COAL POWER PLANTS & SO2 EMISSIONS: MAJOR CAUSE OF POOR AIR QUALITY IN DELHI

COAL POWER PLANTS & SO2 EMISSIONS: MAJOR CAUSE OF POOR AIR QUALITY IN DELHI

Why in News?

• A report by the Centre for Research on Energy and Clean Air (CREA) has revealed that 81% of sulphur dioxide (SO₂) emissions from coal-fired power plants within a 300 km radius of Delhi-NCR originate from plants that were exempted from mandatory installation of Flue Gas Desulphurisation (FGD) systems under the July 2025 notification.
• The findings come one year after the Union Government relaxed emission norms for most coal-based thermal power plants.
• Experts warn that increasing coal-based electricity generation, coupled with weaker emission controls, could worsen 5 pollution and public health outcomes.

KEY HIGHLIGHTS

Major Findings of the CREA Report

• 81% of SO₂ emissions around Delhi-NCR come from Category C coal plants exempted from FGD installation.
• Around 90% of estimated SO₂ emissions originate from plants operating without FGD systems.
• CREA assessed:
  • 12 coal-fired thermal power plants
  • 37 generating units
  • 25 units with sufficient publicly available data.
• Estimated SO₂ emissions in 2025:
  • 154 kilotonnes (kt)
• Category C plants alone contribute:
  • 125 kilotonnes (81%)
• Category A plants contribute:
  • 29 kilotonnes

WHY THE REPORT IS SIGNIFICANT?

• India is expected to witness higher coal-based electricity generation due to:
  • Rising electricity demand.
  • Reduced hydropower generation during strong El Niño
• Increased coal consumption without effective pollution controls may further deteriorate air quality in North India.

WHAT IS SO2?

Definition

• Sulphur dioxide (SO₂) is a colourless, toxic gas produced mainly by:
  • Burning sulphur-containing fossil fuels (especially coal).
  • Industrial processes.
  • Smelting operations.
  • Volcanic activity (natural source).

Major Sources in India

• Coal-fired thermal power plants.
• Petroleum refineries.
• Steel and cement industries.
• Industrial boilers.
• Heavy fuel oil combustion.

WHY IS SO2 A CONCERN?

Health Impacts

Exposure to SO₂ can cause:

• Respiratory diseases.
• Asthma attacks.
• Chronic bronchitis.
• Reduced lung function.
• Cardiovascular diseases.
• Stroke.
• Premature mortality.

Children, the elderly, and people with respiratory illnesses are particularly vulnerable.

Environmental Impacts

SO₂ contributes to:

• Formation of PM2.5 (secondary particulate matter).
• Acid rain.
• Soil acidification.
• Water pollution.
• Damage to crops and forests.
• Reduced visibility (haze).

HOW DOES SO2 FORM PM2.5?

Formation Process

1. Coal combustion releases SO₂ into the atmosphere.
2. SO₂ reacts with:
   • Oxygen
   • Water vapour.
   • Ammonia.
3. Forms:
   • Sulphate aerosols.
4. These become fine particulate matter (PM2.5).

Why PM2.5 is Dangerous

• Diameter less than 2.5 micrometres.
• Can penetrate deep into the lungs.
• Can enter the bloodstream.
• Causes long-term health problems and premature deaths.

WHAT IS FLUE GAS DESULPHURISATION?

FGD is an air pollution control technology used in coal-fired thermal power plants to remove sulphur dioxide (SO₂) from exhaust gases before they are released into the atmosphere.

Working Mechanism

• Flue gases pass through an absorber tower.
• Limestone or lime slurry reacts with SO₂.
• Converts SO₂ into:
  • Gypsum (Calcium Sulphate).
• Cleaned gases are released through chimneys.

Efficiency

FGD systems can remove:

• 90–95% of sulphur dioxide emissions.

Benefits

• Reduces SO₂
• Lowers PM2.5 formation.
• Prevents acid rain.
• Improves air quality.
• Protects public health.
• Helps meet emission standards.

INDIA’S EMISSION NORMS FOR THERMAL POWER PLANTS

2015 Notification

The Ministry of Environment, Forest and Climate Change (MoEFCC):

• Mandated FGD installation for all coal-fired power plants.
• Original compliance deadline: 2017

Repeated Extensions

The deadline was extended four times due to:

• High installation costs.
• Equipment shortages.
• COVID-19 disruptions.
• Implementation delays.

2021 Categorisation of Thermal Power Plants

Plants were classified into:

Category A

• Plants located within:
  • 10 km of Delhi-NCR
  • Million-plus cities
  • Critically polluted areas

Requirement

• Mandatory FGD installation.

Category B

• Plants near:
  • Non-attainment cities.

Requirement

• Compliance based on pollution levels.

Category C

• Remaining thermal power plants.

Initially:

• Required to install FGDs.

July 2025 Notification: Relaxation of Norms

The Union Government revised emission norms.

Category A

• Must install FGDs by 2027.

Category B

• Assessed on a case-by-case basis.

Category C

• Exempted from mandatory FGD installation.

These plants account for nearly:

• 78% of India’s coal-fired thermal power plants.

WHY IS CREA CRITICAL OF THE REVISED POLICY?

1. Location-Based Categorisation is Inadequate

The categorisation depends mainly on:

• Whether a plant is located within 10 km of a city.

However, SO₂ can travel:

• Hundreds of kilometres before converting into PM2.5.

Thus, Even distant power plants can significantly affect Delhi-NCR’s air quality.

2. Increased Coal Generation

India’s electricity demand continues to rise.

During strong El Niño years:

• Hydropower generation declines.
• Coal generation increases.

Without FGDs, SO₂ emissions are expected to rise substantially.

3. Weak Monitoring

CREA highlights:

• Limited public access to Continuous Emission Monitoring System (CEMS)
• Lack of transparency regarding:
  • FGD installation.
  • Operational status.
  • Compliance.

CASE STUDIES

Mahatma Gandhi Thermal Power Plant (FGD Installed)

Annual Generation

• Around 3,400–4,000 million units

SO₂ Emissions

• Unit 1:
  • 1,775 tonnes
• Unit 2:
  • 2,154 tonnes

Shows:

• Effective pollution control significantly reduces emissions.

Rajpura Thermal Power Plant (Without Effective FGD)

SO₂ Emissions

• Unit 1:
  • 20,851 tonnes
• Unit 2:
  • 22,690 tonnes

It emerged as:

• The largest SO₂ emitter in the study.

WHY DOES THIS MATTER FOR DELHI NCR?

According to CREA:

• The energy sector contributes up to:
  • 16% of particulate pollution in Delhi-NCR cities.

Combined with:

• Vehicular emissions.
• Construction dust.
• Biomass burning.
• Crop residue burning.

SO₂ significantly worsens winter smog.

CHALLENGES

• Increasing dependence on coal.
• Relaxed emission standards.
• Slow FGD implementation.
• Weak regulatory enforcement.
• Poor monitoring transparency.
• Rising electricity demand.
• Climate-induced reduction in hydropower.

CREA’S RECOMMENDATIONS

1. Reinstate Mandatory FGD Installation

• Make FGDs compulsory for all coal-fired power plants, irrespective of category.

2. Improve Transparency

• Publicly disclose:
  • Real-time CEMS data.
  • SO₂
  • Compliance reports.

3. Monitor FGD Performance

• Regularly publish:
  • Installation status.
  • Operational efficiency.
  • Maintenance records.

4. Strengthen Regulatory Oversight

• Ensure strict enforcement of emission norms.
• Periodic environmental audits.
• Independent verification of emissions.

5. Accelerate Energy Transition

• Expand renewable energy.
• Improve energy efficiency.
• Promote battery storage.
• Reduce dependence on coal over the long term.

 

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