Govt defends revised framework for SO2 emission norms

SO2 is a harmful gas and is emitted when coal is burned in energy production. It also aids formation of secondary pollutants.

“The norms of Sulphur Dioxide emissions from Thermal Power Plants notified on 11th July is based on extensive consultations with stakeholders and research institutions regarding the effectiveness and rationale behind stack emission standards for SO2 on 537 TPPs throughout the country, and its role in overall ambient air pollution of the region,” a ministry statement said.

“Further, the norms were based on detailed scientific studies which were carried out by premier institutions such as IIT Delhi, National Institute of Advanced Studies as well as by the National Environmental Engineering Research Institute (NEERI)…besides scientific examination by the Central Pollution Control Board,” it added.

The ministry said: “Current exposure levels provide no credible evidence to suggest that SO2, under prevailing ambient conditions, is a major public health concern. Moreover, sulfate (sic) aerosols formed from SO2 constitute a relatively small fraction of PM (particulate matter) 2.5.”

The SO2 emission norms for coal and lignite power plants were first introduced in 2015. Later, the compliance timelines for plants were divided into three categories, based on the location of the plants.

The July 11 order said that plants in Category A, which are located within 10 kms of the Delhi-National Capital Region (NCR) or cities with a million plus population have to continue complying with the norms by the end of 2027.

For category B plants, located within 10-km of critically polluted areas or cities not in compliance with national ambient air quality standards will apply on a case to case basis, based on recommendations of an expert appraisal committee. For Category C plants, located outside of these two areas, will be completely exempted from meeting the SO2 norms. However, they will have to comply with stack height criteria.

The ministry notification said that thermal power plants due to retire before December 2030 shall not be required to meet the SO2 emission norms, provided they submit an undertaking for exemption. A compensation at the rate of Rs 0.40 per unit of electricity generated would be levied if they continue to operate beyond the 2030 timeline.

Out of the 600 units of coal fired power plants, 537 were identified for installation of flue-gas desulphurization (FGD) technology, to curb SO2 emissions.

The ministry said in a detailed note as per rough estimates, Rs 2.54 lakh crore of capital expenditure would be needed for nationwide retrofitting of coal-based capacity with FGD devices to meet SO2 emission norms. “ In light of the limited incremental benefit to ambient PM2.5 levels and the high marginal cost of pollution reduction, such investments must be carefully scrutinized,” the ministry said.

“The revised sulphur dioxide emission policy is not a rollback of environmental safeguards, but a pragmatic, scientifically justified shift toward more targeted, cost-effective, and climate-coherent regulation. It reflects declining ambient sulphur dioxide levels, recognizes the limited role of sulphur dioxide in driving PM2.5 health impacts, and weighs the disproportionate resource and environmental costs of indiscriminate FGD mandates,” the ministry added.