The question I couldn’t drop
In conversations about deploying electrochemical marine carbon dioxide removal (e‑mCDR) at scale, we’ve often emphasized co‑location with existing coastal infrastructure, because the logic is genuinely strong: seawater intake and outfalls already exist, and e-mCDR scale is fundamentally a throughput story.
But the thing that kept bothering me wasn’t whether co-location helps, it was whether we were being too hand-wavy about where to do it, as if all coastlines are interchangeable.
So, the core question became: if you had limited capital and had to pick early deployment regions, which U.S. coastal hubs actually offer the best combination of removal potential, affordability, grid characteristics, and “real-world buildability”?
The dataset reality check
We built the analysis around 38 coastal facilities with seawater intake (power plants, desalination plants, and LNG terminals) because the CO2 removal capacity depends on seawater intake capacity, and that gives you a consistent way to compare sites.
In practice, that meant saying “no” to a lot of candidate sites that didn’t have reported intake data, even if they looked promising on a map, because we didn’t want to invent numbers or lean on assumptions that would quietly bias the results.
We also pulled in regional features tied to deployment reality such as, electricity costs and grid emissions factors, plus environmental/social context indicators (local carbon footprint and social vulnerability index). This way, the ranking wouldn’t just be “who can pump the most water.”
From facilities to “hubs”
We grouped facilities into five geographically defined hubs (Northeast, Southeast, South, West, and Northwest) using hierarchical clustering and then mapped hub boundaries.
Seeing the hubs on a single map made the deployment question feel real: you’re no longer debating “the U.S. coastline,” you’re debating a handful of concrete clusters with different facility mixes.
Figure 1. Geographical Distribution, Clustering, and Composition of Coastal e-mCDR Hubs. (A) Geographical distribution of 38 coastal facilities identified as potential colocation sites for e-mCDR deployment along the U.S. coastline. Facilities are distributed relatively uniformly, with clusters forming near major metropolitan areas. The three facility types included power plants (●), desalination plants (▲), and LNG terminals (■). (B) Identified e-mCDR hubs and facility composition. Each hub's composition is represented by a pie chart indicating the percentage distribution of power plants, desalination plants, and LNG terminals within the hub.
How the hubs ranked
After scoring each hub across seven practical criteria (CO2 removal capacity, removal affordability, grid emissions efficiency, social vulnerability index, local carbon footprint, facility diversity index, and hydrogen management infrastructure), we used AHP to decide how much each criterion should count and TOPSIS to roll everything into one overall “how good is this hub for deployment?” score (the closeness score C, where values closer to 1 are better).
That’s what the rankings entail: not “who has the most seawater intake” or “who has the cleanest grid,” but which hub looks best when you consider deployment as a bundle of technical, economic, infrastructure, and context constraints.
The South hub ranked #1 overall (C=0.6), with West and Northeast tied next (C=0.52), followed by Southeast (C=0.43) and Northwest (C=0.24). It’s more useful to think in tiers than a strict 1-to-5 list: West/South/Northeast are “high potential,” Southeast is “moderate potential,” and Northwest is “low potential” under the chosen criteria and weighting.
What that ranking means in practice is that each top hub wins for a different reason, and the “best” hub is the one that stacks enough strengths at once.
- South: Ranked highest mainly because it performs strongly across multiple criteria, especially removal affordability, hydrogen management infrastructure, local carbon footprint, and facility diversity, even though it has the lowest CO2 removal capacity due to lower seawater intake.
- West: Ranked highly because it leads on CO2 removal capacity and scores well on grid emissions efficiency and hydrogen management infrastructure, but it is held back by lower removal affordability (higher electricity cost) and low facility diversity.
- Northeast: Ranked highly because it performs well on CO2 removal capacity and grid emissions efficiency, but it is constrained by low facility diversity (power plants dominate its intake).
One more nuance the results imply: the top three hubs are close enough that small shifts in what you value (i.e., changing criterion weights) can reshuffle the order, which is why the study also emphasizes sensitivity analysis rather than treating the ranking as absolute.
What comes next
In the future, we want to move beyond “what looks best on paper” and pressure-test these hub rankings with the people who would actually host and operate e‑mCDR systems (i.e., facility owners/operators, regulators, and nearby communities), so we can capture practical barriers like permitting timelines, retrofit constraints, and workforce needs.
We also plan to extend the framework by adding more deployment-realism inputs (for example, more detailed cost and lifecycle assessments and clearer regulatory considerations), so the rankings remain useful as the technology scales and policy evolves.