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Particle and gaseous emissions of a top-feed pellet stove were studied in laboratory conditions. Pellets made of separate stem and bark materials of five different wood species and a commercial pellet product were used as fuels. The study included the determination of the particle number concentration, size distribution, fineparticle mass (PM1.0), CO, CO 2 , NO x , and volatile organic compounds (VOC). The PM1.0 emission was analyzed for inorganic substances, organic carbon, and elemental carbon. Thermodynamic equilibrium calculations were performed to interpret the results from chemical analysis and to estimate the chemical composition of the PM1.0 mass emitted with various fuels. The bark fuels produced higher PM, VOC, and CO emissions than stem fuels. This was evidently related to the higher ash content of the bark fuels and was found to increase both the fly ash emission and the products of incomplete combustion. The fuel ash content correlated linearly with the PM1.0 emission. Among stem fuels, willow and alder produced higher PM1.0 emissions than birch, pine, spruce, and the commercial fuel. An exceptionally low PM1.0 emission was measured from pine bark combustion, which can be explained by the low ash content of the fuel. The main components in the PM1.0 were K 2 SO 4 , KCl, K 2 CO 3 , KOH, and organic material. Except birch fuels, around 60-80 mass % of potassium species were K 2 SO 4 based on the equilibrium calculations. In the case of birch fuels, because of the high chlorine content and low S/Cl ratios, around half of the potassium was KCl.

Abstract. Organic aerosols (OA) derived from small-scale wood combustion emissions are not well represented by current emissions inventories and models, although they contribute substantially to the atmospheric particulate matter (PM) levels. In this work, a 29 m3 smog chamber in the ILMARI facility of the University of Eastern Finland was utilized to investigate the formation of secondary organic aerosol (SOA) from a small-scale modern masonry heater commonly used in northern Europe. Emissions were oxidatively aged in the smog chamber for a variety of dark (i.e., O3 and NO3) and UV (i.e., OH) conditions, with OH concentration levels of (0.5–5)  ×  106 molecules cm−3, achieving equivalent atmospheric aging of up to 18 h. An aerosol mass spectrometer characterized the direct OA emissions and the SOA formed from the combustion of three wood species (birch, beech and spruce) using two ignition processes (fast ignition with a VOC-to-NOx ratio of 3 and slow ignition with a ratio of 5).Dark and UV aging increased the SOA mass fraction with average SOA productions 2.0 times the initial OA mass loadings. SOA enhancement was found to be higher for the slow ignition compared with fast ignition conditions. Positive matrix factorization (PMF) was used to separate SOA, primary organic aerosol (POA) and their subgroups from the total OA mass spectra. PMF analysis identified two POA and three SOA factors that correlated with the three major oxidizers: ozone, the nitrate radical and the OH radical. Organonitrates (ONs) were observed to be emitted directly from the wood combustion and additionally formed during oxidation via NO3 radicals (dark aging), suggesting small-scale wood combustion may be a significant ON source. POA was oxidized after the ozone addition, forming aged POA, and after 7 h of aging more than 75 % of the original POA was transformed. This process may involve evaporation and homogeneous gas-phase oxidation as well as heterogeneous oxidation of particulate organic matter. The results generally prove that logwood burning emissions are the subject of intensive chemical processing in the atmosphere, and the timescale for these transformations is relatively short, i.e., hours.

Emissions from the combustion of agricultural biomasses have not been studied extensively. In this study, the effects of different biomasses and mixed fuels on fine particle (PM1) and gas emissions from a residential cereal burner were investigated. The cereal seeds of oat and rape, rape bark pellets, and wood pellets were the main fuels. In addition, oat was mixed with peat and kaolin and wood with kaolin. The gas emissions of NO x , SO2, and HCl were clearly higher from cereal or mixed-cereal fuels than from pure wood fuel. The emissions of carbon monoxide (CO), organic gaseous carbon (OGC), PM1 and the particle numbers from the cereal fuels did not differ significantly from the emissions of wood fuels, although the fuel ash contents were substantially higher. The release of alkali metals varied substantially between different fuels, probably due to large differences in ash chemical compositions. In contrast to wood fuels, phosphate contributed significantly to the formation of fine particles in the cereal fuels. In rape fuels, probably due to high S/Cl and S/K ratios, all of the fuel chlorine was released in the gas phase and was not enriched in the fine particles. At least partly due to this, the PM1 and alkali metal emissions from the combustion of rape seeds were low, considering the high ash content (4.4%) and high alkali metal contents in the fuel. The addition of 5 wt % of kaolin to oat grains seemed to decrease the alkali metal emissions but slightly increased the emissions of incomplete combustion. It seems that the formation of chlorides (e.g., KCl) affects significantly the emission of fine ash particles. Moreover, sulfation of alkali metals seems to decrease the emission of fine alkali metal particles.

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