Biomass fuels represent a renewable energy source, they are CO2 neutral fuels, and their use reduces the consumption of fossil fuels and limits the emissions of SOx, NOx, and heavy metals. They are used in pyrolysis, gasification, combustion, and co-combustion. The devolatilization is a fundamental mechanism in all these processes, especially for high volatile matter fuels. In this work, the devolatilization of biomass fuels ( of different origin, properties, and composition) and biomass components is studied coupling thermogravimetric (TG) analysis with infrared spectroscopy. The characteristic temperatures are determined for the main devolatilization steps and compared for all fuels. A bituminous coal and a paper sludge are also studied for comparison. Light gases released (CO, CO2, H2O, CH4, CH3OH, HCOOH) are detected, whereas more complex organic ( hydrocarbon and oxygenated) compounds are grouped because of the large variety of volatile species released in a narrow range of temperature. The weight loss of biomass fuels is related to their chemical composition (i.e., considering the devolatilization behavior of cellulose, hemicellulose ( xylan), and lignin in the same operating conditions). The aim of the work is to apply a summative law for the TG results ( validated in previous experimental and literature works) to obtain the chemical composition of biomass fuels and to validate and extend a summative law for the FTIR profiles of volatile species released. Calculated values obtained using this method are in good agreement with the experimental results. Therefore, the validation of this correlation allows the prediction of the devolatilization of biomass fuels considering the initial chemical composition. This is useful for practical applications, plant designing, handling, and modeling.