In this work, calorimetric experiments were performed in order to study the thermal oxidative degradation of rockrose, heather, strawberry tree and pine. Firstly, lignin, holocellulose and cellulose were extracted from the fuels and their contents were calculated according to normalized chemical methods. Then, Differential Scanning Calorimetry was used under air sweeping with dynamic mode on the temperature range [400 - 900 K] in order to obtain reaction enthalpy. Finally, a simple enthalpy model was developed based on the enthalpy of the thermal degradation of each biopolymer with their respective proportions in the fuels. The results showed that the model agreed satisfactorily to experimental data.