Wood chips are chopped-up pieces of wood which are fed from a hopper into a wood chip boiler, via an auger. They are generally sourced from the product of woodland management and arboriculture activities and are used in medium to large scale heating systems. Systems exist to burn a variable sized feed stock, however, to work to high efficiency most modern systems need wood chip of the correct size, with a low proportion of both fine material and oversized chips.
• Chips are most suitable for medium to large scale boiler systems e.g. in schools or hospitals and very large homes or estates.
• Chips are manufactured from a range of sources; forestry, clean recycled wood, arboriculture and factory wastes. Chips can range in size (2mm to 5cm) and have a relatively low energy density compared to pellets. Their moisture content will typically be 25-30%.
• The running of wood chip boilers can be affected if chip size or moisture levels differ, or if there is too much ash – due perhaps to chips with bark on.
• Chip boiler systems need large storage space, and boiler shutdown is normally associated with inconsistent fuel supply rather than the hardware itself.
• A good wood chip system will provide a large home or complex with relatively cheap and environmentally friendly heat and hot water.