Wood Chips

We supply many boilers using wood chips as their source of fuel. For example, with the SL30-150kW and SL199- 250kW we  recommend using  G30 and G50 wood chips. This means chips that have an average size of 30mm, plus a maximum of 30% moisture content. Using quality, dry wood chips will get the most out of your biomass boiler.

If buying wood chips, be sure that they are of the highest quality (as set out by the assurance scheme run jointly by HETAS and Woodsure). The grade and moisture content of your wood chips should be outlined on your delivery paperwork.

To find suppliers, check out the Biomass Suppliers' List (BSL) We’ve found this to be the most comprehensive list of biofuel suppliers in the Wye Valley and across the UK. 

We always recommend checking the wood chips at the point of delivery. We’ve got a handy guide to inspecting woodchip quality here. 

Chipping Your Own Fuel

If you are lucky enough to have your own supply of wood, you can achieve maximum savings on your fuel costs. If you have your own logs, a contract chipping service (check out the Biomass Suppliers List (BSL) again for chipping services) can process 15-20 tonnes per hour. This means that depending on the size of your fuel store you can get a good few months' supply chipped in one go and fuel cost savings of up to 80% versus fossil fuels.

Chipping wood for biomass boilers

If you do own your own managed woodland you can also sell your wood to suppliers to further reduce your fuel costs.

If using your own wood, make sure it is seasoned appropriately so that it has a maximum moisture content of 30% (before chipping). You can achieve this by  storing the wood, before chipping, raised from  ground and covered in tarpaulin which is open at each end in order to air dry. Once the wood has started to season it will have less of a tendency to reabsorb water.

Your fuel grade chipper  will need set screens so that you can process G30 to G50, producing an average chip size of 30-50mm. A general agricultural chipper, essentially a shredder, will not do the job. Again, the Biomass Suppliers' List will help you choose the correct company.

chipping wood for biomass boilers


When it comes to storing your wood, you can either convert an existing building into your fuel store or build new. The space needs to be covered and enclosed with easy access for wood chip delivery or access for the shredding machinery. The larger the building the maximum amount of fuel can be stored, decreasing the amount of fills a year and allowing you to buy in bulk.

Make sure you have access through a hatch so that you can regularly inspect the quality and that the floor of your store is level with agitator sweep arms.

An annual clear of the store will need to take place to ensure all foreign objects are removed.  We would suggest during summer when your boiler is not needed quite so much.

Finally, take a look at the table below to explore how wood chips perform, compared to other sources of fuel:

Fuel kg/m3 g CO2/kWh kWh/ Kg
Wood Chips 250 7 3.5
Logs 350 7 4.1
Wood Pellets 650 15 4.8
Coal n/a 484 8.6
LPG n/a 323 6.6
Heating Oil n/a 350 10
Electricity n/a 530 n/a
Source: Biomass Energy Centre