Can seaweed help curb global warming?

It's time for planetary-scale interventions to combat climate change -- and environmentalist Tim Flannery thinks seaweed can help. In a bold talk, he shares the epic carbon-capturing potential of seaweed, explaining how oceangoing seaweed farms created on a massive scale could trap all the carbon we emit into the atmosphere. Learn more about this potentially planet-saving solution -- and the work that's still needed to get there.

Oh, there's a lot of it.

This is seaweed.

It's pretty humble stuff.

But it does have
some remarkable qualities.

For one, it grows really fast.

So the carbon that is part
of that seaweed,

just a few weeks ago,

was floating in the atmosphere
as atmospheric CO2,

driving all the adverse consequences
of climate change.

For the moment, it's locked
safely away in the seaweed,

but when that seaweed rots --

and by the smell of it,
it's not far away --

when it rots, that CO2 will be released
back to the atmosphere.

Wouldn't it be fantastic
if we could find a way

of keeping that CO2 locked up long-term,

and thereby significantly contributing
to solving the climate problem?

What I'm talking about here is drawdown.

It's now become the other half
of the climate challenge.

And that's because
we have delayed so long,

in terms of addressing climate change,

that we now have to do two very big
and very difficult things at once.

We have to cut our emissions
and clean our energy supply

at the same time that we draw
significant volumes

of carbon dioxide out of the atmosphere.

If we don't do that, about 25 percent
of the CO2 we put in the air

will remain there,
by human standards, forever.

So we have to act.

This is really a new phase
in addressing the climate crisis

and it demands new thinking.

So, ideas like carbon offsets
really don't make sense

in the modern era.

You know, when you offset something,

you say, "I'll permit myself to put
some greenhouse gas into the atmosphere,

but then I'll offset it
by drawing it down."

When you've got to both cut your emissions

and draw down CO2,

that thinking doesn't make sense anymore.

And when we're talking about drawdown,

we're talking about putting large volumes
of greenhouses gases, particularly CO2,

out of circulation.

And to do that, we need a carbon price.

We need a significant price
that we'll pay for that service

that we'll all benefit from.

We've made almost no progress so far

with the second half
of the climate challenge.

It's not on most people's radar.

And, you know, I must say,
at times, I hear people saying,

"I've lost hope that we can do anything
about the climate crisis."

And look, I've had my sleepless
nights too, I can tell you.

But I'm here today as an ambassador
for this humble weed, seaweed.

I think it has the potential

to be a big part of addressing
the challenge of climate change

and a big part of our future.

Now, what the scientists are telling us
we need to do over the next 80-odd years

to the end of this century,

is to cut our greenhouse gas emissions

by three percent every year,

and draw three gigatons of CO2
out of the atmosphere every year.

Those numbers are so large
that they baffle us.

But that's what the scientists
tell us we need to do.

I really hate showing this graph,

but I'm sorry, I have to do it.

It is very eloquent
in terms of telling the story

of my personal failure

in terms of all the advocacy I've done
in climate change work

and in fact, our collective failure
to address climate change.

You can see our trajectory there

in terms of warming
and greenhouse gas concentrations.

You can see all of the great
scientific announcements that we've made,

saying how much danger
we face with climate change.

You can see the political meetings.

None of it has changed the trajectory.

And this is why we need new thinking,

we need a new approach.

So how might we go about drawing down
greenhouse gases at a large scale?

There's really only two ways of doing it,

and I've done a very deep dive
into drawdown.

And I'll preempt my --

And I would say this stuff comes up
smelling like roses at the end of the day.

It does, it's one of the best options,

but there are many, many possibilities.

There are chemical pathways
and biological pathways.

So two ways, really,
of getting the job done.

The biological pathways are fantastic

because the energy source
that's needed to drive them, the sun,

is effectively free.

We use the sun to drive
photosynthesis in plants,

break apart that CO2
and capture the carbon.

There are also chemical pathways.

They sound ominous, but actually,
they're not bad at all.

The difficulty they face is
that we have to actually pay

for the energy
that's required to do the job

or pay to facilitate that energy.

Direct air capture is a great example
of a chemical pathway,

and people are using that right now
to take CO2 out of the atmosphere

and manufacture biofuels
or manufacture plastics.

Great progress is being made,

but it will be many decades

before those chemical pathways
are drawing down a gigaton of CO2 a year.

The biological pathways offer us
a lot more hope, I think,

in the short term.

You've probably heard
about reforestation, planting trees,

as a solution to the climate problem.

You know, it's a fair question:

Can we plant our way out
of this problem by using trees?

I'm skeptical about that
for a number of reasons.

One is just the scale of the problem.

All trees start as seeds,
little tiny things,

and it's many decades
before they've reached

their full carbon-capture potential.

And secondly,

if you look at the land surface,
you see that it's so heavily utilized.

We get our food from it,
we get our forestry products from it,

biodiversity protection
and water and everything else.

To expect that we'll find enough space
to deal with this problem,

I think is going to be quite problematic.

But if we look offshore,

wee see a solution where there's already
an existing industry,

and where there's a clearer way forward.

The oceans cover
about 70 percent of our planet.

They play a really big role
in regulating our climate,

and if we can enhance
the growth of seaweed in them,

we can use them, I think,
to develop a climate-altering crop.

There are so many
different kinds of seaweed,

there's unbelievable
genetic diversity in seaweed,

and they're very ancient;

they were some of the first
multicellular organisms ever to evolve.

People are using special
kinds of seaweed now

for particular purposes,

like developing very high-quality
pharmaceutical products.

But you can also use seaweed
to take a seaweed bath,

it's supposed to be good for your skin;

I can't testify to that,
but you can do it.

The scalability is the big thing
about seaweed farming.

You know, if we could cover
nine percent of the world's ocean

in seaweed farms,

we could draw down the equivalent
of all of the greenhouse gases

we put up in any one year,

more than 50 gigatons.

Now, I thought that was fantastic
when I first read it,

but I thought I'd better calculate how big
nine percent of the world's oceans is.

It turns out, it's about
four and a half Australias,

the place I live in.

And how close are we
to that at the moment?

How many ocean-going seaweed farms
do we actually have out there?

Zero.

But we do have some prototypes,
and therein lies some hope.

This little drawing here of a seaweed farm
that's currently under construction

tells you some very interesting
things about seaweed.

You can see the seaweed
growing on that rack,

25 meters down in the ocean there.

It's really different
from anything you see on land.

And the reason being that, you know,
seaweed is not like trees,

it doesn't have nonproductive parts

like roots and trunks
and branches and bark.

The whole of the plant
is pretty much photosynthetic,

so it grows fast.

Seaweed can grow a meter a day.

And how do we sequester the carbon?

Again, it's very different from on land.

All you need to do
is cut that seaweed off --

drifts into the ocean abyss,

Once it's down a kilometer,

the carbon in that seaweed is effectively
out of the atmospheric system

for centuries or millennia.

Whereas if you plant a forest,

you've got to worry
about forest fires, bugs, etc.,

releasing that carbon.

The key to this farm, though,

is that little pipe
going down into the depths.

You know, the mid-ocean is basically
a vast biological desert.

There's no nutrients there
that were used up long ago.

But just 500 meters down,

there is cool, very nutrient-rich water.

And with just a little bit
of clean, renewable energy,

you can pump that water up

and use the nutrients in it
to irrigate your seaweed crop.

So I think this really has
so many benefits.

It's changing a biological desert,

the mid-ocean,

into a productive, maybe even
planet-saving solution.

So what could go wrong?

Well, anything we're talking
about at this scale

involves a planetary-scale intervention.

And we have to be very careful.

I think that piles of stinking seaweed

are probably going to be
the least of our problems.

There's other unforeseen things
that will happen.

One of the things that really worries me,
when I talk about this,

is the fate of biodiversity
in the deep ocean.

If we are putting gigatons of seaweed
into the deep ocean,

we're affecting life down there.

The good news is that we know

that a lot of seaweed
already reaches the deep ocean,

after storms or through submarine canyons.

So we're not talking
about a novel process here;

we are talking about
enhancing a natural process.

And we'll learn as we go.

I mean, it may be that these ocean-going
seaweed farms will need to be mobile,

to distribute the seaweed
across vast areas of the ocean,

rather than creating
a big stinking pile in one place.

It may be that we'll need
to char the seaweed --

so create a sort of an inert,
mineral biochar

before we dispatch it into the deep.

We won't know until we start the process,

and we will learn effectively by doing.

I just want to take you
to contemporary seaweed farming.

It's a big business --

it's a six-billion-dollar-a-year business.

These seaweed farms off South Korea --

you can see them from space,
they are huge.

And they're increasingly
not just seaweed farms.

What people are doing in places like this
is something called ocean permaculture.

And in ocean permaculture,

you grow fish, shellfish
and seaweed all together.

And the reason it works so well

is that the seaweed
makes the seawater less acid.

It provides an ideal environment
for growing marine protein.

If we covered nine percent
of the world's oceans

in ocean permaculture,

we would be producing enough protein
in the form of fish and shellfish

to give every person
in a population of 10 billion

200 kilograms of high-quality
protein per year.

So, we've got a multipotent solution here.

We can address climate change,
we can feed the world,

we can deacidify the oceans.

The economics of all of this
is going to be challenging.

We'll be investing many,
many billions of dollars

into these solutions,

and they will take decades
to get to the gigaton scale.

The reason that I'm convinced
that this is going to happen

is that unless we get the gas
out of the air,

it is going to keep driving
adverse consequences.

It will flood our cities,

it will deprive us of food,

it will cause all sorts of civil unrest.

So anyone who's got a solution
to dealing with this problem

has a valuable asset.

And already, as I've explained,

ocean permaculture is well on the road
to being economically sustainable.

You know, in the next 30 years,

we have to go from being
a carbon-emitting economy

to a carbon-absorbing economy.

And that doesn't seem like very long.

But half of the greenhouse gases
that we've put into the atmosphere,

we've put there in the last 30 years.

My argument is,

if we can put the gas in in 30 years,

we can pull it out in 30 years.

And if you doubt how much
can be done over 30 years,

just cast your mind back
a century, to 1919,

compare it with 1950.

Now, in 1919, here in Edinburgh,

you might have seen
a canvas and wood biplane.

Thirty years later,
you'd be seeing jet aircraft.

Transport in the street
were horses in 1919.

By 1950, they're motor vehicles.

1919, we had gun powder;

1950, we had nuclear power.

We can do a lot in a short period of time.

But it all depends upon us believing
that we can find a solution.

Now what I would love to do
is bring together all of the people

with knowledge in this space.

The engineers who know
how to build structures offshore,

the seaweed farmers, the financiers,

the government regulators,

the people who understand
how things are done.

And chart a way forward,

say: How do we go from the existing
six-billion-dollar-a-year,

inshore seaweed industry,

to this new form of industry,
which has got so much potential,

but will require large
amounts of investment?

I'm not a betting man, you know.

But if I were,

I'll tell you, my money
would be on that stuff,

it would be on seaweed.

It's my hero.

Thank you.

(Applause)