Recently, a Supreme Court bench 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.
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.
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.
- 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 and the height of the towers would be 20 metres.
- 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.
- 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.
Are they effective?
- 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 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.