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Is Diesel Really Polluting Environment?

CNG vehicles, which are regarded by some as a safer option than diesel and petrol vehicles, come with their own drawbacks

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The crackdown on the use of diesel passenger vehicles in the national capital region and other parts of India has raised one big question - what is the future of diesel vehicles?

While the industry is focused more on the future of the investments they made when the market was looking promising for diesel vehicles, environmentalists are leaving no stone unturned to ban the use of diesel. However, the bigger question is whether diesel is really polluting the environment and if the selective ban on passenger vehicles will control the degrading air quality.

The study by IIT-Kanpur that is frequently cited by the industry in their pleas says that vehicles account for only 20 per cent of the particulate matter (PM) 2.5 pollution in Delhi and the other factors like construction work and industrial discharge account for the remaining 80 per cent.

The study adds that even in the 20 per cent vehicular pollution, the biggest contributors are the commercial vehicles. The passenger cars overall contribute to only 2 per cent of the PM 2.5 pollution load in the NCR. Out of this 2 per cent, all diesel cars are estimated to contribute only 1.5 per cent of the PM 2.5 pollution load. Further BS-IV diesel cars contribute only 0.5 per cent of PM 2.5 emissions.

A diesel car bought in Delhi in the recent past compared to one bought seven years ago when BS III was in place, emits 50 per cent less suspended particulate matter (SPM) and NOx and 20 per cent less carbon emission. When compared to BS II or BS I emission cycle, there is even more a stark difference. It is obvious now that new diesel cars pollute only a fraction when compared to the older ones.

This means that the selective approach made by the Supreme Court to put a ban on new vehicles which fulfil the existing norms and letting old vehicle(some of them as old as thirty years) won’t have any major impact on the air quality but is sure to impact investments in the country.

Is Diesel The Only Villain?

There is no denying the fact that diesel is a polluting fuel but which fuel is not, except a hydrogen fuel or an electric car. Petrol and CNG also emit pollutants that are harmful to human health and the environment.

Vishnu Mathur, director-general, Society of Indian Automobile Manufactures, says, "Petrol and CNG also cause harm to society. So why only put all the pressure on diesel engines?"

A diesel car emits 15 per cent less carbon dioxide than petrol car. Petrol cars also emit substances which are cancerous in nature. The total PM load coming from petrol run two-wheelers is more than that from diesel vehicles as their numbers are very large.

CNG vehicles, which are regarded by some as a safer option than diesel and petrol vehicles, have their own drawbacks. Drilling and production of natural gas leaks methane, a potent greenhouse gas and a major force behind global warming. Scientists at the Council of Scientific and Industrial Research (CSIR) say gases produced while burning CNG contain carbon nanoparticles that are suspected to cause cancer.

Environmentalists Believes Otherwise

The IIT Kanpur study has found alarming details on Delhi's air pollution, including the presence of polycyclic aromatic hydrocarbons (PAH), that are extremely toxic chemicals and a product of emissions from diesel-run vehicles among others.

Apart from PAH, the draft report, that has been submitted to the Supreme Court, identifies the sources of suspended particulate matter PM 2.5, namely road dust (38 per cent), vehicles (20 per cent), domestic fuel burning (12 per cent) and industrial point sources (11 per cent).

Anumita Roychowdhury, head of Centre for Science and Environment's (CSE), clean air campaign, said that even traces of PAH, which is anyway found in "very small quantity", can be extremely deadly and can reach harm to a foetus as well.

"PAH are toxic gases and a potent carcinogen, meaning exposure to them can cause cancer. It comes mainly from sources that use diesel as fuel which include diesel-run cars, gen sets, trash burning," she said.

What Judiciary Says

The Supreme Court in its hearing on May 10 said that it might impose a one-time "symbolic" cess on diesel vehicles if it decides to lift the ban on registration. The cess is expected to be around 30 per cent of the total vehicle cost.

The bench headed by Chief Justice T S Thakur said, "Primarily, we are of the view that diesel vehicles cause more pollution than other vehicles… We may impose a symbolic cess on any person who buys a diesel vehicle — this would be a one-time cess. What should be the scale, price, engine capacity is the thing to be deliberated upon. There has to be a rational basis to decide it.

Last heard, a National Green Tribunal hearing is underway where the topic of discussion is whether diesel engine cars should be banned in 11 other cities or not.

Some of the cities like Mumbai, Bengaluru and Hyderabad which may fall in the list are very big market for 2000cc plus passenger vehicles.