Ohio State University (OSU) researchers are making use of food waste to partially replace the petroleum-based filler used in manufacturing tires.
Rubber made with the new food waste fillers exceeded industrial standards for performance, the researchers contend.
As OSU’s Katrina Cornish explains, 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.
Cornish has spent years cultivating new domestic rubber sources, including a rubber-producing dandelion. Now she has a patent-pending method for turning eggshells and tomato peels into viable—and locally sourced—replacements for carbon black, a petroleum-based filler that American companies often purchase from overseas.
“The tire industry is growing very quickly, and we don’t just need more natural rubber, we need more filler, too,” Cornish explains. “The number of tires being produced worldwide is going up all the time, so countries are using all the carbon black they can make. There’s no longer a surplus, so we can’t just buy some from Russia to make up the difference like we used to.”
That’s why she and her team are getting eggshells and other food waste from Ohio food producers.
According to the USDA, Americans consume nearly 100 billion eggs each year. Half are cracked open in commercial food factories, which pay to have the shells hauled to landfills by the ton. There, the mineral-packed shells don’t break down.
The second most popular vegetable in the United States – the tomato – also provides a source of filler. Americans eat 13 million tons of tomatoes per year, most of them canned or otherwise processed.
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 highly stable at high temperatures and can also be used to generate material with good performance.
“Fillers generally make rubber stronger, but they also make it less flexible,” Barrera said. “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.”
Image credit: Kenneth Chamberlain, courtesy of The Ohio State University