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  • 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.