Disposal of expired, sugar-containing beverages by conventional wastewater treatment represents a waste of a potentially valuable resource that could instead be used for ethanol production. A key limitation is that many soft drinks contain sodium benzoate as a preservative, and this interferes with yeast fermentation. In this study various approaches were used to inactivate or remove sodium benzoate so that fermentation could proceed. Transformation of benzoic acid into its less toxic salt form, by adjusting the fermentation pH to 7, only marginally increased fermentation efficiency and ethanol yield of Mountain Dew. Treatment with the anion exchange resins Biorad UNO Q1 versus DowEX Monosphere 99CA/320, achieved high fermentation efficiencies and yields, but were far too expensive for commercial application ($10-85/L ethanol produced). Biorad UNO Q1 and DowEX Monosphere 99CA/320 resins achieved fermentation efficiencies near 100%, and the highest ethanol yields. However these treatments were prohibitively expensive. The highest performing and most economical treatment was activated carbon BG-HHM, with an ethanol yield of 82.5%, fermentation efficiency of 93.5%, and a treatment cost of only $0.02 per liter ethanol produced. Activated carbon WPH performed similarly, but at a 10-fold higher cost. Treatment with biochar was the least expensive ($0.01/L ethanol produced), but ethanol yields were only 45%.
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