Feasibility of SRC Species for Growing in Mediterranean Conditions

The suitability of poplar (Populus × canadensis Moench.—genotype ‘Neva’), black locust (Robinia pseudoacacia L.), and eucalyptus (Eucalyptus bridgesiana R. Baker) growing in short rotation coppice (SRC) system in a Mediterranean area (southern Italy), and under two management regimes, was evaluated in terms of survival, biomass yield, biomass quality, and soil fertility. The high management regime (H treatment) consisted of high plant density (6667 trees ha−1) and a 2-year harvesting cycle; the low management regime (L treatment) consisted of low plant density (1667 trees ha−1) and a 4-year harvesting cycle. The dry biomass production was 36, 13, and 9 t dry matter (dm) ha−1 in the H treatment and 25, 14, and 7 t dm ha−1 in the L treatment for eucalyptus, black locust, and poplar, respectively. The analysis of the biomass showed a superior quality for the black locust feedstock because of its low moisture and ash percentages, high heating value (HHV), and low alkali metal concentrations, although, from an environmental point of view, the high N (12.3 g kg−1) and S (0.7 g kg−1) biomass concentrations would increase the pollutant emissions generated by combustion. Eucalyptus showed a high HHV, especially for the H treatment (18.70 MJ kg−1). Its high concentrations of K (4 g kg−1) and Mg (0.8 g kg−1) could provoke slagging and fouling in combustion equipment, and the high concentrations of S and N, if leaves are considered in the harvested biomass, indicate the low quality of its feedstock. No specific poplar feedstock stood out, although it had a good HHV (19.02 MJ kg−1). The soil fertility was not affected negatively after the 4-year SRC cycle, while S content in soil showed a tendency to increase in the case of black locust cultivation.