The material that could change the world... for a third time

翻译人员: Meiqi Jia 校对人员: Helen Chang

Thousands of years ago, the Romans invented a material

几千年前，罗马人发明了一种 得以让他们建设庞大文明的材料。

that allowed them to build much of their sprawling civilization.

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

老普林尼夸赞一个由这种材料搭建的海堤

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

称之为 “坚不可摧，并且日益坚固”。

He was right: much of this construction still stands,

他说的对，这建筑大半至今犹存，

having survived millennia of battering by environmental forces

从会摧毁现代建筑的数千年的 恶劣环境影响中存活下来了。

that would topple modern buildings.

Today, our roads, sidewalks, bridges, and skyscrapers

今天的道路、人行道、桥和摩天大楼

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

由类似、没有那么耐用的材料所制，

叫做混凝土。

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

世上每个人有 3 吨混凝土。

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

今后的四十年每个月的消耗量 都足够建造一座纽约市。

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

Concrete has shaped our skylines,

混凝土塑造了我们地平线，

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

但不局限于此。

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

混凝土还惊人地大大影响 过去一个世纪的全球升温。

over the last century,

a trend that has already changed the world,

这个趋势已经改变了世界，

and threatens to even more drastically in the coming decades.

并且温度上升将会在未来加剧。

To be fair to concrete, basically everything humanity does

对混凝土公平一点， 其实人类所有的行为

contributes to the greenhouse gas emissions that cause global warming.

都会促成温室气体排放， 造成全球变暖。

Most of those emissions come from industrial processes

绝大多数的排放源来自我们没察觉到

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

却处处影响我们生活的工业活动。

Look around your home.

看看你的家。

Refrigeration— along with other heating and cooling—

冰箱连同其他加热和制冷

makes up about 6% of total emissions.

占了大约 6% 的总排放。

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

生产食物的农业占 18%。

Electricity is responsible for 27%.

电力占 27%。

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

出去走走，驶过的车，头顶上的飞机，

trains ferrying commuters to work—

载着通勤的人们的火车—

transportation, including shipping,

交通工具，包括船舶，

contributes 16% of greenhouse gas emissions.

占温室气体排放的 16%。

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

甚至在我们使用这些东西之前， 制造它们都会造成排放，

a lot of emissions.

很多排放。

Making materials—

制造材料—

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

混凝土、钢铁、塑料、玻璃、铝和其他—

accounts for 31% of greenhouse gas emissions.

占温室气体排放的 31%。

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

单单混凝土便造成了 全世界 8% 的碳排放量。

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

而且，想减少混凝土造成的排放 要比其他的材料更难。

than from other building materials.

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

问题出在水泥身上，混凝土 四种主要组成原料中的其中一种。

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

水泥将其他三种原料— 碎石，沙子和水粘在一起。

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

不幸的是，生产水泥的过程中 是不可能不产生二氧化碳的。

The essential ingredient in cement is calcium oxide, CaO.

CaO 氧化碳是生产水泥的核心成分。

We get that calcium oxide from limestone,

我们从由 CaCO3 碳酸钙组成的 石灰岩中提取氧化碳。

which is mostly made of calcium carbonate: CaCO3.

We extract CaO from CaCO3 by heating limestone.

通过加热石灰岩 从 CaCO3 中提取 CaO。

What’s left is CO2— carbon dioxide.

剩下的便是 CO2—二氧化碳。

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

每生产一吨水泥 便要排放一吨二氧化碳。

As tricky as this problem is,

即便这个问题很棘手，

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

这代表混凝土可以第三次改变世界，

by eliminating greenhouse gas emissions and stabilizing our climate.

做法是：减少温室气体的排放， 并且使我们的天气更稳定。

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

今天，没有 100% 洁净的混凝土，

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

但有些帮助我们达到目的的好想法。

Cement manufacturing also produces greenhouse gas emissions

制造石灰的过程中，

by burning fossil fuels to heat the limestone.

燃烧化石燃料去加热石灰岩， 还造成温室气体的排放。

Heating the limestone with clean electricity or alternative fuels instead

用清洁能源或者其他燃料加热石灰岩

would eliminate those emissions.

会去除这些排放。

For the carbon dioxide from the limestone itself,

至于石灰岩自带的二氧化碳，

our best bet is carbon capture:

最好的赌注便是碳捕获：

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

确切来说，在产生二氧化碳之处， 于其进入大气层之前，将其捕获。

before it enters the atmosphere.

Devices that do this already exist,

现在有可以达到这种目的的装置，

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

但是由于没有经济激励， 它们的应用并不广泛。

Transporting and then storing the captured carbon can be expensive.

运输并且储存被捕获的碳非常昂贵。

To solve these problems,

去解决这些问题，

one company has found a way to store captured CO2 permanently

一个公司找到了可以永久在混凝土里 储存被捕获的二氧化碳的方式，

in the concrete itself.

Other innovators are tinkering with the fundamental chemistry of concrete.

其他创新者们在利用混凝土的基础化学原理。

Some are investigating ways to reduce emissions

有些人研究减少混凝土里面的 水泥成分去减少排放。

by decreasing the cement in concrete.

Still others have been working to uncover and replicate

其他人仍旧在尝试揭露和复制 罗马混凝土的秘密。

the secrets of Roman concrete.

They found that Pliny’s remark is literally true.

他们发现普林尼的赞美是正确的。

The Romans used volcanic ash in their cement.

罗马人在混凝土里加入了火山灰。

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

当火山灰与海水发生反应， 海水使火山灰变得更坚固—

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

比任何今天所使用的混凝土 都更坚固和持久。

By adding these findings to an arsenal of modern innovations,

把这些新的发现加入到 现代的创新者们的宝库里，

hopefully we can replicate their success—

希望我们可以复制他们的成功，

both by making long lasting structures,

不仅建造更加持久的建筑，

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

还确保我们的后代 在几千年后仍能够敬仰它们。