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Thanks to recent hikes in gasoline
prices, there is a renewed interest in finding a cheaper way to fill
up the gas tank. Researchers at the Agricultural Research Service (ARS)
Citrus and Subtropical Products Laboratory in Winter Haven, Fla. have
been working on a potential substitute: citrus peels.
In 1992, Karel
Grohmann, then research leader of the Winter Haven lab, began
researching the feasibility of converting citrus peel waste into fuel
ethanol. Citrus waste materials are rich in pectin, cellulose and
hemicellusic polysaccharides, which can be hydrolyzed into sugars and
fermented into alcohol. Most of this dried peel residue--a total of
1.2 million tons annually in Florida alone--is currently marketed as
low-value cattle feed, despite its relatively high processing cost.
In 2004, Bill
Widmer, an ARS chemist at Winter Haven, picked up where Grohmann left
off, with the help of a cooperative research and development agreement
partner, Renewable Spirits LLC of Delray Beach, Fla. Widmer and his
scientific team first modified the process to substantially reduce the
amount of enzyme required to convert the citrus waste carbohydrates to
sugars and ethanol. Now the process shows economic promise for
large-volume production.
Beginning with the
one-quart-to-one-gallon laboratory process developed by Grohmann, the
process was modified to work at 10-gallon, 100-gallon and 1,000-gallon
batch levels. A 10,000-gallon pilot facility is currently under
construction, and should be finished by sometime this year. With
further research, according to Widmer, Florida's citrus peel waste
could yield up to 80 million gallons of ethanol per year. |