The role of shipping capacity and maritime regulation in ocean liming deployment

<title>Abstract</title> <p>Ocean alkalinity enhancement (OAE), including ship-based ocean liming, has attracted attention as a potentially scalable carbon dioxide removal (CDR) method. OAE must therefore be represented in Integrated Assessment Models (IAMs) for long-term climate projection, especially in overshoot analysis. In this work, we present the implementation of ocean liming in the WITCH IAM, which integrates a detailed international shipping module, enabling explicit modeling of increased demand for advanced low-carbon engine technologies and fuels, and linking ocean liming to available port capacity. Our results indicate that under a stringent mitigation scenario with constrained shipping availability, ocean liming could reach 1 GtCO2/yr around mid century, and provide 1.7-2.9 GtCO2/yr of removals late in the century, corresponding to 9-15% of the total CDR portfolio. We find that deployment strongly depends on regulations about allowed sea areas and on the availability of low-carbon fuels in the long term.</p>