Waste stream definition
The screens represented 23% of WEEE collected in 2010 (source ADEME).
At present, the stream is mainly composed of CRTs screen and liquid crystal displays with (mercury containing) gas discharge lamps (LCD). However, LCDs and LED screen are starting to arrive at the treatment facilities. In terms of technology, there are also plasma screens, OLED or laser. These technologies are usually reserved for large screens (plasma and laser) or few available on the market (OLED).
It should be noted that the “screen†stream is special because due to the recent and quick evolution of these products, the products currently arriving in treatment facilities are not representative of actual sales of screens (M.A. Reuter – 2004). Indeed, collected screen are mainly CRT screens, while sold screen are “flat screens†type (LCD, Plasma, LED, …).
This is why treatment facilities are now set up to treat CRT, not yet flat screens. New treatment processes are being developed to predict the future and large scale collection of these new types of screens.
Composition of screens stream
Others : Wood, External power cable, Electrons gun, Condensators, Comon waste, Flat screens, Plastics without BFR, Photoluminescent powder, Transformers or others induced motor, Vacuum tube (with electrons gun)
Figure 1: Composition screens stream: mainly composed of CRT screens (Study ADEME 2011)
Waste stream depollution and recycling
Depollution / pretreatment
Currently there are few treatment facilities that can handle liquid crystal displays. However a english study (WRAP – 2009) has demonstrated the technical feasibility of a method for treating flat screens (LCD and plasma). On liquid crystal displays, the component that requires special treatment is the discharge lamp lighting that allows the lighting of the screen. This lamp currently contains a small amount of mercury but still requires appropriate treatment.
Due to the construction of LCDs, it is not possible to consider a manual disassembly of these lamps. Tests disassembly of LCDs have led to the deterioration of lamps in 15 to 35% of cases, making mercury recovery impossible and exposing workers to mercury from these lamps.
Depollution of LCDs is therefore carried out during the treatment process.
Below is an example of process screens (CRT) treatment at SITA:
Treatment / Recycling
The treatment process for LCD screen is as follows:
– Grinding of screens in a closed system to avoid losses of mercury
– Washing of fluff: to recover the mercury content in lamps
– Sort of fluff
- magnetic
- Eddy current
- X-ray
- Near infrared
This processing method allows to seperate the components following screens:
– Mercury
– Ferrous Metals
– Non-ferrous metals
– Printed circuit board
– Cables
– Glass
– PS
– ABS
– PC
Proposed improvement plan
The table below provides some ideas to improve the recycling of WEEE. These ideas are from studies on the recycling of some products and difficulties encountered by treatment operators responsible for the treatment of WEEE. These areas for improvement can initiate a deeper reflection from producers. However, each product has its specificities and a number of other constraints to fulfill.
| Encountered difficulties | Impact for recycling | Eco design opportunities |
|---|---|---|
| Presence of backlight lamp containing mercury. | Obligation to withdraw lamps containing mercury (WEEE directive). Operator exposure to mercury. | Facilitate access to components containing mercury, if possible making their removal automated. Substitution of mercury vapor lamps by technologies that do not use mercury (LED, OLED, etc...). |
| During dismantling backlight lamps are broken. | Mercury recovery is impossible. Operator exposure to mercury. | Reduce weakness of backlight lamps. Facilitate access to backlight lamps (number of fastening elements, type of fixation). |
| The fluff can be contaminated with mercury from broken lamps. | Containment of shredding facilities to prevent the dispersion of mercury. Washing of fluff to recover traces of mercury. | Facilitate access to backlight lamps containing mercury to remove mercury before shredding. |
| Materials of screens are assembled with a large number of fasteners. | Need a thorough shredding to achieve acceptable levels of separation of different materials. | Limit the number of fasteners or provide fasteners consistent with the shredding of the product. Facilitate the separation of incompatible materials for recycling (metal / plastic). |
| Presence of indium in the electrodes of LCD panels. | Although the amount is very low, the recovery has strong environmental interest (ressource depletion) and economic. | Substitute the use of indium. Allow the extraction of components containing indium for recycling of this metal. |
| Some subparts of a screen can break down (backlight, electronic) before the LCD panel (up to 45,000 h), leading the premature disposal of the product. | The lack of availability of spare parts or their price makes the product repair unsuitable. | Easy access and replacement of the subsets having the lowest lifespan. Provide spare parts for the repair and the reuse of products. |
References
– Sampling and characterization: Analysis of campaigns 2009-2010 – ADEME 2011 – french
– ADEME. Annual report « Electrical and electronical equipments ». Data 2011
http://www2.ademe.fr/servlet/getBin?name=C1D8D3FB0D6D41BC332B8322BD6CDB1F_tomcatlocal1320332164546.pdf – french
– Demonstration of flat panel display recycling technologies – WRAP 2009:
http://www.wrap.org.uk/sites/files/wrap/Flat%20Panel%20Display%20recycling%20technology%20report.pdf
– Comparative life cycle analysis of CRT and LCD computer displays.
http://www.epa.gov/oppt/dfe/pubs/comp-dic/lca/
– M.A. Reuter (2004): The time-varying factors influencing the recycling rate of products. Resources, Conservation and Recycling, Vol. 40(4), pp. 301-328