
University of Exeter
SeaCURE
"SeaCURE is accelerating the ocean’s natural removal of atmospheric carbon. SeaCURE has developed and demonstrated the components of a marine-based Negative Emissions Technology (NET), with the potential to be applied at very large scales."
Professor Paul Halloran
Special thank you to Professor Paul Halloran, University of Exeter, for answering the NCEC Interview questions below. Paul Halloran is leading the SeaCURE team. SeaCURE is a collaboration between Exeter, who is leading the work, Plymouth Marine Laboratory, Brunel University in London, and the engineering firm ELIQUO HYDROK. He is leading projects that focus on removing carbon dioxide from seawater and has over 20 years of experience in ocean carbon and ocean climate impacts. Paul Halloran and the SeaCURE team are leading internationally in developing robust approaches for Monitoring, Reporting and Verification (MRV) on marine-based Carbon Dioxide Removal.
NCEC Interview Questions
1. How does SeaCURE contribute to removing carbon from the atmosphere?
SeaCURE started in 2019 in response to a UK government call to develop novel approaches to remove greenhouse gases from the atmosphere. Coming from a background in ocean carbon chemistry and ocean carbon cycle, we saw the ocean as a sensible starting point for thinking about atmospheric carbon removal because it exchanges CO2 freely in the atmosphere and concentrates that carbon. The SeaCURE project takes seawater, which is naturally carbon dioxide rich, and by lowering its pH to around pH four — approximately the pH of tomato juice — turns all of that carbon into CO2. Because there is a very high concentration of CO2 in that water, it can straightforwardly be extracted through a range of existing extraction processes. We then return the alkalinity of the water, and with it the capacity of that water to take up further CO2 and return the water to the ocean where it will return to its original carbon concentration by taking CO2 from the atmosphere. Essentially, it's an indirect approach to removing CO2 from the atmosphere based on changing seawater chemistry, temporarily, to extract CO2. The nice thing about it is when the water is released back to the ocean, and has absorbed CO2 from the atmosphere, the chemistry of that water is exactly the same as it was before it came into the plant.
We’re now commissioning the plant before moving on to operational testing to prove that the technology works outside of the lab, collect lots of data, better understand it’s real-world potential, and identify the next set of challenges to be overcome to take technology of this sort to scale.
2. What are the biggest challenges you’ve faced in carbon removal?
There are many challenges in taking a technology like this, or any CDR technology, to a scale where it's having a meaningful impact on the climate. Whole supply chains need to be reorganized to be able to do anything like this at a the scales required, as well as overcoming technical, scientific and societal hurdles.
The two fundamental challenges to SeaCURE’s approach are:
1. The amount of energy required to operate.
2. Lack of knowledge of how the elevated pH water – a result of having removed the carbonic acid from the water - released back into the ocean might impact marine organisms.
Our pilot plant is currently considerably more energy intensive than the leading Direct Air Capture (DAC) approaches, so the immediate question is how far can that energy consumption drop, and how quickly can it move towards that endpoint. Marine carbon removal is inherently messier than DAC, so for it to make sense in the long term, it needs to be cheaper – a big part of cost being tied to energy intensity - or offer other advantages such as useful biproducts, additional services or be complimentary in how/where it can be deployed and run. At this stage we don’t have answers to these questions, but it is imperative that we deliver these answers quickly so that time, expertise and finances and be invested in the solutions which are ultimately going to meaningfully benefit out climate. We’re very keen to work with the NCEC community to do this.
The other big challenge is that we're releasing decarbonized water, so that's water without the normal amount of carbonic acid in it. This means that until it has replenished its carbon from the atmosphere, with a typical timescale of months, it's got a high pH – it is alkaline. The language around alkalinity is confusing, but we're not changing the water’s alkalinity, as is done in ocean alkalinity enhancement, but the reduction in acid temporarily elevates the water’s pH. We know very little about what high pH water does to different organisms. Similarly, immediately downstream of the plant, the water has a low carbon concentration. Again, we don't know what the limits are to what carbon concentrations are required for different organisms to photosynthesize, for example. When you move to big scales, seawater chemistry anomalies that would only be measurable a few meters downstream of a pipe pilot plant could impact a large area before mixing and absorption of CO2 returns the chemistry of that water. We need answers to these questions before these technologies can be responsibly scaled up, permits for large-scale operation can be issued, and the social license for this kind of activity can be fully developed. Developing that kind of evidence base is one of the biggest challenges to this approach and frankly all marine carbon dioxide removal approaches.
In our project we’re culturing a range of organisms in decarbonized water. We've had a PhD studentship working on this at the Plymouth Marine Lab. They’re producing decarbonized water and studying the effects on organisms.
We want to be in a position where we can do extensive testing, then hand in hand with regulators, step up a scale and test again. Ultimately this needs to be done in the real world because there's only so many organisms you can comfortably grow in the laboratory and who knows what sort of synergistic effects there may be. This is a big and expensive challenge, but it'd be great to bring the whole of this community together to move this forward.
3. Who are the key stakeholders in the carbon removal space?
There are common stakeholders to any carbon removal activity: for example, those investing and those purchasing the carbon credits. Then there's the whole industry around building, maintaining, and producing these plants. The key one perhaps that differs here compared to more established carbon removal activities is this piece around the potential marine impacts and its regulators. In the United Kingdom it's quite a complex environment. There's a huge number of different regulators who look at different marine aspects from different directions. We're doing a lot of work with them now to understand their roles, how they would regulate this and how that can be done safely. These requirements are likely to vary in each country, but we’re hoping that we can at least provide a template to help others thing about how to do this.
4. Who else is doing work like this in the field?
Capture, a Caltech spinout has a 100 ton/year pilot plant and they’re working on a 1,000 ton/year pilot plant, and SeaO2 and a Netherlands based spinout are working towards a pilot plant. Workshops have been held by Exeter and the SeaCURE team with a range of stakeholders including universities, industry, regulators and academics together to help facilitate the conversation and progress. These workshops have also discussed what the verification of the removal looks like, what the big challenges are, and where the effort needs to be focused.
5. How is this a viable financial model?
SeaCURE is a research project, so one of the things we’re doing is generating data to understand financial viability. In the short term, because a number of purchasers of high-quality carbon removal are happy to pay high pricing to stimulate the market, there is space for small scale commercial operation of these kinds of technologies. For the longer term, there are very likely to be entities that would underwrite the basic costs or removal, for example through contract for difference schemes, derisking investment in plants built during a period of rapid cost reduction, allowing companies to cover costs and assuming demand remains high, profit from the sale of credits.
Activities like these are trying to stimulate or help maintain a diversity of solutions because the companies and the public sector understands they're not going to be able to pick the long-term winners straight away.
The pilot plant is built in a very flexible way. We can, for example, adapt the way it is operated so that it is not direct removing carbon from the seawater, but enhance the storage of carbon in the seawater. This could be attractive in regions where they don't have geological storage for carbon dioxide, but they still want to remove carbon within their own national boundaries - the ocean may become the storage location for that carbon.
6. What happens to the carbon when removed?
As far as we know, uniquely amongst direct ocean carbon removal pilots, we are taking the carbon removed from the seawater to the near-purity required for transportation and geological storage. However, the pilot’s aim is to demonstrate the process and identify how to move it forward, so we are not yet directly linking with carbon storage infrastructure.
7. How are you measuring carbon removal and how is it verified?
The removal of carbon from the atmosphere happens downstream of where the plant is. We must follow that water and understand what carbon removal is happening over days, weeks, and months downstream of that point. We are developing the methodology for the measurement at the same time as undertaking the pilot plant build and operation. We've been doing a lot of modeling work, field work, and numerical work to demonstrate how this is best done and start to understand the uncertainties associated with it. We have to rely on models as well as observations, because the water travels so far.
8. How do you work with local communities? And how is the community perceiving this technology?
SeaCURE is based in a local public aquarium that has been very supportive and is a useful partner. They understand the need for this kind of activity. The regulatory community that is involved has been supportive and engaged as well. We’re now working on projects to start these conversations with the public and beyond to understand and shape the social license for this kind of activity at larger scales.
9. How can NCEC help advance your work?
It's very early days for this kind of technology. It would be wonderful to build on the expertise and resources across different institutions involved in this consortium to begin to answer some of the questions we’ve discussed, and understand if, how and where this kind of technology could be responsibly deployed to help us move towards a safe, stable climate.