CHICAGO—Scrap tire chips work well and cost-effectively as drainage material for landfills, according to a three-year study performed by civil engineering professors at the University of Illinois.
"There are no problems in using tires in place of sand, gravel or other substrates," said Krishna Reddy of the University of Illinois-Chicago. Reddy and Timothy Stark from the Champaign-Urbana campus performed the study for the Illinois Department of Commerce and Economic Opportunity.
Civil engineers have known for years that shredded and chipped scrap tires are a useful material in landfills, highway embankments and other civil engineering applications. However, some municipalities have resisted the use of scrap tires in landfills because of concerns about leachates.
Because of these concerns, the study used scrap tires only as final cover for landfills, not as a bottom liner, according to Reddy.
"In Illinois, we are trying to solve two problems at once," he said. "How do we close abandoned landfills, and how do we find another use for scrap tires besides tire-derived fuel?"
In addition, Reddy and Stark wanted to demonstrate the usefulness of large tire chips—roughly four inches by six inches in size. Before this study, there was little information on the performance of large chips in civil engineering applications.
In their study, Reddy and Stark used large tire chips as final cover in laboratory settings and at an abandoned landfill in Carlinville, Ill. According to the executive summary of the report, two acres of the final cover system at Carlinville was divided into two sections, one with sand as the drainage material and the other with scrap tires.
Results from the study showed that scrap tires performed exactly the same as sand as final cover for a landfill, with no problems in slope stability, settlement or pollutant content of water from the flow meters.
"This study...shows that the use of tire shreds as a final cover drainage material is economical, efficient and safe," the executive summary stated. Engineers should achieve the same results using scrap tires in active landfills as in abandoned ones, the summary said.