Wood-fueled cooking stoves are commonly used in Central America and other Third World nations. Producing copious amounts of noxious smoke, the stoves can be detrimental to human health. Lack of knowledge about the characteristics and quantities of emissions from millions of these modified campfires is a major contributor to uncertainties in global emission inventories of particulate matter.
To improve the measurement and characterization of emissions from wood-fueled cookstoves, researchers at the University of Illinois at Urbana-Champaign have designed and built a portable, battery-operated sampling cart. The inexpensive and mobile monitoring system can be taken to remote locations to better evaluate emission sources.
"We have established working relationships with non-profit organizations in the United States and in developing countries that afford us access to ongoing measurements of both traditional and improved wood-burning cookstoves," said Tami Bond, a professor of civil and environmental engineering. "These partnerships form the foundation for achieving a positive impact on both human health and the environment."
In the past, field measurements were difficult to obtain for many reasons, including limited access to remote sites and the lack of power to operate equipment. While cooking fires have been replicated and measured in laboratory settings, the results may not represent actual cooking practices.
"To be accurate, we really need to measure while food is being cooked," said graduate student Christoph Roden. "We need to record how much fuel is consumed, and we need to examine the type, size and condition of the wood that is burned."
The sampling cart carries sensors for measuring carbon dioxide and carbon monoxide, a particle soot absorption photometer for measuring particle color, a nephelometer for measuring particle concentration, and two filters for collecting particles for later analysis. A battery-operated power supply and data-acquisition system complete the design.
In collaboration with two nonprofit agencies -- Trees, Water and People (based in the United States) and AHDESA (the Honduran Association for Development) -- Bond and Roden took their sampling cart to Honduras, where for two weeks they measured emissions from a number of traditional cookstoves. The researchers are now comparing their field measurements with previous laboratory studies, and examining the implications upon human health and global climate modeling.
"Scientists have been assuming certain properties of particles based on testing performed in laboratories," Roden said. "We are finding, however, that the properties really depend upon the conditions under which the wood is burned, and those properties in turn affect the climate differently."
Particle characteristics depend, for example, upon whether the fire is flaming or smoldering. Wood size also makes a big difference. Because larger pieces don't heat up as fast, more volatile material can be released over longer periods. The bottom line, Roden said, is that not much testing has been performed on the kinds of traditional technology that emit most of the particles in the atmosphere. Much more work needs to be done.
"This was a pilot program and provided a baseline study on emissions," Bond said. "Improved, fuel-efficient and pollutant-reducing cookstoves have been developed and are being distributed throughout villages in Honduras by the nonprofits that we work with. We will return next summer to measure and compare the emissions from the new stoves."
The researchers described their sampling cart and presented early results at the American Geophysical Union meeting in San Francisco.
Funding was provided by the National Science Foundation and the Partnership for Clean Indoor Air.