Eggshells and tomato peel could be used to make tyres
Researchers have discovered a new type of material that could make tyres more durable - namely, waste from food processing.
In the future, it may not be so much a case of treading on eggshells as driving on them.
Researchers at Ohio State University claim that in future thrown away food could provide a replacement for the petroleum-based filler currently used in the process of manufacturing car tyres.
The idea that the likes of tomato skins might withstand punishing road conditions might seem odd, but in tests the rubber made with the new, food-based filler actually exceeded industrial standards for performance.
Using scraps from food processing plants or kitchens as a replacement for the carbon black reinforcing agent may ultimately open up new applications for rubber and make its manufacture far more sustainable.
Katrina Cornish, a biomaterials expert and one of the researchers involved in the project, said the technology could slash American dependence on foreign oil as well as keeping food waste out of landfill.
Cornish has spent years cultivating new domestic rubber sources, including a rubber-producing dandelion.
About 30 per cent of a typical automobile tyre consists of carbon black, which has been used in this way for more than a century.
The component, which is often imported from overseas, makes the rubber durable. It also gives tyres their black colour. It is subject to cost fluctuations owing to changes in petroleum prices.
In contrast, the new rubber produced by Cornish and her team does not appear black but rather reddish brown, depending on the amount of eggshell or tomato in it.
Cornish said: “The tyre industry is growing very quickly and we don't just need more natural rubber, we need more filler, too.
“The number of tyres 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.
“At the same time, we need to have more sustainability.”
She and her team collected eggshells and other food waste from Ohio food producers, rather than domestic kitchens.
“We're not suggesting that we collect the eggshells from your breakfast,” she said. “We're going right to the biggest source.”
According to the US Department of Agriculture, 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, the researchers found.
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 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 is not 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.