ABSTRACT.- Using biomass of forest origin to obtain solid, liquid, and gaseous fuels has demonstrated its potential both at an experimental level and in commercial situations. This framework evaluated Eucalyptus benthamii, E. dunnii, and E. grandis planted at densities of 2220, 3330, 4440, and 6660 trees per hectare 56 months after planting. The chemical composition and heating value of biomass fractions were evaluated. The LHV value (KJ/Kg) of the bark was 17,227, 16,813, and 16,167; the leaves 22,491, 23,031, and 21,358; the wood 18,725, 18,577, and 18,828 for E. benthamii, E. dunnii, and E. grandis, respectively. The VM, FC, and A contents (%) were 82, 12, and 6; 84, 11, and 5; and 89, 10, and 1 for E. benthamii; 84, 9, and 7; 84, 10, and 6; and 90, 9, and 1 for E. dunnii; and 84, 8, and 7; 84, 11, and 5; and 90, 9, and 1 for E. grandis in the bark, leaves, and wood fractions, respectively. The contents of C, H, and O (%) were 48, 5, and 40; 57, 6, and 30; and 50, 5, and 44 for E. benthamii; 47, 5, and 41; 57, 6, and 28; and 50, 5, and 44 for E. dunnii; and 46, 5, and 42; 56, 6, and 32; and 51, 5, and 44 for E. grandis in the bark, leaves, and wood fractions, respectively. E. grandis is the species that combines the best results from the point of view of its energy potential at the same time as an absence of effects due to planting density. The prediction models for the heating value were based on the carbon content. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.