Woodfuel, of all the biomass resources, has the greatest immediate ability to deliver significant sustainable solutions throughout the region.

The main types of wood fuel are logs, wood chip and wood pellets. In a domestic setting logs can be used in open fires, stoves and manually fed boilers, for space and water heating and cooking. Woodchip is mainly used in community to commercial scale boilers and for power generation. Wood pellets can be used at any level – from domestic pellet stoves to very large boilers. As a compressed form of wood with very low moisture content they burn very efficiently. These three main types of wood fuel are discussed in more detail below.

Logs

Wood in the form of logs is the simplest and most common form of wood. Logs used for fuel will simply be described by their dimensions and by the species of tree from which the logs came. Those used in log burners and stoves usually have a maximum length and width.

Ideal moisture content: <20%
Energy content: ~ 14GJ/t or 3,900kWh/t (at MC20)
Density: ~ 475kg/m3
Price: ~ £20/m3

Chip

With wood chip, fuel quality is vitally important. Particle size and moisture content cannot be compromised or the user is likely to encounter problems. In addition, chip used for fuel must come from an untreated source. Chip suppliers should be well acquainted with the relevant specifications for different boiler types. Normally, fuel quality chip will need to have dimensions of around 3cm and be of less than 30% moisture content.

Ideal moisture content: <30%
Energy content: ~ 12GJ/t or 3,400kWh/t (at MC30)
Density: ~ 250kg/m3
Price: ~ £45/tonne

Pellet

Wood pellets are the most dense biomass fuel (both in terms of weight and energy). They have a low moisture content and good flow properties so are easy to deliver and store. Normally made from compressed sawdust, they can have diameters of 6, 8 or 10mm. The smaller pellets are usually needed for smaller boilers.

Moisture content: <8%
Energy content: ~ 17GJ/t or 4,700kWh/t (at MC8)
Density: ~ 650kg/m3
Price: ~£140/t

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