Introduction:
- FGDs are pollution control devices used in coal-fired thermal power plants (TPPs) to remove sulphur dioxide (SO₂) from flue gas.
- SO₂ is produced during the combustion of sulphur-rich fossil fuels like coal.
- FGD units neutralise acidic SO₂ using basic compounds like limestone.
Relevance : GS 3(Environment and Ecology)
Common Types of FGD Technologies
- Dry Sorbent Injection:
- Uses powdered limestone or other sorbents.
- Reacts with SO₂ in flue gas and is filtered out using fabric filters or electrostatic precipitators.
- Wet Limestone Scrubbing (most common):
- Uses limestone slurry to absorb SO₂, forming gypsum as a byproduct.
- High efficiency; gypsum has commercial uses.
- Seawater FGD:
- Used in coastal plants.
- SO₂ is absorbed by seawater, which is then treated before being discharged.
Why are SO₂ Emissions Harmful?
- Greenhouse gas contributing to global warming.
- Causes respiratory illnesses and worsens air quality.
- Converts into secondary PM2.5, a major pollutant.
- ~15% of India’s ambient PM2.5 is from coal combustion.
- Of that, 80% is from SO₂-derived secondary particles.
Status of FGD Compliance in India
- 2015: Government mandated FGDs in all 537 coal-fired TPPs.
- Deadlines were repeatedly postponed (2018 → 2027–29).
- As of April 2025, only 39 out of 537 plants had installed FGDs.
- December 2024: Deadline further extended by three years.
- April 2025: Committee led by PSA Ajay Sood recommended rollback of the FGD mandate.
Why is FGD Implementation Contentious?
- High capital cost: ₹1.2 crore/MW → ₹97,000 crore for planned 97,000 MW addition.
- Potential tariff hike of ₹0.72 per kWh (mostly fixed costs).
- Government concerns: balancing health, affordability, and energy expansion.
Expert Opinions on FGD Rollback
- Critics warn that skipping FGD:
- Compromises clean air goals.
- Undermines public health.
- FGDs are essential for reducing SO₂ and indirectly PM2.5.
- Tariff impact is manageable and largely predictable.
Is There Any Alternative to FGDs?
- No effective alternative exists for SO₂ removal from flue gases.
- Dr. Ganesan: FGDs are urgent and unavoidable for compliance.
Conclusion
- FGDs are technically essential but financially challenging.
- India must weigh short-term costs against long-term health and environmental gains.
- Delay in FGD installation risks worsening air pollution, especially from coal-based power generation.
