Ethanol from Citrus Peels

With the recent attention on using cellulosic feedstock for producing ethanol, the USDA Agricultural Research Service's Subtropical Products Laboratory in 2004 resumed research on producing ethanol from citrus waste. Citrus waste materials are rich in pectin, cellulose, and hemicellulosic polysaccharides, which can be hydrolyzed into sugars and fermented into alcohol. In Florida alone, citrus processing yields about 5 million tons of wet waste annually, or 1.2 million tons of dry waste. Most dried peel residue is marketed as low-value cattle feed. Up to 80 million gallons of ethanol per year could be produced from Florida's citrus wastes.

The research, which began in 1992, had been discontinued due to the low prices of gasoline and the high prices of enzymes needed in the process.  But an economic flip-flop occurred over the past decade, thanks to a rise in gas prices and more economical production of the enzymes.

In 2004 the process was modified to cut the amount of enzyme required to convert citrus-waste carbohydrates to sugars and ethanol. Then it was scaled up to where the process shows economic promise for large-volume production.

The original 1-quart and 1-gallon laboratory processes were modified to work at 10-gallon, 100-gallon, and 1,000-gallon batch levels. Helping to make the process economical in the short term are recovery of limonene and use of the residue (which contains significantly more protein than the original citrus waste material) after ethanol conversion as cattle feed. The current 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. These uses could double or triple the value of the waste stream yet again.

The ongoing research project has, among other goals 1) to develop an economically viable method of polysaccharides in citrus waste streams to monomeric sugars with subsequent fermentation to value added products such as ethanol, citric and other organic acids, and similar products, 2) to develop new and use existing procedures to modify and produce new polysaccharide materials, value added polymers, or resins with unique functional properties and 3) to develop new industrial uses for new products produced from the bulk waste stream residue for use as ion-exchange, building and construction materials, paper products, and other non-food related materials.

The current goal is to build a 10,000-gallon operation during this year. With further research, Florida’s citrus peel waste could yield up to 80 million gallons of ethanol per year which could be a great revenue source for citrus growers.

Not a huge potential source of ethanol, but it points out the wide variety of feedstocks that are available.

Thanks to Green Car Congress for the tip

Resources:

Ethanol Feedstock From Citrus Peel Waste, USDA Agricultural Research Service, April 2006
Enhanced Utilization of Carbohydrates and Polysaccharides from Citrus Processing Waste Streams, Agricultural Research Service Research Project, June 2004 to June 2009

Comments

[Cervus]

And your exhaust gets that lemon-fresh scent! :)

[Paul Dietz]

Limonene was actually tested as a rocket propellant. The performance was not sufficiently better than ordinary RP-1 to justify its use, though.

[Cameron]

At least you guys in the US are doing something about Ehtanol - I even hear Bill Gates is spending money on ethanol generation. Our politicans in Australia could learn a thing or two. At least we have one radio commentator willing to challenge the status quo!
Interesting podcast: http://www.freedigitalcontent.com/index.php?option=com_content&task=view&id=27&Itemid=129

[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