ALBANY, Calif.—More than two decades ago, the Agricultural Research Service of the U.S. Department of Agriculture obtained patents on processes designed to make the desert shrub guayule a commercially viable source of natural rubber.
Those patents have lapsed, but research in guayule continues, according to Colleen McMahan, lead scientist for domestic natural rubber at the ARS office in Albany.
"Improving that crop is a big part of what we do," McMahan said.
Much of the ARS' current work in guayule is devoted to genetic bioengineering to improve the plant's rubber yield, according to McMahan. "The watchwords are yield, yield, yield," she said.
Then-ARS scientist Katrina Cornish obtained the guayule patents in December 1996 and February 1998. The patents covered a process to extract hypoallergenic latex from guayule to make gloves and medical products for latex-sensitive persons, and to increase rubber yield by adding initiator isoprenes to their polymer chains.
Yulex Corp., the company that obtained the exclusive license from the USDA for the latex extraction process, has commercialized guayule latex through a co-branded wetsuit product line with Patagonia, according to the Yulex website.
"(Yulex is) bringing a sustainably sourced wetsuit to the action sports market for the first time to great marketplace acclaim," the website said.
Yulex also has entered into a non-exclusive technology transfer agreement with the Italian chemical producer ENI Versalis, which is scaling up guayule production in southern Italy, according to Jeff Martin, Yulex founder and CEO.
However, Yulex is concentrating on the production and marketing of Hevea rubber using its Yulex Pure purification process, Martin said.
"The company does have existing patents on guayule genetics and various extraction technologies which are current and maintained," he said.
The ARS recently has performed field trials not only with Yulex but also with Bridgestone, according to McMahan. Bridgestone's guayule commercialization project began in 2012, and in February 2018 the tire maker announced it had obtained a five-year, $15 million guayule research grant from the USDA National Institute of Food and Agriculture.
The ARS also collaborated with Cooper Tire & Rubber Co. in its five-year, $6.9 million Biomass Research and Development Initiative (BRDI) to develop guayule rubber for use in tires.
Other collaborators with Cooper included Clemson University, Cornell University and the guayule development company PanAridus L.L.C. The ARS also has collaborated with PanAridus on solvent extraction of guayule latex, according to McMahan.
Besides latex yield, the ARS has turned serious attention to the commercial possibilities of guayule resins and bagasse (pulp), McMahan said.
"It's more and more evident that for guayule to become sustainable, the co-products must be commercialized," she said. Resins have particular promise for use as an adhesive and a tackifier for tires, she said.
The ARS has 600 acres of guayule planted at its center in Maricopa, Ariz., according to McMahan. "Our field work happens at Maricopa," she said.
Cornish, who led the research behind the original guayule patents, now is endowed chair and Ohio scholar in bio-emergent materials at Ohio State University's Ohio Agricultural Research and Development Center in Wooster, Ohio.
She also is scientific adviser to American Sustainable Rubber Co. L.L.C., a hydroponic dandelion rubber company, and CEO of her own guayule development company, EnergyEne Inc.
Since leaving the ARS, Cornish has obtained a number of new patents regarding guayule, most of them assigned to EnergyEne.
One is for a process that greatly improves the efficiency of guayule latex extraction, she said. "It allows real-time adjustment of the centrifuge to match different latex concentrations," she said.
While interest in guayule remains high, commercialization will take time, according to Cornish.
"You can't convert 100 acres of plantings into a commercial product," she said. "When people ask me, 'When can I get guayule latex at commodity prices?' I answer, 'Not yet.' "
PanAridus CEO Michael Fraley said depressed prices for Hevea rubber have hampered the impetus for guayule commercialization, and 70 years of government assistance have not worked to achieve it.
"We're looking for additional investment," he said. "Hevea is still a monoculture, prices are depressed, and growers have no economic incentive to care for the trees.
"What raises the interest level is a disaster, which drives interest in alternatives," he said. "I'm ready to work on alternatives, but I need the funding to do that."
Meanwhile, McMahan said she still believes the original guayule patents can be put to commercial use.
"They still have huge potential," she said.