Why is the Diesel Ban Important?

The Odd-Even experiment is long gone but the Supreme Court of India has ordered that the ban on registration on new diesel vehicles with an engine capacity more 2000cc must remain till April 1, 2016.

This ban follows more or less the same logic as the Odd-Even experiment; it is centered around the degrading air quality in Delhi. But it is more than just this debate, and that is where the ban becomes important. The plea to remove the ban was put forward by leading automobile manufacturers such as Mercedes, Toyota and Mahindra & Mahindra. The idea being put forth is that new diesel engines do not pollute more than petrol engines because they are designed based on a “new technology”.

Diesel-driven vehicles account for over 90 per cent of SUVs in the country, 34 per cent of small cars and 70 per cent of large/medium cars. With so many diesel cars on the road, and the exponential increase in the market in recent years, they are under scrutiny for good reason.

Although, traditional literature claims that diesel engines pollute less, that isn’t exactly the case. Diesel engines emit lesser carbon monoxide, carbon dioxide and hydrocarbons. However, they produce more particulate matter than petrol engines. Most diesel engines now use catalytic converters for engine efficiency (and reduced emissions). The converter is most efficient at temperatures above 250 degrees Celsius. Here lies the second problem; most vehicles don’t achieve the 250 degrees needed by the catalytic converter. Which is probably why a report from the Norwegian Centre for Transport Research found that a modern diesel car pumps out more toxic pollutants than a bus or heavy truck.

The amount of time it takes for the diesel engine to warm up to that level is mostly only achieved by buses. And buses don’t use catalytic converters.

Another factor to examine is the quality of diesel fuel with respect to the amount of Sulphur, which is often much higher than acceptable.

Though most manufacturers claim that diesel engines are fitted with an exhaust re-circulation system (to burn partially burnt exhaust from the engine and reduce emission), the system itself is pretty expensive. Most manufacturers also wouldn’t make a profit by designing engines with higher injecting pressures.