Efficiencies and pollutant emissions from forced-draft biomass-pellet semi-gasifier stoves: Comparison of International and Chinese water boiling test protocols

Abstract

Biomass fuels are widely combusted in rural China, producing numerous air pollutants with great adverse impacts on human health. Some improved cookstoves and pellet fuels have been promoted. To evaluate the performance of pellet-gasifier stoves, efficiencies and pollutant emissions were measured following International and Chinese water boiling tests (WBTs). Compared with traditional stoves and unprocessed biomass fuels, increased efficiencies and lower emissions of pollutants including carbon monoxide (CO), particulate matter (PM), parent and derivative polycyclic aromatic hydrocarbons (PAHs) were revealed for pellet-gasifier stoves. However, the calculated emission rates (ERs) of CO and PM2.5 cannot meet the ER targets recently suggested by WHO indoor air quality guidelines (IAQGs). Better control of air mixing ratio and gross flow rates of primary and secondary air supply greatly reduced emissions and increased efficiencies. Differences among testing protocols are the key factors affecting the evaluation of stove performance. With longer burning duration and higher power, the Chinese WBT had statistically higher efficiencies, gas temperature, and lower pollutant emissions (p<0.10) compared to those obtained through the International WBT. Statistically significant differences between the two protocols indicate the need for further efforts in emission tests and methodology development before the release of a well-accepted international testing protocol.