IIT studies make case for enforcement of SO2 norms at our coal power plants: CREA

In light of the ongoing debate on whether flue gas desulphurisation (FGD) systems in coal-fired thermal power plants (CFPPs) are required, the Centre for Research on Energy and Clean Air (CREA) analysed data on India’s FGD status, SO2 emissions, and from scientific studies published by IIT Delhi and IIT Mumbai in 2025. CREA says that the findings are alarming: delays in enforcing pollution control measures have led to widespread non-compliance, putting India’s air quality and public health at serious risk.

Two new scientific assessments – one by IIT Delhi and another by IIT Bombay – have reinforced the urgent need for regional, sector-specific air quality interventions in India. CREA says that both studies conclude that regional air pollution cannot be solved by city-level action alone, urging a shift in clean air policy thinking.

IIT Delhi’s research mapped nine to 11 major regional airsheds that shift with seasons, influencing pollution patterns both across and within states. The study finds that transboundary pollution contributes the most to PM2.5 levels (13%-94%), followed by domestic emissions (2%–41%), industry (1-25%), transport (1-12%), and power (1-12%) sectors. Another of the study’s significant findings is the dominance of secondary PM2.5 (formed from chemical reactions involving SO2 and NOx in the atmosphere) rather than primary PM2.5.

CREA held that the regional sources in India are responsible for nearly 81% of secondary PM2.5 exposure, with residential fuel use (22%), industry (14%), and power plants (11%) being the top contributors. It’s found that the agricultural burning spikes only post-monsoon in the north, while road dust contributes relatively little.

The IIT Bombay study further strengthens the case for regional action. By analysing transboundary contributions using two independent models, researchers found that on average, 85% of urban PM2.5 across 143 cities originates from outside city limits. In 107 of 122 NCAP cities, transboundary sources account for more than 80% of PM2.5 levels. The main contributors to this cross-boundary pollution are domestic biomass burning (32%), energy generation (16%), and industry (15%). The findings clearly indicate that even the complete elimination of within-city emissions will fall short of meeting NCAP’s clean air targets unless regional sources are addressed.

FGD must be mandated to curb SO2 emissions

The emission norms, originally released in 2015, required all CFPPs to install FGDs by 2017. However, sluggish progress has led to repeated extensions. The latest extension, announced in December 2024 by the Ministry of Environment, Forest and Climate Change (MoEFCC), pushes compliance deadlines further to 2029, marking the fourth such extension. There has been some progress in expanding EV (electric vehicle) adoption and clean cooking solutions to reduce transport and domestic sector emissions. However, emissions from industries and the power sector remain largely unaddressed, continuing to be major sources of pollution.

CREA finds that 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%).

A recent reply to a Rajya Sabha parliamentary question reveals that a large number of power plants continue to emit SO2 at alarmingly high levels. For instance, thermal power plant units subject to the most stringent norm of 100 mg/Nm³ averaged 1,068 mg/Nm³ – over ten times the limit. Plants under the 200 mg/Nm³ and 600 mg/Nm³ norms averaged 996 mg/Nm³ and 1,007 mg/Nm³, respectively, showing significant exceedances.

Also, it is not just a problem for the Indo-Gangetic Plain or heavily polluted areas – SO2 emissions from CFPPs affect regions far beyond the plants’ physical location. Therefore, FGD systems must be mandated across the country to prevent cumulative and far-reaching air pollution.

While punitive action is swiftly taken against seasonal stubble burning by farmers, year-round emissions from the thermal power plant continue with minimal enforcement. Strong regulatory mechanisms, transparency in emission data, and strict penalties for non-compliance – similar to those in agricultural sectors – are essential to truly tackle India’s air pollution crisis.