Archives-Fly Ash utilization in India

Published on 11/05/2011

First Update 16/03/2017

Archived on 15/09/2020

Global Coal reserves are expected to last another 200 years. India also has a vast coal reserve of 211 billion tones making coal one of the most extensively used fossil fuel for generating power. With 40 % to 50% ash content in Indian, coal this presents an inherent problem of ash disposal. Power plant ashes are generated as the finer pozollanic (capacity to react with lime in the presence of water at room temperatures to form a solid and water insoluble cement like substance) FLY ASH or the coarser non pozollanic bottom ash .Both these ashes are generally mixed and disposed in ash ponds requiring large areas of land.. More than 175 million tones of fly ash are expected to be generated in the country by the year 2012. This would require about 40000 hectares of land for the construction of ash ponds. The wet slurry system downgrades the pozollanic property of fly ash. It has high water requirements also and fails to recognize the utility of bottom ash. Generally one acre land is needed per M.W. of power production. The Ministry of Power, Govt. of India estimates 1800 million tones of coal use every year and 600 million tones of flyash generated by 2031-2032.

The Fly-ash mission was commissioned in 1994 with the Department of Science and Technology as the nodal agency and the Technology Information and Assessment Council (TIFAC) as the implementing agency. The Ministry of Environment and Forests, Govt. of India, Ministry of Power, Thermal Power stations, R&D Institutions and Industry together have launched a Technology Project in Mission Mode (TPMM). Their focus is on the demonstration of coal ash related technologies for infusing confidence and thus ensuring large scale adoption.

Recognizing the reutilization of fly ash, the huge pressures on land and water and the grave environmental consequences, power plants are shifting to separating the bottom ash and the fly ash and collecting ash to send it to alternative users. As a result of the efforts of the ‘Fly Ash Mission, in India and some other agencies the utilization of fly ash has improved from 3% in 1994 to 27%in 2003. From a little over one million tones in 1993-94 the utilization rose to 22 million tones in 2002. Fly ash utilization increased further to 60 million tones per year in 2006-2007 as against a generation of 130 million tones per year. While there has been a constant increase in the utilization of fly ash yet the unutilized fraction is also growing considerably increasing from 39 million tones in 1993-94 to 70 million tones in 2006-2007. This has grave environmental consequences. A lot still needs to be done. More than 55 demonstration projects have been completed or are under consideration at the fly ash mission. Some of these include use of fly ash in mine filling, construction of roads/ flyover embankments, hydraulic structures, raising of dykes, manufacture of several building components like bricks, blocks, tiles and use in agriculture.

Fly ash utilization has great potential to lower green house gas emissions by decreased mining activities and reducing Carbon dioxide production during manufacture of materials that can be substituted by fly ash.

Fly ash holds a potential to improve the physical health of the soil. It can serve as a soil modifier and also enhance the water retaining capacity and fertility of the soil. It improves the plants water and nutrient uptake; helps in development of roots and soil binding, stores carbohydrates and oils for use when needed, protects the soil from soil borne diseases and detoxifies contaminated soil. Use of Fly ash in agriculture can increase the yield of cereals, oil seeds, pulses, cotton and sugarcane by 10-15%, vegetables by about 20-25% and root vegetables by 30-40%. Waste lands, degraded lands, saline alkaline soils, eroded soils etc., can be successfully reclaimed by fly ash.

Fly ash can substitute up to 66% of cement in the construction of dams. It is also used as a pozollanic substitute for cement in Roller Compacted Concrete dams-an innovative dam technology developed as a result of efforts to design more economical concrete dams that could be constructed rapidly with designed performance. Fly ash in R.C.C. is used not only for saving cement cost but also for enhancing strength and durability. Replacement levels of fly ash primarily Class f, range from 30-75% of total cement material. Fly ash can also be used in Portland cement concrete to enhance the performance of the concrete. Portland cement is manufactured with Calcium oxide, some of which is released in a free state during hydration. As much as 20 pounds of free lime is released during the hydration of 100 pounds of cement. This liberated lime forms the necessary ingredients for reaction with fly ash silicates to form strong and durable cementing compounds thus improving many of the properties of concrete. Typically 15-30% of the Portland cement is replaced with fly ash. This results in net reduction in energy use and green house gas and other emissions.

Studies show that one ton of Portland cement production discharges 0.87 tonnes of Carbon dioxide in the Environment. Another Japanese study indicates that every year barren land approximately 1.5 times of the Indian Territory need to be afforested to compensate for the total global accumulation of Carbon Dioxide discharged into the atmosphere because of total global cement production. Utilization of fly ash in cement concrete minimizes the Carbon dioxide emission problem to the extent of its proportion in cement.

Fly ash from coal fired Thermal power plants is an excellent material for the manufacture of other construction materials like fly ash bricks, mosaic tiles and hollow blocks. The manufacture of conventional clay bricks requires the consumption of large amounts of clay. This depletes top soil and leads to degradation of land.

180 billion tonnes of clay brick production per year consumes 540 million tonnes of clay, makes 65000 acres of land barren, and consumes 30 million tonnes of coal equivalent, generates26 million tonnes of Carbon Dioxide. A 10% switchover to fly ash bricks will use 30 million tonnes of fly ash every year, save environment and coal and yield a benefit of 300 crores by way of reduction in brick cost production.

Except for Fly ash-clay fired bricks, fly ash bricks do not require clay and serve the dual purpose of conserving top soil and the constructive utilization of fly ash. Technologies are also on verge of entering the markets for manufacture of cementing material as well as fly ash bricks with fly ash content as high as 90%.Orissa Government in India has banned the use of soil for the manufacture of bricks up to 20 km. of a thermal power station. In the case of fly ash-clay fired bricks, a mixture of clay and fly ash is fired. The unburnt carbon of the fly ash serves as fuel for burning. Approximately20-30% energy can be reduced by adding25-40% flyash.

The World Bank has cautioned India that by 2015 disposal of coal ash would require 1000 square km. or one meter square of land per person.

Some of the high volume applications of fly ash are for use in paving, building embankments and mine fills. Utilizing fly ash in roads saves top soil, avoids creation of low lying areas, does not deprive the nation of the productivity of top soil and reduces the demand of land for fly ash disposal.

The use of fly ash in the Nizamuddin bridge road embankment at Delhi, India for about 2 Kms. and a height of 8 meters in a flood zone has demonstrated the use of fly-ash in adverse conditions. This has not only saved the top soil and used fly ash which was otherwise a waste but also saved Rs. 1.4 crores in a total project of Rs. 10 crores.


Fly ash-Lime-Gypsum bricks are manufactured using the properties of the mixture as an ‘Hydraulic Cement’ meaning thereby that it sets and hardens in the presence of moisture and on the lines of Portland cement, gets stronger with age but unlike clay bricks does not need sintering. Nearly 200 tonnes of coal are needed to sinter one million clay bricks, a process that liberates over 180 tonnes of Carbon dioxide. The production process of fly ash lime gypsum bricks eliminates this process and has the potential to earn carbon credits in return. Air-water cured bricks are of similar qualities as clay fired bricks and 20 to 25 paise cheaper. Steam cured bricks are of much superior quality as compared to wire cut clay bricks and cheaper by 25 to 50 paise than wire cut bricks.

Cellular light weight concrete blocks are used as a substitute to bricks and conventional concrete blocks. This is a foaming agent based technology from Germany using Fly-ash (to the extent of1/3rd to 1/4th of the total materials constitution), sand, water and foam manufactured from biodegradable foaming agents. Foaming agent and foam generator if used for the production of Cellular light weight concrete blocks with more than 25% content of fly ash is eligible for concession in import duty by the Government of India. The blocks have a better strength to weight ratio and reduce dead load resulting in a saving of steel and cement costs and in reduction in foundation size. It has better acoustics and thermal insulation (Air conditioning requirements are considerably reduced). There is a saving in mortar and it has a higher fire rating.

Fly ash based polymer products are also being used as wood substitutes. They have been developed by using fly ash as the matrix and jute cloth as the reinforcement. The Jute cloth is laminated by passing through a polymer fly ash matrix and then cured. The number of Laminates is increased to get the desired thickness. The product can be use in many applications like door shutters, partition panels, flooring tiles, wall paneling and ceiling. The developed material is stronger more durable, resistant to corrosion and cost effective as compared to wood. This technology has been developed by the Regional Research Laboratory, Bhopal in collaboration with Building Materials and Technology Promotion Council (B.M.T.P.C) and TIFAC. One commercial plant has been set up based on this technology near Chennai, India.

The Government of India has withdrawn a 8% excise duty imposed earlier on fly ash products. Now no excise duty is levied on manufacture of goods in which a minimum of 25% w/w fly ash is used. Similarly for import of equipment machinery and capital goods required for the production of fly ash based products, additional customs duty has been exempted.


HUDCO and NHB are extending financial support to promote industrial units for production of building materials based on fly ash products.


Government of Orissa has exempted fly ash bricks and other products from sales tax.



Damle Anand, 2003: Use of Fly Ash in Burnt Clay manufacturing, Cleaner Technology, Impacts/12/2003-2004, MOEF-CPCB, Govt. of India, 2003 pages11-21


Kumar Vimal and Mathur Mukesh,2003 :Clean environment through fly as utilization. Cleaner Technology, Impacts/12/2003-2004, MOEF-CPCB, Govt. of India, 2003 pages235-255

TIFAC, 1995: Techno market survey on fly ash bricks

Most of the developing countries face energy scarcity and huge housing and other infrastructure shortage. Ideally in these countries materials for habitat and other construction activities should be energy efficient (having low energy demand). The following table shows some examples of energy savings achieved through the use of Fly Ash in the manufacture of conventional building materials. It should be noted that use of Fly Ash also improves the properties of building material, as mentioned above:

Energy Savings in the Manufacture of Building Materials through Use of Fly Ash

Building Material


Material Compared

Energy savings (%)

Portland pozzolana cement

75% Ordinary Portland cement

25% Fly Ash

100% Ordinary Portland Cement


Lime-pozzolana mixture

25% Acetylene gas lime

75% Fly Ash

25% Lime

75% Calcined brick


Calcium silicate brick

90% Fly Ash tailings

10% lime

(waste source)

Burnt Clay brick


Burnt brick

75% Clay

25% Fly Ash

Burnt Clay brick


Source: Building Materials in India: 50 Years – A Commemorative Volume, Building Materials & Technology Promotion Council, New Delhi, India, 1998

Conversion of fly ash into wealth generator

(Excerpt from President A P J Abdul Kalam’s
address to the nation on the eve of the country’s
56th Republic Day):

“As you are aware, the use of coal for power generation results in an increased quantum of fly ash production, which has reached about 100 million tonnes per year. All out efforts are needed to utilize this fly ash not only from environmental considerations, but also to avoid land usage for fly ash dumping. Though there has been a steady progress in fly ash utilization from 1990, we have a long way to go to reach the target of 100 per cent fly ash utilization. It is reported that the agricultural increase of grains is around 15 per cent, green vegetables 35 per cent and root vegetables 50 per cent, when fly ash is mixed with soil. Toxicity tests have proved that there is no toxic element due to fly ash. But it has higher nutrients due to increased availability of iron and calcium. Fly ash can become a wealth generator by making use of it for producing ‘green building’ materials, roads, agriculture etc. Full utilization of the generating stock will provide employment potential for three hundred thousand people and result in a business volume of over Rs.4,000 crore.”

Related Articles


  1. For information on a newly patented ceramic composition from coal fly ash, see: Waste Not, Want Not
    Ceramic Industry, August 2010
    Ross Guenther, General Manager, Ceramext LLC

  2. Fly ash utilization is social, Natinonal and Enviorenment saving movement. It should be grow very fast. We all ask for roads, dams and building with fly ash based technology.
    Best wishes,

    Sunil Mendhekar, Ashkings Enterprises, Nashik. 9373906867

  3. may i know does the machinery imported for manufacturing Light weight concrete, attract any indian customs duty , if its exumt what is the G/O or chapter code, thanks in advance

  4. is there is any central excise duty levid on cellular lightweight concrete. in which we used more than 25% fly ash. plz conformed as soon as possible

  5. The Government of India has withdrawn a 8% excise duty imposed earlier on fly ash products. Now no excise duty is levied on manufacture of goods in which a minimum of 25% w/w fly ash is used. Similarly for import of equipment machinery and capital goods required for the production of fly ash based products, additional customs duty has been exempted.

    Can you please let me know is import duty has been exempted for fly ash based machinery and if yes what is the duty and secondaly is the flyash brick exempt from exise

  6. As mentioned above – for import of equipment machinery and capital goods required for the production of fly ash based products, additional customs duty has been exempted.

    Can you please let me know under what act / section / notification can I find the same exemption ?

  7. I read a lot of interesting articles here. Probably you
    spend a lot of time writing, i know how to save you a lot
    of time, there is an online tool that creates high quality, SEO friendly articles in seconds, just search in google – laranitas free content source

  8. Dear Sir/Madam,

    My name’s Nguyen from Otran Group Company in Viet Nam.

    We, Otran Energy Company, are doing business in coal which supplying some power plants in Vietnam. We specialize in providing coal to be imported from Indonesia (Thermal Coal – Bitumin) and Australia.

    Vietnam now dismisses a huge amount of fly ash (15 – 20 million tons per year) and estimated up to 30 million tons per year by 2020. So we are looking for partners supplying services on dealing fly ash and our orientation is producing AAC bricks/blocks which are generated from this waste. We are now selling a small quantity of fly ash to some cement manufacturers and most of them have been buried.

    We’d like to cooperate with you on the delivery of fly ash dealing technology and AAC manufacturing to sell on the market for our environment protection.

    I’m looking forward to receiving your coordination.

    Thank so much.

  9. Dear All,
    I am working on utilization of Fly ash, pond ash, coal dust and coal ash as a stowing material in under ground mines. If i get success in this R&D project we can fill 100 % of fly ash in under ground mines. its the very interested project. We are preparing the proposal for this work.

    i am facing financial problem for chemicals purchase. I request to Indian Government or Private bodies please give support for this project.

  10. is there a way to personally buy ash frm thermal plants for the purpose of landfilling?i couldnt find a proper way as to how to initiate the process or whom to contact

  11. Dear sir,
    I wanna know about the flyash used in manufacturing of concrete door shutters. ….

  12. Dear Mr Manoj Kumar,
    There are new technologies in Finland to use Fly ash as agriculture manure.
    Is it possible in India. Interested persons could contact me to get the technology.

  13. please stop using fly ash as it comes from the thermal power stations because it is a radioactive material, i made an extensive research and patented, a process to extract nearly 17 products which are most useful.

  14. is there a way to personally buy ash frm thermal plants for the purpose of landfilling?i couldnt find a proper way as to how to initiate the process or whom to contact

    share if any details on my whats number 9960608621


Please enter your comment!
Please enter your name here

Stay Connected

- Advertisement -spot_img

Latest Articles