Thermal power contributes to almost 60 per cent of our electricity needs. In India, low-ash high grade coal is reserved for the metallurgical industry. TPPs, therefore, are compelled to use high-ash low grade coal often with as high as more than 40 per cent ash content. Depending upon the boiler design and efficiency, the ratio of fly ash to pond ash varies between 70:30 to 80:20.

With power production slated to double by 2020, the amount of waste produced will be enormous. With lack of adequate disposal facilities, this waste is going to be a national hazard with alarming consequences. Presently, over 65,000 acres of land is already occupied by ash ponds. Apart from land pollution, dumping of all and any type of ash is also a source of air pollution. The situation is especially aggravated during the summer months when fine particles of ash suspended in the air are a major source of lung and heart diseases. They also cause quick damage to fruit-bearing trees and agricultural harvest. Dumped ashes in ponds are also a source of ground water pollution due to leaching of the heavy metals present.

Though PCA is a waste product for the power sector, it finds utility as a raw material in other areas also. PCA has been primarily used in the construction sector for roads, embankments, dams, dykes, cement and building material manufacturing. However, a very small percentage of the ash generated is actually being utilised, in spite of its huge potential.

PCA is classified into three types depending upon its particle size and zone of collection.

FLY ASH: The extremely fine ash ‘flying’ along with the flue gases is trapped in electro-static precipitators (ESP)

POND ASH: The relatively coarser ash generated at the bottom of the boilers is mixed with water, made into slurry and pumped into the fill sites or ash ponds. This ash forms the bulk of the ash generated.

Realising the problems arising out of fly ash generation, as well as the opportunities presented, efforts have been taken by the Government of India and other agencies to look at productive utilisation of this ‘environmental hazard’.

The Government of India came out with a notification in September 1999 vide number S.O. 763 (E) pertaining to the dumping and disposal of fly ash discharged from coal- or lignite-based TTPs on land. Subsequent modifications in August 2003 and November 2009 issued directions for restricting top soil excavation for brick production and promoting fly ash use in building materials and construction activities within 100 km of TTPs. Recognising the importance for restricting the excavation of the top soil for manufacture of bricks and promoting the utilisation of fly ash in the manufacture of building materials and in construction-related activities, it was notified to compulsorily utilise 25 per cent by weight of fly ash in burnt clay fired brick making within a radius of 100 km from a coal- or lignite-based thermal power plant.

The September 1999 notification directed TPPs to supply fly ash free of cost to building materials manufacturers, the construction sector and the cement industry. The new notification of 2009 authorises TPPs to sell fly ash through a bidding process, while allocating 20 per cent of fly ash generated for the brick industry free of charge keeping in mind the problems faced by this unorganised sector. TPPs are directed to maintain and utilise funds for creating infrastructure and facilities for fly ash utilisation. Existing units have to reach a target of 100 per cent utilisation in five years, i.e., by 2014 while new units have to achieve it within four years of being commissioned.

Amendments to the 1999 notification made it mandatory for any construction within 100 km of a TTP to use only fly ash based bricks instead of red clay bricks. This is applicable for all public as well as private construction activities based on the availability of fly ash. Clay based products are directed to have at least 25 per cent fly ash by weight of the total raw material, whereas those without clay have to have a minimum of 50 per cent fly ash by weight. They are subject to the concessional excise duty of 1 per cent as per notification No.1/2011-Central Excise.

The pulverised ash brick (PAB) technology is a process of converting industrial waste materials into quality building materials. Over the last two decades, there has been substantial work done across the country in utilising this material. Even the Government of India has constituted a Fly Ash Mission to promote the use of this waste in an environmentally sustainable manner. The Development Alternatives (DA) Group has also been working to utilise this waste in a profitable manner. Unlike other organisations, DA has provided emphasis on the ‘technology’ part of the developed process building upon the innovations from other organisations. Thus, the developed technology provides emphasis on ‘design engineering’ rather than ‘compositional variance’. Focus of the technology developed by DA aims to sustain the SME sector through providing quality solutions at affordable costs.

The process of fly ash block making is a true example of ‘waste to wealth’. With the exception of lime, all the raw materials used are wastes. Fly ash is the waste from TPP, Phosphogypsum is a waste from fertiliser industries and sand is available as a waste material from river beds. In some cases, even waste lime from oxygen and paper industries can be used. The PAB technology uses dry ash (fly ash) collected from ESP or silos of thermal power plants; filler materials – usually coarse sand or stone crusher dust and additives in the form of lime, gypsum or cement. Strength of the bricks can be engineered by varying the compositions. The equipment used can be either manual or mechanised. Mechanised machines deploy hydraulic compaction to produce a variety of bricks and can be operated through electric or diesel power.

The technology is of very small scale investment aptly suitable for micro and small scale enterprises and has a payback period of around 2 years. Thus, it is attractive from the bankable finance viewpoint, attracting public and private finance.

Thus, there is a substantial favourable regime for promotion and use of fly ash as a resource material. However, the present scenario of fly ash bricks speaks a different language. Despite the promotional regime, the uptake of fly ash brick making enterprise has been extremely poor. Over two decades of fly ash mission work has produced fewer enterprises than research papers. With the lead taken by research institutions, the prolific publication is expected.

Discussions with entrepreneurs in various waste-producing states, e.g., Odisha, Chattisgarh, Maharashtra, Jharkhand and West Bengal have spelt out the dearth of proper technology. The manufacturing market has been liberated with profuse machines flooding the market. They are of various techniques and capacity. However, the basic theory is to use compaction in the form of hydraulic or mechanical pressure. Inspite of these appropriate machines, the quality of bricks being produced is extremely poor. They are of much inferior quality to even red clay fired bricks. In some places in Odisha, the fly ash bricks being produced gave strength of only around 15-25 kg/cm2. Purists may term these as aberration of results. However, this quality of bricks is very common and not merely an exception.

In some cases, the result of such poor quality rests entirely on the entrepreneur. In an effort to make quick profits, the additive (lime, gypsum or cement) quantity is compromised. However, in most of the cases, the reason of poor quality is ‘lack of technology’ starting from the choice of raw materials to the composition selection, the mixing process and even the curing method. It has been proved by the technology team of DA that better properties of a fly ash block can be achieved not by increasing the additive content but by proper mixing and curing. This is the often forgotten part of the entire process, resulting in poor quality bricks.

New approaches to operational practices require a paradigm shift from the conventional practices and the mentality of conducting regular business, thereby integrating the entire process of innovations with new technology process. Change in mentality, technology innovations and trained human resources are the most valuable assets of utilising waste in a business like manner. This will not only help in benefitting the enterprises but also improve the environment. However, the advantage of all this can only happen if both the entrepreneur and society is ready to change its mind set and working habit. All this requires extensive awareness, widespread demonstrations, intensive training and long-term technology support along with making both users and entrepreneurs learn, practice and adopt improved technology options. q