Grantee Research Project Results
Final Report: Recycling of Liquid Crystal Displays for Maximum Resource Recovery
EPA Grant Number: SU835327Title: Recycling of Liquid Crystal Displays for Maximum Resource Recovery
Investigators: Zhao, Fu , Zelinka, David L , Martin, Alyssa M , Lagro, Adam R , Handwerker, Carol , Mendis, Gamini , Liu, Jili
Institution: Purdue University
EPA Project Officer: Hahn, Intaek
Phase: I
Project Period: August 15, 2012 through August 14, 2013
Project Amount: $14,938
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2012) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Chemical Safety , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
Hundreds of millions of liquid crystal displays (LCDs) will reach their end of life in the next few years, and most of them have cold cathode fluorescent lamps as the backlights. End of life treatment of CCFL backlit LCDs presents some unique challenges. The backlight lamps contain mercury (in general, each lamp could have up to 5 mg mercury), shredding the entire unit will be cost prohibitive since special facilities are needed to avoid mercury release as mercury is very volatile. This leaves manual dismantling the only option. Unfortunately, the mercury containing lamps are located deep in the display panel, and enclosed in the metal frame. To open the metal frame and remove the lamps safely extreme care has to be taken as the lamps are very fragile. This slows down the dismantling process significantly. Discussions with electronic waste recyclers indicate that recycling LCDs for resource recovery using available equipment and tools is not profitable in U.S. due to high labor cost.
As many states in U.S. have laws prohibiting landfill of electronics waste, used LCDs are likely incinerated in large-scale capital intensive facilities or shipped to developing countries where polluting informal dismantling and recycling processes are carried out. Neither scenario is desirable from a sustainability perspective. Incineration is expensive thus brings additional financial burden to the society, while at the same time the substantial energy and materials consumed during raw material extracting and product manufacturing are lost. On the other hand, exporting e-wastes to developing countries damages local environment, damages people’s health, and is against environmental justice.
During the past several years, there have been efforts in developing recycling technologies for retired LCDs, all of which have been carried out in the E.U. Although relevant, these technologies may not be suitable for the U.S. where the recyclers may not be able to charge (or at significantly lower level) a tipping fee. Therefore, the overarching goal of this project is to enable profitable and environmentally sound recycling of liquid crystal displays (LCDs) in the
U.S. For Phase I, the technical objective is to develop “proof of concepts” equipments and tools that can be used to quickly disassemble LCDs to recover and remove valuable and toxic components.
Summary/Accomplishments (Outputs/Outcomes):
The breakeven disassembling time is largely determined by the recovery value and labor rate (including overhead). Under current market conditions and commodity prices our industrial collaborator suggests the following numbers for an average LCD monitor with a screen size of 14-18 inches, which represent more than 90% of LCD monitors collected. Survey results indicate that for an average LCD monitor the breakeven disassembling time for a small to medium size e- waste recycler is in the range of 3 to 5 minutes.
Average weight (lb) |
Market value ($/lb) |
Recovery value ($) |
|
Steel |
2.88 |
0.79 |
2.26 |
Mixed plastics |
3.70 |
0.19 |
0.68 |
Wire and cable |
0.06 |
0.93 |
0.05 |
Screen driver circuit |
0.19 |
6.56 |
1.25 |
Other circuit boards |
0.74 |
4.28 |
3.19 |
Backlight lamps |
2-4 pieces |
-$0.40/piece |
-1.20 |
Recovery value total |
$6.23 |
After exploring many ideas and options, the team develops a four-step procedure for LCD disassembling. Appropriate tools for these steps have been designed and fabricated. The procedure starts with removing the outer plastic casing. For typical LCD monitors, two fastener types are used to constrain the plastic outer casing. Screws are used to attach the back of the casing to a metal inner housing, and injection molded snaps hold the front of the casing to the back. The tool (shown in Figure 4) is similar to a hollow drill bit and consists of a cutting bit and a live center. The geometry of the live center allows the cutting bit to be centered over both external screws as well as those inside a screw boss. When used, the cutter removes a circle of material directly surrounding the screw head. This will detach the back cover of the monitor from the screw post holding it in place. After the screws are removed, the plastic casing is still held together by injection molded snaps. An oscillating cutter is mounted on a workbench so the blade sits above a work surface.
Second, the circuit boards are detached. A metal structure covers circuit boards within the monitor to provide structural support as well as electrical shielding. This structure is generally held in place with a small number of machine screws, which can be removed using standard
Philips bits with a power screwdriver. The circuit boards are usually fastened to the internal metal housing with a large number of machine screws. To improve the speed of the removal, a tool was designed to break the board material (fiberglass) surrounding the screw. The tool is put over the head of a screw and struck with a hammer. The screw boss supporting the circuit board and the edge of the tool function as a set of dies, causing the board material to shear off around the screw head. In addition to this, the circuit board removal tool has an integrated pry bar.
Third, the backlight unit and screen assembly are separated. After removal of the circuit boards, a metal housing enclosing the backlight unit and screen assembly is exposed. This assembly is commonly held together with stamped sheet metal snaps, tape, and a limited number of screws. Because the snaps do not require significant force to disengage, a pry tool is suitable for separation of these components. After opening the metal housing, the backlight bulbs can be removed and stored in a container. The filter set, light guide, and diffuser are collected and sorted for sale. The driver circuit usually has higher gold content than other circuit boards recovered and should be separated and sold as high-quality boards.
Last, liquid crystal inside the screen panel is removed using ethanol as solvent. The liquid crystals are filled between two layers of glass with a thickness of around 1mm. Glass of this thickness is quite fragile. The panel is held together by a lip of epoxy that runs the perimeter of the panel. The epoxy is very recalcitrant against solvent. However, it was found that the edge can be easily cut off using an office paper trimmer, while leaving the remaining of the glass panels untouched. After that, minimal force is required to fully separate the panel and expose liquid crystal.
Conclusions:
Using the tools developed the team was able to limit the total disassembling time to less than 5 minutes, the breakeven time suggested by e-waste recyclers. All the tools can be readily built using low-cost tools available on the market. The disassembling time can be shortened further after optimization. Therefore, the Phase I project was successful overall since the key objective was achieved. Enabling cost-effective recycling of LCDs in the U.S. will contribute to all three pillars of sustainability, e.g. people, prosperity, and the planet. Diverting used LCDs from the landfill and incinerator increases resource efficiency and minimizes toxic releases, while creating job opportunities in the U.S. In addition, profitable recycling of LCDs in the U.S. eliminates the export to developing countries. This improves environmental quality in these countries, thus enhances environmental justice. This also reduces health risks to workers and communities that used to be exposed to toxic chemicals from e-waste handling, thereby contributing to improving the quality of life.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
Waste to value, electronic waste recycling, resource recovery, industrial ecology, life cycle analysis, cost benefit analysis, global considerations.Relevant Websites:
Facebook: Purdue LCD Recycling Exit
https://engineering.purdue.edu/LCDrecycling/ Exit
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.