Wood pellets are made from dried biomass that has been finely powdered and passed through a pellet dye at high temperature and pressure. The act of compression and the high temperature causes the lignin within the biomass to melt, gluing the particles together, which then re-form as a solid pellet after cooling.
The pellet manufacturing process is dependent on the raw material used but tends to include the following steps: reception of raw material, screening, grinding, drying, pelletizing, cooling, sifting, and packaging. The resulting product is a high-value, high-density pellet that is consistently shaped and thus more efficiently transported compared to woodchips. Wood pellets have a bulk density of up to 750 kg/m3 and a lower heating value of 16.5 GJ/ton.
As a comparison, woodchips have a bulk density of about 250 kg/m3 and energy content of 13 GJ/ton. There are strict specifications for a number of parameters designed to homogenize the combustion quality, safety, and feeding properties of wood pellets. The intensive pelleting process means that any fungal pathogens or insect pests are eliminated, and the material is considered sanitary for export and trade.