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Research Funding

Guayule Rubber Gets Ready To Hit The Road

Companies are looking to the desert shrub as an alternative to tropical rubber trees

by Alexander H. Tullo
April 20, 2015 | APPEARED IN VOLUME 93, ISSUE 16

Home On The Range
Credit: Bridgestone
Bridgestone is growing guayule at a research farm in Eloy, Ariz.

For the past century, tire manufacturers have sought alternatives to the natural rubber grown on Southeast Asian rubber plantations. Dependence on a single region for the critical raw material has made their supply chains vulnerable to blight, infestation, bad weather, political instability, and, in the 1940s, war.

When Japan cut off rubber supplies in World War II, the U.S. government had to act fast to establish a domestic synthetic rubber industry. The effort not only delivered rubber but also helped establish the modern petrochemical industry.

But there is no true substitute for the real, natural item. To this end, rubber producers have long tried to extract rubber from the guayule—pronounced why-yoo-lee—shrub (Parthenium argentatum), native to the arid southwestern U.S. Efforts to develop guayule, however, have been sporadic, flaring up in times of crisis and then vanishing just as fast.

During the war, the U.S. set up the Emergency Rubber Project to cultivate guayule. The war didn’t last long enough to sustain the program. Only a few hundred tons of rubber were produced from fields in California and wild shrubs in Texas before the project was discontinued (C&EN, March 29, 1948, page 926).

Big tire companies such as Bridgestone and Cooper Tire & Rubber Co. as well as little start-ups such as Yulex are now taking up the cause again. Seeing a payoff from diversifying their sources of natural rubber, they say they are committed to long-term research of ways to economically grow and extract rubber from guayule.

Natural rubber, known chemically as cis-1,4-polyisoprene, is as essential as ever. “A lot of synthetic work was targeted toward making a replacement for the natural product,” says Bill Niaura, director of new business development for Bridgestone Americas. “Those decades of work have shown we’re not that good yet.”

Natural rubber is still a must for truck and airplane tires. Niaura explains that natural rubber strain-crystallizes as a consequence of the stereoregularity of the polymer chain. As those stereoregular chains are pulled—such as when a plane’s tires slam into the runway for landing—they align. Microcrystalline structures form in the rubber, adding reinforcement. “The higher loading that a tire sees, the more natural rubber it is going to have,” Niaura says.

Guayule is 5 to 10% cis-1,4-polyisoprene by weight. But it isn’t as easy to extract rubber from the shrubs as it is from traditional Hevea brasiliensis rubber trees. Latex flows freely within channels in rubber trees. Workers simply tap the plant to let the latex flow into buckets.

In guayule, the rubber is trapped within the plant’s cells and must be extracted after the plant reaches maturity, which takes two or three years. “You cut at the base, as you would with asparagus, and allow the rest of the plant to regrow,” says Colleen M. McMahan, a research chemist at the U.S. Department of Agriculture’s Agricultural Research Service (ARS).

The harvested plant is ground, and the rubber is extracted in one of two ways, according to McMahan. In the solvent-based process, organic solvents dissolve the rubber and are then stripped off, leaving a hard rubber, suitable for tires.

In the aqueous process, which was developed at ARS, the plant matter is run through a centrifuge in an alkali solution. The rubber particles, McMahan says, rise to the top. The product is a latex emulsion, used for “dipped” products such as gloves and balloons.

And it’s such products that take advantage of a key difference between guayule and hevea rubber. Latex from rubber trees is about 2% proteins, some of which cause allergies. Guayule rubber doesn’t contain these proteins.

This quality was the genesis of San Diego-based Yulex, says Chief Executive Officer Jeffrey A. Martin, who founded the company in 2000. Because Yulex was interested in latex products such as gloves and catheters, the company licensed ARS’s process.

Synthetic polymers, such as polyurethane, are currently used to make allergy-free gloves and condoms, but Martin says synthetics lack the “comfort and creature features” of natural-latex-based products. Glove giant Ansell took an equity stake in Yulex as part of a deal to explore this market.

To date, though, Yulex’s commercial hit is the R2 wetsuit, available since 2013 from Patagonia. In this case, guayule rubber is a natural alternative to polychloroprene. Moreover, Martin says, it is lighter and more flexible than the material it is replacing. “That’s huge if you’re a surfer,” he notes.

Yulex makes the latex for the suit, as well as for test-marketing other products, at its pilot plant near Phoenix. Yulex and partners grow guayule in Arizona and Italy.

The company’s future, according to Martin, lies in collaborating with other firms to scale up its technology. One is Versalis, the chemical arm of the Italian oil giant Eni, which plans to build a guayule rubber facility in arid Southern Europe. The guayule crop, grown with Yulex seeds, has already been planted in the region. Versalis hopes to sell the rubber to the Italian tire maker Pirelli.

Indeed, the tire companies involved with guayule have more than niche products such as gloves in mind. They want a large-scale source of natural rubber to compete with hevea rubber, some 11.4 million metric tons of which was consumed globally in 2013, according to the Singapore-based International Rubber Study Group.

Even when tapped by hand from the veins of rubber trees in Thailand and Malaysia, natural rubber can be pretty cheap: $1,710 per metric ton, compared with $2,630 for styrene-butadiene rubber made in the U.S. last year, according to the study group.

Low prices killed earlier guayule programs. “Many of those efforts failed just on the basis that hevea was so inexpensive,” Bridgestone’s Niaura says.

Nevertheless, tire companies have an incentive to press on because they crave supply diversity. “If you look at the future, the beautiful picture would be rubber coming from tropical regions from hevea trees, from arid regions from guayule, and from temperate climates from something like Russian dandelion,” Niaura says.

Guayule must overcome some obstacles to hit the big time. One is finding value for the 95% or so of the guayule plant that isn’t polyisoprene. This is a focus of the work Bridgestone is undertaking at a process research center it opened last September in Mesa, Ariz.

Niaura envisions using the woody material, the bagasse, as a fuel or as a feedstock for cellulosic biofuels. The firm is also exploring markets for the terpene resins that make up roughly 10% of the guayule plant.

The companies trying to commercialize guayule say the most important factor is improving its agronomics—the economics of growing it. Previous efforts to cultivate guayule never fully tamed the wild domestic shrub.

Yulex has tested the germplasm USDA was sending out to research programs around the world. The company found that USDA’s seed could be traced to just five plants that were part of the WWII guayule program. “It is virtually impossible to make any meaningful progress with traditional breeding methods without proper diversity,” Martin says.

The company scoured universities, labs, and private collections to boost the genetic material for its breeding program. It is now testing guayule hybrids in arid regions around the world.

Yulex isn’t the only company that has been wrestling with agronomics. In 2013, Bridgestone planted a 281-acre farm in Eloy, Ariz., where it breeds and tests crops. Niaura says the company hopes to have commercial-scale cultivation and processing under way by the mid-2000s.

Cooper Tire & Rubber Co. is leading a consortium that includes ARS, the guayule research start-up PanAridus, and Arizona State University. The team received a $6.9 million federal grant to define the guayule genome and to plant, irrigate, and harvest the shrub.

“We think this union has the potential to be the difference maker,” says Chuck Yurko­vich, Cooper’s head of R&D. The key to a successful effort, he says, is consistent funding to render it invulnerable to the ups and downs of the rubber market. The company, he notes, has already tested guayule-based tires and found performance to be equivalent to their hevea-based counterparts.

Yulex’s Martin argues that the foundational work is nearly complete and that the guayule industry is ready to take the next step. “We have solved all the riddles with respect to processing technology, performance of the material, and finally the question of genetics,” he says. “Now it is just an issue of scale.”  



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Robert Buntrock (April 20, 2015 3:57 PM)
A number of oil and petrochemical companies, spurred to investigate alternative fuel sources due to crude supply disruptions, did research in the '70s and '80s on latex producing plants as sources of hydrocarbons. Guayule was one as were euphorbias, milkweed, dandelions, and jojba. I'm not sure how much was published (falling crude prices led to suspension of the research) but a literature search could turn up some articles or patents. Some of the original work dates back to Thomas Edison who considered himself a chemist and did a fair amount of research in the area at his winter home and lab in Ft. Meyers FL where he grew 5000 varieties of tropical plants. He was induced to do the research by his friend and winter neighbor Harvey Firestone who's source of rubber latex from Brazil was impeded by German sub warfare in WW I.
Robert Buntrock (April 20, 2015 3:58 PM)
A number of oil and petrochemical companies, spurred to investigate alternative fuel sources due to crude supply disruptions, did research in the '70s and '80s on latex producing plants as sources of hydrocarbons. Guayule was one as were euphorbias, milkweed, dandelions, and jojoba. I'm not sure how much was published (falling crude prices led to suspension of the research) but a literature search could turn up some articles or patents. Some of the original work dates back to Thomas Edison who considered himself a chemist and did a fair amount of research in the area at his winter home and lab in Ft. Meyers FL where he grew 5000 varieties of tropical plants. He was induced to do the research by his friend and winter neighbor Harvey Firestone who's source of rubber latex from Brazil was impeded by German sub warfare in WW I.
Jeff Martin (April 20, 2015 5:16 PM)
Robert - is this your bio?

Buntrock has an extensive scientific background from which to draw. He is a semiretired chemist who does chemical information consulting and book reviews under the company name Buntrock Associates. He graduated with a B.S. in chemistry from the University of Minnesota in 1962, and he earned a Ph.D. in chemistry from Princeton University in 1967. Before starting his company, Buntrock worked in industry for nearly 30 years at Air Products & Chemicals and Amoco Corp. A successful researcher, he holds three patents and has almost 200 publications.

Jeff Martin
Elizeu Santos (April 25, 2015 8:25 AM)
Since Heve has proven qualities regarding natural rubber production and since Brazil has a lot of land available to grow hevea in places where microciclus can't damage the plantation, why not to invest in Brazil planting rubber trees?
alphax (June 6, 2015 1:30 PM)
Climate change, for one. The socioeconomic instability that comes from climate change is another.

Hevea trees' production declines above a temperature threshold.

It's also a good thing to have alternative supplies to the monoclonal crops such as the hevea in case something like the microcyclus fungus appears.
William T. Winter (December 10, 2015 12:15 AM)
Actually this is a good question. Natural rubber from Hevea b. only grows in tropical climates, Brazil and SE Asia in particular. Between World War I and World War II armies in the major industrialized countries made the transition from animal drawn vehicles to motorized vehicles and airplanes which use rubber tires. The long supply lines bringing rubber to the countries waging war were infested with submarines. As a result those countries invested in crash programs leading to the creation of synthetic rubber, which still does not match the performance of the natural material. So there continues to be interest in cis-isoprene producers such as guayule, Russian dandelion, and others that can be grown in temperate climates.
Raymond Sumo (June 9, 2016 2:13 PM)
I just heard about the Guayule plant at a Bioenergy and Feedstocks Conference this week. Will your Yulex seedings grow in Africa or do you have any on going trials in Africa?
Richard Lange (April 24, 2015 2:17 PM)
Back in the mid-70's I was working in the Research Division of a major lubricant company, and they were concerned about a shortage of mineral oil stocks. They had convened a brainstorming meeting of the various group leaders to discuss the possibility of using guayule oil as a base-stock in our engine oils, and decided that it would be too expensive. After an hour of fruitless debate, I suggested to the research director that we should just buy a few thousand acres of arid land in the Southwest, grow guayule, then research and market the expensive oils and extracts commercially for profit. After all, the director had told us to "think outside the box" at the meeting. That suggestion earned me a major amount of ridicule and hazing. And that is why I particularly enjoyed reading this article, which I intend to send to several of my former associates who were at that meeting!
Jorge Romero (April 25, 2015 1:40 AM)
Do you now something about the research that took place during the 70´s in Mexico?
Dan Swiger (April 25, 2015 10:57 PM)
When a crop has 95% left over to find a home for makes this one of the toughest obstacle overcome and two to three years to reach maturity.

Guayule can only be grown in semiarid regions or four states in the United States is another set of obstacles.

I see articles that indicated Yulex was founded by Daniel R. Swiger in 1997 and negotiated a license agreement with the USDA

William T. Winter (December 10, 2015 12:20 AM)
I did not read the Buntrock comment to completion before submitting mine. There is sufficient duplication that perhaps you need not publish mine,which I just submitted.
Henry Parsons (June 19, 2016 6:43 PM)
My father (deceased) did some work on the guayule rubber project during WWII, and testified before Congress about guayule (perhaps as part of the Emergency Rubber Project ?).
I regret that I didn't learn any details about his work with guayule when he was alive.
Sally Drone (July 24, 2016 10:10 PM)
My father was also involved in the guayule project during WWII. He worked for the US Forest Service. I remember a very hard rubber ball that he brought home for my sister. I was born in Kings City while he was working near Salinas, Ca. on the project. I am glad to find this article and the comments about this product to better understand what my father was doing during the war.
Earlier he worked in Nebraska on the shelterbelt project after the devastating dust bowl period. That's where my sister was born.
Dr. Glenn H. Kageyama (December 16, 2016 5:57 PM)
In the 1940's about 30 Japanese_Americans who were interred at the Manzanar Relocation Center during WWII volunteered to work with Dr. Robert Emerson (Professor of Plant Physiology, Cal Tech)on cultivating, hybridizing, and improving the mechanical and chemical extraction of a high quality rubber from Guayule. They produced a very high quality rubber that was even better than Hevea Tree rubber, proving for the first time that Guayule had the potential for being a viable source of high quality rubber that could be grown on marginal semi-arid lands. They accomplished this on a very marginal budget using jelly jars, washing machine motors, and whatever labware and chemicals Dr. Emerson was able to provide.
Jacinto Gyuevara (March 8, 2017 11:38 PM)
Does anyone know of any seed vendors of "Guayule" (Huei-olli which means "big rubber")? Would this plant grow in the relatively low elevation and humidity of San Antonio, Texas? High altitude/dry clime plants such as Creosote bush and Sacred Sage do NOT survive San Antonio's cold, wet winters.

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