The energy performance and emissions (carbon monoxide and total suspended particulate matter) of a biomass gasification-based cookstove under a modified water boiling test (WBT 4.2.3 protocol) were characterized here. The controllable process parameters analyzed were the biomass bulk density (pellets─WP and chips─WCH) and the combustion-air/gasification-air ratio (2.8, 3.0, and 3.2). Moreover, a design parameter of the cookstove was analyzed through two combustion chamber designs (combustion chambers 1 and 2). The cookstove was characterized in detail considering the complete cookstove (control volume 1), the combustion chamber (control volume 2), and the gasification process (control volume 3). The cookstove reached an average efficiency of 25.2% for pellets and 24.1% for chips. The best behavior for the cookstove was achieved when pellets were used, which is attributed to their higher bulk density and to the fact that during their gasification process, the biochar yield was 12% higher, while the biomass consumption decreased by 16% compared to the chips. The carbon monoxide specific emissions were 2.78 g/MJ_d for pellets and 2.75 g/MJ_d for chips. On average, the cookstove released total suspended particulate matter between 74.11 and 122.70 mg/MJ_d. The cookstove low emissions are ascribed to the proper combustion air flow and the combustion chamber design, which favored the mixing between producer gas and combustion air.

The fallen leaf has the potential to be energy-valorized in cities with sustainability goals. Thermochemical characterization of garden waste through pyrolysis and combustion kinetics will establish the reactivity of this lignocellulosic biomass as biofuel for thermochemical conversion processes for energy recovery. Herein, the thermal degradation of two types of pellets produced from fallen leaf (pellets without glycerol PG0, and pellets with 5 wt% glycerol PG5) are characterized under inert and oxidative atmospheres using three different approaches: thermogravimetry (TG) and differential thermogravimetry (DTG) analyses, TG-based reactivity, and reaction kinetics from three model-free isoconversional methods. The model-free isoconversional methods are Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Friedman, which were applied for estimating the kinetic parameters, activation energy (Eα) and pre-exponential factor, using different heating rates (20, 30, and 40 °C/min) to ensure reliable data interpretation. The pyrolysis results showed that PG5 was more reactive compared to PG0 because the addition of glycerol during the pelletizing process increased the volatile matter and oxygen content in PG5. Likewise, the higher reactivity of PG5 under pyrolysis was determined by average activation energy (Eα) with an average value of 96.82 kJ/mol compared to 106.46 kJ/mol for PG0. During the combustion process, Eα was 90.70 kJ/mol and 90.29 kJ/mol for PG0 and PG5, respectively. Finally, both materials exhibited higher reactivity under an oxidative atmosphere. Therefore, according to our results, the pellets produced from leaf litter can be used as biofuels for thermochemical processes, highlighting that using glycerol as a binder favors the reactivity of the densified garden waste.

Biomass is commonly used for cooking in developing countries, but traditional cookstoves emit pollutants (CO, NO_x, 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/MJ_d, and efficiency between 26.56% and 27.81%. TSPM emissions ranged between ~74 and 122.70 mg/MJ_d. 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.

En este trabajo se presenta un estudio de repetibilidad aplicado a una estufa de cocción basada en gasificación de pellets de madera (19.03 MJ/kg). El análisis es llevado a cabo mediante un protocolo de ebullición de agua (Water Boling Test, WBT 4.2.3) modificado. La repetibilidad de la estufa basada en gasificación se evaluó mediante 2 metodologías: coeficiente de variación (CV, %) y análisis de varianza (ANOVA), en función de variables respuesta, tales como eficiencia térmica ( , %), potencia (P, kW), consumo de combustible (FC, g/min), consumo específico de combustible (SFC, g/L), consumo específico de energía (SFEC, kJ/L) y consumo específico de energía por unidad de tiempo (SFCT, kJ/L-min). Mediante el análisis de CV se obtuvo un CV promedio global de 4.69% ± 0.87%. Por tanto, como el CV ≤ 5%, se concluye que la estufa de cocción basada en gasificación es repetible. Con respecto al análisis ANOVA, los valores P de las variables estudiadas fueron mayores a 0.05 (P>0.05), por lo tanto, se concluye que la estufa de gasificación es repetible con un nivel de confianza del 95%. Consecuentemente, se concluye la eficiencia térmica promedio alcanzada por la estufa es del ~29% ± 2.25%, con un nivel de confianza del 95%. Este valor de eficiencia térmica es comparable con otras estufas de cocción basadas en gasificación reportadas en la literatura con valores entre 16 y 38%. La metodología y los resultados de este trabajo constituyen una base teórica para la evaluación de futuros desarrollos de estufas de cocción a biomasa, ya que se puede cuantificar y analizar la confiabilidad de los resultados encontrados en los prototipos probados a nivel de laboratorio.