New Delhi: India emits the highest amount of sulphur dioxide (SO₂) in the world and is the second-largest emitter of ammonia (NH₃), according to a new analysis by the Centre for Research on Energy and Clean Air.
The report warns that these gases are forming toxic secondary pollutants, particularly ammonium sulfate, which accounts for nearly one-third of India’s deadly PM2.5 air pollution.
Published on Friday, the report by Manoj Kumar and Rosa Giriens examines air quality data across 130 Indian cities under the National Clean Air Programme (NCAP).
While NCAP focuses largely on PM10, the findings suggest that secondary particles are a major but overlooked source of PM2.5 across India.
The CREA analysis finds that cities with the highest concentrations of ammonium sulfate – a compound formed when SO₂ reacts with ammonia in the atmosphere – include Patna (22.5 µg/m³), Muzaffarpur (21.7 µg/m³), Kolkata (21.7 µg/m³), Howrah (21.7 µg/m³), and Varanasi (21.6 µg/m³).
In contrast, cities with the lowest concentrations are Srinagar (3.9 µg/m³), Thoothukudi (5.9 µg/m³), Madurai (6.2 µg/m³), Trichy (6.7 µg/m³), and Kohima (6.9 µg/m³).
The analysis identifies SO₂ emissions from coal-fired thermal power plants (TPPs) as the biggest contributor to ammonium sulfate formation, with these plants accounting for over 60 percent of India’s SO₂ output. This makes the installation of flue gas desulfurisation (FGD) systems at TPPs a critical intervention.
In a major step toward tackling industrial air pollution, a new report recommends a nationwide phased rollout of Flue Gas Desulfurization (FGD) systems in coal-based thermal power plants (TPPs) across India.
The move aims to significantly reduce sulfur dioxide (SO₂) emissions, a key pollutant from coal combustion that poses serious risks to both the environment and human health.
Following the revision of emission norms under the Environment (Protection) Amendment Rules, 2015, many TPPs are now required to curb SO₂ emissions to comply with stricter standards.
The study analyzed emissions data from 240 stacks across 67 TPPs and combined satellite observations, emission inventories, and atmospheric modeling to understand pollution patterns and identify priority areas for FGD installation.
According to the report, implementation of FGDs can lead to a reduction of up to 55% in SO₂ concentrations around the plants, with the most significant benefits seen within 60–80 kilometers from each facility.
Additionally, sulfate aerosols formed from SO₂ can travel much farther; FGD installation is projected to reduce sulfate concentrations by up to 30% as far as 200 kilometers away.
Four major TPPs—Mundra (Gujarat), Vindhyachal (Madhya Pradesh), Talcher (Odisha), and Panipat (Haryana)—were analyzed for seasonal dispersion patterns, with results confirming that SO₂ emissions can spread widely depending on the time of year and local geography.
Further modeling for Delhi NCR revealed that energy sector emissions contribute around 63% to SO₂ levels in the region, underscoring the importance of curbing emissions from power plants.
The report recommends a five-phase national rollout of FGDs over a twelve-year period.
Phase 1, covering 40 TPPs, runs from July 2022 to July 2025. Phase 2, targeting 49 more plants, will occur from July 2026 to July 2029. Phases 3, 4, and 5 will follow, covering the remaining 55 plants by July 2034.
The phased approach allows time to evaluate performance, address operational challenges, and take advantage of emerging cleaner technologies.
The authors urge a detailed follow-up study after Phase 1 to evaluate the broader impacts of FGD installation, including its effect on CO₂ emissions, water use, limestone mining, and the disposal of byproducts like gypsum.
While the environmental and health benefits of reducing SO₂ are clear, the report stresses the importance of ensuring that these gains do not come at the cost of increased greenhouse gas emissions or resource strain.
This action plan offers India a clear roadmap for aligning power generation with environmental protection goals while addressing urban air quality challenges, especially in non-attainment cities struggling to meet national air quality standards.
