Amidst the ongoing debate over the necessity of flue gas desulphurisation (FGD) systems in coal-fired thermal power plants (CFPPs), the Centre for Research on Energy and Clean Air (CREA) examined the current status of FGD implementation, sulphur dioxide (SO₂) emissions, and insights from two new scientific studies published in 2025 by IIT Delhi and IIT Bombay. The analysis reveals a troubling picture of delayed enforcement and persistent non-compliance across the power sector.
One of the IIT Delhi study’s significant findings is the dominance of secondary PM2.5 rather than primary PM2.5. Secondary PM2.5 forms in the atmosphere due to chemical reactions of precursor gases such as SO₂. Annually, local sources contribute about 81% of India’s secondary PM2.5. Population-weighted exposure to secondary PM2.5 across India comes from the residential sector (22%), industry (14%), power (11%), and transport (11%).
The IIT Bombay study assessed the share of transboundary pollution in urban PM2.5 levels across 143 Indian cities using modelling approaches. On average, transboundary sources accounted for around 85% of PM2.5, with 107 of the 122 NCAP cities recording more than 80% of their pollution load from outside their boundaries. The findings imply that most cities, even with complete elimination of local anthropogenic sources, cannot meet the national clean air targets.
The study also identified biomass burning (32%), energy generation (16%), and industry (15%) as the top contributors to transboundary PM2.5.
Stalled progress on FGD poses huge public health risk
Initially notified in 2015, the emission norms mandated the installation of FGD systems to reduce SO₂ emissions by 2017. However, progress has been sluggish, leading to multiple extensions. In December 2024, the Ministry of Environment, Forest and Climate Change (MoEFCC) announced a fourth extension, pushing the compliance deadlines further till 2029.
In FY 2024–25, out of a total of 537 CFPP units, 44 had FGD systems installed, a mere 8% of the total units in India. Among the 493 units without FGDs, 380 (77%) were exceeding the prescribed limits, 59 (12%) were found complying with emission norms, and data was not available for the remaining 54 units (11%). These findings paint a disturbing picture of non-compliance, with a significant proportion of power plants continuing to release SO₂ at dangerously high levels.
While stringent penalties have been imposed on farmers for seasonal agriculture residue burning, the year-round industrial and power sector emissions continue largely unchecked due to regulatory leniency and delays in enforcement. Without robust compliance mechanisms, air quality will continue to deteriorate despite existing policies. If transparency in emissions data is ensured and penalties for non-compliance in the power sectors are enforced with the same rigor as biomass burning, pollution levels could be significantly reduced.
