Wood pellets are a type of solid fuel in the form of small cylindrical pieces produced from waste wood. The pellets are used as fuel, either in industrial or domestic heating systems specially designed for burning pellets. The use of pellet fuel in these units provides some advantages compared to other systems for solid fuels, namely: as the pellets are homogeneous mass of cylindrical pieces, their burning could be completely controlled. Burning under conditions for full control of the heating process saves energy, but also the burning of pellets leads to relatively small residues produced as a result of combustion. Pellets are made ??from both of coniferous and deciduous material. The result is a product with high caloric value. Due to the fact that the pellets are compressed sawdust in their natural state, there is no risk of producing solid residues during or after combustion in burners such as pellet stoves or boilers. Since the material they are made of is a scrap from other manufacture wood pellet production does not harm the environment. In a subsequent controlled harvesting and replanting of forests, the pellets are considered as a renewable source of energy.
In the process of production of pellets to the biomass is not required a further addition of chemical binders. Except from wood waste, sawdust, etc., pellets can be produced from raw wood, which is not applicable elsewhere. For the waste timber, used as a row material in wood pellets production, it is meant a material which cannot be applied in other industries. As stated above, these are wood bark and sawdust, branches, tops and scrap resulting from the primary processing of wood, curved trees, etc. The actual process of production of pellets include the following stages – coarsely wood grinding, drying, fine grinding, pressing, cooling and packing or storage, in case of use of dry wood it may be necessary some moisture to be pre-added to the wood.
The pellets were formed into a pellet press at high pressure and temperature. As a result of the applied pressure and heat the lignin in the timber melt at a temperature above 100%, thus allows the pellets to obtain a desired shape. The hot lignin acts as a binder for the final product. In the production of pellets of wood with a low content of lignin, some additives are applicable.