Characterization of gaseous and particulate pollutants from gasification-based improved cookstoves

Cookstove studies have reported pollutant concentrations (mainly PM2.5, black carbon and CO) without routinely associating it with the design and operating principles of the stoves. Extensive characterization of pollutants from cookstoves and the effect of different operating conditions are required for a better understanding of the mechanisms of pollutant formation. In this study, a forced draft (FD) and a natural draft (ND) gasification-based improved cookstove were tested under controlled conditions. Real-time pollutant concentrations, both particulate (PM2.5, lung-deposited surface area and particle number size distribution) and gaseous (CO, CO2 and NOx), from these stoves using three types of fuel (applewood chips and chunks, cowdung cake and coal) along with different cookstove operating conditions (airflow rates and with or without a cooking pot) were measured and compared. The FD cookstove tended to exhibit higher concentrations of emissions compared to the ND cookstove. Increasing airflow through the FD stove decreased flame length and the residence time of VOCs inside the flame zone, which in turn increased pollutant concentrations. An optimum airflow producing the lowest particulate matter (PM) concentrations was established for the FD cookstove. The CO-CO2 ratio, an indicator of combustion efficiency, demonstrated strong correlations with PM2.5 (r = 0.857), particle geometric mean diameter (r = 0.900) and the total surface area concentration (r = 0.908) indicating that CO-CO2 ratio may be used as a proxy for these PM metrics. Results reported in this study will facilitate further improvements in the design of future cookstoves.