Sulphur Dioxide Emission Norms Relaxed

The Ministry of Environment, Forest and Climate Change has notified the Environment (Protection) Fourth Amendment Rules, 2025, revising the sulphur dioxide emission standards that had been issued in December 2015 vide SO 3305(E) for coal- and lignite-based thermal power plants (TPPs) in the country. The change is a result of multiple representations by stakeholders requesting exemptions or relaxation in timelines due to limited availability of technology providers, techno-economic feasibility, the negative impact of the COVID-19 pandemic on the supply chain, price escalation, low sulphur dioxide concentration in ambient air and heavy burden on consumers. This reverses the decade-old mandate that required nearly 540 coal-based power units to install flue-gas desulphurisation (FGD) systems that remove sulphur from the plants’ exhaust gases in phases starting in 2027.

The revised rules categorise TPPs located within a 10 km radius of the National Capital Region or cities having a million-plus population as Category A, within a 10 km radius of Critically Polluted Areas or Non-attainment cities as Category B and the remaining as Category C. Where Category A plants had to either comply or retire their units by 2022, Categories B and C have been given a deadline of retiring their units for exemption from compliance with the emission standards for parameters other than sulphur dioxide emissions by the end of this year. Plants not compliant with the timeline specified in the rules shall be liable for compensation at the rate of rupees 0.40 per unit of electricity generated in case their operation is continued beyond the specified date.

For sulphur dioxide emission, plants declared to retire before 31st December 2030 shall not be required to meet the specified standards if they submit an undertaking to the Central Pollution Control Board and Central Electricity Authority for exemption due to retirement. Post that compensation shall be levied at a rate of 0.40 rupees per unit of electricity generated.

• Existing Category A thermal power plants and those under commissioning, constituting almost 10% of the total TPPs, shall comply with the Sulphur dioxide emission standards by installing desulphurisation equipment by 31st December 2027.
• For Category B plants, constituting approximately 11% of TPPs, the applicability of Sulphur dioxide emission standards shall be decided on a case-to-case basis by the central government based upon the recommendations of the Expert Appraisal Committee in charge of TPPs constituted under Environment Impact Assessment notification 2006 based on appropriate scientific studies.
• The applicability of the emission standard on the Category C TPPs, i.e., the remaining 79%, shall be dependent on compliance with stack height criteria notified vide notification number GSR 742 (E) by 31st December 2029.