Methane Emissions From Small Scale Appliances Burning Wood And Pellets

Four manually fed (6-11 kW) firewood burning and two automatic wood pellets (8.8-25 kW) residential heating appliances were tested under real-world operating conditions in order to determine methane emission factors (EFs). The results were examined for the influence of different factors (i.e., type of wood, appliance and combustion cycle). Differently from the standard emission testing methods, user habits were simulated in a schematic way in the laboratory employing different combustion cycles that represent a realistic user behavior. Five locally available firewood typeswere used for the feeding of manual appliances. Two types of pellets (i.e., low-quality higher ash, S-, and Cl-content pellets and high-quality pellets with DIN-PLUS certification) were selected for the experiments in the automatic stove and boiler. Methane emissions for the manually fed appliances ranged approx. between 1 g/kg to 10 g/kg. Depending on the appliance type the highest instantaneous emission factors coincided with different situations causing incomplete combustion and favoring the methane formation (e.g., starved air combustion at high temperatures characterizing the advanced stove or low temperature high excess air combustion in the closed fire place. A more complete combustion in the automatic pellet appliances brought to much lower emissions factors.