Increased E-buses in Delhi Could Reduce Pollution-Related Mortality: Study

Changing the current fleet of Delhi buses to electric buses could reduce 74.67% of the total pollutant emissions.

Climate Change
7 min read
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  • A recent study finds that by transitioning the existing fleet of Delhi’s buses to electric buses, it could reduce 74.67% of the total pollutant emissions from the existing fleet.

  • The study noted that with e-buses, there could be a total reduction of 44 tonnes of Particulate Matter (PM) 2.5 per year and 1370 cases of avoided mortality and 2808 cases of avoided hospital admissions annually.

  • Loss of productive time on charging and deterioration of batteries over time continue to affect the potential benefits of electrification of public transport of the national capital, say experts.


Bright blue or green and white coloured buses, with “Zero Emissions” pasted on the sides, are regularly being seen on the roads of the national capital, Delhi.

These are Delhi’s electric buses – a fleet of 150 launched in May this year – which are in operation in addition to the existing fleet of buses that run on compressed natural gas (CNG), carrying thousands of commuters across the city every day.

CNG buses are known to release polluting gases such as carbon monoxide, carbon dioxide and nitrogen oxides besides Particulate Matter (PM) 2.5 and ultrafine particles.

Electric buses, on the other hand, have zero emissions when they are in operation as they run on batteries which are charged by electricity.

According to a recent study by researchers at the Kyushu University in Japan, the complete electrification of the public transport system in Delhi, with battery-operated electric buses, can have several “co-benefits” besides combating air pollution. This is due to its virtue of being a zero-emission transportation alternative.

The study, published on September 1 this year and titled Quantifying the multiple environmental, health and economic benefits from the electrification of Delhi public transport bus fleet estimating a district-wise near roadway avoided PM2.5 exposure, was published in the Journal of Environmental Management.

The study developed an integrated quantitative assessment framework to examine the benefits from the increased penetration of electrification of the public buses in Delhi.

The study estimated the benefits of e-buses in a scenario where all the existing public buses in Delhi are replaced by new electric buses. The study claimed that in such a scenario, 74.67% of the total pollutant emissions from the existing bus fleet in Delhi could be reduced.

It also pointed out that besides the reduction of emissions, the transition from CNG-based to electricity-based buses could have several other “co-benefits” such as increased energy efficiency, improved air quality and better public health.

Changing the current fleet of Delhi buses to electric buses could reduce 74.67% of the total pollutant emissions.

A busy traffic near Indraprastha DTC Bus Depot in New Delhi.

Photo: Manish Kumar/Mongabay.


According to the Delhi transport department, Delhi currently has a total of 7,310 public transport buses which include 7,060 CNG buses and a total of 250 e-buses.

The average mileage of CNG buses is 200 kilometres per day, according to the Delhi Statistical Handbook, 2020. These buses are run by the Delhi Transport Corporation and Delhi Integrated Multi-Modal Transit System (DMIT).

The Delhi government has announced 80% electrification of its buses in the next three years while it plans to have a total of 8000 e-buses by 2025. The numbers of e-buses are expected to increase by the end of this year itself.

According to sources in the department, 50 more e-buses are likely to come on to the road in the next few months while tenders for 4000 additional e-buses are also going to be floated soon.

Researchers of the Kyushu University study, Tavoos Hassan Bhat and Hooman Farzaneh, told Mongabay-India that this transition can help in significant reduction of Particulate Matter (PM) 2.5 emissions up to 44 tonnes per year which helps avoid about 1,370 deaths due to air pollution and a reduction in approximately 2,808 respiratory disease-related hospital admissions per year.

This, the researchers claimed, can help in saving about $383 million that is borne by the government and citizens because of expected reduced mortality and morbidity.

The study, with the help of a near roadmap PM2.5 dispersion model, developed by the researchers, analysed the present condition in the selected traffic zones in 11 districts of Delhi.

It used meteorological data, area specific data, traffic data to analyse the current situation and used parameters such as bus travel demand schedule, bus occupancy rate, technical specifications, battery capacity loss and emissions factors to understand a scenario of avoidable PM2.5 emissions in such areas.

With their health risk assessment model, they also tried to analyse the impact on health based on the anticipated avoidable PM2.5 exposure in case all the existing CNG buses are replaced by electric buses to come to a conclusion. Bhat said that currently in Delhi the annual emission of PM2.5 stands at 59.49 tonnes per year.

The study also highlighted that the number of passengers that travel a particular distance in an e-bus is lower than the number travelling the same distance in a CNG bus because e-buses need to be charged even during the productive time of the day as they cannot run all day even with a full charge.

In India, 17.8% of the deaths are due to air pollution which accounts for around 1.67 million annual deaths, according to a study by researchers from the Global Observatory on Pollution and Health at Boston College, the Indian Council of Medical Research (ICMR), and the Public Health Foundation of India (PHFI).

A 2021 study by Greenpeace on Southeast Asia found that the PM2.5 emissions in Delhi were responsible for 54,000 premature deaths in 2020.

Challenges in Delhi’s Fuel Transition

Bhat, one of the co-authors of the study, told Mongabay-India that the transition from CNG to electric has several benefits to health of the people and economy of the state but it has challenges too.

“Definitely there would be more investments if the government wants to replace all buses with e-buses in Delhi but it has many benefits as described in our study. Owing to the lower operational and maintenance costs compared to conventional vehicles the government is likely to recover the costs within six years.”
Tavoos Hassan Bhat, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Fukuoka

“The additional electricity demand for addition of extra electric buses for the transition is also not very high. We have estimated that this will demand 1.3% of the total electricity consumption in Delhi. And if the government works to use more renewable energy as sources to power the charging stations, these demands will also come down in the days to come,” Bhat told Mongabay-India.

He also added that for ensuring the same amount of passengers ferried over the distance covered by CNG buses now, the government would need 25% extra electric buses than the total number of existing CNG buses in operation now to compensate for the comparatively lower productivity of the e-buses that need charging during the productive period of the day.

To simplify, Bhat says if we want to replace 100 CNG buses, we will need 125 e-buses to ensure the same amount of services to passengers and performance of existing buses.

Changing the current fleet of Delhi buses to electric buses could reduce 74.67% of the total pollutant emissions.

An e-bus near Sarei Kale Khan in New Delhi.

Photo: Manish Kumar/Mongabay.


Currently though, note experts, there isn’t an ideal solution to avoid the challenge of time spent on charging.

“In India the government is also trying to boost the infrastructure of battery-swapping as an alternative to electric charging to reduce loss of timing spent in charging but in case of buses even the battery swapping is time consuming and complex and it would require multiple small power batteries to be replaced. It was also tried in some places and proved to be a futile experiment. Now the Union government is also planning to experiment with a dedicated electric corridor for e-buses where overhead electric wires could be tried to reduce dependency on batteries and charging,” said Sanyog Tiwari, founder of EV Urjaa, a battery swapping company.

He however claimed that e-buses would definitely bring down the operational and maintenance costs and prove economical for the states too. 

In Delhi, the buses are run under the Gross Cost Contract (GCC) Model where the Delhi government does not purchase the e-buses but pays the private service provider for hiring their services and the service providers take care of the maintenance, repair, charging the buses and the staff like driver, cleaner, conductors and others needed to handle the same.

Under this system, the government makes contracts with the private players for certain years and pays them on the basis of per kilometer for their services.

Convergence Energy Services Limited (CESL) is a unit of the Ministry of Power. Under the Convergence Energy Services Limited (CESL) Challenge tender, Delhi is set to get a total of 1500 e-buses for which orders have been placed by the government and the supply is slated to start from December this year onwards.

Incentives under the FAME-II scheme of the Union government and incentives from the Delhi government also aim to give support to the e-bus ecosystem.

Promit Mookherjee, a researcher at Observer Research Foundation (ORF) told Mongabay-India about the several challenges that are likely to come in the way of transition of public buses in Delhi from CNG to electric.

“We need dedicated manpower for the maintenance of e-buses to make it a successful model. We have seen cases of fires in e-bikes earlier. The same case with e-buses could be disastrous. So, there is a need to have dedicated manpower and agencies to ensure its maintenance and keep them ready for any emergency situation to deal with. Unlike other conventional buses, here the batteries of e-buses are produced by another company and buses by others, so its maintenance and repair remain a challenge,” he said

He also claimed that a large chunk of the buses in Delhi are owned by private bodies and thus special hand-holding support is needed by the government to help them.

“If the real intention is to reduce emissions and encourage the public to use buses instead of private vehicles, the government needs to also ensure the electrification of private buses too. Let’s do it on a pilot basis like helping in electrifying all the school buses to ensure the kids who use it daily are not exposed to harmful emissions from polluting vehicles.”
Promit Mookherjee, Researcher, Observer Research Foundation (ORF)

(This copy was originally published at Mongabay. It has been re-published here with permission.)

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