Vehicle emission forecasts pinpoint CO2, NOx as problem pollutants

Emissions of carbon dioxide from the EC's vehicle fleet are unlikely to fall below 1990 levels by the end of the century, according to forecasts prepared for the European Commission.1 And a combination of best available technology and official vehicle inspection and maintenance standards will have to be implemented by the mid-1990s if emissions of most other major air pollutants are to be cut significantly.

The forecasts were compiled for the Commission by German and Greek consultants. Their original purpose was to show whether the EC as a whole could comply with the 1988 UN Economic Commission for Europe protocol on nitrogen oxides. This requires signatory countries to stabilise their NOx emissions at 1987 levels by 1994, with reductions to follow thereafter. Future trends in vehicle emissions, which accounted for 55% of the EC's total NOx emissions in 1985, will clearly influence the EC's ability to meet the protocol.

The forecasting exercise has gained added significance following the agreement by Environment Ministers in 1990 that the EC should aim to stabilise its carbon dioxide emissions at 1990 levels by 2000. Vehicles account for 18% of the EC's total CO2 emissions, and the figure is growing in both absolute and relative terms.

The forecasts were based on a methodology initially agreed by national experts for estimating road traffic emissions for 1985. The figures for the EC as a whole are shown in the table.

The Commission's consultants then developed five scenarios incorporating different assumptions about the growth in vehicle fleets, vehicle usage patterns, emission controls and fuel consumption. The key results were as follows:

  • In a baseline scenario A, vehicle numbers were extrapolated to 2000 from trends over the past 15 years, and new vehicles were assumed to meet emission limits due to be phased in between 1993-6 under existing EC legislation for cars and heavy duty vehicles.

    In this scenario, CO emissions are projected to fall steadily to just 45% of 1985 levels by 2000, while smoke and SO2 emissions, after peaking in 1995, are projected to decline sharply following a cut in the sulphur content of diesel in January 1996. VOC emissions, after stabilising at 1985 levels by 1992, are projected to decline by 40% by 2000.

    But the forecasts for NOx and CO2 are more pessimistic. NOx emissions are projected to rise to 10% above 1985 levels by 1992, and then to decline slowly to just 5% below 1985 levels by the end of the century. And for CO2, a steady rise culminating in an increase of almost 30% above 1985 levels by 2000 is forecast.

  • The introduction of emission standards for light trucks, together with mandatory car inspection programmes to ensure that engines and catalytic converters were properly maintained, would bring about a modest improvement, the forecasts suggest. Compared with the 1985 baseline, CO emissions would fall by 65% and VOC emissions by 50% by 2000 if these measures were phased in from 1996.

    However, CO2 emissions would rise by 30%, and NOx emissions would be cut by only 10%.

  • In a scenario C, it was assumed that the best emission control technologies available now or in the near future would be phased in from 1996-8. These include tighter emission standards for cars and trucks, changes in petrol quality to reduce evaporative VOC emissions, and cuts in the fuel consumption of new vehicles of 10-15% from 1996, as well as mandatory vehicle inspection and maintenance programmes from 1993.

    These measures would bring sharper reductions in CO and VOCs, as well as a 30% cut in smoke emissions by 2000. However, NOx emissions would still fall to only 10% below 1985 levels by 2000, while CO2 emissions would be slightly above 1985 levels, though about the same as 1990 levels, by then.

  • The most pessimistic of the five scenarios assumes that vehicle numbers increase by 15% above the baseline case by 2000, with car mileages and urban traffic increasing by 15% and average speeds falling by 15%. Emission controls would be the same as in scenario A.

    In this scenario D, emissions of all the main pollutants except VOC and CO are projected to be higher in 2000 than in 1985. CO2 emissions are some 70% higher, and NOx emissions 20% higher.

  • The most favourable scenario makes assumptions obverse to those in scenario D, with vehicle numbers being 15% smaller in 2000 than in the base case, and accompanying 15% reductions in mileages, urban traffic, and trip length. Even so, CO2 emissions are projected to be only about 10% lower, and NOx emissions less than 30% lower, in 2000 than in 1985.

    Overall, the forecasts underline how difficult it will be to achieve major inroads into NOx and CO2 emissions without further improvements in emission control technology, new EC measures to improve the fuel efficiency of vehicles, and a concerted effort of the kind outlined in the Commission's recent Green Paper on transport and the environment to shift traffic off the roads (ENDS Report 205, p 33 ).

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