The additionality problem of ocean alkalinity enhancement

Abstract 2 sequestration relative to a baseline state without OAE. This so-called “additionality” can be calculated as follows: Additionality = C OAE - Δ C baseline. So far, feasibility studies on OAE have mainly focussed on enhancing alkalinity in the oceans to stimulate CO2 sequestration (C OAE); however, the primary focus has not been on how such anthropogenic alkalinity would modify the natural alkalinity cycle and associated baseline CO2 sequestration (Δ C baseline). Here, I present incubation experiments in which materials considered for OAE (sodium hydroxide, steel slag, and olivine) are exposed to beach sand to investigate the influence of anthropogenic alkalinity on natural alkalinity sources and sinks. The experiments show that anthropogenic alkalinity can strongly reduce the generation of natural alkalinity, thereby reducing additionality. This is because the anthropogenic alkalinity increases the calcium carbonate saturation state, which reduces the dissolution of calcium carbonate from sand, a natural alkalinity source. I argue that this “additionality problem” of OAE is potentially widespread and applies to many marine systems where OAE implementation is considered – far beyond the beach scenario investigated in this study. However, the problem can potentially be mitigated by dilute dosing of anthropogenic alkalinity into the ocean environment and the avoidance of OAE in natural alkalinity cycling hotspots, such as in marine sediments. Understanding a potential slowdown of the natural alkalinity cycle through the introduction of an anthropogenic alkalinity cycle will be crucial for the assessment of OAE.

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch

References and Relationships

• Bibliographic citation: The additionality problem of ocean alkalinity enhancement ; volume:21 ; number:1 ; year:2024 ; pages:261-277 ; extent:17 ; Biogeosciences ; 21, Heft 1 (2024), 261-277 (gesamt 17)

Contributors, Places and Time

• Creator: Bach, Lennart Thomas

Further information

• DOI: 10.5194/bg-21-261-2024
• URN: urn:nbn:de:101:1-2024011803150441510296
• Rights: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 15.08.2025, 7:22 AM CEST