Targeted interventions in marine chemistry
WOR 8 The Ocean – A Climate Champion? How to Boost Marine Carbon Dioxide Uptake | 2024

Targeted interventions in marine chemistry

Targeted interventions in marine chemistry
> Complex processes allow the ocean to absorb carbon dioxide from the atmosphere, chemically bind much of the carbon it contains, and store this carbon in its water masses. However, the more carbon dioxide the sea absorbs, the more acidified its waters become. This process could be reversed through a targeted boost of its natural acid-binding capacity. As yet, however, little is known about the impacts that could result.
Alkalinity enhancement – an approach in its infancy fig. 7.4: Aaron Takeo Ninokawa of UC Davis

Alkalinity enhancement – an approach in its infancy

> The amount of carbon dioxide the ocean can absorb without substantially acidifying depends on the alkalinity of its surface waters. This term refers to the amount of acid-binding mineral components that were previously dissolved by the weathering of rocks and discharged into the sea. This then raises the question: Could a deliberate input of minerals help to increase the ocean’s carbon dioxide uptake without disrupting its chemistry and life in the ocean?

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Alkalinity enhancement – understood in theory but insufficiently tested in the field

Mineral-rich dissolution products from the natural weathering of rocks enable the chemical bonding of dissolved carbon dioxide in the ocean, and the subsequent absorption of new carbon dioxide from the atmosphere. This natural process of climate regulation could be selectively accelerated if large amounts of limestone and silicate rocks were mined and distributed in the sea in the form of rock flour or alkaline solutions. Such alkalinity-enhancing processes would also have the benefit of reducing acidification in the treated water masses and improving the living conditions for many marine organisms.
The chemical processes involved in a targeted programme of alkalinity enhancement of the ocean are now quite well understood. Its technical feasibility, however, is difficult to assess because most of our knowledge comes from computer simulations and small-scale laboratory experiments. Large-scale field experiments are still lacking.
In the laboratory, researchers are now testing various naturally occurring and artificially produced minerals for their suitability and weathering properties. At the same time, initial studies are being carried out on the possible environmental impacts and risks, about which very little is yet known. Specialists are also working on electrochemical methods of alkalinity enhancement. These require a high input of energy but, in contrast to other methods, could be applied without the massive input of rock material.
The true potential for carbon dioxide removal using alkalinity-enhancement methods is also difficult to quantify. According to calculations, if the presently known methods were to be applied worldwide, an additional 100 million to more than a billion tonnes of carbon dioxide could be removed from the atmosphere. However, this would be countered by new greenhouse gas emissions generated in the activities of quarrying, transporting and processing the rocks. As a consequence, potential methods for targeted alkalinity enhancement in the ocean are still subject to large uncertainties.