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Ethanol from Citrus Waste

Florida Company to Build Plant to Convert Citrus Waste to Ethanol

FPL Energy is constructing an ethanol production facility in Florida that will be the first of its kind to produce ethanol from citrus waste. Taking the old adage about lemons and lemonade to new levels, the facility will take the rinds and fruit solids left over from the juicing process and convert it into fuel grade ethanol.

The project will be a partnership between FPL Energy, a subsidiary of the company that owns Florida Power and Light, and Citrus Energy. Citrus Energy was formed in 2006 to commercialize citrus fermentation technology developed by the USDA Citrus Laboratory. Southern Gardens, a citrus processor, will supply the citrus waste and processing site.

 Florida Lacks Ethanol Production

Florida currently has no domestic production of ethanol. Most ethanol in the United States is produced from corn and Florida does not have the right climate for commercial corn production. This means that Florida must either import ethanol or develop alternative sources of production to support the US government's alternative fuels strategy.

Converting a Florida food crop to ethanol production is not cost effective. The food value of each of the Florida's major crops is much higher than the fuel value. This leaves using agricultural waste as an ethanol feedstock as the only near term alternative that Florida has for producing fuel grade ethanol.

Citrus Waste as Ethanol Feedstock

The signature crop produced in Florida is citrus fruit for the food and juice market. The juice processing of oranges and grapefruit produce over 5 million tons of citrus waste every year. Currently most of that waste is processed into a dry cattle feed known as citrus pulp pellets (CPP). The CPP are sold at less than their processing cost with the losses offset by juice sales.

In the 1990's the USDA Citrus Lab developed an ethanol production process that used the residual sugars and cellulose in citrus peel. A series of citrus specific enzymes was developed to convert the cellulose to sugars for the fermentation process. From that point forward the ethanol process is much the same as used in corn-ethanol production.

Valuable Byproducts

While this will be a fuel ethanol plant, it will also produce two byproducts that will sold to help defray the cost of production. First, the solids that remain after any fermentation process still retains value as cattle feed. The solids will be sent to the current facility used to make CPP for drying and packaging.

The second byproduct is limonene, a terpene based solvent that is responsible for the characteristic citrus odor. Limonene has some anti-bacterial and anti-fungal properties, which makes it a valuable addition to cleaning and disinfectant products. Limonene must be removed from the feedstock before fermentation can take place.

Facility Limitations

The facility will be co-located with the citrus juice processing facility to reduce raw material shipping and storage costs. There are two drawbacks to this, however. First, the size of the ethanol facility is limited by the amount of available citrus waste. For this plant that means about 4 million gallons per year instead of the 50 million gallons of a typical corn based plant.

The second draw back is that the juicing operation only operates 8 months out of the year. Since there are no provisions for storing the citrus waste, the citrus-waste ethanol production will have to stop when the waste stream stops. Current plans call for the facility to be used for cellulosic ethanol research during the off months.

Florida is attempting to make lemonade from their citrus waste. Biofuel production facilities like this can make a significant contribution to future energy production.

References

  • http://www.citrusenergy.net/productsandservices.html
Submitted by SuperGreenMe on Oct 31, 2008