About

• Sulphur dioxide (SO2) is a gaseous air pollutant composed of sulfur and oxygen.
• SO2 is a colourless, soluble gas with a characteristic pungent smell which forms sulphuric acid when combined with water.
• Sources of SO2 emissions: 
  • Anthropogenic sources: Burning of coal in power plants, oil refineries, motor vehicles, domestic boilers, etc.
  • Natural sources: Volcanic eruptions, forest fires, etc.

• SO2 emissions can cause respiratory, cardiovascular and lung diseases, and can induce acid rain, which is a threat to crops, forests, and aquatic species.
• SO2 is also a precursor to the formation of the hazardous fine particulate matter (PM2.5), which has been linked to many health issues.
• Reports suggest that India was the largest emitter of SO2 globally in 2022, accounting for over 20% of the world’s anthropogenic emissions.

Why in News?

• As many polluting thermal power plants have missed the third deadline to comply with SO2 emission standards notified in 2015, the Ministry of Environment, Forest, and Climate Change (MoEFCC) has granted another extension, extending the timeline by three years to install pollution control equipment.
• All these power plants were expected to install Flue Gas Desulphurisation (FGD) equipment to meet the SO2 standards by the previous deadline but many of them failed to do it. 

About Flue Gas Desulphurisation

• Flue gas is the emitted material produced when fossil fuels such as coal, oil, natural gas, or wood are burned for heat or power.
• Flue gas desulfurization is the process of removing sulphur compounds from the exhaust emissions of fossil-fueled power stations. 
• Methods of FGD include
  • Wet Scrubbing – In this process a slurry of limestone or lime is used to absorb SO2 in a wet scrubber. This method is often used in power plants that burn high-sulfur fuels.
  • Dry scrubbing – It is also known as spray dry absorption, and uses a concentrated slurry of powdered limestone to remove SO2.