Macroalgae cultivation and sinking

Macroalgae cultivation and sinking is a form of biotic marine carbon dioxide removal (mCDR).

Currently, seaweed is cultivated for use in human food products, animal feeds, fertilizer, and other productive uses. To count as carbon removal, the carbon sequestered by seaweed via photosynthesis must be locked away somewhere where those carbon molecules cannot re-enter the atmosphere for at least hundreds of years. The most cost effective and scalable use of seaweed as a carbon dioxide removal technique would be to simply cultivate large amounts of seaweed and sink it directly to the ocean floor. 

This method is in the research stage currently, and is not yet implemented at scale as a climate solution.