ANALYSIS: Can marine CDR overcome its many challenges to deliver removals at scale?

Quantum Commodity Intelligence – Maine-based Running Tide became the second company in the marine carbon dioxide removal (mCDR) space this year to exit the market, when it announced last month that it was starting the process of shutting down operations. The company cited similar reasons – lack of finance – to another US company, Oceanid MRV, for the reason it was winding up its business.

Running Tide had been a prominent and vocal proponent of mCDR and even in its closing announcement said there was no issue with its technology – carbon capture and removal by deploying floating buoys containing limestone and algae, which are then sunk into the deep ocean.

The same month saw a chapter in a report, while acknowledging the potential of oceans to sequester and store carbon dioxide (CO2), raise a host of issues with mCDR. These include technical, environmental, political, legal and regulatory challenges. It said more research is needed for a better understanding of how oceans sequester carbon.

The chapter focused on mCDR in the UNESCO Intergovernmental Oceanographic Commission's 'State of the Ocean Report 2024' argued that currently there are "major unknowns" on how removal approaches will interact with the carbon cycle in the ocean and whether they will create "feedbacks" that lead to unintended consequences.

Market players do not dispute the conclusions, but feel the need for more research and companies exiting the sector are not reasons to write off mCDR.

"Looking at the observation at the end [of the chapter] – that there are many unknowns before a decision can be made about large-scale deployment – I think that's the key, 'large-scale deployment', and I absolutely agree," said Steve Rackley, scientific advisor at Canada-based mCDR developer Planetary Technologies.

Rackley, who is based in the UK, pointed out that mCDR has many different pathways each of which has different challenges.

Different ocean interactions

"The technical, political, environmental challenges differ whether you're looking at kelp farming and sinking as was Running Tide's approach, at one end of the spectrum, electrochemical CO2 removal techniques in the middle, or ocean alkalinity enhancement, as Planetary approaches it, which is the mineral addition pathway at the other end," he said.

This is because each of the mCDR approaches have different potential interactions with the oceans systems, he added.

Planetary ocean alkalinity enhancement (OAE) involves adding pure antacid to seawater from existing coastal outfalls to "neutralise acidic CO2" and transform it into a stable salt to support marine life and store carbon for thousands of years. The company's most advanced project is at Tufts Cove in Halifax, Nova Scotia, with others in development in Vancouver, Virginia and in Cornwall in the UK.

"Nova Scotia is the biggest project, so that's been multiple years of academic collaboration starting in the lab and, as of last year, moving into the field," said Planetary's chief ocean scientist Will Burt. "That's really not only leading our projects, but sort of leading most, if not all, of the ocean alkalinity space in terms of developing that technology and just learning about it," he said.

Planetary is also the first company to sign up and use an OAE methodology to generate CDR credits developed by carbon removals registry Isometric.

The protocol's aim  is "advance the field by creating consensus around robust MRV [monitoring, reporting and verification] approaches and sharing key data", said Isometric head of science Stacy Kauk. "The protocol requires taking outflow measurements, using regional and far-field ocean models to quantify air-sea gas exchange over the large spatial and temporal scales of the ocean, and improving models with real world results," she said.

Robust MRV is key to all carbon projects, not just those in the sea, but it is one area that for mCDR is going to be dependent on modelling for some time to come.

"At the scale that we're doing at the moment, beyond a few tens of metres you can't measure any change in ocean chemistry as a result of the quantities of alkalinity we're putting in," said Planetary's Rackley.

"It's widely recognised in the community that modelling, oceanographic modelling using numeric models, is always going to be a major part of MRV for marine CDR," he said. "I expect that when we get to the tens of megatonne scale we'll start to get the capability to measure changes in ocean conditions which can be tied back to marine CDR interventions. We're not there yet; it's going to take quite some time," he added.

"As with all CDR that relies on natural systems, where it's not feasible to measure all inputs and outputs, measurements must be statistically significant and representative and any crediting around these measurements is conservative," said Isometric's Kauk.

She said OAE has high scaling potential because it intentionally leverages oceans' vast surface area and capacity. "MRV in mCDR must be scientifically rigorous, operationally feasible and still leave room for innovation. MRV will only improve over time as we receive more data from marine CDR projects," she said.

A potential advantage for Planetary is that its projects are close to coast, not far out to sea like some projects. "I've been working as an ocean scientist off the coast, largely on multi-week cruises, and the cost of working out there and the complexity of doing measurements and things, it's unfathomable to try and have a business that's focused on that," said Planetary's Burt. Working at the coastline is what gives the company a "huge leg up" in terms of dealing with the complexities of mCDR, he added.

Another important component for Burt for companies to be successful in the space is collaboration. "The way to get past these various bits of complexity are to collaborate. And I think that's the difference between us and other companies as well," he said. In Halifax, for example, Planetary is working with local energy company Nova Scotia Power and with researchers at the local Dalhousie University.

"We've really focused hard on building out large collaborative teams with the academics, because no company can do this even a little bit on their own," Burt said. "We aim to get to a point where we can do this on our own, that's what's going to have to happen, but at this stage, it's much too complex."

He also highlighted transparency, with Planetary having shared publicly the findings of the project in Halifax. "You can't have a large collaborative team with a university and then keep it under wraps," Burt said. "If we try and do things without being honest about our findings and what's working and what's not, then eventually that will bite us," he said

Ultimately, success will depend on investors buying the credits projects generate. Running Tide removed 25,416 tonnes of CO2 from the atmosphere in 2023, and delivered 21,778 credits to over 25 buyers. When Isometric unveiled the OAE protocol and Planetary's involvement, it noted that Shopify, MaRS and Terraset are some of the first buyers from the developer.

"Companies like ours will live and die on whether people want to buy our credits. And whether people want to buy our credits is going to come down to, do they believe in the process that we're doing? And do they believe it can scale?" said Burt.

"That is the goal. We have evidence that that robust MRV exists, or can exist in the near term, and there's plenty of people trying to  buy credits right now, and that's only going to increase."