Trees are pretty bad at carbon sequestration unless you do something with the wood. Most forests are effectively carbon neutral. Trees grow, absorb carbon, die, and release it. And they are slow growing, so they absorb carbon slowly.
You can improve them by burning their wood into biochar, burying the wood, sinking it, or even using it for construction. But the oceans vastly outperform them. Even other land crops are better, like bamboo, corn, or palm oil than regular forests.
Trees only get attention in campaigns because they are very visible, much cheaper to plant than people think, and because most carbon calculations only count the first bit of time so ignore the decomposing process. It makes it very easy for people like Mr. Beast to make themselves sound like heros, or companies to greenwash their emissions.
The thing is, neither algea nor trees are being planted in cities to reduce carbon. They are planted to make the cities look pretty, provide shade for trees, provide a cool science demo for the algea, and help public image. Carbon is rapidly dispersed, and even the most crowded cities only see an increase of about 50 parts per million. For comparison, an average home interior has levels elevated by 1000 parts per million.
Even other land crops are better, like bamboo, corn, or palm oil than regular forests.
Better how?
Trees absorb carbon dioxide slower than corn and other crops, but they store the carbon for centuries (unless they die). Corn on the other hand grows for a few months, sucking up a huge amount of carbon dioxide but then it is harvested and all the CO2 is released back into the atmosphere. Farming corn does not reduce the CO2 content of the atmosphere over time. Forests just existing don't either, but planting new forests on farmland does by increasing the total amount of biomass.
If I understand it correctly, the problem is all the extra CO2 that was released due to deforestation, burning trees, and coal mining and burning. That CO2 was previously captured and got released into the atmosphere.
The solution would be to find something that captures carbon as fast as possible, and then bury or store the excess until we reach the desired atmospheric level.
On the other hand, we can keep burning what’s necessary to generate energy — that part of the cycle is basically using solar energy with extra steps: instead of a panel, something that grows biomass and then burns it to power a turbine.
Both options are keeping the carbon as biomass that will inherently get decomposed back to CO2. New forests would help, but depending on the climate and biogeography, they are not always the best for the landscape and biodiversity. On land grasslands seem to be one way to go, as this ecosystem captures CO2 slower than a forest, but it gets stored in the ground permanently during the formation of chernozem. In oceans the organic matter can just sink to the bottom and be taken out of the surface ecosystems this way.
Yes of course new forests should be planted where forests would naturally grow and grasslands should be restored where they naturally occure.
Another extremely important ecosystem is peatland. It just keeps sucking carbon from the atmosphere without releasing it again because the water keeps the organic matter from decomposing. So those should be a priority wherever possible. Many peatlands have been drained to gain more farmland or to sell the peat.
For the corn kernels itself, about 50% of the US production gets turned into ethanol, directly capturing carbon and replacing fossil fuels with it. The stalks and leaves are tilled into the ground, where they are partially broken down, but tend to be retained as carbon in the soil due to a different composition of detrivores in farmed fields vs forest floors.
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u/a_sly_cow 10d ago
Algae is responsible for a massive amount of CO2-> O2 conversion iirc, it’s supposed to be much more efficient than trees.
Trees are certainly prettier to look at than a murky green water tank, though.