Articles | Volume 21, issue 1
Research article
 | Highlight paper
16 Jan 2024
Research article | Highlight paper |  | 16 Jan 2024

The additionality problem of ocean alkalinity enhancement

Lennart Thomas Bach

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Monitoring, reporting, and verification for ocean alkalinity enhancement
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Cited articles

Adkins, J. F., Naviaux, J. D., Subhas, A. V, Dong, S., and Berelson, W. M.: The Dissolution Rate of CaCO_3 in the Ocean, Annu. Rev. Mar. Sci., 13, 57–80,, 2020. 
Aller, R. C.: Carbonate Dissolution in Nearshore Terrigenous Muds: The Role of Physical and Biological Reworking, J. Geol., 90, 79–95,, 1982. 
Archer, D., Kheshgi, H., and Maier-Reimer, E.: Dynamics of fossil fuel CO2 neutralization by marine CaCO_3, Global Biogeochem. Cy., 12, 259–276,, 1998. 
Bach, L. T.: The additionality problem of Ocean Alkalinity Enhancement: Underlying experimental and observational data, Zenodo [data set],, 2023. 
Reaching the Paris Agreement targets to limit global warming to 1.5 or 2°C implies not only reducing emissions, but also active carbon dioxide removal from the atmosphere. While land-based carbon dioxide removal or negative emission technologies have received most attention, ocean solutions are increasingly being considered. Ocean alkalinity enhancement (OAE), or alkalinization, is one promising ocean-based carbon dioxide technology. However, any new carbon dioxide removal technique needs thorough investigations for its effectiveness, longevity, benefits and lack of disbenefits, financial viability, social acceptance and governability. The paper by Bach is a nice illustration of the type of research that must be done if we are to consider large scale application of OAE. It focuses on the additionality problem of ocean alkalinity enhancement, specifically it investigates how the addition of alkalinity modifies the natural alkalinity cycle and in that way the efficiency of carbon dioxide sequestration.
Short summary
Ocean alkalinity enhancement (OAE) is a widely considered marine carbon dioxide removal method. OAE aims to accelerate chemical rock weathering, which is a natural process that slowly sequesters atmospheric carbon dioxide. This study shows that the addition of anthropogenic alkalinity via OAE can reduce the natural release of alkalinity and, therefore, reduce the efficiency of OAE for climate mitigation. However, the additionality problem could be mitigated via a variety of activities.
Final-revised paper