Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/19/2008
Publication Date: 4/1/2009
Citation: Zhou, W., Widmer, W., Grohmann, K. 2008. Developments in ethanol production from citrus peel waste. Proceedings of Florida State Horticultural Society. 121:307-310. Interpretive Summary: Over the past 20 years, fuel ethanol from agricultural waste has been studied extensively. Although much progress has been made, high production costs remain the major obstacles to commercial production of fuel ethanol from agricultural waste, such as wheat straw, sugarcane bagasse and corn stover. A new process, developed by USDA/ARS scientists and their partner Renewable Spirits, LLC, has given rise to the potential commercial production of ethanol from citrus peel waste. In this new process, limonene, a high value co-product, can be recovered from citrus peel, thereby lowering the production cost.
Technical Abstract: Each year, the Florida citrus juice industry produces about 3.5~5.0 million tons of wet peel waste, which are currently dried and sold as cattle feed, often at a loss, to dispose of the waste residual. Profitability would be greatly improved if the peel waste could be used to produce higher value products. In this paper, a new process for making ethanol and limonene co-product from citrus peel waste is described. The process consists of three parts: pretreatment, simultaneous saccharification and fermentation (SSF), and distillation. Our pilot plant study has demonstrated that citrus peel can be fermented to produce ethanol with limonene and citrus pectin fragments obtained as co-products. The sensitivity study shows that citrus ethanol is economically competitive to citrus pulp pellets, depending on the price of citrus pulp pellet, energy, ethanol and limonene. This new technology provides an alternative disposal of citrus peel waste for the citrus industry.