Biomass from forestry and agricultural sector provides an important contribution to encounter the government’s targets for increasing bioenergy production and utilization. Characterization of agricultural and forest wastes are critical for exploiting and utilizing them for energy purpose. In the present work agricultural and forest wastes and shrubs were sampled in two sites in north Portugal (Ave and Sabor basin) and subjected to Higher Heating Value (HHV) and chemical composition quantification. The HHV was evaluated according to the methodology described in Standard DD CEN/TS14918:2005. For the lignin content, the procedure was made by the Klason method and the extractives content was determined with the Soxhlet method. For agricultural and forest wastes the HHV values are identical with a range of 17 to 21 MJ·kg−1. However, shrubs biomass presentx slightly higher and statistically different values from agricultural and forest wastes, varying between 19 and 21 MJ·kg−1. Forest wastes contain higher levels of holocellulose compared to agricultural wastes and, with respect to extractive contents, this trend is the reverse. There is a general tendency for the woody components present thermo-chemical properties more suited for energy purposes, than the residues formed by the branches and leaves.