Energy balance of sweet sorghum genotypes (Sorghum bicolor (L.) Moench) in a semi-arid environment of South of Italy

European Council sets a 20% share of renewable energies in EU energy consumption by 2020 (CEC, 2008). This target will be supplemented by a minimum 10% obligation for biofuel and it would require 17.5 million hectares or 15% of the total arable land of EU-27 (EU, 2007). Sweet sorghum (Sorghum bicolor (L.) Moench) may produce bioethanol from sucrose contained in the stems and also contribute to the production of bioethanol from the lignocellulosic biomass as a second generation biofuel. This C4 crop shows an high yield potential in non limiting water conditions (Cosentino et al., 1996), but in Southern Europe the high temperature requirements for seed germination which impose its growing season during summertime, when rains are almost absent, makes necessary the use of irrigation. On this basis a field experiment was carried out in order to study the energy indices of two sweet sorghum genotypes in relation to different energy inputs