Name: The material that could change the world... for a third time
Uploaded: 2021-03-01T18:30:51.000Z
Duration: 5 min 27 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Thousands of years ago, the Romans invented a material

that allowed them to build  much of their sprawling civilization.

Pliny the Elder praised an imposing sea wall made from the stuff

as “impregnable to the waves and every day stronger.”

He was right: much of this construction still stands,

having survived millennia of battering  by environmental forces

Today, our roads, sidewalks, bridges,  and skyscrapers

are made of a similar, though  less durable, material called concrete.

There's three tons of it for every person  on Earth.

And over the next 40 years,  we'll use enough of it

to build the equivalent of New York City  every single month.

but that's not the only way it's changed our world.

It's also played a surprisingly large role in rising global temperatures

a trend that has already  changed the world,

and threatens to even more drastically in the coming decades.

To be fair to concrete, basically everything humanity does

contributes to the greenhouse gas  emissions that cause global warming.

Most of those emissions come  from industrial processes

we often aren't aware of,  but touch every aspect of our lives.

Refrigeration—  along with other heating and cooling—

Agriculture, which produces our food, accounts for 18%.

Walk outside, and the cars zipping past, planes overhead,

contributes 16%  of greenhouse gas emissions.

Even before we use any of these things, making them produces emissions—

concrete, steel, plastic, glass,  aluminum and everything else—

accounts for 31% of greenhouse gas emissions.

Concrete alone is responsible for 8%  of all carbon emissions worldwide.

And it's much more difficult to reduce  the emissions from concrete

The problem is cement,  one of the four ingredients in concrete.

It holds the other three ingredients— gravel, sand, and water— together.

Unfortunately, it's impossible to make cement without generating carbon dioxide.

The essential ingredient in cement is calcium oxide, CaO.

We get that calcium oxide from limestone,

which is mostly made of calcium carbonate: CaCO3.

We extract CaO from CaCO3 by heating limestone.

So for every ton of cement we produce, we release one ton of carbon dioxide.

it means concrete could help us change the world a third time:

by eliminating greenhouse gas emissions and stabilizing our climate.

Right now, there's no 100% clean concrete,

but there are some great ideas to help us get there.

Cement manufacturing also produces greenhouse gas emissions

by burning fossil fuels  to heat the limestone.

Heating the limestone with clean  electricity or alternative fuels instead

For the carbon dioxide from the limestone itself,

specifically, capturing the carbon right where it's produced,

but they aren't widely used because there's no economic incentive.

Transporting and then storing  the captured carbon can be expensive.

one company has found a way to store captured CO2 permanently

Other innovators are tinkering with  the fundamental chemistry of concrete.

Some are investigating ways  to reduce emissions

Still others have been working to uncover and replicate

They found that Pliny's remark  is literally true.

The Romans used volcanic ash  in their cement.

When the ash interacted with seawater, the seawater strengthened it—

making their concrete stronger and more  long-lasting than any we use today.

By adding these findings to an arsenal  of modern innovations,

hopefully we can replicate their success—

and ensuring our descendants can admire them thousands of years from now.