Heavy Lanthanides: An "Imminent Crisis."

[NNadir]

The paper I'll discuss in this brief post is this one: Heavy rare earths, permanent magnets, and renewable energies: An imminent crisis. (Karen Smith Stegen, Energy Policy 79 (2015) 1–8)

I came across it going through some old files (accessed in 2018), but had not read it, although the subject of critical elements has been a subject of considerable interest to me, and represents a big part (besides toxicology and wilderness preservation) of why I changed my mind on the issue of whether so called "renewable energy" is sustainable. It is clear enough that despite all of the mindless cheering for it (in which I, to be honest, used to participate) so called "renewable energy" has not addressed climate change, is not addressing climate change and, I contend, will not address climate change. This paper addresses that issue.

From the introduction:

In past years, many policy makers, scientists and other interested parties have urged reducing reliance on hydrocarbon energy sources in favor of renewable ones. Reasons for this range from concerns over global warming, oil price volatility and economic vulnerability, to the peaking of oil production or the general need for diversification in energy portfolios. Actually attaining the potential environmental, economic and political benefits of renewable energies will, however, require a massive build-out. This article sounds the alarm that one significant obstacle to this effort may be the scant supplies of certain critical materials: rare earth elements.1 These are conventionally divided into two categories: the more common light rare earths and the less abundant heavy rare earths, which are particularly needed for efficient lighting applications and for the permanent magnets used in many renewable energy technologies. Lately, the ‘rare earth problem’ has received considerable attention, and several publications have taken stock of the situation. These assessments include, but are not limited to, a flawed Wall Street Journal article belittling the possibility of shortages (Sternberg, 2014), a more accurate but overly optimistic report (Butler, 2014), as well as a rigorous evaluation (Golev et al., 2014). None of the recent reporting on rare earths accurately depicts the extent of the various challenges. In general, misconceptions about rare earths and rare earth-related industries are rampant. Rare earths are the linchpin ingredients of many high technologies for a wide variety of uses—ranging in application from military and medicine to entertainment, communications and petroleum refining, through to lighting and renewable energies...

...This article seeks to serve as a wake-up call to renewable energy advocates, whether government officials, policy makers, industry decision-makers or simply concerned citizens. We begin by providing background information on rare earth elements and permanent magnets, clarify several ubiquitous misperceptions about rare earths and outline the risks of heavy reliance on a single supplier. We then review and assess the various methods for addressing shortages and present the main issues associated with developing rare earth supply chains outside of China. The article closes with a discussion of the implications and several policy
recommendations.

The bold is mine, which is to reflect my feeling which would be amusing were it not so dire, that trying to "wake up" advocates of so called "renewable energy" to the fact that so called "renewable energy" is not, in fact, "renewable," is at best a Sisyphean task, but more likely, a Quixotic task.

One thing I have noted about advocates of converting every wilderness area into industrial parks for short lived wind "farms" - the use of the word "farm" is another example of, um, lying - is that they are in general, disinterested in replacing dangerous fossil fuels and are more interested in attacking nuclear energy, even though nuclear energy is the only sustainable form of energy there is and represents the only workable tool for addressing climate change. (As good as nuclear energy is, however, addressing climate change at all is increasingly a long shot.)

The author makes a distinction between the heavy lanthanides and the light lanthanides, which is a very important distinction, and one about which I've spent considerable time thinking, particularly with respect to dysprosium.

The ‘rare earths’ category, depicted in Table 1, refers to 15 chemical elements (numbers 57–71 of the periodic table) collectively known as the lanthanide or lanthanoid series plus two additional metals, scandium and yttrium, that are closely related. Although many rare earths were discovered one-to-two centuries ago, their value has only recently been discerned. The “unique magnetic, luminescent, and electrochemical properties” of rare earths makes them almost indispensable to many of today's technologies (RETA, 2014); for example, when used as additives to permanent magnets, they endow resistance to demagnetization at high operating temperatures.

Several of the rare earths used in renewable energy technologies and efficient lighting applications are considered critical, that is, at risk for short- and mid-term shortages. The United States (US) Department of Energy (US DOE, 2011) assessed the criticality of various materials to clean energy applications according to a two-part schema: the importance of each individual material and [page 3] the severity of the supply risks. Materials scoring high on both dimensions are considered “critical”, and those at medium or low risk are deemed, respectively, “near critical” or “not critical” (see Table 1). For both the short- (0–5 years) and medium-term (5–15 years) periods, five rare earth elements were placed in the critical category: dysprosium, neodymium, europium, yttrium, and terbium. Most of these are categorized as heavy rare earths: dysprosium, used in neodymium–iron–boron permanent magnets (for example, in wind turbines and electric vehicles); terbium, used primarily in lighting (terbium can also substitute for dysprosium, but is more expensive); and yttrium, used in lighting. Europium, used in lighting, lies between the light and heavy rare earths on the periodic table and is considered a heavy rare earth by some authorities (US DOE (US Department of Energy), 2011, Molycorp, 2012 and Alkane Resources, 2013) and as a light rare earth by others...

Although the chemistry of the lanthanides (aka "rare earths" as in this article) is very similar, which is why all of these elements, plus yttrium and scandium, are generally found together in ores, there is a very subtle but consequential difference in their chemistry which appears when the f shell is half filled, which occurs at europium. Europium itself is sometimes depleted in these ores because it, unlike the other lanthanides, has a very stable +2 oxidation state, which makes its chemistry more like that of barium and strontium than the other lanthanides, effecting the geochemistry of some ores. The elements after europium, except sometimes in some contexts gadolinium, have some differences in their geochemistry which makes changes to their distributions.

The author gives one - among many that are not mentioned in this paper - fairly good xample of the relevance of these elements, including dysprosium, to the utility of so called "renewable energy:

Rare earth permanent magnets are particularly important for clean energy applications and, currently, China accounts for about 80 percent of global production (Benecki, 2013 and Dent, 2014). Permanent magnets are divided into two categories: samarium cobalt and neodymium–iron–boron. According to an executive in the permanent magnet industry interviewed for this article, the two types have similar properties, but offer different advantages and disadvantages. Samarium cobalt magnets perform better at higher temperatures, but are brittle, which limits magnet size and can cause problems with integration into certain applications, such as motors. Samarium cobalt magnets do not contain dysprosium, but there are supply and price concerns associated with cobalt (US DOE, 2011). These magnets are used for small, high-temperature applications and are typically not found in renewable energy technologies.

Neodymium–iron–boron magnets are even stronger than samarium cobalt magnets and, because their size is not as restricted, they are more suitable for large applications, such as wind turbines and other electricity generators. These magnets typically contain two to four percent of dysprosium to enhance their temperature resistance. The advantages offered by neodymium–iron–boron permanent magnet to renewable energies are not inconsequential. Depending on the system, permanent magnets can increase efficiency—upwards to 20 percent—which translates into lower costs and shorter payback periods. For example, at least two major benefits can be derived from replacing the mechanical gearboxes in wind turbines with direct-drive permanent magnet generators: first, the overall weight of the turbine is reduced, which thus reduces the costs of other components, such as the concrete and steel required to support heavy gearboxes; second, reducing the number of moving parts allows for greater efficiency and reliability (Hatch, 2014; see also Kleijn, 2012). The advantages of permanent magnet generators are particularly salient for offshore installations, where reliability is paramount due to the high costs of maintaining and repairing turbines. Neodymium–iron–boron magnets are also used in other types of renewable energy technologies—such as underwater ocean and wave power (Dent, 2014). Additional potential applications that could use permanent magnets include small hydro applications, solar updraft towers (Hatch, 2008), geothermal drilling (Hatch, 2009), and heat pumps (rdmag.com, 2013). Several of these renewable energy technologies are in the prototype or testing stages. One factor that could impede their commercialization is the price of permanent magnets. Indeed: were the price lower, many existing renewable energy technologies could be re-designed around them, which could reap the same efficiency, size, reliability and, ultimately, cost benefits as they already produce for new technologies (Hatch, 2014).

Table 1:



The table gives a nice overview of the uses of these elements, omitting a few.

Many of the light lanthanides are fission products, some of which feature radionuclides with acceptably short half-lives that suggest they could be utilized directly after isolation. These are praseodymium, neodymium and lanthanum. The latter two contain radioisotopes that are very long lived and are in fact found in the natural ores as a result, for example Nd-144. Cerium contains the parent isotope of Nd-144, Ce-144, which has a half-life of 284 days, meaning that to utilize cerium in places where the radioactivity would not be desirable - there are many potential applications where the radioactivity would be desirable - would require up to ten years of cooling.

Promethium, element 61, is found only in used nuclear fuel and not in nature (except for very, very minor trace amounts from the spontaneous fission of natural uranium). It is not very long lived in the common isotope, 147, but has been utilized for permanent lighting applications.

Samarium and europium have very high neutron capture cross sections, and, as a result, are somewhat depleted in used nuclear fuels and are, in any case, the reason that nuclear fuel becomes exhausted in the current common nuclear reactors, before all the fissionable material is exhausted. I believe that in "breed and burn" reactors, they might serve (besides as control rods) as long term neutron shields for reactors that run for decades without refueling. Under these conditions, some of these elements would be transmuted into "heavy" lanthanides.

Used nuclear fuel however is not an option for the long term supply of lanthanides, since it has a high energy density.

The amount of plutonium required to meet all of the world's energy demands, shutting all the world's energy mining (including for many centuries, uranium mining or extraction from seawater), all the gas, all the oil and all the coal, is rather small.

Currently the world is consuming about 600 exajoules of energy per year. The amount of plutonium required to meet this demand is relatively trivial, about 7,500 tons per year, as compared with billions of tons of dangerous fossil fuels consumed each year.

These small quantities, and the fact that the lanthanides are only a fraction of the elements that can be obtained as fission products, suggests that the lanthanide problem cannot be solved by isolation from used nuclear fuels, as the yearly production would only represent a small fraction of world demand.

I wish you a happy Thanksgiving holiday.

[DetlefK]

1. Rare Earths are not "rare" per se.

They are "rare" in the sense that they are evenly distributed on Earth. We have copper-mines and iron-ore-mines and cobalt-mines... but there are no mines for rare earths.

That's why China is dominating the rare earth market:

1. China has regions where the concentration of rare earths is marginally higher.

2. Getting rare earths out of rock and soil requires massive and extremely dirty mining-operations and chemical refining. You can't really do that in the West because of enviromental regulations. The chinese government has no qualms about destroying the environment as long as it serves the interests of the Communist Party.