Globe artichoke crop residues and their potential for bioethanol production by dilute acid hydrolysis

The globe artichoke [Cynara cardunculus var. scolymus (L.) Fiori] produces large amounts of residues after harvesting. Such biomass could be exploited for energy purposes and, for obvious reasons, does not compete with food production. In this work, the production of residues from the cultivars Apollo and Violetto di Sicilia, grown in Ramacca (Sicily), and from the cultivar Spinoso sardo, grown in Siracusa (Sicily), has been evaluated over a two year period. The average biomass productivity of crop residues from the different globe artichoke varieties assessed in this study is around 11 t dry matter (DM) per hectare per year. This is a considerable figure, especially considering there are more than 14,000 ha cultivated with globe artichoke in Sicily. For ‘Spinoso sardo’, an evaluation of sugar production, for potential ethanolic fermentation, was carried out. The biomass has therefore been subjected to various pretreatments with different dilute sulfuric acid solutions (0, 0.5 and 2%), in order to break up its lignocellulosic structure. The responses of biomass to the dilute acid hydrolysis (DAH) were evaluated by the saccharification yield of the pretreated solids. Results show that, with the harshest conditions of this experiment (H2SO4 2% and 121 °C for 1 h), up to ~440 kg of fermentable sugars (glucose and xylose) per ton of DM are obtainable from ‘Spinoso sardo’ pretreated biomass. The same pretreatment resulted in a theoretical production of bioethanol per hectare of ~3,900 kg.