Cooper: guayule viable as NR/SR substitute in tires

Pearsall, Texas — Cooper Tire & Rubber Co. researchers have determined that guayule rubber is a viable substitute for natural and synthetic rubber in building tires and could start using it immediately if sufficient material was available at a reasonable price.

Cooper is basing its conclusions on research it conducted over the past five years under the auspices of a $6.9 million Biomass Research and Development Initiative (BRDI) grant that included consortium partners, including Clemson University, Cornell University, PanAridus and the Agricultural Research Service of the US Department of Agriculture (USDA-ARS).

"Based on our findings, Cooper could use guayule rubber in tire production tomorrow if enough material was available to meet our production needs at a competitive price," Chuck Yurkovich, Cooper's senior vice president of global research and development said.

"To make this happen, the combined effort of government, agriculture and industry is needed to grow the plants and create large-scale manufacturing operations to produce the rubber for use in the tire industry," he added.

As part of the project, Cooper built more than 450 trial tires, replacing various tire components made with Hevea and synthetic rubber with those made with guayule and testing each for overall performance,

Yurkovich said. "With knowledge gathered from these builds, we created the industry's first all-guayule concept tires and with them conducted rigorous lab and road tests that provide verifiable performance results."

These tires were found to have overall performance at least equal to tires made with Hevea and synthetic rubber, Cooper said.

Notably, the tires performed significantly better in rolling resistance, wet handling and wet braking than their conventional counterparts, the tire maker said. Cooper recently presented a report on the grant — "Securing the Future of Natural Rubber: an American Tire and Bioenergy Platform from Guayule" — during a wrap-up meeting of the public-private sector at its Tire & Vehicle Test Center near Pearsall, Texas, where consortium members participated in a ride and drive on the guayule concept tires.

"The results of this grant have been groundbreaking," Yurkovich added. "Never before has it been proven that guayule is a viable source of domestically produced natural rubber for the tire industry. However, through the combined effort of industry, government and academia, the BRDI team has unequivocally demonstrated just that."

Consortium member Clemson University reported the completion of a Life Cycle Analysis (LCA) to quantify the environmental impact of producing tires from guayule, including materials, energy and emissions from raw material procurement to end of life.

"Through our LCA, we found that the 100-percent guayule-based concept tire had between 6- to 30-percent lower emissions in 10 different life-cycle environmental and energy-impact categories compared with a conventional tire," said Amy Landis, professor, Glenn Department of Civil Engineering, and Thomas Hash an endowed chair, at Clemson University.

"This model can also be used in the future to continue to quantify the environmental impacts of guayule for tire commercialization as it is impacted by factors such as agricultural yield and farming efficiency, the identification and use of coproducts, and improved guayule-tire rolling resistance," she added.

In addition, USDA-ARS, which earlier in the BRDI grant cycle completed an extensive irrigation study of guayule, reported the completion of a web-based tool for farmers to access an irrigation model online. The model will allow those growing guayule to use research data to manage irrigation water usage for maximizing yields while controlling costs.

Cooper said its guayule tires performed better in rolling resistance, wet handling and wet braking than their conventional counterparts.

"Guayule is cultivated in semi-arid regions, so sustainable use of irrigation water resources is paramount," said Colleen McMahan, research chemist, ARS, Western Regional Research Laboratory.

"This study clearly showed large productivity improvements when sub-surface drip irrigation was used versus surface irrigation," she said, "which may help justify investment in more water-efficient systems for guayule agriculture."

ARS also reported on its work under the grant to sequence the guayule genome. This effort was geared to position the crop to benefit from modern genomics tools developed by the Cornell University consortium partners.

"The genomics efforts at Cornell, which include the most detailed genetic characterization of the entire publicly available guayule collection to date, lay the foundation for genomics-assisted breeding of the plant to accelerate improvements in terms of yield, resistance to disease and pests, cold tolerance and other factors," said Michael Gore, Liberty Hyde Bailey professor and associate professor, Plant Breeding and Genetics Section, School of Integrative Plant Science, Cornell University.

"The ARS and Cornell consortium partners ensured the genomics tools and information are publicly available in order to facilitate the rapid development of the guayule plant as a viable crop."

Other significant accomplishments over the five-year grant cycle included:

- PanAridus, the project's raw material supplier, achieved success in manufacturing rubber using improved strains of guayule, producing rubber in quantities never before achieved for use in modern tires. Cooper and PanAridus also improved the rubber extraction process from guayule plants.

- USDA-ARS pioneered direct seeding methods and agronomics.

- Cooper, PanAridus and USDA-ARS worked closely to identify key variables impacting rubber quality. Controlling these factors during the rubber manufacturing process resulted in compounds with properties that are similar to Hevea natural rubber.

- USDA-ARS completed an irrigation study of guayule that compared surface irrigation and subsurface drip irrigation to determine the most effective method to drive higher rubber yield per acre. The study found that drip irrigation provided an enormous benefit over other irrigation techniques and led to improved yields.