Auto shredder residue recycling researched

by Brian R. Hook

Prototype recovers up to 60 percent

Automobile recyclers have long wondered what to do with shredder residue, the leftover material that remains after shredding vehicles and recovering the metals.

If research that is underway at Argonne National Laboratory in Argonne, Illinois is commercialized, two potential options for the nation’s shredder residue would include turning foam into carpet padding and transforming the plastics into battery trays.

“Up to 60 percent of the residue can be recovered as usable materials,” said Bassam Jody, group leader of the energy systems division at the research lab.

With most of the shredder residue currently sent to landfills, the United States generates around 5 million tons of the leftover material annually, Jody estimates. About 30 percent of the material, by weight, is polymers and 10 percent is residual metals.   

Argonne, funded by the United States Department of Energy, has spent around $5 million to develop the process to recycle the residue, Jody estimates. Although the basic concept was developed more than 15 years ago, the last 5 years have been used to develop a pilot plant to demonstrate that the recycling system works, Jody said.

“Based on this work, we are now preparing a full-scale process design and cost estimate as a possible next step in achieving commercialization of the technology.”

The separation system is a continuous dry process that separates the shredder residue – a mixture of polymers, wood, glass, residual metals, rocks, sand and dirt.

After removing any oversized material to protect the equipment, the residue is conveyed to a shredder to further reduce the size. The residue is then conveyed to a trommel to separate the bits and pieces. A magnetic separation chamber recovers the ferrous metals and an eddy current separator recovers the non-ferrous metals.

The resulting material contains more than 90 percent of the recycled polymers originally present in the shredder residue, Jody said. By weight, about 80 percent of this fraction is polymers and contains more than two dozen different types of polymers.

Since most of these polymers are not compatible with each other, the second part of the process uses a wet flotation system that separates the polymers by selectively floating or sinking the polymers.

Recycling the polymers and residual metals in the 5 million tons of shredder residue produced annually would save the equivalent of 24 million barrels of oil a year and would reduce carbon dioxide emissions by 12 million tons, Jody estimates.

Some of the shredder residue still ends up in a landfill, however. After all the recyclables are recovered from the shredder residue during the process, the remaining material – including dirt, glass, sand and other in-organics – is sent to a landfill.

“Shredder residue is one of the leading problematic materials resulting from the recycling process,” said Charles Ossenkop, chair of the technical advisory committee for the Automotive Recyclers Association. The committee monitors recycling issues related to automotive design, material usage and recycling techniques for the trade group.

Ossenkop said the trade group’s committee plans to discuss the economics behind recovering shredder residue with researchers at Argonne within the next year.

The biggest hurdle for recycling shredder residue is the cost, Ossenkop said, noting it is often more expensive to recycle, transport and remanufacture recycled material. “Virgin material is cheap enough that it often doesn’t justify the cost,” he said.

Shredder residue goes beyond automotive recycling. David Wagger, director of environmental management at the Institute of Scrap Recycling Industries, Inc., estimates that 40 percent of shredder residue derives from end-of-life appliances, with the remaining 60 percent of residue coming from old vehicles.

While most of the shredder residue ends up in landfills, Wagger expects to see more uses for shredder residue in the future. He said it would provide additional value to shredder operations by reducing waste-disposal costs and increasing product sales.

The economics behind recycling shredder residue are more favorable in today’s market than in the past, said Paul Johansen, a technology marketing consultant with Johansen Marketing Consulting Ltd., in Victoria, British Columbia, Canada.

Transportation costs have gone up, tipping fees at landfills have increased, and shredder operations do not have enough land to store the shredder residue, Johansen said. But he said the viability of any solution for shredder residue will vary by region.

“There are significant differences in distances to landfills, trucking costs and environmental regulations,” Johansen said, adding that there are often marketing challenges involved with introducing new technologies. “A good new technology can languish for years unless there is a good plan on how to commercialize it.”