The utilization of biomass for energy production is an attractive option for power producers to reduce their CO2 emissions. Because of its porous structure the wood has a low density. One solution to that problem is the densification of biomass materials into pellets. Densification of biomass materials increases the bulk density of biomass and could reduce the costs of transportation; storage, handling, and results in less pollution, lower amount of fine fraction and controlled combustion process. The aim of the thesis was to obtain an overview of the physical properties and chemical compounds in wood pellets produced by seven selected producers in Slovenia. The results obtained were compared with the values specified in the national standard for wood pellet SIST EN ISO 17225-2. Softwoods have a higher content of lignin than hardwoods and therefore pellets made from softwoods have a better mechanical durability than pellets made from hardwoods. Producer E was the only one, which used raw material with a greater proportion of hardwoods than softwoods. This had the lowest mechanical durability of the pellets. Softwoods have a high calorific value than hardwoods. The highest gross calorific value for a dry sample of pellets was measured at producer C. Producer C produces pellets only from pine. The lowest gross calorific value for a dry sample of
pellets was measured at the producer E. They used for pellet production 70 % of hardwoods. Producer G, which had the highest content of bark in pellets, had the second highest calorific value for dry samples of pellets. The net calorific value for a sample of pellets as received is most affected by moisture content. Therefore, the lowest average net calorific value for samples of pellets as received was measured in pellets from producer D, which had the highest average moisture content in pellets. The highest nitrogen content was measured in pellets from manufacturer G, which produced pellets with bark. Bark has a higher content of nitrogen compared to wood. Bark content, content of lignin and extractives, moisture and particle size distribution are an important influencer of pellet durability. With the particle size distribution in the raw material we could only partially evaluate the influence on mechanical durability of pellets
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