Sponges are great aren't they? Super absorbent materials that you can just
dab onto whatever it is you clumsily spill this time, safe in the knowledge it'll soak it all up
and keep you out of trouble. And that's kind of how we've been unwittingly treating our oceans
for the last couple of hundred years. Except it's not excess liquid that they've been mopping up,
it's excess carbon dioxide from the atmosphere. In fact it's reckoned that our oceans have absorbed
at least 30 percent of all the CO2 we humans have spewed out since the start of the industrial
revolution, and by the way more than 90 percent of the excess heat too. If they hadn't have done
that then our average surface temperature will be more than double what it is now and I wouldn't
be sitting here talking to you, because I'd be dead! But sponges have their limits don't they?
If you completely drench them they start to leak because they just don't have any more space to
absorb any more stuff. And in a similar way, as we humans rapidly change the ocean's carbon balance,
we're reaching the limits of how much CO2 can be absorbed before the oceans start breathing some
of it back out again in a process the scientists refer to as degassing. Now, when a sponge starts
dripping water all over your floor you can be fairly sure it's saturated and at that point,
if you had any sense, you'd find somewhere to ring it out so it could regain its absorbency.
And that's quite a good analogy for the proposal in a recent paper from a research team at UCLA
which outlines a method for capturing carbon dioxide from our oceans at the kind of gigaton
scale that could genuinely make a meaningful impact on our climate mitigation challenge.
So is this yet another exercise in wishful thinking or have we
got ourselves a potential winner?.. "are you gonna clean that up"? Yes!
Hello and welcome to just have a think. This whole ocean CO2 concentration thing
doesn't really get quite as much attention as it probably deserves. The fact is we're extremely
fortunate that about 70 percent of the planet is covered in water and that water by volume just
happens to have the ability to hold on to about 150 times more carbon dioxide than the air. And
that rather serendipitous physical phenomenon has at least so far saved us humans and all the other
species we share the land with from far more severe climate change impacts than the ones
we're already witnessing around the world today. But there's a price to pay for all that surplus
carbon dioxide in the upper layers of our oceans. It upsets delicately balanced ecosystems resulting
in damaging consequences like marine heat waves, species migration and ocean acidification.
Reducing the levels of CO2 in our oceans would therefore, at least on the face of it,
seem like a good way to slow down or even reverse those consequences and restore the
marine balance. But the atmosphere and the oceans are in a state of equilibrium, so if we did find a
way to reduce the levels of CO2 in our oceans then to maintain the equilibrium the oceans would react
by absorbing more CO2 back out of the atmosphere. Now it just so happens that removing carbon
dioxide from our atmosphere is precisely what the Intergovernmental Panel on Climate Change
or IPCC tell us will be essential in the coming decades if we're to stand any chance
of keeping planetary warming within safe limits. So the challenge is to find an ocean carbon
dioxide removal method that doesn't cause even more shocks and disruptions to marine ecosystems
while removing CO2 at a scale of billions of tons per year and storing it durably so it can't seep
back into the system. That's a pretty seriously complicated conundrum! But in this research paper,
published in 2021, the UCLA team outlined a method that they reckon might just do the job.
Interviewed in an article for the UCLA newsroom the paper's senior author, Gaurav Sant explains
"to mitigate climate change we need to remove carbon dioxide from the atmosphere at a level of
between 10 billion and 20 billion metric tons per year. To fulfil a solution of that scale we've got
to draw inspiration from nature". The system that Sant and his co-authors are proposing is called
Single Step Carbon Sequestration and Storage, or sCS2, and in basic terms it works like this.
Seawater is drawn up into a flow reactor and through an electrically conductive stainless
steel mesh which acts like a cathode in a battery and causes electrolysis of the water.
That increases the concentration of hydroxide ions which facilitates chemical reactions between the
carbon dioxide and calcium and magnesium that are naturally present in seawater to produce solid
limestone and magnesite in a process very similar to the way seashells are formed, only at a vastly
accelerated rate. The sea water that flows out of the other end now has far less carbon dioxide
dissolved in it and it can be returned back to the ocean. The solid limestone and magnesite
mass that builds up on the mesh itself can then be removed using a rotary drum and it too can be
returned back into the ocean, where it'll take its chemically captured carbon dioxide to the seabed
in a solid state that would effectively remain permanently stable. Now, any chemistry teacher
watching this might be gently pointing out that electrolysis of salt water produces chlorine gas
at the anode which is nasty. And at the scale these guys are talking about it'll be extremely
dangerous if it got into the local atmosphere, so the UCLA system would need to incorporate
special coatings in the anode or a commercial adsorption technology like activated carbon to
soak up the chlorine and stop it getting airborne. But water electrolysis also produces hydrogen gas,
which could be an extremely valuable by-product if it was integrated into the right infrastructure.
And the system could also be a perfect complement to existing desalination facilities,
providing pre-softened water for the processing plant, reducing the overall cost and energy demand
of the desalination process by something like nine percent according to the UCLA research team.
The team also calculated that their sCS squared carbon removal technology
would use far less energy than existing direct air capture technologies currently in development.
That energy would ideally come from renewable sources like wind and solar.
In fact it could prove to be a useful way to utilize excess power generation from those
intermittent sources which would otherwise be wasted through the process of curtailment,
where renewable power generators have to be periodically shut down to prevent grid overloads.
The single step in the name differentiates the UCLA proposal from atmospheric carbon
dioxide capture technologies which invariably require the captured CO2 to undergo multiple
concentration processes before it can be stored. And those atmospheric carbon capture systems
generally involve storing the CO2 in geological formations like depleted oil and gas reservoirs
where there's a risk of the gas leaking back out and escaping up into the atmosphere. By contrast,
the sCS squared concept would durably store carbon dioxide in the form of solid minerals.
As Gaurav Sant points out "what's nice about turning carbon dioxide into a rock
is it isn't going anywhere". The science bods have calculated that the amount of carbon
currently stored on our ocean seabeds in the form of these solid carbonates and bicarbonates
is about 50 times more than all the carbon in our atmosphere. So we know that even relatively minor
increases to that ocean carbon storage vault could produce huge reductions in atmospheric
CO2 concentrations. The scale and cost of the infrastructure required are a bit eye
watering though. The team carried out detailed analyses of the material and energy inputs
as well as the cost involved in running the system and dealing with the various by-products.
By their calculations, to remove 10 billion metric tonnes of carbon dioxide from the ocean per year
the world would need to construct about 1800 of these facilities in strategic coastal and
river delta locations around the world and the upfront capital expenditure would run to
trillions of dollars. But climate mitigation at the scale now required is going to cost money,
whichever methodology we choose to employ. What's required is the political will to find that money.
It can be done though. After all, our world leaders managed to find several trillion dollars
almost overnight when the clear and present danger of COVID19 presented itself, didn't they?
And all the major global financial institutions like the IMF, the World Bank, and even hard-nosed
asset managers like Blackrock agree that if we don't take rapid and radical action now
then the financial consequences of future extreme climate events
will completely eclipse the costs of implementing mitigation measures today. "We should be clear",
says Gaurav Sant, "managing and mitigating carbon dioxide is foremost an economic challenge. We've
tried to use a lens of pragmatism to consider how we may be able to achieve synthetic interventions
at an unprecedented scale while considering the finite energy and financial resources we have".
What we've got here though, is essentially a form of geo-engineering.
And while the UCLA team do go to some length in their paper to assess and quantify the potential
knock-on effects of tinkering with nature's ecosystems at this kind of scale
there is still a risk that initiatives like this may do more harm than good in the long term.
And there's another school of thought that says we can achieve similar levels of decarbonisation
in a biological rather than geological way by cultivating the growth of photosynthesizers like
kelp, seagrass meadows, and mangroves, all of which can suck up far more CO2 by volume than
our land-based rainforests. It's something we looked at on this channel a couple of years ago,
and I'll leave a link to that video up there somewhere. But even here, the long-term effects
of our interference on delicately balanced ocean ecosystems are not yet fully understood.
It was a subject of some considerable debate at the recent World Ocean Summit Week.
Here's Brad Ack, the Chief Innovation Officer of a decarbonisation startup called Ocean Vision,
discussing the challenge during the event... "we don't know enough yet to know which ones
are going to be the most successful, the least harmful, the most positive.
So we need a great deal more research and development and testing in water,
in multiple replicants, all around the globe, to be able to answer the question that you asked".
And of course another major caveat with any carbon dioxide removal or CDR scheme is that it'll only
work if it runs alongside very large, very rapid, and very genuine reductions in energy consumption
and greenhouse gas emissions in industry, commerce, food and transport systems across
the globe. If governments and corporations look at CDR as an excuse to carry on business as usual
then whatever system we choose will turn out to be an extremely expensive waste of time and money!
As usual, leave your thoughts in the comments section below, but that's it for this week.
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