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PHOTO: USDA-ARS CITRUS AND SUBTROPICAL PRODUCTS LABORATORY
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mericans love oranges. According to the USDA, the fruit consistently ranks third among the nation’s favorite fresh fruits and it’s the No. 1 fruit juice. Americans consume two-and-a-half-times more orange juice than apple juice, making juice production a huge industry for Florida citrus processors. But before you drink that next glass of OJ, consider that half of the orange used to make that juice becomes waste material. In fact, the Florida citrus industry produces 3.5 million to 5 million tons of citrus waste every year. Which begs the question: What possibilities are being explored to turn that waste into something useful, and who’s brave enough to try? Bill Widmer, a research chemist at the USDA Agricultural Research Service’s Citrus and Subtropical Products Laboratory in Winter Haven, Fla., has been working on the conversion of citrus peels to ethanol the past four years. His work is a continuation of research first conducted in the 1990s by Karel Grohmann, who developed the conversion process. At the time of Grohmann’s research, gas prices were relatively low and enzyme costs were high. When Widmer took on the project four years ago, gas prices were substantially higher and enzyme costs had come down enough to make it possible to further explore citrus-peel-to-ethanol technology. Widmer set out to modify the process into something that would be economically feasible and that could be a continuous process for commercialization purposes.
Citrus waste at a Florida processing facility is moved by conveyor to a peel bin for further processing.
Technology His research was a success. Four years ago it took $12 to $15 worth of enzymes to produce 1 gallon of ethanol. Widmer was able to lower the enzyme cost to approximately
ETHANOL PRODUCER MAGAZINE JULY 2008