Diesel cars emit five times more harmful particulate matter than petrol cars, and they’re even legally allowed to emit three times more NOx (nitric oxide and nitrogen dioxide) compared to petrol-based vehicles.

Apart from releasing more PM, the emissions factor of the Automotive Research Association of India (ARAI) shows that diesel cars release seven times more total air toxins compared to petrol cars. As per a draft report by IIT-Kanpur, commercial vehicles, which mostly run on diesel cause 46 per cent of all vehicular pollution in Delhi. Vehicular emissions account for 30-40 per cent of all air pollution, as per the draft report which was presented in the Delhi Government on Wednesday.

With the Supreme Court’s decision on Wednesday to curb the use of diesel vehicles, environmentalists say air quality in the Capital is bound to improve and public health will also get a boost. Diesel emissions have been classified by the World Health Organisation as a group-I carcinogen for the strong link with lung cancer. But, diesel isn’t the same devil around the world as it is in India.

“As per standards in Europe and the United States, there is hardly any difference in emissions from petrol and diesel. At Euro-VI, the difference melts away,” said Ashwani Kumar, the Secretary of the Delhi Government’s Environment and Forest Department.

While welcoming the Supreme Court’s decision, Mr. Kumar said there was a need to boost clean energy solutions, which the government was planning on. Tutu Dhawan, an auto expert, said diesel was “the fuel of the future” in other parts of the world.

“Diesel at Euro-VI norms is more refined and fuel efficient. The move to ban registrations of diesel vehicles will hit the common man and the auto-mobile industry, though I agree with the move towards CNG for cabs,” said Mr. Dhawan.

Meanwhile, AnumitaRoychowdhury, of the Centre for Science and Environment (CSE), noted that the Supreme Court had scheduled a hearing for longer-term solutions, including leapfrogging emissions standards for vehicles to Euro VI. The court will also look into introducing BS-IV, the current emission standards in Delhi, nation-wide immediately, action on power plants, and public transport strategy for Delhi and NCR.

The CSE has long demanded an additional tax on diesel cars to reduce public revenue losses and public health costs, alleging that with each litre of petrol replaced by diesel, the government’s excise earnings drop seven times.

Ms. Roychowdhury said: “The effect of the increased use of diesel in cars is so dramatic that the excise earnings from both diesel and petrol has nearly equalled. We found that the new diesel car fleet were to pay the same excise as that of petrol cars, the potential excise revenue can be Rs.100,000 crore from the lifetime fuel use of the new car fleet to be sold between 2009 and 2015.”

S.P. Singh, whose Indian Foundation of Transport Research and Training (IFTRT) had been calling for a ban on diesel vehicles since April this year, said the court’s decision went only half-way.

“There should be a total ban on registration of diesel cars in the National Capital Region. People know how to get around regulations, they can just get the cars registered in the NCR,” said Mr. Singh, senior fellow at IFTRT.

He added that most taxis in the NCR were diesel-based, and that policies over the years had contributed to the spurt in diesel vehicles.

“Apart from SUVs being a status symbol, there had been pressure from the automakers. The Supreme Court’s decision needs to be implemented properly to have a real effect on air pollution,” he said.

For about 35,000 cab drivers in the NCR, the Supreme Court’s decision brought bad news. In Gurgaon, there are an estimated 6,000 registered cabs in and more than 90 per cent of them are diesel-run and cannot be converted into CNG.

“Only petrol-run vehicles can be converted into CNG. With most diesel vehicles being bought with huge loans, the owners would be incurring heavy losses in the wake of the court directions. Even if they sell these vehicles, they would not fetch a good price,” said Jitender Kumar, who runs Gaurav Travels Limited cab service.

Jitender, who owns five cabs, added that the court should have banned the registration of diesel cabs from a cut-off date in the future, instead of making it mandatory for the already registered vehicles to convert to CNG.

Rajiv Yadav, who runs Golden Tours and Travels agency in Gurgaon, said: “I recently bought five diesel-run vehicles, including two Multi-Utility Vehicles, against a loan of over Rs.30 lakh. The court direction has left me in the lurch. If the cabs are not allowed to ply, how will I repay the loan?”

He also said that the infrastructure in terms of CNG stations was inadequate in Gurgaon. “There are just half-a-dozen CNG stations which are not enough even for the existing vehicles. If all cabs are converted into CNG, as the court said, we will need at least 30-40 CNG stations.”

Qutab Automobiles general manager Juber Khan said that the installation cost of CNG kits into post-2009 vehicles ranged from Rs.30,000-50,000.

‘As per standards in Europe and the US, there is hardly any difference in emissions from petrol and diesel’