Wood pellets are densified biofuel made from woody biomass with or without additives usually with a cylindrical form, random length typically 5 to 40 mm and diameter up to 25 mm (6 mm and 8 mm are the most common diameter) and broken ends.
Wood pellets have standardised characteristics in terms of size, composition, calorific value, ash rate, etc. They can be used in household stoves or industrial/municipal boilers suitable for the production of heat and/or power.
Wood pellets are mainly produced in Europe from by-products of wood related industries, being mainly sawdust or white wood chips. The first step of producing pellets is to turn raw materials into a ground product. This wood powder is then dried and compressed into a more dense and coherent material. The wood pellets are finally sieved and cooled down.
No chemical additive is used (natural additives as starch might be used in limited quantity), the cohesion is ensured by the natural binders of the biomass.
The densification of wood makes it possible to increase the energy content of the fuel per unit volume, thus making its transport and storage more efficient. The densification process also has the advantage of converting a relatively heterogeneous fuel into a homogeneous and standardised product allowing complete automation of the energy production installations.