FocusUS lab seeks dregs-to-plastics partner

21 July 2008 20:05 [Source: ICIS news]

Lab recovers plastics from shredder residue By Brian Ford

HOUSTON (ICIS news)--The US Argonne National Laboratory is looking for an industry partner to turn plastics and other residue from old shredded cars into commercially attractive materials, lab officials said on Monday.

Part of the US Department of Energy, Argonne National Laboratory operates a pilot plant for the recovery of plastics, rubber and residual metals from material that would otherwise go into a landfill after the typical recycling process.

The US scraps about 15m cars and trucks each year, according to Argonne.

Most end-of-life vehicles (ELVs) begin their journey at vehicle dismantling facilities that recover usable parts for resale or remanufacture, according to Argonne.

From there, the remaining hulk goes to a shredding facility for separation into ferrous (iron-containing) and non-ferrous metals, both of which are recycled.

About 75% of automotive materials are recycled in the US, but the remaining 25%, known as shredder residue, goes to landfills.

“Shredder residue is an ugly thing,” said James Kolb, senior director - automotive, for the American Chemistry Council (ACC). It typically consists of polyurethane foams, plastics, small amounts of metal as well as rust, dust, glass, wood and dirt.

The technology exists to retrieve much of the plastics and metals from shredder residue, “but whether it is picked up by the vehicle recycling industry is another thing,” Kolb said, explaining that nation’s roughly 200 shredder operations mostly pay attention to metals. “We have to help them realise they are landfilling valuable materials.”

Argonne pilot project manager Bassam Jody said that as vehicles become smaller and lighter to improve fuel economy, they will use more lightweight and non-metallic materials such as plastics.

The move toward fuel efficiency will result in more auto shredder residue, according to Argonne. Unless the companies find ways to profit from non-metallic scrap recovery, the trend towards fuel efficiency could reduce their profits.

“How can these be recovered from the used vehicles and be re-used,” Jody asked, “so they don’t end up in the waste stream at the end of the life of the vehicle?”

Construction of the Argonne pilot project to answer that question began in the early 1990s, Jody said.

It is part of a research and development agreement between Argonne, the American Plastics Council and the US Council for Automotive Research (USCAR), which includes DaimlerChrysler, Ford and General Motors.

Argonne has all but completed its research stemming from the project, Jody said.

“Right now we are looking for an industrial partner” for a full-scale project, Jody said. “The results we have the process looks very promising economically.”

Construction of the pilot plant took place in multiple phases, Jody said. “We kept adding to it as different issues came up.”

The one-tenth scale pilot plant has a design capacity of 2 tons/hour (1.8 tonnes/hour) and consists of two parts, Jody said.

The first part is a dry mechanical separation process. The dry process recovers a good portion of the residual metals, and it separates the polymers from the shredder residue as a concentrate that contains more than 20 different polymers, Jody said.

Some 15-20% of shredder residue is recoverable plastics and rubber, he said.

The second part of the plant is a wet flotation facility that can separate individual polymers or groups of compatible polymers from the concentrate, using a series of flotation tanks.

The chemistry of the solutions in each tank separates the materials. Light materials, including polyolefins, wood and rubber, float in the first tank. The heavier materials sink at this stage, and these include metals, glass, rocks, rubber, and the remaining plastics including filled polyolefins.

The sinking materials are conveyed to the next tank to recover the styrenic plastics. The sinker material from that tank is conveyed to the third tank to recover other targeted polymers, and so on.

The process was successful in separating and recovering plastics from shredder residue and from waste generated from recycling home appliances and electronics, according to Argonne.

Acrylonitrile-butadiene-styrene (ABS) was separated from home appliances at purities in excess of 98% and at yields of more than 80%.

ABS recovered from home appliances and polyolefins recovered from shredder residue were successfully tested for injection-moulding of automotive parts, confirming the feasibility of the process.

However, challenges remain, Jody said, including the presence of polychlorinated biphenyls (PCBs) in the recovered plastic from shredder residue.

The value of the recovered plastics is significantly more if the PCBs, which are carcinogens, can be eliminated, Jody said. Then they can be reused as plastics.

Otherwise, the recovered plastics can be only used as fuel. The material has a heating value greater than coal, Jody said.

“Research is under way at Argonne and at other places to develop an economical process to remove the PCBs,” Jody said.

Even after the removal of PCBs, however, the recovered plastics are 50% less expensive than virgin material, he said.

There are efforts in Europe and Japan to recover material from shredder residue, but those efforts are mostly aimed at using the material as fuel, Jody said. Because disposal costs are higher in Europe and Japan, it is more attractive economically to use the material as fuel, he said.

As disposal costs in the US and the price of oil continues to spiral upward (which in turn affects the price of plastics), the material recovered from shredder residue will become more commercially attractive, Jody said.

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By: Brian Ford
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