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Comment by mikewarot | Hacker News Reader

>Think of all the fusion powered direct air CO2 capture we could have <3

Oh, trees? ;-)

This popped up on HN reasonably recently https://caseyhandmer.wordpress.com/2021/05/04/so-you-want-to... - basically "it's not necessarily as simple as that, where are you getting the water from?".

Is this still an issue when fusion power is available?

No, but the parent to my comment implied trees as being the source of that fusion power. Nobody's going to be able to use trees to power the desalination plants that allow us to irrigate the land so that we can grow those trees.

People have been growing coppice forests with salt tolerant trees such as willow for ages. No need to desalinate, the trees do it themselves. You can also use algae, which can grow in salt water.

The fusion energy that is powering the system is that of our sun. No perpetual motion machine required, our planet is being bathed in outside energy.

For a tree to be an effective long-term sequestered of carbon, you have to ensure the tree never burns or decays. Obviously this can be done; you can sink it in anaerobic water or bury it deep in a mineshaft... but just letting forests grow wild doesn't get the job done anymore. Not since the end of the Carboniferous era. New forests don't make new coal deposits, that's a thing of the past.

Trees are still great though, for innumerable other reasons.

Left to their own, trees will grow, die, fall over, and build up soil. The soil is carbon sink. You just have to keep it from eroding.

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