*3.1. The Variety Factor*

Plants show a huge amount of similarities in properties between species, ye<sup>t</sup> with significant specific variations such as the ones related to combustion properties. In this research, we focused on contrasting whether the differences were also notable between varieties within the same species. Marcona and Vayro varieties were statistically compared by means of variance analysis. The results obtained are shown on Figure 1. As we can see, the gross calorific value of Marcona (18858.70 J·g<sup>−</sup>1) was statistically higher than the one obtained by Vayro (18148.20 J·g<sup>−</sup>1). The same results were reached in the evaluation of the carbon and the hydrogen contents, while no differences were found for the nitrogen content. Marcona has been described in previous research as a variety with very high residue productivity (13.91 kg dry matter/tree) [20], this variety could be of interest in order to obtain not only a higher level of biomass in weight per tree but also a higher energetic potential because of its superior gross calorific value.

**Figure 1.** LSD intervals at 90% confidence level in the influence of the variety factor in residual biomass characteristics. (*n* = 108).
