In recent years, there have been considerable developments in combustion models for fossil fuels that are used for design purposes by means of CFD modelling of combustors in power stations. As a result it is now possible to predict combustion behaviour in complex power station furnances fuelled by coal. Biomass is finding increasing use as a fuel in similar circumstances and at present there are no accurate models available. The object of this paper is to examine the applicability of the present models to wood (pine) and straw and to provide ways to improve their accuracy.