Fuel use and emissions performance of fifty cooking stoves in the laboratory and related benchmarks of performance

Abstract Improved cooking stove projects in the developing world have the potential to reduce deforestation, improve health, and slow climate change. To meet these requirements, stoves must be carefully designed through thorough testing and verification of performance. The systematic investigation of the heat transfer and combustion efficiency of stove design in the laboratory sheds light on what technologies work best and helps to ensure that stoves being disseminated are truly a significant improvement over traditional cooking methods. Performance of 50 different stove designs was investigated using the 2003 University of California-Berkeley (UCB) revised Water Boiling Test (WBT) Version 3.0 to compare the fuel use, carbon monoxide (CO) and particulate matter (PM) emissions produced. While these laboratory tests do not necessarily predict field performance for actual cooking, the elimination of variables such as fuel, tending, and moisture content, helps to isolate and compare the technical properties of stove design. Stoves tested fell under 7 main categories: simple stoves without combustion chambers, stoves with rocket-type combustion chambers, gasifier stoves, fan-assisted stoves, charcoal-burning stoves, liquid/gas fuel stoves, and wood-burning stoves with chimneys. A carefully made three-stone fire was also tested for comparison. Results showed that: • Stoves without well-designed combustion chambers may reduce fuel use in comparison to the three-stone fire but do not necessarily decrease and can potentially increase emissions of CO and PM. • Rocket-type stoves can reduce fuel use by 33%, CO emissions by 75%, and PM emissions by 46% on average in comparison to the three-stone fire. • Use of a pot skirt can reduce fuel use and emissions by 25–30%. • When operating well, gasifier stoves can reduce particulate matter substantially, averaging 90% improvement over the three-stone fire. • Five forced air stoves reduced fuel use by an average of 40% and emissions by 90% over the three-stone fire. • Traditional charcoal stoves use about the same amount of energy as the three-stone fire to complete a task (not counting the energy lost in making the charcoal, which can be as much as 70%) and produce up to two times more carbon monoxide and 80% less PM. A rocket-type charcoal stove can reduce this energy consumption by one third and CO emission by at least one half. • Liquid fuels generally exhibit less energy use and emissions. Kerosene can emit higher levels of PM than some improved wood stoves when not operating properly. • Well-designed stoves with chimneys remove smoke from the kitchen while fuel use is generally directly related to how much of the pot is in direct contact with the flames. From this data, it was possible to recommend benchmarks of improved cookstove performance. Benchmarks were suggested at levels that were achievable using known materials and manufacturing techniques, yet still aspirational, ensuring each stove design is carefully tested and optimized for highest efficiencies. It is hoped that these benchmarks can be used as the first step toward international performance standards for cooking stoves. Five of the stoves presented here were also tested at the US EPA, with results agreeing within 20% or better on all fuel and emissions measures, suggesting standard evaluation at various locations is possible.