With the largest mass and surface, world’s oceans are largest store of carbon on earth (save the deep carbon in earth’s core, mantle and lithospheric crust). Through the process of carbonation, oceans already absorb about 30 % of all man-made CO₂ emissions every year.

Therefore, the “blue carbon capture” initially appeared promising. However, when this path was pursued further, it turned out that ocean’s absorption capacity is limited, and we can already see the negative consequences – ocean acidification from excess carbonic acid. This impacts all marine life forming shells and skeletons (corals, mollusks, and many planktons) and already disrupts several oceanic nutrient cycles. Most visible impact of this is the coral reef bleaching (reduction in carbonate ions hinders development of coral’s calcium carbonate structure).

Hence, any technology aimed at increasing CO2 absorption into oceans has a high likelihood of being harmful and truly a two-edged sword – particularly if done at scale.