This work aimed to evaluate the elemental composition of different biomass components of the forest species Acacia mearnsii De Wild, Eucalyptus grandis W. Hill ex Maiden, Mimosa scabrella Benth and Ateleia glazioviana Baill, at their first, third and fifth year after planting, aiming at bioenergetic use. The biomass elemental composition was determined by quantifying the levels of carbon, hydrogen, nitrogen, sulfur and oxygen. The three ages, the four species, and the four compartments differ in relation to the elementary constituents. The use of trees at any age allows for energy use. The fifth year presents the best carbon and hydrogen values, being the best age for using the biomass energy of the different species. A. mearnsii presents the highest carbon values for the leaf and A. glazioviana presents the highest hydrogen values for all compartments. The leaf is the best compartment for energetic use.
