Dumping alkalinity into the ocean works. The chemistry is straightforward — add dissolved minerals, shift the carbonate equilibrium, pull more CO₂ from the atmosphere into the water. But where you dump it might matter more than how much you dump. A new study presented at the EGU 2026 General Assembly puts hard numbers on the regional cost variation, and the spread is enormous.

The research, titled “Carbon Dioxide Removal via Ocean Alkalinity Enhancement: Uneven Costs and Optimal Regions,” models OAE deployment across different coastal environments. The core finding: geography dominates the economics. Water temperature, mixed layer depth, existing pCO₂ levels, hydrodynamic mixing patterns, and proximity to alkalinity sources all compound to create wildly different cost curves depending on where you deploy.

What makes a coastline good for OAE? Warm water (faster CO₂ equilibration with the atmosphere), strong mixing (distributes alkalinity efficiently, prevents local carbonate oversaturation), high CO₂ undersaturation (more room for additional uptake), and proximity to mineral sources (lower transport costs for the alkaline material). Tropical and subtropical coastlines with active upwelling tend to check multiple boxes.

What makes a coastline bad? Cold, stratified waters with limited air-sea gas exchange. Regions where the water is already close to carbonate saturation. Coastlines far from mineral deposits. The North Sea, for instance, presents a mixed picture — evaluations show OAE performance there depends heavily on local physical conditions that vary on surprisingly small spatial scales.

This matters because OAE is scaling now. Companies like Planetary Technologies, Vesta, and Ebb Carbon are running real-world alkalinity addition projects. Investment is flowing. But if the field deploys in the wrong locations, costs stay high, efficiency stays low, and the entire pathway gets judged on suboptimal results.

The model resolution angle is subtle but important. Coarse global models smooth out the coastal dynamics that determine OAE performance. This research uses higher-resolution coastal modeling that captures the mesoscale processes — eddies, tidal mixing, river plumes — that actually move alkalinity around after deployment. The difference between a 1° global model and a high-resolution coastal model can flip a region from “promising” to “don’t bother.”

Think of it like wind energy siting. You wouldn’t put a wind farm anywhere there’s wind — you’d site it where capacity factors are highest, grid connections are close, and permitting is feasible. OAE needs the same geographic precision. The carbon removal potential per dollar of alkalinity varies by potentially an order of magnitude between optimal and suboptimal sites.

The research doesn’t pick winners (it’s an EGU abstract, not a deployment plan). But it establishes something the field needs: a framework for comparing regions on cost-per-ton-CO₂-removed, not just theoretical alkalinity uptake. The question isn’t whether OAE works — it’s where it works well enough to compete with other CDR pathways on cost. That map is starting to come into focus.

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