Using biomass as a source of energy has been gradually increasing in last decades, because it is a sustainable and CO2 neutral fuel. In order to improve the performance of gasifiers, academic and industrial researches need to gain insights into the highly complex processes during the combustion of biomass. Even though many research has been already done in this field, the detailed mechanisms during the interaction between the gaseous and the solid phase are still not well understood. During the combustion of biomass in a fixed bed, each particle experiences sequence of processes such as heating, drying, pyrolysis, char combustion and gasification. Furthermore in the gas phase pyrolysis products may react with the oxygen. The aim of this investigation is to propose a novel numerical model to address high level of detailed information about all the phenomena that occur during the combustion of biomass. XDEM as an Euler–Lagrange model is used, in which the fluid phase is a continuous phase and each particle is tracked with a Lagrangian approach. Energy, mass and momentum conservation is applied for each single particle and the interaction of particles with each other in the bed and with the surrounding gas phase are taken into account. Hence, the sum of all particle processes represents the entire process like of a fixed bed. An experimental investigation of the processes in a bed during the combustion of biomass is conducted. Temperature evaluation along the reactor and mass loss of the bed are measured. Predicted results are compared with the experimental data. Very good agreement between prediction and measurements was achieved, proving the accuracy of the numerical model in prediction of the biomass combustion.