Centre for Science and Environment (CSE) condemned the new study on compressed natural gas (CNG) that has been jointly carried out by the CSIR, IIP-Dehradun and University of Alberta.According to CSE, the statements from CSIR have claimed, without presenting the full study and the facts in the public domain, that CNG buses emit more ultrafine particles than diesel buses and are a health hazard.

As per CSE, finding from CSIR was striking as it has shown that the conventional CNG buses in India have already achieved emissions levels for all pollutants including ultrafine particle number very close or better than Euro VI emission standards that are yet to be implemented.

"Diesel buses are far behind. The ultrafine emissions from Indian CNG buses are higher only from the Canadian diesel bus with advanced particulate traps meeting one of the global best standards," said the CSE study.

The study stated that this motivated campaign against CNG buses in India, and defiance of what science is saying, will harm not only the CNG bus programme that has given enormous public health benefits but will also jeopardize the policy decision to leapfrog emissions standards roadmap to Euro VI by 2020 to cut dangerous diesel emissions.

"The government of India is dragging its feet in the face of strong opposition from the diesel industry. Diesel technology and fuels need the most drastic transformation in Indian transport sector today to protect public health," said CSE member.

This study, done jointly by CSIRIIP-University of Alberta,has carried out real world emissions tests on two Indian CNG buses and two diesel buses. The measurements were carried out while accelerating and cruising the vehicles. The study revealed that the ultrafine particle emissions from Indian diesel bus without particulate traps emit 600 to 2,000 times more than the Indian CNG bus. "CSIR should have put out a red flag immediately to highlight this concern and urged the government to leapfrog to Euro VI emission standards when much tighter particle mass standards and particle number standards become applicable," mentioned CSE in its study.

As per CSE, even more dramatic finding is that the conventional Indian CNG buses have ultrafine particulate number emissions close to the Euro VI standards for particulate number. "While the limit value for particle count under Euro VI emissions standards is 600 billion particles per kwhr, the actual observed level in one CNG bus is 278 billion particles per kwhr and in the second 950 billion per kwhr," said CSE.

The reportage on this study is silent on the performance of CNG bus on all other parameters including carbon monoxide (CO), non-methane hydrocarbon (NMHC) and nitrogen oxide (NOx) that have also been tested as part of this study.

Conventional Indian CNG buses have been compared with Canadian diesel bus with advanced particulate traps and NOx controls meeting one the best global standards. But there is no data on how CNG buses in Canada meeting the same tighter standards perform. Only when Indian conventional CNG bus was compared with the Canadian diesel bus with particulate traps and advanced NOx control meeting US Tier 2 standard, tighter than even the Euro VI standards, the study found levels of ultrafine to be 12 to 40 times higher. But it has not been mentioned what genre of Indian CNG bus has been compared.

But more important, the same study shows that the Indian diesel bus without particulate trap emits 28,000 times higher ultrafines compared to Canadian bus with particulate traps – much worse than Indian CNG bus. The study has only reconfirmed how CNG bus fleet is giving the overall environmental benefits compared to CNG buses even today.

"CSIR has omitted to mention the serious health risk associated with diesel emissions.It is now well known that the WHO has concluded that diesel exhaust is a human carcinogen and is in the same class as tobacco for its strong link with lung cancer.

CNG based public transport system has already given enormous opportunity to cities to have a winwin strategy of clean fuel based public transport.But there are many cities that do not have CNG and will continue to use diesel. "Moreover, all trucks and buses across the country will need clean diesel. It is therefore important that a quick transition is made to clean fuel and vehicle technology benchmarked to Euro VI standards," added the study.