Seaweed along coastlines already captures an estimated 173 million metric tons of CO2 each year as it grows; some of that seaweed eventually sinks, trapping the carbon at the bottom of the ocean. Phykos wants to replicate the same process in the open ocean, where kelp doesn’t grow, to vastly increase seaweed’s global level of carbon sequestration. “Seaweeds have evolved to grow crazy fast and are fantastic at drawing out CO2,” Julian says. “Essentially what we’re just doing is giving them a bigger surface area, out in the open ocean, to do their same magic.” It could be a meaningful part of a larger carbon removal industry, he argues, which some experts have calculated will have to be as large as the oil and gas industry by the middle of the century.

The tech is modular: with the units that float on the surface, each the size of a small boat, and the lines of kelp underneath roughly the size of a single-family house. After seaweed “starts” from nurseries are planted on the lines, the vessels will navigate out to the open ocean. Software on each vessel is designed to steer toward the best areas for growth, moving throughout the year, and to automatically avoid areas like shipping lanes. Then it will harvest itself. “The seaweeds will grow and periodically get a haircut, so to speak, with an integrated harvest clipper mechanism,” says Julian. Unlike some types of kelp that float—picture the seaweed along California coastlines, which has small, round air-filled pockets to keep it near the surface—the company plans to work with species that naturally sink. A scale built into the platform will weigh the seaweed after each harvest to help calculate how much carbon has been captured….”