Particulate and gaseous emissions from different wood fuels during combustion in a small-scale biomass heating system

Abstract Woodchip is widely used as fuel in dedicated biomass and, even in some conventional energy generation plants. However, there are concerns about atmospheric air pollution from flue gases emitted during wood biomass combustion, particularly oxides of nitrogen (NO x ) and particulates X and PM10 of 150 and 30 g per gigajoule (g/GJ) of energy input, respectively. In an experiment, three locally available types of Willow ( Salix spp) and one of Sitka spruce ( Picea sitchensis ) woodchips, showed significant differences in physical and chemical constituents, gaseous and particulate emissions. During combustion in a 120 kW biomass system, air flows, flue gas temperatures and energy output correlated with gaseous emissions, NO x with raw fuel ash, nitrogen, phosphorus and potassium content, as did all flue gas particulate fractions. PM10 ranged from 30.3 to 105.7 g/GJ and NO x from 91.2 to 174.3 g/GJ. Sitka spruce produced significantly lower emissions of PM10 and NO x (27.5 and 52.6% less, respectively) than the three willow fuels, from which emissions were above the RHI emissions limits.