The use of cow dung as cooking fuel in India releases disproportionately large quantities of air pollution, according to new research. The findings of the work suggest a major need in the country to phase out biofuel use in rural homes, which could help mitigate air pollution–related public health impacts.
Millions of Indians use cow dung as their primary cooking fuel, including in the densely populated Indo-Gangetic Plain in the country’s north. But cow dung–fired stoves are highly polluting, according to the analysis by researchers at the Indian Institute of Science Education and Research (IISER) Mohali.
“These solid fuels don’t burn cleanly, and as a result there’s a lot of smoke.”
“These solid fuels don’t burn cleanly, and as a result there’s a lot of smoke,” said Baerbel Sinha, an environmental scientist and study coauthor at IISER Mohali. “If we want to get a handle on the air pollution crisis, the Indo-Gangetic Plain is a high priority,” she added.
The team will present its research at AGU’s Annual Meeting 2024.
Emissions and Exposure
Sinha and her team inventoried emissions estimates in India for cow dung stoves, as well as for other types of residential solid fuel usage, such as liquefied petroleum gas, kerosene, wood, and agricultural materials, providing an on-the-ground dataset to complement satellite measurements of pollution. To assemble the inventory, they visited homes in the northern Indian state of Punjab to measure air pollution emissions in real time. They also incorporated nationwide petroleum sales data, fuel consumption statistics, and census data collected by government ministries as well as surveys of household cooking fuel use conducted between 2010 and 2020.
Emissions from cooking fuels emit particulate matter smaller than 2.5 micrometers (PM2.5) on average. Prolonged exposure to PM2.5 is linked to higher rates of respiratory disease, asthma, and other cardiovascular diseases, especially among young children, as well as to premature mortality.
Air pollution caused 1.67 million deaths (17.8% of all deaths) in India in 2019, of which 610,000 were attributed to household air pollution. Pollution exposures are high in low-income Indian communities because homes are often cramped and lack proper ventilation, noted Prithviraj Pramanik, cofounder of AQAI, a UNICEF-funded air pollution monitoring startup in India, who was not involved in the new research.
In their work, Sinha and her colleagues found that dung stoves emitted an estimated 1,600 gigagrams of PM2.5 in 2020, about half of all residential sector PM2.5 emissions and 17% more than was emitted by wood stoves (~1,370 gigagrams). However, less than 10% of Indian households used dung stoves that year, whereas more than 40% used wood stoves.
“The real reason why the dung emissions are so outrageous is that wood supplies greater than 5 times more cooking energy than dung” while still emitting substantially less pollution, said Sinha. “Dung, on the other hand, is used by a really small share of the population.”
Mitigating the Pollution Problem
India’s high air pollution rates have prompted the national government to act to mitigate polluting practices. In 2016, the government launched the nationwide Pradhan Mantri Ujjwala Yojana, a program designed to equip households to use liquefied petroleum gas—and to subsidize the gas itself—as a means of reducing pollution and boosting productivity.
But people still must purchase the gas cylinders, the price of which ranged, for example, from about 800 to 850 rupees (~$10) for 14 kilograms in the northern Indian state of Punjab as of April. Such costs are “a lot for many communities,” Pramanik said.
“People are making the types of economic choices that make sense to them.”
The government program did help to phase out kerosene and coal use from many households, according to the new research, but did little to reduce the use of biofuels, which are cheaper and more readily available. “People are making the types of economic choices that make sense to them,” said Pallavi Pant, an air pollution researcher at the Health Effects Institute in Boston who wasn’t involved in the work.
The study results suggest that substantial room for improvement exists to reduce emissions from biofuel use in homes and that “targeted mitigation approaches, aimed at cow dung users,” are an “attractive option for air quality improvement,” according to the researchers.
One potential approach, Sinha said, is to make use of infrastructure built to reduce air pollution from India’s agricultural sector. In Punjab, for example, the government has set up 10 compressed biogas facilities to convert crop residue into cleaner-burning methane. Farmers can receive the biogas in exchange for depositing agricultural waste, which they might otherwise just burn in their fields, thus reducing pollution and energy costs.
Sinha said she has urged the Punjab government to expand the biogas project by allowing people to bring cow dung to biogas facilities in exchange for gas cylinders. She said the scheme would incentivize people to replace polluting fuel with a cheaper and cleaner alternative.
—Tom Brown (@Journo_TomBrown), Science Writer
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