How Much Energy Would It Take to Pull Carbon Dioxide out of the Air?

Basically... A lot! Just to have what effectively amounts to a painkiller. Now don't get me wrong, those are great but you know what's better? Solving the issue that causes you pain to begin with.

Hmm ...what about continuing to go on benders every night and not addressing the problem at all? Would that be bad?
I know something better and it's solar powered: Trees!
- Trees are great for other reasons, but they grow far too slow to capture significant carbon. The fastest natural carbon sinks are algae.
- But think of all the space that would take! If you replant forests where are we going to put our superhighways and parking lots?
At this point, we need to do both
Sounds like a great use for nuclear and then if there's a drop in renewable energy it can pick up the slack

None. They are called trees. We should stop wrecking things.

To be fair trees still use energy for doing this, but that energy is conveniently provided by the sun.
- If humans could make a profit off of killing the sun, they would.

Algae does it for free all the time. Physically trying to capture carbon dioxide is dumbassery. We need more investment in algae production.

It could be beneficial for densely populated areas, though. Because you have predictable airflow and low-hanging regions to implement physical capture and sequestering. We can do more than one thing at a time and targeted approaches combined with generalized approaches will yield faster results.
- In order for that we need more renewable energy, otherwise we're just burning fossil fuel, producing carbon dioxide, and then capturing it. Solar, wind, algae biofuel, renewable diesel, green hydrogen, etc. We have to be careful how we use energy otherwise we're just producing carbon dioxide to capture carbon dioxide.
Algae doesn't capture it for long. Trees do it for longer but not long enough to be more then a speed bump. Unless we start dumping algae and trees into giant pits and sealing them up three is no long term carbon capture.
- Biochar (created in a retort) is how you sustainably sequester carbon for the long-term using trees (and similar biomass).
- Algae doesn’t capture it for long.
  
  Not true, it depends on how it's contained. Drying algae and removing the water will stop it from decomposing. Think of seaweed used for sushi except ground up into a very dense powder. Algae will decompose if left hydrated in the sun though.
- A single tree isnt a long-term capture, a forest is
Techbros were pitching how we'd invent self replicating carbon capture nano machines in the future
- That's so annoying about motorsports in recent years. Commentators are tasked by the race series owners to hype up that BS. Researching the technology is fine. Scientists may find ways to capture carbon at a better rate at acceptable energy cost but shouting that an inefficient combustion engine is somehow better for the environment than EV because "batteries bad, carbon capture great" is just stupid.

If we wanted to remove enough CO2 to get back to the preindustrial level of 280 ppm, it would take 2.39 x 10^20 joules of energy. For a reality check, that's almost as much as the world's total annual energy consumption (5.8 x 10^21 joules every year).

Isn't that over an order of magnitude difference? What am I missing? How is that "almost as much"?

Yep, it's close to 4% of the total. Not really "almost as much".
- That's honestly pretty good, I can see world leaders coming together and just doing that. There must be other technical challenges to this other than raw power usage
I'm guessing they don't understand scientific notation, and "numbers are close" without understanding the numbers are much more significant
- even if 10^20 was almost 10^21 (which is isn't) 2.39 is not almost 5.8. It's less than half!
  
  Why do we listen to people who do not know what the fuck they are talking about? Have we lost our ability to know who is, and is not, completely full of shit?
This is why STEM education is important. You clearly learned from yours and that's awesome!
The problem is that this is a theoretical minimum, not an actual, proposed process. We'd need a way to attract CO2 to separate it from the rest of the air, and afaik that doesn't exist. Any actual process is likely to be far less than 100% efficient, probably an order of magnitude or more less.

This is an example of a real proposal, but I have no idea how efficient it is. It would be a lot more helpful if this article provided a realistic example instead of some back-of-the-napkin math.
- Oh yeah, I agree it's super inefficient currently. But if the theoretical 100% efficient process is 5% of our current yearly energy expenditure, that sounds promising and suggests we shouldn't just write off the idea.
- We'd need a way to attract CO2 to separate it from the rest of the air, and afaik that doesn't exist.
  
  Call me crazy but what about plants and trees?! 🤷🏼‍♂️
  
  They might not be 100% efficient but it's dirt cheap to plant them, let alone not destroy the rest we still have
I didn’t read the article but it seems off. With only 1/20 of energy used by the world in a single year we could undo the damage of 300 years?

Seems too low. If that’s true we could shut down completely for just two weeks to undo
- Can't imagine "shutting down completely for just two weeks" would exactly be reasonable, but yeah I wonder if the article had a typo in it. I'm not sure. As of right now, the numbers are still the same in the article.
  
  If the numbers are correct, expending like 5-10% of our energy expenditure for a single year on carbon capture sounds a lot more reasonable than the article suggests. Even if it were half of our yearly energy usage, that sounds pretty reasonable if you draw that out over a few decades.
That’s like 24x more….

Carbon capture makes much more sense directly on smokestacks and other industry waste outputs, but then how do businesses make taxpayers fund it?

Idk, I just feel like it’s 1. A cop out. We need to reduce emissions and not put our eggs in one basket. And 2. In its infancy. The tech isn’t efficient enough yet to be rolled out imo
- I think we should pursue it for the future, but it shouldn't be taking funding that could be used for more immediate solutions or used as a distraction / delay tactic (although of course it will).
Preventing additional carbon emissions doesn't decrease what's already in the atmosphere. We would need some form of carbon capture even if we stopped all emissions today.

TL;DR: the total energy produced by humanity in a year.

Or if you want to do it in let's say 20 years, 5% of the total power output.

That doesn't sound too bad.
- Technically yes, but politicians start freaking out as it would lower GDP a few percent too.
It's way less than that. 2.39x10^20 is around 4% of 5.8x10^21. Not even close to "almost as much". Looks like the authors don't know their powers of 10. So if we dedicate 5% of the total energy for one year it could theoretically be done.
- Assuming a 100% efficient CO2 capture system...
  
  Here's an actual carbon capture system, I have mo idea how efficient or practical it is.

It depends on the method. IIRC, the most cost effective methods cost more than leaving it there. The real problem really is figuring out how to make a profit off it. Without the government forcing it subsidizing it, nobody will do it, even sustainably, in volume enough to matter.

That's what the article theoretically exemplifies, avoiding emission in the first place is the best bet.

Targeting the preindustrial level of atmospheric CO2 is such an ambitious target, trying to undo 300 years of emissions. Then again, it's not like we've stopped emitting.

If we instead try to calculate the energy requirements to simply offset the average emissions of that particular year, using this formula of 652 kJ/kg CO2, and average annual CO2 emissions, against the current numbers of about 37 billion tonnes, or 37,000,000,000,000 kg, we have 2.4 x 10^16 kJ, or 2.4 x 10^19 joules. Which converts to 6.7 x 10^12 kWh, or 6,700 TWh.

Total annual US electricity generation is about 4700 TWh per year.

Global electricity generation is about 25000 TWh per year, about 40% of which is from low or zero carbon sources.

So basically if we've got 6700 TWh of clean energy to spare, it would be more effective to steer that into replacing fossil fuels first, and then once we hit a point of diminishing returns there, explore the much less efficient options of direct capture for excess energy we can't store or transport. Maybe we'll get there in a decade or two, but for now it doesn't make any sense.

Actually a thorough article from Wired. Oh...written by an Associate Professor, that's why.

Casey Handmer seems to think there’s still an opportunity here. There are updated versions of that post, but I think this was his first on the topic.