Diesel: no answer to global warming

Published: Thursday 30 September 1999

Diesel: no answer to global warming

Whenever the issue of urban smog due to diesel exhaust emissions is raised, auto companies vie that diesel is the answer to reducing emissions of carbon dioxide (CO 2 ), the main greenhouse gas. But the last bastion of the powerful diesel lobby collapsed with a new study saying that though it takes less diesel to run a vehicle per km, it still does not help save fuel and control carbon emissions. The study is from France, where almost every fourth car is diesel-fuelled. It explodes the myth that diesel -- promoted in many European countries to help cut CO 2 emissions -- is actually no energy saver or a solution to the global warming problem. Moreover, policy to keep diesel cheap will only increase its consumption in volume and exceed the small advantage it enjoys over petrol.

These are the findings of Diesels in Europe: Energy saving or Energy waste? , a study conducted by Lee Schipper and Celine Marie-Lilliu of International Energy Agency, Paris, France, for the US Department of Energy. The study includes an analysis of the typical use pattern of diesel cars in five European countries. It studies the intensity of vehicle use, distance travelled, average engine size and other vehicle characteristics. It shows that diesel cars actually "lead to greater, not lower energy use, principally because diesel fuel is priced significantly below gasoline".

The most dramatic conclusion is that CO 2 emissions per km from both diesel and petrol cars differ by less than 10 per cent in the five European countries they included in the study. With this small difference in CO 2 emissions and higher kilometrage for diesel cars, the total CO 2 emissions from a diesel car per year is actually higher than a petrol car. Thus, one diesel car in France emits 3.8 tonnes CO 2 per year as opposed to 2.2 tonnes from a petrol car.

The researchers say that apart from the potential gains in fuel economy that diesel vehicles offer over petrol vehicles, the European experience actually suggests very little real fuel savings. The researchers found that low prices of diesel across Europe mean that diesel vehicles, on an average, are driven 40-70 per cent more than petrol vehicles. The study also shows that drivers of diesel vehicles prefer engines that are fuel guzzlers -- heavier and larger than petrol versions. So, the authors raise a question: "Are drivers buying fuel savings or just money savings?"

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