This chapter is based on extensive practical experience, research projects, and literature study. It addresses the key question related to metal production, supply, and recycling: What is the loss for a metal along each step in its entire metal/product life cycle, now and in the future, and how is this influenced by the social, economical, and technical factors present throughout the entire life cycle?
Answers are explored, providing guidance to optimize the life cycle and its subsystems in a sustainable manner. Emphasis is on the end-of-life (EoL) phase, as well as on losses that occur during primary production and manufacturing. To develop these issues and to identify interdependencies and potential conflicts in a comprehensive system approach, precious and special metals are used as examples for various reasons: Some of these metals are regarded as critical in the current scarcity debate, as they have significant relevance for clean- and high-tech applications, are valuable both from an economic and an environmental perspective, and face specific supply challenges since they derive mostly from coupled production with other carrier metals.
Losses occur at every stage of the life cycle and, especially for by-product metals, only a part of what is mined with the ores is finally supplied as metal to the market. Further significant losses occur during high purity upgrading and product manufacturing. However, the biggest issues are related to no or inefficient recycling of EoL products; this is especially true for consumer products due to the open character of their life cycles. Additional technical challenges stem from complex material compositions in components and often low concentration of metals, which are distributed over various parts of the final product. As a result, the actual recovery rate along the recycling chain, even in the European Union, is well below 50% for precious and special metals.
Improvement can only be achieved through a holistic, global system approach aimed at enhancing resource efficiency and metals recovery throughout the life cycle. Consumer awareness, effective collection, and monitoring of EoL flows in a quantitative manner are necessary prerequisites. Efficient, often high-tech recycling technologies exist, but optimized interfaces and supportive new business models are needed to overcome the structural deficits in the life cycle. Consequent use of available tools and technologies can significantly contribute to a more sustainable metals supply and use, now as well as in the future.
Metals and minerals are classical examples of nonrenewable resources, and their extraction from Earth by mining of ores cannot be seen as sustainable in the strict sense of the word. Mining, by definition, depletes ore reserves. Through mineral processing and subsequent smelting and refi ning, ores are disintegrated, and the desired substances (e.g., specific metals) are isolated. Other unwanted ore constituents are fundamentally changed in their appearance, deposited back to the environment as tailings or slag, fumed to the air, or dissolved into processing effluents.
If, however, the focus is less on the ore in a certain specific modification and more on its metallic ingredients, and if the system boundary is extended to its entire utilization cycle, the picture looks somewhat different. Metals are not lost or consumed (except those used in spaceships and sent into outer space); they are only transferred from one manifestation to another, moving in and between the lithosphere and technosphere. Whether products and (production) wastes constitute a future source for metal extraction depends on physical parameters such as concentration, "deposit" size, and accessibility as well as on social, technical, and economical parameters. In an ideal system, the sustainable use of metals could be achieved by avoiding spillage during each phase of the product life cycle (i.e., during mining, smelting, product use, and recycling/ recovery of the metals).
Our current situation differs significantly, however, from this ideal system. Life cycle and recycling systems are far from optimized for a number of metals; in particular, precious and special metals are very susceptible to suboptimal life/utilization cycles. Depending on the metal, losses can vary between small and very large. As a result, a discussion on materials security has arisen again for a number of metal resources, focusing on potential scarcities and the impacts of supply constraints (Gordon et al. 2006; Wolfensberger et al. 2008). This discussion requires quantitative information on the metal reserves (ore bodies and EoL products) and flows. In addition, it is necessary to pinpoint where in the (supply) chain other factors (e.g., the availability of specialist production and expertise rather than material availability itself) cause the bottleneck (Morley and Eatherley 2008). Furthermore, interactions and interde-pendencies between metal cycles and future needs and developments must be included in the discussion of materials security.
For some aspects, valid quantitative data sets for metals are available, such as geological reserves and resources (ore stock), mine production, demand by application, and region. Less data are available on in-use stocks in durable products and infrastructure, and thus we rely heavily on assumptions about in-use losses, product lifetimes, and hibernating products. Data about potential metal stocks in waste deposits are rarely available. The modeling of metal stocks and fl ows made valuable contributions for a number of metals (e.g., Bertram et al. 2002; Boin and Bertram 2005; Elshkaki 2007; Reck et al. 2008). The assumptions used in these studies indicate that the lack of data becomes larger when the scope of the investigation becomes smaller. Data on global or country levels are relatively easy to access, whereas data on the process level (including material efficiencies) are much less available. Nevertheless, this information is a prerequisite to predictions and quantitative assessments on what is happening in the life cycle, how great the losses are, and what optimization potential exists.
The biggest challenge relates to the EoL phase of (metals in) products. Some of the open questions in this context are: How much of the EoL products enter into a recycling channel? Do discarded products accumulate in a controlled/ centralized location, which could be a future metal resource, or are they widely dispersed so that future recovery is impossible? How do (old) products flow around the world, and what will be their fate at their final destination? What is the effectiveness of each recycling process and of the combination of processes in a recycling chain? How can single metals be effectively recovered from complex multi-metal assemblies in a product? What is the impact of product design/lifetime and social/societal factors on the previously posed questions?
Formulated into one key question, we ask: What is the loss for a metal along each step in its entire metal/product life cycle now and in the future, and how is this influenced by the social, economical, and technical factors present throughout the entire life cycle?
In this chapter, we explore possible answers to this question and provide guidance as to how the life cycle, and all its subsystems, can be optimized in a sustainable manner. Our emphasis is on the EoL phase, as well as on losses that occur during primary production and manufacturing. To identify interdepen-dencies and potential conflicts in a comprehensive system approach, we use precious and special metals as an example for the following reasons:
• Precious and special metals1 are rather expensive and thus offer economic incentives for recycling. In areas where recycling fails, structural limitations can be more easily identifi ed than for metals where economic and technical constraints are mixed.
• Most of these "minor metals" (defined below) are by-products from ores of a major or carrier metal. This has particular implications when interpreting reserves and mine production.
Precious metals are (complete list): Gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir) and osmium (Os). Special metals are (among others): antimony (Sb), bismuth (Bi), cobalt (Co), gallium (Ga), germanium (Ge), indium (In), lithium (Li), molybdenum (Mo), rare earth elements (REE), rhenium (Re), selenium (Se), silicon (Si), tantalum (Ta), tellurium (Te).
• Precious and special metals are widely used in complex, multi-metal products with often very low concentrations per metal. This implies significant technology challenges in recycling, as minor metals are coupled to each other and major metals, but differently than in ores.
• Their low concentrated ores and complex production processes imply a significant environmental impact of their primary supply (Table 10.1), making efficient recycling even more relevant.
• Most of these metals are used in "clean-tech" or "high-tech" products and have experienced tremendous growth over the last years. They are seen as a vital resource for the future, and some are seen critically in terms of supply security. The expression "technology metals" is increasingly used to underline their crucial function.
Throughout this chapter, statements and ideas will be illustrated with examples specific for one or more precious or special metals.
As in many other publications, the expression minor metals will be used, although no clear definition exists. "Minor" can refer to metals that have relatively low production or usage, which occur in low ore concentrations, are regarded as rare, or are not traded at major public exchanges (e.g., the London Metal Exchange). The term is also used for "special metals" that have rather unique properties without being major or mass metals (see, e.g., MinorMetals 2007). In the context of this chapter, these specific useful properties, which make them valuable for high-tech applications, constitute the key issue of what is understood as a minor metal. A further important feature is that most minors
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