Wood stoves used in developing world are big culprits in climate change

More than two billion people on this planet rely on raw biomass (firewood, crop residues, dung) for cooking and heating. Scientists have now found that stoves fuelled by this kind of biomass are contributing significantly more to climate change than expected. This makes the case for the introduction of modern bioenergy (biogas, biobriquettes, green gelfuel) all the stronger. Moreover, modern household biofuels also reduce indoor smoke pollution, a real killer in the kitchen that claims up to 1.6 million children and women's lives each year.

Researchers have found that smoke produced by these stoves, which are traditionally used for cooking and heating in developing countries, contains twice as many soot particles as laboratory experiments had previously indicated. When released into the atmosphere, the black, noxious particles — which are darker than those produced by grassland or forest fires — absorb light and increase atmospheric temperatures.

"They can absorb energy and keep it in the Earth's system when it would otherwise escape," says lead author Tami Bond of the University of Illinois at Urbana-Champaign, US. Lack of knowledge about the characteristics and quantities of emissions from wood stoves is a major contributor to uncertainties in global emission estimates for particulate material.

Bond and colleagues measured emissions from cooking stoves in Honduras using a portable monitoring system. In a previous study Bond had established that burning firewood produces 800,000 metric tons of soot worldwide a year:
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By comparison, diesel vehicles generate about 890,000 metric tons of soot a year. Both sources together contribute 10 per cent of the soot emitted annually into the atmosphere.

Distributing well-designed stoves with chimneys and training people in their use "may be an effective method of mitigating global climate change, and can improve the health of the users", says Christopher Roden, also of the University of Illinois at Urbana-Champaign and one of the study's authors.

However, the most effective way to reduce climate-warming particles, says Bond, would be replacing the wood with cleaner fuels. "These include liquefied petroleum gas, but also alternatives like biogas, managed charcoal and processed briquettes."

El Salvador, Guatemala, Honduras and Nicaragua are the main consumers of wood in Latin America, according to the World Conservation Union. In Honduras, more than 80 per cent of families cook over open wood fires.

The authors estimate that around 400 million wood stoves are used daily by more than 2 billion people worldwide. The study was published online last month (27 September) in Environmental Science & Technology.