Stick an Orange in Your Gas Tank!
An apple a day keeps the doctor away, but an orange-load could keep your car on the road.
That's if Florida chemist Karel (pronounced "Carl") Grohmann's idea ever bears fruit: making ethanol, a natural "biofuel," from the peels, pulp and other wastes of processed oranges.
He first came up with the idea about six years ago at the Citrus and Subtropical Products Research Laboratory in Winter Haven, Florida. The lab is part of USDA's Agricultural Research Service.
Grohmann's idea may sound wacky until you learn that oranges and their peels are chock-full of many different kinds of sugars, like fructose. And these sugars can be fermented by microscopic yeasts to make a type of alcohol called ethanol.
Most
ethanol is now made out of fermented corn sugars. Today, ethanol is used in
about 11 percent of all automotive fuel blends sold in the U.S. In some states,
ethanol is regularly sold to help hold down air pollution from cars, trucks and
buses. That's because the oxygen it adds to
petroleum-based fuels
like gasoline helps neutralize
carbon
monoxide.
Until recently, no one had tried making this natural biofuel from orange peels or other citrus wastes. In Grohmann's view, Florida, the Sunshine State, was the perfect place to start.
For one, juice-makers and other food processors generate millions of pounds of citrus waste there each year. This waste is dried, pressed and sold as animal feed. But citrus growers and processors don't earn much from such waste. It usually sells for less than five cents a pound.
Grohmann
figured he could squeeze more value out of the industry's citrus castaways. He
knew that yeasts could partially ferment orange sugars into ethanol, also
called ethyl alcohol. But he knew that certain natural oils in orange peels
keep the yeasts from finishing the job.
That's why Grohmann decided to get extra help from another microbe, a bacterium called Escherichia coli KO11. This E. coli isn't the same kind that can make people ill from eating undercooked meat, however. Instead, this one-celled assistant came from the lab of two University of Florida scientists Grohmann teamed up with. They gave the bacterium special genes for fermenting the leftover sugars.
When grown in a batch
of citrus waste, KO11 quickly ferments the sugars that the yeast passed up. It
takes the hardworking bacterium only about two days to convert the unfermented
sugars into ethanol, acetic acid and carbon dioxide, or CO2.
Ethanol isn't the only valuable product from the bacterium's efforts, Grohmann says. The CO2, for example, can be captured and frozen into dry ice, which keeps perishable items cold during shipping or storage.
Acetic acid is used in many industrial products--from organic solvents to food items such as vinegar and flavorings.
All this from oranges! And you thought they were just for
eating, and the peels only good for throwing away.
— By Jan Suszkiw, Information Staff,
Agricultural Research Service
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