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Explained | Hiding behind a smog tower

Like all end-of-pipe solutions, whether for effluents or for emissions, investments such as smog towers or effluent treatment plants have been established to be futile and economically unfeasible in the long run

August 24, 2021 / 12:05 PM IST
A 25-metre (82 foot) high smog tower near Connaught Place in New Delhi inaugurated by Delhi CM Arvind Kejriwal on August 23. (Source: ShutterStock)

A 25-metre (82 foot) high smog tower near Connaught Place in New Delhi inaugurated by Delhi CM Arvind Kejriwal on August 23. (Source: ShutterStock)

On August 23, Delhi Chief Minister Arvind Kejriwal inaugurated India’s first smog tower at Connaught Place. Air pollution is a major concern, especially during the winters when air quality remains at hazardous levels for weeks together.

Given this, it will be interesting to dive deeper and clear the air about smog towers.

What is Smog?

Smog is the dirty brown haze that hangs over the skylines of major cities. The term ‘smog’ was first used in the early 1900s to describe a mix of fog and smoke from burning coal. Today, most of the smog we see is photochemical smog.

Photochemical smog is produced when sunlight reacts with nitrogen oxides and at least one volatile organic compound (VOC) in the atmosphere. Nitrogen oxides come from car exhaust, coal power plants, and factory emissions. The VOCs are released from gasoline, paints, and many cleaning solvents. When sunlight hits these chemicals, they form airborne particles and ground-level ozone — or smog.

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Why is it harmful?

Smog causes multiple health problems, such as difficulty in breathing, eye irritation, asthma, reduced immunity to lung infections, and colds that can be fatal in children. The ozone in the smog also inhibits plants growth. It can cause widespread damage to crops and forests, and the haze reduces visibility. When inhaled, smog irritates our airways, increasing our risk of serious heart and lung diseases. These health risks are why many cities monitor smog levels.

What is a Smog Tower?

Smog towers are structures designed as large-scale air purifiers to reduce air pollution.

Smog towers work on the principle of HEPA filtration or air ionisation technology to remove PM2.5 particles. That is, air flowing through a smog tower passes through a filter to provide clean air coming out of it. These methods of cleaning air are scientifically well established and used widely for cleaning indoor air where the air exchange with the outdoors is minimal. The first prototype of a smog tower was built in 2017 by Dutch artist Daan Roosegaarde in Beijing as a demonstration and art project that converts the carbon in filtered particles into diamonds.

Does it work?

The only operational smog tower in the world is a 60-metre high tower in Xian, the capital of northwest China’s Shaanxi province. The tower has been slammed by experts and national media as an ‘eyewash’ and ‘ineffective’. It has been undergoing testing by researchers at the Institute of Earth Environment at the Chinese Academy of Sciences, who claim that so far, the average reduction in PM2.5 — the fine particles in smog deemed most harmful to health — fell 15 percent during heavy pollution. That’s a spoonful from a periphery of not more than 100 metres.

Maybe our tower will be better?

According to Vikram Singh, Department of Chemical Engineering, Indian Institute of Technology Delhi, “Cleaning of ambient air is impossible at the scale of a city or any open-air community due to the air pollution being very dilute with continuous replenishment of polluted air from the boundary layer and neighbouring regions, that is, from both vertical and lateral directions.”

According to the engineers, the smog tower in Delhi, built at the cost of Rs 20 crore will have 40 giant fans on a 25-metre (82-foot) tower that will pump 1,000 cubic metres of air per second through filters that halve the number of harmful particulates in a radius of one square kilometre only.

So why is Delhi installing it?

The government is desperate to find a solution, any solution, even untested. According to the World Health Organization (WHO), India has six of the top 10 most polluted cities in the world, with Delhi on the top of the list. A 2020 study in The Lancet found there were 1.67 million deaths in India attributable to air pollution in 2019, including almost 17,500 in Delhi. The Supreme Court in January 2020 directed the central government to construct a smog tower to reduce pollution at Anand Vihar and the Delhi government to install another such structure at Connaught Place in three months.

So what is the solution?

Like all end-of-pipe solutions, whether for effluents or for emissions, investments such as smog towers or effluent treatment plants have been established to be futile and economically unfeasible in the long run. The only solution is to reduce harmful emissions.

Some of the immediate measures that can be taken include stopping usage of all diesel generators (a law exists but it is not being implemented), massive adoption of electric vehicles, strict policies to curb construction dust, shutting down coal plants and forcing industries to adopt methods of reducing emissions.
Shailendra Yashwant is a senior advisor to Climate Action Network South Asia (CANSA). Twitter: @shaibaba. Views are personal.
first published: Aug 24, 2021 12:05 pm

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