Enlarge /. The Chinese Bayan Obo mine currently produces about half of the world’s supply of rare earth elements.
The transition to electric vehicles and renewable electricity sources, which is now gaining momentum, is mainly about the renunciation of fossil fuels. However, to end our dependence on these substances, we increasingly need other materials – such as lithium and rare earth elements. Unlike fossil fuels, however, these materials do not have to be consumed when we use them. In principle, devices can be recycled at the end of their lifespan in order to return these valuable materials to a closed cycle that could ultimately minimize the need for mining.
But with solar systems, wind turbines and electric vehicles, which are entering the disposal phase in increasing numbers – while manufacturing is exploding – is a new recycling industry actually increasing in order to reap the benefits? For known and new reasons, the answer is “not really”. There is a lot of heavy lifting between here and a closed cycle for clean energy technologies.
I rarely prefer my earth medium
The so-called “rare earth elements” (or REEs) include the 15 lanthanide elements in the periodic table – lanthanum to lutetium – as well as scandium and yttrium directly above. Despite the name, most rare earths in the earth's crust are more common than gold or silver, although high quality ores are indeed difficult to get.
However, the REEs give electronics and energy technology slightly miraculous properties. Neodymium or samarium in magnets, for example, increase their effectiveness considerably, making these components smaller. Rare earths are also used to create the phosphor coatings in fluorescent lamps that are responsible for the color of the light emitted. And they are important for lasers, optics, nickel-metal hydride batteries – even for chemical catalysts for oil refining. For one reason or another, REEs find their way into telephones, electric vehicles, solar panels and wind turbines.
Enlarge /. The worldwide production of rare earth elements (including yttrium) has increased dramatically – shown here until 2015.
Of course, you are not alone. Wind, sun and vehicles also rely on steel, copper, aluminum, quartz, lithium, nickel and cobalt. Steel, copper and aluminum are already mature recycling industries as long as these components are obtained from the waste stream. And the lithium supply chain is currently receiving a lot of attention, from increased mining to battery recycling (which manufacturers are very interested in). In contrast, REEs were mainly discussed geopolitically, as China is responsible for the lion's share of mining and processing.
In a way, recycling is even more attractive for rare earths than for lithium due to the so-called "balance problem". While you visit the grain aisle and can only select the grain you want, rare earth mining means buying the entire aisle. Some of the rare earth elements are much more in demand than others, but the conditions found in ores bear no resemblance to their relative popularity. If you look at the lanthanide series in the periodic table, the most frequently used elements are found in the middle – for example neodymium and dysprosium. Most ores, however, are enriched with one or the other end of the series. They also often contain radioactive thorium and uranium, which is another level of complexity for mining.
Other elements may become more important in the future, but at least for now, it is beneficial to preserve your rare earths by recycling materials that already contain the mixture you want. Otherwise, with increasing demand for dysprosium, it could be difficult to produce ten times the amount of lanthanum to get the desired dysprosium.
Ores with high concentrations of rare earths usually fall into two general categories: igneous rock and weathered sediments. The igneous ores mainly consist of carbonatite – an unusual product of magmas that are rich in carbonate minerals. It is unusual enough that only one volcano in the world erupts carbonatite lavas, although others have done so in the past.
About half of the current global production of rare earth elements comes from the Chinese Bayan Obo mine alone, which contains many carbonatites. The Mountain Pass mine in Southern California along Interstate 15 has consistently mined similar rocks in its history.
The Australian Mount Weld spans the two categories rock and sediment. The ultimate source of REEs is carbonatite rock, but current mining focuses on the soil and sediment on that rock. This soft stuff is the result of the weathering that destroyed the bedrock, carried away some of the less resistant minerals, and further concentrated the rare earth minerals. Similar processes are responsible for deposits of ionic clays in China and mineral sands in India.
The different sources contain different ratios of rare earth elements.
"In general, all carbonatites are enriched with lanthanum and cerium," Simon Jowitt from UNLV told Ars. The reverse is the case with ionic clays; You get a lot less lights and a lot more heaviness. But what we actually want is some of the things in the middle. "
China has dominated production and processing (much of the ore mined elsewhere is still processed in China), although there are many other potential sources. When China attempted to curb exports in 2011 in the face of growing demand, rising prices led to the opening of new mines. A 2014 ruling by the World Trade Organization ended China's restrictions. Together with the increase in production in other countries and the efforts of manufacturers to lower demand, this stabilized the market again. However, work on new projects has continued to evolve, even if some only become economical when prices rise again.
Russia, Canada, Brazil, Greenland and the United States are home to significant undeveloped deposits. In the United States, for example, there is the Bear Lodge project in Wyoming, the Bokan-Dotson Ridge project in Alaska and Round Top in Texas – all at an early stage of development. After the recent trade war between the US and China, the US government continued to finance domestic processing plants in addition to these mines.
Enlarge /. Here is the breakdown of the identified deposits of rare earth elements.
But it's not just about brand new mines. Some mines that produce other metals have residues – crushed rubble – that are full of rare earths. India's mineral sand mines, for example, have generally targeted things like titanium, while setting aside the rare earth-bearing minerals. Stenkampskraal in South Africa and Mary Kathleen in Australia also have piles of uranium and thorium surgery left over.
"There is the type of nuclear carbonatite deposit," said Jowitt. "And then there is the type of 'well, these could be interesting if the economy is right …" And these are both different types of primary deposits and some of the secondary things – the kind of things that people are doing now are not interested But if the prices are right and garbage dumps are still available, they may be extracted in the future. "
Reprocessing this inventory could be a win-win situation because such residues often leach out hazardous substances when exposed to the elements. An economic incentive could lead to them being tidied up and not abandoned.