Through drying and recycling ASR, recyclers can prevent this useful and valuable material from taking up the dwindling space in landfills and contribute to a cleaner, safer environment.
Savannah Cooper
Every year, about 27 million cars around the world reach the end of their use (U.S. EPA, www.epa.gov). The majority of these vehicles are recovered for recycling, where they are shredded and the useful components, such as metals, are recycled and reused. End-of-life vehicles are the most recycled consumer product, supplying the steel industry with more than 14 million tons of steel.
About 75 percent of an automobile can be recycled. The remaining 25 percent is a combination of metals and shredder waste known as automotive shredder residue (ASR) or auto fluff. ASR consists of a wide variety of materials, including plastics, glass, rubber, wood, foam, tramp metal, wire, fibers, sand and dirt. It can also contain some hazardous contaminants such as lead, cadmium and petroleum hydrocarbons, prompting some countries to classify ASR as hazardous waste. Automobile recycling produces about five million tons of ASR every year, and nearly all of this residue ends up in landfills.
According to the U.S. EPA, approximately 1 million tons of ASR could be recovered for fuel. Using this residue for fuel would reduce carbon dioxide emissions and conserve around one million tons of coal each year, as well as avoid landfilling, resulting in an annual savings of $20 million.
Recycling and Reusing ASR
Because of the decreasing space in landfills and the possibility of hazardous chemicals leaching out, recyclers and scientists have been searching for ways to recycle and reuse ASR. Numerous States allow the use of ASR as an alternative daily landfill cover, which limits odors and prevents trash from blowing away.
Because ASR is full of plastics, which are made of petroleum, it also has the potential for use as a fuel supplement in cement kilns. The California Department of Toxic Substances Control (DTSC) has developed methods for processing ASR to make it into suitable fuel for cement kilns. The process results in a mix of ASR that has a heating value of about 13,240 Btu per pound, which is higher than most types of coal (California DTSC, http://www.dtsc.ca.gov). The DTSC also found that processing and using all of California’s ASR for cement kilns would save cement manufacturers $50 million each year through reduced energy costs and save automobile shredders $20 million a year by avoiding landfill costs.
Similarly, the Environment & Plastics Industry Council and the American Plastics Council coordinated with eight automobile shredders to create a method of processing ASR for use in steel mill blast furnaces. This process would increase the energy content of ASR and produce a material with a thermal value of about 10,000 Btu per pound.
In April 2013, the EPA announced a new interpretation of its regulations which will allow automobile shredder plant operators to recycle plastics that are separated from ASR. This new interpretation allows the automobile industry to use recycled shredder residue products in coatings, paints, adhesives, plastics and flame-retardant additives, resulting in both economic and environmental benefits (Recycling Today, April 2013, http://www.recyclingtoday.com/epa-asr-plastics-recycling.aspx).
Recovering Plastic
Plastics make up 12 to 15 percent of an automobile’s weight and more than half of ASR. The plastics found in ASR include polypropylene, high-impact polypropylene and acrylonitrile butadiene styrene (ABS) and are found in bumpers, dashboards and other vehicle components.
Recovering plastic from shredder residue involves a process of identification and separation. Prior to separating, the ASR is often dried, which makes separation easier. After the plastic is dried and separated out, the various polymers are separated using a flotation system. Through this process, 95 percent of the plastic from a shredded vehicle may be recovered and then used to produce new products such as battery trays and other automobile components (Earth911, http://earth911.com).
According to the Institute of Scrap Recycling Industries (ISRI), 1 to 2 million tons of plastic are generated in shredder residue each year, most of which could be separated and recycled, rather than landfilled. The EPA’s new interpretation allows for automobile recyclers to obtain more usable plastics from scrap vehicles, which will not only save money but will reduce greenhouse gas emissions and conserve energy and landfill space.
Further value can be found in shredder residue through a process known as pyrolysis. In pyrolysis, a material is heated in an oxygen-deficient environment. Through this process, oil can be extracted from the plastics found in ASR. While this process is not yet completely proven for shredder residue, researchers continue to explore its efficiency and profitability, and pyrolysis may soon be a common solution for the recycling of ASR.
After it is dried and sorted, shredder residue is most commonly used as daily landfill cover. This material is placed on top of the waste in an operational landfill to help reduce odors and provide a solid base on which vehicles may move and work.
Equipment and Systems
A full range of equipment can dry, sort and move automotive shredder residue. There are new and used dryers designed specifically to dry ASR, making the material easy to transport, separate and handle. Dryers can be sized and built to best suit specific project needs.
Dryer systems can consist of a correctly sized drum and a burner mounted to a combustion chamber. After passing through the dryer, the dried material is discharged to a transfer conveyor for further sorting and separation. The vapor from the process is pulled through a cyclone that is specifically designed to deal with the fine ASR dust, as well as a high-temperature baghouse which removes all fine particulates from the vapor stream. All ductwork, cyclone and other high-wear areas in the system have abrasive resistant plates to reduce lifetime wear and maintenance costs.
All oversized material ore is removed from the feed stream and placed in front of the feed conveyor. Conveyors transfer the material to and from the dryer system and can be covered to shelter the dried material from the elements.
Automotive shredder residue could be recovered and recycled for use as fuel or landfill cover, but unfortunately most ASR ends up in landfills, where it slowly releases hazardous chemicals. Fortunately, though, more and more recyclers are becoming interested in the possibilities of recycling shredder residue. The EPA recently announced that its regulations will permit automobile shredder plant operators to recycle plastics from ASR, opening up new opportunities to prevent this waste from being dumped in landfills. Drying shredder residue makes it easier—and cheaper—to sort, handle and transport, and there are a variety of drying systems that can be used for this purpose. Through drying and recycling ASR, recyclers can prevent this useful and valuable material from taking up the dwindling space in landfills and contribute to a cleaner, safer environment.
Savannah Cooper is the Writer/Copy/Social Media Specialist at Worldwide Recycling Equipment Sales, LLC (Moberly, MO). For more information on ASR drying systems, call (660) 263-7575 or e-mail [email protected]. View the complete inventory online at www.wwrequip.com.