Waste wood is divided into four categories based on the hazardousness of the contaminants in it. Category A I is wood in its natural state without significant contamination; Category A IV is used wood treated with preservatives. The category determines the conditions under which the processed waste wood can be recycled or used as fuel in a biomass cogeneration plant, or whether it can only be used in cogeneration plants that have extensive exhaust scrubbing. The most common use for untreated waste wood is the manufacture of wooden construction materials such as particle board.

Treatment by particle classes
After a visual check during receiving and manual pre-sorting, the waste wood is shredded down to the grain size that is most suitable for further use. First the metallic contraries are removed. Particle sizes normally follow the categories of EN ISA 17225, which defines the particle classes of biogenic solid fuels. If the waste wood is to be used as a reclaimed material, it is usually reshredded and undergoes another contrary removal step, resulting in fine chips for chipboard.