Report: Recovering just 1% of mining waste could reduce reliance on imported critical minerals

Here’s a startling fact for you: There’s enough lithium in one year of U.S. mine waste to power 10 million electric vehicles.

That’s one of the main findings of a new study by Elizabeth Holley, associate professor of mining engineering at the Colorado School of Mines. As Grist put it, U.S. mines are literally throwing away critical minerals.

And lithium isn’t the end of it. Holley and her team found that if we recovered 90% of byproducts from existing domestic metal mining operations, we could meet almost all of our country’s critical mineral needs. Just 1% would reduce our reliance on importing these minerals — which power everything from smartphones to solar panels to electric cars.

Right now, all of those critical minerals are thrown away — labeled as waste as miners extract copper, for example, and discard the rest of the rock they pull from the ground.

Now, researchers are trying to spark a conversation about how to rethink mining in the U.S. — and what’s labeled as waste.

Full conversation

ELIZABETH HOLLEY: So imagine that we're going to excavate a bunch of rock and then we're going to use equipment to make the particle size smaller. And then we use extractive metallurgical techniques to get out the things that we want. So in analogy to you in your kitchen, you might be cooking with, I don't know, a lemon. And you realize that you've squeezed some juice out of the lemon, but there's more left.

The question is, do you throw the lemon away or do you try to get more things out of it before it becomes waste?

LAUREN GILGER: Right. OK, so a lot of what is extracted in the rock when mining operations are happening is labeled waste. But you found that maybe it shouldn't be labeled that.

HOLLEY: I think there are a lot of things that are of value that are in what we treat today as mine waste. The problem is the economics of a mining operation are designed around that main product. So if it's a copper mine, it's copper that drives the economics of the mining, and it might not be worth it for the operator. If you think about market prices for something like gallium or germanium, the prices are very low.

And so is it worth it to that operator to add additional infrastructure into their processing flow sheet? And that might not be worth it. So the rest of that, including the things that we want, then becomes waste.

And in many cases that waste is tailings. So that's very fine grained material. Rock that's been ground to a really, really small grain size. And it's treated as a slurry. And it's put behind a tailings dam. And it has to be monitored, usually in perpetuity, to make sure that it doesn't cause environmental impact.

Colorado School of Mines

GILGER: Right. In perpetuity is right. There's lots of controversy surrounding mine tailings and what happens to them and how we keep them safe or keep people safe from them in that way.

But you're talking about some things that are not of a lot of value kind of wasted in this. But you also found that there's a lot in that waste that is critical right now — lithium, for example.

HOLLEY: That's right. And so when I say value, I think we need to differentiate between the market price, so what are people willing to pay for something, and its usefulness to society.

So the elements that are designated as critical right now are really important to our economy, and our economy would suffer if there were to be a supply chain disruption.

But the market price for some of them might not be very high. That's why it's difficult for operators to justify recovering perhaps all of the metals in a rock that might not be realistic economically.

GILGER: Yeah, I want to get to the policy in a moment, but let me just drive this point home, because this is, it's kind of wild.

Lithium is, for example, a mineral that we need for, like, electric vehicles ... will be in great demand and isn't mined very often in this country. You found there's enough lithium in one year of US mine waste to power 10 million electric vehicles. Is that right?

HOLLEY: That's right. And if you think about it another way, the question is: How much of this potential byproduct, lithium or any other byproduct element could we recover?

It's never going to be 100%. Because it's very difficult to get 100% of everything out of a rock. So sticking with the lithium example, if we recovered only 4% of the lithium that we mine but throw away, we could replace imports. So we wouldn't have to import lithium from anywhere else.

GILGER: That's a huge deal. OK, why did you look into this, Elizabeth? Like, did you have a hunch? Is it kind of common knowledge in that industry that there's good stuff and all of that waste?

HOLLEY: Well, I would say, personally, I'm a geoscientist, and I love the fact that there is so much in a rock. As a geologist, I want to know what is in the rock. There are a lot of elements on the periodic table.

The amount of any element in any rock is never truly zero. It might be parts per trillion. It might be very, very small. But our rocks are complex. They have a lot of chemical constituents that we need. And we were curious about how much we might currently be mining, but throwing away.

GILGER: Yeah. And were you surprised by the findings, which are, you know, probably more extreme than you might have expected?

HOLLEY: We had a hunch that the numbers would be large. I don't think we knew going into it that they would be this large.

GILGER: Yeah. OK, so let's then talk, Elizabeth, about the policy side of this, right. Like how you shift industry to maybe not throw away all of those critical minerals, even though they might not be what they're exactly mining for. Is there any momentum to make that happen?

HOLLEY: There really is. We've had some very exciting news from the Department of Energy. There's a notice of intent out right now that the federal government is willing to support some infrastructure at operating mines and processing and refining facilities to add that additional equipment to recover byproducts.

So we're starting to think about: What proposals do we want to participate in? Whom might we collaborate with to actually bring some of these elements into byproduct recovery implementation?

GILGER: Can you extract these kinds of critical minerals out of existing waste sites? There's so many of those.

HOLLEY: That is true, and those are calculations that we are finishing up this week and next, and so we intend to publish those as well. I will say those numbers are also very large.

GILGER: What about abandoned mines? We read a lot about that in Arizona. I know there are lots of them across the state that, you know, sort of just sit. Is there any way to look at those as a potential resource?

HOLLEY: Absolutely. And I think it's important to differentiate. Our work right now is focused on accumulated wastes at active mines. ... But there are also a lot of abandoned mines, and those are a taxpayer burden. They might be a safety concern, they might be an environmental concern. And there has been a lot of interest in potentially reprocessing some of that material for critical minerals that we need.

One of the questions is: How much is out there? The USGS and the state geological surveys are starting to work on that, but we don't even have a complete inventory of our mine waste sites and how big they are and what their chemistry might be.

So I think it's going to be really heterogeneous. There are going to be some great opportunities that might be really economic for a company to come in and reap some benefit from doing that. And there are going to be others where maybe reprocessing could help cover the cost of reclamation.

GILGER: Let me ask you, lastly, Elizabeth, about what you hope this might look like in a decade, two decades more. It sounds like we need a shift in the way that we think about mining, because they're finite resources and because, you know, the minerals that we need for the clean energy future are shifting. How do you think this kind of research could impact that future?

HOLLEY: That's such a great question. When I talk to students about the mine of the future, I ask them to envision it as zero waste. So what if we recovered all of the metals and then we had a metal-free end product that could be repurposed for construction or infrastructure? I think that is an excellent, very, very distant goal.

So we see our work as one small step in that direction towards more effective utilization or more efficient utilization of the resources that we mine.