Fly Ash Utilisation In India
By Dr. Yashpal Singh, Chairman, The Wealthy Waste School India
Also see MoEF & CC Publishes Draft Notification on 100% Utilization of Ash by Thermal Power Plants. Fixes Responsibilities and Proposes Fines and Fines and Penalties. Comments on draft notification no. G.S.R. 285(E) dated 22/04/2021
Coal India reports that the ash content of Indian Coal ranges from 25 to 45% as against the 10 to 20% in imported coal. The higher ash content is attributed to the drift theory of formation of coal deposits in India. Excessive land requirement, air borne pollution and the possibility of hazardous substances leaching to ground water are big problems associated with Fly ash disposal.
Thermal Power, Coal and Fly Ash
As per the National Power Portal, India has a total installed power generation capacity of 371976.84 M.W. as on 31-07-2020 of which 205954.50 mw is attributed to coal based power generation (http:npp.gov.in 10/8/20 12.21.46)
In 2019, the global proven reserves for anthracite and bituminous coal amounted to around 749 billion metric tons. Sub bituminous and lignite coal amounted to almost 320.5 billion metric tonnes in 2019. (www.statista.com> chemicals and resources > Fossil fuels.)
The Federal Institute for Geo science and National Resources (BGRI) Energy Study 2019 reports 734.93 Billion Tons as the Globalreserve for Anthracite and bituminous coal and 319.879 Billion tons for sub bituminous and Lignite coal at the end of 2018. Indian reserves at 9.6% of the total reserves,are reported as 96.468 for Anthracite and bituminous coal and 4.895 billion tons for sub bituminous and Lignite coal respectively with a R/P ratio (number of years that the reserves would last) of 132 Years of current use both in the National and Global Contexts.(BP Statistical Review of World Energy, 2019.68th Edition.)
The 69th edition of the BP Statistical Review of World Energy, 2020 reports 749.167 Billion Tons as the Global reserve for Anthracite and bituminous coal and 320.469 Billion tons for sub bituminous and Lignite coal at the end of 2019. Indian reserves at 9.9% of the total reserves, are reported as 100.858 for Anthracite and bituminous coal and 5.073 billion tons for sub bituminous and Lignite coal respectively with a R/P ratio (number of years that the reserves would last) of 140 Years of current use in the National context as compared to a R/P ratio of 132 in the Global Context. As per this report, the Global coal production to the end of 2019 has been 167.58 Exajoules (5717.9 Million Tons Coal Equivalent) of which 12.73 Exajoules, with an annual growth rate of 3% (2008-2018) has been from India. This translates to 434.35 Million Tons Equivalent of Coal, which is 7.6% of the global production. China with 79.82 Exajoules is the biggest producer with about 47.6% of the global share. In terms of yearly consumption, India had consumed 18.62 Exajoules(635.33 Million tons Coal Equivalent) at the end of 2019. This was 11.8% of the total Global consumption and demonstrated a 5.5% annual growth rate over the period 2008-2018. China consumed 81.67 Exajoules’ at an annual growth rate of 1.7%. This was 51.7% of the total global consumption. Indias coal imports have grown at an annual growth rate of 14.1% over the years 2008-2018 and at 5.69 Exajoules (194.14 Million Tons Coal Equivalent , are about 16.1% of the total coal being Globally traded for imports.
As per data available at coal.nic.in/content/production-and-supplies the All India production of coal during 2019-20 was 729.10 MT (Provisional) with a positive growth of 0.05%. The total import of coking coal was 51.88 million metric tons and that of non -coking coal 196.72 million metric tons in the F.Y. 2019-20 up to March 2020. The total coal import was 248.55 million metric tons in this period. The Coal production in India based on data from 1-04-2017 to 31-03-2018 was 726 Million Tons which demonstrates an increment of 48% since 2007. This included 635.6 million tons of thermal coal, 47.5 million tons of Lignite and 40.9 million tons of coking coal. Coal imports have been reported as 209 million tons (125 million tons hard coal and 84 million tons of brown coal) which is up by 320% since 2007. The share of coal is 44% of the TPES (Total Primary energy supply) and 74% of electricity generation. Of the 935 mt of total coal used in the country, 73.7% was used for Power and heat generation, 17.6% in Industry, 5.8% in other energy industries like coke ovens and blast furnaces and 3.3% in residential and service sectors.( coal.nic.in/content/production-and-supplies)
In terms of Million Tons Oil Equivalent (Mtoe), India produced 308 Mtoe in 2018 at an average growth rate of 3.1% between the decade spanning 2007-2017, growing to 7.5% in 2018. India’s share in 2018 stood at 7.9% of the total global production of 3916.8 Mtoe in 2018. Global average growth rate for 2007-2017 was 1.3% and 4.3% in 2018.
The Problems of Fly ash disposal
Coal India reports that the ash content of Indian Coal ranges from 25 to 45% as against the 10 to 20% in imported coal. The higher ash content is attributed to the drift theory of formation of coal deposits in India. Excessive land requirement, air borne pollution and the possibility of hazardous substances leaching to ground water are a few problems associated with Fly ash disposal.
Land requirements for ash ponds are considerable. It has been stated vide MoEF& CC notification dated 3-11-2019 that 50 hectares or about 125 acres may be required for a 500 MW unit based on 45% ash content in coal or in the same proportion for units in other capacity. (0.25 acres per M.W). The land requirements for fly-ash generated from imported coal with a 10% ash content has been suggested as 0.056 acres per MW. It has been estimated that at an average ash content of 33% in coal, the annual fly ash generation in India would be approximately 437 million tons. With the current trends of Fly ash utilization continuing, the overall utilization could be 310 MT by 2030. While fly ash requirement in the Cement Industry will grow fourfold to 151 million tons in 2030, approximately 128 million tons of fly ash will still remain unutilized. This will require an additional 2300 hectares of land and 1.3 billion cubic meters of water for the Ash ponds. (Fly ash 2020. Mission energy.org). In India an area of 65000 acres of land is being occupied by ash ponds and its generation is expected to cross 225 million tons by 2020(4).
The unutilized fraction which is growing considerably presents grave environmental consequences. A lot still needs to be done.
The utilization of fly ash
Many demonstration projects to facilitate use of fly -ash 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. Studies show that one ton of Portland cement production discharges 0.87 tons 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 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 pozzolanic 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 greenhouse 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.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.
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.
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 used 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.
Fly Ash generation and utilization in India
As per a Central Electricity Authority (CEA) report, the utilization of fly ash has increased from 66.6 million tons in 2008-09 to 132 million ton in 2017-18. In the year 2017-18 the overall utilization of fly ash was 67%. This utilization was 25.6% in the cement sector, 10.48% in reclamation of low-lying areas, 9.01% in bricks and tiles, 6.9% in ash dyke raising, 6.7% in mines back filling, 3.4% in roads and flyovers, 0.66% in concrete, 0.29% in agriculture.
The utilization of Fly ash in India has increased from 6.64 million tons in 1996-97 to 168.46 million tons in 2018-19 (8).
The Fly ash generation during the financial year 2018-19 (8) has been 217.04 million tons due to the combustion of 667.43 million ton coal/lignite and the fly ash utilization has been 168.40 million tons suggesting an effective usage of 77.59%. The installed capacity for thermal power generation was 197966.50MW.
Fly ash utilization during 2018-19 has been
- Cement -26.88%
- Mine Filling -4.65%
- Bricks and tiles -9.96%
- Reclamation of low-lying areas -13.51%
- Ash Dyke raising -9.94%
- Roads and Flyovers-4.48%
- Agriculture -0.63%
- Concrete -0.82%
- Hydro Power Sector –Nil
- Others -6.72%
- Unutilized -22.41%
- Total -100%
The fly ash utilization which was merely 9.63% in 1996.97 has risen to 77.59% in 2018.19.
The Central Electricity Authority (CEA) also reports that in the six months of the first half year of 2019-20 (April 2019 to September 2019) the generation of fly ash was 129.0929 million tons and the utilization 100.9427 million tones with a percentage utilization of 78.19% (better than the 67% in 2017-18). 10.1767 million tons were utilized in making bricks and tiles, 36.20 million tons in the manufacture of port land Pozzolana Cement, 10.4229 million tones in construction of high ways and roads, 0.6502 for part replacement of cement in concrete, 11.1752 million Tons in Ash Dyke raising, 18.6902 million tons in reclamation of low lying areas, 5.9697 million tones in mine filling, 0.4151 million tons in agriculture and waste land development and 7.2350 in other uses. Ref. Central Electricity Authority 2020, Report on Fly Ash Generation at Coal/Lignite based thermal power stations and its utilization in the country for first half of the year 2019-2020 (April 2019 to September 2019). Dated April 2020.
The Fly ash notifications of 2009 as amended through 2016
The Ministry of Environment, Forests and Climate Change (MoEF& CC) issued the first Fly Ash notification in 1999 which has been subsequently amended in 2003, 2009 and 2016. The notification mandates that:
- Fly ash shall be used for the purpose of manufacturing ash-based products such as cement, concrete blocks, bricks, panels or any other material or for construction of roads, embankments, dams or for any other construction activity by every construction agency within a radius of 300 Kms from Thermal Power plants.
- Fly ash shall be used in the external overburden, mines back filling or stowing of mines within a distance of 50 kms. of Thermal Power Plants
- All construction agencies/Government departments undertaking road projects, Fly- over/bridges as well as local authorities will make provisions for use of fly ash in their tender documents and schedule of materials and rates.
- Fly-ash utilization shall be achieved in a time bound manner in a phased manner for all Coal/Lignite based TPP’s in the country so as to achieve 100% utilization of fly ash.
- The amendment of 2016 provides that the cost of transportation of ash upto 100 kms shall be borne by the thermal power plant TPP and for distances between 100 kms to 300 kms will be shared between user and TPP’s. However, it shall be mandatory for coal-based power plants to bear the entire cost of transportation of fly ash up to a radius of 300 Kms in asset creation programs of the Government involving construction of roads, buildings and dams etc.
- A draft amendment of 2019 has also mandated that no new red clay brick kiln shall be installed within a radius of 300 Kms from a power plant and existing red day brick kilns within a radius of 300 KM of power plant shall be converted to Fly ash bricks/blocks/tile manufacturing units.
- To encourage conversion, thermal power plant should provide fly ash at nominal rate of Rs. 1 per ton and bear full transportation cost up to 300 Km to such units. At least 20% fly ash shall be made available to units manufacturing fly ash bricks, blocks and tiles on priority basis over other users at Rs. 1 per ton.TPP’s with 100% utilization are exempted from this provision.
- The 2009 notification, also provides that “No agency, person or organization shall within a radius of three hundred kilometers of a coal/lignite based thermal power plant undertake or approve or allow reclamation and compaction of low-lying areas with soil.Only fly ash shall be used for compaction and reclamation and it shall be ensured that such reclamation and compaction is done in accordance with the specifications and guidelines laid down by the authorities. (The increase from 100 to 300 kms has been done in further amendments)
- The provisions of the MoEF and CC Gazette notification dated 3-11-2009 stipulate that at least 25% ash can be mixed with over burden material for filling in the coal mines and other mines of minerals and metals.
- The 2009 notification provides that TPP’s established before the notification (i.e. 3rd November 2009) will achieve 50% within one year, 60% within 02 year, 75% within 03 years, 90% within 04 years and 100% within 5 years. New thermal Power plants shall achieve 50% in one year, 70% in 2 years, 90% in three years and 100% in 04 years.
- Emergency ash pond or Fly ash storage area up to 50 HA for 500 mw may be provided. TPP’s shall not store at any given time more than 03 months of ash generation in their ash ponds. In case it exceeds 03 months of generation the same will be disposed off (through emergency storage?) within a maximum period of 05 years.
- Minimum Fly Ash content for building materials or products to qualify as fly ash- based products ranges from 15-50%. I.S.(Indian Standards) specification have been provided.
- The Ministry of Agriculture may consider the promotion of ash utilization in agriculture as soil conditioner.
- To maximize utilization of Fly ash in Roads/Flyover embankment construction the MoEF through its gazette notification dated 25-01-2016 has made it mandatory for the use of ash in road embankment/flyover embankment construction within 300 Kms radius of coal/lignite based thermal Power. The costs of transportation within 100 Kms are to be borne by the Thermal power plants and between 100 to 300 Kms to be shared equally between the thermal power plant and the user. For Government, asset creating projects, the entire cost for 300 KMS has to be borne by the TPS.
Additional condition being imposed by the MoEF and CC for Thermal power plants 28th August 2019 (O.M.F.No. 22-13/2019-IA III)
- Guidelines prepared by CPCB for disposal of fly ash for reclamation of low-lying areas and in stowing/back filling of abandoned mines/queries shall be followed during disposed of ash in abandoned or working mines.
- There should at least be a clearance of 500 meters from river and water body in case of ash disposal in abandoned mines to prevent embankment failures and fly ash flow into the water body.
- Top layer of the disposal area in the abandoned mines shall be kept moist during disposal.
- Top layer of disposal layer should have at least 70 cm overburden of gravels/stones and then 30 cm sweet soil cover. Subsequently the vegetation shall be raised on the cover.
- Bio accumulation and bio magnification tests shall be conducted on surrounding flora and fauna during pre-monsoon and post monsoon to monitor trace metals uptake through ground water/run off.
- Surface run off shall not be let out in the surrounding. It should be suitably collected, treated and reused back for mixing ash and in plant operation.
- To the extent possible, only decanted water from mine, make up water from treated effluents such as cooling tower blow down and treated sewage water shall be used for making slurry.
- Fly ash to be used as a soil conditioner, in quantitative certified by the state Agricultural Universities/Colleges based on soil testing.
- Approval from the DGMS shall be obtained before disposing the ash in the mine wide.
- Technology for conversion of fly ash into coarse granules for stowing in the under -ground mines be explored.
- All power plants should install different silos for dry collection of fly ash.
- Monthly records on fly ash disposed and water consumption along with nature/source of water shall be maintained and submitted to the Ministry/Regional Officer annually.
- Before starting disposal of ash into voids, the permission of the mine owner has to be obtained and submitted to the Ministry and its Regional officers.
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