[ivankirigin]

Biomass that falls into the deep ocean doesn't quickly cycle back into the carbon cycle, so some companies are look at the opposite, with the deep ocean as a sink. https://www.phykos.co/

But your idea is somewhat correct, and it has to do with desalinization tailings. There are companies like Heimdal which can take the high mineral runoff from desalinization and use it to make concrete. https://www.ycombinator.com/companies/heimdal