I think the idea seems to be that this uses algae, which "eats" the carbon.
Assuming that's right, then like any other plant-based carbon absorption method, it matters what happens later, whether the carbon is released back into the atmosphere in some form during decomposition, or if it's buried, or whatever else.
Assuming that's right, then like any other plant-based carbon absorption method, it matters what happens later, whether the carbon is released back into the atmosphere in some form during decomposition, or if it's buried, or whatever else.