Wood Pellet Manufacture
Any untreated wood waste can be used, from sawdust and wood chip, to larger off-cuts, whole trees and stripped bark. The feedstock must be from solid wood, never from composites such as chipboard. Different raw materials will require different levels of processing. Where freshly harvested entire trees are used, much more energy must be consumed during the drying process. This has economic, energy and environmental costs associated with it. Recycled wood can also be used, but not if it has been treated. Using treated wood as a source is limited by national regulations stipulating the amounts of particular compounds, heavy metals and additives that can be legally present in the pellets. The Codes of Good Practice (2000), developed by British BioGen for the DTI, state that pellets destined for large commercial use (mainly co-firing in power stations) can contain up to 15 per cent material other than biomass (MOB), while pellets destined for domestic use must be manufactured from virgin and clean wood only.