• The Ministry of Railways and NTPC convened a national conference on fly ash utilisation and transportation in Noida on August 25. 

• The event brought together fly ash generators, users, transporters, and policymakers to discuss and formulate strategies for sustainable fly ash management in India.

• The conference held added significance in the context of government policies mandating and promoting the use of fly ash in cement manufacturing, road construction, mine backfilling, brick production, and other building materials. 

• These initiatives reflect India’s commitment to the principles of a circular economy, cost efficiency, and environmental sustainability.

What is fly ash?

• In India, coal is a major source of fuel for power generation. In the process of electricity generation, large quantities of fly ash get produced and become available as a byproduct. 

• It is a fine powder resulting from the combustion of powdered coal — transported by the flue gases of the boiler and collected in the Electrostatic Precipitators (ESP).

• Fly ash produced in modern power stations of India is of good quality as it contains low sulphur and very low unburnt carbon. 

• In order to make fly ash available for various applications, most of the new thermal power stations have set up dry fly ash evacuation and storage systems.

• Fly ash consists primarily of oxides of silicon, aluminum iron and calcium. Magnesium, potassium, sodium, titanium and sulfur are also present to a lesser degree. 

• When used as a mineral admixture in concrete, fly ash is classified as either Class C or Class F ash based on its chemical composition. 

• Class C ashes are generally derived from sub-bituminous coals and consist primarily of calcium alumino-sulfate glass, as well as quartz, tricalcium aluminate, and free lime (CaO). Class C ash is also referred to as high calcium fly ash because it typically contains more than 20 per cent CaO.

• Class F ashes are typically derived from bituminous and anthracite coals and consist primarily of an alumino-silicate glass, with quartz, mullite, and magnetite also present. Class F, or low calcium fly ash has less than 10 per cent CaO.

• The unique spherical shape and particle size distribution of fly ash make it a good mineral filler in hot mix asphalt (HMA) applications and improves the fluidity of flowable fill and grout. 

• The consistency and abundance of fly ash in many areas present unique opportunities for use in structural fills and other highway applications.

• Fly ash presents both a challenge and an opportunity. While it requires safe and sustainable handling, it also offers significant potential as a valuable resource for the infrastructure and industrial sectors.

• In 2024–25, India generated 340.11 million tonnes of fly ash, of which 332.63 million tonnes were successfully utilised.

• During the year 2024-25, about 32 per cent of the total fly ash generated was used in the construction of roads and flyovers, followed by 27 per cent utilised within the cement industry, and 14 per cent in the manufacturing of bricks and tiles. 

• Backfilling and mine filling accounted for approximately 11 per cent and 10 per cent, respectively. 

• The agricultural sector and ready-mix concrete (RMC) recorded the usage, ranging between 1 per cent and 2 per cent.