OAE Monitoring, Reporting, and Verification (MRV)
The underlying science of OAE and its high potential for carbon removal is well understood and recognized by leading scientific bodies such as The National Academies.
Decades of oceanographic research, including lab and mesocosm studies, confirm that increasing ocean alkalinity leads to durable carbon dioxide removal (CDR) (2023, He and Tyka). By slightly raising surface alkalinity, dissolved CO₂ is shifted to a different form and stored as dissolved inorganic carbon (DIC) in seawater, allowing the ocean to absorb more CO₂ from the air.
However, resulting carbon removal from OAE can vary greatly due to physical, biological, and chemical processes in the ocean. Understanding exactly how these factors influence CDR has been a major focus of research for years and is often referred to as the “efficiency rate” (2017, Renforth and Hendersonl; 2023, He and Tyka; 2024, Bach).
New research on drivers of efficiency and real-world prototypes of OAE now allow increased focus on the frameworks needed to rigorously and transparently quantify the amount of carbon removed.
These frameworks are known as MRV.
MRV in Carbon Markets
The framework used to accurately determine the amount of CO₂ that has been durably removed by CDR, with transparent reporting and independent verification, is called monitoring, reporting, and verification (MRV). MRV is critical to building trust in carbon removal techniques, enhancing the integrity of carbon credit markets by ensuring that CDR claims and environmental safety criteria are met.
MRV helps governments, businesses, and civil society to assess whether a given CDR project has achieved its claims and thus fulfilled the conditions of a given CDR standard’s methodology document, resulting in CO₂ being stored durably and safely.
From “Towards improved cost estimates for monitoring, reporting, and verification of carbon dioxide removal” by Mercer et al, 2024.
The ABC’s of MRV
M: Monitoring
In the context of ocean-based CDR, monitoring includes the combination of direct measurements and predictive models that quantify carbon removal across the ocean over time.
In addition to monitoring efforts to support CDR quantification, additional measurements for environmental impacts help meet permitting requirements and community interests.
R: Reporting
Reporting data from a project serves two purposes. First, providing auditable information for the verification of carbon credits in voluntary and compliance markets, including any emissions caused during a project’s life cycle.
Second, data is often shared with regulatory bodies, investors, or members of the public such as researchers to build trust and accountability.
V: Verification
The final step in the MRV framework involves verification of the reported data through an independent third party in order to validate accuracy.
This is an essential layer that increases trust and credibility by confirming the amount of CDR that has occurred and therefore that carbon credits can be issued within a marketplace or national procurement programs.
Closed-system and Open-system CDR
The CDR community distinguishes between closed-system and open-system CDR.
Closed-system CDR, including Direct Air Capture (DAC), relies on fully engineered processes to convert atmospheric CO2 into a directly measurable stream of CO2. The extracted CO2 must be enclosed in long-lived products (the production of fuel, for example, would not qualify) or durably stored and monitored in order to qualify as carbon removal for crediting. Because many of the steps in a closed-system pathway are directly controlled or engineered, they are easier to monitor and more straightforward to quantify but demand energy input for every moving molecule. Its potential to scale may be limited to a Megatonne level (European Scientific Advisory Board on Climate Change, 2025).
Open-system CDR, including reforestation, OAE, and Enhanced Rock Weathering (ERW), leverages natural processes happening in diffuse, open environments to absorb and sequester atmospheric CO2. Through mimicking, accelerating, or enhancing different natural carbon storage methods, these pathways rely on nature to complete the removal process. They do not require energy input for every step of the process and have the potential to scale to Gigatonne level. However, the development of new monitoring approaches is needed to accurately quantify the amount of CDR that results (NASEM, 2022).
Applying MRV to OAE
Quantifying CO₂ removal via ocean alkalinity enhancement requires both direct measurements and models informed by empirical data.
Measurements detail the biological, physical, and chemical properties of an ocean area and can detect shifts in carbonate chemistry (by measuring factors such as the total alkalinity, pH, and dissolved CO₂) as alkalinity is added to seawater. Calibrated with these observations, regional models simulate how measured changes propagate over space and time.
Together, models and measurements provide an integrated framework for assessing both the immediate and long-term impact of OAE in removing atmospheric CO₂ and durably storing it as dissolved inorganic carbon.
Monitoring, reporting, and verification are essential to closing information gaps and asymmetries between public and private sectors, managing the risks and opportunities of removals, and to informing policies with evidence from projects.
From “Scaling up carbon dioxide removals – Recommendations for navigating opportunities and risks” by the European Scientific Advisory Board on Climate Change.
What comes next?
Early OAE research efforts allow testing of the first MRV frameworks. As a result, scientists can gain real-world evidence about the quantification of OAE. Over time, MRV frameworks for OAE will improve based on an increasing body of evidence and confidence around key processes to measure and model. The focus of upcoming research efforts is to improve model reliability, measurement performance, and their integration to reduce uncertainty.
Carbon to Sea supports the assessment of models and measurements and joint learning through field research. Simultaneously, we are laying the groundwork for components of future MRV frameworks through data standards and environmental impact guidelines.
You can learn more about key insights and recent progress on MRV in an upcoming blog series.
