According to a study the way families in developing countries use their cook stoves has a huge impact on emissions from them, and laboratory emission tests don't precisely reflect real-world operations.
Biomass-burning cook stoves are used all over the developing world, which uses wood, agricultural waste and other organic matter as fuel.
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Policymakers and nonprofit organizations are working to develop and distribute 'improved' cook stoves, for example, addition of insulation or chimneys to reduce emissions.
They are especially concerned with fine particles that are released, which cause health problems and also affect climate.
Just like automobiles undergo emission testing before hitting the market, cook stoves are also tested in the lab before distribution to measure how effective improvements are at reducing emissions.
But if the conditions aren't the same as to how people use them at home, then the modifications that designers make to the stove may not actually reduce emissions in the field.
"The understanding of how people really use combustion devices is important if we're going to optimize that device," said study leader Tami Bond, a professor of civil and environmental engineering at University of Illinois.
"In the laboratory, where tests are conducted by trained people, there's a lot more attention to operating the stove carefully. At home, people are not as concerned with its operation; they're more concerned with making a meal. So they operate in ways that are non-optimal," said Dr. Bond.
However, these differences in use are masked by the current methods of testing, which use only average values to determine emissions - sort of like a snapshot of the stove in operation, not accounting for variation in use.
Bond's team developed a real-time analysis technique called 'Patterns of Real-Time Emissions Data (PaRTED)', which allows researchers to compare emissions under different operating conditions and to gauge how often a stove operates under certain conditions in the field.
"Wood burning is like a dance," Bond said.
"A movie gives you a better understanding than a photograph. This is a way to make movies of how users change as they make fires, and that can help people understand emission rates and make better stoves," he said.
Bond's team tested cook stoves, using PaRTED, in use in a village in Honduras and compared the field results to lab results.
The team found that operation under less-than-ideal conditions produces the highest emissions.
They also discovered that in the field, stoves are rarely used under optimal conditions, a scenario not reproduced in laboratory tests.
The team did a comparative analysis of the emission profiles, or the chemical makeup of the smoke, from traditional cook stoves and two types of improved stoves: insulated stoves and stoves with chimneys.
They found that although stoves with an insulated combustion chamber could add to overall efficiency, they did not significantly reduce emissions per mass of fuel burned. himneys did reduce certain types of particle emissions - but chimneys did not cut down on black particles, the type most harmful to climate.
"Our measurements confirm that changes in stove design cause a change in the way they operate," Bond said. I think people weren't aware that changes in design actually change the profile of the emissions rather than just reducing emissions," he said.
Next, the researchers will use PaRTED analysis to study variations in cook stove usage in other regions of the world.
Bond hopes that PaRTED and this study will inform future testing protocols for cook stoves in the lab, allowing researchers to more accurately test under realistic conditions and providing insight into a whole range of possible use scenarios.
"Insulated and chimneyed stoves are a step in the right direction, but not as far as we need to go to get really clean stoves," Bond said.
"The next step is to identify both the patterns of stove operation and the factors that lead to the characteristic profile of operation so that those can be brought into the lab and optimized. The cook stove world is moving toward having emission standards. It would be best if those standards were relevant to real operations," he added.
This study has been published in the journal Environmental Science and Technology.