Particulate Matter Characteristics from a Gasification Cookstove: Implications of Operating Conditions Using Densified Wood Biomass

Biomass is commonly used for cooking in developing countries, but traditional cookstoves emit pollutants (CO, NOx, PM), which harm indoor air quality. Improvements and solutions are essential for achieving Sustainable Development Goal 7 (SDG 7). This study assesses the impact of the combustion chamber design, the combustion-air/gasification-air ratio (CA/GA = 2.8, 3.0, and 3.2), and the start type of water boiling test (WBT) protocol (cold and hot starts) on the chemical and morphological characteristics of the total suspended particulate matter (TSPM) emitted from a biomass gasification-based cookstove using densified biomass as feedstock. TSPM was characterized using Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, and Transmission Electron Microscopy (TEM) to evaluate their chemical composition and morphological features under the above operational conditions. Under the modified WBT protocol, the cookstove achieved CO levels ranging from 1.52 to 2.13 g/MJd, and efficiency between 26.56% and 27.81%. TSPM emissions ranged between ~74 and 122.70 mg/MJd. The chemical characteristics of TSPM surface functional groups weren’t affected by the start condition, except for decreased intensities as CA/GA increased, promoting oxidation and removal as CO/CO2. While cold start produced TSPM with higher structural order at higher CA/GA levels, no significant differences were observed among samples from both start conditions at CA/GA ≥ 3.0, indicating chemical and structural similarity. Morphology and particle size were mainly unaffected, with only slight increases in particle size during hot start due to higher biomass-to-air ratios.