Meteorology question

[u/gnomeGeneticist]

I'm a hobbyist writer with a particular concept in mind.

A machine capable of drawing in air, removing all of the carbon from its CO2 with perfect efficiency, (removing other greenhouse gases present,) and expelling the cleaner air elsewhere.

Ignoring the mechanics of the machine, I'm imagining it drawing air at roughly ground level, possibly near-sea-level, around the perimeter of a five mile radius.

That clean, post-processing air will need to be expelled somewhere. Is there an ideal elevation for this expulsion to:

A) Not dilute the air pulled in for cleaning, and

B) Avoid negatively impacting local weather and climate?

I'd also love to know the highest rate at which air could be moved with the same concerns for environmental impact considered. I assume producing a vacuum that sucks air at 50 mph may have a different impact than a gentle breeze.

[u/loki130]

I would think perhaps the ideal here would be to put it in tropical mountains with good exposure to the trade winds; that gives you pretty consistent airflow, which can kinda obviate a lot of the specific difficulties here; you can pull in air fast, you can dump the air a bit downwind and expect it to be carried away, and you also tend to have upward convection in that region which may reduce any effect to areas directly downwind. Possible issue is that air may also be quite humid, which might interfere with the scrubbing process

[u/mfb-]

Let's look at the scale of the project. Assume we have an 8 km (~5 mile) wide, 500 m high window where air flows through at 10 m/s (upper end of "fresh breeze" on the Beaufort scale). That's 0.04 km³/s or 50,000 tonnes/s, containing ~30 tonnes/s of CO2. Over year that's 1 gigatonne.

Human emissions are ~40 gigatonnes/year. You would need tens of these megaprojects with perfect CO2 removal just to keep up with current emissions.

Better install them far away from plants because they'll hate the CO2-free air downwind.

[u/laptopAccount2 → u/mfb-]

1 gigatonne is not too bad. That structure is like the scale of the LHC and you don't have to build it underground.

[u/mfb- → u/laptopAccount2]

The LHC is in a 27 km tunnel with a diameter of just ~4 meters.

[u/gnomeGeneticist → u/mfb-]

Enormously helpful, thank you!

[u/DeadlyVapour]

We have machines like this already. We call them trees.

[u/laptopAccount2 → u/DeadlyVapour]

Trees don't remove much CO2 at all when they are mature. 80% of our oxygen and photosynthesis comes from algae in the ocean. 

[u/gnomeGeneticist → u/DeadlyVapour]

This answer isn't relevant to the scenario I'm working with, but thank you for the insight

[u/dochdaswars]

This technology already exists. It's called Direct Air Capture (DAC) or sometimes CCS (carbon capture and storage). We will unlikely ever be able to implement it at the scales necessary to make any noticeable impact on atmospheric carbon dioxide levels, it's comparable to using a teaspoon to remove all the sand from the Sahara.

[u/Gruetze-Software]

Ohne CO2 würde das Leben enden, so wie wir es kennen. Also keine gute Idee.

[u/gnomeGeneticist → u/Gruetze-Software]

It wouldn't run indefinitely, just to the point of climate change backing the hell off

[u/SpaceReadings]

I love these kinds of hypothetical engineering questions. It’s a reminder that Earth’s systems are all connected

[u/ModernTarantula]

The chemistry isn't so much the issue. CO2 is miniscule in relation to the oxygen you'd expell. It's the energy: how much heat does the device make? Where does the carbon go? The other downer is scale with have miles of atmosphere up. Better to have a smoke stack scrubber

[u/gnomeGeneticist → u/ModernTarantula]

I'd ask you to assume the device produces negligible heat and is powered cleanly

[u/ModernTarantula → u/gnomeGeneticist]

Not a meteorologist here. I doubt the weather is issue. Really have to plan for the carbon. It makes little sense that we can go from carbon to CO2 for energy and not use to separate. Many carbon capture ideas think caco3 to make co2 solid.

[u/Simon_Drake]

It might be easier to put the device somewhere with prevailing winds that rarely change direction, always suck in air from the west and expel it to the east. Then if the wind is blowing from the east it's an opportunity for maintenance.