Researchers report progress with NR alternates

AKRON—On one hand, there is guayule, the shrub native to the Sonoran desert that for 100 years has been the focus of efforts to make it a commercially viable source of natural rubber.

On the other, there is the flower variously known as Taraxacum kok-saghyz, Russian dandelion and “Buckeye Gold,” also known to be a rich source of rubber, and with a much wider potential range of cultivation than guayule.

Research scientists and tire manufacturers are heavily involved in the effort to make both guayule and TKS commercially successful, and they discussed their findings at the International Tire Exhibition & Conference in Akron Sept. 9-11.

The case for having alternates to Hevea brasilensis is obvious, according to Katrina Cornish, endowed chair and Ohio research scholar in bio-emergent materials at Ohio State University.

“We need alternative natural rubber sources for biodiversity and easing price volatility,” she said. Having a domestic source of NR also is extremely desirable, she said. But the rubber has to be useful in manufacturing, both in quality and quantity, for any plant commercialization program to succeed, she said.

“You can't just order it. You have to produce it,” said Cornish, a renowned expert in both guayule and TKZ. “You have to inspect it, process it and transport it. Someone is going to have to want to buy this.”

While polymers are officially the same, different polymers have different molecular structures and properties, according to Cornish. Comparing TKS and guayule, TKS rubber is much closer to the structure of Hevea, she said.

“Guayule makes an outstanding thin film polymer,” said Cornish, who during her tenure at the U.S. Department of Agriculture's Agricultural Research Service patented a method of making hypoallergenic latex from guayule. That patent was later assigned to Yulex Corp., where Cornish also worked.

“I'm a big proponent of guayule for medical products,” she said. “You can use guayule even if you have a Type I latex allergy.

“You can actually forget you're wearing a guayule glove, they're so comfortable,” she said.

But although guayule also can be used for tires, TKS—which Cornish and her associates rechristened “Buckeye Gold” during their agricultural research project at the Ohio Agricultural Research and Development Center in Wooster, Ohio—is perfect for tires because of its close resemblance to Hevea, she said.

On the other hand, TKS also contains many of the same proteins as Hevea, so it too has to be heavily washed and treated before being used in medical products, Cornish said.

“Guayule is semi-domesticated, but Buckeye Gold is lower down the curve,” she said. “Much greater yields are possible, but its great advantage is that it's an annual.” The OARDC has eight acres planted in TKS, she said.

Ford Motor Co., which uses substantial amounts of recycled rubber and other materials in several of its models, has achieved very promising results in its experiments with guayule and TKS, according to Janice Tardiff, elastomers technical expert at Ford.

Ford has experimented with guayule from Yulex, PanAridus L.L.C. and the OARDC in tire-related applications, as well as with TKS from the OARDC and with devulcanized rubber, according to Tardiff.

Devulcanized rubber didn't perform up to expectations, but the other materials produced encouraging results, she said. In a model tire tread, for example, Ford replaced 29 percent of the Hevea rubber in the tread with guayule.

The properties of the guayule rubber differed very little from those of Hevea, Tardiff said, but the tread rubber was a little soft compared with that of a typical tire. “Guayule may be more applicable to sub-tread material,” she said.

TKS will receive further testing once Ford receives more TKS rubber, Tardiff said.

TKS is native to Kazakhstan, but British Columbia has the ideal climate for growing the flower, according to Anvar Buranov, founder of NovaBioRubber Green Technologies L.L.C. NovaBioRubber has acreage near Kamloops, B.C., and TKS has thrived there, Buranov said.

TKS grows best at a temperature range between 10 and 25°Celsius, but dies at temperatures below -7°C, according to Buranov.

British Columbia has two growing seasons annually, he said, and growing costs in British Columbia should be only about 50 cents per kilogram of rubber produced—especially using NovaBioRubber's patented dry milling process, which Buranov said was cheaper and more environmentally friendly than any other extraction method.

TKS also is being studied closely in its native country, according to Kairat Uteulin and Serik Mukhambetzanov, director and deputy director of BioTech-TKS L.L.P.

Gathering TKS in Tien Shan, the Kazakh mountain range from where the flower emanates, Uteulin and Mukhambetzanov discovered three strains of the plant, which produce 16, 21 and 27 percent rubber respectively, they said.

From these, they created a bank of seeds that can be used for the creation of high-yielding TKS varieties, they said.

“Guayule at Warp Speed” was the title of the speech by Michael Fraley, president and CEO of PanAridus, and he left his audience in no doubt of what he meant: guayule commercialization for tire production, he said, is imminent.

“I am extremely passionate about what we are doing at PanAridus,” Fraley told the audience.

Hevea, according to Fraley, no longer can meet global natural rubber demand.

“There is probably no commodity produced in such volume that still has such antiquated methods of collection and processing,” he said. “Hevea has a very narrow clone, prone to leaf blight and other diseases.

“Because of volatility in supply and prices, Hevea is in a very precarious strategic situation,” he said. “We also have to worry about climate change, because Hevea is grown in tropical regions.”

Guayule is a 100 percent usable plant that can be used for its biomass, energy and resins as much as for its rubber, according to Fraley. PanAridus focuses on breeding and agronomics, and has developed some 300 types of the desert shrub, most of which have shorter growing periods than traditional guayule, he said.

The company has filed a patent for direct seeding, Fraley said. “You can plant seed to establish 20,000-40,000 acres in one growing cycle. This will be a tremendous cost savings.”

PanAridus also has four patents pending on rubber extraction, he said, and major tire manufacturers have validated the quality of its guayule rubber.

“We've received the rubber colonos-copy,” he said.