The State of the Science for Marine Carbon Dioxide Removal (m CDR): A Scientific Summary for Policy-Makers
- 10 jun 2025
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Since net zero greenhouse gas emissions targets have become a keystone of climate policy, there has been increasing debate about the need to complement urgently needed emission reductions with active removal of carbon dioxide from the atmosphere (termed ‘carbon dioxide removal’, CDR)This document provides a concise summary of the state of marine CDR (mCDR) science, with a focus on those methods that are currently being most actively researched.These include mCDR options that aim to enhance the biological carbon pump: microalgal ocean fertilization, biomass (macroalgae and crop-waste) sinking, artificial upwelling and mCDR options that aim at increasing the chemical carbon sink: ocean alkalinity enhancement and direct ocean removal (also termed ‘direct ocean capture’ and ‘direct water removal’).
KEY MESSAGES
• Due to the insufficient rate of emission reductions, there is increasing interest in exploring the potential for carbon dioxide removal in marine environments.
• Marine carbon dioxide removal (mCDR) approaches are still in the early stages of development; many knowledge gaps and uncertainties remain.
• Each mCDR approach comes with trade-offs in terms of durability, energy demand and environmental impact,and would require large ocean areas if considered for large-scale implementation.
• A key challenge is to enhance technical and regulatory monitoring, reporting and verification (MRV) capacities for marine interventions.
• Future implementation of any and all mCDR approaches will require site-specific assessments, robust regulatory frameworks and an approach that balances ocean protection and use.
Vivian, C., Boettcher, M., Elliot, M., Mengis, N., Merk, C., Oschlies, A., ... & Gupta, A. (2025). The State of the Science for Marine Carbon Dioxide Removal (mCDR)–A Scientific Summary for Policy-Makers.