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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.
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