Improving metal returns and eco-efficiency in electronics recycling

Transcription

1 Improving metal returns and eco-efficiency in electronics recycling - a holistic approach for interface optimisation between pre-processing and integrated metals smelting and refining Christian Hagelüken Umicore Precious Metals Refining. Umicore AG & Co. KG Hanau, Germany christian.hagelueken@eu.umicore.com Abstract The efficient recovery of precious and special metals from electronic scrap has significant benefits - economically, environmentally, but also under a resource conservation aspect. The yields of these metals could be substantially improved by higher collection rates, less scrap exports to regions with insufficient recycling structures, and by interface optimisation, as pointed out in this document. Keywords - electronic scrap recycling; precious metals; integrated metals smelting and refining; interface optimization I. INTRODUCTION In today's discussion on the optimization of electronicsrecycling, raising attention is put on maximizing ecoefficiency, i.e. the environmental and economical balance, by maximizing physical recycling and revenues obtainable thereof, while minimizing environmental burden and total costs connected with the recycling chain. Here, also the 'environmental fingerprint' of materials has to be considered, i.e. how much negative environmental impact can be saved by recycling of e.g. a metal instead of producing this 'new' from mining operations [1]. Due to the considerable environmental impacts of turning precious metals from low grade primary ores into pure metals, a high overall recycling yield of the precious metals has not only economical but also large ecological benefits. Just since recently, another aspect has regained interest, which - after "The limits to growth" discussion triggered by the Club of Rome in for almost two decades has been widely neglected: the scarcity aspect of natural resources. The price development for crude oil and the continuing economic growth especially in the Asian region with its huge demand also for metals, resulting in a remarkable price rally affecting the industry globally, brought back to attention that natural resources are not unlimited. Reference [2] concludes "providing today's developed-country level of services for copper worldwide (as well as for zinc and perhaps platinum) would appear to require conversion of essentially all of the ore in the lithosphere to stock-in-use plus near-complete recycling from that point forward". Besides base and precious metals also special metals like selenium (Se), tellurium (Te), bismuth (Bi), antimony (Sb) and indium (In) have shown significant increase in demand and price. Many of these special metals are typical byproducts, only available to the market in quantities corresponding to the production of the main metal (In from Zn; Se, Te mainly from Cu; Bi from Pb) [3]. They are also important for electronic applications: Indium is needed in the production of LCD screens, bismuth is an important lead substitute, e.g. in lead-free solders, antimony is used among others for flame retardants in electronic applications. In this context, end-of-life products like electronic scrap are not to be regarded only as a burden but also as a significant resource potential, a 'mine above ground' that should not be wasted. This is especially important for regions like Europe, where after over thousand years of mining the natural resources for many metals have been largely exploited. Nevertheless, today a large portion of European (and North American) electronic scrap is exported - not seldom illegally - to Asia, with China being one but not the only destination. Like in mining of primary resources also for recycling operations the metals recovery efficiency, i.e. the bottom line metal yields, is a crucial factor, but here still much needs to be optimized in 'waste'-processing. A big improvement potential exists in China, India, Vietnam and other countries in Asia and Africa, where e-scrap is mostly treated in 'backyard operations', using open sky incineration, cyanide leaching and simple smelters to recover mainly copper, gold and silver - with comparatively low yields - and discarding the rest [4][5]. Besides the tremendous adverse effects on environment and health in these regions, this also means a huge and mostly irreversible waste of resources. It is of particular irony if material that had been collected e.g. in Europe under the WEEEdirective aiming to foster the environmentally sound reuse/recycling and to preserve resources finally ends up in such a 'recycling'-environment. But also the recycling chains for e-scrap in Europe and other industrialized regions can be further optimized as will be shown later. The following chapters will elaborate what challenges, deficits and optimization potentials exist in e-scrap recycling in a European context. The text will not go into technical details but put emphasis on a holistic approach and the technical interdependencies, especially within the interface between mechanical pre-processing and metals smelting and

2 refining. The eco-efficiency aspect is here an important evaluation tool. Material recovery per se is not a solution in itself without considering the implied economic and environmental effects. This is the main problem of the solely weight based calculation of recycling quotes as defined in the EU WEEE-directive, which makes the recovery of 1 kg of iron - or even concrete from a counterweight in a washing machine - as important as recovering 1 kg of gold. Any sustainable recycling solution must be transferable and applicable in practice - and it must be payable. Demanding e.g. in an European labor cost context that used cell phones would need to be dismantled manually down to their different components, simply means that even more phones from Europe would find their way somehow to Asian or African destinations, where recycling - if any - would take place in an inefficient way. II. MATERIAL COMPOSITION OF ELECTRONIC SCRAP Electronic materials contain a wide range of elements, some of which are valuable, some of which are toxic or otherwise hazardous and some are both. These all are highly interlinked in a complex composition. Precious metals: Gold (Au), silver (Ag), palladium (Pd), and to a lesser extend platinum (Pt). Base metals: Copper (Cu), aluminium (Al), nickel (Ni), tin (Sn), zinc (Zn), iron (Fe), etc. Metals of concern: Mercury (Hg), beryllium (Be), indium (In), lead (Pb), cadmium (Cd), arsenic (As), antimony (Sb), etc. Halogens: Bromine, fluorine, chlorine Combustibles: Plastics, organic fluids, etc. If such scrap is landfilled or not treated in an environmentally sound way a high risk of environmental damage exists. It also contains valuable resources, which should be utilized. Most of the hazardous but also most of the valuable metals are concentrated in the circuit board; hence the eco-efficient treatment of the boards is of key significance. Looking at the different e- scrap categories, grey goods (IT equipment) and brown goods (audio and video equipment) are most important in terms of the use of precious and non-ferrous metals. Table 1 gives examples of the material composition of various equipment, as well as for circuit boards from PCcomputers and TV's. These figures are only indicative numbers obtained from specific samples, they can vary significantly also within one type of equipment, but the order of magnitude is correct. As compiled in Table 2, it can be seen that also for the grey and brown goods, plastics and steel dominate the weight of the equipment. A totally different picture is obtained when looking at the value distribution as shown in the same table. For PC-boards, cell phones and also the calculator the precious metals make up more than 80% of the value, for TV-boards and the DVD-player they still contribute to more than 40%. Behind the precious metals comes copper, while Al and Fe value-wise are less important. Taking into account the high 'environmental fingerprint' of the precious metals, an ecological ranking of the elements would be much closer to the value than to the weight distribution. TABLE I. MATERIAL COMPOSITION OF ELECTRONIC EQUIPMENT cell phone cordless portable DVD DVDR calculatoboards TV- phone audio PCboards weight g/unit Cu [%] Al [%] Fe [%] plastics [%] glass [%] others [%] Ni [%] 0,1 0,1 0,03 0,05 0,1 0,5 0,3 1 Pb [%] 0,3 0,8 0,14 0,3 0,4 0,1 1,0 1,5 Sn [%] 0,5 0,9 0,1 0,2 0,2 0,2 1,4 2,9 Ag [ppm] Au [ppm] Pd [ppm] source: 1-5: J. Huisman/Philips; 6-8: Umicore; 6 without battery TABLE II. WEIGHT VERSUS VALUE DISTRIBUTION weight-% Fe Al Cu plastics Ag [ppm] Au [ppm] Pd [ppm] TV-board 28% 10% 10% 28% PC-board 7% 5% 20% 23% mobile phone 5% 1% 13% 56% portable audio 23% 1% 21% 47% DVD-player 62% 2% 5% 24% calculator 4% 5% 3% 61% value-share Fe Al Cu sum PM Ag Au Pd TV-board 4% 11% 42% 43% 8% 27% 8% PC-board 0% 1% 14% 85% 5% 65% 15% mobile phone 0% 0% 7% 93% 5% 67% 21% portable audio 3% 1% 77% 20% 4% 13% 3% DVD-player 13% 4% 36% 48% 5% 37% 5% calculator 0% 5% 11% 84% 7% 73% 4% This leads to the following observations and conclusions: Toxics or other harmful substances are usually concentrated in the circuit boards; the same applies for the material content values. Any major loss of precious metals decreases drastically the net recoverable value from electronic goods. Material composition can have a significant impact on recycling requirements and adequate technical processes, including emission control. Mixing different qualities in collection/pre-processing can negatively influence recycling returns (dilution, technical constraints). Legislation impacts the material composition (and hence the recycling requirements), e.g. the ban on lead from the EU ROHS-directive implies increased use of tin, copper, bismuth and silver in solders. Also miniaturization and technical progress impact the material composition. There is a tendency of decreasing absolute precious metals content in new models (miniaturization), but the relative content in ppm is more stable. New products can bring new compositions (e.g. MP3 player, digital camera), also new product generations can drastically change recycling requirements (e.g. CRT-glass LCD glass).

3 III. RECYCLING CHAIN AND TOTAL CHAIN EFFICIENCY Recycling is more complex than it appears on the first look. The chain consists of different, subsequent steps, which are collection, dismantling, shredding/pre-processing, and end-processing (smelting/refining) of the various materials and metals. These steps are interlinked and interdependencies are crucial. But currently, the single steps are mostly conducted in an isolated way, thus missing the chance for a more holistic optimization, which has to work on the interfaces. It is obvious that the bottom-line efficiency (metal yield) of the entire recycling chain is the product of the efficiency of every single step. Thus, the least efficient step has the biggest impact on the efficiency/yield of the entire chain. If something goes wrong in the upstream processes even the most sophisticated end-processing technologies cannot make up for the losses that occurred before. In this context, making end-of-life material available and fit for recycling still has the highest priority. Today, probably more than 50% of IT-equipment still escapes recycling for various reasons: End-of-life material sits 'on the attic' or 'in the drawer' of consumers (here at least a theoretical future potential for recycling exists). Material is discarded with municipal waste. Material is exported for 'reuse' to developing and less industrialized countries (Asia, Africa, Eastern Europe). Even if the reuse label is not simply misused to circumvent transborder waste shipment regulations, it has to be realized that reuse is a temporary solution only, finally leading to end-of-life. However, due to a lacking infrastructure and awareness in many importing countries, an efficient recycling probably will not take place [5]. Even if material is collected and enters the recycling chain, numerous opportunities for failure of metals recovery exist. Material is exported for 'recycling' to non-oecd countries. As pointed out before, often 'cheap' backyard operations are used, which usually obtain much lower metal yields and cause considerable environmental damage [4]. Material is dismantled and preprocessed not in an optimal way, which implies significant (precious) metal losses in sidestreams and final waste (see IV). State-of-the-art integrated smelters and refiners can achieve metal yields for components or fractions containing precious metals and copper of well over 95%, while also a range of other non-ferrous metals are recovered at high yields. Nevertheless, due to the inefficiencies in collection and recycling, the bottom line recycling yields along the entire chain are far below 50% (see also [6]). A drastic example is the cellular phone. With annual sales increasing from 400 million units in 2001 to 825 million in 2005 [7][8] and taking into consideration their relatively short use-phase, the theoretical potential for recycling lies in the magnitude of 500 million units or 50,000 t/yr (at 100 g per unit). The real quantity of phones which physically came back to industrial recycling operations on a global scale is estimated to be surely less than 1000 t/yr and probably even less than 500 t/yr, i.e. only 1% of the theoretical recycling potential. IV. METALS SEPARATION AND RECOVERY For metals separation and recovery from electronic scrap both mechanical and metallurgical processes are utilized. Each has strengths and weaknesses, which have to be understood to develop the most efficient way. In an optimized system both approaches should be used in the right combination. A. Mechanical processes Before any metals recovery can take place, the various metals and materials contained in an electronic device or a fraction thereof have to be liberated first. The liberation usually is done by some kind of shredding or crushing process, which often is supported by manual dismantling of certain components (circuit boards, casings, external cables, batteries, etc.) prior to mechanical size reduction. After breaking the material up in smaller sizes, these are then sorted into defined output fractions, making use of their specific physical and/or optical characteristics. Typical sorting processes used are magnetic separation of ferrous parts, eddy current separation (electric conductivity) of aluminium, and gravity separation (water or airflow tables, heavy media floating, sifting). Alternatively or in addition also manual sorting or new optical sorting techniques are used. Intermediate screening processes and further size reduction steps might be used to support the mechanical sorting. Final output streams are usually components taken out as a whole, a magnetic fraction (going for further treatment to a steel plant), an aluminium fraction (to Al-smelters), a copper fraction (to Cu-smelter), sometimes clean plastic fraction(s), and waste. The latter comprises mixed plastic fractions, glass, wood, rubber, etc, often in the form of a 'shredder light fraction', which is given out for further processing, incineration or landfill. Mechanical processes have the advantage of being relatively cheap in investments and operating costs compared to metallurgical processes. However, they have their technical limits that have to be considered: Only a material, which is really broken up into its main fractions (liberated), can be sorted efficiently. Separation processes are never 100% sharp, there always is a certain overlap between different physical properties. In gravity separation, e.g. besides density also particle size affects the sorting result. Reworking/scavenging of separated fractions can improve the selectivity, but also drives up investment and operating costs. Dust and other very fine fractions can cause considerable problems in dry processes. Adhesion to surfaces can overrule other physical propertiers, in case of large dust portions, even filter systems might not be able to catch it completely. Moreover, dust layers on machinery and in building can lead to fires and explosions. Like in mineral processing of ores, also for electronic scrap the concentration-yield function applies (Fig. 1). The basic rule is that the recovery yield for a specific metal from an input stream is decreasing with a rising

4 concentration rate (purity) of that metal separated into an output fraction ('concentration dilemma'). This is logic, since in order to obtain a 'clean' output fraction all nontarget materials have to be surely removed, which in a certain magnitude leads also to an unintended coseparation of the target metal in sidestreams. Hence, the further processing of a clean output fraction becomes more easy and economical, but the 'cost' for this is a higher loss of the target metal. When separating several major materials (like Fe, Al, plastics) in subsequent processing steps from a complex feed material, the unintended co-separation of 'minor' metals can add up substantially. In the concrete case of electronic scrap this means that the mechanical separation of iron, aluminium and plastics always bears the risk of inevitably losing precious metals in these streams. These cumulated losses reduce the overall precious metal yield of pre-processing, which generally aims to concentrate the PMs in a copper fraction. Accepting higher impurities of Fe, Al and plastics in the copper fraction can boost the overall PM recovery and thus the generated value. As liberation of the different materials prior to mechanical sorting is so important, the complexity of a feed material has a considerable impact on the achievable yields. The more different materials are interlinked and the more intensely the particles are interwoven with other materials the worse are the results of mechanical separation. Circuit boards, but also cell phones, are highly complex materials in this respect, which should be removed prior to mechanical pre-processing. Concentration rate* % The e.g. concentration separating Cu + PM from feed into own fraction dilemma Recovery rate** % * in output fraction ** of target metal PM-loss % A less complete separation of Fe, Al, plastics can significantly reduce PMlosses by unintended co-separation PM Fe 100% Al 100% plastics 100% Recovery rate per individually separated material % Figure 1. The concentration-yield function in mechanical processing B. Metallurgical processes A state-of-the-art smelter and refinery process has a major impact on the recycling efficiency, in terms of elements and value that are recovered as well as in terms of overall environmental performance. Besides copper and precious metals, modern smelters can recover a large variety of other elements, they safely isolate hazardous elements, and can make use of organics like plastics. Umicore has recently completed major investments at its Hoboken Works, designed for an optimized treatment of recyclable materials and industrial by-products. The processes are based on complex lead/copper/nickel metallurgy, using these base metals as collectors for precious metals and special metals. All processes are equipped with state-of the art off-gas and waste water purification installations. A detailed description of the operations is given in [9]. In principle, also metallurgical processes work with the steps liberation, separation/upgrading and purification. Other than in mechanical processes, liberation is not achieved by crushing/shredding but by smelting. From the melt then the different materials/metals are 'sorted' by making use of their chemical/metallurgical properties. Some metals amalgamate with the collector metal, e.g. precious metals in copper, others are oxidized and transferred into a slag phase or leave the furnace via the offgas stream as dust or in a volatilized form. Most output streams including slag and offgas are usually reworked, which leads to a complex flowsheet (Fig. 2), but helps to improve yields significantly. The final output are purified metals, a depleted slag (used as construction material), cleaned offgas and sewage water, sulfuric acid (a product derived from offgas purification) and a small amount of waste (containing certain non-recoverable metals extracted from the offgas stream), which goes to controlled deposits. As for mechanical processes, certain limits exist for metallurgical processes, which have to be considered. Organic constituents are utilized to substitute coke as a reducing agent and fuel as an energy source, but a material recovery of plastic to plastic is not possible. Integrated smelters cannot recover aluminium and iron as metals, they are transferred into the slag. The presence of halogenated flame retardants in the smelter feed (as in circuit boards) can lead to the formation of dioxins unless special installations and measures are present. State-of-the-art integrated metal smelters designed for the treatment of electronic scrap have such installations and can safely prevent dioxin emissions, however standard copper smelters, designed for the treatment of mining concentrates or simple copper scrap, usually are lacking the necessary offgas treatment. Thus, on a global scale only a handful of integrated smelters have the capability to treat electronic scrap in an environmental sound way, but capacity in these few smelters is sufficient. Investments for state-of-the-art smelters are high, economies of scale are important. To build a plant like Umicore's Hoboken facility would need an investment of well over 1 billion US-$. Electronic scrap always is only one part of the smelter feed. It requires an elaborated mixing with other feed materials to create the appropriate chemical and physical properties for an eco-efficient treatment. Large amounts of fine dust of organic materials, e.g. shredder light fraction with metallic residues, can lead to problems since when fed into the smelter this can instantly burn off before reaching the metal baths. If such fine feed materials cannot be avoided, then a prior agglomeration (pelletizing or briquetting) makes sense. Both mechanical pre-processing as well as smelting and refining are important steps in the recycling step, which have to be seen in a complementary way. The challenge is to optimise the interface between these steps. Here we still see a lot of room for improvement.

5 Figure 2. Flowsheet of Umicore's integrated metals smelter/refinery V. THE NEED FOR INTERFACE OPTIMIZATION As pointed out before the highest value but also the highest environmental impact in the treatment of e-scrap is concentrated in the circuit boards. An optimized process chain has to find an economic way to minimize losses of precious metals, copper and special metals while safeguarding a controlled handling of toxic substances. In this context, some technical conflicts have to be overcome: Integrated smelters recover precious metals, copper and other base- and special metals but not aluminium or iron. Aluminium smelters recover Al but precious metals and other metals contained in the feed are lost. All non-ferrous metals are lost in fractions that go into landfill, incineration, steel plants, or plastic plants. This means, that large aluminium (and iron) parts as well as clean plastics, which can be valorized as such, should be separated from the feed before sending to an integrated smelter. On the other side, it must be strictly avoided that the preprocessing fractions sent to aluminium-, steel-, or plastic plants, respectively into landfill or incineration contain precious and other valuable metals. However, if circuit boards are mechanically pre-processed, such losses in sidestreams are unavoidable, the reason lies in the high complexity and intense interlinkage of the different metals, especially with respect to precious metals (PM), which are highly disseminated. They occur in boards with other metals in contacts, connectors, solders, hard disk drives, etc.; with ceramics in multi layer capacitors (MLCC), ICs, hybrid ceramics, etc.; with plastics in PCB-tracks, interboard layers, ICs, etc. Taking into consideration the technical limits of mechanical processes it becomes obvious that they cannot really liberate the precious metals in circuit boards. Although usually the major part of the precious metals ends up in the copper fraction (from where it can be recovered later on), still significant portions are found in other output streams. Especially the 'Al fraction' after eddy current separation often has considerable amounts of small circuit board pieces (with PMs). Without having had up to now the possibility to set up a detailed PMmass balance based on comprehensive mechanical preprocessing tests and sampling, various samples analyzed indicate that a precious metal loss of 20% in mechanical preprocessing of circuit boards seems likely. Table 3 shows the economic impact of a loss of such magnitude. The calculation is done for PC-boards, TV-boards and cell phones with a composition as given in II, with metal prices of February It was assumed that not only 20% of the precious metals are lost but also 20% of aluminium, copper and iron. The calculation gives the following results: Aluminium or iron losses have only a marginal impact on net value. Copper losses would make up for 7-42% of the value. Losing precious metals corresponds with a decrease in net intrinsic value of 43% to 93%. In absolute terms a 20% metal loss from PC-boards and cell phones represents a total loss of well over 1300 US- $/tonne. This is a very high value, also if set into relation to treatment charges in integrated smelters. Sending more, non-upgraded material instead of 'copper fractions' to smelters thus very often has a positive net effect. The calculation underlines that for complex, intensely interlinked electronic components/fractions with a relatively high precious metals density, mechanical pre-processing by shredding and sorting should be avoided. Examples are computer circuit boards and small electronic devices like cell phones, digital cameras, handheld computers etc. For these type of equipment it is the most eco-efficient way to feed them, after removal of batteries, directly into an integrated smelter as has also been shown by [10]. TABLE III. IMPACT OF A 20% METAL LOSS (PM, CU, AL, FE) gross intrinsic value* value share per metal US-$/tonne Ag/Au/Pd Cu Al Fe TV boards % 42% 11% 4% PC-boards % 14% 1% 0% cell phones % 7% 0% 0% metal loss 20% total loss loss per metal in USD / tonne US-$/tonne Ag/Au/Pd Cu Al Fe TV boards PC-boards cell phones Metal prices of Febr (rounded): in US-$/Troz: Ag 9.8; Au 550; Pd 290 in US-$/tonne: Cu 4800; Al 1300; Fe 150 * gross metal value without considering any losses during recycling nor any recycling costs. The more efficient the recycling chain is, the more of this value can be recovered net value.

6 For low-grade materials as small domestic appliances or many brown goods, the direct smelter route usually is not applicable and pre-processing is required. But instead of intensely shredding the material, often a coarse size reduction, by just breaking up the device e.g. using a chain mill, followed by manual or optical removal of circuit board fractions (e.g. color recognition with air blow separation) could be a valid alternative. The selectivity of trained workers in this context must not be underestimated. Whenever there is access to cheap but reliable manual labor, like in many developing and industrializing countries, manual dismantling, sorting and removal of critical fractions like circuit boards combined with state-of-the-art, industrial metals recovery processes can be a valid alternative. Such "best of two worlds" approaches are currently investigated in the frame of the StEP initiative by the United Nations University [11]. Altogether, a mutual optimization of sorting depth as well as of destination of the various fractions produced can lead to a substantial increase in overall yields, especially for precious metals. The principal window of optimization is shown in Fig. 3. There will be no general solution but individual best routes depending on type of e-scrap, companies involved and also regional aspects. For the practical implementation, requirements in this context are an open dialogue and cooperative approach between the relevant stakeholders, as well as transparent material flows up to the final destinations, which until now is not always the case. Further investigations, to which we are open to contribute, are necessary in this promising field. These include: Comprehensive testing and sampling of various lay outs of mechanical pre-processing considering all output fractions and sidestreams in order to obtain reliable mass balances for precious and non-ferrous metals. Holistic calculations of total costs, revenues and environmental gains for various interface combinations (quantification of Fig. 3). Development of smart pre-processing technologies for TV- and monitor boards to remove larger iron and aluminium parts without co-separating precious metals. VI. CONCLUSION Integrated metals smelters are a crucial part of the e-scraprecycling chain, which can further increase its efficiency if interfaces to pre-processing are consequently optimized. Their ability to recover numerous metals at high yields and without any 'downcycling' in quality can contribute to a significant future supply of secondary metals. Moreover, such operations can offer possibilities to utilize plastic fractions contained in electronics as feedstock substitute for coke. However not any 'copper smelter' can treat electronic scrap in an environmentally sound way, only a handful of plants in the world have the necessary installations for offgas and wastewater purification. Umicore's Hoboken plant has been developed to the globally most advanced full-scale processor of various precious metals containing fractions from electronic scrap, generating optimum metal yields at competitive terms. Costs Area of optimisation smelting costs preprocessing costs (incl. landfill) Preprocessing Intensity precious metal losses Figure 3. Qualitative cost functions in interface optimization In order to sustainably improve metals recovery from electronic scrap, the following routes should be followed: Improve collection of end-of-life electronics. Stop shipment of e-scrap to non-compliant and nonefficient destinations. Pre-sort materials in a way that the mix has no adverse effects on later material recovery from this category. Make sure that losses of precious metals and spillage of toxic/hazardous substances are minimized. Avoid deep mechanical pre-processing of computer boards, cell phones and other 'high-grade' materials. Remove such materials by appropriate manual or mechanical technologies for a direct treatment in state-ofthe-art integrated smelters. Use holistic approaches (entire chain) for evaluation of recycling processes. Do not optimize single steps without considering the impacts on the steps before and after. REFERENCES [1] J. Huisman, "The QWERTY/EE concept - Quantifying recyclability and eco-efficiency for end-of-life treatment of consumer electronic products," thesis Delft University of Technology, Delft, [2] R.B. Gordon, M. Bertram, and T.E. Graedel, "Metal stocks and sustainability", PNAS, vol. 103, pp , Jan [3] M. Reuter, "Pyrometallurgy - the key to sustainable use of materials", Erzmetall 56, pp , July [4] Basel Action Network, "Exporting harm - The high-tech trashing of Asia", Seattle, Febr [5] Basel Action Network, "The Digital dump - exporting re-use and abuse to Africa", Seattle, Oct [6] Umicore, Öko-Institut, GFMS, "Materials flow of platinum group metals", London, June [7] Singhal, P., "Integrated Product Policy Pilot Project. Stage I Final Report: Life Cycle Environmental Issues of Mobile Phones", Nokia: Espoo. 87 pp., [8] N. Gohring, "Mobile phone sales topped 800 million in 2005", [9] C. Hagelüken, "Recycling of electronic scrap at Umicore's integrated metals smelter and refinery", proceedings of EMC 2005, vol. 1, pp , Sept [10] J. Huisman, "QWERTY and eco-efficiency analysis on cellular phone treatment in Sweden", Delft, April 2004, unpublished. [11]