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Updated: Thursday, 11 Oct 2012, 3:16 PM EDT
Published : Thursday, 11 Oct 2012, 3:16 PM EDT
WEST LAFAYETTE, Ind. (WLFI) - Millions of flat-screen monitors and TV sets will soon be obsolete, posing environmental hazards if disposed of improperly. Purdue University researchers are therefore developing tools to help industry efficiently recycle the products.
Liquid crystal displays (LCDs) made before 2009 could have cold cathode fluorescent lamps, or CCFLs, to backlight the display. The CCFL displays contain mercury, which makes them hazardous to get rid of, or even to burn.
"Over the next few years, it is expected that hundreds of millions of CCFL-backlighted LCDs will retire each year," School of Mechanical Engineering assistant professor Fu Zhao said. “Without proper treatment, these used LCDs could lead to serious damage to the environment."
Purdue researchers are trying to help the industry recycle the displays through a new project funded b the U.S. Environmental Protection Agency’s People, Prosperity and the Planet – or P3 – program.
"We will produce equipment and tools specifically designed to disassemble LCDs with acceptable labor cost while recovering high-value components and reducing environmental hazards," Zhao said.
Zhao, also part of Purdue’s Division of Environmental and Ecological Engineering department, is leading the project alongside Carol Handwerker. Handwerker is the Reinhardt Schuhmann Jr. Professor of Materials Engineering.
Electronics contain hazardous chemicals such as heavy metals and brominated flame retardants. The materials can leach out of landfills into groundwater and streams or be converted into "super toxicants" including dioxin while being burnt.
Upwards of 3 million tons of e-waste were generated in 2007 in the U.S., with 13.6 percent collected for recycling and the other 86.4 percent heading to landfills and incinerators. Environmental concerns have led 25 states to pass laws mandating e-waste recycling.
"Because many states have laws prohibiting disposal of electronic wastes in landfills, used LCDs are likely to be incinerated in large-scale capital-intensive facilities or shipped to developing countries," Zhao said. "Neither scenario is good from a sustainability perspective. Incineration is expensive, and materials and energy are wasted. Exporting e-wastes to developing countries damages local environments, harms people's health and is against environmental justice."
LCD hardware usually lasts 10 to 20 years.
But Zhao says because of new advances, those lifetimes are being cut short.
“Due to rapid technology advances, LCD monitors and TVs are becoming obsolete much faster," Zhao said. "The life cycle for products is speeding up, in part because people want the latest products."
Surveys have been done on e-waste collectors. They show LCD monitors and TVs manufactured four to five years ago have started showing up in waste streams.
The high cost of e-waste recycling in the U.S. and Europe has made the waste difficult to manage, but new tools to disassemble LCD panels could make recycling more profitable, according to Zhao.
"Recycling hundreds of millions of LCDs will create new job opportunities," Zhao said.
E-waste recyclers will test the new equipment and tools, and field data will be collected. The tools will be used to more easily remove a monitor's housing and detach circuit boards and metal frames, then separate polarizing filters, glass, liquid crystals, and the mercury-containing backlight unit.
"A unique feature is that these new tools allow quick access, separation, and recovery of high value parts and toxic sub-assemblies," Zhao said.
An LCD monitor includes the front frame, back cover, metal frame, circuit boards, the liquid crystal subassembly with a driver circuit and the backlight unit. Electrode patterns are made of a layer of indium tin oxide, or ITO. The backlight unit includes a frame, fluorescent tubes, a prism, a "diffuser," a reflector, and a protective layer. The liquid crystal subassembly's drive circuit has a gold coating.
"The gold price is currently higher than $50 per gram, and the drive circuit may contain 1-2 grams of gold," Zhao said.
In the past several years, increasing demands from LCD and thin-film solar cell manufacturing have led to the price of indium running from less than $100 per kilogram in 2003 to more than $600 per kilogram in 2011.
"Therefore, recovering the ITO-coated glass makes business sense," Zhao said.
Because fluorescent tubes in the backlight unit contain mercury, the unit must be removed carefully and then sent for proper disposal. To access the backlight unit, the front frame has to be removed first.
"Although screw drivers can be used to remove the front frame, this is not preferred due to potential risks of breaking the backlight unit, which results in mercury release," Zhao said. "To minimize the probability of breaking the tubes, a case-opening tool will first be developed."
A different tool will be developed to remove the back cover from the metal frame.
In 2010, LCD TVs using light emitting diodes as backlights
gained popularity. The LED-backlighted LCDs contain no toxic substances and consume 20 percent to 30 percent less electricity than the CCFL technology.
"Although the LED monitors don't contain mercury, they are still e-waste and will need to be recycled," Zhao said. "At the same time, the LED-backlighted monitors contain valuable materials that will be cost-effective to recover."
Two graduate students and five undergraduate students from mechanical engineering, materials engineering and environmental and ecological engineering are working on the project. The team is expected to showcase their prototype at the National Sustainable Design Expo next April on the National Mall in Washington, D.C.
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