Fuel Efficiency and Air Pollutant Concentrations of Wood-Burning Improved Cookstoves in Malawi: Implications for Scaling-up Cookstove Programs.

National governments and other key stakeholders in developing countries are grappling with how to reduce household air pollution (HAP) resulting from cooking with solid fuels using traditional cooking technologies. Recent studies have shown that improved cookstoves may offer reductions in fuel use and harmful emissions of carbon monoxide (CO) and fine particulate matter (PM2.5 ), yet there is little quantitative evidence collected in a "real-world" setting showing how improved stoves perform directly compared to traditional cooking technologies. Our simulated kitchen study takes place in a semi-controlled, "real-world" setting in Malawi and was designed to quantify the fuel efficiency improvements and air pollutant concentration reductions capabilities of two improved stoves currently marketed in the country. In this study, we perform a Water Boiling Test (WBT) to compare the air pollutant concentrations (CO and PM2.5 ) and fuel efficiency of the traditional three-stone fire stove and two improved cookstoves: a locally produced clay stove known as the Chitetezo Mbaula (CM) and a Philips gasifying stove. We find that the Chitetezo Mbaula uses 53% of the fuel used by the traditional three-stone fire, and produces 59% of CO, and 50% of PM2.5 of the three-stone fire. The Philips gasifying stove uses 31% of the fuel, and produces 38% of CO, and 22% of PM2.5 of the traditional three-stone fire. We consider the potential for the wide-scale adoption of each of these technologies given their relative costs and conclude that lower-cost, intermediate quality cookstoves are an important and realistic first step toward reducing household air pollution.