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, because remember, 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 [by] 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 geothermal, 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. Negative emissions require
that the CO2 separated be permanently removed
from the atmosphere forever, which means putting it back underground, where it came from in the first place. But let's face it, nobody
gets paid to do that today -- at least not enough. So the companies that are developing
these technologies are actually interested in taking the CO2 and making something useful
out of it, a marketable product. It could be liquid fuels, plastics or even synthetic gravel. And don't get me wrong --
these carbon markets are great. But I also don't want you
to be disillusioned. These are not large enough
to solve our climate crisis, and so what we need to do
is we need to actually think about what it could take. One thing I'll absolutely say
is positive about the carbon markets is that they allow for new
capture plants to be built, and with every capture plant built, we learn more. And when we learn more, we have an opportunity
to bring costs down. But we also need to be willing to invest as a global society. We could have all of the clever thinking
and technology in the world, but it's not going to be enough in order for this technology
to have a significant impact on climate. We really need regulation, we need subsidies, taxes on carbon. There are a few of us that would
absolutely be willing to pay more, but what will be required is for carbon-neutral,
carbon-negative paths to be affordable for
the majority of society in order to impact climate. In addition to those kinds of investments, we also need investments
in research and development. So what might that look like? In 1966, the US invested about
a half a percent of gross domestic product in the Apollo program. It got people safely to the moon and back to the earth. Half a percent of GDP today
is about 100 billion dollars. So knowing that direct air capture is one front in our fight
against climate change, imagine that we could invest
20 percent, 20 billion dollars. Further, let's imagine
that we could get the costs down to a 100 dollars a ton. That's going to be hard,
but it's part of what makes my job fun. And so what does that look like, 20 billion dollars,100 dollars a ton? That requires us to build
200 synthetic forests, each capable of capturing
a million tons of CO2 per year. That adds up to about five percent
of US annual emissions. It doesn't sound like much. Turns out, it's actually significant. If you look at the emissions
associated with long-haul trucking and commercial aircraft, they add up to about five percent. Our dependence on liquid fuels
makes these emissions really difficult to avoid. So this investment
could absolutely be significant. Now, what would it take
in terms of land area to do this, 200 plants? It turns out that they would take up
about half the land area of Vancouver. That's if they were fueled by natural gas. But remember the downside
of natural gas -- it also emits CO2. So if you use natural gas
to do direct air capture, you only end up capturing
about a third of what's intended, unless you have that
clever approach of co-capture that Carbon Engineering does. And so if we had an alternative approach and used wind or solar to do this, the land area would be
about 15 times larger, looking at the state of New Jersey now. One of the things that I think about
in my work and my research is optimizing and figuring out
where we should put these plants and think about
the local resources available -- whether it's land, water,
cheap and clean electricity -- because, for instance,
you can use clean electricity to split water to produce hydrogen, which is an excellent, carbon-free
replacement for natural gas, to supply the heat required. But I want us to reflect a little bit
again on negative emissions. Negative emissions should not be
considered a silver bullet, but they may help us
if we continue to stall at cutting down on CO2
pollution worldwide. But that's also why we have to be careful. This approach is so alluring
that it can even be risky, as some may cling onto it as some kind
of total solution to our climate crisis. It may tempt people to continue
to burn fossil fuels 24 hours a day, 365 days a year. I argue that we should not
see negative emissions as a replacement for stopping pollution, but rather, as an addition to an existing
portfolio that includes everything, from increased energy efficiency to low-energy carbon to improved farming -- will all collectively get us on a path
to net-zero emissions one day. A little bit of self-reflection: my husband is an emergency physician. And I find myself amazed
by the lifesaving work that he and his colleagues
do each and every day. Yet when I talk to them
about my work on carbon capture, I find that they're equally amazed, and that's because combatting
climate change by capturing carbon isn't just about saving a polar bear or a glacier. It's about saving human lives. A synthetic forest may not ever be
as pretty as a real one, but it could just enable us
to preserve not only the Amazon, but all of the people that we love and cherish, as well as all of our future generations and modern civilization. Thank you. (Applause)
