Wood chip systems can provide automated, clean and convenient heating at a range of scales, from larger domestic properties up to large scale systems for hospitals, factories, schools and district heating schemes with heating loads in the megawatt range.
Wood chip fuel can be produced from a variety of wood feedstocks:
- Small round wood from coniferous plantation (largest source)
- By products from sawmills (chips/sawdust/bark)
- Clean recycled wood (read more on using recycled wood for wood chip)
- Arboriculture arisings from management of amenity woodlands, parks etc
Wood fuel suppliers will usually purchase freshly felled timber at between 55% and 60% moisture content. They will then season the timber by stacking it outside; where it will naturally dry out over 12 months and end up at between 30% and 45% moisture content, so containing between 3,530kWh and 2,628kWh per tonne. It is then chipped in a specialist wood energy chipper and stockpiled in large agricultural sheds for sale and use (or delivered direct from chipping).
As an alternative to air drying, the deployment of mechanical wood chip drying has grown rapidly since 2014. They will the chip the wet timber immediately and undertake a forced drying process to bring the moisture content of the chips down to between 15% and 25% depending upon their customers. This has been a benefit to wood fuel users;
- Offering drier, and more consistent moisture content chip.
- Lowering fuel haulage costs are reduced as less water is transported to customers.
Purchasing wood chip
When purchasing wood chip it is vital that you know:
- What quality standard of wood chip your boiler requires, for example the particle size and moisture content. Click here to find out more about quality standards for wood chip and why they are important.
- The implications of the moisture content for the energy content of wood chip and your options for purchasing it.