Sulphur Dioxide (SO₂) Emissions in India

GS3 – Environment

Context:

The government has recently eased the 2015 requirement mandating coal plants to install Flue Gas Desulphurisation (FGD) units, citing high installation costs, despite SO₂’s substantial role in air pollution.

India’s SO₂ Emission Status:
  • Global Ranking: India was the largest SO₂ emitter in 2022, contributing over 20% of global anthropogenic emissions (CERA).
  • Primary Sources: Emissions mainly stem from coal-based thermal power plants, heavy industries, and a few natural sources.
  • Regulatory Standards (Air Act, 1981):
    • 24-hour limit: 80 µg/m³ (all areas)
    • Annual average:
      • Urban areas: 50 µg/m³
      • Sensitive zones: 20 µg/m³
  • Implementation Lag: Out of 537 coal plants, only 39 have installed FGD units, indicating slow progress in emission control.
Impacts of SO₂ Pollution:
  • Health Risks:
    • Acute exposure: Triggers asthma, coughing, and respiratory distress
    • Chronic exposure: Leads to lung diseases and early mortality
  • Environmental Harm:
    • Causes acid rain, damaging crops, soil, and aquatic ecosystems
    • Forms sulphate aerosols, reducing visibility and harming biodiversity
Control Measures:
  • Pre-Combustion Techniques:
    • Fuel switching, coal washing, and Fluidised Bed Combustion (FBC) reduce SO₂ at the source
  • Post-Combustion Techniques:
    • Dry and wet FGD systems use limestone to extract SO₂, generating gypsum as a by-product
  • Innovative Methods:
    • Biotech and regenerative systems convert or recover sulphur into eco-friendly forms like elemental sulphur
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