Minimizing both molded-in metal parts and paint levels are the most effective product-design strategies for boosting the recycling of computer housings, according to a new study.
The report also recommends continued use of the ISO resin identification symbols, although it found some problems with accuracy.
Eric Masanet, a graduate student at the University of California at Berkeley, presented results of the study May 6 during the International Symposium on Electronics and the Environment in San Francisco.
He coordinated the study for Apple Computer Inc. as an internship last year.
Environmentalists often call on computer makers to use only one type of plastic for all large computer-housing parts, or to make one color standard for each polymer. That sounds good, but it's not realistic given the range of colors and materials used by dozens of computer manufacturers, Masanet said.
Apple has differentiated itself with eye-grabbing colors on its iMac computer, for example.
``You're almost at the mercy of how these computers are collected, and if you don't have a type of plastic that is collected in high-enough volumes, it doesn't tend to get recycled,'' said Masanet, who is working on a doctorate at UC Berkeley's Consortium on Green Design & Manufacturing.
Researchers interviewed 35 recyclers, academic researchers and authorities directly involved with design-for-recycling in the United States and Europe. They visited 24 sites, including recyclers that manually take apart old computers, and companies that use automated machinery. They asked industry officials if potential design guidelines actually could end up increasing computer recycling.
Masanet found that the ISO resin symbols used on electronic equipment are used incorrectly as much as 20 percent of the time.
Rudolph Auer, a manager of environmental issues at Apple, said Apple tightly controls resin identification symbols through its quality-control process.
The most common resins used in computers are high-impact polystyrene, ABS and polycarbonate. Apple uses only ``neat,'' unfilled resins for its computer housings, so researchers did not question recyclers about glass-filled resins.
Recyclers cited problems caused by molded-in metal inserts. Glued-on metal parts pose less of a problem, they said.
Conventional wisdom says snap-fit parts are easier to disassemble. But Masanet said recyclers begged to differ. Snap-fits actually can be harder for recyclers, because employees have to switch back and forth between the power tools used to take apart conventional fasteners, and the methods used for snap-fits, he said. Masanet also said automated recycling technologies will continue to grow.
Attendees at the San Francisco conference saw a video of Hewlett-Packard Co.'s new automated line to take apart HP inkjet printer cartridges. The $1.3 million disassembly line, scheduled to begin production in June, removes the ink, separates materials and ends up granulating the plastic cases. HP officials hope to mix the plastic back into new inkjet cartridges. They said they think the disassembly line will pay for itself in two years.
Held May 6-9, the electronics symposium was sponsored by the Institute of Electrical and Electronics Engineers of Piscataway, N.J.