Four hundred parts per million:
that’s the approximate concentration of CO2 in the air today.
What does this even mean?
For every 400 molecules of carbon dioxide,
we have another million molecules of oxygen and nitrogen.
In this room today, there are about 1,800 of us.
Imagine just one of us was wearing a green shirt,
and you’re asked to find that single person.
That’s the challenge we’re facing when capturing CO2
directly out of the air.
Sounds pretty easy,
pulling CO2 out of the air.
It’s actually really difficult.
But I’ll tell you what is easy:
avoiding CO2 emissions to begin with.
But we’re not doing that.
So now what we have to think about is going back;
pulling CO2 back out of the air.
Even though it’s difficult, it’s actually possible to do this.
And I’m going to share with you today where this technology is at
and where it just may be heading in the near future.
Now, the earth naturally removes CO2 from the air
by seawater, soils, plants and even rocks.
And although engineers and scientists are doing the invaluable work
to accelerate these natural processes,
it simply won’t be enough.
The good news is, we have more.
Thanks to human ingenuity, we have the technology today
to remove CO2 out of the air
using a chemically manufactured approach.
I like to think of this as a synthetic forest.
There are two basic approaches to growing or building such a forest.
One is using CO2-grabbing chemicals dissolved in water.
Another is using solid materials with CO2-grabbing chemicals.
No matter which approach you choose, they basically look the same.
So what I’m showing you here is what a system might look like
to do just this.
This is called an air contactor.
You can see it has to be really, really wide
in order to have a high enough surface area
to process all of the air required,
we’re trying to capture just 400 molecules out of a million.
Using the liquid-based approach to do this,
you take this high surface area packing material,
you fill the contactor with the packing material,
you use pumps to distribute liquid across the packing material,
and you can use fans, as you can see in the front,
to bubble the air through the liquid.
The CO2 in the air is separated from the liquid
by reacting with the really strong-binding CO2 molecules in solution.
And in order to capture a lot of CO2,
you have to make this contactor deeper.
But there’s an optimization,
because the deeper you make that contactor,
the more energy you’re spending on bubbling all that air through.
So air contactors for direct air capture have this unique characteristic design,
where they have this huge surface area, but a relatively thin thickness.
And now once you’ve captured the CO2,
you have to be able to recycle that material that you used to capture it,
over and over again.
The scale of carbon capture is so enormous
that the capture process must be sustainable,
and you can’t use a material just once.
And so recycling the material requires an enormous amount of heat,
because think about it: CO2 is so dilute in the air,
that material is binding it really strong,
and so you need a lot of heat in order to recycle the material.
And to recycle the material with that heat,
what happens is that concentrated CO2 that you got from dilute CO2 in the air
is now released,
and you produce high-purity CO2.
And that’s really important,
because high-purity CO2 is easier to liquify,
easier to transport, whether it’s in a pipeline or a truck,
or even easier to use directly,
say, as a fuel or a chemical.
So I want to talk a little bit more about that energy.
The heat required to regenerate or recycle these materials
absolutely dictates the energy and the subsequent cost of doing this.
So I ask a question:
How much energy do you think it takes
to remove a million tons of CO2 from the air
in a given year?
The answer is: a power plant.
It takes a power plant to capture CO2 directly from the air.
Depending on which approach you choose,
the power plant could be on the order of 300 to 500 megawatts.
And you have to be careful about what kind of power plant you choose.
If you choose coal,
you end up emitting more CO2 than you capture.
Now let’s talk about costs.
An energy-intensive version of this technology
could cost you as much as $1,000 a ton
just to capture it.
Let’s translate that.
If you were to take that very expensive CO2 and convert it to a liquid fuel,
that comes out to 50 dollars a gallon.
That’s way too expensive; it’s not feasible.
So how could we bring these costs down?
That’s, in part, the work that I do.
There’s a company today, a commercial-scale company,
that can do this as low as 600 dollars a ton.
There are several other companies that are developing technologies
that can do this even cheaper than that.
I’m going to talk to you a little bit
about a few of these different companies.
One is called Carbon Engineering.
They’re based out of Canada.
They use a liquid-based approach for separation
combined with burning super-abundant, cheap natural gas
to supply the heat required.
They have a clever approach
that allows them to co-capture the CO2 from the air
and the CO2 that they generate from burning the natural gas.
And so by doing this,
they offset excess pollution and they reduce costs.
Switzerland-based Climeworks and US-based Global Thermostat
use a different approach.
They use solid materials for capture.
Climeworks uses heat from the earth,
or even excess steam from other industrial processes
to cut down on pollution and costs.
Global Thermostat takes a different approach.
They focus on the heat required
and the speed in which it moves through the material
so that they’re able to release and produce that CO2
at a really fast rate,
which allows them to have a more compact design
and overall cheaper costs.
And there’s more still.
A synthetic forest has a significant advantage over a real forest: size.
This next image that I’m showing you is a map of the Amazon rainforest.
The Amazon is capable of capturing 1.6 billion tons of CO2 each year.
This is the equivalent of roughly 25 percent
of our annual emissions in the US.
The land area required for a synthetic forest
or a manufactured direct air capture plant
to capture the same
is 500 times smaller.
In addition, for a synthetic forest,
you don’t have to build it on arable land,
so there’s no competition with farmland or food,
and there’s also no reason to have to cut down any real trees
to do this.
I want to step back,
and I want to bring up the concept of negative emissions again.