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Secondary metals, recycled from defunct products, provide valuable supplementary resources. But secondary stock will never meet growing demand. And recycling has technical limits.
From mobile phones to motor vehicles, technology metals are used in myriad applications. Up to 60 different elements go into the manufacture of microprocessors and circuit boards6, usually in tiny quantities and often in combinations that are not found in nature.
Whether a metal can be recovered once a device is defunct depends on the element's value, concentration and accessibility when it is combined with other materials7. Precious metals — platinum-group metals and gold — are the main target in the processing of used circuit boards. Lower-value copper, antimony and indium can be recovered at the same time. But metals such as tantalum, gallium, germanium and rare-earth elements are oxidized and effectively lost in the smelter slag1.
Recycling technology metals is most economically attractive when they are highly concentrated, for example in manufacturing scrap. Around 70% of the indium used in producing flat-screen displays, for example, finds its way into scrap, which is then recycled8.
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To fix bottlenecks and inefficiencies requires measuring technology-metal stocks and understanding how they flow through the whole supply chain — from mining to concentration, extractive and process metallurgy, manufacturing, use, reuse, recycling, dispersal and disposal9. For instance, improving recovery technology at tungsten mines would increase the amount of the metal in the ore that ends up reaching the smelter (just 75% for tungsten, in contrast to 90% for gold).
In theory, more than 90% of platinum-group metals used in autocatalysts can be recovered. In practice, only 50–60% is retrieved from European scrap cars because many vehicles are exported second-hand to places that lack recycling facilities. Analysis of metal flows could show whether a scheme to retrieve lost catalytic converters would be more effective than another type of scheme, such as a 2011 proposal by a UK waste-management company to recover these metals from road sweepings. Autocatalysts contain about 0.2% platinum-group metals; sweepings contain less than 1 part per million10.
Addressing technological barriers to resource efficiency in this way is a focus of initiatives, such as the European Innovation Partnership on Raw Materials — a network of European countries aimed at increasing the availability of raw materials across the region.
However, mapping the life cycle of critical metals is challenging. The volumes are low; extraction, processing and recycling are handled by just a few organizations; and commercial confidentiality can make data and contacts hard to find.
One system
In the past five years, concerns over securing supplies of technology metals have evolved from near-panic over physical depletion and Chinese geopolitical muscle-flexing, to a dangerous assumption by some policy-makers that recycling is the panacea. A more holistic approach is needed.
Primary and secondary sources must be considered as part of one system that needs to be wholly understood. Basic statistical data are crucial. Better dialogue between producers, processors, consumers and recyclers will be needed. Policy-makers must assess how technology metals are used and combined, and the impact this has on the economic and environmental viability of recycling them.
The benefits of securing supplies of technology metals are clear. Improving the efficiency and reducing the environmental footprint of extraction and processing of these metals from primary sources is a major opportunity for industry and researchers.
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