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Ethanol from Citrus Peels


Citrus waste can be converted into ethanol feedstock. Source: Bill Widmer, USDA ARS

Scientists at the US Department of Agriculture’s Agricultural Research Service (ARS) are developing a process to derive sugars from citrus waste (i.e., the peels) which will then serve as the feedstock for ethanol production.

In Florida alone, citrus processing yields about 5 million tons of wet waste annually, or about 1.2 million tons of dry waste, most of which is currently marketed as low-value feed for cattle. The citrus-to-ethanol process could, given further research and development, yield up to 80 million gallons of ethanol per year just from Florida citrus waste.

Citrus waste is rich in pectin, cellulose and hemicellusic polysaccharides, which can be hydrolyzed into sugars and fermented into ethanol.

Work on the producing ethanol from peels began in 1992, but was shelved due to the low cost of gasoline and the use of other oxygenates (such as MTBE) within gasoline. In 2004, however, Bill Widmer, an ARS chemist at Winter Haven, modified the process to reduce substantially the amount of enzyme required to convert citrus-waste carbohydrates to the sugars which serve as the fermentation feedstock for ethanol.

The research team the scaled the process up to where it shows some promise for large-volume production. While the original processes were 1-quart and 1-gallon sized, Widmer and his team achieved 10-, 100- and 1,000 gallon batch levels. A 10,000-gallon pilot facility is currently under construction, and should be finished by sometime this year.

The new process shows economic promise for large-volume production. His project was partly funded by Renewable Spirits LLC of Delray Beach.

The process uses the recovery of limonene and use of the residue (higher in protein than the original citrus waste) as byproducts generating revenue streams to offset the production cost.

Although the original work began with orange peels, the current research team has is studying the use of other types of citrus waste, such as that from grapefruit.

According to the ARS, the citrus-conversion process can double the value of byproducts obtained from citrus waste. With more research, material from the residue left after limonene removal and ethanol production could be turned into other industrial products, such as building-material additives and ion-exchange resins for wastewater cleanup, thereby doubling or tripling the value of the waste stream yet again.




80.000.000 gallons of ethanol per year is 5200 barrels of ethanol per day.

Small, but still something.


What will the cows eat now ?
But, yes, a step in the right direction.

Joseph Willemssen

Not a very wise fuel source, since it would be better used for its health benefits.


Does this mean my car exhaust will have that fresh lemon scent?


"What will the cows eat now?"

Like corn based ethanol there will be residual waste from the orange peels suitable for use as a feed.


I am sure the cow will have many other things to chew. While small in scale but idea behind is very important here.


"fresh lemon scent"! Now that's the gol-darn funniest thing I've seen on 'congress pages' in a long time! extreme witticism!

Rafael Seidl

Cervus -

considering that biodiesel based on restaurant grease makes your exhaust smell a little like french fries, there is indeed a chance that a vehicle running on citrus ethanol could be rather a-peel-ing. Owning a lemon might never be the same again.


I think this idea is a great idea lemon scented exhaust would be awesome and actuallty this is not a good idea we need to feed the aniamls all the citrus peels and we need to help people in the middle east to get more money


I wonder what happens to the oils in the peel. Do they at least slurry and centrifuge them out before fermentation?

(regarding the scents, I'm not sure they'd make the cut in the ethanol distillation).

zz ziled

From the April 2008 Issue of BioMass Magazine:

"Freshly Squeezed Ethanol Feedstock"

[Seventy-five percent of U.S. oranges are grown in Florida. The sunshine state’s citrus processing industry produces nearly all of the orange juice consumed in the country, resulting in up to five million tons of citrus waste each year. Options for turning that waste into something useful are limited, so the possibility of using citrus waste as a feedstock for ethanol plants is being closely monitored.]

By Kris Bevill

Americans 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 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 to 5 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 is a research chemist at the USDA Agricultural Research Service’s Citrus and Subtropical Products Laboratory in Winter Haven, Fla., and has been working on the conversion of citrus peels to ethanol for the past four years. His work is a continuation of research first conducted in the 1990s by Dr. 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.
[Full article @: http://www.biomassmagazine.com/article.jsp?article_id=1531]

zz ziled

Cross-Post to Previous Update:

BusinessWire Press Release:

"Xethanol Announces Grant Application for Citrus Waste to Ethanol Production" December 18, 2007 8:30 AM ET

Xethanol Corporation XNL, a renewable energy company, today announced that its subsidiary Southeast Biofuels LLC has filed a grant application with the Florida Department of Agriculture and Consumer Services to expand the company's work on converting waste to energy, using citrus waste as the raw material and converting it into ethanol. Only about 50 percent of a citrus fruit is used to produce juice and related products. Currently, most citrus waste is turned into low-value animal feed.

Xethanol intends to build a demonstration plant for converting citrus peel waste into ethanol. The company is negotiating an agreement to locate the plant at an existing citrus facility in Florida owned by one of the largest citrus processors in the state. The planned cost for the two-year build-out of the demonstration plant is approximately $6,000,000, and Southeast Biofuels is seeking a $500,000 grant.

The Xethanol citrus-to-ethanol project began with a Cooperative Research and Development Agreement (CRADA) with the U.S. Department of Agriculture's Agricultural Research Service (ARS) in 2004 at the USDA-ARS Citrus and Subtropical Products Laboratory in Winter Haven, Florida. The agreement is under the supervision of research chemist Dr. Bill Widmer of the USDA-ARS Citrus Lab.

The results of citrus research done by the USDA were transferred to Southeast Biofuels LLC, by Renewable Spirits of Delray Beach, Florida. Renewable Spirits owns 20% of Southeast Biofuels. Renewable Spirits' President Gwenn Stevenson commented, "Southeast Biofuels brings not only ability and expertise to this project; they also bring the components necessary to develop a demonstration system. We are very excited about their future plans and moving forward with this project."

David Ames, President and CEO of Xethanol commented, "We are pleased to be moving ahead with this exciting project to convert Florida citrus waste into renewable fuel."

About Xethanol Corporation

Xethanol Corporation is a renewable energy company focused on alternate energy products and technologies as well as producing ethanol and other co-products. For more information about Xethanol, please visit its website at http://www.xethanol.com."

The Xethanol citrus-to-ethanol project began with a Cooperative Research and Development Agreement (CRADA) with the U.S. Department of Agriculture's Agricultural Research Service (ARS) in 2004 at the USDA-ARS Citrus and Subtropical Products Laboratory in Winter Haven, Florida. The agreement is under the supervision of research chemist Dr. Bill Widmer of the USDA-ARS Citrus Lab."

More @: http://news.moneycentral.msn.com/ticker/article.aspx?Feed=BW&Date=20071218&ID=7954884&Symbol=US:XNL

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