ELOY, ARIZONA — I’m standing in a field in rural Arizona, watching migrant workers plant seedlings that will, in three years, grow into green bushes with tiny white flowers. When mature, they don’t look anything like the Southeast Asian hevea trees that produce more than 90 percent of today natural rubber, but in nature these guayule (“why-u-lee”) shrubs are the second best thing.

Dr. David Dierig has been refining guayule his whole working life.

Dr. David Dierig has been refining guayule his whole working life. (Photo: Jim Motavalli)

Bridgestone Americas, a branch of the world’s largest tire maker, is growing guayule in an experiment to see if it can be cost-effective to produce tire rubber like corn for ethanol or algae for biofuels. Since only about six to 10 percent of the plant (the bark and roots) can be made into rubber, Japan-based Bridgestone is going to have to harvest the whole plant, grind it up, and then separate out resin and woody material to be repurposed. Just what to do with these potential revenue streams isn’t clear yet, though diesel fuel and specialty chemicals are a possibility.

“Hundreds of plants produce natural rubber,” said Dr. David Dierig, section manager at Bridgestone’s 281-acre guayule farm in Eloy. “But only a few produce it in high quality.”

This tire was made from guayule in the 1980s — an earlier attempt to commercialize the process.

This tire was made from guayule in the 1980s — an earlier attempt to commercialize the process. (Photo: Jim Motavalli)

Rubber from the Texas native and desert-loving guayule isn’t a new idea. The Aztecs played games with balls made from guayule. It was extensively cultivated in Mexico for tire production beginning in 1905, and in California and Arizona before the Depression. World War II rubber shortages led to an emergency revival, and it was briefly cultivated in the 1980s by Firestone (now part of Bridgestone) and Goodyear in a project with the U.S. Department of Defense. But that effort ended in 1989. Guayule is just a wild crop today.

The conveyor will carry guayule plants for processing.

The conveyor will carry guayule plants for processing. (Photo: Bridgestone)

Guayule, as Texan as the armadillo, will thrive with very little water, but Dierig said it grows much more quickly and larger when it is irrigated. Cotton is one of the “five Cs” of the Arizona economy (climate is another one), and guayule will use far less water, Dierig said.

Guayule plants under cultivation in Eloy, Arizona.

Guayule plants under cultivation in Eloy, Arizona. (Photo: Jim Motavalli)

Earlier that day, I was in Mesa, Arizona, near Phoenix, with state politicians cutting a ribbon on Bridgestone’s 17,000-square-foot Biorubber Process Research Center and production facility. This is where they’ll study ways to maximize guayule’s commercial potential as an ingredient in tomorrow’s tires. Bridgestone won’t say how much it’s investing in its experimental guayule operations, but it pales before what will get spent if the unassuming bush actually gets produced in large-scale farming operations. Bridgestone would like to produce all of its tires from renewable and sustainable materials by 2050.

Right behind the center is a brand-new pilot-level plant that will within a month begin producing guayule rubber daily and forming it into 75-pound bales for testing. The plant uses solvents to separate the rubber from the biomass (also known as bagasse) and resin, but there’s no chemical waste — the hexane and acetone solvent is almost entirely recovered and reused. 

A guayule bale ready for processing.

A guayule bale ready for processing. (Photo: Jim Motavalli)

Guayule rubber is chemically almost identical to what comes out of Thailand, Malaysia and Indonesia, even though the production process is entirely different. The Asian industry is relatively stable, with prices up somewhat in the last few years, but Bridgestone’s Bill Niaura, director of new business development, said the company worries about depending so heavily on a single source for a product that really has no substitute. Regular passenger tires don’t need much natural rubber, but heavy-duty truck and airplane tires aren’t viable without a fair amount of it.

The rubber tree is actually native to Brazil, but only 3 percent of the world’s rubber comes from there now because of a tenacious leaf blight. Auto pioneer Henry Ford, who loved vertical integration, found out about leaf blight to his sorrow when he tried to grow rubber at an outlandish plantation called Fordlandia in the Brazilian jungle.   

The swimming pool at Fordlandia, Henry Ford's failed effort to grow rubber in the Brazilian jungle.

The swimming pool at Fordlandia, Henry Ford's failed effort to grow rubber in the Brazilian jungle. (Photo: Ford)

Other plants show potential for producing rubber, most notably the Russian dandelions that Bridgestone is also growing, but none would have comparable yields.

Back in the field, section manager Bob White shows us the minuscule seeds hidden inside guayule’s white flowers. Because this isn’t a commercial crop (at least not yet), the company can’t just buy guayule seeds; it has to painstakingly separate them from other plant material, and then use them to selectively breed the best plants.

Niaura admits that Bridgestone has a lot of work ahead, and it’s unlikely that commercialization will occur before the 2020s. But the company is definitely serious about growing rubber in the Arizona desert.

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Jim Motavalli ( @jmotavalli ) writes about cars, technology and the environmental world to anyone curious enough to ask.