Stubble Burning Drives Nearly Half of Black Carbon Pollution in Rural Punjab, Study Finds

A new study by researchers from IIT Delhi has quantified how much crop-residue burning, also called stubble burning, contributes to black carbon pollution across North India's Indo-Gangetic Plain, including downwind cities such as Delhi. Despite a 2015 National Green Tribunal order aimed at preventing agricultural residue burning, the practice remains common in states including Punjab, Haryana, Uttar Pradesh, Delhi and Rajasthan.

Using a mobile monitoring lab equipped with an Aethalometer, a device that measures black carbon, at a field site in Kheral village in rural Punjab, the researchers found that crop-residue burning contributed an average of 48% of total black carbon during the post-monsoon period, and periodically exceeded 90% during active burning hours. The study, conducted during October and November, the peak season for crop-residue burning after the rice harvest, recorded an average black carbon concentration of 12.6 micrograms per cubic meter at the site, slightly lower than levels previously reported in Delhi (17.23 micrograms per cubic meter) and Agra (about 13 micrograms per cubic meter).

Two analysis models gave similar results. The Aethalometer model found biomass burning and fossil fuel burning contributed 48.5% and 51.5% of black carbon respectively. A more detailed Positive Matrix Factorisation model identified biomass burning as the largest single contributor at 48%, followed by power plant emissions at 24% and traffic emissions at 20.2%, with smaller shares from an industrial source and waste incineration. Using NOAA's HYSPLIT model, the researchers also confirmed that pollutants from the Punjab site travel and affect downwind areas across the Indo-Gangetic Plain.

Pratima Gupta, a postdoctoral researcher at the University of Lille who was not involved in the study, said the findings provide strong evidence that stubble burning can temporarily become a dominant source of local black carbon pollution, though she noted other studies have found lower contributions elsewhere: a 2024 study estimated stubble burning contributed between 15% and 37% of black carbon in Delhi across different months, while a 2025 study of the wider Indo-Gangetic Plain found household biofuel combustion was the dominant contributor at 58%, with stubble burning at just 3.5% in the post-monsoon period.