Scientists Make Tire Filler From Eggshells, Tomatoes

It’s not exactly like using refrigerator leftovers, but Ohio State University researchers say raw material for tires could originate at a farm before reaching the factory.

They have found a way to partially replace the petroleum-based filler that has been used in manufacturing tires for more than a century with food waste.

During tests, rubber made with the new egg and tomato fillers exceeded industrial standards for performance

Ohio Research Scholar Katrina Cornish, Endowed Chair in Biomaterials at the university, says the technology potentially could solve three problems by making the manufacture of rubber products more sustainable, reducing American dependence on foreign oil and keeping waste out of landfills.

Cornish has spent years cultivating new domestic rubber sources, including a rubber-producing dandelion.

She now has a patent pending for a method of turning eggshells and tomato peelings into viable – and locally sourced – replacements for carbon black, the petroleum-based filler U.S. companies often purchase from overseas.

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.

Cornish says carbon black is getting harder to come by. But the tire industry is growing quickly and manufacturers need not only more natural rubber but also more filler.

“The number of tires being produced worldwide is going up all the time, so countries are using all the carbon black they can make,” Cornish says in a statement. “There’s no longer a surplus, so we can’t just buy some from Russia to make up the difference like we used to.”

The industry also needs to become more sustainable and that’s where the university project comes in.

Cornish and her team are obtaining eggshells and other food waste from Ohio food producers. “We’re not suggesting that we collect the eggshells from your breakfast,” she says. “We’re going right to the biggest source.”

That would be the poultry industry.

Americans consume nearly 100 billion eggs each year and half of them are cracked open in commercial food factories. The operators pay to haul mineral-packed shells by the ton to landfills where they don’t break down.

Tomatoes are the second-most popular vegetable in the U.S., with Americans eating 13 million tons a year.

Most of them are canned or otherwise processed and 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.

Postdoctoral researcher Cindy Barrera found in tests at Cornish’s laboratory that eggshells have porous microstructures that provide a larger surface area for contact with the rubber, and give rubber-based materials unusual properties. Tomato peels are highly stable at high temperatures.

Barrera says fillers generally make rubber stronger, but they also make it less flexible.

“We 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,” she says.

The new rubber doesn’t look black, but rather reddish-brown, depending on the amount of eggshell or tomato in it. The research team is testing different combinations and looking at ways to add color to the materials.

Ohio State has licensed the technology to Cornish’s company, EnergyEne, for further development. “We may find that we can pursue many applications that were not possible before with natural rubber,” she says.