Planetary Technologies' Groundbreaking Marine Carbon Dioxide Removal (mCDR) Project in Halifax, and the Emergence of Halifax as a Global mCDR Hub

Ocean Alkalinity Enhancement (OAE) is a marine carbon dioxide removal (mCDR) pathway that is widely accepted to be both permanent in its CO2 storage and, potentially, the most scalable pathway available today. Here, we outline the science behind OAE, and provide details of the past and present advances in the science, engineering, and community building at a worlds-first OAE field trial site in Halifax, Nova Scotia. The site is operated by Halifax-based Planetary Technologies, and the R&D work is conducted alongside numerous local and international collaborators spanning academia, philanthropic organizations, and engineering firms. While the fundamental science is relatively straightforward, the practical deployment of Planetary's end-to-end OAE process is complex and interdisciplinary, and includes the following elements: site scoping and development, the engineered mechanism of adding alkaline materials to the ocean, and the eventual generation of high-quality carbon credits. Workstreams include permitting and regulatory compliance, meaningful community engagement and governance, established protocols to ensure operational, environmental, and social safety, oceanographic sensing using traditional boat-based and novel autonomous platforms, spatiotemporal ocean modelling at scales spanning multiple orders of magnitude, and techniques for both quantifying uncertainties and applying those uncertainties to ensure high-confidence and thus high-quality credits.