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Sustainable Rubber is No Stretch

Honored Contributor
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Contributed by Ashley Baker, Research Assistant, ACS Green Chemistry Institute®

The list of companies joining the race towards sustainable rubber is growing. From startups to global chemical manufacturers, there’s a widespread push to develop high quality rubber that isn’t sourced from petroleum. Fluctuating oil prices, growing pressure to be sustainable, and virtually no domestic means of producing natural rubber are all fueling the search for a reliable, long-term solution.

Natural rubber and synthetic rubber each have their pros and cons. For example, most of the world’s natural rubber comes from Hevea brasiliensis plants, often called rubber trees, in Southeast Asia. This means there’s little to no geographic diversity in where natural rubber is sourced. On the other hand, natural rubber offers unequaled properties such as its ability to reinforce tires under the pressure of trucks and airplanes (Tullo).  New technologies for producing rubber focus less on which type is “better” and more on how to make the production of durable rubber more sustainable, efficient and cost-effective.

Natural Rubber

11055-guayule-plants-pv.jpgAlternative plant sources of rubber are gaining traction, and a little desert shrub has garnered lot of press. On October 1st, the Bridgestone Corporation announced the first-ever tires made entirely from guayule-sourced rubber. The guayule plant is native to the southwestern United States and northwestern Mexico, and this renewable source is being grown commercially for its 5-10% natural rubber content (cis-1,4-polyisoprene) (Tullo).  The ability to grow the plant in the U.S. is significant; it offers a uniquely local solution to natural rubber.

The percentage of latex in guayule is low; moreover, much of the plant, and therefore the resources that go into growing the plant, becomes waste. Yulex Corporation, a small company in Arizona, hopes to change that. Yulex has an extensive guayule breeding program and plant genomics research facility, projects enabled in part by a $6.9 million U.S. Department of Agriculture Grant (Fikes). Their hope is to use these tools and advancements in biotech to improve the plant’s rubber yield, making the harvesting process more efficient and cost-effective (Metz).

Guayule isn’t the only plant that’s being bred for rubber production. At the Fraunhofer-Gesellschaft, dandelions are being investigated for their natural latex output, but they aren’t expected to provide the world’s supply of rubber by themselves. Like hydroelectric, geothermal and other sources are combined to provide renewable energy, dandelions could play one part in sustainably meeting the world’s growing demand for rubber.

Synthetic Rubber

Even with a wider variety of natural sources, there is still a need for synthetic rubber which is used in a range of products from shoes to medical equipment. Perhaps the most exciting development in synthetic rubber is the role biosynthesis might play in its production. A partnership between LanzaTech, a biotech firm, and a global polymer and fiber producer, INVISTA, could drastically change how synthetic rubber is made.

Butadiene is a key intermediate in the production of synthetic rubber and nylon. Rather than sourcing it from petroleum, this collaboration focuses on an innovative alternative: biotechnology that converts industrial waste gases like carbon monoxide into valuable butadiene. INVISTA and LanzaTech plan to commercialize this biosynthetic route to butadiene early next year. Not only does this technology enable renewable intermediates to synthetic rubber, it also creates value from what would otherwise be waste.

As with any industry, it’s exciting to see companies innovating to be more sustainable. With new tools, facilities and emergent biotech to develop alternative materials and renewable sources, rubber manufacture – a seemingly unlikely field – seems headed toward a much greener future.

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