Thermal power plants polluting Delhi NCR's air 16 times more than stubble burning, study finds

According to CREA estimates, 281 kilotonnes of sulphur dioxide (SO₂) were released by coal-fired thermal power plants in NCR between June 2022 and May 2023.

A study conducted by the Centre for Research on Energy and Clean Air (CREA) has found that thermal power plants in the national capital region (NCR) emit 16 times more air pollutants than stubble burning. “…Thermal power plants in NCR emit 16 times the 17.8 kilotonnes released from burning 8.9 million tonnes of paddy straw,” the CREA study stated.

This finding comes as Delhi's air quality worsened further on November 17, reaching an AQI of 441, making it the second-most polluted city in the country. The city's 24-hour Air Quality Index (AQI), recorded at 4 pm daily, stood at 441, in the "severe" category. On Saturday, the AQI was 417.

According to the Central Pollution Control Board (CPCB), a "severe" AQI poses risks to healthy individuals and severely impacts those with pre-existing health conditions.

According to CREA estimates, 281 kilotonnes of sulphur dioxide (SO₂) were released by coal-fired thermal power plants in NCR between June 2022 and May 2023.

Notably, India is currently the world’s largest SO₂ emitter, responsible for over 20% of global anthropogenic SO₂ emissions, primarily due to its coal-dependent energy sector. India’s SO₂ emissions from electricity generation were measured at 6,807 kilotonnes in 2023, surpassing emissions from other major emitters like Turkey (2,206 kilotonnes) and Indonesia (2,017 kilotonnes).

“A comparison between NCR thermal power plant emissions and paddy straw burning emissions in Punjab and Haryana highlights the scale of SO₂ pollution. Thermal power plants in NCR emit 281 kilotonnes of SO₂ annually—16 times more than the 17.8 kilotonnes emitted by burning 8.9 million tonnes of paddy straw,” the study found.

“While paddy straw burning causes seasonal spikes, thermal power plants represent a larger, persistent pollution source year-round, underscoring the need for stricter controls on thermal power plant emissions. Yet, thermal power plants often receive leniency and repeated compliance extensions, especially for installing FGDs, whereas stubble burning is heavily penalized, with strict enforcement on farmers during the burning season,” it added.

Accelerated adoption of the flue gas desulfurization (FGD) technology would reduce emissions to 93 kilotonnes in the NCR, representing reductions of 67 percent, the CREA study found.

“Over 96 percent of particulate pollution from coal-fired power plants in the NCR is secondary in nature, primarily originating from SO₂. Reducing SO₂ emissions can significantly decrease the secondary particulate matter load, thereby reducing the health risks associated with prolonged exposure to these particles,” said Manoj Kumar, Analyst, CREA.

“SO₂ levels often meet the NAAQS because, once released, it quickly transforms into sulfates—secondary particles that are major components of PM2.5. These secondary particles have a longer lifetime and pose serious health risks. This hidden transformation of SO₂ into harmful particles emphasises the necessity for FGD installation,” he added.

However, according to the Centre's Decision Support System for Air Quality Management, vehicular emissions contributed approximately 15.8 percent to Delhi's pollution on Sunday. The system also reported that stubble burning was the main contributor to the capital's air pollution on Saturday, accounting for 25 percent of the total pollution.

Meanwhile, the prominent pollutant was PM2.5, according to the CPCB. PM2.5 refers to fine particles with a diameter of 2.5 micrometres or less, about the width of a human hair. These particles are so small that they can penetrate deep into the lungs and even enter the bloodstream, posing significant health risks.

(With agency inputs)