THE CONTEXT: In December 2015 the Ministry of Environment, Forest and Climate Change (MoEFCC) tightened emission norms for all 537 coal-fired thermal power plants and made installation of FGD systems mandatory. Compliance has remained abysmally low (only 39 units commissioned by August 2024), and a high-level committee chaired by Principal Scientific Adviser (PSA) Ajay Sood (April 2025 study; June 2025 media reports) has advised rolling back the blanket mandate, citing cost, limited SO₂ benefit, and grid reliability arguments.
THE BACKGROUND:
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- Policy timeline: 2015 norms set the first deadline for 2018. Extensions were given in 2017, 2021, Sept 2022, and 30 Dec 2024 (latest: 2024/ 25/ 26 for Category A/B/C plants).
- Installed coal capacity: ~214 GW (Jan 2025 CEA data), which equals 46 % of the total generation mix.
- Cost profile: Average capital cost ≈ ₹1.2 crore / MW; nationwide roll-out on 219 GW equals > ₹2.5 lakh crore.
- Funding for clean air: NCAP launched 2019 with an initial CAMPA corpus > ₹6,000 crore and XV Finance Commission grants; utilisation still < 60 %.
WHAT IS AN FGD UNIT?
A post-combustion pollution-control system that brings flue gas (SO₂-rich exhaust) into contact with an alkaline sorbent so that sulphur oxides are chemically converted to benign salts such as gypsum (CaSO₄·2H₂O). Removal efficiencies: 70 – 95 % depending on design.
| Technology | Principle | Water use | By-product | Typical Indian application |
|---|---|---|---|---|
| Dry sorbent injection (DSI) | Limestone/lime powder injected into hot duct; reaction in-situ | Very low | Dry CaSO₃/CaSO₄ dust collected in ESP/fabric filter | Small-medium units, peaking plants |
| Wet limestone ‘scrubber’ | Counter-current contact of gas with limestone slurry | High (1.2 – 1.3 m³/MWh) | Commercial-grade gypsum | Most new super-/ultra-super-critical units |
| Seawater scrubbing | Uses alkalinity of seawater; no reagent cost | Moderate (return-flow required) | No solid; effluent aerated before discharge | Coastal stations (Mundra, UMPP-Krishnapatnam) |
TECHNICAL TERMS EXPLAINED:
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- Electrostatic precipitator (ESP): an upstream particulate-control device that charges ash particles and captures them on grounded plates.
- Stoichiometric ratio (SR): molar ratio of Ca to S; SR ≈ 1.05 in well-optimised wet FGDs for 93 % removal.
- Gypsum saleability: IS 1288-2019 grade gypsum from FGDs can substitute for 15 % natural gypsum in cement.
WHY IS SO₂ A CONCERN?
Sulphur dioxide is not a long-lived greenhouse gas but is a major precursor of secondary sulphate aerosols (PM 2.5). Modelling by CEEW–IIASA shows coal combustion accounts for ~15 % of India’s ambient PM 2.5, and ≈ 80 % of that load is formed via SO₂ oxidation. Chronic exposure elevates cardiopulmonary mortality; SO₂ also triggers acid deposition, harming crops and freshwater ecosystems.
DRIVERS OF THE ROLLBACK DEMAND
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- Capital strain on GENCOs & DISCOM pass-through: ₹ 0.60 – 0.75 / kWh tariff rise forecast.
- Domestic coal’s low sulphur (0.3 – 0.6 %) and tall stacks (220 m) allegedly disperse SO₂ – an argument raised by NIAS and NITI Aayog.
- Supply-chain limits: BHEL and three private vendors can together fabricate < 18 GW year-¹ – complete retrofit would stretch well beyond 2032.
- Water stress in arid pit-head locations: Wet scrubbers add ~2 % to station water consumption, clashing with 2016 CEA zero-liquid-discharge norms.
- Opportunity-cost narrative: funds might yield larger PM 2.5 gains if spent on electrostatic precipitator upgrades, coal beneficiation, and urban clean-air plans.
COUNTER-ARGUMENTS FROM PUBLIC-HEALTH & ENVIRONMENT AGENCIES
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- IIT-Delhi source-apportionment shows sulphate makes up 25 – 30 % of winter PM 2.5 in the Indo-Gangetic Plain; SO₂ cut is therefore “low-hanging fruit”.
- CEEW estimates monetised health damage of coal SO₂ at ₹ 1.7 / kWh – several times higher than the ₹ 0.75 FGD tariff impact.
- Rolling back nullifies the MoEFCC compensation regime notified in 2022 (₹ 0.20 – 0.40 / kWh penalty for non-compliance).
GLOBAL PERSPECTIVE & BEST PRACTICES
| Jurisdiction | Policy Lens | Outcome | Lesson for India |
|---|---|---|---|
| United States – Title IV Acid Rain Programme (1990) | Cap-and-trade on SO₂; plants opted for low-sulphur coal + FGDs | 88 % SO₂ cut (1990-2020) at ¼ predicted cost | Market mechanisms lower compliance cost |
| China (2005 – present) | Mandatory wet FGDs + feed-in tariff bonus; retro-fit rate > 95 % by 2015 | SO₂ emissions fell 87 % despite coal growth | Centre-aligned fiscal incentive accelerates retro-fits |
| EU Large Combustion Plant Directive (LCPD) | Emission ceilings + opt-out (limited operating hours) | Older plants retired; SO₂ down 85 % (1990-2020) | Time-bound ‘exit or comply’ maintains ambition |
THE ISSUES:
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- Regulatory credibility gap: Four extensions erode faith in the environmental rule of law; States hesitate to enforce CPCB directions.
- Asymmetric burden: 65 % of non-compliant capacity is state-owned; private IPPs fear tariff-pass-through delays by SERCs.
- Gypsum logistics: annual FGD gypsum potential (100 Mt by 2030) exceeds current cement industry uptake; disposal risk if end-use market not widened.
- Water-energy-pollution trade-off: Wet FGD effluent is chloride-rich; retrofits must co-install zero-liquid-discharge (ZLD) units, inflating cost.
- Skill & O&M gap: Continuous emission monitoring systems (CEMS) are often dysfunctional; manpower shortfall in SPCBs undermines oversight.
THE WAY FORWARD:
Prioritised roll-out: Sequence FGD retrofits first for units within 300 km of non-attainment cities; link deadlines to local health-cost modelling for maximum social benefit.
Green finance window: Create a Viability Gap Funding-cum-interest-subvention line under the National Clean Air Programme to cut effective capital cost by 20 %.
SO₂ trading pilot: Extend Gujarat–Maharashtra particulate ETS logic to a multi-state SO₂ market; power plants that over-comply can monetise surplus allowances.
Domestic manufacturing push: Notify minimum 60 % local-content requirement and Production-Linked Incentive for critical FGD components (mist eliminators, alloy absorbers).
Lifecycle gypsum strategy: Mandate BIS-conforming FGD gypsum use in cement, drywall, and road-base projects via revised CPWD Schedule of Rates.
De-risk tariff impact: Allow automatic pass-through of fixed FGD cost under the Electricity (Timely Recovery of Costs) Rules 2021 to avoid regulatory lag for generators.
Accelerated retirement of sub-critical fleet: Offer a sunset clause – plants older than 25 y can skip FGDs if they commit to shut down by 2030, aligning with Just Transition funds.
Real-time compliance transparency: Integrate CEMS data with the PRANA portal; publish hourly plant-wise SO₂ dashboard to empower communities.
Strengthen SPCBs: Ring-fence 20 % of NCAP grants for staff augmentation and forensic audits of FGD performance to close the enforcement loop.
Regional airshed planning authority: Constitute a statutory Indo-Gangetic Airshed Council to harmonise State action plans and avoid pollution ‘leakage’ across borders.
R&D on multi-pollutant scrubbers: Fund NTPC-IIT-BHU collaborative pilot on SNOX technology that simultaneously removes SO₂, NOₓ and particulates, halving capex/MW.
THE CONCLUSION:
A calibrated FGD compliance pathway safeguards co-benefits—public-health, Paris-aligned co-pollutant cuts, gypsum circularity, just-transition finance—while upholding the Precautionary Principle and Polluter Pays Principle under Article 48-A and judgements such as M.C. Mehta v. UOI (1987). Weakening the mandate risks reputational damage ahead of Global Stocktake-2 and undermines India’s NCAP and SDG 3.9 targets.
UPSC PAST YEAR QUESTION:
Q. What are the key features of the National Clean Air Programme (NCAP) initiated by the Government of India? 2020
MAINS PRACTICE QUESTION:
Q. India’s debate on Flue-Gas Desulphurisation (FGD) captures the larger energy-environment-equity trilemma. Examine
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