A perfect `waste to wealth' story. The Raichur thermal power station uses the fly ash it generates to manufacture mosaic tiles.

Bharathi Ghanashyam

Despite the established uses of fly ash and stringent policies to support its utilisation, overall fly ash utilisation in India stands at about 15 per cent of the quantity generated.

The Centre for Ash Utilisation Technology and Environment Conservation (CASHUTEC), situated adjacent to the Raichur Thermal Power Station (RTPS), is bustling with activity. In one section of the big shed, new mosaic tiles are being pressed into shape; in another, batches of air-dried tiles are being transferred into big water tanks where they will cure for a period under water. While the procedure for manufacturing these tiles is the same as that for the conventional ones, the difference is in the ingredients used.

A significant quantity of fly ash has been used in place of cement; doing so , almost 30 per cent of cement has been saved without compromising on the tile quality. In fact, tests show that tiles made with a mix of cement and fly ash are stronger than those made with cement alone, and can be used for heavy-duty floors as well.

RTPS, one of Karnataka's major power plants, is owned by Karnataka Power Corporation Ltd and consists of seven units, each capable of generating 210 MW of power.

Deep inside the underbelly of the power plant, is an ongoing challenge that needs to be addressed on a daily basis. RTPS uses coal to generate power, in the process generating about 1.5 million tonnes of fly ash annually. This translates to more than 4,000 tonnes of ash requiring proper disposal every day.

This situation is not unique to RTPS alone. Seventy per cent of India's thermal power plants use coal to generate power. Indian coals are known to have very high ash contents almost 40-45 per cent; an estimated 100 million tonnes of fly ash are collectively generated from India's thermal power plants per year. Of this, 80 per cent is fly ash and 20 per cent bottom ash.

The conventional method used to dispose both fly and bottom ash is to convert them into wet slurry, and dump them into specially built ash-ponds around the thermal plants. While this may solve immediate disposal needs, it is fraught with long-term environmental problems.

Fly ash is a very fine powder and is known to pollute air and water, cause respiratory problems when inhaled and reduce yields when it settles on leaves and crops in agriculture fields around the power plant.

Ash-ponds require large tracts of land that could otherwise be used for agriculture. Water consumption also goes up while converting ash to slurry. Dumping of fly ash pollutes groundwater, as it contains many salts and metals, which, when dissolved in rainwater, can contaminate the groundwater.

Utilisation a safer option

Utilisation as opposed to dumping of fly ash can address the problem effectively. Research on utilisation of fly ash has proved its usefulness in various applications. Fly ash could be used in the manufacture of several products for the construction sector like blended cement, fly-ash bricks and mosaic tiles.

While the use of cement cannot be completely avoided, for certain products like mosaic tiles the substitution can go up to 50 per cent. This results in substantial savings on raw materials and the products are proven to be stronger and more cost-effective.

Fly-ash products are also environment friendly. A case in point is fly ash bricks. When conventional clay bricks are produced, they consume large amounts of clay. This results in the removal of topsoil and deterioration of the quality of agricultural land. Fly-ash bricks, on the other hand, do not require clay and result in the preservation of topsoil, as well as productive utilisation of fly ash.

In recognition of the problems that arise out of fly ash dumping, and to encourage its use by the construction industry, the Ministry of Environment and Forests has passed stringent notifications on the utilisation of fly ash. It has also set a time limit for compliance with the notifications. Notable among the attempts being made to utilise fly ash in the country is the effort at RTPS.

"Despite the established uses of fly ash and stringent policies to support its utilisation, overall fly ash utilisation in India stands at about 15 per cent of the quantity generated. Efforts are on to improve the situation, and we have sought to initiate sustainable optionsat RTPS," says R.R. Chousalkar, Executive Director (Thermal), RTPS.

RTPS, in collaboration with the Indo-Norwegian Environment Programme (INEP), has set up CASHUTEC, a technology demonstration centre, in Raichur. The centre aims to demonstrate the varied applications for fly ash in the construction sector including fly-ash bricks, blocks, interlocking pavers and mosaic tiles.

CASHUTEC also functions as a nodal centre for the development, demonstration, training and transfer of technologies for fly ash utilisation in India.

For more details, contact the author atbharathiksg@gmail.com, or cs@karnatakapower.com

(This article was published in the Business Line print edition dated August 4, 2006)
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