We often hear that renewable energies are big consumers of rare earth elements. Criticised for their environmental impact related to their extraction and processing, rare earth elements are however only weakly used in the renewable industry. A study published by ADEME provides an update on the state of the sector, its applications in industry and particularly in renewable energies.
What are rare earth elements?
Rare earth elements consist of a set of 15 to 17 metal elements of the Periodic Table. They are divided into two groups:
- The light rare earth among which we find the neodymium which enter in the composition of the permanent magnets;
- The heavy rare earths including dysprosium which is also found in permanent magnets.
State of the deposit
Contrary to what their name suggests, rare earth elements are abundant in the earth’s crust. It is the small number of ores made up of these elements and their highly localised deposit that make them a critical material.
In 2017, rare earth reserves were estimated at 120 million tonnes of all rare earth oxides combined. China is the leading producer of rare earth elements, with nearly 86% of world production in 2017. However, the market is becoming more diversified as Australia and the United States are also producing. It should be noted that Greenland has one of the largest deposits in the world, for which the Chinese have already taken stakes in exploration.
In which applications do we find rare earth elements ?
Rare earth elements are used in multiple applications. They are mainly used to produce permanent magnets because they reduce the volume and weight of electric motors and generators. This represents 89% of applications for neodymium and 98.5% for dysprosium. Rare earths are also used in the following technologies:
- Catalytic pots of cars and petroleum refining;
- Glass polishing, heavily used for TV, smartphone and computer screens;
- Certain type of battery (Nickel Metalhydride batteries – NiMH) used in particular in hybrid vehicles.
Their environmental impact
Extraction of rare earth elements, like other extractive industries, generates environmental damage both during extraction and processing. Extraction modifies the landscape, the soils and the local hydrographic regime. The separation of metals releases pollutant treatment residues into the air and into the groundwater. Heavy earth deposits also have the particularity of inducing also a radioactive pollution related to their composition (presence of uranium and thorium in the ores).
The place of rare earth in the renewable industry
Most of current renewable energies do not use rare earths. Certain segments of wind power technolgy, and particularly off-shore technology, consume rare earths through the use of permanent magnets which reduce the weight of the turbines. On-shore wind turbines using permanent magnet technology are very rare in Europe. In France, only 3% of the on-shore park are using rare earth elements. In addition, the research and development projects carried out by the manufacturers do not seem to indicate an important need for permanent magnets. This trend shows that the problem has been integrated by the manufacturers.
At the solar photovoltaic level, the major proportion of commercialised technologies does not use rare earth elements. However, some technologies such as “thin films” use other critical metals such as tellurium, cadmium or silver. However, this type of technology remains a minority on the photovoltaic market.
And at the level of energy storage?
The most widely deployed technologies in the use of renewable energy storage are currently Lithium-ion, Sodium-Sulfur and Lead-acid batteries in which rare earth elements are weakly used. Nickel Metalhydride batteries used in hybrid cars include rare earth elements but their use for renewable energy storage purposes will remain highly marginal due to their high cost compared to Lithium-ion batteries. Note that the use of Cobalt in Lithium-ion batteries is much more problematic in that it is a critical material.