[MUSIC] Humans are land-based creatures,
so it's not surprising that most of the solutions we've
developed to address climate change
are land-based solutions.
One might wonder though,
what will our solutions be with a different worldview?
[MUSIC] Oceans make up
70 percent of the Earth's surface,
and already they absorb more than
a 1/4 of the nearly 40 billion tons of
annual CO_2 emissions through
natural processes that are part of
what's called the global carbon cycle.
The question is, can we enhance any of
these natural processes to pull
down even more carbon dioxide?
The answer is, we probably can,
but we're a long way from understanding
the scale at which we could use the ocean
to sequester more CO_2
and the potential side effects of doing so.
In this video, we're going to
summarize what we do know so far.
Number 1, which ocean carbon dioxide removal
or CDR techniques show the most potential?
Number 2, what are
the risks and costs of employing them?
Number 3, how should we proceed in
testing and developing these technologies?
To start, let's take a look at what
the ocean already does to draw down CO_2.
Seawater and air exists in a physiochemical balance.
The higher the concentration of
CO_2 there is in the atmosphere,
the more CO_2 gets dissolved into
the seawater in the form of carbonic acid,
so as we pump more and more CO_2 into the atmosphere,
we are also adding more CO_2 to the oceans.
Once in the ocean,
the biosphere steps in as Dr. Kim Mayfield,
a Geochemists and Research Scientist at
Lawrence Livermore National Lab, explains.
What's happening is that you have CO_2
from the atmosphere.
It's dissolving into the surface water of the ocean.
Think about how plants do on land, that's a plankton,
our primary producers,
that's what they do in the surface waters.
They're taking this CO_2,
making it into their little bodies,
and then the primary consumers,
think like animals on land,
but in the ocean it's probably a zoo plankton,
it goes and eats it, and all the meanwhile,
while this food web is doing
its thing in the surface waters,
this carbon is sinking down lower
and lower into the deep ocean.
Now some of that carbon is certainly getting recycled.
It's getting pushed back up into the surface waters.
But some of it is sinking all the
way down into the deep ocean and
ends up dissolving into the deep ocean
or getting locked away in the marine sediments.
What we call this is the ocean biological carbon pump.
Ocean CDR strategies aimed to perturb
the biochemical ocean system in order to
increase the drawdown of CO_2 from the atmosphere.
But before we get into
the specifics of how this might be done,
we need to explore what it actually
means to try to engineer a specific outcome,
like increased CO_2 drawdown
from a system as complex as the ocean.
Let's do a thought experiment.
Let's simplify things.
Imagine a beaker of deionized water.
We can add a little table salt
or sodium chloride for fun.
The system we've created is way simpler than the ocean.
It's just air, water, and some salt.
But these three phases are interacting
with each other in many different ways,
driving all of these chemical reactions.
The equilibrium or chemical balance for
each reaction is dependent on
the others and on the conditions of the beaker.
If I were to add more salt or
warm it up or put a lid on it,
or perhaps add more CO_2 to the air,
every one of these chemical reactions would adjust to
these changing conditions and
often in ways that are hard to predict.
The ocean is way more complicated than the beaker.
Whereas our experiment only dealt with a few elements,
in the ocean most elements on
the periodic table are participating in
thousands of biogeochemical reactions
that are interconnected in ways we don't understand.
If there is anything that we have learned
over all of our generations and lifetimes of knowledge,
we know that the ocean is complex.
You're fishing one species,
it affects another,
completely far away, different trophic level.
Ocean food webs are complex.
Ocean chemistry is also complex.
If we're going to be sequestering a lot of carbon,
if we are going to be manipulating
that ocean biological carbon pump,
then we need to be prepared for
even effects that we don't think of right
now or even know could possibly happen.
Keeping that huge caveat in the back of our minds,
let's take a look at how perturbing
the ocean's biogeochemistry to
remove more carbon dioxide might work.
There are two categories of ocean CDR techniques.
Those that try to speed up
the biological pump so that more CO_2
that is dissolved in the surface water
sinks into the deep ocean and sediments.
Those that try to increase the solubility of CO_2,
so that more CO_2
dissolves into the ocean in the first place.
Biological CDR techniques all work by
increasing the growth rate
of the photosynthesizing organisms,
like microscopic phytoplankton or
sea grasses and seaweeds.
A few approaches have been proposed to
increase CO_2 uptake by
increasing the biomass of phytoplankton.
Ocean fertilization involves supplying
a key nutrient into a part of
the ocean where it is naturally
scarce much like fertilizing crops.
The most common growth limiting
nutrients that might be added are iron,
phosphorous, and nitrogen.
Artificial upwelling involves dredging
nutrient rich water up from the deep ocean
into the photic zone where
photosynthesizing organisms
have the sunlight they need to live.
The most studied of these techniques
is artificial iron fertilization,
which has the potential to sequester
as much as 3.7 gigatons of
CO_2 every year at cost between $8-80 per ton CO_2.
But for this or any nutrients seeding method to work,
once you increase the volume of
phytoplankton growing in the photic zone,
they need to sink down into the deep ocean where
their carbon-rich biomass would
remain for thousands of years.
Dr. Wil Burns,
visiting Professor in
the Environmental Policy and Culture Program
at Northwestern University,
explains why this might be
a problem for these types of approaches,
based on existing field studies.
The only way that you would get
sequestration is if this phytoplankton,
has the CO_2 when they drop below
the photic layer or the light layer and
ultimately end up in the deep ocean,
gets consumed that at surface or
remineralizes be before that photic layer,
the CO_2 is going back into the atmosphere.
Virtually none of the studies found
much either phytoplankton production
or sinking below the photic layer.
It can also rob other areas of nutrients,
and so you might have fisheries
downstream that no longer have
the nutrients that they need to thrive and so forth.
Biological techniques focused on
macroscopic organisms like sea grasses
or large seaweeds like kelp,
could potentially solve the problem of
getting the carbon to the deep ocean.
If we sink the seaweed we grow
before it's consumed by animals at the surface.
Seaweed farms come with some added benefits too,
they can absorb the heavy nutrient flow of
urban and agricultural runoff that leads to
algae blooms and fish kills in coastal environments.
They can promote biodiversity,
and they can complement shellfish aquaculture
by locally soaking up
dissolved CO_2 and removing
local ocean acidity. All good, right?
Well, not quite.
First, to sequester just
0.1 gigatons of CO_2, and remember,
we released about 40 gigatons of CO_2 every year,
by growing a seaweed forest
and then sinking into the sea floor,
you'd need a seaweed farm that's
7.3 million hectares in size.
That's the equivalent of 100 meter
wide continuous belt of seaweed running
along 63 percent of
all coastlines of every continent
and island in the world.
The other issue is what
giant seaweed farms could do to natural ecosystems.
Near the surface, they could rob
other organisms of nutrients and light.
In deep ocean, the decomposition of so much seaweed
could alter the chemical balance of sea floor ecosystems,
creating an influx of CO_2 and
nutrients and taking up all of the available oxygen.
Let's say that you want to go,
and raise massive swaths of macroalgae,
think like giant kelp everywhere.
Then you're just going to tie it to some cinder blocks,
and sink it down in the ocean.
Well, something might
live down in the ocean where it is.
There's all of these really neat deep sea communities.
The deep sea does have things living in it,
and we don't know how damaging
their deep sea habitat could
impact the carbon cycle moving forward into the future.
How do you value
environment that you don't see on a day to day basis?
It's complicated.
[MUSIC] It is complicated.
Let's consider the other suite of
ocean CDR approaches which focus
on changing ocean chemistry.
First, there's ocean alkalinity enhancement.
In this scenario, we would dissolve
finely ground rock into
the ocean to increase the oceans alkalinity,
which is like adding a base to increase ocean pH.
To maintain the seawater's chemical equilibrium
more CO_2 will get drawn down from the atmosphere,
dissolving in the sea water to form carbonic acid,
and balancing out the base.
The benefits of this technique are that Number 1,
it could work at scales greater than
one gigaton of CO_2 draw down per year.
Number 2, it will likely keep
the dissolved CO_2 stable in
the ocean for hundreds or thousands of years.
Number 3, it could decrease ocean acidification,
which is important for corals and animals with shells.
A big downside for
ocean alkalinity enhancement is the cost of extracting,
processing, and transporting
the necessary rock or mineral particles.
Cost estimates range from
50-150 US dollars per tonne of CO_2 sequestered,
not including the costs of mitigating
the environmental impacts of a huge amount of mining.
Some of the sequestration benefit would be offset by
emissions from the energy intensive
processes of extracting,
and grinding the rock particles,
but nature might have provided us a work around.
A pilot studies investigating rock flour,
which is the fine silt created when glaciers
scour and abrade the rocks of the Earth's surface.
With its ice sheet quickly melting away,
Greenland is particularly rich in this material.
For example, just one glacial lake
on the edge of the Greenland Ice Sheet holds
about three billion cubic meters of
rock flour enough to capture almost a gigaton of CO_2.
This stuff is already crushed,
and sitting on the coast of
Greenland ready to be transported.
That said, just like seaweed farming,
we need to do a reality check on
the scale of intervention here.
Transporting those three billion cubic meters of
rock flour to tropical waters
where they would dissolve quickly,
would require the largest cargo vessel in the world,
taking about 5,000 trips.
For context, the total number of container ships
operating globally is just over 5,000.
The last option we are going to look
at is electrochemical engineering.
Electrochemistry is a technique that uses
electricity to drive chemical reactions.
In this context, we would pump
seawater into a processing facility where we'd
use an electric current to create
reactions that separate CO_2 from seawater.
The current would locally change pH conditions of
the seawater to more acid or basic solutions,
decreasing how much CO_2
can remain dissolved in the water.
The CO_2 can be degassed,
and then we'd sequester it on land as
we do with other carbon capture techniques.
The remaining fluid, which now has a higher pH because we
pulled out the carbonic acid
could be discharged back into the ocean,
and essentially acts like an ocean alkalinity enhancer,
causing further draw down of CO_2.
The downsides to this technique are that is expensive,
costing hundreds to thousands of
dollars per ton sequestered,
and it's very energy intensive,
so it doesn't make sense to do this until we
have a completely decarbonized energy sector.
While the techniques we have discussed
all have the potential to
remove significant amounts of
carbon dioxide from the atmosphere.
We are far from understanding what
the downstream effects of these interventions might be.
Unfortunately, the only way to really find out is to
carefully scale up the research
in natural marine settings.
We have put ourselves,
we, my generation,
my parents generation and so forth,
have put ourselves in
a position where we have to contemplate
these risky technologies because of
the dire applications of not considering them.
But we have to acknowledge
the fact that there are risks,
and that some of those risks carry
huge uncertainties that we won't know
the answer to until we scale up.
Scale up will have to in a lot of
cases if we're going to determine it.
I don't want the private companies alone involved in it.
I want the international treaty regimes
that have already, to some degree,
talked about this and talked about the need
for risk assessment protocols,
and only doing it for scientific purposes,
and not just allow
private companies to be cowboys in the oceans.
Those international treaty regimes are
the United Nations Convention on Law of the Seas,
and the London Convention and London Protocol.
The first of these requires that
scientific interventions taking place in the ocean must
not ''Unjustifiably interfere with
other legitimate uses of the oceans.''
The second regulates ''Marine
pollution by dumping of wastes,
and other matter,'' which can include
material that would be used in artificial fertilization,
alkalinity enhancement, and in
some cases, seaweed cultivation.
Entrepreneurs cannot simply go out into the ocean,
try one of these methods,
and see what happens.
We have to develop careful experiments
with detailed monitoring protocols,
and approval from all relevant jurisdictions,
and in collaboration with any potential stakeholders.
But it's also important to just think about
all the different communities
that live near these coastal areas,
that live near the ocean,
and how to best involve them
in the different projects
that are going to be taking place.
I think that some of the best science,
and most exciting works can
go unnoticed if they're not communicated.
I think that's something
that I would personally love to see moving
forward is for all these different exciting ocean based
carbon dioxide removal ventures to really
include the communities in
the areas that they're working around.
Ocean carbon dioxide removal technologies
are not ready to deploy tomorrow.
As we build our knowledge about whether
these could be safe and effective solutions,
our priority must continue to be fast paced,
decarbonization, and efficiency improvement.
We should keep exploring other ways the ocean could
contribute to decreasing atmospheric CO_2.
The sea floor is the ideal composition
for CDR through mineralization,
which we discussed in its own dedicated video
in our CDR series.
We explore the CDR potential
of restoring marine ecosystems
in our video on nature
based solutions for carbon dioxide removal.
You can find these videos and more at climatenow.com.
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Thanks and see you next time.
[MUSIC]