Changing the way food is cooked in households across South Asia could help tackle climate change, according to a study published in the latest edition of Science.
The research shows that 'biofuels' such as wood, agricultural waste and dried animal manure, which are widely used in the region, are a significant source of pollution in the form of soot.
Soot particles absorb light, leading to increased temperatures in the atmosphere and decreased temperatures on land. These changes could have profound impacts on rainfall patterns, potentially making floods and droughts more intense.
The study's authors, led by C. Venkataram of the Indian Institute of Technology in Mumbai, say that efforts to address climate change should therefore focus on controlling biofuel use by introducing cleaner technologies.
The researchers used laboratory tests to estimate how much soot 11 types of biofuel emit when burnt in traditional one-pot stoves, which are thought to account for at least 80 per cent of stove use in India.
They estimated that biofuels contribute 42 per cent of India's total soot emissions, while open burning (such as forest fires) produced 33 per cent and use of fossil fuels produced 25 per cent.
The large quantities of soot produced by household stoves, especially those using wood, could have a negative impact on the atmosphere, particularly given the extensive use of biofuels in India, says the study.
It notes that airborne pollution such as soot could have important implications for agriculture and the economy by altering rainfall patterns.
Using cleaner fuels, such as liquid petroleum gas or kerosene, would be the best solution to reduce soot emissions, say the researchers, but these alternatives are more expensive than biofuels and less accessible to poor households.
"Above all, this not an attempt to blame the developing countries for polluting the world," Kirk Smith, professor of environmental health sciences at the University of California, Berkeley, United States, told SciDev.Net. "Developed nations are still responsible for the majority of greenhouse gas production."
Tackling the problem of burning solid biofuels would be a win-win situation because of the combined health and environmental benefits that would result from reducing soot emissions, says Smith.
According to the Intermediate Technology Development Group, indoor pollution caused by burning biofuels affects the health of hundreds of millions of people, and kills more children each year than malaria or HIV/AIDS. Among the diseases linked to stove use are pneumonia, lung cancer and respiratory tract infections.
The problem is exacerbated by the poor quality of stoves, says the organisation, which estimates that the number of people relying on polluting fuels for cooking will increase by 200 million to 2.6 billion people by 2030.
Venkataram and colleagues say their findings could also apply to other parts of Asia, as well as Africa, Asia and South America, where residential use of biofuels is also prevalent.
Reference: Science 307, 1454 (2005)