The International Maritime Organization (IMO) has adopted new assessment frameworks to guide research into marine carbon dioxide removal (mCDR). This establishes a structured approach to evaluating ocean-based climate solutions. This decision was made during the 48th Consultative Meeting of the Parties to the 1972 London Convention and the 21st Meeting of the Parties to the 1996 London Protocol, which took place in London from 5 to 9 October 2026. These frameworks will assist governments in the evaluation of proposed research activities, the identification of potential risks, and the determination of whether projects can proceed without causing unacceptable harm to marine ecosystems.
Marine carbon removal is receiving increasing attention as countries and companies seek to address climate change. While reducing GHG emissions remains essential, removing CO2 already present in the atmosphere is also seen as important for achieving long-term climate goals. The ocean plays a significant role in the global carbon cycle, presenting opportunities for technologies that could enhance its ability to absorb or store CO2. However, the environmental consequences of these approaches are not yet clear, so more scientific research is needed.
Three marine CDR methods under assessment
Three marine geoengineering techniques are covered by the newly adopted frameworks: ocean fertilization, ocean alkalinity enhancement (OAE) and ocean sinking of biomass. Each approach seeks to increase carbon uptake or storage through different processes.
- Ocean fertilization: adding nutrients to seawater stimulates phytoplankton growth, microscopic organisms that absorb CO2 through photosynthesis. The goal is to enhance biological productivity and possibly move more carbon into deeper ocean waters. However, researchers still need to determine this method's long-term effectiveness for carbon storage and understand its broader ecological impacts.
- Ocean alkalinity enhancement (OAE): is the process of adding alkaline substances to seawater to increase its capacity to absorb atmospheric CO2. This approach could help counteract ocean acidification, as well as offering the potential to remove carbon. Further research is required to understand the effects of introducing these substances and to determine whether the resulting carbon storage can be reliably measured.
- Ocean sinking of biomass: it refers to the deliberate placement of biological material, such as marine or terrestrial plant matter, into the ocean for carbon storage. The effectiveness of this method depends on how much carbon remains stored over time and whether the process has any harmful effects on marine ecosystems.
Under the frameworks, governments will evaluate proposals on a case-by-case basis. This will be through a process covering initial screening, environmental assessments, risk management, decision-making, and post-project reviews. Proposals must demonstrate a legitimate scientific purpose, undergo appropriate peer review, and include stakeholder consultations. They must also establish monitoring and transparent reporting procedures. Assessments can also be updated as new scientific evidence emerges.
The IMO Secretary-General, Arsenio Dominguez, welcomed the decision, noting that the frameworks offer regulators and researchers rigorous and transparent tools for evaluating proposed activities. Ocean Conservancy also supported the adoption, emphasizing the need for credible scientific evidence, effective governance, and meaningful community engagement as the development of marine carbon removal progresses.
Implications for Carbon Markets and CDR
Adopting these frameworks is an important step in establishing clearer rules for marine carbon removal research. The IMO and the parties to the London Convention and London Protocol are working together to create a common assessment process. This aims to prevent unreliable experiments and ensure that research is conducted responsibly.
However, the decision also places significant restrictions on the sector's short-term development. The parties emphasized that scientific understanding remains limited, and that activities beyond the research stage cannot currently be considered under the frameworks. Therefore, the adoption of these frameworks should not be interpreted as approval for the deployment of commercial-scale marine carbon removal.
These requirements could also influence the emerging market for ocean-based carbon removal credits. Projects looking to generate and sell these credits may struggle to demonstrate their scientific legitimacy, environmental integrity, and the reliability of their long-term carbon storage. Environmental organizations, including the Center for International Environmental Law, have argued that projects designed mainly to generate or sell carbon offsets may not qualify as legitimate scientific research. Payments for services directly linked to experimental trials may be treated differently, depending on the rules that apply and how they are understood.
A key point to note is that the frameworks address marine geoengineering in surface waters and the water column. These operate independently of the regulatory arrangements applicable to offshore carbon capture and storage in geological formations beneath the seabed.
In summary, the IMO's decision establishes a basis for more responsible research into marine carbon removal. While these technologies could eventually contribute to climate mitigation, their future development relies on demonstrating measurable carbon removal, understanding their long-term effects, and establishing clear regulatory pathways.
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