India has withdrawn its decade-old mandate requiring coal-fired power plants to install flue gas desulphurisation (FGD) systems, significantly easing clean-air regulations for most of its thermal power fleet.

A recent gazette notification from the Union Ministry of Environment states that 79 per cent of coal-based power plants — those located beyond 10 kilometres of major cities — are now exempt from FGD installation, which is designed to curb sulphur dioxide (SO₂) emissions. An additional 11 per cent of plants near but not within urban centres will be reviewed on a case-by-case basis. Only 10 per cent of plants, primarily those near New Delhi and other cities with populations exceeding one million, are required to install FGDs by December 2027.

The move means the majority of India’s coal power units will no longer be obliged to install the costly pollution-control equipment, unless they are close to large urban areas.

The reversal follows findings that FGDs, while reducing SO₂, result in increased carbon dioxide (CO₂) emissions. A study commissioned by the Office of the Principal Scientific Adviser and conducted by the National Institute of Advanced Studies (NIAS), Bengaluru, challenged the 2015 policy. It argued that over 90 per cent of Indian coal has low sulphur content and that such retrofitting should be reserved for plants using imported or high-sulphur coal.

Additionally, India's thermal power plants, with 220-metre chimneys and favourable climatic conditions, already dilute SO₂ emissions. The NIAS report estimated that universal FGD use between 2025 and 2030 would lead to an extra 69 million tonnes of CO₂ emissions, while reducing SO₂ by only 17 million tonnes. It also noted that SO₂ has historically exerted a cooling effect on the atmosphere, based on Intergovernmental Panel on Climate Change (IPCC) data.

So far, only 11 per cent of coal plants — backed by Rs 334 billion (US$4 billion) in investment — have installed FGDs. Roughly half the units had placed orders or begun installations, raising concerns about cost burdens and competitive disparities. The new directive offers no clarity on how these issues will be resolved.

The NIAS team — R. Srikanth, A.V. Krishnan, and Dizna James — recommended a shift towards controlling particulate matter (PM), which poses a more severe threat in India due to the high ash content in domestic coal. The report suggested installing electrostatic precipitators developed by Bharat Heavy Electricals Limited (BHEL), which are cost-effective and reportedly eliminate 99 per cent of PM emissions.