This study provides essential information related to the nutrient and carbon levels and the energy potential of Eucalytpus nitens (Deane & Maiden) Maiden bionenergy plantations located in northwestern Spain. Nutritional analysis showed that leaves and bark had the highest concentrations of N, P, K and Mg. Carbon concentration was constant for all above-ground tree components. Nutrients and carbon were analyzed at stand level according to plantation productivity. Stemwood, the main tree component at the end of the rotation, had the highest nutrient content, except for N and Ca, which were highest in leaves and bark respectively. Based on this study, the nutrient content per ha of above-ground biomass was 243-706 kg N, 44-122 kg P, 131-375 kg K, 121-329 kg Ca and 25-67 kg Mg at the end of the bioenergy rotation (6-12 years, depending on site quality) and 19-56 Mg C ha-1. Energy analysis showed a fairly constant Net Calorific Value for wood, 18.32 ± 0.19 MJ kg-1. The results obtained are valuable for selecting the most appropriate forest management system in these bioenergy plantations, and thereby promote the sustainable use of woody crops.