If 33% of new petrol cars purchased were replaced by diesel versions, bringing Ireland into line with the rest of Europe, our emissions would be 7.4% lower.
Given that transport is the third-biggest contributor to greenhouse gases, the findings could help the government reduce Ireland’s likely penalties for breaching its Kyoto emissions targets.
But a switch to diesel cars is unlikely unless vehicle registration tax (VRT) is changed. It penalises larger-engined diesel cars, even though they emit less CO2. Transport accounted for 18% of CO2 emissions in Ireland in 2004.
“The decrease of CO2 emissions is one way to minimise climate changes. An efficient way to decrease emissions is the replacement of gasoline passenger cars by diesel ones,” said Efthimios Zervas, a chemical engineer based at Renault in France, who analysed the Irish car market.
“Most of the member countries of the European Union have high percentages of new diesel car registrations; but this remains less than 17% in Ireland,” Zervas says in the Energy Policy journal.
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“A CO2 benefit of more than 2.9% can be achieved if a diesel penetration higher than 30% occurs in the current fleet. If penetration reaches 50%, this benefit will be higher than 7.4%.”
The percentage of new diesel cars averages 40% in all EU countries, and reaches 60% in Spain and France. Ireland’s low diesel uptake is mainly because the cars attract higher rates of VRT than their petrol equivalents.
Diesel versions of cars require a larger engine than the equivalent petrol model to ensure adequate performance. Many diesel cars’ engines are greater than 1.9 litres in size, meaning they are hit with higher VRT and road tax than similar petrol models.
“Our tax system punishes higher cc [cars], through VRT and road tax,” said Cyril McHugh, of the Society of the Irish Motoring Industry (SIMI). “The government could encourage a reduction in CO2 by encouraging diesel sales. Other markets have shown if there was such an encouragement, the market would adjust very quickly. At some stage the government is going to have to make a portion of VRT CO2-related. Some effort should be made to give reduced road taxation to diesel.”
Conor Faughnan of the Automobile Association (AA) said basing VRT and road tax on engine size was too crude a measure. “It would be more reasonable to base it on volumes of emissions. There is no doubt the current way is a disincentive [to buy diesel cars] because a diesel engine needs to be larger to give the same power, ” he said.
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Ireland’s greenhouse gas emissions in 2004 were up by 0.15% on 2003 levels, reaching 68.5m tonnes of CO2 equivalent. The emissions were 23% higher than in 1990.
Ireland is committed under the Kyoto Protocol to limit emissions to 13% above the 1990 level in the period 2008-12.