New Delhi: Spread across nearly 900 acres, the fly-ash pond at

thermal power plant is a green anomaly. Despite the thousands of

growing around, there is little one can do to prevent the

ash from being dispersed by the wind. Experts have pointed a finger at it as being a factor in the city's polluted air, and plant officials are keen to have the ash utilised, but there is too much of it, having accumulated over four decades, with some dunes reaching as high as 15 metres from the ground.

Fly ash is a by-product of coal burnt to generate power. When the Badarpur thermal power plant was started in the early 1970s, no one foresaw any problems because the plant was surrounded by barren land. From the '80s, however, slums and unauthorised buildings started coming up in the vicinity. Being very minute, experts said, fly ash tends to remain airborne for a very long period and can lead to serious health problems when inhaled.

"Despite using water sprinklers and planting thousands of Ipomoea plants, there is no way to stop fly ash from being airborne, especially during dust storms," conceded an official of

Thermal Power Corporation, which runs the plant. At present, there are approximately 250 lakh metric tonnes of fly ash in the pond.

Clearing the fly ash is a priority, and

said that in the last few years, the total ash utilisation of the plant has been more than 100%. "The ash is being used in the laying of the Delhi-Agra Highway and for ash-brick manufacturing," said a senior official. "In 2015-16, the total ash utilisation was 6.68 lakh MT against the production of 5.12 lakh MT."

NTPC is banking heavily on the eastern peripheral road project to deplete the ash. "If the project materialises, it can use up all the accumulated fly ash," said a top official. "The requirement for such a project would be 280 lakh metric tonnes. We are able to use the newly generated fly ash, but the pond has 45 years of collected ash. We aim to have the whole quantity used within two years."

To make the ash more useful, an officer explained that the Badarpur plant installed Electro Static Precipitators to collect the fly ash in a dry condition, which is preferred by cement industry for use in construction material. The coarser ash, significantly less than dry fly ash in quantity, is discharged into the pond."

Almost 90% of the fly-ash pond area has been developed into a green belt with the planting of Ipomoea and other shrubs. The area is criss-crossed by pipes of a sprinkler system that moistens the dusty ash and keeps it from being blown away. There are also sand filters to ensure minimum fly ash becomes airborne.

Because of the fly ash problem, there have been demands for closing down the plant. On its own, it is also facing a bleak financial future, and insiders say operating it might not be viable beyond five years. "The power distribution companies only schedule purchases from us in peak seasons, specially summer. Else, they schedule power from Badarpur barely 60% of the time," said a plant official. Absorbing the fixed costs for the rest of the time doesn't make for a good bottom line.