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Globally, 3 billion people rely on solid biomass fuel for their everyday cooking, most often using inefficient cooking practices, leading to high exposure levels of household air pollution. This is subsequently associated with negative health and climate impact. Further, the inefficient use of biomass fuels applies pressure on natural forests, resulting in deforestation, loss of biodiversity, and soil degradation. Improved cookstove technologies and biomass fuels are being promoted to mitigate these issues. However, limited knowledge exists about how the interaction between stove technology and new fuels affects the physical and chemical properties of particulate emissions. In this study, the emission performance of four cookstove technologies in combination with five fuels was evaluated in a laboratory setup, applying a modified water boiling test with a hood dilution system for flue gas sampling. Filter sampling was applied to determine the emissions of fine particulate matter (PM₁) and for subsequent analysis of polycyclic aromatic compounds (PAC), organic- and elemental carbon, and inorganic composition. Particle mass size distribution was determined by using a 13-stage low-pressure cascade impactor. Online instruments were used to determine gaseous emissions (e.g., CO, CH₄, and BTX) as well as particle number size distribution. The results show that both the stove design and fuel properties influence the total emissions as well as the physiochemical PM characteristics. It was further seen that the impact of fuel on the PM properties did not translate linearly among the different stove technologies. This implies that each stove should be tested with various fuels to determine both the total emissions and fuel suitability.

Around one-fourth of the global population lacks access to clean fuels and technologies for cooking, most of them living in low- and middle-income countries. Reliance on rudimentary and inefficient biomass cookstoves results in high pollutant concentrations that adversely affect the health of those exposed to indoor air pollution, the environment, and the climate. In this study, we systematically reviewed the literature on aerosol and particle properties from biomass cookstoves of relevance to health, climate and the environment. We identified 187 articles reporting aerosol characterization (i.e. particulate mass or number concentrations, or particle size distributions). Of these, 82 presented detailed particle characterization (e.g. chemical composition), thus selected for further analysis. Articles were classified based on the reported particle properties and the study type and location, which allowed mapping research efforts to date and identifying major knowledge gaps. Most reviewed studies (39 articles) on particle properties reported particulate organic and elemental carbon composition. Despite considerable variability, the EC/TC ratio generally varied in the range of 0.1-0.4 for all cookstove technologies, indicating that organic carbon is the dominating PM fraction in biomass cookstove emissions. Findings from this systematic review highlight the need for further studies on particle properties from biomass cookstoves that use a multidimensional approach simultaneously combining several properties and different cookstove-fuel combinations. We also assessed the policy landscape, including the three main global policies concerning biomass cookstove emissions, and evaluated whether those policies included the state of the knowledge on particle properties and their adverse effects on human health, climate, and the environment. We finally identify key aspects that future policies should integrate, and critical knowledge gaps that must be filled to advance the overall development of the field. Notable was that field studies consistently report particle emission factors (PM_2.5) higher than the ones determined under laboratory conditions, for example, an average of 8.9 g/kg_fuel (field) compared to 5.2 g/kg_fuel (lab) for traditional cookstoves and 4.0 g/kg_fuel (field) compared to 1.3 g/kg_fuel (lab) for advanced cookstoves. Cookstove manufacturers, practitioners, policymakers, and society in general will benefit from a solid knowledge base regarding particle properties from biomass cookstoves and their related adverse effects on human health, climate, and the environment.

Around 2.3 billion people lack access to clean cooking solutions worldwide. In sub-SaharanAfrica, over 80% of the population relies on rudimentary, low-efficiency, and highly pollutingcooking appliances. This study presents in-depth field data collected in rural Rwanda oncombustion and emission performance from four biomass cookstoves fueled with locally andsustainably produced woody biomass. The study builds on pairwise cookstove combinations,with two cookstoves tested in each of the six households included in the study.Our results show that the rocket stove and the two natural-draft gasifiers required less fuel tocook the same recipe. The cooking time was slightly increased for the natural draft gasifierscompared to the three-stone fire. Biochar yield ranged from 143-457 g/cooking event, with themost producing cookstoves being the gasifiers and 3-stone fine and the rocket stoves. Carbonmonoxide (CO) concentrations averaged up to around 180 ppm with peaks of up to 400 ppmwhen cooking with the three-stone fire. On the contrary, the lowest CO concentrations wereobserved when using the industry-manufactured gasifier, ranging from 7 to 14 ppm. AveragePM1 and particle number (PN) concentrations followed similar trends of reducedconcentrations along the technological gradient, except for the artisan-manufactured gasifier,which performed worse than the less technologically advanced rocket stove for bothparameters.We used a portable Scanning Mobility Particle Sizer (SMPS) to determine particle numberconcentrations and size distributions. The analysis showed that particle numberconcentrations were significantly higher for the 3-stone fire than for the other three studiedcookstoves. The analysis also shows that particle size distributions varied over time for all thecookstoves. In all cases, particle size distributions peaked around 80-100 nm, varying overtime during cooking events. Regarding specific particle properties, our study shows that,despite all the cooking events being performed with the same fuel, the particle propertieschanged considerably between cookstoves. We also show that improved cookstoves generatelower black and brown carbon (BC and BrC) emissions. The results show a significant CO,PM1, BC and BrC emission reduction from improved cookstoves compared to the three-stonefire. On the contrary, particle size distributions from artisan-manufactured gasifiers weresimilar to those from the three-stone fire. In addition, the detailed and source-specificinformation provided in this study will benefit cookstove manufacturers, modelers, andpolicymakers.Conclusively, improved cookstoves have a vast potential for reducing fuel consumption andemissions compared to the three-stone fire. This study provides valuable and comprehensivefield-based data on combustion and emission performances and aerosol and particleproperties.

Most people in rural sub-Saharan Africa lack access to electricity and rely on traditional, inefficient, and polluting cooking solutions that have adverse impacts on both human health and the environment. Here, we propose a novel integrated agroforestry-bioenergy system that combines sustainable biomass production in sequential agroforestry systems with biomass-based cleaner cooking solutions and rural electricity production in small-scale combined heat and power plants and estimate the biophysical system outcomes. Despite conservative assumptions, we demonstrate that on-farm biomass production can cover the household’s fuelwood demand for cooking and still generate a surplus of woody biomass for electricity production via gasification. Agroforestry and biochar soil amendments should increase agricultural productivity and food security. In addition to enhanced energy security, the proposed system should also contribute to improving cooking conditions and health, enhancing soil fertility and food security, climate change mitigation, gender equality, and rural poverty reduction.