General Mukul Rohatgi has claimed in the Supreme Court that big cars cause less pollution than small ones. However, car manufacturers do not share the emissions profile of their vehicles so there is no way to ascertain that.
What is more, technology treatments that allow certain big cars to be cleaner than their smaller compatriots are not available here as they need ultra-low-sulphur diesel that is not yet commercially available in the country.
The Centre claimed that high-end and big diesel cars pollute less than small cars while challenging the court’s blanket ban on fresh registration of SUVs and diesel luxury cars with over 2000 CC engine capacity in Delhi.
Attorney General MukulRohatgi told the court that expensive cars are better equipped against pollution and just because a car is powerful and big, it does not mean that it is more polluting.
Research proves that if a big diesel car employs specific exhaust treatment technologies it can cut down nitrous oxide emissions as compared to a small car. In Europe, cars equipped with Selective Catalytic Reduction (SCR) module cost about Rs.7,500 more than those with nitrogen trap and Exhaust Gas Recovery (EGR).
Problem is that SCR, which is scheduled to be mandatory for the forthcoming Euro 6 norms in 2020, and even EGR are assumed to be effective only if they employ diesel that has sulphur content less than 50 parts per million. In India, oil companies have yet to put in the infrastructure to produce such diesel.
Norms in India
Diesel engines are now criticized globally for being a source of particulate matter and nitrous oxide which worsen several lung diseases. They can vary in the quantity of particulate matter they emit.
In India, diesel engine cars are required to ensure they emit no more than 0,06gm/km of particulate matter if they are “big” or 2000 cc-and-above and 0.025gm/km if they are “small”.
Again depending upon the weight class, the same cars are allowed to give off roughly 10 times more nitrous oxide emissions. This explains the paradox of pollution by diesel engines. All the same, a diesel engine burns fuel more efficiently as compared to a petrol engine.
While this could mean less particulate matter, but it substantially steps up nitrous oxide levels. Conversely, trying to rein in nitrous oxides will compromise fuel-use efficiency and enhance particulate matter emissions.
Toyota, Mercedes, Volkswagen cars are equipped with particulate filters abroad. But they are not available in their Indian versions.
After mulling over the facts, the claim that big cars are cleaner does not seem to be true, but new inventions to manufacture cars are essential to curb pollution level.