Catching Carbon - Is the Sea Safe for Sequestration?

Could the ocean provide a good 'sink' for carbon dioxide? We invited Margaret Leinen, from Climos, and Dr Chris Vivian, from CEFAS, to discuss the pros and cons of...
20 January 2008

Interview with 

Dr Margaret Leinen, Climos & Dr Steve Vivian, CEFAS


Chris - It's hard to turn the radio or television on now and not to be told to reduce your carbon footprint or be more green and things like that.  That's not the message of this show though.  We want to talk about, not the problem of climate change but the solution. On the line now is Margaret Lienan.  She works for Climos which is a company based in the United States.  Hello, Margaret.

Margaret - Hello, how are you?

Chris - I'm very well, thank you.  Your plan is to try to lock away CO2 and solve the problem of climate change by encouraging the oceans to soak up more of it.  How does it work?

A phytoplankton bloomMargaret - Well, a few years ago in studying what controlled the biological productivity of the oceans scientists found that most of the open ocean far away from land was limited by iron.  Iron is very insoluble so iron from rivers precipitates out close to shore.  Far away from land the iron often comes from dust storms that move out far over the sea and then fall into the water.  We did both experiments in the laboratory and observations at sea.

Over the last twenty years they've done a set of a dozen experiments at sea spreading fairly soluble iron (iron sulphate) to see what happened.  They found in every case that there were very, very big phytoplankton blooms.  Phytoplankton are the small, microscopic plants of the sea.  So when phytoplankton bloom they take organic carbon out of water and CO2 from the atmosphere.  Some of that organic carbon is eaten or decomposes close to the surface so nothing happens to it.  Some of it sinks much deeper into the ocean where it's protected from exchange with the atmosphere.  The big question is, 'how much of that is sequestered?'  That's what the current round of scientific experiments that are proposed are designed to answer.

Chris - So what you're saying is that the dead bugs that fall to the bottom of the sea will end up locking away carbon in a form where it won't resurface in the atmosphere.  So in that respect it's almost like turning it back into coal?

Margaret - Well, yes.  The sequestration is not as long-term as turning it back into coal.  It's sequestered for periods of 100-1000 years rather than up to millions of years like coal.

Chris - So what you're arguing then Margaret, this is a way of buying us time rather than solving the problem of climate change.  It locks the CO2 into a position where it can't cause trouble while we sort ourselves out and get our house in order.

Margaret -   That's exactly right.  Not only that, it's not a silver bullet.  This will not solve the CO2 problem but it can help in the same way that every other technology and approach that is being discussed can help with the problem.

Chris - It doesn't sound particularly environmentally friendly though.  There must be some possible unforeseen effects of scattering large amounts of iron sulphate, that's quite acidic in itself, onto the surface of the ocean to then create a bloom or a massive growth of just one species of marine organisms.  There must be knock-on effects of that.

Margaret - Several things.  First of all it doesn't just stimulate one species.  It stimulates a whole set of species with time.  We know that both from looking at how this happens naturally.  Remember all of those very large quantities of iron go out onto the ocean all the time.  That's what actually stimulates the blooms.  That set of questions about what are the consequences for the chemistry and biology of the ocean are very important.  Of course, the first set of questions is, 'does this work, does it really sequester CO2?'  Previous experiments weren't well-designed to answer that question.  That suggests a new set.  If it does sequester CO2 then we need to know about the consequences for chemistry and biology and what do they tell us about the limits to which this could and should be used to draw down CO2.  You're obviously going to have to balance that against the problem of CO2 in the atmosphere, what it does in terms of acidification of the ocean and so forth.

Helen - Margaret, you say that previous tests weren't really conclusive as to whether or not this was going to work.  Are you looking at trying to answer that question now and what are you doing to try and get to that answer?

Margaret - Our company is trying to bring private funding sources to the ocean science community to enable them to answer the questions.  What they want to do is have a set of larger area experiments so that they would fertilise areas of the ocean about 100X100km. They would want to stay much longer to really observe this whole sequence of activities in the bloom rather than just say, 'oh yes, phytoplankton bloomed.'  Then they also want to bring new state-of-the-art sampling here to the ocean.  We then have a lot of the remotely robotic autonomous vehicles during the time that the experiments were done.

Finally, they want to do a lot more modelling to understand how long the CO2 will remain in the ocean and how soon the ocean will re-equilibrate and pull CO2 out of the atmosphere.

Chris - Climos is a company so you must have a business model.  How do you expect to make money from this?

Margaret - If carbon is sequestered and that has to be demonstrated in a rigorous fashion with measurements, with external observers, with very open data then the carbon that is sequestered can be sold as carbon offsets on the voluntary market.

Chris - This seems like a good opportunity to bring in Chris Vivian.  He's from CEFAS, that's the Centre for Environment, Fisheries and Aquaculture Science.  I guess that makes you the oceanographic equivalent of DEFRA, Chris?  How do you react to what Margaret's saying?

Chris Vivian - Hello Margaret, good to hear from you.  Margaret's quite right in many respects that we still don't know enough about exactly what happens in these situations.  There's a large degree of uncertainty.  A lot of issues to be resolved.  Some of the issues you mentioned we just don't have answers to at the moment.  The experiments that Margaret was talking about should help to identify that.

Chris - What are the big worries?

Diatoms - a key Phytoplankton groupChris Vivian - Some of the issues that have been raised are will we change the phytoplankton community in the oceans by doing repeated experiments of this type?  Will we, through putting a lot of organic matter deep into the water, change the oxygen conditions there reduce the oxygen?  Will we change the pH, will we create the additional other gases which may have global warming potential.  Some concern has been raised with nitrous oxide.

Chris - CO2 comes down, comes up as something even worse?

Chris Vivian - Could be nitrous oxide, or methane for example, can be generated by plankton groups.  We don't know enough about those yet to understand whether they are significant.  They may be, they may not be.

Chris - Let's see if Margaret can offer us any reassurance on that score.  What do you think Margaret?

Margaret - Well, we totally agree with Chris [Vivian] that those are the issues.  He raised some that have to do with how much CO2 you can sequester and also what the side-effects are in terms of other greenhouse gases; then those other questions about biology and chemistry.  We certainly know that you do change the oxygen conditions in the ocean because that CO2 that falls deep into the ocean- I'm sorry it's not CO2, it's organic carbon that falls deep into the ocean- it is changed by combination with oxygen into bicarbonate.  The question is that we need these experiments in order to answer those questions.  We think that this first phase has to be very carefully designed in order to answer both the sequestration questions and the biology and chemistry questions.

Chris - So Helen, as a marine biologist, how does this sit with you?  Are you worried because we've seen umpteen examples where you change once species quite dramatically and get knock-on effects with other things.  We've had huge plagues of jellyfish because we've removed all the big fish that would have eaten them.  So what do you think the catches of this could be?

Helen - I think you're quite right.  I think, to be honest, the implications are potentially huge and we really don't understand them yet.  That's the problem with the oceans, they can be so complex:  the interactions between different groups of animals and plants.  Predicting that's going to be really difficult.  I think you could generally take an approach that you are messing with something you don't understand so why do that?  Maybe because what we're going to achieve will be important enough to do that.  I think we just don't know, that's the problem.

Chris - It's not very reassuring, Chris.

Chris Vivian - Well, at the moment I think it's far too early to judge whether this could be a viable mechanism to offset climate change to any degree.  Certainly the estimates that have been made are that it probably could only be a relatively minor one.  That's not to say lots of minor ones might not add up and be useful if they are otherwise acceptable.  One could not rule it out at the moment but I think it's far too early to say that it would be a viable option right now.

Chris - What do you think a better option is if this is not going to be something which actually has legs.  What should people be putting their resources into?

Chris Vivian - If we look at what's happening now in a number of countries in various parts of the world, things like carbon capture and storage in sub-geological structures is being pushed quite hard by the UK and other governments around the world because they believe there's a lot of capacity for that.  Some of these things will take quite a bit of time to bring into effect.  That's probably the biggest one that has the biggest capacity, we think.  It will require a lot of money to get it worked up into a viable and practical option.

Helen - I know we said we weren't going to talk about problems of climate change but I just wondered maybe, Chris [Vivian], what you think about how much this really takes people's minds off the problem of creating CO2 in the first place.  Does this make us feel a bit better if there's an option to mop it up then we don't have to worry about creating it in the first place?

Chris Vivian - That is certainly a concern that's been raised by NGOs in some of the international discussions.  They feel there is a danger that some countries will see this is a way to avoid doing anything.  It's certainly a concern.  Certainly governments view it as one means of trying to help deal with the problem.  We've got to, in their view, apply a portfolio of all sorts of options including the sorts of things we've talked about for energy efficiency and renewables etcetera.  We need to hit it with everything really to try and address the problem.

Chris - The oceans have suffered quite badly because of the effects of global warming and they continue to do so.  The models predict that they will.  The oceans are going to become more acidic, for example.

Chris Vivian - You're exactly right.  That is certainly probably one of the major effects of climate change that wasn't fully appreciated early on.  Just that over the long term we're going to make oceans distinctly more acid so we are threatening, for example, the existence of corals in the world ocean.  Possibly, in something like 100 years there will be great danger that we'll have hardly any corals left in surface waters because the oceans will be too acidic.

Chris - Margaret, when do you see the strategy for getting this tested and then perhaps into a phase when you're selling carbon credits by seeding the ocean in the way you describe?

Margaret - I think that we're planning for the first experiment that we will give funding to the oceanographic community to do, probably in about a year.  I anticipate that we're probably looking at a period of a few years.  Three to five years of experimentation to answer the questions that you've raised and that Chris has raised; to see whether this technique is effective and if so to what degree should it be used.  I think that one of the very attractive things about it is that it does actually remove CO2 from the atmosphere, not just limit emissions.  Chris [Smith] raised the issue of acidification and it's a very serious one.  We're stuck with that so long as there is all of this excess CO2 in the atmosphere.  Again, this technique wouldn't remove all of it but it could help.

Chris - Chris?

Chris Vivian - Yes, indeed. I think that's probably correct and certainly there's a recent publication in the journal Science, by sixteen leading scientists in this area of ocean iron fertilisation have identified a series of issues that need to be addressed before we think it can be justifiable if they were resolved satisfactorily.  It would seem to be that they are going to take a significant amount of time to resolve.  I couldn't make a judgement of how long but I would certainly be surprised if it was less than five years, put it that way. That's my personal judgement.


Add a comment