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.

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 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.

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.

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.

Sources:

www.dst.gov.in/whats_new/what_new08/fly-ash.pdf

www.parisaramahiti.kar.nic.in

www.tribuneindia.com/2000/20000217/science.htm

www.icrindia.org/?p=180

www.bmtpc.org/pubs/papers/paper4.htm

www.icjonline.com/may2007.htm

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

ENERGY SAVINGS AND ENVIRONMENTAL BENEFITS
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:

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.”

The synthesis of chlorophyll triggered a process in which the Carbon Dioxide present in the atmosphere (probably about 10000 times more than of now) entered a reaction with water in the presence of sunlight. This was the beginning of a transition from the chemoautotrophic, fermentative and anaerobic mode of metabolism to the autotrophic, photosynthetic and aerobic form of metabolism.

The process also heralded the way for the evolution of plants – for the fixation of carbon and nitrogen- the synthesis of biomass and all primary food production. Oxygen evolved as a by-product of the reaction but it took another about 0.8 billion years for earth to get free Oxygen. The all-important ozone layer was formed. As plant activity achieved dominance plant material became embedded in the lower crusts of the earth to finally form fossils. Coal is one such fossil, which has been thus formed.

Man in his quest for excellence, saw this coal and recognized its potential as a slave. He had discovered fire already. This was the beginning of the Industrial revolution- of smoking chimneys serving as signatures of prosperity and development. Little did man know that the process could recoil as a danger to mans very existence on earth. That man would eventually cut the very branch on which he is sitting. Electrical energy is a very important part of all development activity. 1995 estimates for the per capita consumption of electrical energy in India were 360 units which compares very badly with 6000 to 10000 units from the industrially developed countries. Estimates for the demand for power during1992-1997 reveals a demand of 1783989 million kWh, a supply of 1626544 kWh and a deficit of 8.8% on the demand. Indias coal reserves are estimated to be just about 1% of the worlds reserves while its population is 16% of the global population. India has a coal reserve of 200 billion tons and a current annual production of 295.93(1997-1998) million tons. Seventy percent of the total coal production and virtually the entire lignite production goes into power generation. In the early years of this century India will be producing 400 million tons of coal and lignite of which about 330 million tons would be needed for power generation.

Interestingly the production of coking and non-coking coals for 1962-1963 was just 55.23 million tons. About 75% of electrical energy is produced by the thermal power plants in India. Emissions from the combustion of coal are one of the basic environmental problems associated with the thermal power plants. The World Health Organisation has prescribed the following emission factors for thermal power plants: Particulates- 3.5(A) Kg. per ton of Lignite burnt; 8(A) Kg. Per ton of Bituminous coal burnt; 8.5 (A) Kg per ton of Anthracite burnt. Here A is the ash content of combustible coal by weight. Sulfur Dioxide- 15 (S) Kg. Per ton Lignite burnt; 19 (S) Kg. Of coal and Anthracite burnt. Here S is the percentage combustible sulfur by weight. Nitrogen Oxides- 7 Kg. Per ton of lignite burnt, 9 Kg. Per ton of Anthracite and 9Kg. Per ton of Bituminous coal. Hydrocarbons- 0.5 Kg per ton of lignite, 0.015 Kg. Per ton of Anthracite burnt and 0.15 Kg. Per ton of bituminous coal burnt. Carbon monoxide- The emission of carbon monoxide from all sources is prescribed as 0.15 Kg. Per ton.

 Indian coal has a high Ash content sometimes exceeding 40%and a Sulfur content ranging from 0.2 to 8 % with an average of 2%. With low conversion efficiency, thermal power plants release almost about 1.5 to 2 MW of thermal energy per MW of power produced in the environment. About 15 % of this is released along with the flue gases and the rest is discharged along with cooling water. It is estimated that a 500MW coal fired power plant having no pollution control equipment would emit nearly 100 tons of Sulfur Dioxide, 20 tons of Nitrogen Oxides and 6 tons of Ash daily. Existing power plants produce about 50 million tons of fly ash per annum needing 40000 acres of precious land for disposal of fly ash during their span of 30 years. Combustion products from thermal power plants have great environmental significance. Acidic gases have a tendency to form acid rain. While the problem of acid rain is not yet severe in India yet the increasing use of coal is likely to increase the possibility. Soot from chimneys has a low particle size and may tend to deposit in the tissues of lungs where it embeds itself, may stay for two to six weeks and in the process because of adsorbent capacities, adsorb acidic gases, heavy metals and other particulate air pollutants which are inhaled.

Heavy metals are an important constituent of fossils and combustion of coal releases in the atmosphere a number of heavy metals. These either come out as slag from boilers or are impregnated on the soot particles and with the slightest of acidic conditions may resolubilise in the environment causing metal pollution of air and water. This class of pollutants, because of bioaccumulative properties needs special mention. Bioaccumulation leads to magnification and long term exposure to very small concentrations may cause severe problems. Episodal pollution of this kind is best exemplified by the Minamata Bay incident where Methyl Mercury created problems of fish and human mortality.

In a 200 MW power plant in India burning about 9000 tons of coal per day leaching of a mere 15% of heavy metals from the surface of Ash will cause a nearby river to receive daily 208 Kg of Iron, 56 Kg of Zinc, 45 Kg of Copper, 5 Kg.of Cadmium, 56 Kg of Nickel, 4.6 Kg. of Uranium, 16.5 Kg of Thorium, 60.6 Kg of Chromium and 11.2 Kg of Cobalt daily. The transformation, which these metals undergo in the polluted anaerobic waters, the effects of bioaccumulation on the flora and fauna and the impact of biomagnification need special attention. Chlorine and Fluorine are also constituents of coal and it is expected that photochemical reactions would trigger out a process of synthesis of Chlorofluorocarbons which may have far reaching consequences.

We all know by now that Chlorofluorocarbons are causative in the catalytic breakdown of Ozone and the consequent depletion of the ozone layer. The life of these molecules (Chlorine) is almost 100 years and it is for this extent of time that it would go on damaging the ozone layer. We must be cautious. Most of the gases released from fossil fuel burning contribute to the green house effect. Global warming is a consequence. It is also significant that every three tones of carbon burnt consume 8 tons of oxygen and that we are drawing excessively on the oxygen resource of earth. Fly Ash disposal is a major concern for the thermal power plants. Generally, for every MW of installed capacity approximately one acre of land is required for the ash generated, the material accumulating to a height of 8 – 10 metres.

Fly ash is a harmful environmental pollutant. Being light it gets air-borne very fast. Long inhalation causes silicosis, fibrosis of lungs, bronchitis and pneumonites etc. It corrodes structural surfaces and deposition effects horticulture. Slurry disposal lagoons/ settling tanks become sources of mosquitoes and bacteria. It holds the potential to contaminate the underground resources with traces of toxic metals present in it. The ash handling system may account for 5% of the total cost of a power project.