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Fly ash

Topics Covered:

Conservation, environmental pollution and degradation, environmental impact assessment.


Fly ash


What to study?

For prelims: What is fly ash, how is it produced and where it can be used?

For mains: Concerns associated with its contamination, what needs to be done and legislative measures necessary.


Context: IIT Hyderabad scientists convert fly ash into waterproofing material.

Treating fly ash with stearic acid, used in soaps and shampoos, modified the nature of fly ash and helped develop materials with contrasting adhesion behaviours — high adhesions like a rose petal and low adhesion like a lotus leaf.


What is Fly Ash?

Fly ash is a major source of PM 2.5 (fine, respirable pollution particles) in summer. It becomes air borne, and gets transported to a radius of 10 to 20 kms.

It can settle on water and other surfaces.



Fly ash contains heavy metals from coal, a large amount of PM 2.5 and black carbon (BC).


Health and environmental hazards:

Toxic heavy metals present: All the heavy metals found in fly ash nickel, cadmium, arsenic, chromium, lead, etc—are toxic in nature. They are minute, poisonous particles accumulate in the respiratory tract, and cause gradual poisoning .

Radiation: For an equal amount of electricity generated, fly ash contains a hundred times more radiation than nuclear waste secured via dry cask or water storage.

Water pollution: The breaching of ash dykes and consequent ash spills occur frequently in India, polluting a large number of water bodies.

Effects on environment: The destruction of mangroves, drastic reduction in crop yields, and the pollution of groundwater in the Rann of Kutch from the ash sludge of adjoining Coal power plants has been well documented.


The issues which impede its full-scale utilization in India:

  1. Indian fly ash is primarily of the calcareous or class C variety, implying that it possesses not only pozzolanic, but also hydraulic (self-cementing) properties. In contrast, European fly ash is of a silicious or class F variety, implying an absence of hydraulic properties.
  2. BIS revised the maximum and minimum blending standards. While the BIS is in line with the American standards on blended cement, the European and South African standards allow the blending of fly ash up to 55%.
  3. The pricing of fly ash is increasingly becoming a contentious issue that is hampering its gainful utilisation.
  4. Imperfections typical of quasi-markets, such as information asymmetry and high transaction costs, vested interests, technical and technological limitations, and the lack of regulatory oversight and political will, have impeded the flow of fly ash to its most value-adding use. 


How can it be utilised?

  1. Fly ash is a proven resource material for many applications of construction industries and currently is being utilized in manufacturing of Portland Cement, bricks/blocks/tiles manufacturing, road embankment construction and low-lying area development, etc.
  2. There is need for education and awareness generation.
  3. Road contractors and construction engineers need to know the benefits of using fly ash in construction.
  4. Measures need to be taken to reduce the cost of construction of roads using fly ash by way of tax structure, subsidies and transportation services.
  5. There is also a need to prevent the ash from coming to the power plant by washing the coal at its place of origin.
  6. The government should also come out with a policy to encourage fly ash use in cement plant.


Need of the hour:

  1. Conduct more research on improving the quality of fly ash, grading fly ash generated by different technologies and types of coal, and feasible blending ratios for the cement industry.
  2. The BIS must update the blending standards, which have not been revised since 2000.
  3. Improve transparency and reduce the costs of fly ash disposal by Coal power plants.
  4. Limit fly ash production through greater deployment of renewable energy sources, using better coal and combustion techniques, etc, since cement-related industries alone will not be able to absorb all the fly ash generated in the future
  5. The key requirements for overcoming the barriers are greater regulatory oversight and price control, revision of cement blending standards, research in improving fly ash quality, reducing cost of transportation, provisions for overcoming information asymmetries, and overall sensitisation of key decision-makers on the matter.


Sources: the Hindu.