Domestic source of guayule close to development

HILTON HEAD, S.C.—An alternative, sustainable domestic source of natural rubber may be as little as a decade away, thanks to intensive research by Bridgestone Americas Inc., a Bridgestone Americas executive said at the 31st annual Clemson University Global Tire Industry Conference.

Bill Niaura, Bridgestone Americas director of new business development, spoke at the conference held April 15-17 at Hilton Head, updating the audience on his company's efforts to commercialize guayule, a desert shrub native to Mexico and the southwestern U.S.

“Developing guayule on a commercial basis is a huge challenge,” Niaura said. “There is no existing U.S. natural rubber industry. We are starting on that journey, and there are technical challenges that need to be addressed.”

Bridgestone Americas dedicated the Bridgestone Biorubber Process Research Center in Mesa, Ariz., last September, about a year after it opened its Agro Operation Guayule Research Farm in Eloy, Ariz. The farm provides rubber for the pilot guayule processing plant at the research center, with pilot-scale guayule rubber production planned for this year.

Bridgestone is developing guayule because NR sourcing as it exists now is a chancy enterprise, according to Niaura.

“Natural rubber is our single largest raw material purchase, accounting for more than 25 percent,” he said. “But it has a poor business model as far as supply is concerned. Hevea trees are cloned, genetically identical plants, genetically susceptible to the same diseases.”

The narrow geographic distribution of Hevea threatens supply instability between political unrest, climate change and an uneven supply-demand balance, Niaura said.

“It's a market-based commodity that has a huge impact on profitability in a low-margin business,” he said.

There are more than 2,000 plants besides Hevea that produce rubber latex, but by far the most promising are guayule and the Russian dandelion, Niaura said.

While both guayule and Russian dandelions are promising NR sources, Bridgestone believes guayule is the better bet, he said, adding that the company has a history with the cultivation of guayule, and lots of data on the shrub.

“Also, there's a problem with dandelions—how do you keep weeds out?” he said.

Guayule has been harvested in the U.S. since pre-Columbian times, when Native Americans chewed its sap to make balls for their games, according to Niaura.

At the turn of the 20th century, several companies along the Rio Grande harvested wild guayule for rubber. However, the wild plants were depleted rapidly, and the beginning of the Mexican Revolution forced the guayule companies to close.

There was some production of guayule rubber in California and Arizona in the 1920s by a company called Intercontinental Rubber Co., Niaura said. But the biggest guayule project before the 1980s was the Emergency Rubber Project during World War II, when government researchers planted 32,000 acres of the shrub in Arizona and Texas, he said.

Unfortunately, that acreage was disked under when the war ended, because the government decided to back the development of synthetic rubber instead.

According to Niaura, that was probably an unfortunate decision.

“Natural rubber is an indispensable material,” he said. “Our industry has been trying since World War II to reproduce it synthetically, but we haven't succeeded.”

Firestone Tire & Rubber Co., the predecessor of Bridgestone Americas, gained major experience with guayule when it joined the U.S. Department of Defense and the Gila River Indian Community in a guayule development project in Sacaton, Ariz., in the 1980s.

“Gila River was the basis of the data showing the validity of guayule as a viable alternative source of natural rubber,” Niaura said.

Bridgestone's research into the guayule plant concentrates on plant genetics, process quality and rubber yield, he said.

Because different guayule strains are so diverse—the plant can reproduce both sexually and asexually, depending on variety—plant breeding is especially difficult, Niaura said. Yet this same variety assures the vitality and resilience of the guayule plant, he said.

Guayule is only 5 percent latex by weight, so Bridgestone must concentrate on finding markets for the shrub's pine tar-like resins and the bagasse, or woody part of the plant, to make it commercially viable, he said.

“We have to find the best value for those products,” he said. “Energy is the low-hanging fruit, either for someone else's use or onsite. It's easy to do, but rather low on the profitability rung.”

Using guayule bagasse and resins to make composite boards is a promising application, according to Niaura. “Termites will starve before they eat boards like that,” according to Niaura.

Firestone Natural Rubber Co., the branch of Bridgestone Americas that runs the company's Hevea plantation in Liberia, has no involvement in the guayule program, he said. Bridgestone is not considering the creation of anything like a guayule plantation, but instead hopes to attract independent farmers to grow the crop.

“Guayule agriculture is feasible, but it's a lot of work to turn it into a true agribusiness,” Niaura said. “A lot of hard labor is involved in growing the crop, but it yields a free-flowing latex that is easy to collect.”

The various challenges in developing guayule means it will be the 2020s at the earliest before it's used for tires in wide distribution, he said.

Bridgestone's ultimate goal, however, is to replace 30 percent of the Hevea content in its tires with guayule rubber, he said.