Inside the bold, quixotic quest to store planet-warming carbon in the ocean

Scientific American · Alec Luhn · 2026-10-20 10:00 UTC

These start-ups are trying to suck CO2 from the air and stash it in the sea. Is it working?

On a drizzly morning in March 2025, a bright blue dive boat motored through Halifax Harbor in Nova Scotia toward the Tufts Cove generating station. The boat rumbled past the power plant’s three smokestacks, striped red and white like candy canes, to a yellow buoy bobbing in the waves.

Canadian company Planetary Technologies had been adding an alkaline slurry to the generating station’s cooling water before it rushed through a concrete tunnel and into the harbor near the buoy. The added alkalinity is meant to shift dissolved carbon dioxide into more stable forms, drawing more of the gas out of the air. The question was how much.

The captain thrummed the engine to steady the vessel against the incoming tide. Dalhousie University oceanographer Dariia Atamanchuk lowered the team’s “carbon cage,” a rectangular frame of wires and sensors, into the blue-green waves and checked the water’s CO₂ concentration on her laptop. “It is just slightly below atmospheric,” she said.

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