[♪ 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 sand… is in demand. Together with gravel, sand is one of the most
used natural resources in the world, second only to water. And that means… that 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 shells—giving
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 — but due to climate change, Greenland’s ice sheet is already shrinking
at an alarming rate. And glaciers are filled with sand. So as the ice melts, it unearths and dumps a lot of potentially
usable sand into the sea. This is sand that was shaped by water, so it has the potential to be suitable for
construction. In a paper from 2019, scientists suggest that Greenland could become a large exporter
of sand if it collected the sediment from melting
glaciers. Now it’s worth noting that this is purely
speculative at the moment— it is not happening yet. And since Greenland is very far north, the
sand mined from the ice sheet would probably need to be shipped great distances
-- which would be expensive, and have a substantial
carbon footprint. Scientists are also investigating alternatives
to rock and natural sand that could be used in concrete. These concrete alternatives include replacing
sand with iron slag or fly ash, byproducts of the iron and coal industries
that usually go to waste. Other suggestions have included using microplastics and shredded rubber instead of sand. Studies have shown that iron slag in particular makes a suitable replacement for natural sand. However, iron and coal production is dwindling
in the US, meaning their waste is actually in short supply. Recycled building materials are also being
examined as a possible replacement for natural aggregate
in concrete creation. Like crushed concrete, appropriately enough. Germany actually already recycles nearly ninety
percent of the aggregate it uses. And, yes, some have even tried revisiting
that useless desert sand. Though they haven’t met with widespread
success yet. Lastly, one California-based company has proposed
that instead of using sand in concrete… it could be an opportunity to capture carbon. Their process uses carbon dioxide from the
exhaust stack of a power plant to create synthetic limestone -- which then
can act as a substitute for the aggregate in concrete. They’ve already used some of this fancy
concrete at San Francisco International Airport. So there are options now, and hopefully there
will be more in the future. The problem is that the building industry
is very slow to change, and a major hurdle for these technologies
is less science, and more getting stakeholders to buy in. Natural sand, particularly water-worn sand, is a proven and effective ingredient in concrete— builders know it won’t make structures collapse. And when you’re in the building industry, your number one priority is that your building
stays up. The demand will continue to be high until alternatives to natural sand gain more
traction. So the next time you’re at the beach, have a little appreciation for the stuff that’s
sticking to all your parts. Because it’s taken thousands, maybe even
millions, of years to form. And our world would not be the same without
it. Thanks for watching this episode of SciShow, which was brought to you with the help of
our patrons. There isn’t a way we could finance content
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this one go to patreon.com/SciShow, because we do, as always, need your support. [♪ OUTRO]
