Formation of new particles from a cross-section of biomass cookstoves and their global radiative impacts

Recent advances in aerosol instrumentation have facilitated the discovery of so-called nanocluster aerosols in emissions from combustion sources. These are distinct from new particles formed in the atmosphere from secondary processes and have recently been shown to dominate the sub-10 nm particle burden in urban environments. In this work, we investigated particle emissions from five different cookstove technologies that span the range from a dirty to a clean cookstove: 3-stone fire, rocket elbow, charcoal, gasifier, and liquified petroleum gas (LPG). A water boil test, commonly used in cookstove studies, was performed for all cookstoves that included a cold start, hot start, and simmer test. The cold and hot starts involved heating 5 kg of water from room temperature to 90 ℃ and the simmer test involved keeping the water temperature at 90 °C for 45 minutes. Emissions were measured using a scanning mobility particle sizer (for particles larger than 10 nm) and an Airmodus A11-nCNC system (for particles larger than 1.3 nm). For all cookstoves, the sub-10 nm particles outnumbered the super-10 nm particles by more than an order of magnitude, indicating the presence of a large number of primary sub-10 nm particles. Since we did not measure the chemical composition, it is unclear how these particles were formed and whether these particles were composed of sulfuric acid, organic compounds, or both. These primary sub-10 nm particles had emissions that ranged between ~10 ¹⁵ # kg-fuel ^-1 for the LPG to ~3×10 ¹⁶ # kg-fuel ^-1 for the charcoal stove. Our emissions estimates were similar to those for sub-3 nm particles measured from engine exhaust (e.g., diesel engine, natural gas turbine) and on and near roadways in Europe. The cookstove results point to the ubiquity of sub-10 nm particle emissions from combustion sources and highlight the urgency of explicitly including them in atmospheric models. Ongoing work is focused on developing global emissions inventories for sub-10 nm particles, which will be used to determine their influence on the global distribution of particle number concentrations using the GEOS-Chem model (a global chemical transport model). Model results will be analyzed offline to investigate the potential role of these sub-10 nm particles on direct and indirect radiative effects.