Updated in January 2025.
Oceans have long been seen as part of the solution to rising greenhouse gas emissions. With over 30% of CO2 absorbed in them, as well as 90% of excess heat, ocean carbon removal has emerged as another branch of the carbon industry with the promise of sparing us some of the impacts of global warming.
The last few years have seen a number of startups emerge, either adopting their own new technologies or spinning off from universities after announcing promising research.
A bit of clarification before we go into the list. We use the blanket term “ocean carbon removal” to refer to all seven approaches according to non-profit Ocean Visions: Artificial Downwelling, Deep Sea Storage, Electrochemical Ocean Carbon Dioxide Removal, Macroalgal Cultivation, Marine Ecosystem Restoration, Microalgae Cultivation and Ocean Alkalinity Enhancement.
We’ve arranged the companies alphabetically and selected them based on their adoption of either one or multiple approaches. In any case, we feel they are the ones that have generated the most excitement and attention in the last year.
But with great promise come great risks. We’ve also provided some background about the dangers these approaches pose, as well as the efforts to create policies for regulating the industry.
Captura
A spin-out from Caltech, Captura was founded in 2021 by two of the university’s professors—CX Xiang and Harry Atwater.
Its visualization of a full-scale carbon removal facility also triggered the imagination of those hoping that ocean carbon removal can have a substantial impact.
Relying on a new variation of electrodialysis, the company’s approach utilizes Henry’s law by taking CO2 from the ocean, creating an imbalance, causing the ocean to draw down carbon dioxide from the atmosphere to compensate for the one it lost.
In an interview with Carbon Herald, Captura CEO Steve Oldham (former CEO of Carbon Engineering) shared that “Direct air capture is a perfectly good solution, but it’s quite expensive … Fundamentally, Captura’s approach is taking CO2 out of the ocean so that the ocean draws down the same amount of CO2 from the atmosphere. If you can do that in a way that doesn’t harm the ocean, you have a very cost-effective and highly scalable way to take CO2 out of the atmosphere.”
The company’s first pilot was launched in August 2022, and in May 2023 they deployed a 100-ton system at the Port of Los Angeles.
Following a series of successful funding rounds, in October 2024, Captura announced plans for expanding its research, development, and demonstration (RD&D) capacity in Los Angeles, installing new equipment to test and refine its electrodialysis and gas extraction processes.
In partnership with Equinor, in November 2024 the company also began work on a pilot project in Hawaii, slated for completion in the beginning of 2025. Once fully operational, this site will be able to capture 1000 tons of carbon from the ocean annually.
Captura ended 2024 on a high note, sharing plans for commercializing its direct ocean capture solution in Japan by 2026.
Ebb Carbon
Ebb Carbon was established in 2021 by co-founders Matt Eisaman, Dave Hegeman, and Ben Tarbell.
CTO Eisaman has been working on Ebb’s ocean carbonate system for a decade, perfecting an electrochemical process that can not only remove CO2 but also reduce ocean acidity.
CEO Ben Tarbell is a mechanical engineer and served as VP of products for SolarCity before joining Google X as climate tech research lead. Dave Hegeman completes the leadership team as VP of Engineering.
The main example of where and how Ebb Carbon’s system can work is at a desalination plant. It utilizes the saltwater flows there by pulling acid out from the brine flow (generating acid can then be sold as a product).
The treated seawater is then returned to the ocean with slightly higher alkaline levels, where it reacts with atmospheric carbon dioxide to form bicarbonate while simultaneously decreasing water acidity.
Ebb Carbon points out that their tech is modular and can be fitted onto a wide variety of coastal industry plants. The company’s potential has been noticed by both XPRIZE and the DOE’s carbon removal purchase prize.
Having secured a $22 million Series A funding, the company kicked off a pilot project in collaboration with the Department of Energy’s (DOE) Pacific Northwest National Laboratory (PNNL) in Washington.
In October 2024, Ebb Carbon made headlines by signing the largest to date marine carbon dioxide removal (mCDR) deal with Microsoft for the removal of 350,000 tonnes of CO2 over the following 10 years, cementing its leading position in this emerging industry.
Equatic
Equatic is a carbon removal startup that spun out from the UCLA Samueli School of Engineering’s Institute for Carbon Management.
Equatic’s unique approach utilizes the ocean’s natural ability to sequester carbon dioxide and speeds it up using a single process that in the end not only results in permanent CO2 removal, but also produces carbon-negative hydrogen.
The company has two pilot plants in Singapore and its hometown of Los Angeles, both of which are operational and busy removing CO2 from the atmosphere.
2024 was a big year for the company, marked by the announcement of plans to build one of the world’s largest ocean carbon removal plants, a shared project of UCLA and the National Water Agency of Singapore.
This ambitious project, set to be constructed with engineering help from Arup, will build on the experience gained from the Equatic-1 project in Singapore, which boasts an operational capacity of 10 electrolyzers, each one of them removing 1 tonne of CO2 per day.
Expected to come online in 2026, the new plant will have an annual carbon removal capacity of 100,000 tonnes, with plans to expand to millions of tonnes per year in 2030.
In 2024 Equatic started producing its oxygen-selective anodes (OSAs) technology in the United States and welcomed leading industry names to its team, appointing Chief Operational Officer (COO) Edward Sanders to a new role as Chief Executive Officer (CEO).
In an interview with Carbon Herald, Sanders said, “Equatic-1 is really important for us, as the demonstration facility will have around 3,650 tonnes of CO2 removal capacity annually.”
“We will have the modular reactor operating at this scale for the first time. Equatic can then systematically duplicate the modular reactor and start benefiting from manufacturing at scale.”
The company plans to ramp up its operations to reach millions of tons by 2028, which is expected to bring down the cost to under $100 per ton of CO2.
Gigablue
Gigablue has positioned itself among the front-runners in the ocean carbon removal sector with the largest-to-date mCDR deal signed with aviation sustainability company SkiesFifty.
The historic agreement will see Gigablue remove the record amount of 200,000 tons of CO2.
The New York-based company has developed a technology that follows the natural principles of the ocean for pulling down atmospheric CO2.
Their solution is a substrate that gets released into ocean water, where it collects CO2 from the surface water levels, taking it to the ocean floor sediment for sequestration in a controlled and measurable way.
Made from a nutrient shell and a core that has a gravity-controlling capacity, the substrate provides a favorable environment for local phytoplankton to flourish, growing them to amounts that activate the controlled sinking trigger, which then sinks the substrate and the attached CO2 to the ocean bottom for permanent storage.
Powered by natural elements like water, sunlight, and gravity, this solution has the competitive edge of being more cost-effective than other available options, signaling a real chance of reaching gigaton removal levels due to its financial feasibility.
When it comes to tracking the impact of this technology, Ori Shaashua, co-founder and chief commercial officer at Gigablue, explains, “There is a third party, an independent third party that works in parallel to us, the National Institute of Water and Atmosphere of New Zealand (NIWA). We are sequestering, and they’re measuring.”
The company has already deployed its innovative tech in the waters of New Zealand, with plans to expand to other geographies in the future.
Kelp Blue
Kelp Blue, a company founded by oil industry veteran Daniel Hooft, is set on a mission to fight climate deterioration by growing and managing large-scale Giant Kelp forests.
The company entered the carbon removal spotlight by being selected as one of the top 20 finalists in the Ocean category of the XPRIZE Carbon Removal competition.
Headquartered in the Netherlands, Kelp Blue is led by a vision of removing over 1 million tons of CO2 annually by 2029 through 70,000 hectares of Giant Kelp farms located 30-100 km offshore from the town of Lüderitz in Namibia.
Besides its project in Namibia, the company also cultivates Giant Kelp sea forests off the coasts of Alaska and New Zealand, with plans to expand to more regions in the future.
The Kelp Blue grows the Giant Kelp algae in a facility they call the Hatchery. Once mature enough, the algae gets attached to farming structures submerged in ocean water, which reach a depth of 15m below the surface—an optimal growing environment for the kelp.
Using monitoring methods like acoustics, visual observations, water sample analysis, and environmental DNA, the team keeps a close eye on the kelp, measuring the water quality and performing lab tests to access the dissolved organic CO2.
The biomass generated on the farms is collected for usage in agriculture and the packaging industry, while the kelp itself is processed to extract its bioactive compounds for the creation of crop-boosting biostimulants.
These underwater forests cultivated by Kelp Blue safely lock away vast amounts of carbon dioxide, and the company is confident that this solution offers a cost-effective pathway to restore environmental balance.
Limenet
Limenet is a fast-advancing Italian company that specializes in ocean CO2 storage in the form of bicarbonates.
The company utilizes an ocean alkalinity enhancement (OAE) method to remove atmospheric CO2 and store it in seawater. OAE as a removal approach has attracted a lot of attention as it also counteracts ocean acidification.
Limenet’s OAE method starts with the heating of limestone—an abundant natural resource. This heating process, powered by renewable energy, releases CO2 and converts the limestone into quicklime, which gets mixed with water to produce slaked lime.
The CO2 capture happens during the carbonation of some of the slaked lime, which naturally absorbs carbon dioxide from the air when exposed to it, or by using biogenic CO2 from biomass gasification.
In a Limenet reactor, the CO2 released from the limestone or the pure captured CO2 in the next step of the process reacts with seawater and with the slaked lime that didn’t capture CO2, creating bicarbonate, a marine alkalinity agent that has the same pH as seawater.
Speaking to Carbon Herald, Limenet CEO Stefano Cappello explains that it is so urgent now to restore balance in ocean chemistry that the benefits from adding calcium bicarbonate and calcium carbonate can far exceed any hypothetical risks.
Limenet has experienced rapid growth since its establishment in 2023, taking only 18 months from its launch to create one of the world’s largest facilities for CO2 ocean storage.
With a maximum annual storing capacity of 800 tons of CO2, the Limenet industrial facility in Augusta, Sicily, in Italy will expand in the future, integrating Direct Air Capture (DAC) technology to facilitate passive mineralization of lime.
Planetary Technologies
Planetary Technologies, one of the 15 winners of the XPRIZE Carbon Removal award in April 2022, is driven by the mission of capturing 1 billion tons of CO2 from the atmosphere by 2045.
The company’s novel approach kills four birds with one stone: it removes CO2 from the air, restores the ocean’s natural acidity, and purifies mine waste, turning it into nontoxic antacid.
In turn, the antacid is released into the ocean, where it restores the seawater’s pH levels, thus accelerating the ocean’s natural ability to pull carbon dioxide from the air.
Finally, the process results in the production of green hydrogen, which many consider to be the fuel of the future and allows hard-to-abate sectors to rely less on the use of fossil fuels.
While proposing a trial of its technology in Hayle, UK, Planetary received a report commissioned by the Environment Agency (EA) that deemed its method as “very low” risk to marine organisms.
The company has an operational project in Nova Scotia and has provided its support on the Elizabeth River Project.
In the spring of 2025, Planetary intends to roll out a small-scale field trial in Vancouver while still researching and mapping out the St. Ives Bay project in Cornwall.
Speaking to Carbon Herald, CEO Mike Kelland shared, “Ultimately, how I expect a gigaton level of carbon removal to work is having relatively small-scale additions at a huge number of sites around the world. The reason for that is it reduces risk over time.”
Towards the end of 2024, Planetary reached a key milestone by delivering the world’s first OAE carbon removal credits.
The company managed to successfully remove 138 tonnes of CO2 as part of a prepurchase agreement with Frontier, providing 96 tonnes to Shopify and 42 tonnes to Stripe.
Having secured $11.35M in Series A funding, in the long run, the company aims to remove over one million tonnes of CO2 every year by 2028 and even gigatonnes by 2050.
SeaO2
The aptly named Dutch startup SeaO2 was founded in 2021 with the striking goal of removing 1 gigaton of carbon dioxide by 2035 via Electrochemical Direct Ocean Capture (DOC).
Founders Ruben Brands, Rose Sharifian, and David Vermaas have refined a technology that first emerged at Delft University of Technology (where Sharifian is a Researcher PhD candidate and Vermaas an associate professor) and Wetsus laboratories.
SeaO2’s approach uses the flow of ocean water through a capture plant, taking seawater at 50-100 meters depth and subjecting it to an electrochemical reaction that separates CO2 in a gaseous form. After the process, the treated water is returned to the ocean’s surface, where it can again absorb CO2.
The company says the technology can be retrofitted to existing industrial installations and that the compressed CO2 it generates can be directed towards storage or utilization.
SeaO2 made the top 60 cohort in the XPRIZE Carbon Removal competition, and in 2024 the company completed the CEEZER Carbon Coalition accelerator program.
Having already entered several pre-purchase agreements with the likes of Ledgy and Klarna, towards the end of 2024 SeaO2 also managed to secure $2 million in seed funding.
With this financial injection, SeaO2 will focus on scaling operations from a prototype level to a pilot launch scheduled for 2025, pushing towards a removal capacity of 250 tons of CO2 per year.
Vesta
Project Vesta offers the world a very promising approach to ocean CDR in that its solution revolves around a material that is already available in abundance—sand.
The solution is what is referred to as enhanced coastal weathering. Namely, the company found that adding small amounts of the finely ground mineral olivine to regular beach sand can help pull more CO2 from the air and even restore eroding coastlines.
To showcase this concept, Vesta launched its first demonstration project in Southampton together with NSBC Beach Erosion Control District (NSBC-BECD) in the summer of 2022.
The company has also been working together with the public and private sectors to provide the necessary knowledge on the implementation of its approach in coastal regions.
As olivine is one of the most common minerals in the world, Vesta’s climate solution is not only scalable but can potentially be more cost-effective than many other alternatives.
In 2024, the company became the first applicant to receive permits for a standalone ocean-based carbon removal pilot in the United States.
Following an extensive consultation with the local community and with approval from the North Carolina Department of Environmental Quality and the U.S. Army Corps of Engineers, Vesta proceeded with depositing 8,200 metric tons of carbon-absorbing olivine sand near the shoreline of Duck, North Carolina.
This trial is expected to result in the removal of around 5,000 tons of carbon dioxide.
Vycarb
Founded in 2022, Vycarb is a Brooklyn-based technology that has developed a unique CO2 neutralization process and a pioneering carbon sensing technology.
The tools developed by the company enable a scalable and fully-measured carbon capture, removal, and storage.
Their open system CDR approach leverages a natural reaction that converts CO2 to bicarbonate and carbonate to store carbon in the oceans.
What sets Vycarb apart from other solutions on the market is the cutting-edge monitoring system that controls the pH-mediated neutralization reaction by actively dissolving a range of natural minerals, making sure that CO2 is stored safely and permanently.
The technology is being demonstrated in live pilots on the US East Coast.
In October 2024, the company launched its largest pilot project on New York City’s East River. On an annual basis, this project will work towards permanently removing and storing 100 tons of CO2.
During its short existence, Vycarb has attracted the attention of various investors, locking in funding from Rio Tinto, the Earth Fund by Twynam, prepurchase deals with Stripe and Milkywire, a $100k sale with Frontier, and a potential first-of-its-kind CO2 removal deal with the US federal government.
In 2024, Vycarb also made the list of 24 semifinalists for the Carbon Removal Purchase Pilot Prize organized by the US Department of Energy (DOE).
In an interview with Carbon Herald, Vycarb founder and CEO Garrett Boudinot shared that the company will continue to scale up and increase capacity at the East River pilot, simultaneously working on two other noteworthy plans lined up for the future.
Risks
While the world’s oceans have the unrivaled potential to remove CO2 from the air at gigaton scale, the many different ocean CDR solutions developed by scientists and companies may still pose certain risks to the environment.
Ocean experts warn that ocean-based climate interventions (OCBIs) are likely to have an immense impact on entire ecosystems, and for that reason, research is constantly ongoing to determine the exact effect of the different mCDR approaches.
Policy
The world is still in need of robust policies and legal frameworks to advance scientific developments in the field of ocean CDR.
At the beginning of 2025, ocean CDR is visible on the radar of policymakers, yet there are still no clear and actionable decisions when it comes to regulations.
For example, in mid-2024, the US Department of Energy and the National Oceanic and Atmospheric Administration (NOAA) signed a memorandum of agreement (MOA) to accelerate ocean carbon removal, while in January 2025 a group of US Congress members proposed a bipartisan legislation for the advancement of mCDR in the United States.
Carbon Removal Canada outlined extensive guidelines for policymakers on how to boost the CDR and mCDR sector in the country, while towards the end of 2024, the NOAA partnered with Carbon To Sea to standardize data management for ocean-based CO2 removal.
These initiatives signal action in the right direction, however, businesses and stakeholders keep highlighting the urgent need for clear rules and frameworks for further mCDR development.
As Ori Shaashua, Co-Founder & CCO of Gigablue, recently explained, “In a proper market, you have all the rules defined. It’s very clear what you should do and shouldn’t do. And due to this clarity, there is freedom to operate because as long as you’re following the rules, you’re in a good place.”
