Saturday, November 19, 2011

Rare Earths

In order to build a functional post-carbon economy, one must have the materials to do so. This may seem obvious, but it is a point often overlooked, even by scientists.

So-called rare earth elements are used in just about every aspect of clean-tech, things like photovoltaic panels, wind turbines, hybrid batteries, even computer screens and cell phones (which are 'clean' in the fact that one can communicate with less travel). The thing is, these materials are finite. And some are even quite rare (despite the name, rare earths are not always rare, but sometimes are). And although the technologies they create may be considered "green", the mining of these materials is decidedly not.

Mother Jones covers the issue here:
Your Prius' Deepest, Darkest Secret (Mother Jones). Highlights:

Neodymium magnets turn wind turbines. Cerium helps reduce tailpipe emissions. Yttrium can form phosphors that make light in LED displays and compact fluorescent lightbulbs. Hybrid and electric cars often contain as many as eight different rare earths. And the stuff is good for more than just renewable energy technology. Walk down the aisles of your local Best Buy and you'll be hard-pressed to find something that doesn't contain at least one of the rare earths, from smartphones to laptop batteries to flat-screen TVs. They're also crucial for defense technology—radar and sonar systems, tank engines, and the navigation systems in smart bombs.

For the last few decades, China controlled the world's market for rare earths, producing about 97 percent of the global supply. But in late 2010, China cut its exports by 35 percent in order to keep the valuable metals for its own manufacturers. The prices of rare earths rose almost immediately.

But no matter how quickly new mines open, the United States won't be able to produce enough rare earths on its own—it's thought that North America contains only 15 percent of the world's supply.

Rare earths occur naturally with the radioactive elements thorium and uranium, which, if not stored securely, can leach into groundwater or escape into the air as dust. The refining process requires huge amounts of harsh acids, which also have to be disposed of safely.

Mines in China have a particularly terrible record of contamination. Communities around a former rare-earths mining operation in Inner Mongolia, for example, blame hundreds of cases of cancer on leaked radioactive waste from the mine, and local people complain that their hair has gone white and their teeth have fallen out.

This creates a real dilemma: What good is green technology if it's based on minerals whose extraction is so, well, ungreen? Most of the experts that I talked to agreed that the elements are just too useful to give up on. "We need this stuff," says Jim Kuipers, an independent mining consultant in Montana. "It's just a matter of figuring out how to do it right, and unfortunately, the mining industry doesn't have a strong history of doing this."

Here's National Geographic on the subject: The Secret Ingredients of Everything (National Geographic)
Rare earths, as the elements are called, were discovered beginning in the late 18th century as oxidized minerals—hence "earths." They're actually metals, and they aren't really rare; they're just scattered. A handful of dirt from your backyard would probably contain a smidgen, maybe a few parts per million. The rarest rare earth is nearly 200 times more abundant than gold. But deposits large and concentrated enough to be worth mining are indeed rare.

The list of things that contain rare earths is almost endless. Magnets made with them are much more powerful than conventional magnets and weigh less; that's one reason so many electronic devices have gotten so small. Rare earths are also essential to a host of green machines, including hybrid cars and wind turbines. The battery in a single Toyota Prius contains more than 20 pounds of the rare earth element lanthanum; the magnet in a large wind turbine may contain 500 pounds or more of neodymium. The U.S. military needs rare earths for night-vision goggles, cruise missiles, and other weapons.

"They're all around you," says Karl Gschneidner, a senior metallurgist with the Department of Energy's Ames Laboratory in Ames, Iowa, who has studied rare earth elements for more than 50 years. "The phosphors in your TV—the red color comes from an element called europium. The catalytic converter on your exhaust system contains cerium and lanthanum. They're hidden unless you know about them, so most people never worried about them as long as they could keep buying them."

Now a lot of people are worried.
Related: How Much Is Left (Scientific American interactive feature).

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