Ocean Alkalinity Enhancement: Tool to Mitigate Climate Change — Thesis

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https://portal.findresearcher.sdu.dk/en/publications/ocean-alkalinity-enhancement-tool-to-mitigate-climate-change

Authors 

Jakob Bang Rønning

Published - 1 March 2024

10.21996/p2f3-rp88

Abstract

In the face of climate change challenges, characterized by rising atmospheric carbon dioxide (CO2) concentrations and the consequential threats of approaching climate tipping points, including sea level rise, more wildfires, and escalating heatwaves, there exists a pressing need to explore effective strategies to mitigate these CO2-related issues. This thesis explores the potential of ocean alkalinity enhancement (OAE) as an ocean-based carbon dioxide removal (CDR) method, specifically focusing on alkaline minerals for mineral-based OAE as novel avenues for climate change mitigation. As global decarbonization is obliged, integrating diverse CDR technologies is essential to effectively counter and reverse the ongoing trend of global CO2 emissions in the atmosphere.

This thesis studied the nuanced aspects of mineral-based OAE, emphasizing the potential of alkaline minerals such as dolomite, limestone, and olivine. The study aims to examine their impact on seawater carbon chemistry and primary producers. With the focus on different solid/liquid distributions in different aquatic environments, dissolution and investigate the importance of grain size. Manuscript I revealed the influence of olivine, dolomite, calcite, chalk, and limestone on seawater carbon chemistry, demonstrating their potential to mitigate ocean acidification. The results showed a high of increase of olivine and potentially dolomite to increase and stabilize seawater pH. In contrast, calcium-based minerals regularly lead to opposite effects, reducing the pH. Alkalinity was increased by olivine additions but not by dolomite and the other calcium minerals. Manuscript II findings disclose minimal negative impact on primary producers from olivine additions. Additionally, the olivine additions elevated nickel concentrations, but the exposure did not seem to have a harmful effect. Manuscript III investigated olivine on a larger scale with a flume setup; the experiment explores olivine weathering across varying salinities and demonstrates increased dissolved inorganic carbon alkalinity and pH. Generally, the brackish and partially freshwater scenarios exhibit favorable outcomes in response to olivine additions. These initial findings suggest that river or fjord environments with lower salinity may provide an advantageous setting for olivine dissolution, advancing the prospect of river alkalinity enhancement. Manuscript IV provides an overarching

perspective on OAE methods, including mineral additions. It discusses each method's technical aspects and implications, acknowledging the importance of considering regional conditions, scalability, and environmental impacts. This thesis offers valuable insights into mineral-based OAE and considers how to develop and effectively deploy OAE approaches to mitigate CO2.

Source: SDU