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The Supreme Court has brought ‘smog towers’ back in the news. What are they?

Air pollution in the national capital has been an issue of concern for quite some time as Delhi and its suburbs have ranked among the most polluted cities in the world frequently since 2014, when the WHO declared Delhi the most polluted city in the world.

Written by Shivam Patel , Edited by Explained Desk | New Delhi | Updated: July 31, 2020 6:42:40 pm
delhi pollution, delhi air pollution, delhi smog, delhi smog tower, delhi pollution tower, delhi smog supreme court, delhi smog tower iit, indian express Delhi and its suburbs have ranked among the most polluted cities in the world frequently since 2014. (Express photo by Prem Nath Pandey/File)

Last November, a Supreme Court Bench of Justices Arun Mishra and Deepak Gupta had sharp words for authorities in Haryana, Punjab and Uttar Pradesh for failing to control the practice of stubble-burning on farms, which contributes to air pollution in Delhi at the beginning of every winter.

“This has been going on since long. Is this not worse than internal war? Why are people in this gas chamber? It’s better to finish them with explosives in one go instead of suffering for long…,” Justice Mishra had remarked as the Bench directed authorities to take measures, including asking the Delhi government and the Central Pollution Control Board (CPCB) to submit a comprehensive plan on setting up “smog towers” in the capital.

A proposal on the towers was then submitted by the Indian Institute of Technology, Bombay (IIT-B) to the Central Pollution Control Board (CPCB). In January, the Supreme Court directed that two towers should be installed in the capital by April on a pilot project basis — one at East Delhi’s Anand Vihar, and another at Central Delhi’s Connaught Place.

This timeline was never met, however. This infuriated the apex court, and on July 29, The Indian Express reported that IIT Bombay has backed out from the project. Later that day, Solicitor General Tushar Mehta told the Supreme Court that IIT Bombay had indeed withdrawn from the project.

This upset the Bench greatly. “How can they back out from a government project? We will draw contempt against them. What is this nonsense?” the Bench of Justices Mishra, Vineet Saran, and M R Shah said. The next day, the Central government informed the court that IIT-B was back on board, and would be signing a Memorandum of Understanding for the project worth over Rs 36 crore.

What is a ‘smog tower’?

A smog tower is a structure designed to work as a large-scale air purifier, fitted with multiple layers of filters which trap fine dust particles suspended in the air as it passes through them.

Air is drawn through fans installed at the top of the tower, passed through filters, and then released near the ground, experts involved in the project had earlier told The Indian Express.

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The large-scale filters expected to be installed in the towers in Delhi would use carbon nanofibres as a major component, and would be fitted along the peripheries of the towers, project experts had said, adding that the height of the towers would be 20 metres.

Has anyone else experimented with a smog tower?

Yes, smog towers have been experimented with in recent years in cities in the Netherlands, China, South Korea and Poland. The first such tower was erected in 2015, in Rotterdam, Netherlands, created by Dutch artist Daan Roosegaarde.

This 7 metre-high ‘smog free tower’ can filter 30,000 cubic metres of air per hour around it, as per details on the Studio Roosegaarde website. More such towers were unveiled by Roosegaarde in subsequent tours of Poland, South Korea and China.

The towers to be installed in Delhi were to be the result of a collaboration between the IITs at Mumbai and Delhi, and the University of Minnesota. The university has helped design a 100-metre high permanent smog tower in the Chinese city of Xian. This tower was completed in 2017, and is supposed to be the world’s biggest air purifier.

How bad is air pollution in Delhi?

Air pollution in the national capital has been an issue of concern for quite some time as Delhi and its suburbs have ranked among the most polluted cities in the world frequently since 2014, when the World Health Organisation (WHO) declared Delhi the most polluted city in the world.

Pollution levels in Delhi increase dramatically during winter — on some days to nearly 10 times above the limits prescribed by WHO, posing a serious risk to vulnerable and also healthy populations.

This is largely because sources of emissions — construction work, industrial and vehicular pollution — in and around the city remain more or less consistent, but the situation is aggravated at the start of winter by smoke from stubble-burning in northwestern states, coupled with unfavourable meteorological conditions, such as calm winds, low temperatures, and fewer sunny days.

A number of measures have been taken over the years to control pollution levels. This includes persuading farmers in Punjab and Haryana to use mechanical alternatives to stubble-burning, closure of thermal power stations in Delhi, making industries use piped natural gas, in addition to control measures taken under the Graded Response Action Plan (GRAP) when pollution levels spike.

An assessment by the CPCB shows that Delhi’s air quality has been improving every year since 2016, even as it remains above acceptable limits, as a result of the pollution control measures being taken.

And how effective are smog towers?

Experts involved in setting up the smog towers in Delhi have said that the towers would create “clean air zones” in the city. An estimate made of their impact on air quality shows a tower would reduce 50% of the particulate matter load — fine dust particles suspended in the air — in an area of 1 kilometre in the direction of the wind, as well as 200 metres each along the sides of the tower and against the direction of the wind.

An affidavit submitted by the Delhi environment department to the Supreme Court in December had stated, “The (Delhi government) committee is of the view these smog towers may not be useful for the whole city, but they can be useful in creating ‘clean air area’ zones in different parts of the city.”

Another expert panel set up by the Centre’s Department of Science and Technology had estimated in December that 213 smog towers may be required across Delhi — which it said was premature at this stage, and had recommended a pilot project first.

An assessment of Roosegaarde’s smog tower in Beijing by the Eindhoven University of Technology found that in an open field in calm weather, it can reduce particulate matter of 10 micrometres (PM10) up to 45%, and PM2.5 levels up to 25% in an area of 20 metres around the tower, as per details on the ENS Clean Air website, a Dutch business that collaborated with Roosegaarde for the project.

As for the tower in Xian, researchers told the ‘South China Morning Post’ in 2018 that on severely polluted days, the tower was able to reduce smog close to moderate levels and improvements in the air quality had been observed over an area of 10 sq km in the city. Delhi government officials had, however, said that since full data were not available, the technology of the Chinese tower should be considered unproven still.

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