In a major move to address industrial air pollution, the Supreme Court of India held a crucial hearing on April 29, 2025, to review the compliance of thermal power plants (TPP) within a 300-kilometre radius of Delhi with sulphur dioxide (SO₂) emission norms.
The hearing took place under the long-standing environmental litigation case MC Mehta vs Union of India & Others filed in 1985. The bench, comprising Justice Abhay S Oka and Justice Ujjal Bhuyan, reviewed the compliance status of 11 thermal power stations and examined the central government’s progress in issuing formal notices to non-compliant plants.
The court focused on two major questions, the first being reclassification of TPPs: Whether the existing classification of TPPs within 300 km of Delhi could be amended, particularly to reclassify some Category C plants as Category A, imposing stricter emission deadlines. This would mean amending Schedule I of the Environment (Protection) Rules, 1986, which currently defines emission norms and timelines for different categories of power plants.
The second was the timeline for compliance with SO₂ standards. Given repeated extensions and rising public health concerns, the court scrutinised delays in enforcing pollution control norms. Over the years, the government granted multiple extensions, delaying the implementation of critical technologies like flue gas desulphurisation (FGD).
In a previous hearing on April 2, 2025, the court noted that while National Capital Power Station Dadri in Uttar Pradesh and Mahatma Gandhi Super Thermal Power Project in Jhajjar, Haryana were fully compliant, others — such as Indira Gandhi Super Thermal Power Project (under NTPC Ltd and Haryana Power Generation Company Ltd) and Harduaganj Thermal Power Station in Uttar Pradesh (owned by UP Rajya Vidyut Utpadan Nigam Ltd) — showed partial compliance.
In the case of Rajpura TPP in Punjab (operated by Nabha Power Ltd (NPL), under Larsen & Toubro), the court found that the FGD system had been installed but was not operational.
The Supreme Court directed the central government to submit the official addresses of nine non-compliant or partially compliant TPPs with SO₂ emission norms to issue formal legal notices. Each notice would include a copy of the court’s April 2, 2025 order and the plants will be informed of their obligation to respond or appear in court. However, during the April 29 hearing, it emerged that the government had not yet submitted the required addresses.
Despite the overall delay, there was a positive step; advocate EC Agrawala, representing NPL for the Rajpura TPP in Punjab), independently submitted the company’s address to the court on April 17. The Supreme Court Registry issued a formal notice via speed post on April 22, and NPL e-filed a reply on 28 April.
NPL, which has an installed capacity of 2 units of 700 megawatts capacity each in Rajpura, told the Supreme Court that it could not start using its FGD system because it was facing problems proocuring limestone, a key material needed to run the system. Although the FGD system has been set up, it cannot be operated in the absence of adequate quantity and quality of limestone. The company also claimed Punjab State Power Corporation Ltd (PSPCL) was not participating in the procurement to buy the limestone needed to run the system.
NPL had signed a Power Purchase Agreement with PSPCL in 2010, under the regulatory oversight of the Punjab State Electricity Regulatory Commission (PSERC). At that time, the installation of FGD systems was not mandatory for thermal power plants and hence, was not included in the original bid parameters.
After environmental norms were updated to require FGD technology, NPL sought cost recovery under a ‘Change in Law’ provision, which was denied by PSERC. Although the Appellate Tribunal for Electricity (APTEL) ruled in favour of the company, PSPCL challenged the order in the Supreme Court. The matter is now sub-judice and the final judgement is awaited.
The installed FGD system has not been put into use because of the ongoing dispute over electricity tariffs between the power company and the distribution company (discom), NPL told the SC.
While NPL highlighted its case, several other plants are also not meeting SO₂ emission standards. To ensure that FGD systems are properly implemented and operated, it is important to understand the deeper issues and lack of coordination among key stakeholders — State Electricity Regulatory Commissions, distribution companies (discoms), and power generators.
The Union of India’s counsel requested the SC to grant a two-month extension to assess whether TPPs’ current SO₂ compliance deadline (latest by December 31, 2029 for category C plants at present) could be amended. The government argued that altering timelines could trigger tariff revisions, as power producers may claim ‘Change in Law’ cost recovery.
Changing the deadline for compliance could have financial consequences, the counsel explained. If power plants are required to install FGD or other pollution control systems earlier than planned, it would be treated as a “change in law” under electricity regulatory frameworks. This would allow power producers to legally ask for higher tariffs to recover the extra costs. Hence, the authorities needed time to evaluate this aspect carefully.
Acknowledging the need for regulatory and financial review, the court granted the extension, allowing the government to submit a detailed assessment.