The State of the mCDR Union

Marine Carbon Dioxide Removal (mCDR), comprising both abiotic pathways (such as Ocean Alkalinity Enhancement and Direct Ocean Capture), as well as biotic pathways (such as biomass sinking or ocean fertilization) has the theoretical potential to sequester nearly 10 Gt CO₂e / year when fully scaled¹, and it has the potential to be very cost effective, through a combination of abundant source materials and relatively low energy requirements². Emissions reduction remains the primary focus of the fight against climate change, but the scientific consensus, as clearly stated by the IPCC³, is that both emissions reduction and CDR will be needed to reach net zero. As such mCDR is likely to be a vital tool in the CDR toolbox - especially if, as seems increasingly likely, the need for CDR will be ongoing to help reverse the damaging consequences of climate change.

Today, the industry is firmly in the chasm between early field trials working to close remaining knowledge gaps, and the beginning of true market growth. Although there has been less 'headline grabbing' activity, the last year or two have seen quiet and steady progress, and many of the key prerequisites for a healthy market are now in place or on track. Abiotic pathways and biotic pathways have followed somewhat different trajectories, with the former seeing faster development of Monitoring, Reporting, and Verification (MRV), early buyers and funding, and further progress towards resolution of key uncertainties, but the latter still facing deeper scientific and ecological uncertainties. However, key challenges with fragmented regulation and public perception remain - and they are perhaps the hardest to overcome.

Ostensibly some of the typical metrics used to measure industry progress have slowed - only 2 companies were started in 2024, compared to 18 in 2022. VC funding is still scarce - 7 mCDR companies received a total of $65m in 2024, only 8% of the whole CDR VC funding pot (the total CDR pot itself was down 30% from the prior year)⁴. Companies with VC funding from earlier years are facing challenges in raising more money. Fewer new trials were launched - only 10 in 2024, vs 19 in 2023⁵.

However, foundational, yet less visible, progress has been happening on multiple fronts. Crucial for the emergence of the industry is robust MRV, and several key protocols are now available or in scientific review⁶. In June, Planetary became the first mCDR company to receive third-party verified Ocean Alkalinity Enhancement carbon credits through the first of these⁷. Funding from the non-traditional sources that have seeded much of the CDR industry is also flowing into mCDR - in January one of the largest pre-purchase deals to date, for 200,000 tons of CO₂ removed, was funded by SkiesFifty, an airline-industry consortium⁸. Frontier continues to provide tremendous encouragement - three of the nine companies funded by Frontier in 2024 were mCDR related⁹, and two out of the three in summer 2025¹⁰. Frontier recently inked a 115,000 ton $30m pre-purchase deal with Planetary¹⁸. Partly as a result of expanding funding, pricing for mCDR credits was no longer the highest of the CDR pathways - and it fell the most from 2023⁴.

2023 was a year of scientific hesitancy in the industry, typified by Ocean Vision's initiative calling for more research which was signed by 400+ scientists¹¹. In 2025, however, scientific confidence is growing for some mCDR pathways as an increasing body of evidence suggests that environmental risks of Ocean Alkalinity Enhancement can likely be managed¹²; thus far no insurmountable challenges have been identified. Many of the field trials launched in the last couple of years are now close to fruition - 13 concluded in 2023-2024, and 19 are underway; many of these are likely to be reporting results in 2025-2026⁵. The rate at which the science is progressing can also be seen in publications - 80+ papers across mCDR and specific pathways were published in 2024, up significantly from 2023¹³.

Many of the key prerequisites for market growth are also emerging. The Voluntary Carbon Market (VCM) is expected to reach $1.6 bn in 2025, up from $1.1 bn in 2024 - but more importantly, it's projected to reach $47.5 bn within 10 years¹⁴, a CAGR of 40%. CDR as a whole may soon have access to the much larger compliance markets - the EU is actively developing methodologies for incorporating CDR into the EU ETS, the EU's flagship compliance market, worth $42 bn in 2024. The German government has already announced formation of a dedicated CDR department¹⁵. Critical elements of an effective market, data sharing and data standards, are now in place for Ocean Alkalinity Enhancement: led by Carbon to Sea, Submarine Scientific, and NOAA, and with the collaboration of dozens of researchers, the first version of the OAE Data Management Protocol was published in August¹⁶.

Regulation continues to be fragmented, with multiple overlapping sets of legislation. Within a nation's EEZ, nations have the ability to permit projects, and some nations are developing the ability to issue permits. However, many forms of mCDR (including Ocean Alkalinity Enhancement, biomass sinking, and ocean fertilization) fall under the provisions of the London Protocol, and so (at least until the marine geoengineering amendment is ratified) would require nations who have ratified the protocol to obtain permits under it. In the US, the FTAC (Fast Track Action Committee for mCDR) was disbanded in 2024, but the recent first-of-a-kind permitting of the LOCNESS field trial by the EPA following an extensive two year review is a promising sign. At scale, however, international cooperation will be needed as the impact of mCDR can extend beyond any nation's EEZ. The High Seas Treaty / BBNJ reached 60 ratifications in September this year, following on from June's UN ocean conference in France, triggering its entry into force in January 2026 ¹⁹; the treaty establishes an EIA (Environmental Impact Assessment) framework covering mCDR.

One of the biggest and most significant challenges today is public sentiment towards mCDR. Without very careful and effective messaging, mCDR is easily seen as a risk, or a threat. Too many news articles opt for sensational headlines misleadingly ascribing the risks of certain activities to the whole field, with the very real possibility of creating an insurmountable and inaccurate negative perception of mCDR as a whole¹⁷. Of course, there will always be the risk of unintended consequences when making changes to chemistry or biology on the scale envisaged. However, many of the potential 'unintended consequences' of many forms of mCDR are likely to be positive. Some forms of mCDR such as OAE and Direct Ocean Capture (DOC) have the potential to be forms of 'ocean deacidification', which in turn can reduce the threat posed by climate change to those who make their livelihoods from marine industries. mCDR has the potential to provide economic and environmental co-benefits to communities, which could provide an economic lifeline in addition to the primary benefit of climate change mitigation. The industry needs to focus on these possible positives (while identifying, monitoring, and transparently reporting any negatives), and to find ways to share these benefits with coastal communities as directly as possible. Public perception may shape the future of abiotic and biotic pathways differently, as the magnitude of potential ecosystem impacts vary.

We at Submarine remain firmly convinced that mCDR can be one of the most effective ways mankind can fight climate change, with the potential to help restore the natural balance of the oceans, and we are excited to be working on the ocean modeling necessary to support the industry's critical need for accurate MRV.

Written by Jonathan Kirk

Co-Founder, Submarine Scientific LLC

References

1: The Ocean as a Solution to Climate Change, High Level Panel for A Sustainable Ocean Economy (Table 18) https://oceanpanel.org/wp-content/uploads/2023/09/23_Ocean-Panel-Climate-Change_DOI.pdf

2: Direct air capture (DAC) vs. Direct ocean capture (DOC)–A perspective on scale-up demonstrations and environmental relevance to sustain decarbonization https://www.sciencedirect.com/science/article/pii/S1385894724059102

3: IPCC CDR factsheet https://www.ipcc.ch/report/ar6/wg3/downloads/outreach/IPCC_AR6_WGIII_Factsheet_CDR.pdf

4: Keep Calm and Remove On - CDR.fyi 2024 Year in Review https://www.cdr.fyi/blog/2024-year-in-review

5: Ocean Visions mCDR field trial database https://oceanvisions.org/mcdr-field-trials/

6: Protocols include:

• Isometric Ocean Alkalinity Enhancement from Coastal Outfalls https://registry.isometric.com/protocol/ocean-alkalinity-enhancement
• Isometric Direct Ocean Capture and Storage Protocol Section 8.2.1.1 (currently in public consultation)
• Isometric Air-Sea CO2 Uptake Module Version 1.1 (Currently in public consultation)
• Microsoft Criteria for High Quality Carbon Removal 2024 and Addendum to the 2024 Edition for Marine Carbon Dioxide Removal
• Puro.earth Microalgae Carbon Fixation and Sinking Methodology (currently in public consultation) https://puro.earth/blog/our-blog/Puro-Launches-Public-Consultation-for-Microalgae-Carbon-Fixation-and-Sinking-Methodology

7: Will Burt's announcement that Planetary's credits are live on the Isometric registry https://www.linkedin.com/posts/will-burt-b074ba99_the-worlds-first-verified-oae-credits-activity-7340376561050673152--gz9/

8: Gigablue Announces Largest Ocean Carbon Removal Agreement with SkiesFifty, Capturing 200,000 Tons Over Four Years — Gigablue https://www.gigablue.co/news/skiesfifty-200kton-carboncredit-announcement-gigablue

9: Frontier Purchase Agreements - GitHub https://github.com/frontierclimate/carbon-removal-source-materials/tree/main/Purchase%20Agreements

10: Frontier Summer 2025 Prepurchases https://frontierclimate.com/writing/summer-2025-prepurchases

11: 2023-09 OV letter of concerned scientists - signed by over 400 https://www.oceancdrscience.org

12: Proceedings of the 2025 Carbon to Sea Annual Convening https://www.carbontosea.org/2025/07/28/2025-annual-convening-proceedings/

13: Searches on Dimensions.ai for papers containing the words "ocean alkalinity enhancement" and "marine carbon dioxide removal"

14: Voluntary Carbon Credit Market - Roots Analysis https://www.rootsanalysis.com/reports/voluntary-carbon-market.html

15: Sebastian Manhart's announcement that the German government is forming a dedicated CDR department https://www.linkedin.com/posts/sebastianmanhart_breaking-german-government-sets-up-activity-7357010981811572736-KEQT

16: Carbon to Sea Initiative OAE Data Management Protocol v1 https://www.carbontosea.org/oae-data-protocol/1-0-0/

17: Using the Ocean to Suck Up CO2 Could Come With the Small, Unintended Side Effect of Wiping Out Marine Life - Futurism https://futurism.com/ocean-suck-carbon-kill-marine-life

18: Frontier buyers sign $31M deal with Planetary to advance ocean alkalinity enhancement - 2025-08-26 https://frontierclimate.com/writing/planetary

19: With 60 Ratifications, BBNJ Agreement to Enter into Force in January 2026 – SDG Knowledge Hub https://sdg.iisd.org/news/with-60-ratifications-bbnj-agreement-to-enter-into-force-in-january-2026/