Efficient method to capture carbon dioxide from the atmosphere

According to https://www.co2meter.com/blogs/news/carbon-dioxide-indoor-le..., at 1000 ppm people start getting drowsy. Let's assume that a decent indoor environment has 300 ppm more CO2 This means that our threshold for when people start getting drowsy even in decent indoor environments is when atmospheric CO2 reaches 700 ppm. For reference, it is currently around 420 ppm, and pre-industrial levels were 280 ppm.

From https://www.climate.gov/news-features/understanding-climate/..., the pessimistic projections suggest that we may reach our 700 ppm threshold by roughly 2070; 45 years from now. (The graphs are hard to read precisely)

The 300 ppm offset compared to the outside air is naturally just an arbitrary number, everything up to 1000 ppm (meaning everything up to 580 ppm more than atmospheric levels) is considered "acceptable". That means any increase in CO2 concentration will take an indoor environment which used to be considered "acceptable" and make it cross the threshold into "unacceptable". An indoor environment which would've been at 900 ppm around the industrial revolution (280 ppm) would've crossed the threshold when we surpassed 380 ppm (which was in 1965 according to https://www.statista.com/statistics/1091926/atmospheric-conc...).

let's compare the past 20 years. In 2004, the concentration was ~377 ppm. That's 47 ppm lower than what was in 2024. An indoor environment which was "borderline but acceptable" at 955 ppm CO2 in 2004 would've crossed the arbitrary 1000 ppm threshold by now, and therefore would benefit from a CO2 scrubber. The next 20 years will likely have a higher increase than the past 20 years, so there will be a larger range of currently acceptable indoor environments which will cross the 1000 ppm threshold by 2045.

TL;DR: It's complicated, 20 years is arbitrary, but as CO2 concentrations increase, indoor quality gets worse so indoor environments which were already bad will become worse. 45 years is a more realistic estimate for when your typical good indoor environment will become unacceptable, but it's a gradient.

Think about the magnitude you’re talking about here. Every internal combustion engine on earth is emitting CO2. Every volcano, forest fire, coal power plant, etc. The atmosphere is massive. We’ve been, basically, doing our best to pump it full of CO2 for the last 150 years, and this is what we’ve got. Ignoring the chemical challenges with your idea here, the scale is impossibly gargantuan.

Where else are they going to come from? They’re all basic elements, either you separate them from air, or you have to go through an energy intensive process to liberate them from various chemicals they’ve been compounded into.

But guess what, all of those chemicals are extremely valuable, such as nitrates for fertiliser, water, and Argon does really react with anything (it’s a noble gas), which is why we use it as a shield gas in processes like welding.

So producing enough of those gases to somehow offset CO2 production would first require ludicrously large amounts of energy, and if we had access to that amount of clean energy we wouldn’t even be having this discussion. Plus it requires breaking down really valuable chemicals that we spend quite a lot of energy trying to produce or preserve anyway.

Still, it will add some 80ppm over the amount you have today. There's a huge amount of disagreement over how much CO2 is harmful, but it tends to happen over numbers way above 800ppm.

If your room has 2 times the open air concentration, and you are concerned if it's 2.0 times or 2.2 times, you should already be dealing with the problem.

Supercritical CO2 turbines: https://energy.wisc.edu/industry/technology-highlights/super...

On a much smaller scale I've been hoping for a small solar powered CO2 compressor to exist so I could use it for mosquito traps. The state of the art for those right now is burning propane for the CO2 combined with a scent emitter for the human smell to attract female mosquitos.