Energetic characterization of densified residues from Pyrenean oak forest

In Southern Europe there are vast areas of forestry land which are composed of Pyrenean oak (Quercus pyrenaica). However, these areas represent an important source of biomass which can be used for energetic purposes. The maintenance of the Pyrenean oak woodland is carried out by means of the extraction of complete trees, having a final residue made of very different types of branches that can influence on the properties of the pellets. The present work shows the results obtained from the characterization and analysis of different types of pelletized residues of the Pyrenean oak. The results have been classified in order to find out if different pretreatments for the residues, according to their branch size, are necessary. Nevertheless, any significant difference was found among the three classes of samples. On the other hand, during the pelletization of the different types of branches some of their physical characteristics, such as the bulk density, were substantially improved. However, the chemical characteristics of the samples were not significantly altered during this densification process. Furthermore, the pellets showed interesting physical resistance probably due to the high percentage of lignin present in forest biomass which improves their durability.