Guidance on best available techniques and best environmental practices for the recycling and disposal of wastes containing polybrominated diphenyl ethers (pbdes) listed under the Stockholm Convention on Persistent Organic Pollutants
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| Figure 4‑7: Composition of the polymer rich mixture after metal recovery from e-Waste shredding
A large proportion of WEEE plastics is sold as mixed polymer for export, mainly to China or India (UNEP, 2010b). In many parts of the world, however, the polymer fractions and particularly shredder residues are then sent to landfill (see chapters 6 and 8) or incinerated (see chapter7), often in non-BAT/BEP facilities. The four main reasons for the limited recycling of mixed plastics from WEEE are (UNEP, 2010b): Industry using secondary plastic materials has tight specifications in relation to plastic quality, both chemically (compliance to RoHS Directive; European Commission 2011c and respectively the EU-POP Regulation No. 850/2004 as amended by No. 1342/2014), and with respect to material properties have to be taken into consideration. WEEE plastic fractions often contain 15 or more different plastic types and a degree of cross-contamination is inevitable in practice (see Figure 4-2; Dimitrakakis et al., 2009). While three polymers (ABS, PS, PP24) account for between 70% and 85% of the total, the efficient sorting of the mixtures presents difficult technical challenges. WEEE plastics could contain Convention listed POP-PBDEs and also RoHS Directive listed c-DecaBDE25. Potential customers are therefore at risk due to contaminated plastic articles recycled from WEEE. Many major manufacturers require production of larger volumes with identical properties and performance and this is difficult from heterogeneous plastic from WEEE. 
(Dimitrakakis et al., 2009) Figure 4‑8: Polymer types identified in small WEEE polymer samples (%, w/w). Some of the plastics used in WEEE equipment are high-value engineered thermopolymers that can be repeatedly softened by heat and hardened by cooling. If these thermoplastics can be recovered in a usable condition they can be sold for a profit. TV and computer monitors provide two of the richest sources of plastics: the plastic content in these two product groups varies between 10 wt % and 40 wt %. The major plastic part of a monitor is the rear part of the housing; this is separated for recycling and to gain access to the cathode ray tube. These plastic parts are normally removed by hand in the facilities and this gives a clean polymer fraction consisting mainly of ABS and HIPS, which can then be recycled. To maximize resale value, polymers must then be sorted by polymer type (e.g. HIPS, ABS thermoplastic), and by colour. After the plastic has been cleaned and sorted into a specific type, it will need to be compacted for storage and transportation (annex 1), or further processing (see annex 2). This can be done by hand tools such as scissors, shears, etc., or, better, by baling, shredding and size grading. Some mechanized operations combine heating, rapid cooling and cutting into grain. These smaller pieces are then typically heated and extruded through a die to form strings and pellets for final sale as raw materials. This polymer fraction is normally traded at prices that only allow a limited number of treatment steps, especially when the cost of incineration of residual POP-PBDE-containing plastics has to be covered. Therefore the disposal of residual contaminated plastics needs to be covered by the revenue from WEEE recycling (e.g. noble metals) or by legal implementation of the extended producer responsibility (e.g. European WEEE or Chinese WEEE regulations). While initial collection and handling of unbroken plastic parts and cases should not involve exposures of concern to hazardous substances, all subsequent processing involves higher exposure risks. Plastic particles, additives and brominated flame retardants may be released, causing exposures to workers (UNEP, 2010a,b). Size reduction and granulation can also generate heat and, if not properly managed, open smoke and fire. After granulation, the plastic will be moulded under elevated pressure and temperature with risks of exposure to substances contained in the plastic and new substances such as halogenated dioxins and furans (Ota et al., 2009). Directory: Portals Portals -> Draft I film Screening Portals -> Black History Academic Bowl arts & entertainment Portals -> Setting the Table for a Successful Season Download 2.99 Mb. Share with your friends:
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