Biomass is an important source for energy production but remains a high moisture content material. A drying process can increase its energy value. To study the heat and mass transfer in a porous medium, the modelling approach is conducted in order to simulate the drying process of a donut made of compacted biomass. The conservation equation, the transfer laws, the equilibrium equations and the equations of states are established for the three phases of the porous medium: solid, liquid, gas. The finite volume approach is chosen to have access of local and averaged values of temperature and moisture content in particular. The external drying conditions are taken constant for both temperature and relative humidity. The typical shape of donut produced in South Africa is simulated. The temperature evolution is quite rapid (a few hours) while it take several days for the moisture content to reach steady states conditions.