Generally all species of wood can be carbonised to produce use-able charcoal. There is a variation in the ash content of different woods but this is generally not significant. Bark, however, has an unacceptably high ash content and the structure of bark charcoal is too friable to be useful for most purposes.
Therefore, where possible, bark should not be used or the amount of bark charged with the wood should be minimised.
Softwoods generally produce a softer, more friable charcoal than hardwoods but where available in quantity at a suitable price, they are a good raw material and can produce all types of charcoal.
Where a choice of wood supply is possible, such as where plantations are being established to provide wood, it is worthwhile to choose the species and manage its growth rate to optimise charcoal properties. Eucalypt and acacia species produce good dense charcoal and are the favoured plantation species for the purpose. Careful tests should be made before unproven, little known species are planted.
What counts in the long run is the mass of saleable charcoal produced per unit mass of wood substance. The volume of wood grown per hectare is only a rough indicator of the mass of wood substance produced. A high volume increment may correspond to low density and hence low yield of charcoal per unit volume of wood. Also denser wood usually produces a denser, less friable charcoal. Therefore research to determine what species and what management regime produces the maximum yield of wood substance by weight from plantations is worthwhile. This is an area of active research and definite answers are not yet available. But acacia and eucalypts are still the favoured genus.