How we could make carbonnegative concrete Tom Schuler
Transcriber: TED Translators Admin
Reviewer: Rhonda Jacobs
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 eight percent
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 percent
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’s 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 percent.
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 with 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.