MESA, Ariz.—Bridgestone Corp.'s recent disclosure that it has begun building tires with guayule-based rubber in place of Hevea natural rubber components is important, a top Bridgestone executive said, but only part of what the company is doing to make the desert shrub a commercial crop.
“The release of the new tires is a milepost in a long and complicated story,” said Bill Niaura, director of new business development for Bridgestone Americas, referring to passenger tires built at Bridgestone Corp.'s research facility near Rome early this summer and later at Bridgestone headquarters in Tokyo.
“We made the rubber using a process that fully visualizes how we'd expect a commercial guayule facility to operate,” Mr. Niaura told Tire Business.
The new tires—in which guayule rubber fully replaced Hevea rubber in the tread, sidewall, bead fillers and other parts of the tire traditionally made from NR—were unveiled Oct. 1. That's a little over a year after Bridgestone opened its Biorubber Process Research Center in Mesa.
The tire maker also operates a 281-acre research farm, the Agro Operation Guayule Research Farm in Eloy, Ariz., which is devoted to various aspects of cultivating guayule, a desert shrub native to Mexico and the southeastern U.S.
Building the tires was less important than creating the process that allowed them to be built, according to Mr. Niaura.
“It's a continuous process, not a batch process—the materials go in one end, and the product comes out the other,” he said. “We have no firm date for building the next guayule tires, but it's not a question of what's next—it's a series of nexts. We're learning how to influence the process.”
One of the major parts of that process is developing guayule rubber into a commercial product, Mr. Niaura said.
This is an even more complex undertaking than it sounds because there are many different types and grades of guayule. There are many different grades of Hevea rubber, with different properties that make each appropriate to a certain part of a tire, and the same is true of guayule rubber, he said. In any case, further research and development is needed in this area.
“We had some head start in this research, because we know how guayule behaves,” he said, “but it too is an ongoing process. I would expect there will be a need at some point to develop international standards for guayule rubber. There will be many different grades of guayule rubber, and also many different guayule rubber producers.”
Research on guayule plants is ongoing in many different areas, including germplasm, yield and methods of seeding, according to Mr. Niaura. Bridgestone has planted guayule fields all across Arizona, at varying altitudes and in different soil and moisture conditions, to determine which strains do best under which growing conditions, he said.
Genetics and environment are crucial factors in cultivating guayule, according to Mr. Niaura.
“There are so many different properties to guayule shrubs—disease tolerance, salt tolerance, cold tolerance, plant architecture,” he said. “These traits are being tracked and managed through our breeding program.”
Research and development of the resins and bagasse that are byproducts of guayule processing have become crucial in the viability of guayule as a cash crop, especially in light of falling prices for NR.
“Bagasse is probably more important than resins because of its sheer volume,” he said.
Bridgestone is examining different technologies for turning bagasse and resins into value-added products, according to Mr. Niaura. On the low end, bagasse has BTU value as a fuel, though probably not enough in today's market to make it viable, he said.
Construction materials are a better possibility, he said, as is creating oil and diesel fuel through pyrolysis and other means.
“We have three or four major efforts on bagasse going on right now,” Mr. Niaura said.
At the dedication of the research center last year, Mr. Niaura said Bridgestone planned further scaling-up of the pilot plant in 2016, toward a goal of making guayule commercially viable by the early 2020s. Those plans are still on track, he said.
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