The importance of biomass in combustion processes for the combined production of electrical power and district heat is still rising. In the presented work, CFD is used for the development and optimisation of an innovative combustion chamber for a solid stem-shaped biofuel in the form of compressed biomass bales. The main focus of this investigation is the maximisation of the thermal output of the combustor by an optimisation of the bale burnout and the minimisation of gaseous emissions such as VOCs, carbon monoxide and nitrogen oxide. For this purpose the functionality of a commercial CFD-solver has been extended in terms of the solid phase description and the solid–gas interactions. These sub-routines comprise the description of the solid biomass fuel as a porous bed, the biomass drying, the degradation during devolatilisation and char burnout, as well as the generation of gaseous species and the release/consumption of energy during these three steps. Moreover a simplified model for the prediction of NOx-emissions emanating from the fuel-bound nitrogen has been implemented. The results of this work show that the application of CFD enables a significant reduction of the development costs and the time-to-market of innovative chemical engineering concepts such as solid biomass combustion.