Governing onboard carbon capture residues: a precautionary framework for sea disposal of calcium-looping by-products

The accelerating push for decarbonization within the maritime industry has spurred considerable innovation, and the emergence of onboard carbon capture and storage (OCCS) represents a potentially significant, albeit transitional, step. While various carbon capture technologies are being explored, the calcium looping (CaL)-inspired approach, which mineralizes captured CO2 into calcium carbonate (CaCO3) residues, presents a unique regulatory challenge. As highlighted in a recent study examining governance under the MARPOL and London Convention/Protocol frameworks, simply treating these residues as ordinary waste is insufficient. IMO Council Reaffirms Commitment To Freedom Of Navigation And Seafarer Safety underscores the ongoing international effort to address maritime environmental concerns, and this new research adds a crucial layer of complexity to that effort. The potential for these solid or slurry materials to impact marine ecosystems, coupled with the carbon accounting implications of their creation and potential disposal, necessitates a far more nuanced approach than current regulations allow. This is further complicated by the disparities in marine science education and support, as evidenced by our article on Women in marine sciences in India: progress or disparity?, which demonstrates that addressing complexities within the field requires broad participation and diverse perspectives.

The study’s identification of four interconnected governance gaps – carbon-crediting and traceability, regulatory fit, environmental thresholds, and institutional responsibility – is particularly valuable. The inherent ambiguity surrounding the classification of these CaL residues, whether as dry solids, wet slurry, or dewatered filter cake, creates a significant hurdle for policymakers. The authors rightly point out that intentional release to seawater could trigger precautionary logic akin to geoengineering activities, demanding rigorous assessment and oversight. The proposed staged framework, prioritizing legal classification and emphasizing auditable custody transfer, is a pragmatic starting point. Limiting marine placement to carefully controlled research pathways, subject to independent review, reflects a responsible approach to this emerging technology. The recognition of current port-reception capacity limitations is also crucial; relying solely on port infrastructure for residue disposal is unrealistic in the short term and demands innovative solutions, potentially involving temporary onboard storage or alternative processing methods.

The broader significance of this research extends beyond the immediate regulatory challenges posed by CaL-inspired OCCS. It exemplifies the shift towards a more sophisticated understanding of carbon capture technologies and their lifecycle implications. As we move beyond the initial wave of enthusiasm for carbon capture, the need for robust governance frameworks that address the full spectrum of environmental and operational risks becomes increasingly apparent. The study’s focus on translating emerging risks into practical governance recommendations is commendable, directly contributing to the development of future IMO rule-making and port-state implementation strategies. Furthermore, the need for a holistic approach to marine resource management, encompassing not just emissions reduction but also the potential impacts of new technologies, aligns with a broader movement towards ocean intelligence and sustainable practices – principles central to the World Data Ocean mission. The “fun schools” discussed in What are some Fun Schools for Marine Science? highlight the growing interest in these areas, indicating a bright future for the field.

Looking ahead, the question remains: how can we effectively balance the urgent need to decarbonize maritime shipping with the imperative to protect marine ecosystems? The authors’ precautionary framework provides a valuable roadmap, but its implementation will require ongoing collaboration between researchers, policymakers, and industry stakeholders. The development of standardized methodologies for assessing the environmental impacts of CaL residues, alongside the establishment of clear protocols for custody transfer and disposal, will be essential for ensuring the responsible deployment of OCCS technology. The long-term success of OCCS will hinge not only on its technical feasibility but also on our ability to govern its potential risks proactively and transparently.