Emerging green technologies such as photovoltaics (PV) and solid-state lighting (SSL) heavily depend on the use of raw materials like gallium, indium and rare-earth elements. Figure 1 shows the projected growth for gallium and indium, indicating that global supply will increasingly lag behind on demand if the current circumstances pertain.

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Figure 1  World-wide supply and demand forecasts for gallium (left) and indium (right)

 

 


The growing demand is driven by PV, SSL (notably light-emitting diodes, or LEDs) and electronics (integrated circuits) for gallium and by PV and electronics (liquid-crystal displays, or LCDs) for indium. Meanwhile the primary production and trade of these materials is highly controlled by a few countries and particularly by China. A further complication for both gallium and indium is that they are mined as by-products of other materials.

The group of the rare earths (RE) consists of yttrium, scandium, and the so-called lanthanides, e.g. europium. For rare-earth elements a similar tight situation exists with global annual demand being projected to rise to 170,000–190,000 tonnes by 2014 and associated Chinese production of 160,000–170,000 tonnes being subject to export cuts.  Various sources estimate that phosphors represent 4 to 15% of the rare-earth market, with the most recent estimates ranging from 7 to 11%. Within this sub-group, there are three main applications: televisions (plasma, liquid-crystal display and cathode-ray tube), fluorescent lamps, and X-ray intensifying screens, with currently few – if any – suitable substitutes for the used phosphors available. As an example of how critical market conditions currently are, the rare-earth tri-phosphor in a general-service fluorescent lamp can be the highest material cost component (depending on the lamp type). With yttrium and europium being the most important rare earths for lighting applications, this places a particular emphasis on the availability of these specific key metals. 

The previous obviously poses a problem as it renders Europe particularly susceptible for the provision of these increasingly scarce materials that are crucial for meeting policies on energy renewability and energy saving as well as for the further development of these sectors with apparent economical and employment implications. This is also expressed by a recent EC report that qualifies gallium, indium and rare earths to be the numbers one, two and four in terms of criticality for emerging technologies in the long term (2030). 

The situation for gallium and indium on the one and rare-earth elements on the other hand is somewhat different though, as the former are almost exclusively used in electronics (including PV and SSL) while the latter also have several other applications (including metallurgy, magnets, catalysts and polishing agents).

Recycling systems to reclaim these materials from waste from electrical and electronic equipment (WEEE, or E-waste) such as TV sets, computers and mobile phones are not yet in place which severely challenges the sustainability of these technologies. Further to that, one of the main barriers to virgin sources of such key metals is in the time delay for starting up new mines (or reviving existing ones) due to their capital-intensive nature and the regulatory requirements. Reports by USGS show that it takes between 2 and 17 years (with an average of just below 10 years) from the start of the (post-exploration) process to commercial production.


Hence there is a strong need to establish recycling systems for PV, SSL as well as for other electronic waste to reclaim gallium, indium and rare-earth elements and capitalise on these as yet unexploited and growing deposits of key metals. Figure 2 shows that especially these new classes of products contain a variety of key metals in a diversity of compounds, noting also that these generally appear in overall low amounts per product.

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Figure 2  Allocation of the targeted key metals in current and prospective E-waste types

 

 

Current bottlenecks are in the isolation of the parts with the targeted materials from the waste and in the extraction and purification of these materials to bring them back to specification. More in particular, the concerned materials tend to be used as compounds (gallium arsenide, gallium nitride, indium oxide) rather than in their elemental form and as thin layers on substrates in overall very low amounts. Further, recycling of discarded products will have to handle multiple sources of waste of various and undefined compositions.
Table 1 lists the main research and technological development areas as well as the project objectives to be achieved within the RECLAIM project. The prospective recycling technology should be able to reclaim the targeted materials from present and future E-waste, be it in the metallic form or in compounds (oxides, sulphates, nitrates or phosphates), depending on the specific requirements for re-use. Boundary conditions for the processes to be developed are that they are apt to fit in an industrial context and are environmentally compliant (to the European situation).


Table 1   Scientific and technological project objectives

AREA

OBJECTIVES

Separation

Processes for the disassembly, disconnection and sorting of E-waste to isolate the parts containing the targeted materials, including proper identification techniques (³80% separation efficiency)

Dissolution and recovery

Processes for the selective extraction of the targeted materials from their carriers (reclamation efficiency for gallium, indium, yttrium and europium >95%)

Concentration and purification

Processes to remove undesired contaminations from the targeted materials and bring them to specification for renewed use (purity for gallium ³99.99%, indium ³99.99%, and yttrium and europium ³99–99.9%)*

Impact assessment

Eco-efficiency profiles for high-value recycling routes that give directions for optimal closed-loop recycling, including that on a regional scale

Demonstration

Pilot implementation of a recycling facility in an industrial setting with newly developed unit operations for separation, dissolution/recovery and concentration/purification for selected waste streams on a pre-production scale (output: 5–15 g/day for gallium and indium and 30–100 g/day for yttrium and europium oxide)

Economically viable technological solutions that relieve current bottlenecks hampering recycling of gallium, indium and the rare-earth elements yttrium and europium

 

* Representing commercial-grade quality (for the rare earths depending on the specific element)