The participation of renewable energies in the generation of primary energy is expected to increase in the coming years. Biomass is considered a kind renewable energy. Considering the consumption of primary energy in Europe, renewable energies represented a 10.3% of the total consumption in the year 2008, 70% of which corresponds to biomass. In Spain, according to the primary energy balance in 2010, the 3.5% of the total primary energy consumption belongs to biomass, which represents 43% of the renewable energies, lower than in Europe. The purpose of this study was to determine the amount of nonfood biomass that the Spanish agricultural and forest lands could generate. To determine residues from forest and agricultural land we used data of surface and yields, harvest index, the residues generated by the pruning, forest residues and energy crops. Total biomass production in dry matter was 32.75 Mt for a dry year (2005) and it was 38.46 Mt for an average year (2006). We obtained a potential of 15.17 Mtoe of the biomass. Non-food biomass could supply a 10% of current Spanish total energy demand. Spain has a limited potential to generate primary energy from agricultural and forestry residues.