Researchers at Ohio State University say they have discovered that food waste can partially replace the petroleum-based filler that has been used in manufacturing tires for more than a century.

In tests, rubber made with the new fillers exceeds industry standards for performance, which may ultimately open up new applications for rubber.

As Katrina Cornish explains it, the technology has the potential to solve three problems: It makes the manufacture of rubber products more sustainable, reduces American dependence on foreign oil, and keeps waste out of landfills.

Researchers developed a technology for incorporating food waste into rubber.Researchers developed a technology for incorporating food waste into rubber.Cornish, an Ohio Research Scholar and Endowed Chair in Biomaterials at Ohio State, has spent years cultivating new domestic rubber sources. Now she has a method for turning eggshells and tomato peels into viable—and locally sourced—replacements for carbon black, a petroleum-based filler.

About 30% of a typical automobile tire is carbon black; it’s the reason tires appear black. It makes the rubber durable, and its cost varies with petroleum prices.

As a solution to combat both the lack of a carbon black surplus and to create a more sustainable product, her team has collected eggshells and other food waste from Ohio food producers.

Tomatoes also provide a source of filler, the researchers found. Commercial tomatoes have been bred to grow thick, fibrous skins so that they can survive being packed and transported long distances. When food companies want to make a product such as tomato sauce, they peel and discard the skin, which isn’t easily digestible.

Cindy Barrera, a postdoctoral researcher in Cornish’s lab, found in tests that eggshells have porous microstructures that provide larger surface area for contact with the rubber, and give rubber-based materials unusual properties. Tomato peels, on the other hand, are stable at high temperatures and can also be used to generate material with good performance.

According to researchers, fillers generally make rubber stronger, but they also make it less flexible. Researchers found that replacing different portions of carbon black with ground eggshells and tomato peels caused synergistic effects—for instance, enabling strong rubber to retain flexibility.

The new rubber doesn’t look black, but rather reddish brown, depending on the amount of eggshell or tomato in it. With doctoral student Tony Ren, Cornish and Barrera are now testing different combinations and looking at ways to add color to the materials.

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