Wildfire Emissions From European Boreal Fuels: Effects of Fuel Type and Moisture Content

The increasing severity of wildfires poses significant challenges through the release of greenhouse gases and other harmful gases and particles. Although field measurements exist, there is a lack of systematic data collection to understand the influence of moisture content on the particle and gas emissions of boreal fuels, particularly for European boreal forest fuels. This study investigates the influence of moisture content and fuel type on flaming combustion emission characteristics of surface fuels collected from two Swedish forest types, which share key characteristics with fire‐prone forests across the European boreal. The results are based on bench‐scale controlled combustion conditions in a cone calorimeter, where gaseous and particle emissions were measured using Fourier Transform Infrared spectroscopy and an Electrical Low‐Pressure Impactor, respectively. Moisture content of the fuels only insignificantly affected combustion efficiency, with higher moisture content leading to increased emissions of incomplete combustion products (CO, CH 4 and NH 3 ). Thus, although moisture affects the amount of fine fuel consumed in a wildfire, it is not significant for the emissions factors during the flaming combustion. The combustion of mosses was instead significantly less efficient than that of litter for all moisture contents. Average emission factors highlighted clear differences between fuel types, with mosses producing higher CO (87 ± 20 g/kg) and lower CO 2 (1350 ± 220 g/kg) compared to litter (47 ± 12 g/kg and 1620 ± 81 g/kg, respectively). Particle emissions were strongly dependent on fuel type with of 29 ± 12 g/kg for mosses compared to 98 ± 15 g/kg for Pinus sylvestris needles and twigs.