RESUMO
The widespread adoption and sustained use of modern cookstoves has the potential to reduce harmful effects to climate, health, and the well-being of approximately one-third of the world's population that currently rely on biomass fuel for cooking and heating. In an effort to understand and develop cleaner burning and more efficient cookstoves, 15 stove design and fuel/loading combinations were evaluated in the laboratory using the International Workshop Agreement's five-tiered (0-4) rating system for fuel use and emissions. The designs evaluated include rocket-type combustion chamber models including reduced firepower, sunken pots, and chimneys (three stoves); gasifier-type combustion chambers using prepared fuels in the form of wood pellets (four stoves); forced draft stoves with a small electric fan (five stoves); and a single insulated charcoal stove with preheated secondary air. It was found that a charcoal burning stove was the only stove to meet all the Tier 4 levels of performance. Achieving over 40% thermal efficiency at high power was made possible by reducing firepower and gaps around the pot, although batch-fed stoves generally do not "turn down" for optimal low power performance. While all stoves met Tier 4 for carbon monoxide, only stoves equipped with electrical fans reduced respirable particulate matter to Tier 4 levels. Finally, stoves with chimneys and integrated pots were fuel efficient and virtually eliminated indoor emissions. It is hoped that these design techniques will be useful in further development and evolution of high-performance cookstove designs.