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  • [♪ INTRO]

  • Whether it's your phone, laptop, or TV,

  • you're watching this video on a miracle of technology.

  • As much as it might seem like it, these devices aren't made from literal magic,

  • but materials with unique and surprising properties.

  • But as special as they are, it shouldn't surprise you to learn that they're also hard to find enough of.

  • Today, we're consuming them faster than ever

  • and researchers are starting to worry that we may be running out.

  • This idea that we may exhaust our supply of certain important elements is called criticality,

  • and it's already starting to shape what the technology of the future might look like.

  • We're going to look at a bunch of reasons why certain elements might become scarce,

  • but the obvious one is that there just wasn't a lot to begin with.

  • A great example of this is indium, which sits two rows below aluminum on the periodic table.

  • Yet aluminum is more than a million times more abundant in Earth's crust.

  • As much as 75% of the world's indium production is used to make indium tin oxide,

  • which has the remarkable property of conducting electricity while remaining completely transparent.

  • It's a key component in LCDs and touch screens,

  • so you're probably looking at, or through, some indium right now!

  • It's also used in solar panels and for the ball bearings in Formula 1 race cars.

  • The world is planning on building a lot of solar panels and LCDs in the coming years,

  • so we're going to need a big supply of indium, which is kind of a problem.

  • In fact, some estimates suggest our demand for the element may begin to exceed production by 2030.

  • Unfortunately, increasing that production is easier said than done.

  • Indium is mined mainly as a byproduct of zinc extraction, but even then it's rare,

  • with abundances anywhere from 1 to 100 parts per million in zinc ore.

  • So a big increase in indium production means a glut of zinc,

  • whether we need more of that metal or not.

  • Instead of producing more indium, another option is to simply use less of it.

  • Since we're not likely to give up on televisions and solar panels, that means finding an alternative.

  • For screens, that could mean antimony,

  • but the criticality of that element is even higher than that of indium.

  • So not a great substitute.

  • Manufacturers of solar panels could replace indium with graphene or carbon nanotubes,

  • but these advanced materials are still experimental and very expensive.

  • It's not only very scarce elements that face a supply risk, either.

  • Some materials have high abundance, but low concentration.

  • The poster children for this problem are the dubiously-named rare-earth elements,

  • which consist mainly of the elements in the lanthanide series.

  • Scientists initially discovered them as trace components of minerals that themselves were very rare.

  • This gave rise to the notion that they were among the Earth's scarcest elements.

  • Today, we know that that's not actually true.

  • Cerium, for example, is as abundant as copper,

  • and even the rarest of the rare-earths is 200 times more common than gold!

  • What makes themrareis that, unlike many other metals,

  • they didn't end up in concentrated deposits in the Earth's crust that are easy to find and mine.

  • The rare-earths have the highest criticality of any element

  • not just because they're extremely difficult to extract,

  • but because they're also used in an incredible array of products.

  • Cerium is the only element other than iron that produces sparks when struck.

  • If you've ever used a “flintto start a fire or a lighter instead of a match,

  • you've probably used an alloy of the two called ferrocerium.

  • Ferrocerium is valuable because it sparks at a uniquely low temperature,

  • making things like lighters easier to use.

  • The unusual properties of rare-earths mean they pop up in all sorts of modern technology.

  • Up to 50% of the glass in your smartphone camera, for instance, is made of lanthanum.

  • Neodymium magnets are used in spinning hard drives and DVD players,

  • while yttrium, europium, and terbium create the colors in your TV screen and LED lights.

  • A big part of why technology today is so different from a century ago

  • is that we've learned to effectively extract and use these exotic materials.

  • Rarity isn't the only reason an element can have high criticality.

  • A material can be relatively abundant, yet difficult to mine safely and ethically.

  • As governments around the world

  • become more concerned with the environmental and human impact of mining,

  • they may create regulations that further diminish the supply of a critical element.

  • These broader limitations can mean that even if a particular substance is safe,

  • it faces restrictions based on the byproducts of its extraction.

  • A good example is monazite, a mineral rich in rare-earth elements.

  • After processing, monazite can contain up to 70% cerium and lanthanum,

  • enabling the creation of all the products we just talked about.

  • But monazite also contains thorium, uranium, and radium, which are highly-regulated radioactive elements.

  • The cost and difficulty of dealing with these toxic byproducts

  • led to the closure of America's only rare-earth element processing facility in the early 2000s.

  • Another example is arsenic, which is a byproduct of copper and gold mining.

  • In the form of gallium arsenide, it's a key component in the manufacturing of semiconductors,

  • which are the foundation for basically all modern technology.

  • Arsenic is also used in the process of pressure-treating wood,

  • like what you might build a deck or mailbox post out of.

  • It's also poisonous, and can cause cancer,

  • which means it hasn't been mined in the United States since 1985.

  • That's the tension in this class of criticality:

  • some of our most important technology relies on some pretty nasty stuff.

  • Right now, there are people and places willing to do that dirty work,

  • but there's no guarantee that this will always be true.

  • The last big cause of criticality is what researchers call vulnerability to supply restriction.

  • It's the idea that there are people and politics behind everything we do,

  • and that those factors are inherently unpredictable.

  • For many elements, it's not just that they're incredibly rare or dangerous to produce,

  • but that production happens in very few places.

  • Which, if you think about it, is a natural consequence of our two previous factors.

  • If a resource is very rare, there are probably only a couple places in the world where it can be easily found.

  • And as more countries regulate the mining industry,

  • there are fewer and fewer places willing to do the extraction.

  • If something happens to restrict production in those few places, whether it's deliberate or not,

  • the global supply of a critical element could be threatened.

  • The world first started to understand this about fifty years ago

  • when what's today the Democratic Republic of the Congo underwent a period of severe civil unrest.

  • Back then, the DRC was the world's chief supplier of cobalt,

  • and the nation's unrest led to a sharp drop in exports.

  • Today, the country still supplies about two-thirds of the world's cobalt.

  • It's used in a bunch of things, but the most important by far is in the construction of lithium-ion batteries.

  • That's the battery technology that powers our phones and laptops,

  • but it's also used in many modern electric cars.

  • If electric cars are going to be a big tool in the fight against climate change,

  • that means the effort will hinge in part on the stability of the DRC.

  • And cobalt isn't the only example. Geology and chemistry don't care about national borders.

  • But because of how mineral deposits are often concentrated,

  • one nation can end up controlling the lion's share of a particular element.

  • The US, for instance, produces 73% of the world's helium,

  • which is critical for the use of MRI machines.

  • China provides 95% of the gallium used in LED lights,

  • as well as around 70% of arsenic, antimony, and all the rare-earth elements.

  • In fact, of the 35 most critical elements in the world, China is the leading producer of at least 20.

  • This is where geopolitics, technology, and geology can overlap, sometimes uncomfortably.

  • Whether it's China, the US, or somebody else controlling most of one element,

  • that's a lot of influence concentrated in one place.

  • That's why some researchers believe the key to overcoming this form of criticality

  • is to focus on finding more ways to make the same stuff.

  • Another way might seem even more obvious: we could just reuse the material we already have.

  • Recycling important elements from discarded products

  • would help resolve all three factors that produce criticality.

  • Reusing material would slow the extraction of a finite resource and reduce the need for further mining,

  • which could have a big environmental impact.

  • One study found that recovering metals at a recycling plant produced 80% fewer emissions

  • than mining an equivalent quantity, which is a win for stopping climate change.

  • And unlike extraction, which can only happen where ore deposits are located,

  • stuff can be recycled anywhere.

  • That could reduce the market power of dominant producers.

  • The challenge is that recycling individual elements is a lot harder than, say,

  • recovering the plastic from a milk jug.

  • These materials often exist in only trace amounts as part of a highly processed product

  • like a circuit board.

  • Worldwide, less than 1% of rare-earth elements are recovered

  • and, in 2018, no arsenic was recycled anywhere in the world.

  • Instead, it ends up adding toxicity to your local landfill.

  • Reversing this trend will require techniques as innovative as the materials themselves.

  • One idea is phytomining, which uses specially-selected plants to extract trace elements from recycled products.

  • The plants concentrate the metal in their own structure,

  • which can then be destroyed to retrieve the substance.

  • Another option is bioleaching, which uses engineered bacteria to dissolve

  • and extract metals like copper and cobalt.

  • It's already used to produce more than 20% of the world's mined copper,

  • and researchers are investigating how to effectively use bioleaching in recycling programs.

  • Ultimately, we don't really have much of a choice when it comes to dealing with criticality.

  • Our modern forms of transportation, power generation, and medicine

  • have come to rely on these nearly-magical materials.

  • To keep their benefits, we'll need to learn to deal with their scarcity.

  • But it's not all bad news.

  • Criticality isn't a single, static problem; it's a function of our ability to engineer and discover.

  • As we find new ways to solve problems and more accessible, sustainable materials to use,

  • we can sidestep some of these challenges.

  • Others will require learning to live within the constraints of what's here on Earth,

  • but that research is already underway.

  • Still, the next time you buy a slick new phone,

  • make sure you don't simply throw the old one away.

  • The elements inside could literally be priceless.

  • Thanks for watching this episode of SciShow,

  • which was brought to you with the help of our patrons.

  • Patrons earn cool perks, plus they help us make awesome videos for everyone to enjoy.

  • If you'd like to join up, check out patreon.com/scishow.

  • [♪ OUTRO]

[♪ INTRO]

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B1 中級

我們的這些元素已經用完了--這裡有辦法 (We're Running Out of These Elements — Here's How)

  • 7 1
    林宜悉 發佈於 2021 年 01 月 14 日
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