Cng Delhi Case Study

Nearly 18 years after Delhi took its first steps towards getting its public transport vehicles to switch from diesel and petrol to the cleaner Compressed Natural Gas, the national capital is the most polluted city in the world. The initial gains of the mass switchover to CNG were negated by a rise in the number of vehicles, especially diesel vehicles.

Today, Delhi is set to fall back on CNG again to pull it out of a difficult situation. On Saturday, the Supreme Court ruled that all diesel taxis must convert to CNG immediately in order to ply in the national capital. The order came on the last day of the second phase of the odd-even scheme – which allowed car owners to drive only every other day – but doesn’t seem to have caused any significant drop in the pollution levels. In fact, some reports suggest that pollution actually increased during odd-even dobara, sending the government back to the drawing board.

The SC order will impact at least 35,000 diesel taxis in Delhi, most of which run on cab aggregation platforms like Uber and Ola. These companies asked the court to be lenient, claiming that their drivers cannot afford the cost of conversion, but the SC was unmoved. It cited its 1998 ruling in which it had said that all commercial passenger vehicles must run on CNG. “Why did you buy diesel cars? We can’t keep extending deadlines,” the court said.

The SC’s 1998 ruling was a landmark one that it led to the conversion of Delhi’s public transportation system to the cleaner CNG fuel. Its latest ruling means a few thousand vehicles will be taken off the roads unless they convert to CNG. But will this have any impact on the capital’s ever-rising pollution levels? Past experience suggests that it just might.

Going green

In the late 1990s, Delhi’s first big bang CNG programme was kickstarted when activists filed Public Interest Litigations in the Supreme Court to control the city’s rising air pollution. The SC set up the Environment Pollution (Prevention and Control) Authority in 1998 to advise it on controlling pollution and to monitor the implementation of its directives.

Following the Delhi government’s recommendations to launch a broad CNG programme – made in consultation with the new authority – the SC then issued several directives to ensure implementation. These included strict deadlines to convert the city’s entire bus fleet to CNG; state-owned GAIL was asked to increase the number of CNG stations in the city from 9 to 80 by the year 2000, and all pre-1990 autos and taxis were ordered to convert to clean fuels by a 2000 deadline too.

In 2003, when the Central Pollution Control Board released its study of 22 polluted cities, Delhi appeared to be breathing easier. The SC noted the data and observed that air quality had “improved considerably” since 1996 even as particulate pollution in other cities was getting worse.

Soon enough, more vehicles converted to CNG than the government had anticipated. This caused some trouble as the limited number of gas stations meant that users sometimes spent more than 10 hours in queues to fill gas.

In 2002, the SC rapped the Delhi government for its failure to replace diesel buses with CNG-run ones by the March 2001 deadline. It fined the government Rs 1,000 per day per diesel bus that was still on the streets. By December that year, the last diesel bus was taken off the roads, and the national capital ended up with the cleanest public transportation system in the world.

The switch to CNG showed significant results, at least initially. A study by the Washington DC-based Resources For the Future, which studied air pollution in the capital for 15 years (1990-2005), said the CNG conversion of public transport had made the “most significant” impact on air quality. A 2004 World Bank study of several Indian cities where CNG programmes were launched also concluded that the switch to CNG had prevented premature deaths. The study said: “One of the largest CNG programmes have helped to reduce the number of premature deaths annually – at least 3,629 in Delhi and at least 5,308 in Mumbai.”

Bumpy road

However, it wasn’t all smooth running for the switchover by buses, which saw technological problems and cost overruns. Also, according to a paper authored by the Centre of Science and Environment, no study has specifically looked at the impact of CNG buses on Delhi’s pollution even though overall numbers suggest it helped it reduce substantially.

This is perhaps why the court has once again turned to CNG to help combat Delhi’s pollution. But besides the fact that converting cabs to CNG is likely to put a financial strain on drivers who may not be able to afford it, the bigger question of pollution also remains unanswered. For instance, the CSE paper on CNG claims that retrofitted vehicles aren’t as successful in combating pollution as pre-fitted new vehicles.

The paper said: “Global experiences have shown that poor quality conversion and diesel to CNG conversion can be particularly problematic and if not done well, gaseous emissions can escalate.”

It adds: “Evaluation show that the retrofitters [businesses which convert diesel engines to CNG] had claimed to provide one year warranty on components, original conversion kits, and customer support but studies found frequent breakdowns and poor workmanship, and lack of customer support.”

This, along with the fact that though the switch to CNG made a significant impact on Delhi’s air, the gains were negated by the sheer increase in the number of vehicles, especially diesel vehicles, perhaps means that for pollution levels to really go down significantly, more than just CNG vehicles, Delhi needs fewer vehicles on its streets. But that won’t happen till the national capital ramps up its public transport system, especially last-mile connectivity.

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Not very long ago in 1993, during the English cricket tour of India, when the visitors lost a match, they attributed part of their loss to the air pollution in Delhi – the capital city of India [8]. Perhaps they were bad losers, but we must admit that the pollution levels were dangerously high enough for it to be listed amongst the world’s most polluted cities. Vehicular emissions, which accounted for 70% of the air pollution, would morph into deadly smog during the foggy winters resulting in an increase in respiratory illnesses, with children and senior citizens being the worst affected. With the economy shifting gears around the same time amidst increasing middle class aspirations, with about 500 new vehicles being added every day, a turnaround seemed highly improbable.

Ever since then, Delhi has won the US Department of Energy’s first ‘Clean Cities International Partner of the Year’ award in 2003 for ‘‘bold efforts to curb air pollution and support alternative fuel initiatives’’ [7]. In a unique display of judicial activism, the Supreme Court of India ordered the responsible government to switch its public-transit system to a cleaner-burning fuel in response to citizens concerns about air pollution. Buoyed by the public pressure, the government of New Delhi reluctantly as is typical of a developing nation, complied and enforced regulations to convert its entire fleet of diesel and gasoline dependent public transport system to Compressed Natural Gas (CNG) by 2002. It’s funny to note that the court actually slapped a fine of about $450 on the Union government, for repeatedly seeking a modification in the order [4]. To its credit, once the government set about preparing a comprehensive action plan by passing the desired legislation and setting up the infrastructure necessary for such a transition, it earned the recognition of drafting one amongst the top 12 best policies in the world, as per a study conducted by the World Wide Fund for Nature (WWF) and E3G [1].

Between 2000 and 2008, the Carbon emissions plummeted by 72%, while the SO2 emissions decreased by 57% on account of 3500 CNG buses, 12000 taxis, 65000 auto rickshaws (tuk-tuks) and 5000 mini buses plying on CNG [1]. CNG is mainly comprised of methane, which upon combustion mainly emits CO2 and H2O and being lighter disperses very quickly, whereas gasoline and diesel being more complex, emit more harmful emissions such as NOX and SOX.  Owing to the recent volatility in the oil prices and continued patronage of CNG by the government by way of subsidies, the general public has begun to increasingly incorporate CNG kits in their private vehicles, which facilitates them to run on dual fuel mode.  Encouraged by the public response, the Ministry of Petroleum and Natural Gas has set about an ambition plan of bringing 200 cities under the supply network of CNG and Piped Natural Gas (PNG) by 2015 [5]. For a country which depends on 70% of oil imports, the recent indigenous gas discoveries in the K.G Basin and elsewhere have only brightened our outlook for lesser dependence on foreign oil, enabling us to save valuable foreign exchange. In view of growing awareness for cleaner air and climate change, there’s many a lesson to be learnt from Delhi’s resurgence.


  1. Hohne, N., Burck, J., Eisbrenner, K., Vieweg, M. and Grieβhaber, L., “Scorecards on best and worst policies for green new deal”, WWF and E3G, Nov 2009.
  2. Jalihal, S. A and Reddy, T. S., “CNG- An alternative fuel for public transport”, Journal of Scientific and Industrial Research, May 2006.
  3. Narain, U. and Krupnick, A., “The impact of Delhi’s CNG program on air quality”, Resources for the Future, February 2007.
  4. Singhal, B., “Presentation on the introduction of CNG in Delhi”, Delhi Integrated Multi-modal Transit System Ltd.
  5. Joshi, S., “200 cities to get CNG, PNG by 2015”, The Hindu.
  6. Choubey, U. D., “Need for partnership based model”, Financial Express, July 2008.
  7. Jain, S., “Smog city to Clean Capital – How Delhi did it”, Mumbai Newsline, May 2004.
  8. “England in India and Sri Lanka, 1992-93”, ESPN Cricinfo.

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