In Focus: Sulphur Dioxide (SO2) as a Pollutant

 In Focus: Sulphur Dioxide (SO2) as a Pollutant

• Description
  • SO2 is a colorless and toxic gas which is part of a larger group of chemicals referred to as sulphur oxides (SOx). 
    
    
  
  
  
• Sources
  • It is produced by burning of fossil fuels, like coal, oil and diesel.
    
    
  • Industrial processes like cement production and petroleum refinement also lead to its production.
    
    
  • Sources include coal based power plants, metals processing and smelting facilities, and vehicles.
    
    
  • Sulphur dioxide is also a natural by-product of volcanic activity.
    
    
  
  
  
• Secondary Pollutants
  • Sulphur dioxide can create secondary pollutants once released into the air.
    
    
  • Secondary pollutants formed with sulphur dioxide include sulphate aerosols, particulate matter, and acid rain.
    
    
  
  
  
• Effects
  • SO2 is a poisonous air pollutant that increases the risk of stroke, heart disease, lung cancer, and premature death.
    
    
  • Sulphur dioxide and secondary pollutants can contribute to respiratory illness by making breathing more difficult, especially for children, the elderly, and those with pre-existing conditions.
    
    
  • Longer exposures can aggravate existing heart and lung conditions, as well.
    
    
  • Sulphur dioxide and other SOx are partly culpable in the formation of thick haze and smog, which can impair visibility in addition to impacting health.
    
    
  • Beyond human health impacts, sulphur dioxide’s contribution to acid rain can cause direct harm to trees and plants by damaging exposed tissues and, subsequently, decreasing plant
    
    
  • Other sensitive ecosystems and waterways are also impacted by acid rain.
    
    
  • Acid rain causes corrosion of metals, damage buildings and monuments.
    
    
  
  
  

Principal Approaches to Control Sulphur Oxide (SOX) Emissions

• Use of low-sulphur fuel
  • Since sulphur emissions are proportional to the sulphur content of the fuel, an effective means of reducing SOx emissions is to burn low-sulphur fuel such as natural gas, low-sulphur oil, or low-sulphur coal.
    
    
  
  
  
• Reduction or removal of sulphur in the feed
  • The most significant option for reducing the sulphur content of fuel is called beneficiation.
    
    
  • Up to 70% of the sulphur in high-sulphur coal is in pyritic or mineral sulfate form, not chemically bonded to the coal.
    
    
  • Coal beneficiation can remove 50% of pyritic sulphur and 20–30% of total sulphur.
    
    
  • Sulphur in oil can be removed through chemical desulphurization processes, but this is not a widely used commercial technology outside the petroleum industry.
    
    
  
  
  
• Use of appropriate combustion technologies
  • Processes using fluidized-bed combustion (FBC) reduce air emissions of sulphur oxides.
    
    
  • A lime or dolomite bed in the combustion chamber absorbs the sulphur oxides that are generated.
    
    
  
  
  
• Emissions control technologies such as flue gas desulphurization (FGD)
  • It is the process of removal of SO2 from flue gas emissions through chemical processes.
    
    
  
  
  

 

News Summary:

• The Centre for Research on Energy and Clean Air (CREA) and Greenpeace India have released findings of anthropogenic sulphur dioxide (SO2) emissions globally, in a report titled- Annual Global Sulphur Dioxide Emissions.
  
  

Major Findings the report

• India –Top Emitter of SO2:
  • By contributing 21% of global anthropogenic emissions of sulphur dioxide, India continues to be at the top in the list of big emitters for the fifth year in a row.
    
    
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• Decline in Emissions
  • India has recorded a 6% decline in emission of hazardous sulphur dioxide (SO2) in 2019 compared to 2018, which is the first decline in four years.
    
    
  • The overall SO2 emissions fell for all the top three big emitters — India, Russia and China — for only the second time on record.
    
    
  • The declining trend continues, so far, even in 2020.
    
    
  
  
  
• Reasons for Decline
  • The findings attributed the decline in India’s SO2 emission to the country’s stride towards renewable energy and less consumption of coal.
    
    
  • The report, however, expressed concerns over growing resistance among existing coal-based power plants in India to move to cleaner technology in a time-bound manner as initially planned by the government in 2015.
    
    
  
  
  
• SO2 Hotspots in India
  • The report shows that the overall SO2 emissions in India are high despite recording a decline of 6% in 2019 with majority of power stations still lacking Flue-Gas Desulphurization (FGD) technology to reduce emissions.
    
    
  • As a result, the biggest emission hotspots are areas around coal-based power stations (or clusters of power stations) such as Singrauli, Neyveli, Mundra, Korba, Talcher, Korba, Kutch, Chennai, Chandrapur and Koradi.
    
    
  • These areas are part of the top 50 global hotspots of SO2 emissions. 
    
    
  • The researchers used satellite data and a global catalogue of SO2 emission sources from NASA to detect hotspots.
    
    
  
  
  

 

Environment Ministry’s Mandate at Reducing SO2 Emissions in India

• The environment ministry had in December 2015 introduced SO2 emission limits for coal-fired power stations and asked them to install flue-gas desulphurisation (FGD) to reduce emissions within two years.
  
  
• However, the December 2017 deadline for this was moved to 2022 after most of the units failed to install the technology within the timeframe.