New Delhi: The Centre for Science and Environment’s (CSE) latest assertion that newer cars emit more carbon dioxide than older ones could well be part truth and rest hot air.
That’s because the activist group, which concluded that new cars emit more carbon dioxide, may have drawn these conclusions by comparing the performance of vehicles which are in the same category without being similar. The data used by CSE was obtained from the Automotive Research Association of India, or Arai, a certifying body, and it compares vehicles of different engine sizes and weights, even though they belong broadly in the same class.
So, while CSE says small cars available in 2005 were more polluting than those in 2000, the vehicles used as a basis for this surmise, while broadly classified as small, are actually vastly different in size and performance.
Smoky affair:The data used in the analysis show that Arai compared vehicles of different sizes. (Photo: Sanjeev Verma/MINT)
CSE claims emission factors are representative of a class of vehicles, such as small and mid-sized, and that therefore, its analysis shows that newer cars emit more carbon dioxide than old cars. Carbon dioxide is a greenhouse gas and contributes to global warming.
The “factors are supposed to represent a technology vintage,” said Anumita Roychoudhury, associate director of research and advocacy at CSE. “That’s all the data we have and we are asking if car companies are increasing the weight of vehicle?”
A closer look at the data given in the Arai study titled “Air Quality Monitoring Project-Indian Clean Air Programme (ICAP)”, which formed the basis for CSE’s ananlysis, shows that the certifying body compared vehicles of different sizes.
For instance, in the category of passenger cars below 1,000cc, it has taken the Maruti 800 as being representative of such cars between the years 1991 and 1996, and a Maruti Zen, which is heavier and more powerful, as being representative of small cars after the year 2000. Emissions for heavier and more powerful cars, especially with larger engines, are more than those of lighter and smaller ones.
In the case of diesel cars, Indica has been taken as being representative of cars available in 2000 and Indigo, in 2005. While both cars are made by Tata Motors Ltd, the Indigo weights upto 105kg more than the Indica.
CSE says it ignored the differences in specifications when making the comparisons because it was going by a wide category and didn’t differentiate between an 800cc car and a 1,300cc car because both belong to the class of small cars.
“Larger cars would produce more carbon dioxide,” says Shashikanth Suryanarayanan, assistant professor of mechanical engineering, Indian Institute of Technology, Mumbai. “The amount of carbon dioxide produced is linked to the size of the engine and load. Things like hydraulic power steering will add to more load. The amount of fuel consumed depends on the load and more fuel consumption means more emission of carbon dioxide.” It is likely that newer vehicles in categories such as small cars have hydraulic power steering, which means a higher load, and, as he explained, more emissions, but it is also likely these cars come with lighter and more efficient engines.
However, only a like-for-like comparison across categories can establish whether new cars actually emit more carbon dioxide. Even Arai admits as much, and says “the sample size is limited and the technical committee has also felt the need to test more number of vehicles as the automotive industry in India is expanding at a very rapid rate.”
Mint could not ascertain whether newer vehicles with the same engine sizes and other features as older ones produce more carbon dioxide.
An Arai official involved in the research and who does not wish to be identified said the study was not about “carbon dioxide emissions.” He said the agency was merely trying to “capture the real situation (on the roads)..” through the study.
Carbon dioxide and fuel efficiency standards are typically defined on basis of the mass of the vehicle or its size. Among the at least 20 countries that are targeting carbon dioxide emission reductions by the end of this decade, only two, South Korea and Taiwan, define it on the basis of engine displacement measured by cubic capacity of the vehicle.
“As automakers, we would prefer to go with kerb weight (mass of the vehicle),” for defining emission standards, says Arun Jaura, chief technology officer, Mahindra and Mahindra Ltd, the country’s largest utility vehicle maker.