When cost trumps clean air

The claim of relaxing sulphur emission norms for thermal power plants being scientific may be misleading, writes Kalyan Ray

Ten years after creating rules to make thermal power plants cleaner, the Union Ministry of Environment and Forest has decided to go easy on the power sector. It has tweaked the norms, exempting most power units from installing costly equipment to clean up the coal exhaust, arguing that such instruments are not required for them.

Last week, in a gazette notification, the ministry restricted the 2015 mandate to install flue-gas desulphurisation (FGD) systems, which remove sulphur from power plants’ exhaust gases, only to facilities located within 10 kilometres of cities with a population of more than 10 lakh.

Plants in critically polluted areas or non-attainment cities will be evaluated on a case-by-case basis while all other units — accounting for 79% of India’s thermal power capacity — are exempt from mandatory FGD installation, as stipulated in the 2015 rules.

‘The measure is scientific’

With criticism mounting, the ministry issued a clarification, stating that the decision was based on studies conducted by the Indian Institute of Technology, Delhi, the CSIR’s National Environmental Engineering Research Institute in Nagpur, and the National Institute of Advanced Studies (NIAS) in Bengaluru.

“The revised sulphur dioxide emission policy is not a rollback of environmental safeguards, but a pragmatic, scientifically justified shift towards more targeted, cost-effective and climate-coherent regulation,” the ministry says.

Indian coal has a very high ash content (42%), compared to imported coal, which has less than 10%. However, domestic coal contains little sulphur (less than 0.5%) compared to imported coal, which has more than 2% of it. The ministry claims 94% of electricity generated by thermal power plants is fuelled by Indian coal, and this may be the reason for very low ambient sulphur dioxide levels in Indian cities.

Therefore, according to the government, further filtering of sulphur oxides is not necessary for most plants operated by the public and private sectors.

As per the Central Electricity Authority, 44 thermal power plants are equipped with FGDs, while another 233 FGDs have been awarded out of 537 power plants identified for installation. Retrofitting of the equipment in each operating plant requires shutdown times of more than 45 days.

The NIAS in its report – that also takes into account the conclusions of IIT Delhi and NEERI studies - recommends a halt for FGD installations for the time being because of low-sulphur content of Indian coals, 220-275 mt tall stacks (vertical distance from the ground to top of the chimney) of thermal power plants, and tropical climate.

The institute suggests studies to assess the impact of FGDs in controlling secondary particulate matter pollution from 32 thermal power plants located within 10 km of cities with a population of more than 10 lakh which have either installed FGDs or are at various stages of installing them.

“We don’t know the terms of reference for any of these studies. These documents are not in the public domain. Also, we have not heard anything from the Central Pollution Control Board, whose job is to set the emission standards,” Nivit Yadav, programme director, industrial pollution and renewable energy at the Centre for Science and Environment, a Delhi-based think tank, tells DH.

The ministry argues that nationwide retrofitting of India’s coal-based capacity for ensuring compliance with the previous SO₂ norms is projected to cost over Rs 2.54 lakh crore in capital expenditure (around Rs 1.2 crore per MW of installed capacity).

“In light of the limited incremental benefit to ambient PM2.5 levels and the high marginal cost of pollution reduction, such investment must be carefully scrutinised,” it claims, noting that there is barely any difference in sulphur and ambient dioxide concentration in the ambient air of cities with or without FGD.

Misinterpretation?

However, an analysis released last month by the Centre for Research on Energy and Clean Air states that studies by NEERI, NIAS, and IIT Delhi are being “selectively used to justify inaction” by power plants across the country, which continue to delay the installation of FGD units to control sulphur dioxide emissions.

According to the CREA report, the NEERI’s assertion on low levels of ambient sulphur dioxide is “highly misleading”.

“The air quality monitoring stations don’t capture the real impact of power plant pollution because they don’t track whether emissions drift upwind or downwind, and they certainly don’t account for chemical reactions that convert SO2 into other pollutants like PM2.5,” says the report.

“Using low ambient readings to argue against FGD is not just scientifically wrong, it completely misleads about how pollution control works,” it adds.

The CREA has also identified loopholes in the IIT report. A 2022 study by IIT Delhi recommended a phased rollout of FGDs across all coal-based power stations, but in their 2024 report, the IIT team contradicted their earlier findings, relying on data from six cities.

“The newer IIT Delhi report recommended halting FGD installations in plants that have yet to adopt them, despite the fact that 92% of plants still lack FGDs. This shift was justified by citing low ambient SO₂ levels and limited impact, overlooking the secondary particle formation,” it says. The ministry’s counter is that such particle formation matters little to ambient air pollution.

There are other questions, too. “Exempting all Category C plants from SO₂ norms solely based on location overlooks cumulative pollution, especially in mining areas like Singrauli or Korba, which are not “officially” critically polluted areas but are still heavily impacted,” adds the CSE.