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One year after India relaxed pollution norms for most coal-fired power plants, a new analysis has found that the largest sulphur dioxide emitters around the Delhi-National Capital Region (Delhi-NCR) are the very plants no longer required to install pollution control systems, raising concerns about worsening air quality as coal generation is expected to rise.
Nearly 81 per cent of the estimated sulphur dioxide (SO2) emissions from coal-fired power plants within a 300-kilometre radius of Delhi-NCR originate from plants exempted from mandatory installation of flue gas desulphurisation (FGD) systems under the Union government’s July 2025 notification, according to a new analysis by the Centre for Research on Energy and Clean Air (CREA).
The findings come exactly a year after the Union Ministry of Environment, Forest and Climate Change revised emission norms, exempting 78 per cent of India’s coal-fired power plants from installing FGDs, a technology capable of cutting SO2 emissions by up to 95 per cent.
CREA assessed 12 coal-fired power plants comprising 37 generating units around Delhi-NCR. Of these, 25 units had sufficient publicly available data for analysis. The study estimates these units will emit around 154 kilotonnes of SO2 in 2025, with around 90 per cent of emissions originating from plants operating without FGD systems. Category C plants, which are exempt from mandatory FGD installation, accounted for 81 per cent of the estimated SO2 emissions.
The analysis assumes greater significance because CREA's recent El Niño assessment projects higher coal-based electricity generation under a strong El Niño scenario, driven by rising electricity demand and lower hydropower generation. Higher coal use without effective SO2 controls could further increase emissions in the Delhi-NCR region.
SO2 is a major precursor to fine particulate matter (PM2.5), which is associated with respiratory diseases, cardiovascular illnesses, stroke and premature deaths. According to a recent peer-reviewed study cited by CREA, the energy sector contributes up to 16 per cent of particulate pollution in Delhi-NCR cities.
India first mandated FGD installation at all coal-fired power plants in 2015, requiring compliance by 2017. The deadline was subsequently extended four times. In 2021, plants were categorised based on location, with stricter timelines for plants located close to major cities and polluted regions.
The July 2025 notification significantly diluted the framework. While Category A plants must still comply by 2027, Category B plants are assessed on a case-by-case basis, and Category C plants, which account for 78 per cent of India’s coal-fired power plants, no longer have to install FGDs.
CREA argues that the categorisation is flawed because it is based largely on whether a plant lies within a 10-kilometre radius of a city, even though sulphur dioxide can travel hundreds of kilometres before forming secondary PM2.5 pollution.
“The government should reinstate mandatory FGD installation for all coal-fired power plants, make real-time Continuous Emission Monitoring Systems data publicly available, and regularly disclose the operational status of FGDs. These measures will reduce SO2 and PM2.5 pollution, strengthen compliance, and improve air quality and public health,” said Manoj Kumar, analyst at CREA.
The assessment found that the Mahatma Gandhi Thermal Power Plant, equipped with FGD systems, emitted only 1,775 tonnes and 2,154 tonnes of SO2 from Units 1 and 2, despite generating roughly 3,400 to 4,000 million units of electricity annually.
By contrast, the Rajpura Thermal Power Plant, which lacked effective SO2 controls, emitted an estimated 20,851 tonnes and 22,690 tonnes from two comparable generating units, making it the largest emitter in the study.
Overall, Category A plants emitted an estimated 29 kilotonnes of SO2, while Category C plants emitted 125 kilotonnes, underscoring that the bulk of emissions now comes from facilities no longer required to install pollution control technology.
CREA has recommended that the government:
· Reinstate mandatory FGD installation for all coal-fired power plants, irrespective of category.
· Make real-time online Continuous Emission Monitoring Systems data publicly available to improve transparency and verify compliance.
· Regularly disclose the operational status of FGD systems.
According to CREA, these measures would substantially reduce SO2 emissions, curb PM2.5 formation, improve compliance with air quality standards and lower the health burden associated with air pollution, particularly as India is expected to increase coal-based power generation to meet rising electricity demand.