Scientists Find Multiple New Uses For Worn-Out Tires

"In the United States alone, more than 200 million tires are disposed of annually," said Mark Rood, a U. of I. professor of environmental engineering and one of the co-investigators on the project. "These waste tires can serve as an inexpensive and plentiful feedstock for carbon adsorbents that have commercial value in gas separation, storage and cleanup applications."

Currently, there are an estimated 3 billion waste tires stockpiled in the United States. Mounds of old tires can mar the landscape, collect rainwater that fosters breeding sites for mosquitoes, and ignite into long-lasting fires that pollute the air. While other researchers have investigated the recovery of useful oils and gases from waste tires, little work has been performed on tailoring the properties of tire-derived activated carbons to help solve troublesome air-pollution issues.

In a collaborative research program between the U. of I. and the Survey, Rood, engineer Massoud Rostam-Abadi and graduate student Christopher Lehmann compared the performance of carbon adsorbents derived from shredded tires with the performance of existing commercial products. The researchers also characterized the physical properties -- such as pore size -- of the adsorbents and studied the surface chemistry that can influence adsorption.

Potential commercial applications of tire-derived activated carbons for the removal of toxic pollutants from fossil-fuel-fired power plants, storage of alternative fuels such as natural gas in vehicles, and the removal of volatile organic compounds from industrial gas streams were studied by the researchers. In these tests, the performance of the tire-activated carbon was comparable or superior to some commercial carbons.

"The next step is to produce enough quantities of tire-derived activated carbon for pilot-scale testing to show that this material works under actual industrial test conditions," Rostam-Abadi said. "This is what we are doing now."

Activated carbon is commonly produced from carbonaceous materials such as wood and coal. With its high carbon content and plentiful supply, "tire rubber could potentially serve as an ideal material for making low-cost adsorbents," Rood said. "In addition, almost 70 percent of tire rubber is volatile material that can be recovered as oils and gases and used as an energy source for processing the tires."

The researchers presented their findings in the November issue of the journal Energy and Fuels.