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  • [♪ INTRO]

  • What do your phone screen, your basement,

  • and the road outside your house have in common?

  • They are all made of sand!

  • Glass, concrete, and asphalt all use sand as one of their main ingredients.

  • Which means sandis in demand.

  • Together with gravel, sand is one of the most used natural resources in the world,

  • second only to water.

  • And that meansthat of course...we're running out.

  • I hate to add to your list of worries, and this seems weird, right?

  • After all, we have kilometers upon kilometers of beaches

  • and also like...deserts. There's deserts!

  • But believe it or not, not all sand grains are created equal.

  • That annoying grit that sticks to your whole body after a day at the beach

  • is different from what makes up desert dunes

  • and only one of them is much use to us.

  • To get sand in the quantities we need,

  • it has to be extracted from the ground

  • coastlines, riverbanks and quarries

  • and this is not only causing shortages, but also major ecological destruction.

  • Luckily, there could be some solutions.

  • Scientists and engineers are developing some alternatives

  • that could help break our reliance on sand.

  • So let's get down to the nitty gritty

  • like, it's actually gritty.

  • What is sand?

  • Sand is defined as having grains

  • between about 0.06 millimeters and two millimeters across.

  • If it's smaller, it's silt.

  • If it's larger, it's gravel.

  • Sand is formed by the weathering of mountains and land masses.

  • Rain, snow, wind, and frost all slowly erode rock,

  • until it's small enough to be carried by water in the form of glaciers, streams,

  • and rivers all the way down to the ocean.

  • That's why natural sand takes thousands or even millions of years to form.

  • And true to form, we are exhausting it faster than it can be naturally replenished.

  • Because the definition of sand is based on size and not material,

  • depending on its location, sand can be made from all kinds of rocks,

  • minerals, and organic matter, like shellsgiving it a lot of variety.

  • But most mundane sand is most commonly made up of

  • silicon dioxide in the form of quartz.

  • It usually also has bits of minerals like feldspar mixed in --

  • materials that are abundant in the Earth's crust and hard to fully break down,

  • so they stick around as sand grains.

  • The light brown color you often see comes from iron oxide -- the same stuff as rust.

  • Different weathering processes also give sand grains different shapes.

  • Sand weathered by wind, like desert sand, is very rounded.

  • Whereas sand worn by water has more jagged edges, because it's a more

  • gentle form of weathering that doesn't wear the particles down as much.

  • And while that sounds like a minor distinction,

  • it makes a huge difference when it comes to how we use it.

  • And boy, do we use it.

  • Humans consume nearly fifty billion metric tons of sand each year.

  • And there's a good reason for it: glass everywhere,

  • from window panes to cell phone screens, is made from melted sand.

  • A combination of sand and gravel, known as aggregate, constitutes

  • eighty percent of concrete -- which is the single most used material in the world.

  • In 2012, we used enough concrete to build a band around the whole equator of

  • the Earth -- twenty-seven meters tall and twenty-seven meters thick!

  • To build a typical home in the United States,

  • you need more than one hundred tons of sand and gravel.

  • The number doubles if you count the street in front of that house,

  • because sand is also the main ingredient in asphalt.

  • In 2012, paved roads accounted for over

  • four million kilometers of road in the US alone.

  • Sand is even used as a base below the construction of buildings and roads.

  • The demand for sand is greatest in Asia,

  • where countries like China are building at a rapid pace.

  • The amount of concrete used worldwide is not tracked, but the amount of cement is.

  • In just three years, from 2011 to 2013,

  • China used more cement than the US did in an entire century.

  • In order to make concrete, you need roughly one part cement

  • to seven parts aggregate or more, depending on the recipe.

  • Meaning China's demand for sand is truly enormous --

  • and the rest of the world needs even more.

  • In some places, sand is also used to expand a nation's geographic footprint.

  • And it's not just for construction projects.

  • We also use sand to restore natural landscapes and ecosystems.

  • Globally, most beaches in protected marine sites are eroding because of

  • climate change and other human impacts.

  • To combat this, engineers in some places will dredge sand up from the ocean

  • and dump it back on beaches.

  • The most populated beaches in the US require sand to be brought in regularly

  • to keep them from eroding away completely.

  • Half of the coastline in the US is eroding,

  • to the point that we've had to fill beaches with over 1.3 billion cubic yards of sand.

  • The cost of all this sand?

  • Over ten billion dollars.

  • And beach sand doesn't stay where you put it.

  • It's consistently being washed out to sea.

  • So beach restoration is always going to be an ongoing process.

  • Here's the real problem, though:

  • whether it's ecosystem restoration or manufacturing,

  • that sand has to come from somewhere.

  • And the type of sand can really matter.

  • Because, yes, as discussed,

  • there are types of sand.

  • The round grains produced by wind weathering, the kind that make up desert sand,

  • aren't really suitable for construction

  • because they don't bond properly when making concrete.

  • The water-worn sediment on coastlines and in riverbeds is rougher

  • and more angular, and the jagged edges connect together like puzzle pieces

  • to create a strong binding, perfect for concrete and asphalt.

  • But because we need so much asphalt and concrete,

  • water-weathered sand is in big demand.

  • In particular, sand mined from riverbeds is the most desirable.

  • That's because sand from beaches or the ocean floor contains contaminants,

  • notably salt -- which has to be washed out before the sand can be used.

  • Our enormous hunger for just the right kind of sand

  • has caused some serious environmental issues.

  • Removing sand from river systems causes their banks to erode

  • and increases the risk of floods.

  • All of this is harmful to aquatic species,

  • and humans who often rely on river-fed aquifers for drinking water.

  • Sand mining can also change the pH balance of water and pollute river basins,

  • further jeopardizing these fragile ecosystems.

  • In many countries, riverbed mining has been largely phased out because it is so destructive,

  • but it's still practiced in some parts of the world.

  • Unregulated river bed sand mining is leading to the destruction of

  • Vietnam's Mekong Delta, an agriculturally important area of Southeast Asia

  • that's home to twenty million people.

  • The delta depends on sediment from upriver to maintain its landscape,

  • particularly as the sea level rises.

  • But sand extraction is removing the sediment before it can make its way to the delta.

  • As countries limit inland sand mining,

  • there's been greater demand on marine and coastal sand.

  • But that's more expensive, thanks to the need for salt removal.

  • Dredging marine sand also kills marine organisms of course.

  • It destroys coral reefs, and affects water circulation.

  • Even when engineers are just restoring beaches,

  • pulling sand up from the ocean floor is harmful to the flora and fauna

  • that depend on that landscape.

  • Marine sand is also crucial for protecting coastlines and islands from severe weather,

  • like the destructive storm surges that accompany tropical storms,

  • destroying coastlines and causing inland flooding.

  • Removing it or mining it makes coastal lands vulnerable to storms and sea level rise.

  • Sand doesn't have to come from water; it can be mined in inland quarries.

  • But they require open pit mines,

  • which are a real not-in-my-backyard kind of problem

  • who wants to live near a giant hole in the ground?

  • Since sand mining is so destructive, some governments have imposed bans.

  • But the need for sand, of course, persists, so it gets shipped from all over the world.

  • Sand shortages have even led to violence and crime in some parts of the world.

  • India and Morocco have sand mafias

  • I'm not making this up

  • that export illegally mined sand,

  • and in Italy, sand supplies are heavily influenced by organized crime.

  • This is real!

  • This stuff is so expensive, it is a mob business.

  • Even when it's legal, sand is pretty heavy, and it often needs to be

  • transported by cargo ships -- giving sand a serious carbon footprint.

  • In Dubai, for example, to build the world's tallest building, the Burj Khalifa,

  • they had to import sand from Australia.

  • And yeah, Dubai is in the middle of the desert!

  • But they couldn't use that sand to make structurally sound concrete.

  • So it had to come all the way from Down Under.

  • Right now, you might be thinking, can't we just make sand?

  • Well, we can, but it is made from rock,

  • which is still a finite resource and still has to be mined from a quarry.

  • Manufactured sand is created by running rock through a crushing machine.

  • And that stuff is actually even rougher than river sand.

  • The angular grains bond together so well that it's actually better for making asphalt.

  • However, studies suggest that manufactured sand

  • requires more water to bind it together compared to water-tumbled sand.

  • It also doesn't look as nice.

  • So even though it can work, construction companies prefer river or coastal sand.

  • Luckily, we have some other options, in addition to manufacturing sand.

  • Some researchers have proposed harvesting sand...

  • from Greenland's retreating glaciers.

  • Now no one wants to melt the glaciers