphere. Civil aviation is responsible for most of this air pollution, but military aviation also plays a significant role. The impact of light aviation is mainly local.

There are several options for reducing aircraft emissions. There are technical options, such as measures to improve the engines; operational options, which concern the method of operating the craft; and economic instruments, i.e. green taxes or other charges that encourage a more environmentally friendly attitude. To cut emissions the Executive Body of the Convention on Long-range Transboundary Air Pollution is proposing measures to make engines less polluting. However, as engines have a long lifetime (almost 30 years for aircraft engines), new technology penetrates slowly. So it is important to try and upgrade or "retrofit" old engines, as well as to make new ones cleaner.

To this end, the Executive Body has decided to amend some technical annexes to its NOx and VOC Protocols. These will in future recommend specific technical solutions to reduce emissions from mobile sources such as off-road vehicles, ships and aircraft and give an idea of their cost.

"The amendments to the NOx Protocol will come into effect in a month's time; the amendment to the VOC Protocol cannot come into force until the Protocol itself has been ratified by 16 Signatories", confirms Mr. L. Nordberg.