this post was submitted on 05 Dec 2023
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It doesn't even do that well. Algae have short lifespans and when they decompose, the CO2 will go right back into the atmosphere. It's the same reason you can't reasonably capture CO2 with small plants like grasses, nor does the carbon inside you count as captured. The reason trees "capture CO2" is because trees live for a long time and wood decomposes very slowly, and therefore keep its carbon locked in the wood for a long time. The point of capturing carbon is you take it out of circulation for as long as possible.
There are ways to have algae capture carbon, but they are fairly involved (read: very expensive) processes whose scalability is still uncertain. Certainly not a tank in the street.
I was always under the impression that plants chemically convert CO2 and some other stuff to glucose (C6-H12-O6), right? In that case, the algae would still help, wouldnt they?
It helps if and only if the glucose stays as glucose and is not metabolized. Wood is a good application of this, as its cellulose fibers are made of glucose, in a form that is very stable and can stay locked away for a long time (especially if the tree is alive as it does not metabolize the glucose in its own wood and has anti-predation adaptations that actively guard it against other organisms). However, if the glucose decomposes, i.e. is metabolized, it is converted either directly to CO2 or into other compounds that eventually end up as CO2, essentially returning the captured carbon back to the atmosphere.
Can you plant a tree capable of capturing the same amount of CO2 as those algae in that small a space? How about "refilling" the tree if it happens to die?
Society doesn't have to lock itself to a single solution for countless varied problems. If we're talking about a long, empty walkway, or a park, then trees are a great solution. If we're talking about a small space that must be kept free of obstructions, such as a bus stop, then a sack or box of phytoplankton is much better suited.
Thousands?
I assume they mean how long many old growth forests have been growing (though even then thousands of years is on the younger end), not the time it took for trees to evolve.
What happens when we go too far and remove all CO2 from the atmosphere?
Your question isn't entirely a hypothetical - this happened at the dawn of time, when photosynthetic life forms first evolved. First, it won't ever happen again, no matter how good we get at scooping CO2 from the atmosphere. Second, the result is theoretically catastrophic for aerobic life forms, but it's also a negative feedback loop, meaning it self corrects.
Most plants would die because they rely on CO~2~ for photosynthesis.
Many sea animals would die. Oceans absorb CO~2~ which forms carbonic acid (H~2~CO~3~) in water. Oceans are slightly alkaline due to dissolved salts (bicarbonate and carbonate) and the carbonic acid from the absorption helps to create a stable pH. Many sea animals are highly adapted to a specific pH and would die if the ocean got either too acidic or too alkaline, so they are pretty doomed in either case.
Many humans would die because agriculture would collapse. Also breathing pure oxygen over a long period of time would be very bad because of oxygen toxicity. Yeah, pure oxygen is toxic for humans lol
Land animals, I'm not so sure, but I assume most of them would die too.