"NGT has concluded that diesel vehicles are more polluting than petrol and CNG. Government has submitted that there are various pollutants that cause air pollution from vehicles.
"Diesel may be inferior to petrol in some pollutants such as particulate matters and oxides of nitrogen, but petrol is also inferior to diesel in some other pollutants. Hence, the misconception that only diesel is a polluting technology or fuel," Additional Solicitor General Pinky Anand told the NGT.
Opposing the ban on 10-year-old-diesel vehicles, the Ministry of Heavy Industries told the tribunal that diesel was not the only polluting fuel as they have higher fuel efficiency which leads to 10-15 per cent lower carbon dioxide emission compared to a petrol vehicle.
"Assuming a 10 per cent lower carbon dioxide emission for diesels, diesel passenger vehicles in India's fleet would have saved over 1.5 million tons of carbon dioxide emissions a year, thereby significantly helping in the commitment of reducing the country's emissions intensity per unit GDP by 33 -35 per cent below the 2005 level by 2030 at 21st Conference of Parties at United National Framework Convention on Climate Change," Ms Anand said.
The ASG also referred to the Delhi government's odd-even road rationing scheme and said that Central Pollution Control Board unequivocally establishes that pollution levels did not come down due to reduction in vehicles.
"Report of CPCB shows unambiguously that on diverse locations in Delhi on a sample basis, the PM emissions levels not only did not come down, during the full operation of odd even scheme but was measured to be significantly higher during this period, in contrast to periods when there was no odd even scheme in operation and when the number of vehicles on Delhi roads was bound to be higher.
"That vehicles generally make a significant difference to PM emission levels in ambient air quality level is both misleading and over simplistic," she told a bench headed by NGT Chairperson Justice Swatanter Kumar.
The ASG also pointed to report published by Central Road Research Institute in 2002 and said it clearly mentions that the average age of cars plying in the city of Delhi was between the age of 5-6 years and, hence, the vehicles of 10-15 year old vintage were seldom used and their contribution to air pollution of Delhi was minuscule.
Advocate Saliq Shafique, appearing for Vardhaman Kaushik who has filed the case against deteriorating air quality in Delhi-NCR, contested the submissions of the ASG and said that diesel vehicles were primary contributors to air pollution.
The bench, after hearing the arguments from various parties, reserved its verdict on the plea filed by the Centre seeking modification of NGT's order banning diesel vehicles.
On January 13, the Centre had moved the Supreme Court seeking lifting of the ban on 10-year-old diesel vehicles in Delhi and NCR, saying it was affecting the economically weaker sections.
Noting that diesel is the prime source of air pollution in Delhi, the tribunal had held on November 26, 2014 that all diesel vehicles which are more than 10 years old, will not be permitted to ply in Delhi-NCR.