18th April 2025 (12 Topics)

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Flue Gas Desulphurisation (FGD)

Context

A new study by the National Institute of Advanced Studies (NIAS), Bengaluru recommends a rollback of the Environment Ministry’s 2015 mandate requiring all 537 coal-fired power plants in India to install Flue Gas Desulphurisation (FGD) systems.

What is FGD?

Flue Gas Desulphurisation (FGD) is a pollution control technology that removes sulphur dioxide (SO?) from the exhaust flue gases of fossil-fuel power plants.
It was mandated in 2015 to tackle India’s rising SO? emissions. The deadline for installation was 2018, but due to slow compliance, it has been extended to 2027–2029, depending on plant category.
SO? contributes to acid rain, respiratory illnesses, and air pollution. FGDs were intended to curb these health and environmental risks.

What Does the NIAS Study Argue?

FGD Not Needed at All Plants: 92% of Indian coal is low-sulphur (0.3%–0.5%). Thus, FGD should only be mandated for plants using imported/high-sulphur coal.
Low Risk of Acid Rain in India: Acid rain is not a significant issue in India. Stack heights (minimum 220 m) and climatic conditions disperse SO? adequately.
Environmental Trade-Off: Installing FGDs would:
- Increase CO? emissions by 69 million tonnes (2025–2030) due to higher energy and water use.
- Reduce SO? by 17 million tonnes — but this trade-off may worsen global warming.
Focus on Particulate Matter (PM) Instead: PM pollution from coal plants is more harmful due to high ash content in Indian coal.

Fact Box: Sulphur dioxide (SO2)

Sulphur dioxide (SO2) is a heavy, colourless, and poisonous gas with a pungent and irritating odour. Its smell is often described similar to that of a burnt matchstick.
The gas forms secondary particulate matter (PM2.5) when it oxidizes to sulphuric acid (H2SO4) by combining with water vapour.
It also reacts with ammonia (NH3) to create another dangerous compound called ammonium sulphate ((NH4)2SO4).
SO2 also contributes to sulphurous smog, which results from a high concentration of sulfur oxides (SOx) in the atmosphere and is exacerbated by dampness and particulate matter (PM).
Health impact of sulphur dioxide: Lung function, worsen respiratory diseases, Wheezing, shortness of breath, chest tightness, Aggravation of asthma and chronic bronchitis, Inflammation of the respiratory tract (coughing, mucus secretion), Eye irritation
Environmental impact: Acid rain, Damaging of vegetation, Depriving soil of essential nutrients (calcium, aluminum, magnesium)

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Flue Gas Desulphurisation (FGD)

What is FGD?

What Does the NIAS Study Argue?

Fact Box: Sulphur dioxide (SO2)