Production of Ethanol from Olive Mill Solid Waste by Microwave Pretreatment and Enzymatic Saccharification

Olives and olive oil production are a major agriculture practice with more than 20,000,000 tons of olives produced yearly. Olive oil production is accompanied by production of large amount of wastes, among them olive mill solid waste (OMSW). OMSW is an abundant agricultural waste and a notorious environmental nuisance due to the high phenol content and the resulting phytotoxicity. To-date there is no economical viable solution to this waste. Here we demonstrate its conversion to ethanol by microwave pretreatment, comparing different additives and commercial saccharification enzyme. Parameters tested include sugar loss, formation of fermentation inhibitors, saccharification efficiencies and ethanol production by fermentation with commercial yeast. The results suggest that microwave treatment combined with formic acid resulted in low loss of glucose in the pretreatment stage , high scarification rates and good fermentation yields, up to 90% and 100% of the cellulose fraction for Accellerase® 1500 and Cellic® CTec2, respectively. This combination also gave the highest ethanol concentration (12.8 g/l).