Wood chips are fragments of wood in the form of pieces with a defined particle size produced by mechanical treatment with sharp tools such as knives.
They can be obtained from different wood products: branches, trees unsuitable for sawing, parks and gardens residues, related products of sawmills, wood waste, short rotation coppices, etc. They can be used in domestic boilers but are mainly used in medium scale and in industrial boilers.
Traditionally we distinguish between several categories of woodchips depending on their composition and origin:
- White industrial wood chips come from the sawmill industry. They are normally devoid of barks, leaves, needles or twigs;
- Gray forest chips: they come either from the shredding of residues from the exploitation and maintenance of forests and green spaces, excluding leaves, needles and twigs, or from milling of the wood industry;
- Green forest chips: they come from the shredding of forestry and maintenance residues from forests and green spaces and include leaves, needles and twigs.
The particle size of the wood fragments may vary depending on the type of shredding but also on the sieving (screening) of the particles.
Wood chips are a much more homogeneous fuel than “raw” wood material. They facilitate storage, drying, packaging and transportation. Their homogeneity and their size also make it possible to fully automate the boiler.