NIDHI JAMWAL looks at ways to utilise flyash, and so combat a polluting scourge

-- Every year Indian thermal power plants (TPPs) spew out 100 million tonnes of flyash, a grey outpour soon expected to reach 175 million tonnes. According to current estimates nearly one lakh hectares (ha) of land in India is taken up by ash ponds. Bad news for the environment. For, most of the flyash is disposed off in ash ponds, from where it contaminates both surface water and groundwater. As if that isn't bad enough, exposure to flyash has been linked to diseases such as silicoses, fibrosis of the lungs, cancer and bronchitis.

Flyash is a byproduct of coal combustion. TPPs powered by this fossil fuel are the mainstay of India's power sector. In 2002, out of a total of 1,04,917.50 megawatts (MW) of electricity generated in India, 74,428.82 (MW) was generated by TPPs alone. According to a report titled Clean Coal Initiatives by the New Delhi-based Central Pollution Control Board, 70 per cent of electricity generated by TPPs is through coal. Indian coal has high ash content (45 per cent); ergo, more flyash.

With coal expected to drive the power sector in India at least till 2012, flyash is a matter of grave concern. According to some experts, utilising flyash mitigates its harmful effects. Says K Basu, a former scientist with Bharat Heavy Electricals (BHEL), Hyderabad, "We have the technologies to increase flyash utilisation. What we need is to integrate the chain of coal consumption, flyash generation and flyash utilisation. Also we need policies to make flyash products more profitable." But many question flyash usage on grounds of environmental safety. Flyash is an alumino silicate glass consisting of the oxides of silicon, aluminium, iron and calcium with minor amounts of magnesium, potassium, zinc, sulphur and other trace elements. These elements can leach into the environment, enter the food chain and affect human health.
Promoting flyash... In 1994, the government of India started the flyash mission (FAM) -- under the Technology Information Forecasting and Assessment Council of the Department of Science and Technology (DoST) -- with the aim to increase flyash utilisation in the country. According to Vimal Kumar, director of FAM, "The launch of FAM has given a boost to research on technologies for flyash utilisation, which has increased from three per cent in early 1990s to 25 per cent in 2003." Many premier institutions such as the Central Road Research Institute (CRRI), the Central Building Research Institute (CBRI), the National Thermal Power Corporation (NTPC) and BHEL have developed technologies to increase flyash utilisation in the country. The Bureau of Indian Standards (BIS) has developed specifications based on which flyash can be used for various applications.

Flyash possesses pozzolanic properties. Pozzolanas are artificial or naturally available materials which react with lime and water to form cementatious compounds. This property makes it suitable for various applications (see graph: Using flyash). According to the Technology Information, Forecasting and Assessment Council (TIFAC), utilisation of flyash for various applications can save US $1.2 billion per annum.
... in roads and mines
Experts feel that the best way to make bulk use of flyash is for construction. Research shows that when mixed with soil, flyash can be used as sub-base while constructing roads/embankments. According to a paper, Management of fly ash in Delhi Vidyut Board, "by utilizing flyash in roads and embankments, not only the problem of disposal of flyash can be reduced, but demand of land for flyash dumping would be reduced. The soil -- which is a scarce resource -- would also be saved. When soil is treated with lime alone, there is a possibility of leaching of lime, but if flyash is added to it the leaching of lime gets inhibited". Studies conducted by CRRI show that a proportion of 1:2:9 of lime, flyash and gravel/sand yields good results.

"Flyash can be used for road and embankment construction. The fear of leaching of heavy metals and other contaminants is least as layer of soil/clay follows the layer of flyash. And all this is compacted well," says K C Sahu, retired professor from Indian Institute of Technology (IIT), Mumbai. FAM has assisted entrepreneurs in the construction of roads, embankments and flyovers using flyash -- the Nizamuddin bridge approach road embankment and the Sarita Vihar flyover in New Delhi, and the Raichur-Arsnagi road in Raichur district of Karnataka are some examples.

Using flyash for construction activities saves topsoil, and this has economic benefits. Estimates point out that there can be 30-40 per cent saving in expenditure if flyash is used in constructing embankments. For instance, in constructing the 1.7 kilometres (km) long and 8 metres (m) high Nizamuddin bridge embankment about 1.5 lakh cubic metre flyash was used, which lead to a net saving of Rs one crore, in no way a unique fact (see table: Flyash is a good bargain).

Flyash is a good bargain

Specifications Cost
(in Rs)
Savings
(%)
Bottom ash 1,31,825 50.88
Soil: Bottom ash (1:2) 1,34,025 50.07
Lime: flyash: soil (3:9:88) 1,35,765 49.4
Water bound macadam (WBM)* 2,68,428  

Note: * this is the conventional way of constructing roads.
Source: R K Swami et al 2000, Use of coal ash in road construction, in 2nd International Conference on flyash disposal and utilisation, Central Board of Irrigation and Power, New Delhi, p6.

Flyash is also utilised to reclaim low-lying areas and mines. For instance, the Indian Oil Corporation (IOC) has used three lakh cubic metres of flyash to raise the low-lying area adjacent to the Yamuna river near Badarpur in New Delhi. The ground elevation has been raised by 2.5 m using compacted flyash, which is now covered with 0.5 m of local soil. Similarly, NTPC's Centre for Power Efficiency and Environmental Protection has carried out studies to examine the environmental feasibility of using flyash to fill abandoned open-cast coal mines -- Gorbi mines (two pits) -- in the Singrauli region straddling Uttar Pradesh and Madhya Pradesh. The study concludes: "flyash in conjunction with local soil and other materials can provide an excellent solution... (it would) provide conditions for afforestation in the area". Environmentalists, however, are skeptical. "Filling mines with flyash might lead to leaching of heavy metals into the groundwater. This needs to be carefully addressed," says Sahu.

... in bricks and cement
India has a huge potential to utilise flyash bricks. The 180 billion bricks made today consume about 540 million tonnes of clay. Utilising flyash bricks could minimise such consumption. A typical flyash brick consists of 55-60 per cent flyash, 20-30 per cent sand/stone dust, 10 per cent lime and 5-6 per cent gypsum. India annually manufactures 600 million flyash bricks but can make about two billion. This would consume five million tonnes of flyash and lead to a net saving of Rs 20 crore per annum. "Flyash bricks do not require baking in kilns, hence they consume minimal energy. Also the cost of a flyash brick at Rs 1.10 is comparative with a clay brick," says Anil Arora, director of En-Friend Ask Bricks Co, Delhi.

Construction companies today do use flyash bricks. The oldest example of such construction is the housing colony of the Neyveli Lignite Corporation near Pondicherry, built in the 1960s. But some experts contend that flyash bricks may not be as strong as clay bricks. According to Sahu, when flyash comes into contact with water, the alumino-silicate along with sodium, potassium and calcium in ash particles forms a thin layer of polysialate (mineral layer) over the ash particles over a period of time. This layer is likely to decrease inter-particle cohesion between ash particles, making the bricks weaker in the course of time. Structures built with such bricks could, therefore, collapse.

But TIFAC claims that it has got flyash bricks tested by institutes like the Roorkee-based CBRI, the Bhopal-based RRL, Dhanbad-based Central Fuel Research Institute (CFRI), and results prove that flyash bricks are in no manner inferior to clay bricks. Arora feels the same.

There's another way to use flyash. "As much as 35-65 per cent flyash can be blended with cement," says a senior official of DoST. BIS is also encouraging such blending. Until 2000 it allowed only 25 per cent blending of flyash. This has now been raised to 35 per cent. But many government agencies are still skeptical about the safety of this usage. They claim that due to poor quality of Indian flyash, blending it with cement might reduce the structure's strength. "During the 1970s, the Central Public Works Department (CPWD) banned use of flyash blended cement in reinforced cement concrete due to apprehensions of corrosion. But that could possibly be reviewed now," feels Basu.

Flyash is also being used to make precast products. Concrete pipes made with flyash are considered more watertight and more resistant to weak acids and sulphates as compared with the plain portland cement ones. "The use of flyash for cement/concrete applications does offer a way out, because once the flyash is mixed, it gets "fixed" or "bound" with the rest of the mixture, and cannot therefore leach out into the external environment," says Debi Goenka of Bombay Environmental Action Group, a Mumbai-based non-governmental organisation (NGO).

But is that enough?
Clearly there is no dearth of technologies for economical use of flyash. Flyash utilisation has increased, but India lags far behind many industrialised countries. For instance, Denmark utilises 70 per cent of the flyash it generates; France and Britain utilise 65 and 60 per cent respectively.

The Indian government is also keen to improve its standing in flyash utilisation. In September 1999 the Union ministry of environment and forests (MOEF) notified that 'no person within a radius of 50 km from a coal- or lignite-based TPP shall manufacture clay bricks/tiles/blocks for use in construction activities without mixing at least 25 per cent of ash with soil on weight to weight basis'. The TPPs had to make available ash for at least 10 years from the date of the notification. Also the exiting TPPs had to, within a period of 15 years from the date of publication of notification, achieve 100 per cent utilisation of flyash. But till date this notification remains unimplemented. And it is currently under review. As per the revised draft of November 2002, the notification will now apply up to 100 km radius around a TPP. And all the TPPs have to ensure 100 per cent flyash utilisation by December 2005. There is also a proposal to ban digging topsoil. But experts claim that the revised notification will remain only on paper. "The government has failed to implement even the 50 km notification, how does it intend implementing 100 km notification? They can go ahead and notify an area of 200 km, but what use will it be if it remains unimplemented?" questions a member of Delhi Brick Kiln Owners Association.

TPPs are no better. " TPPs have budgetary allocation for flyash disposal. Due to various reasons (read corruption) they do not want to bring down their budget," says a Delhi-based flyash brick manufacturer. He informs that the Badarpur Thermal Power Station in New Delhi has recently acquired 500 acres of land for flyash disposal. It already occupies 100 acres of land as an ash pond. Elsewhere in the country, flyash seems to be pure waste: according to the Tamil Nadu Industrial Development Corporation, the state recklessly discharges almost 94 per cent of the flyash into the sea.

To make flyash utilisation attractive, the central and state governments are providing financial incentives to entrepreneurs. Bricks using more than 50 per cent flyash have been exempted from excise duty. The Orissa government has exempted flyash bricks and other flyash products from sales tax. It has also banned use of soil for brick manufacturing up to 70 km of a TPP. Rajasthan government recently issued a notice stating that 'flyash bricks can be used in place of clay burnt bricks as and when required'

Flyash utilisation is also being promoted under the Pradhan Mantri Gram Sadak Yojna, which aims to link every habitation with a population greater than 1,000 and 500 in the country by the year 2003 and 2007 respectively. For the same, the Union ministry of rural development has published a manual on flyash utilisation for making rural roads. But experts opine that till the time flyash utilisation in road construction is not made mandatory, contractors will continue to use topsoil .

Flyash brick manufacturers in Delhi complain that in spite of huge potential their business is still lukewarm. Why don't government agencies such as the Delhi Development Agency (DDA), CPWD, Municipal Corporation of Delhi (MCD) promote flyash bricks? "It is easy to make money in a project if the tenders call for clay bricks as there are various qualities of clay bricks available in the market. And flyash bricks has no such varieties, hence no possible cuts," points out a manufacturer. He claims the only thing lacking is administrative will. He voices the concern of brick manufactures in Delhi, labelled as 'polluters' by the Supreme Court of India in November 1996 and directed to shut down their units. "Today we want to become 'eco-friendly' by manufacturing flyash bricks, but are facing administrative problems. Hence our products keep lying in the godown for months together," he adds. At present, the Rajghat power station in Delhi has close to 80 lakh flyash bricks stocked at its premises, with no buyers.

And is that safe?
Flyash utilisation, no doubt, has economic viability. But is it a safe and long term solution? Some contend that it is not. "Flyash bricks contain gypsum which is radioactive. Houses constructed of such bricks might be exposing people to high levels of radiation," says Nitish Priyadarshi, a Ranchi-based geologist. Others fear that heavy metals present in flyash might leach out into the environment. But Kumar claims that their presence is in parts per billion, which do not pose such danger.

Another controversial application is utilisation in agriculture and plantations. TIFAC projects show that application of flyash has increased oil seed yield by about 10 per cent per hectare in the sunflower crop at Raichur. It has also witnessed a 20 per cent increase in wheat yield at Farrakka, West Bengal. Flyash contains micronutrients, required by the plants during growth and the Hyderabad-based National Institute of Nutrition has proved this as a safe practice, explains Kumar. Striking a discordant note, Goenka says that adding flyash to soil for agricultural purposes might lead to uptake of heavy metals by the plants.

So what do we do?
Keeping in mind the views of all the groups, a long-term strategy to deal with increased flyash generation in the country needs to be developed. FAM alone cannot deliver. It is time various ministries such as the Union ministry of power, Union ministry of coal, MEF, and DoST work together to develop a comprehensive programme.

While promotion of flyash goes on, the aim should be to minimise its generation. This is where clean coal technologies come into play, which will not only increase efficiency of TPPs but also reduce flyash generation (see: Shunned solutions, February 28, 2003). But due to their expensive nature, they are not much on the government' agenda. We also need to relook our energy consumption patterns, which at present leads to high flyash generation. "The way buildings are being constructed, they consume a lot of energy to run their cooling and heating systems. This means more and more coal consumption and flyash generation. This cycle needs to be broken," says a New Delhi-based architect. But all this requires strong political will. Does government have it?

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