Rare earth metals recovered by bacteria

19 May 2014

Interview with

Lynne Macaskie, Birmingham University

Microorganisms might hold the key to the future of precious and rare metal recovery, Rare-earth oxidesand also to detoxify the chemicals that can leach from deposits of mine tailings or "slag heaps".

Birmingham University's Prof Lynne Macaskie, works on microbes that can do this. She's recenly been to Cape Town and Canada.

Kat - Tell me, why are these mine tailings or slag heaps such a threat to our environment?

Lynne - They're a big threat because unless the area is contained very well, the toxic elements, the metals and other things can actually migrate away from the source and through the environment and have an environmental impact. So, there's a lot of scope for environmental damage.

Kat - And what kinds of metals? What sorts of contaminants are we talking about and why are they damaging in the environment?

Lynne - Well, the main metal of interest that's being mined obviously whether that's copper, nickel, uranium, but other elements that are there as well which may not be immediately of interest can also have toxic effects on the ecosphere, plant life, animal life. One example of this is where historically, people were mining for uranium and they ignored another set of elements which were often present called rare Earth elements. Now that they in themselves are not too toxic, not as toxic as some are, but they're now becoming quite valuable. So, the interest is refocusing on getting as much benefit as possible from the slag heaps.

Kat - Basically, you've got all these rare Earth metals sitting in slag heaps, why are they so useful? Why do people want to get them out?

Lynne - They're absolutely key to the 21st century technologies. They're used in magnets, electronics, phosphor screens, LEDs, TV screens and a lot of the time, they're not replaceable by anything else. And so, as technology is moving forward, we are coming to rely on these elements. The problem is, not that they're rare. They're actually very common. It's just very, very difficult to get them out and commercial processing is something like a hundred different steps. It's very tricky. It's very expensive. It's been developed in China mainly and so, China largely controls the global supply of these elements.

Kat - So, how are you trying to get these rare Earth minerals out of the slag heaps.

Lynne - As we heard on the piece from Africa, some bacteria can actually take up minerals, take up elements and some will take up gold, some will take up copper. Some will actually take up rare earths. But of course, the tricky part is choosing your bacteria so that effectively, you can put them into different pots. You don't want a complete mixture because then you've got the problem of separating them. So, I think the future lies in getting separation, getting bacteria to take some and not others.

Kat - And so, where are you at the moment with your research? Do you have some bugs in the lab that can actually eat specific metals and minerals?

Lynne - We do have some bugs already. But we're just starting to embark on looking at natural deposits, finding out what bugs are in there. And this story about bugs being found at 70 degrees way below ground is so interesting, so exciting because it's opening up a whole new area of science that hasn't been explored yet.

Kat - Do you think that there are going to be just naturally occurring bacteria that could be useful for this or would you look towards genetically engineering specific capabilities into bacteria?

Lynne - Nature is very clever, given millions of years, things evolve. Quite often, people will genetically engineer a microbe, and then find something else that's engineered itself in the environment. And obviously, there's a lot of resistance still to releasing genetically modified microbes. So by and large, we tend to try for natural microbes where we can.

Kat - What kind of benefits do you think there could be if you could actually successfully get these rare Earth metals out?

Lynne - Well the environmental benefits are obviously strong, but these elements are so, so valuable and the price is going up. Everybody thinks of gold and platinum as precious metals. But actually, we're not short of gold and platinum. There's plenty of that, but we don't yet have the technology to harvest rare earths from the environment in an efficient way, that's cost-effective. So potentially, there's a lot of economic benefit to be gained. And in fact, in parts of Canada, they've got huge areas of tailings ponds where they've taken out the uranium for the nuclear industry and they're left with huge tailing ponds full of these rare earths. At the moment, they're seeking exploitation licenses to go back to these historic deposits.

Kat - I was going to say, it sounds like they're sitting on a gold mine, but obviously, it's a rare Earth mine. In terms of just getting the bugs in and out, would you just be taking bacteria out and purifying them or isolating bacteria, bunging them in there, making them grow, and then taking them back out again.

Lynne - Well, it's a very large problem obviously. It's not just a small hole. It's a very, very big hole. So, there's a lot of technology to be developed to try to make it a manageable size. And part of the bottle neck is, it's quite difficult to do pilot plants because you've got to construct a smaller version to try out. Also, the actual composition of the material differs from mine to mine.

Kat - What kind of timescale briefly are we talking about here that you could maybe start getting metals out? What would you hope for?

Lynne - We would hope to start getting the metals out and proving the technology in principle within 2 to 3 years. But obviously, getting it up to plant scale will be much longer than that, somewhere between 5 and 10 probably. And don't forget also that you have to convince the wider public and the governments that you're not going to end up making a larger mess you started with.

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