A computer model is presented for the calculation of the steady and nonsteady behavior of straw bales subject to surface combustion in cigar burners. The mathematical formulation is one-dimensional and the flow of gas through the straw bales is described by means of Darcy’s law far flow through a porous medium. The computer model is able to predict flow rate, temperature and composition of gas and straw as function of axial length and time. Calculated results are compared to measurements of temperature and gas composition profiles within the burning straw bales. It is observed that the straw bale temperatures as well as the outlet gas composition are predicted reasonably well. Calculations have been carried out in order to assess the implication of a straw bale feed stop upon combustion in a 3 MW district heating plant fueled with Heston straw bales. The results indicate that serious disturbances may be introduced.