Thursday, February 25, 2021

Fighting air pollution the green way

D.V. Subramanian

The World Health Organisation recently released a list of the 20 most polluted cities, 14 of them Indian cities. Kanpur, Delhi, Varanasi, Patna, Patiala, Faridabad figure here. Delhi has been in the news for more than a decade, grappling with suspended particulate matter in its air, the levels of which are so high that seasonal health warnings have had to be issued. But it’s not just Delhi, pollution is now a problem in all big Indian cities. The cost in terms of the health of citizens will be huge.
Vehicular emissions, particulate dust from the burning of crop residue, and dust from construction sites contribute to air pollution levels and smog. Use of diesel for vehicles is more polluting than of petrol and CNG. Two and three-wheel vehicles are more polluting than cars. Some seasonal measures have been introduced to tackle pollution, most of them flowing from court rulings. Different lobbies ensure that they are ineffective. Meanwhile, the number of vehicles keeps increasing.
The only option now is to seek the assistance of nature. Greening the environment by planting appropriate trees along roads and separators along highways is a possible solution as trees absorb carbon dioxide, and store the carbon while releasing oxygen. An acre of mature trees absorb in one year the same amount of carbon dioxide produced as a medium-sized car running 40,000 km. Trees clean the air by absorbing odours and pollutant gases — oxides of nitrogen, carbon monoxide and sulphur dioxide. Trees provide oxygen. In a year, an acre of trees such as peepal can give enough oxygen for 18 persons.
Trees to cool
Decrease of tree cover and an increase of heat-absorbing roads and buildings raise average temperatures in cities. Trees cool them, muffle noise pollution and create a soothing canopy of green.
But this is a slow solution. Trees need years to attain sufficient spatial density and canopy. It’s unfortunate that mature trees, older than 50 years, have been sacrificed for widening inner city and highway roads for ‘growth’.
There are, however, ways to compensate for the absence of mature trees. A a Central American city affected by air pollution as many Indian cities, has deployed one method successfully.
During the last two decades, Mexico City was badly affected by air pollution. But with public determination and commitment, it found a beautiful way to clean its polluted air with a project called Via Verde, or ‘green way’.
In a widely circulated video, Ferdinando Ortiz Monesterio, founder-director of Via Verde, says the project has transformed more than 1,000 concrete pillars of the elevated high ways of Mexico City into vertical gardens to improve air quality and aesthetics in the city. The total area of the pillars used is more than 600,000 sq ft. The vertical gardens use soilless technology to grow plants in a special kind of medium made out of recycled plastic bottles and other stuff to have properties and density similar to the soil.
Rainwater use
These gardens use rainwater captured on the elevated highway and at ground level, to keep the 500,000 plants of the vertical garden, green. They suck more than 27,000 tons of polluting gases annually from the environment. They produce annually enough oxygen for 25,000 persons. And, they capture more than 11,000 tons of dust. The greenery has also taken stress off commuters.
This innovative technique of growing vertical gardens for fighting air pollution is now in vogue in China, Germany, Japan, the U.S. and France. In China’s Jiangsu province, a “vertical forest” is coming up in Nanjing, with the capacity to produce about 60 kg of oxygen every day and absorb 25 tons of carbon dioxide. People will be able to breathe oxygen 3,000 times purer than the average level in China.
Designed by Stefano Boeri, an architect, the “forest” will be a pair of towers. The twin towers will have 1,100 large and medium-sized trees on their facade, along with 2,500 other plants and shrubs. One of the towers will be 200 m high, with 35 floors. It will house a museum, a rooftop private club, and a school of architecture specialising in green buildings. The smaller tower will be just over 100 m tall. But this is an expensive project.
How can Delhi, or for that matter other Indian cities affected by pollution, adapt vertical gardens or forests to suit their budgets? The Mexican Via Verde model is not high-cost as it does not involve building anything. Small plants and climbers can be grown on the supporting pillars of the elevated highway; for aesthetics, one can grow even climbers with flowers. Such plants can be grown with suitable support even on normal road flyovers whose side-walls have a large surface area.
Such projects can also become job-creators as planting and taking care of the gardens will require hands familiar with gardens. This should be the future for the concrete jungles of India.
(Courtesy: The Hindu)