Note: * Non-Methane Hydrocarbon are a small fraction of total hydrocarbon in CNG vehicles
** Certificate from ARAI says particulates negligible and so for purposes of calculation we have used the lowest the machine could estimate.

References:
1. CPCB 2000, Environmental Standards for Ambient Air Automobiles Fuels and Noise, July, PCLS/4/2000-2001, p 20, p 29, p 37, New Delhi.
2. Ministry of Road Transport and Highways, The Gazette of India Notification, April 24, 2001, GSR 286 (E), New Delhi, mimeo.
3. J S McArragher et al 1999, Fuel quality, vehicle technology and their interactions, CONCAWE, Brussels, p 7.
4. Ashok Leyland 2001, Emissions certification data of ARAI, mimeo. (Annexure 1)
5. TELCO 2001, Emissions certification data of ARAI, mimeo.


By moving to CNG today, we can get emission levels comparable to Euro IV diesel vehicles as far as key pollutants are concerned.
The Mashelkar Committee does not even indicate when we will reach Euro IV norms, which will be introduced in Europe in 2004. According to Mashelkar, Euro III norms, introduced in Europe in 2000, will be mandated for metros in 2005 and for the entire country in 2010. Therefore, the Supreme Court order literally leapfrogs Delhi by many years.

In the case of particulates, diesel vehicles become comparable with CNG only with Euro IV emission norms, which would also mean the introduction of near sulphurless diesel (50-10 ppm or 0.005-0.001 per cent sulphur in diesel)


Current CNG vehicles are 15 times better than Euro II diesel vehicles (with 500 ppm sulphur) in the case of particulates.
Euro II diesel vehicles will continue to emit deadly particulates, while CNG vehicles have next to negligible particulate emissions. Furthermore, diesel particulates primarily because of PAH are toxic while CNG particulates are not.

Only in the case of CO (Carbon Monoxide) presently available CNG vehicles are below Euro III norms. But we must note that what we have on the road today are first generation CNG buses and we must insist with manufacturers to bring in better technology as fast as possible.


Do CNG vehicles emit particulates and are CNG emissions toxic?

The Union government argued in Court that CNG emits more ultrafine particles than diesel and is therefore, more toxic. The evidence it cited to prove this contention is the `study' done by the US-based Harvard Centre for Risk Analysis, which contends CNG vehicles emit more ultrafine particles than diesel vehicles. The "Harvard" study is a six-page pamphlet which is a literature survey with no references to the information cited. This was funded by Navistar International - the largest truck manufacturer in the world (Annexure 2).

Available scientific studies show that CNG vehicles emit negligible amount of particulates as well as ultrafine particulates but these are far less toxic than the diesel particulates. The reason is that while particulates come from all kinds of combustion sources it is the toxicity of the particulate emissions that help to prioritise its control. Particulate emissions from diesel vehicles are tiny -- over 90 per cent of the particulates emitted from diesel vehicles are less than 1 micron (PM 1) - and are coated with extremely toxic chemicals called polycyclic aromatic hydrocarbon (PAH).