One example is PGM loss from car catalysts: in contrast to earlier conditions, today's au-tocatalysts under European or American driving conditions emit hardly any PGMs during the use phase. However, under typical "African" driving conditions (e.g., bad roads, low car maintenance, misfires, bad petrol quality), a catalyst is likely to be mechanically destroyed, and PGMs with broken catalyst ceramic are blown out from the exhaust and dissipated along the roadside.
resource potential in our "wastes." This has been recognized by governmental bodies such as the European Commission, which strives to make Europe a "recycling society" and seeks to prevent the creation of waste and to use waste as resources. Supportive legislative measures underline this approach: the Directive on End-of-life Vehicles from September, 2000, and the Directive on Waste Electrical and Electronic Equipment (WEEE) from January, 2003.
Does this mean that everything is now on the right track? Could the closed loop for most metals be expected to become reality soon? How well does this all fit to the recycling of technology metals?
The success by which metals will finally be recovered from EoL products depends on a set of main impact parameters as well as on the setup of recycling chains as a whole. No single universal recycling process exists. Depending on the products and materials involved, various logistical and technological combinations are required, and many different stakeholders are involved. The main steps in the recycling chain are collection, dismantling/preprocessing, and final metals recovering. Success factors are interface optimization between the single recycling steps, specialization on specific materials, and utilization of economies of scale. The key impact parameters comprise technology and economics, societal or legislative factors, as well the life cycle structure of a product (Hageluken 2007).
Technical Impact Factors on Minor Metal Recycling Rates
Technical capability and installed capacity to recover metals effectively from products need to be evaluated under a systems perspective that considers the entire recycling chain. Technical conflicts of interest cannot be fully avoided, and from complex streams, some metals will not be recovered. Setting the right priorities is important. Considerations include:
• Complexity (i.e., the variety of substances in a product): Cars and electronic devices are examples of highly complex products, each consisting of a large number of complex components. Many substances are used in numerous combinations, often closely interlinked, and comprise both valuable and hazardous substances. Precious and special metals are frequently key elements in such products or in one of their key components.
• Concentration and distribution of metals: The recovery of technology metals that occur on a ppm level (e.g., in circuit boards, catalysts, or LCD screens) is technically more challenging than the recovery of Cu from a cable, Al from a wheel rim, or Pb from a car battery, since the latter are highly concentrated in these components.
• Coupled recovery: Similar to coupled production in primary production, a limited number of valuable "paying" metals provide the economic incentive for recycling, enabling the additional recovery of
"by-product" metals with subeconomic value or concentration. For printed circuit boards (PCBs), the drivers for recycling are Au, Ag, Pd, and Cu; however, various special metals can be co-recovered with appropriate technologies. • Product design and accessibility of components: A good "design for recycling" eliminates the use of (hazardous) substances that hamper recycling processes (e.g., mercury in backlights of LCD monitors) and ensures the accessibility of critical components. An example of an easily accessible component is the car catalyst, which can be cut from the exhaust system prior to shredding and fed into the appropriate recycling chain. The opposite is the case for most car electronics, which are widely distributed over the vehicle and thus are seldom removed prior to shredding. Consequently, most technology metals contained in car electronics are lost during the shredding process.
Metal Recovery: Smelting and Refining
Complex products require a well-organized, dedicated process chain, involving different stakeholders. Especially for the efficient recovery of technology metals in low concentrations from complex components, high-tech metallurgical processes are required. Umicore, for example, recovers in such an "integrated smelter refinery" 14 different precious and special metals together with the major metals Cu, Pb, and Ni, which are used as metallurgical collectors. For precious metals from PCBs or catalysts, despite their low concentration, yields of over 95% are realized, and Sn, Pb, Cu, Bi, Sb, In, Se and others are simultaneously reclaimed (Hageluken 2006a). In other dedicated processes, Umicore recovers Co, Ni, and Cu from batteries (NiMH, Li ion, Li polymer type), Ge from waver production scrap, and In from ITO-sputtering targets. Research is ongoing to extend the range of feed materials further (e.g., into PV applications) and recovered special metals (e.g., Ga, Mo, Re, Li). For metals that already follow other metal streams or can be separated from the offgas or effluents, recovery might be achieved through affordable adjustments of the flow sheet and/or the development of dedicated after-treatment steps. However, for metals that oxidize easily and are dispersed as a low grade slag constituent, economic recovery can be extremely difficult or even thermody-namically impossible.13
The combination of metals as well as toxic and organic substances with halogens in many EoL products requires special installations and considerable investments for off-gas and effluent management to secure environmentally
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