Preprints
https://doi.org/10.5194/egusphere-2024-1824
https://doi.org/10.5194/egusphere-2024-1824
19 Jun 2024
 | 19 Jun 2024
Status: this preprint is open for discussion.

Review and syntheses: Ocean alkalinity enhancement and carbon dioxide removal through coastal enhanced silicate weathering with olivine

Luna J. J. Geerts, Astrid Hylén, and Filip J. R. Meysman

Abstract. Coastal enhanced silicate weathering (CESW) is increasingly receiving attention as a marine-based carbon dioxide removal (CDR) technology. The method aims to achieve ocean alkalinity enhancement (OAE) by introducing fast-weathering silicate minerals into coastal systems. The latter is envisioned to act as a large natural biogeochemical reactor, where ambient physical and biological processes can stimulate silicate dissolution, thus generating a concomitant alkalinity release and increasing the seawater’s capacity to sequester CO2. Olivine has been forwarded as the prime candidate mineral for CESW, but to the present, no results from larger-scale field studies in actual coastal systems are available, so all information is exclusively derived from idealized laboratory experiments. As a result, key uncertainties remain concerning the efficiency, CO2 sequestration potential, and impact of olivine-based CESW under relevant field conditions. In this review, we summarize recent research advancements to bridge the gap between existing laboratory results and the real-world environment in which CESW is intended to take place. To this end, we identify the key parameters that govern the dissolution kinetics of olivine in coastal sediments, and the associated CO2 sequestration potential, which enable us to identify a number of uncertainties that are outstanding with respect to the implementation and upscaling of olivine-based CESW, as well as the monitoring, reporting, and verification (MRV). From our analysis, we conclude that the current knowledge base is not sufficient to predict the outcome of in situ CESW applications. Particularly, the impact of pore water saturation on the olivine dissolution rate and the question of the additionality of alkalinity generation remain critical unknowns. To more confidently assess the potential and impact of olivine-based CESW, dedicated pilot studies under filed conditions are needed, which should be conducted at a sufficiently large spatial scale and monitored for a long enough time with sufficient temporal resolution. Additionally, our analysis indicates that the specific sediment type of the application site (e.g. cohesive versus permeable) will be a critical factor for olivine-based CESW applications, as it will significantly impact the dissolution rate by influencing the ambient pore water pH, saturation dynamics, and natural alkalinity generation. Therefore, future field studies should also target different coastal sediment types.

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Luna J. J. Geerts, Astrid Hylén, and Filip J. R. Meysman

Status: open (until 31 Jul 2024)

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  • RC1: 'Comment on egusphere-2024-1824', Anonymous Referee #1, 12 Jul 2024 reply
Luna J. J. Geerts, Astrid Hylén, and Filip J. R. Meysman
Luna J. J. Geerts, Astrid Hylén, and Filip J. R. Meysman

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Short summary
Coastal enhanced silicate weathering (CESW) with olivine is a promising method for capturing CO2 from the atmosphere, yet studies in field conditions are lacking. We bridge the gap between theoretical studies and the real-world environment by estimating the predictability of CESW parameters and identifying aspects to consider when applying CESW. A major source of uncertainty is the lack of experimental studies with sediment, which can heavily influence the speed and efficiency of CO2 drawdown.