Retaining improved air quality after Covid-19 lockdown

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Updated: Jun 11, 2020 9:14 AM

Three-tier mixed species forests along the Yamuna can scrub air columns of pollutants

CO2 emissions, air quality of cities, International Energy Agency, global energy, india emissions, co2 emissions, covisd 19 lockdown, delhi AQI, air pollutionThe International Energy Agency (IEA) has estimated that global energy-related CO2 emissions are set to fall by 8% this year. (Representational image: Reuters)

The fear that infection from the novel coronavirus can lethally impair lungs and breathing has forced people into prolonged inactivity and considerably improved the air quality of cities. The International Energy Agency (IEA) has estimated that global energy-related CO2 emissions are set to fall by 8% this year—the largest decrease in emissions ever recorded, and six times the previous record drop of 400 million tonnes in 2009, after the financial crisis.

The environmental website, Carbon Brief, says India’s emissions fell by 1.4% (30 million tonnes) in FY20 (Lockdown began on March 24). During that month, it says, CO2 emissions dropped by 15%, and likely fell by 30% in April, owing to the lockdown.

In Delhi, AQI was ‘satisfactory’ for 18 days in April and May compared to just one day during the same period last year. ‘Satisfactory’, is one step lower than ‘good’ in the six rung AQI. One step lower than ‘satisfactory’ is ‘moderate’, and there were 41 such days compared to 26 in the year-ago period. Thirty-four days were ‘poor’ or ‘very poor’ during April-May 2019 against two ‘poor’ days during the same period this year when people were likely to feel discomfort in breathing or were at risk of developing respiratory illnesses.

So, how do we retain the gains post-lockdown? N Bharathi suggests plantations of bamboo along the banks of the Yamuna on raised bunds. Bamboo is a fast-growing species and has economic value. Bharathi is a bit of a bamboo fanatic. An agricultural scientist from Tamil Nadu Agricultural University (TNAU), he has a company called Growmore Bio-tech in Hosur on the Tamil Nadu-Karnataka border. It specialises in making bamboo clones for state bamboo missions, and the plantations that feed power plant boilers and alcohol fermentation vats. Each bamboo culm or pole absorbs 450 kg of CO2 a year, he says. Indians, on average, emitted 1.7 tonnes of CO2 in 2014, according to the World Bank. It would take four bamboos per person to neutralise annual emissions. Since rural folk pollute less, city dwellers will need to plant more.

Bharathi recommends Bambusa balcooa, a species that grows extensively in the north-east. It is naturally sterile, unlike other bamboo species, which flower after a few decades, produce seeds and die. It does not have thorns, so is unattractive to snakes which use the spikes to shed slough. That makes it easy to harvest. The variety grows up to 55 feet when well-tended. Each pole weighs 25 kg as it is dense; the hole in the middle is about the width of a finger. With close planting, irrigation (20 litres per day), application of fertilisers and good agronomic practices about 40 tonnes per acre can be harvested annually, Bharathi says. At any time, Bharathi has about a million two-year-old, tissue-cultured plants produced at his laboratory, ready for planting.

Forty tonnes of cane can produce 10,000 litres of ethanol, according to Bharathi. The yield is better than cane. The cane juice, when converted entirely into ethanol, can yield 2,400 litres per acre, says Bakshi Ram, Director of the Sugarcane Breeding Institute in Coimbatore. This is from the blockbuster variety, Co-0238, he has developed. It has a high yield per acre (31.5 tonnes), and a high rate of sugar recovery (a little over 11 tonnes for every tonne of cane crushed). If the cane juice is used to make sugar, the ethanol yield from molasses drops to a fifth.

Ethanol is also produced from maize. In the US, an acre of maize yields on average 1,775 litres of ethanol, as per the University of Nebraska-Lincoln. Average US maize yield is much higher than that of India.

U Sivakumar, professor of Microbiology, TNAU, says the advantage of bamboo as a raw material for ethanol production is that it does not compete with food material. It can also be grown on wasteland. KT Parthiban, professor and head of forestry at the Forest Research Institute, TNAU, says Bambusa balcooa is a densely populated plant with heavy foliage, which is good for trapping gaseous and particulate pollutants. He says it acts as a good sound barrier too. His experiments have shown that it responds well to irrigation and fertiliser. He thinks it is a good idea to plant it along the Yamuna.

Bambusa balcooa is the preferred input for a 60 million litre per year ethanol plant that Numaligarh Refineries (NRL) in Assam is setting up. While it is contributing half the investment, the rest is from Fortum, a Finnish energy company and Chempolis, the Finnish licensor of the technology. This is one of the 12 projects that the central government is supporting with Rs 150 cr each. The Indian refinery is the first to use the Finnish licensor’s technology.

The capital cost of ethanol produced from cellulose is usually high, making it unprofitable. SK Barua, managing director, NRL, says the Finnish technology is efficient. The other chemicals—furfural and acetic acid—will enable the plant to recover the cost of production. Barua says, the bamboo species have been tested for alcohol production and found to be satisfactory. The project will commence production from the end of 2021. The recent slump in prices of petro-fuel (with which ethanol is blended) has not forced a rethink, Barua says.

Even if there is a demand for ethanol, are bamboo plantations advisable along the Yamuna? CR Babu says they can be planted on the slopes of the bunds and elevated flood plains of the Yamuna, not in ribbons, but with native broadleaf species and shade-loving shrubs. Babu is an ecologist and professor emeritus at Delhi University’s Centre for Environmental Management of Degraded Ecosystems (CEMDE). He is advising the Delhi Development Authority on bio-diversity parks, and the Delhi government on replacing Vilayati Kikar, an invasive Mexican shrub, with native species on the Ridge. Babu says a three-tier community of mixed species, comprising bamboo and broadleaf trees with shrubs in between can efficiently scrub the columns of air passing through them of CO2 and particulate matter like PM10 and PM2.5.

Any plantation along the Yamuna needs an ecosystem approach, says Faiyaz Khudsar, scientist in charge of CEMDE’s biodiversity parks programme. The community of trees and grasses must help maintain river flow and biodiversity while mitigating air and dust pollution. This means restoring the wetlands and marshes along with the establishment of floodplain forest community and grasslands. Khudsar says bamboo (Dendrocalamus strictus) is part of the Yamuna floodplain species along with Arjuna (Terminalia arjuna), Jamun (Syzyzium cumunii) and so on.

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