Cleantech: The leading edge

Power plants in the country have long been experimenting with innovative ways to utilise fly ash. Though considered a hazardous by-product, it has proved to be a useful input in cement manufacturing, road building and house construction. With each passing day, its applications seem to be further expanding and even finding their way into green initiatives.

It is estimated that for every mega watt of coal generated, about 5-6 tonnes of fly ash is produced. About 30-35 per cent of fly ash that gets generated goes into cement manufacture, including Pozzolanic cement mortar and concrete, 12 per cent respectively is used for mine filling and brick making, 11 per cent finds its way into low lying areas and about 3 per cent is utilised for agriculture.

NTPC Limited, the country’s largest power company, and various other power generation companies — both private and State-owned are seeking innovative ways to engage locals and help them turn into fly ash entrepreneurs. As a business proposition, they transform the substance into bricks and light weight concrete structures to be used by the construction industry.

Alind Rastogi, Chief Forest Officer and Executive Director, Environment and fly ash, NTPC, who is driving the in-house green initiative says, “There is vast potential to use fly ash-based bricks and other products in the infrastructure development taking place in the country and in real estate. Together they can boost fly ash use.”

However, apart from tried and tested applications, fly ash is now finding new avenues of usage. These include stowing of ash into abandoned coal mines, using it for railway embankments and ash based bituminous roads, flux bonded bricks and tiles and mine filling.

In 2009, the Ministry of Environment and Forests also provided guidelines on fly ash utilisation wherein it advocated its usage within 100 km radius of thermal power plants for construction, embankment and reclamation of low lying areas and for back filling of underground and open cast coal mines.

The other way was to try and reduce the output of fly ash at the power plant itself. K Vijayanand, Managing Director of AP Genco, explains what they did. “One of the bigger problems is the coal sourced from domestic mines, which have content of about 30-40 per cent as against 10-15 per cent in imported coal. One way we address this challenge is by blending domestic coal with imported coal. This brings down the fly ash output. “

Rastogi says, over the years, NTPC has utilised the material from its Unchahar project in Allahabad for by-pass road projects executed by NHAI, from NTPC Badarpur for the Noida-Greater Noida Expressway, Yamuna Expressway and Badarpur flyover. In addition more than 15 lakh cubic meters has been used by Delhi Metro Rail Corporation. One of the challenges faced when using fly ash is the transport cost. If the project location is say 100 to 150 km away it adds tremendously to the cost. Therefore, local entrepreneurs are being encouraged to make use of the fly ash generated from power plants as close to the utility as possible.

In collaboration with IIT-Kanpur, use of fly ash has been tried for the manufacture of pre-stressed railway concrete sleepers and development of ash based bituminous roads and flux bonded bricks and tiles at Ramagundam. Ash is also being used in the manufacture of high-density polyethylene (HDPE) products through IIT Delhi.

Interestingly, fly ash has found its way into agriculture as a soil modifier and source for micro and macro nutrients. This has been demonstrated through projects in collaboration with farmers and guidance of agriculture universities, Annamalai and ND University of Agriculture and Technology.

Various crops have been grown and harvested in varying agro climatic conditions and different soil-crop combinations and successful increase in crop yields have been demonstrated.

As power plants continue to innovate while seeking to address the issue of mounting fly ash in their backyard, they are also engaging local people to make entrepreneurial use of the material.

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