Recently a committee of experts, chaired by Principal Scientific Advisor (PSA) Ajay Sood, has recommended that India do away with a decade-long policy of mandating Flue Gas Desulphurisation (FGD) units in all coal-fired thermal power plants (TPPs).

Rationale Behind Rolling Back of Mandate

• Low Sulphur Coal Usage: 92% of Indian coal has low sulphur (0.3%–0.5%), making universal FGD installation unnecessary, as per NIAS and IIT-Delhi data.
• Environmental Trade-offs: FGDs would raise power and freshwater use, adding 69 million tonnes CO₂ (2025–30) while only cutting 17 million tonnes SO₂, worsening climate impact.
• Cost-effective Alternatives Exist: Electrostatic precipitators by BHEL cost ₹25 lakh/MW (vs ₹1.2 crore/MW for FGD) and reduce particulate matter by 99%, offering better pollution control.

What is Flue Gas Desulphurisation (FGD)?

• FGD : It  is a scrubbing method that utilizes an alkaline reagent, typically sodium- or calcium-based, to remove sulfur dioxide (SO₂) from the flue gas emissions of  coal-fired power plants.
• Effectiveness: FGD can remove up to 95% of sulfur dioxide from flue gas, significantly reducing SO₂ emissions.
• Flue Gas Composition: Also known as exhaust or stack gas, flue gas originates from combustion plants and contains a mix of pollutants, including particulate matter (dust), sulfur oxides, nitrogen oxides, and carbon monoxide.
• It may contain pollutants such as particulates, sulfur dioxide, mercury, and carbon dioxide, but most flue gas consists of nitrogen oxides.
• Untreated flue gas from power plants, industrial facilities, and other sources can significantly impact local and regional air quality.
• Process Overview: In the scrubber or absorber tower, uncleaned flue gas is sprayed with a mixture of water and limestone (scrubbing slurry), which reacts with sulfur dioxide and binds it, preventing its release into the atmosphere.

Impact of Sulphur Dioxide in the Environment

• Major Air Pollutant: Sulphur dioxide is a severe environmental pollutant, harmful to human, animal, and plant health.
• Acid Rain Precursor: SO₂ contributes to acid rain, which harms forests, freshwaters, and soils.
  • Acid rain disrupts ecosystems by killing insects and aquatic life forms, damaging vegetation, and reducing biodiversity.
  • It causes damage to infrastructure and materials causing paint to peel and corrodes steel structures such as bridges.
  • Accelerates the weathering of stone buildings and statues, eroding cultural and historic landmarks

Electrostatic Precipitators vs FGD

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