New Delhi’s decades-old regime to control vehicular pollution, including a heavy reliance by commercial vehicles on compressed natural gas (CNG) fuel, has been challenged by a new study by the International Council on Clean Transportation (ICCT). 

The report upends the narrative the that CNG is a ‘clean’ fuel, pointing to its high level of health-damaging emissions of nitrogen oxide (NOx), which can damage children’s lung development and contribute to a range of chronic lung diseases.

The report is based on innovative remote sensing technology that monitored actual traffic flows. Its results challenge two critical policy interventions: the mandate for buses and taxis to use CNG, as well as a Pollution Under Control Certificate (PUCC) surveillance system.

The PUCC requires every fossil-fuel powered vehicle to undergo regular emissions checks, with car owners facing fine if they do not have an up-to-date certificate. 

However, the ICCT report highlights how the PUCC inspections fail to capture emissions of the two biggest polluters – NOx and Particulate (PM2.5) – as well as failing to reflect the level of real-time emissions on city roads.

Its authors point out that both automobile tech and air pollution monitoring have become a lot more sophisticated and the PUCC tech has not kept up. 

Vehicle emissions, according to some estimates, contribute as much as 38% to Delhi’s pollution. 

Famous for exposing ‘dieselgate’

The ICCT is famous for exposing Volkswagen for falsifying real-time data on NOx vehicle diesel emissions in its reporting  to the US Environmental Protection Agency in 2015. The scandal, widely known as ‘Dieselgate’, led to a global reconsideration of diesel engines and their health impacts, in terms of excessive particulate emissions as well as NOx.

It conducted this India study on CNG vehicles with the support of the local transport and police departments in Delhi and Gurugram, on its southern border. The two cities are among the 20 most polluted globally. 

“For the first time in India, we have collected significant emissions data from motor vehicles on the road and it is crucial to remember that what impacts our air quality is not the laboratory emissions but the pollutants released by these vehicles when they are in operation. Therefore, it’s time to reimagine our emissions testing regime and aggressively push for the adoption of zero-emission vehicles,” said Amit Bhatt, India managing director of ICCT.

CNG is not a ‘clean’ fuel

According to the study, CNG vehicles emitted very high levels of nitrogen dioxide and other oxide of nitrogen  (NOx) emissions, challenging the narrative that CNG is a ‘clean’ alternative fuel.

NOx causes shortness of breath, irritation in the eyes, nose and throat in acute exposures. But there’s also substantial evidence of excess rates of asthma and impeded lung development amongst children growing up along busy highways where NOx emissions are high. Chronic NOx exposure can lead to the development of a range of lung diseases in the long term. For example, some light goods vehicles, commonly seen ferrying vegetables and other supplies in the city, emit up to 14.2 times their lab limits, and taxis are four times. 

“This shows that while the CNG transition has helped cut toxic particulate emissions from diesel vehicles during the early years, NOx emissions from on-road CNG vehicles without adequate controls can be high. This builds a case for the next big transition to electrification to make tailpipe emissions not cleaner but zero,” said Anumita Roychowdhury, executive director of the Centre for Science and Environment, one of India’s foremost air pollution experts.

The report found that tougher engine standards have helped reduce NOx emissions. The latest Indian standard, Bharat Stage 6 (BS6), which is comparable to a Euro 6 engine, shows a reduction in real-world NOx emissions from private cars of 81% and buses by nearly 95% as compared to Bharat Stage 4 (comparable to a Euro 4). Of the over 110,000 vehicles sampled by the ICCT study, 55.5% are BS 4, and 33.5% are of BS 6. (See figure below.)

Commercial vehicles pollute more than private cars

One clear trend the study identifies  is that commercial vehicle emissions are higher than private vehicles. 

In the BS6 four-wheeler category, light goods vehicles (LGV) had five times higher NOx emissions, seven times higher carbon monoxide emissions, and five times higher hydrocarbon emissions than private cars.

Meanwhile, in comparison to taxis, light goods vehicles had double the NOx emissions, six times higher carbon monoxide emissions, and four times higher hydrocarbon emissions.

However, commercial taxis were consistently far more polluting than private cars within the passenger car segment, indicating poor maintenance. There were also multiple instances where three-wheelers, mostly running on CNG, had higher emissions than passenger cars.

Innovative remote sensing technology 

ICCT used a remote sensing technology to measure the emissions of vehicles on roads as they drove past the sensors. At each of the 20-odd sites, machines about the size of large microwave ovens were placed on either side of a road lane. It took a split second to capture the emissions data. Simultaneously, a camera snapped a picture of the vehicle and licence plate. The emission data was matched with the registered vehicles database. Over 110,000 vehicles were monitored across four months in early 2023.

Now, the ICCT is calling for the remote sensing system to be implemented as a regular monitoring system. It points out how air pollution has shut down schools in Delhi and Gurugram and how harmful it is to human health and the local economy.

🚨 New TRUE vehicle emissions testing in India shows:
📊 Standards changes show major improvement, but still emitting over set limits
🌬️ Compressed natural gas vehicles produce up to 14x NOx limit
🚛 Commercial vehicles are particularly high emittershttps://t.co/1nfOUMliID pic.twitter.com/sLfvmUmSf8

— TRUE Emissions (@TRUE_Emissions) August 23, 2024

Current vehicle pollution-check system unreliable 

While the ICCT says the system can complement the over two-decade-old PUCC system, it could render the PUCC obsolete. The latter does not measure on-road emissions; it only measures when the vehicle is parked. 

The PUCC monitors CO and HC but not particulate matter or NOx, which are major contributors to pollution in this region. 

There also are concerns that the PUCC data can be manipulated, especially in states where it’s recorded manually. The low failure rates, the report says, suggest a need to reconsider the reliability and authenticity of the tests. All of this suggests a broken system.

Swagata Dey, an air quality policy specialist at the Centre for the Study of Science, Technology and Policy (CSTEP), has spent years studying the PUCC system.

She says this is “not effective in controlling real-world emissions. So, in this case, the remote sensing technique is welcome, but we also have to find a way to scale up the process… Further, we have to ensure that results from such methods are acceptable in the court of law.  Without this [legal recognition of the remote sensing technology], vehicles cannot be asked to comply with this test for obtaining PUCC certification.”

The policy stage, however, has been long set for the wider adoption of a more accurate pollution monitoring regime. India’s Supreme Court, the National Green Tribunal, India’s top dedicated environment court and federal pollution control agency, have all called for implementation of more accurate vehicle surveillance for some years. 

Kolkata authorities have been using remote sensing since 2009, the study’s authors point out, even initiating action against vehicle owners based on readings. 

Globally, the system has been used extensively in places like London, Paris, and Hong Kong. 

What the ICCT report offers is new scientific evidence to overhaul or even replace the PUCC regime. It also challenges the notion that CNG can serve as an alternative, clean fuel to diesel and petrol.

For about two decades both concepts have been the bedrock of policy action to reduce vehicular pollution, a significant contributor to India’s air pollution crisis.  Debunking these misconceptions, can jump-start the dialogue about truly sustainable solutions. 

Image Credits: ICCT, Chetan Bhattacharji/HPW.