<p>This work investigated the bioenergy potential of wood from different <i>Eucalyptus</i> genetic materials grown under different planting densities. We used a trial conducted as part of the TECHS research program, which is in Macaíba, Rio Grande do Norte State, in the Northeast Region of Brazil. Five clones were grown at six densities (497, 641, 1075, 2083, 4761 and 13333 trees ha^-1). Higher planting densities led to greater mortality, decreasing from 86 to 61% as density increased after 7 years of cultivation. Survival directly influences productivity, whereby every 10% increase in survival resulted in a linear increase of 4.7 m³ ha^-1 year^-1. There was a difference in wood density among the clones, with a variation of 19% between the clones with the greatest (501 gl^-1) and lowest (420 gl^-1) density. Spacing also had an effect, with a variation of 17% between the highest and lowest wood densities, which were obtained at densities of 497 and 13,333 trees ha^-1, respectively. Energy generation was not strongly correlated with spacing (R² = 0.15, <i>p</i> = 0.02) because of the strong influence of mortality on biomass production. There was a strong correlation (R² = 0.99, <i>p</i> &lt; 0.0001) between the average annual increment of wood production and wood density.</p> Graphical Abstract <p></p>