Developments in ethanol production from citrus peel waste

Weiyang Zhou, Wilbur Widmer, Karel Grohmann

Abstract


The Florida citrus juice industry produces about 3.5 to 5.0 million tons of wet peel waste annually. This material currently is dried and sold, often at a loss, as cattle feed to dispose of the waste residue. Profitability could be greatly improved if higher value products could be developed and produced from the peel waste. In this paper, the development of a new process to make ethanol along with improved recovery of D-limonene from citrus peel waste is discussed. The process consists of four parts: pretreatment to remove and recover D-limonene, simultaneous saccharification and fermentation (SSF) to produce ethanol, distillation to remove the ethanol and treatment of the residue for use as cattle feed or other co-products. Pilot plant studies have demonstrated that citrus processing waste can be fermented to produce ethanol (approximately 4% w/v) with D-limonene obtained as co-product. In order to design an efficient and cost-effective distillation column to strip off ethanol, the heat transfer coefficient and specific heat of fermented citrus processing waste was measured under forced convection using a heat exchanger. The technical difficulties of stripping off ethanol from fermented peels are also discussed. This new technology provides an alternative disposal of citrus peel waste in the citrus industry.

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283