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New research demonstrates effective carbon removal with alkalinity enhancement.

Updated: Nov 8, 2023

Researchers at the University of Miami publish a study in Marine Chemistry calculating global projections for ocean alkalinity enhancement.

Published on June 7, the study was conducted at the Rosenstiel School of Marine and Atmospheric Science. The researchers tested the reaction rate of magnesium hydroxide alkalinity when added to a tank of seawater. The 9,000 gallon tank is equipped with fans and pumps capable of reaching hurricane force wind and waves. They used these capabilities to create a realistic ocean mixing scenario mimicking the release of alkalinity at a test site.


Ocean alkalinity enhancement (OAE) is an emerging technology to increase the ocean's buffer capacity and store additional carbon from the atmosphere. Alkalinity refers to water’s ability to neutralize acid. When alkaline molecules react with carbon dioxide, it converts to a form that can’t readily return to the atmosphere as CO2 gas. OAE artificially adds minerals to the ocean like olivine, lime, and basalt, or a synthetic equivalent, to remove legacy carbon emissions and combat ocean acidification.


The results of the experiment showed stable enhanced alkalinity without precipitation (undissolved solid) and at an efficiency rate consistent with the theoretical maximum carbon capture. Efficiency favors lower initial dissolve inorganic carbon (DIC) to total alkalinity (TA) ratio, lower temperature, and high atmospheric CO2. Based on these findings the researchers created global projections for uptake of CO2 if OAE were implemented globally at the ocean's surface. They calculated that adding 175 μmol kg−1 Mg(OH)2 to the top 10 m of the ocean, can remove about 44 Gt of CO2.



Laura Stieghorst funded and planned the experiments on behalf of Básico as a part of her XPRIZE Carbon Removal project. The full article can be access online at https://doi.org/10.1016/j.marchem.2023.104251.


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