How we could make carbon-negative concrete

Concrete is all around us,

but most of us don't even
notice that it's there.

We use concrete to build our roads,

buildings, bridges,
airports; it's everywhere.

The only resource we use
more than concrete is water.

And with population
growth and urbanization,

we're going to need
concrete more than ever.

But there's a problem.

Cement's the glue that
holds concrete together.

And to make cement, you burn limestone

with other ingredients in a
kiln at very high temperatures.

One of the byproducts of that process

is carbon dioxide, or CO2.

For every ton of cement
that's manufactured,

almost a ton of CO2 is
emitted into the atmosphere.

As a result, the cement industry

is the second-largest
industrial emitter of CO2,

responsible for almost 8%
of total global emissions.

If we're going to solve global warming,

innovation in both cement production

and carbon utilization
is absolutely necessary.

Now, to make concrete, you mix cement

with stone, sand, and other ingredients,

throw in a bunch of water,

and then wait for it to harden or cure.

With precast products
like pavers and blocks,

you might shoot steam
into the curing chamber

to try to accelerate the curing process.

For buildings, roads, and bridges,

we pour what's called
ready-mix concrete into a mold

on the job site and wait
for it to cure over time.

Now, for over 50 years,

scientists believed that if
they cured concrete with CO2

instead of water, it
would be more durable,

but they were hamstrung by
Portland Cement's chemistry.

You see, it likes to react
with both water and CO2,

and those conflicting chemistries

just don't make for very good concrete.

So, we came up with a
new cement chemistry.

We use the same equipment
and raw materials,

but we use less limestone

and we fire the kiln
at a lower temperature,

resulting in up to a 30%
reduction in CO2 emissions.

Our cement doesn't react with water.

We cure our concrete with CO2,

and we get that CO2 by capturing waste gas

from industrial facilities

like ammonia plants or ethanol plants

that otherwise would've been
released into the atmosphere.

During curing, the chemical
reaction with our cement

breaks apart the CO2,

capturing the carbon to make limestone,

and that limestone's used to
bind the concrete together.

Now, if a bridge made out of our concrete

were ever demolished,

there is no fear of the CO2 being emitted

because it doesn't exist any longer.

When you combine the emissions reduction

during cement production

with the CO2 consumption
during concrete curing,

we reduce cement's carbon
footprint by up to 70%.

And because we don't consume water,

we also save trillions of liters of water.

Now, convincing a 2,000-year-old industry

that hasn't evolved much
over the last 200 years

is not easy, but there are lots of new

and existing industry players

that are attacking that challenge.

Our strategy is to ease adoption

by seeking solutions that go
beyond just sustainability.

We use the same processes,
raw material, and equipment

that's used to make traditional concrete,

but our new cement makes
concrete cured will CO2

that is stronger, more
durable, lighter in color,

and it cures in 24 hours
instead of 28 days.

Our new technology for ready-mix

is in testing and
infrastructure applications,

and we've pushed our research even further

to develop a concrete that
may become a carbon sink.

That means that we will consume more CO2

than is emitted during cement production.

Since we can't use CO2 gas
at a construction site,

we knew we had to deliver
it to our concrete

in either a solid or liquid form.

So, we've been partnering with companies

that are taking waste CO2

and transforming it into a
useful family of chemicals

like oxalic acid or citric acid,

the same one you use in orange juice.

When that acid reacts with our cement,

we can pack in as much
as four times more carbon

into the concrete, making
it carbon negative.

That means that for a
one-kilometer road section,

we would consume more CO2

than almost a 100,000
trees do during one year.

So, thanks to chemistry and waste CO2,

we're trying to convert
the concrete industry,

the second-most-used
material on the planet,

into a carbon sink for the planet.

Thank you.