Moisture Content

Moisture Content

The majority of biomass boilers are designed to burn wood chip with a maximum level of moisture in it. This moisture content can vary from 25% to 60% but is most typically at 35%.

The levels specified by the boiler installer company will vary according to the make, style and size of the boiler and its fuel transfer system. We test moisture content using various methods which you can see here.

If the moisture content of the wood chip is too high it can cause a boiler to shut down, while if it is too low and the wood chip is too dry it will burn too quickly.  Having a reliable supply of high quality wood chip at the correct moisture content is probably the most significant factor affecting the operation of a biomass boiler.

Forest Fuels tests its wood chip to ensure that we always deliver premium grade fuel at the correct moisture content.

Virgin wood chip

Mature trees are rarely cut down specifically for wood fuel.  Instead virgin wood for biomass is supplied from residues such as branches, small round wood (SRW), thinnings, poorly formed wood, stumps and brash.  High quality timber will continue to be processed by sawmills for the construction, furniture and other industries, and these too will produce residues and co-product such as offcuts, bark and sawdust that are also potentially suitable fuel.

The raw material to produce woodchip for fuel and hardwood firewood is plentiful in the UK. The Forestry Commission estimates there is an additional 2,000,000 tonnes of material per year available from un-managed woodlands.

Forest Fuels can provide long-term, guaranteed supplies of woodfuel and has established links with the Forestry Commission and many private estates, sawmills, joinery organisations and other growers across the south west.

Clean recycled wood chip

Used wood which is natural or merely mechanical processed wood can be an excellent source of fuel. It needs to be carefully screened and processed to remove any contaminants that are not normally found in wood in its natural state.

Sources of clean recycled wood might include pallets, transport cases, boxes, wood packages, cable reels or construction wood. Forest Fuels has a stringent process for ensuring our clean recycled chip to ensure it is of the highest quality. It has proved very popular biomass fuel with clients who are promoting a wide sustainability agenda.