Taming the Wild Cuphea

Cuphea has been in development as an industrial crop for a number of years. Once the oilseed reaches commercial viability it could replace imported oils and petroleum as a source for capric and lauric acids used in the production of manufacturing surfactants, detergents, lubricants, personal care products and other specialty chemicals.
By Susanne Retka Schill
The purple flowers of the cuphea oil plant could add a splash of color to the U.S. crop scene, but not before its wild side is tamed. Cuphea's seed shattering trait, which is helpful in the wild to disperse seeds for propagation, makes it difficult to capture the oilseed's full yield potential. The crop's current yields of 500 to 800 pounds per acre limit its use in high-value oil markets. Cuphea has the potential to become a hot commodity, however, if researchers succeed in boosting yields to the 2,000 pound per acre level. "I've heard one company say it would use production from 300,000 acres, and another from 1 million acres," says Russ Gesch, a research plant physiologist with the USDA Agricultural Research Service (ARS) in Morris, Minn., who is among a small group of researchers trying to domesticate cuphea.

Cuphea could be a domestic source for short- and medium-carbon chain fatty acids such as capric acid and lauric acid used in manufacturing surfactants, detergents, lubricants, personal care products and other specialty chemicals. The current sources are imported palm and coconut oil and petroleum. As the price of petroleum and tropical oils increase, and the price of corn and soybeans adjust to new market conditions, a yield-enhanced cuphea has the potential to compete.

Cuphea is the genus name for 260 species found in uncultivated areas from the southern United States into Central and South America. Thirty years ago, scientists looking for promising new plant materials began working with cuphea because it's a natural source of short- and medium-chain fatty acids. The vegetable oils commonly produced in the United States from soybeans, canola, sunflowers and others are 18-carbon-chain oils used primarily in cooking. Cuphea is of particular interest to researchers because each plant species produces high proportions of different fatty acids. Current cuphea agronomic lines contain 30 percent to 35 percent oil, of which 80 percent to 90 percent is capric acid. Other cuphea species favor lauric acid and can yield as much as 80 percent, compared with palm and coconut oils which typically yield 50 percent lauric acid.

Agronomic Characteristics
Researchers are challenged by several agronomic problems in their efforts to commercially produce cuphea. Besides the shattering issue, cuphea is indeterminate, meaning it continually grows and flowers, and thus ripens unevenly. The agronomic lines Gesch is developing in Minnesota, however, are steadily improving. He is working with a hybrid developed from two cuphea species, C. viscosissima and C. lanceolata, one native to the United States and the other native to Mexico. This short-season annual performs much like soybeans, he says. It can be planted in the northern Corn Belt in early- to mid-May and harvested in late September after a killing frost. It grows quite densely and in one trial yielded a combined seed and biomass total of five tons per acre, Gesch says. The seeds are disc-shaped and small, comparable to canola seeds.

The agronomic lines are well-adapted to western Minnesota and eastern North Dakota, he says. The oilseeds have yielded as much as 1,200 pounds per acre under intensive management, but farmers growing small acreages have seen yields as small as zero to 800 pounds. "Timing is really important," Gesch explains. "It's not forgiving if you're not on time with the herbicide or with harvest." Illinois research determined that cuphea is beneficial in rotation with corn as it helps to break the corn rootworm cycle and boost corn yields. The occasional zero yields, however, demonstrate that the plant can't tolerate stress. This year, Gesch began new trials at Morris with two or three agronomic lines and several wild species that have shown an ability to adapt to varying temperature and moisture conditions.

In 2007, cuphea planted in central Illinois yielded an average 550 pounds per acre, according to Terry Isbell, who leads the new crops and processing technology unit at the USDA Agricultural Research Service in Peoria, Ill. At such low yields, he says the primary market for the crop will be the relatively small, high-value cosmetic uses where cuphea oil's high solubility, dispersibility and oxidative stability are desirable characteristics. "When we hit 1,000 pounds per acre we can think about the [10-carbon] markets," he says. The 10-carbon-chain fatty acids can be used in surfactants and has been utilized by one company in an environmentally friendly wood preservative.

Isbell's team in Peoria patented a chemical process combining capric acid with oleic acid, the most common fatty acid, to produce a lubricant. "It makes a lubricant with good low-temperature points, which is oxidatively stable so it doesn't degrade in an engine or hydraulic system," he says. With a pour point of minus 41 degrees Celsius (minus 41.8 Fahrenheit) and excellent lubrication characteristics, it outperforms petroleum-based motor oils even in winter in International Falls, Minn., which is considered the nation's icebox. A start-up Montana company, Peaks to Prairies LLC, has licensed the technology and will soon be introducing a line of lubricants. The products probably won't contain capric acid derived from cuphea oil until it's commercially available.

It's those kinds of products that have prompted some companies to invest in development of the crop. Andrew Hebard leads one of the companies looking to commercialize cuphea production, Technology Crops International, with offices in Winston-Salem, N.C., Fargo, N.D., and Essex, England. "We are seeing a strong interest in this product," he says. The company has contracted with farmers to grow the crop for its research effort and they supply a small commercial market. Hebard projects the crop is a year or two away from being commercially available for a specialized higher end-value market, but further away for wider commercialization. Technology Crops specializes in industrial crops, contracting with farmers at prices that are competitive with soybean and corn markets and providing information on best production practices to help ensure successful harvests. The company finds markets for the oil and the protein meal coproduct. Hebard describes cuphea as a new crop with several different industrial uses. "It creates an opportunity for growers to produce something agronomically different, a value-added crop," he says.

Researchers are also exploring uses for other cuphea species. One species produces short carbon chains, C6 and C8 and has the potential to produce a biofuel with properties similar to No. 2 diesel without involving the transesterification process. There is also interest in using cuphea esters as a jet fuel source, Isbell says. He estimates it will be three to five years before the crop begins to be commercialized. "We have to get the yields up to 2,000 pounds per acre before the markets will start to establish themselves," he says. Once that benchmark is reached, the market for surfactants and detergents will pull the crop out of the specialty arena and into the commodity realm.

Gesch and Isbell agree that the process would be more efficient if they were able to dedicate a plant breeder to the crop's development and to enlist the help of a geneticist to develop gene markers to speed up the selection of desirable traits. "The new crop group in the United States is not a large group," Isbell explains. "We work on several crops simultaneously with four to six crops spread across the whole United States." The researchers are part of the Association for the Advancement of Industrial Crops, which began meeting 20 years ago to share developments on crops with the potential to replace petroleum-based chemicals. "All of us are getting intensive scrutiny now," Isbell says. "A lot of people are calling us and asking questions about the crops we've been working on for some time. The world is coming to the realization that petroleum will come to an end."

Susanne Retka Schill is a Biomass Magazine staff writer. Reach her at [email protected] or (701) 746-8385.