10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Characterizing Emissions from Diverse Domestic Biofuel Uses in Rural Malawi
ASHLEY BITTNER, Eric Lipsky, Mohammad Maksimul Islam, Andrew Grieshop, North Carolina State University
Abstract Number: 1623 Working Group: Combustion
Abstract Malawi is a low-income, energy-poor rural country in Southern Africa, where only ~7% of the population has electricity grid access. Consequently, the majority of household energy is provided by biofuel use, i.e. collected firewood and/or charcoal. Many of the common emission sources in Malawi and their respective emission factors are uncharacterized and unquantified, limiting understanding of air quality trends and impeding evaluation via atmospheric models. As an initial step, we identify various, diverse small-scale biomass burning activities (cooking/heating/bathing, charcoal making, brick burning, whiskey distillation, etc.) for emission characterization. We conduct village-level emission sampling using a portable Stove Emission Measurement System (STEMS). The STEMS measurement system records real-time measurements of carbon monoxide (CO), carbon dioxide (CO2), particulate matter (PM) scattering, black carbon (BC) absorption and integrated measurements of PM and organic carbon/elemental carbon (OC/EC).
In summer 2017, we monitored 2 charcoal ovens, 3 whiskey distillation events, and 20 cooking events [13 three-stone fires (TSF) and 7 improved clay cookstoves (ICS)]. We used the partial emissions capture approach for concentration measurements and the carbon balance method to estimate pollutant emission factors (EFs). Preliminary analysis of all cooking events shows an average CO EF of 104 g kg-1 and an average PM2.5 EF of 13 g kg-1 (calculated from Teflon filter measurements). On average, the improved cookstoves had lower CO and PM2.5 EFs (99 g kg-1 and 10 g kg-1, respectively) compared to traditional cookstoves (138 g kg-1 and 15 g kg-1 respectively). The cookstove pollutant EFs measured in this study are comparable to those measured in previous studies. Compared to the cooking events, CO EFs associated with charcoal making and whiskey distillation were considerably higher, 240 g kg-1 and 142 g kg-1 respectively. Charcoal making had the lowest measured PM2.5 EF (9 g kg-1), while whiskey distillation had the highest measured PM2.5 EF (19 g kg-1). Preliminary analysis of the real-time PM data suggests a similar average PM scattering EF for charcoal making and whiskey distillation (19 m2 kg-1 and 17 m2 kg-1, respectively). For comparison, the average PM scattering EF for the cooking events was slightly lower (14 m2 kg-1). The PM mass scattering cross-section (MSC) for charcoal was the highest (3.2 m2 g-1), and was found to be similar for whiskey distillation and cooking (1.0 m2 g-1 and 0.9 m2 g-1, respectively).
For future work, we will readdress the carbon balance assumptions, particularly for the less-studied emissions from charcoal making, and we will complete analysis of the remaining data collected during summer 2017 (BC absorption, OC/EC, modified combustion efficiency, etc.). In summer 2018, in addition to another round of emission sampling, we plan to use low-cost, low-power sensor packages (AriSense, Aerodyne Research) to conduct ‘fenceline’ monitoring of near-source, ambient conditions for comparison with the point source measurements made with the STEMS as an initial approach to characterization of biofuel burning emissions in Malawi.