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Study: Guayule tyre performance “at least equal” to conventional rubbers

Cooper Tire & Rubber Company and its consortium partners have completed their five-year research project into the potential of guayule rubber as a replacement for Hevea natural rubber in tyres. A report on their work was recently presented at the public-private sector consortium’s wrap-up meeting held at the Cooper Tire & Vehicle Test Center near San Antonio, USA.

Working as the lead entity in the consortium, Cooper Tire & Rubber announced at the meeting that its scientists have produced several sets of concept passenger car tyres in which all natural and synthetic rubber was replaced by guayule natural rubber. The 100 per cent guayule-based concept tyres wereextensively evaluated by a Cooper technical team, with rigorous wheel and road tests performed as part of the evaluation.

The Cooper test team found the tyres to have “overall performance at least equal to tyres made with Hevea and synthetic rubber.” Notably, the tyres performed significantly better in rolling resistance, wet handling and wet braking than their conventional counterparts.

“Cooper built more than 450 tyres, replacing various tyre components made with Hevea and synthetic rubber with those made with guayule, and testing each for overall performance. With knowledge gathered from these builds, we created the industry’s first all-guayule concept tyres and with them conducted rigorous lab and road tests that provide verifiable performance results,” shares Chuck Yurkovich, Cooper’s senior vice-president of global research and development. “Based on our findings, Cooper could use guayule rubber in tyre production tomorrow if enough material was available to meet our production needs at a competitive price. 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 tyre industry.”

Guayule is particularly interesting to Cooper Tire & Rubber as the shrub grows primarily in the southwestern United States, and its use as a raw material in tyre manufacture would reduce or eliminate Cooper’s dependency upon imported natural rubber. The tyre maker could potentially supply its production with guayule rubber from its own plantations.

The consortium, which also includes Clemson University, Cornell University, PanAridus and the Agricultural Research Service of the US Department of Agriculture (USDA-ARS). Their research was carried out under a five-year, US$6.9 million Biomass Research and Development Initiative (BRDI) grant, titled “Securing the Future of Natural Rubber – an American Tire and Bioenergy Platform from Guayule.”

LCA, irrigation studies, genome sequencing

During the meeting at the Cooper Tire & Vehicle Test Center, Clemson University reported the completion of a Life Cycle Analysis (LCA) to quantify the environmental impact of producing tyres from guayule including materials, energy and emissions from raw material procurement to end of life. “Through our LCA, we found that the 100 per cent guayule-based concept tyre had between six to 30 per cent lower emissions in ten different life cycle environmental and energy impact categories compared with a conventional tyre,” said Clemson University’s Amy Landis. “This model can also be used in the future to continue to quantify the environmental impacts of guayule for tyre commercialisation as it is impacted by factors such as agricultural yield and farming efficiency, the identification and use of coproducts, and improved guayule-tyre rolling resistance.”

In addition, USDA-ARS, which earlier in the BRDI grant cycle completed the most extensive irrigation study of guayule ever conducted, reported the completion of a web-based tool that gives farmers online access to an irrigation model. The model allows those growing the guayule plant to utilise research data to manage irrigation water usage for maximising yields while controlling costs. “Guayule is cultivated in semi-arid regions, so sustainable use of irrigation water resources is paramount,” said Colleen McMahan, research chemist from the ARS Western Regional Research Laboratory. “This study clearly showed large productivity improvements when sub-surface drip irrigation was used versus surface irrigation, 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 consortium partner Cornell University.

“The genomics efforts at Cornell, which include the most detailed genetic characterisation 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 from Cornell University’s School of Integrative Plant Science. “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 include:

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 tyres. 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.

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