Why India Exempt 78% Thermal Plants from Anti SO₂ Devices?

What is Flue Gas Desulfurisation (FGD)? What Is the Current Status of FGD Installation in India’s Thermal Power Plants? What Are the Trends in India’s SO₂ Emissions Over the Years? Which Countries Are the Top Emitters of SO₂ Globally?

In 2015, India stood at a critical environmental crossroads. Having just returned from the Paris Climate Conference, the government took a bold step: it mandated the installation of Flue-Gas Desulfurisation (FGD) systems in all coal-fired thermal power plants. The mission was clear—cut down sulfur dioxide (SO₂) emissions, which were dangerously high and contributing to the rising health burden across cities like Delhi, which had recently surpassed Beijing to become the world's most polluted city.

But ten years later, in July 2025, a major policy reversal shook environmental circles: the Ministry of Environment announced that 78% of India's thermal plants would now be exempt from installing FGDs. What caused this dramatic shift? And what does it mean for air pollution, public health, and the future of clean energy in India?

What Is FGD and Why Is It Important?

FGD, or Flue-Gas Desulfurisation, is a widely used pollution control technology meant to remove sulfur dioxide (SO₂) from the exhaust gases of coal-fired power plants. The process is fairly straightforward yet effective: flue gases are passed through a scrubbing solution—usually lime or limestone—which reacts with SO₂ to form by-products like calcium sulfite or calcium sulfate. These residues, whether in wet sludge or dry powder form, can then be repurposed in sectors like cement and wallboard manufacturing.

FGDs are generally classified into wet and dry systems, depending on the nature of the scrubbing process. While their operational costs are notable, the health and environmental benefits they provide—by cutting down SO₂—are significant.

2015: The Mandate to Install FGDs

Following international pressure and increasing domestic pollution concerns, India introduced its first-ever emission norms for coal plants in 2015. The rules required all existing thermal power plants to install FGDs within two years.

The urgency was unmistakable: Delhi's pollution levels were making global headlines, and SO₂ was a key culprit in the formation of PM2.5, a dangerous category of fine particulate matter.

But from the outset, implementation ran into hurdles. Power producers—both public and private—argued that the installation of FGDs would raise electricity tariffs, create supply chain bottlenecks, and strain already stretched budgets. At the time, projections showed that private sector plants would bear 45% of the total cost, while state and central plants would shoulder 32% and 24%, respectively.

Then came the COVID-19 pandemic, bringing construction work to a halt and disrupting global supply chains. By 2024, many deadlines had passed with limited on-ground progress.

July 2025: Who Still Needs FGDs and Who Doesn’t?

A full decade after the FGD mandate, the Ministry of Environment significantly revised the policy. Now, only a select group of thermal plants were required to comply. These were grouped into new categories:

• Category A included plants within 10 km of the National Capital Region (NCR) or any city with a population of over 1 million. These units must install FGDs by December 2027.

• Category B encompassed plants located near critically polluted areas or non-attainment cities. These would be reviewed case-by-case.

• Category C—which covers a staggering 78% of all thermal plants—was fully exempted from installing FGDs.

Moreover, plants scheduled to retire before December 2030 could also skip FGD installation, provided they submitted a formal undertaking.

To put it in perspective, 596 thermal units were originally supposed to comply between 2017 and 2024.

Why the Government Decided to Drop FGD Plans for Most Plants?

The government cited scientific research from leading Indian institutions—IIT Delhi, NEERI, and NIAS—to justify its rollback. According to these studies, widespread FGD deployment would not lead to a "notable" reduction in ambient SO₂ levels. The arguments included:

• Indian coal is low in sulfur, naturally emitting less SO₂.

• Existing plants are already fitted with 220-meter tall smokestacks, which help disperse emissions.

• India’s climate reduces the formation of acid rain.

• Most zones already meet national SO₂ standards.

• FGD systems themselves could increase CO₂ and PM emissions during operation.

On the basis of these findings, a formal notification was issued on July 11, 2025, granting broad exemptions to coal-based power stations across the country.

What Do Experts Say?

Environmental scientists and public health advocates were quick to voice concerns. A joint study by Harvard University and IIT Hyderabad presented compelling evidence contradicting the rollback:

• Nationwide FGD installation could reduce India’s average PM2.5 levels by 8%, and in areas near power plants by 7–28%.

• The move could help bring India’s annual PM2.5 average down from 50.6 µg/m³ (2024) to the national standard of 40 µg/m³.

• Most strikingly, it could prevent up to 48,000 premature deaths every year.

Critics also questioned the integrity of the government-backed studies. The Centre for Research on Energy and Clean Air (CREA) pointed out that the studies referenced only 18 cities over a period of 3 months, ignoring rural and downwind regions. The Centre for Science and Environment (CSE) further warned that SO₂ can travel over 300 km and remain airborne for up to 10 days, eventually forming sulfate aerosols that evade detection by traditional monitoring.

Are FGDs Really Too Expensive?

The government has often defended the rollback on the grounds of high costs, but several independent studies tell a different story. According to a 2018 study by CSTEP:

• The cost of nationwide FGD installation would be INR 2,540 billion (approximately USD 29.5 billion).

• The economic and health benefits would amount to INR 9,622 billion (about USD 112 billion).

• That translates to a return of INR 3.79 for every rupee spent.

Additionally, the Harvard-IIT Hyderabad study projected GDP benefits in the range of USD 18.1–604 billion annually, which could account for 0.44% to 10% of India’s total GDP.

How India’s SO₂ Emissions Compare with China’s?

India’s recent rollback stands in stark contrast to China, which has adopted a far more aggressive approach to controlling SO₂. According to NASA’s OMI satellite data:

• China has reduced SO₂ emissions by 75% since the early 2000s.

• India, on the other hand, has seen a 50% increase over the same period.

India’s key SO₂ hotspots include:

• Singrauli (MP)

• Neyveli & Chennai (TN)

• Talcher & Jharsuguda (Odisha)

• Korba (Chhattisgarh)

• Kutch (Gujarat)

• Ramagundam (Telangana)

• Chandrapur & Koradi (Maharashtra)

These regions consistently show high SO₂ concentrations, flagged repeatedly by NASA's OMI data.

How SO₂ Pollution Affects Our Health and Environment?

While SO₂ is not a greenhouse gas, its health implications are severe. Once released, it reacts with ammonia (NH₃) in the atmosphere to form ammonium sulfate, a major component of PM2.5.

Exposure to SO₂ and related compounds is associated with:

• Asthma, bronchitis, and other respiratory illnesses

• Heart disease and strokes

• Irritation in eyes, throat, and lungs

• Increased cardiovascular and respiratory mortality over long-term exposure

India's Power Minister Manohar Lal Khattar even suggested that sulfate aerosols reflect sunlight, offering a form of temporary cooling. But scientists warn this argument is dangerously misleading: such aerosols may mask warming for a short time, but their health consequences far outweigh any marginal climate benefit.

What This Means for India’s Future?

India’s decision to exempt the majority of thermal plants from FGD installation represents a significant turning point in the country’s environmental journey. While government bodies cite cost-effectiveness and national conditions, a wide body of research shows that the long-term health, environmental, and economic benefits of FGDs greatly outweigh their costs.

As coal continues to dominate India’s energy mix, it becomes all the more crucial that science, public health data, and sustainability goals drive policy—not just short-term economics. The future of India’s air, and the health of millions who breathe it, may depend on whether this rollback remains a pause—or a permanent retreat.

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