'good wood' for heating

The usefulness of a type of wood for heating very much depends on its properties.

Firstly, the physical size and shape of the material: logs must be an appropriate shape to fit in the boiler and wood chips must fit through the fuel handling machinery.

Secondly, the species of tree that the wood is from: hardwoods are usually denser than softwoods, therefore a unit volume of hardwood 'stores' more heat potential than the same volume of softwood. However, the heat output per unit weight is approximately the same for all wood types of the same moisture content.

Thirdly, the moisture content of the wood: damp wood is heavier than dry wood. It also gives off less heat when burnt. Freshly felled wood may contain up to 50% moisture, whereas 'dry' wood is specified as having a moisture content of 10-15%. Wood pellets approved under the British BioGen Code of Good Practice have a moisture content under 10%.

British BioGen Code of Good Practice [1]