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Comment by deegles | Hacker News Reader

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

When you find yourself in a hole, stop digging.

The first landmark is to make coal plants unprofitable. Once all (most of) the coal and oil plants are closed, it would be interesting to use the spare electricity for carbon capture. Otherwise you are burning coal to power the carbon capture facility.

I don't know, we might need technology to save us from our seemingly bottomless stupidity. Maybe in 2050, Robo-Joe Manchin will secure a permanent government slush fund for Greater West Virginia coal mining and we'll have to stick a fusion-powered CO2 capture facility right next to where they burn it.

Don't disagree but we are already at the stage where we have the technology to solve climate change , what we have is a problem of status quo-ism

I just don't know if we should firmly say "we have enough technology so now the only problem is how to make humans amenable to radical change". It's frustrating but maybe "more technology" is a more practical path that can still get us to the same place.

>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.

As usual, everything that is infinite meets another barrier in physics. Initial investment is the barrier for every energy plant. But I also imagine ourselves already using energy like it’s cheap, trying to illuminate the moon with a big ad for Coca-Cola, “since we now have enough energy for it”.

I wonder how many capture plants and energy would be required to bring it back to a normal level.

Let's run the numbers. I believe Climeworks' Orca is the largest DAC plant right now, and they claim it'll capture 4000 tons/year. We currently emit something like 40 gigatons/yr. (4*10^10)/(4*10^3) = 10^7 DAC plants. So let's say that DAC isn't a silver bullet :-) There are a whole portfolio of other carbon capture and sequestration technologies that'll be needed to get us carbon-negative enough to avoid going over +2 degrees C.

Of course, by the time we have spare fusion power, that'll also have replaced much of those 40 gigatons, and Orca is certainly not the upper limit in terms of scale.

And we've emitted 2 teratons of excess CO2 that needs to be dealt with as well.

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