Ohio State University Researchers Find Food Waste Could Partly Replace Petroleum-Based Filler Used in Tire Manufacturing for Over a Century

Tests showed that rubber produced with the new fillers performed above industry standards and enabled new applications for tires.

Katrina Cornish explained that this technology has the potential to solve three problems: making rubber product manufacturing more sustainable, reducing dependence on petroleum, and diverting waste from landfills and disposal sites. A research scientist at Ohio State University working in the field of biomaterials, Cornish has spent years cultivating new domestic rubber sources, including a dandelion that produces rubber. Now she is awaiting a patent for a method that will turn egg and tomato shells into suitable alternatives for carbon black. This technology creates an alternative where carbon black—a petroleum-based filler that American companies typically purchase from abroad—can be produced from local sources. Approximately 30% of a typical automobile tire is carbon black; this is why tires appear black. Carbon black makes rubber durable and its cost fluctuates with oil prices. Cornish noted that sourcing carbon black has become increasingly difficult. "The tire industry is growing very rapidly and we need not only natural rubber but also more filler," she said. "The number of tires produced globally increases each year, so countries are using all the carbon black they can produce. There is no longer an abundance, so we cannot source it from Russia as we once did to bridge the gap. At the same time, we need greater sustainability," she stated. For this reason, the project team collects egg shells and other food waste from Ohio-based food producers. Cornish said, "We are not collecting egg shells from breakfast tables; we are going to the largest source." According to the USDA, Americans consume approximately 100 billion eggs annually. Half of egg shells are generated during production at commercial food factories, and money is spent transporting and storing them in solid waste landfills. In these facilities, shells filled with minerals cannot be converted as they should be. Researchers explain that tomatoes, the second most popular vegetable in the United States, also represent a source of filler material. Americans consume 13 million tons of tomatoes annually, most in canned or processed form. Commercial tomatoes are grown with thick, fibrous shells to withstand long-distance shipping. When food companies want to make a product like tomato sauce, they peel off and discard these hard-to-digest shells. Cindy Barrera, a postdoctoral researcher in Cornish's laboratory, observed in tests they conducted that egg shells have porous microstructures that provide a larger surface area for contact with rubber and offer unusual properties for rubber-based materials. Barrera said, "Fillers typically make rubbers stronger, but they also make them less flexible." "We saw that replacing different portions of carbon black with egg shells and tomato shells resulted in synergistic effects, thus allowing strong rubber to maintain its flexibility," she stated.