But also, any growing plants - you could compute for every kg of dry plant matter, how much oxygen is released, as the dry plant matter is almost entirely carbon produced from breaking up CO2.
So unless you're collecting tens or hundreds of kilograms of dead plants from your roof every year, it isn't producing much oxygen.
This is why we won't solve climate change by simply planting trees. Planting trees is good but once the land is covered in trees like it was you can't go further. You have to start actively putting carbon underground so it doesn't end up in the air again.
Well, you can build shit with the wood that's going to last a long time and plant a new tree. Though I'm not sure the lumber processing & construction isn't producing more carbon than the tree sequesters...
Googling "are algae plants?", gives this as the first answer:
> Algae are in the plant kingdom, but technically they are not plants. ... Algae range in size from microscopic to meters long and from single-celled to complex organisms that rival large plants. These organisms may look like true plants, but unlike plants, algae do not have roots or true stems and leaves.
Either way, I wasn't thinking of algae or aware that they might be net oxygen producers for the atmosphere.
But also, any growing plants - you could compute for every kg of dry plant matter, how much oxygen is released, as the dry plant matter is almost entirely carbon produced from breaking up CO2.
So unless you're collecting tens or hundreds of kilograms of dead plants from your roof every year, it isn't producing much oxygen.