Woodchip Biomass Fuel
Wood chips are small pieces of wood that have been cut to small pieces to allow the fuel to be ‘metered’ into the boiler in a controlled way.
Chips have a low density so are not well suited for haulage overly long distances. Typically 50 miles is used as a maximum transport distance, although large vehicles can travel further.
Chips must be ‘tipped’ from the delivery vehicle or offloaded from a large ‘walking floor’ vehicle. This does create some chip store design challenges which can be overcome, but the store will be much higher cost that an equivalent size wood pellet store.
Each boiler is designed around a particular fuel size. The current standard governing fuel particle size is EN 17225-4, and covers chips from 3.15mm in length to 200mm but it is common for chips to be much larger than this, even over 350mm in length. If the chip size specification is not matched to the boiler, then there can be problems with ‘bridging’ or blocking of the fuel feed system.
The moisture of the chips is also characterised within the ISO standard. Typically, wood chips are sold as M25 (less than 25% water content), M30, M35, M40 or M50. As with the size, it is important to understand the maximum water content that your boiler can accept. If the fuel is too wet then there will be problems with tarring, incomplete combustion and most likely the boiler will display a fault and stop as it cannot burn the wet fuel. Wet fuel boilers are available, so please make contact if this is a requirement.
Finally, the chemical constituents present in the wood are also governed by the standard. For virgin, clean, wood these are all acceptable but if the wood is contaminated in any way with paint, glues etc then the fuel will need to be assessed against the regulations before burning it.
Benefits of Woodchip Biomass Fuel
- Cheaper per kWh then pellets and logs
- More locally obtainable and can be from several sources (very often the reason for installing a wood chip boiler is availability of local, cheap fuel)
- Chip your own wood from managed woodland after preparation
- More likely to have a beneficial impact on the local economy