Earlier this month, the government eased sulphur emission rules for coal-fired power plants, effectively exempting 79 per cent of the plants – including those located more than 10 km from populated and polluted cities – from installing FGD systems.
FGD stands for flue-gas desulphurisation, a system that removes sulphur from power plants’ exhaust gases. In 2015, the government had mandated that all coal-fired power plants install FGD systems to reduce sulphur dioxide emissions; the mandate now stands restricted.
The government’s move, which came after concerns were raised about increased carbon dioxide emissions from the operation of existing control measures and a “detailed analysis” by the Central Pollution Control Board (CPCB), may reduce electricity costs by 25-30 paise per unit, claim officials.
Also Read: Coal plants get exemption as Centre eases SO2 rules
But, the Centre for Science and Environment (CSE) and environmentalists are not buying the reasons for this shift. They are, instead, asking hard-hitting questions about the need to choose the lesser of the two evils – sulphur or carbon emissions – instead of finding a middle path.
Key findings and studies
The government claims that extensive deliberations and multiple independent studies were undertaken to formulate the new framework that categorises mandatory FGD installation only to plants located within 10 kilometres of cities with a population exceeding one million.
However, plants in critically polluted areas or non-attainment cities will be evaluated on a case-by-case basis, according to the new mandate.
All other plants are exempt from mandatory FGD installation.
Studies by IIT Delhi, CSIR-NEERI and the National Institute of Advanced Studies (NIAS), said the government, found that ambient sulphur dioxide levels in most parts of India were well within the National Ambient Air Quality Standards (NAAQS).
The IIT Delhi study, which was conducted in 2024 with support from the Ministry of Power, examined ambient SO₂ (sulphur dioxide) concentrations in 10 cities, covering a range of geographic and developmental categories.
It reported that daily mean SO₂ concentrations ranged from 2.97 to 16.17 micrograms per cubic metre, which was well below the NAAQS limit of 80 micrograms per cubic metre. More curiously, the study found no significant difference in SO₂ levels between cities with thermal power plants equipped with operational FGDs and those without them.
The study by NIAS Bangalore stated that over 92 per cent of electricity generated by Indian thermal power plants comes from coal with sulphur content that is below 0.5 per cent – a level considered low by international standards.
The organisation’s report suggested that a mandated installation of FGD systems in all thermal plants by 2030 could, in fact, result in a significant rise in Auxiliary Power Consumption, which could lead to an additional 69 million tonnes of carbon emissions from 2025-2030.
A reduction in SO₂ emissions, on the contrary, may be only about 17 million tonnes over the same timeframe.
New mandate and the reasons behind it
The current mandate that eases rules of FGD installation stems from a 2015 study that was conducted by professors Mukesh Sharma and Dikshit from IIT Kanpur. Their research led to the conclusion that secondary sulphate particles accounted for 8 to 21 per cent of PM2.5 pollution in Delhi during the winter months.
When they measured sulphur oxide levels across multiple cities, they found them ranging between 3 and 20 micrograms per cubic meter, which is below the NAAQS threshold of 80 micrograms per cubic meter.
Officials said studies had also questioned the environmental and economic efficacy of a universal FGD mandate in the Indian context.
When it comes to coal-fired power plants, Indian coal typically has a sulphur content of less than 0.5 per cent. When high stack heights and favourable meteorological conditions are taken into account, dispersion of SO₂ is efficient.
The NIAS study warned that retrofitting FGDs nationwide could be counter-effective, as it would add an estimated 69 million tonnes of CO₂ emissions between the time period of 2025 and 2030 due to increased limestone mining, transportation, and power consumption.
An affidavit incorporating these findings will be submitted shortly to the Supreme Court in the MC Mehta vs Union of India case, where FGD enforcement timelines have been under judicial scrutiny.
Why the industry backs new norms
Industry officials justified a relaxation in the norms, saying they would bring down the cost of electricity by 25-30 paise per unit, which would trickle down to consumers.
In a high-demand, cost-sensitive economy, the impact may help state discoms contain tariffs and reduce subsidy burden on governments.
Moreover, the financial burden of mandatory FGD retrofitting was previously estimated to be an exorbitant ₹2.5 lakh crore, or ₹1.2 crore per MW, with installation timelines of up to 45 days per unit – a figure that may even jeopardise grid stability during peak seasons.
A senior executive at a leading public sector utility called it a “rational, science-based move that keeps electricity affordable”.
ICP Keshari, the Director General of Power Producers Association (PPA), also hailed the decision as “good and consumer-centric”. Indian coal, he opined, “does not have any big sulphur oxide emission problems”.
“It is only the particulate matter which is of concern,” he added.
While acknowledging that the move will benefit power plants based on domestic coal, Keshari said the new FGD norm “identifies the problem and does not unnecessarily load cost on consumers”.
Concerns and questions
While government officials insist that the government remains committed to environmental protection, “under a smarter lens” and that the new mandate is "not a rollback but a recalibration based on evidence,” the Centre for Science and Environment (CSE) and environment activists have raised strong concerns about the shift in India’s FGD strategy.
The CSE argues that the current discussions around FGD installation have ignored a hugely critical aspect – the role of SO₂ in the formation of secondary PM2.5, a pollutant closely linked to severe respiratory and cardiovascular diseases.
Ambient SO₂ levels, which the new mandate is largely centred on, are not significant, says the body.
The CSE underscores that the 2015 IIT Kanpur study had already identified secondary sulphate aerosols as major contributors to PM2.5 concentrations in Delhi.
Yet, the government seemed to have downplayed this crucial connection, especially the impact of transboundary SO₂ emissions from surrounding operational power plants.
If the new recommendations are adopted, there would be increased chances of regulatory inconsistencies. The progress made so far in containing sulphur emissions could even stall over time, further disincentivising the adoption of cleaner technologies and reversing compliance momentum achieved over the past few years.
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