Marine CO2 Removal Research: New Studies Map What Works, What's Uncertain, and What Needs to Scale

A new collection of eleven studies in Frontiers in Environmental Engineering assesses marine carbon dioxide removal (mCDR) methods such as ocean alkalinity enhancement, direct ocean capture, iron fertilization, and macroalgae cultivation. The research covers engineering performance, monitoring challenges, environmental risks, and costs. It does not claim these methods are ready to scale; instead it outlines the gaps in durability, verification, and governance that remain before any method can be considered viable for carbon crediting. Key findings include the need for at least 100 years of carbon isolation, the limits of current pH sensors for verifying alkalinity addition, and the influence of local ocean currents on project effectiveness. One techno-economic analysis finds large cost uncertainty driven by weak oceanographic data. The overall message is that better science and better monitoring are prerequisites for responsible mCDR deployment, not optional extras.