The way wood fuel is processed depends on what type of wood energy is being produced. But a common factor is that most wood burners require wood fuel to be a consistent size to maximise burning efficiency.
Wood pellets are produced by drying and compressing sawdust and wood shavings which are usually sourced from timber processing operations. There are several steps to this process:
- Reducing size – Material needs to be a particular size so larger material is run through a hammer mill, which thrashes the material into a fine, uniform particle size.
- Drying – The material is dried to the required moisture level.
- Pelletising – The soft, dry material is then force through a ring die at very high pressure to create the pellet shape. The wood fibre is then bound together using lignin (the wood’s natural glue.
- Cooling and sieving – Pellets are usually dropped through a cooling unit and sieved to remove smaller pieces that are not bound to the pellets.
- Bagging – Pellets are either bagged in 20kg bags or stored in silos for bulk deliveries.
Wood residue processing is a relatively simple process. Residue is collected from log felling and timber processing operations and then mechanically processed to create wood chips or hogged wood. Wood chippers and hoggers are designed to process a wide range of wood types and produce consistently sized wood fuel.