Feasibility of Bioethanol Production from Cider Waste

Wastewater from cider factories (losses during transfers, products discarded due to quality policies, and products returned from the market) exhibits a Chemical Oxygen Demand greater than 170,000 mg O-2/l, mainly due to the ethanol content and carbohydrates that are added to obtain the finished product. These effluents can represent up to 10% of the volume of cider produced, and they must be treated to meet environmental regulations. In this work, a process was developed, based on alcoholic fermentation of the available carbohydrates present in ciders. The impact of inhibitors at different pH, size and reuse of inoculums and different nutrient supplementation on the ethanol yield were evaluated. The use of a 0.5 g/l yeast inoculum and corn steep water as the nutrient source allowed for depletion of the sugars in less than 48 h, which increased the content of ethanol to more than 70 g/l.