Rare earth elements used by Prius to be in short supply

BUT, they are less abundant in the nature than oil, aren't they?

 

It's hard to recycle CO2 back into petrol.

 

Maybe someone who owns a chunk of these commodities revisits this story every few months to drive the market price up and make some coin. All this stuff will get recycled and reused. Thats what makes it different than oil.

 

Without doing the math, I am going to assume they are much more common than oil. With the exception of promethium, with is unstable, all of the rare earth elements are relatively abundant. Cerium, as an example, is the 25th most abundant element in the earth's crust. I can't picture petroleum coming anywhere close to that.

The problem comes from extraction. Petroleum, until recently, sat in nice pools close to the surface. Rare earth elements are scattered about and difficult to extract.

Tom

 

I was wondering about this. How much does the battery weigh? Is lanthanum really that large a percent of the total weight of the battery?

 

Let's not overlook the fact that the article not only included Prius electronics, but wind generators as well. On the basis of my observations of wind generators in the field, I would guess the generators are enormous! There has to be a great deal more rare elements in their windings.

Remember .... after all is said and done, there is generally more said than done.

 

Yes. Many SUV's have TWO large catalytic converters so they might have 3x the platinum used in the Prius.

 

The major use of rare earth elements in Prius probably is in the nickel-metal hydride battery. Lanthanum or other "rare earth" metals are used in conjunction with another metal such as nickel. We are talking pounds of material per vehicle here.

This has been much discussed elsewhere.

If lithium batteries are practically around the corner, this is even a lamer discussion.

 

I think it is about right. Lanthanum is the metal, or "M" in NiMH. The Nickel and Lanthanum are aranged in a lattice structure with Lanthanum atoms on the corners of a cube and Nickel atoms inside the cube. The Lanthanum atom is heavy, more than twice as heavy as a Nickel atom, so overall it seems reasonable that there is a roughly comparable weight of Nickel and Lanthanum in the battery.

 

Most wind turbines use induction generators, which don't require rare earth elements. Some of the new very large units use permanent magnet generators, which do use rare earth in the magnets, but at this stage most don't.

The trend is toward permanent magnet generators because of efficiency, but at this point there aren't many of them, except for little residential and marine units.

Tom

 

I accept your statement, because clearly, I have no idea. I was merely noting that the article that all this was predicated on, mentioned wind generators.

 

I'm pretty sure that's the wrong way round, that the negative electrode material is AB{5}, 5 atoms of nickel for 1 atom of mischmetal (lanthanide composite). The positive electrode is nickel hydroxide, Ni(OH){2}.

Mischmetal is used because it's actually easier to use a composite of lanthanides, as they're so chemically similar that it's hard to extract any one of them from the ore they occur in. Neodymium is usually extracted first for the magnetic material. What's left is a mix of lanthanum and cerium, or lanthanum, cerium and praesodymium.

Lanthanum weighs 138.9 grams per mole, while nickel weighs 58.7 grams per mole. Lanthanum therefore would make up 32.1% of the negative electrode. Nickel makes up the other 67.9%, plus 63% of the positive electrode. I'm not sure of the relative weights of the two electrodes though - I believe they are made to be about the same size, rather than weight, so it depends on the relative density. Only the very surface of the material is involved in the reaction, so they're made up of a lot of very thin plates that are interleaved within the cell.

In addition you have to add the weight of the electrolyte (potassium hydroxide in water) and the casings.

 

I was not implying there is only one Nickel atom in the lattice, just that all of them sit within the lattice. If there was only one the numbers would not make sense at all. There are for sure more Nickel atoms than La, but as you say they are a lot lighter. I couldn't find a proper image, but maybe this one is close:

http://www.bnl.gov/bnlweb/pubaf/pr/photos/2001/dumbbell2-w.gif

It was a very handwavy analogy in response to the poster that wondered if the Lanthanum could possibly be a significant fraction of the weight. So all I was trying to say is that the overall La could quite reasonably be 10kg, ie not vastly different from the weight of Nickel. I'll try to be clearer next time.

 

As for catalyst in the emissions control, there is only about 2 grams of Platinum in a C1 converter. The material is used as a coating and has a surface area of something like 5000 square yards, so it is VERY thin. However, Pt catalyst are not particularly efficient at lower temperatures and have been superceded in a large degree by palladium catalysts, which work better at low temperatures, this is called a C2 catalyst. Finally, some of the big SUVs may also have a C3 catalytic unit to clean up the NOX emissions. C3 units use rhodium, the best low temperature catalyst and tops in converting nitrous oxides back into N2 and O2. Rhodium is very rare and very expensive, but big SUVs can afford a more expensive solution than a Yaris. This is probably how Ford got the Excursion to be listed as a "green" vehicle. I think the TDI VW also uses a C3 catalyst for NOX reduction, at least the last model. The US leads the world in reclaiming precious metals from the catalytic converters with more than 60% recycled.

 

I didn't mean to imply that wind turbines are not a resource issue. PM motors and generators are getting more and more common, and wind turbines are being installed in large numbers. Ultimately they will consume a fair amount of rare earth material.

Tom

 

China tries to calm unease over curbs on rare earths exports but says limits needed

China tries to calm unease over rare earths curbs - Yahoo! Finance

 

Looking at the US Geological Survey's Mineral Commodity Summary