Woodchips

Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees, branches, logging residues, stumps, roots, and wood waste. Woodchips may be used as a biomass solid fuel and are raw material for producing wood pulp. They may also be used as an organic mulch in gardening, landscaping, and ecosystem restoration; in bioreactors for denitrification; and as a substrate for mushroom cultivation. The process of making woodchips is called wood chipping and is done using a wood chipper. The types of woodchips formed following chipping is dependent on the type of wood chipper used and the material from which they are made. Woodchip varieties include: forest chips (from forested areas), wood residue chips (from untreated wood residues, recycled wood and off-cuts), sawing residue chips (from sawmill residues), and short rotation forestry chips (from energy crops). The raw materials of woodchips can be pulpwood, waste wood, and residual wood from agriculture, landscaping, logging, and sawmills. Woodchips can also be produced from remaining forestry materials including tree crowns, branches, unsaleable materials or undersized trees. Forestry operations provide the raw materials needed for woodchip production. Almost any tree can be converted into woodchips, however, the type and quality of the wood used to produce woodchips depends largely on the market. Softwood species, for instance, tend to be more versatile for use as woodchips than hardwood species because they are less dense and faster growing. A wood chipper is a machine used for cutting wood into smaller pieces (chips). There are several types of wood chippers, each having a different use depending on the type of processing the woodchips will undergo. Woodchips used for chemical pulp must be relatively uniform in size and free of bark. The optimum size varies with the wood species. It is important to avoid damage to the wood fibres as this is important for the pulp properties. For roundwood it is most common to use disk chippers.