Fly Ash | 05 Jul 2021

Why in News

National Thermal Power Corporation (NTPC) Limited has invited Expression of Interest (EOI) for sale of fly ash, in its endeavour to achieve 100% utilization of fly ash, from the designated plants of the Middle East and other regions.

  • Fly Ash is a byproduct from burning of coal in the thermal power generation.

Key Points

  • Fly Ash:
    • About:
      • It is called fly ash because it is transported from the combustion chamber by exhaust gases.
      • It is collected from the exhaust gases by electrostatic precipitators or bag filters.
        • An electrostatic precipitator (ESP) is defined as a filtration device that is used to remove fine particles like smoke and fine dust from the flowing gas.
        • It is the commonly used device for air pollution control.
    • Composition:
      • Fly ash includes substantial amounts of silicon dioxide (SiO2), aluminium oxide (Al2O3), ferric oxide (Fe2O3) and calcium oxide (CaO).
    • Properties:
      • Resemble Portland cement but is chemically different.
        • Portland cement is a binding material in the form of a finely ground powder that is manufactured by burning and grinding a mixture of limestone and clay.
        • Its chemical composition includes calcium silicates, calcium aluminate and calcium aluminoferrite.
      • Exhibit cementitious properties.
        • A cementitious material is one that hardens when mixed with water.
    • Uses:
      • It is used in concrete and cement products, road base, metal recovery, and mineral filler among others.
    • Harmful Effects:
      • Fly ash particles are toxic air pollutants. They can trigger heart disease, cancer, respiratory diseases and stroke.
      • When combined with water they cause leaching of heavy metals in ground water.
      • It also pollutes the soil, and affects the root development system of trees.
  • Fly Ash Utilisation:
    • NTPC has collaborated with Cement manufacturers around the country to supply Fly Ash.
    • To promote the use of Fly Ash bricks in building construction, NTPC has set up Fly Ash brick manufacturing Plants at its Coal based Thermal Power Plants.
      • These bricks are being utilized in Plants as well as township construction activities exclusively.
      • On average, 60 million Fly Ash bricks are being manufactured annually by NTPCs own Fly Ash brick Plants.
    • As per the MoEF&CC directives, NTPC stations must keep at least 20% of total Fly Ash produced in reserve for the issue to Fly Ash brick/blocks/tiles manufacturers and issuing Fly Ash free of cost to them.
      • About 9% of the total Fly Ash produced in NTPCs stations, is being utilized by Fly Ash bricks/blocks and tiles manufacturing units annually.
    • During the year 2020-21, almost 15 NTPC stations supplied Fly Ash to various Road projects and Ash utilization crossed by nearly 20 million tonnes.
    • Over the last five years the fly ash utilisation has grown up by 80% in the country.
    • Pradhan Mantri Awas Yojana (Urban) has focused on new construction technologies such as using fly ash bricks that are innovative, and environmentally friendly.
    • Even state governments have come out with their Fly ash utilization policies, e.g. Maharashtra was the first state to adopt the policy.
    • A web portal for monitoring of fly ash generation and utilization and a mobile based application titled “ASHTRACK” has been launched by the Government.
    • GST rates on fly ash and its products have been reduced to 5%.


  • NTPC Ltd. is a central Public Sector Undertaking (PSU) under the Ministry of Power.
  • Aim: To provide reliable power and related solutions in an economical, efficient and environment-friendly manner, driven by innovation and agility.
  • It became a Maharatna company in May 2010.
  • India’s largest power generating company.