Diesel cars are known to produce higher levels of some pollutants than petrol cars, in particular very small particulates and nitrogen oxides. However, tough new EU standards applicable to both engine types from 2000 are expected to significantly reduce emissions. In addition, diesel engines are widely seen as contributing less to global warming than petrol versions because they are 20-25% more fuel efficient.
According to the Swedish EPA, though diesel cars have been made considerably cleaner over the last ten years, improvements in petrol-driven cars from exhaust emission control technology have far outstripped this trend. The agency calculates that emissions from new cars of nitrogen oxides will double and particulates will both more than double if current diesel sales trends are maintained.
"It's not enough that we have [the new EU] limits for 2000 and 2005," an agency official told ENDS Daily. "In Sweden we have to come down more. Higher nitrogen oxides, particulates and carcinogenic [substances] emissions levels from diesel...are hampering our national environmental goals. We have long-term goals and they are not being met."
The study was launched in response to growing sales of diesel cars in Sweden, which reached 15% of new car sales this year compared with 1% at the beginning of the decade. Similar trends is also apparent in other EU countries. Diesel car sales in France exceeded 50% for the first time recently, prompting calls by environment minister Dominique Voynet for diesel tax benefits to be withdrawn.
The Swedish EPA backs up its argument for cutting sales of diesel cars by challenging conventional wisdom about their carbon dioxide emissions and therefore their contribution to global warming. Advertisements for diesel cars "put great stress" on their fuel efficiency, the agency says. But carbon dioxide emissions per litre of diesel are actually 15% higher than for petrol, it says, and therefore increasing diesel car sales from 1% to 20% would only cut total CO2 emissions by a "negligible" 1-2%.
An official from the European car manufacturers' association Acea responded that making comparisons between new diesel and petrol cars was "very difficult and very delicate". He said that new catalyst technology was under development that would further reduce diesel car emissions.
Swedish EPA, tel: +46 8 698 1000.
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