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Trees respire. They breath in and out. At night time, many trees emit more CO2.

And trees don't exist in isolation as these napkin calculation articles consider them (spherical cows and all that). Every single tree on earth relies on mycorrhizal fungi for the vast majority of its nutrients. Fungi break things down release CO2.

Most of our oxygen comes not from forest but from oceans (specifically from phytoplankton, algae, and photosynthetic bacteria). Between 50-80% of it in fact. Likewise, most of the CO2 that has been captured has been captured by the ocean not by forests. About 25-30% of all human emissions have been captured by the ocean.

Forests (and grasslands) are tremendously important for ecosystems and our health but I think this focus on CO2 and oxygen is simply misleading. If that's your concern you should really be focusing on the ocean. Which IMO is in an even more dire strait than our forests

Forests do net sequester carbon. But if you want to really sock away the carbon you harvest the trees and pyrolize it. It will give you energy (heat) you can use and elemental carbon (biochar). You could bury that a few feet under or innoculate it with microorganisms and work it into fields. Carbon in that form will sit in the soil for hundreds of years. Thousands or millions if you bury it.
The ocean breathes in and out too. Very little carbon sinks down to the sea floor. The ocean does happen to absorb a lot of CO2, but that's from acidification rather than photosynthesis.
> Most of our oxygen comes not from forest but from oceans (specifically from phytoplankton, algae, and photosynthetic bacteria). Between 50-80% of it in fact.

That fact checks out: about 70% of the earth's surface is covered by oceans. It follows that most photosynthesis, thus oxygen comes from oceans.

Forests and grasslands are critical for the climate because of the carbon they lock away. So long as the plants stay alive, they store carbon in the cellulose structures of roots and stems.

Conserving these ecosystems is less about their daily respiration and more about keeping existing carbon out of the atmosphere. It's a defensive strategy. Not "carbon capture" per se but more "avoid loosing the carbon we've already captured". We're interested in the sink, not the flow.

Of course when the plant dies and decomposes or burns up, it all goes back. Long term, it's almost exactly net zero. The ONLY way to use plants for long term carbon sequestration is to make sure that plant matter gets treated or literally buried so that aerobic microbes and fungi can't break it down.

it looks like i'm guilty of having never really thought and done some research about this and i'm a bit ashamed to admit i fell in this trap and used to think forests and trees are the most important pieces in the system.

I don't get why media has been fixating so much on trees and forests (Amazonia!) without even mentioning ocean's role in this.

> Which IMO is in an even more dire strait than our forests

I think you are probably right, but could you kindly elaborate and provide more details? Very curious to hear your view and learn more.

If the ocean is the main hero there, why is the forest still important to our health?
“I couldn’t live with so many trees. They suck up all the oxygen.”
(Author here) I've added the word "indoor" to the title, which will hopefully make it harder to miss that this is not about climate change or carbon sequestration.
As somebody who works on carbon dioxide removal at planetary scale, I was excited about your article about indoor air… but nearly every comment here seems to want to talk about the changing climate!
It's an interesting article overall, but this assertion:

> Carbon dioxide is bad for cognition.

is dubious and unsupported by science. As I point out downthread, we have extensive experience with very high-CO2 environments-- at levels regularly exceeding ten or twenty times current atmospheric levels-- and as yet little good evidence of uncompensated cognitive effects.

Beyond that, modern humans live much of our lives in moderately elevated CO2 with no apparent ill effect. Without deliberate ventilation, any enclosed space like a bedroom or classroom will rapidly achieve elevated CO2 levels, often into the thousand ppm range. Again, we have lots of data, and little of it points to a practical cognitive effect.

The US Navy maintain an informal goal to keep levels on board submarines to below 8000 ppm, loosely informed by what little evidence they have of its effects on crew performance. That's twenty times the current atmospheric levels. In practice, CO2 levels often go over 10,000 ppm, which apparently still doesn't cause them much concern.

Did you consider the alternative calculation of how many plants you need to grow to feed yourself? A few thousand potatoes growing simultaneously might do it.

That would overestimate the number you need to remove excess exhaled CO2, since you could throw out the parts you can't eat rather than letting them decay and release CO2 indoors.

OK, so we can’t use plants.

What are the options, then?

In my apartment I’m running 2 AirGradients. One in the bedroom and one in the main room.

Awesome little devices, btw. They monitor temp, humidity, CO2, TVOC, and various particulate matter metrics. They expose prometheus metrics for scraping, and can be configured through a REST API to never phone home. I’ve got grafana alerts set up to push notifications to my phone when things get to “bad” ranges.

Anyway, the big issue is that the only way I’ve found to clear CO2 and TVOC is to open windows. However, windows open means increased humidity and particulate matter, even with air purifiers running aggressively. Also, opening windows at night kind of sucks for obvious reasons. In the summer it also sucks to lose that cool air.

I found these devices you put in your window, sort of like window fans, that can open/close airflow completely, but they don’t fit in my side-opening windows.

The only other thing I can think of is some kind of home automation with a little gadget that cracks the window until the metrics are back in an acceptable range. My AC unit unfortunately does not have a mode where it takes air from outside. I know some things like this exist for opening blinds, etc, but haven’t gone down that rabbit hole yet.

Anyone find a good way to solve this problem?

Challenging in an apartment setting, but the state of the art here is an Energy Recovery Ventilator (ERV) installed in your home to continuously refresh the air.
NASA is working on it: https://www.nasa.gov/spacecraft-oxygen-recovery-scor/
"Residential CO2 scrubber" seems like the sort of gadget eccentric rich people would buy, sort of a distributed DAC system.
If it wasn't an apartment and you could cut holes in the wall, I would say a ductless HRV.
I don't really understand this. First of all, you can just weigh the plant, and tell how much CO2 it has captured, right?

Second of all, what does it matter how much CO2 I produce? What's harmful is the additional CO2 that goes into the atmosphere for burning fossil fuels. All other CO2 is just in the same cycle that's been happening for ever.

EDIT: My child comment is dead and vouching doesn't resurrect it, but now the post makes sense, thanks for the clarification.

> what does it matter how much CO2 I produce

Because the author of the piece is worried about the CO2 levels in their home, not about global warming. (well maybe they are worried about global warming too, but that's not what this is about)

You can sequester carbon with plants, but you can't let them decay or it will release it back into the environment (it's called the "carbon cycle" of a reason).

A startup has solved this problem the following way (for example): grow microalgae near a very dry desert, and bury it in trenches. It never decays and thus never releases CO2 due to lack of water.

Basically, we'd have to permanently stick it back underground again.

The BBC did this in their 2012 documentary mini-series "How to Grow a Planet" with Iain Stewart. It was a lovely series; I highly recommend it.
OK, this was fun.

But I think the real problem is that we’re pushing carbon into the atmosphere that has hitherto been sequestered for upwards of millions of years deep underground and under the oceans. I.e., nothing that’s been a part of a plant, or involved in any ecosystem, on the surface or underwater for a very long time.

Do we even have enough land on the planet to grow enough plants to sequester all this additional carbon? If we reforested the whole earth, would that be enough (and over what time period)? Can enough plants grow in the oceans without turning them all into a giant algal bloom?

I don’t know but I certainly would like to see the maths that answers those questions.

Or… you could go outside?

But the analysis rests on 0 ventilation, which doesn’t work at all.

I think the main thing to keep in mind is plants really aren’t industrial carbon sinks. They were never evolved to be. Their biological functions are about growing and thriving, and the soil they grow in are net carbon producers.

In a broad open system, they are net carbon sinks over the long term. But any analysis in a closed system is bound to fail, you don’t even need numbers to know intuitively this won’t work.

Crack open a window. Run a fan. Have plants because they have many benefits. Reducing CO2 around you meaningfully isn’t one of them.

What if the plants were algae?
Related tangent: I recently bought an inexpensive consumer CO2 monitor for under $40. It confirmed my suspicion about air quality in my home office; after a few hours, levels rise above 1000ppm unless I leave a window partway open. Mid-afternoon mental fog cleared right up.
Of course, do it with vats of plant cells in floating oceanic CO2 factories. Not in your living room.

Or, just let the oceans recover, let the mollusks return to the bays and shores, let them do their efficient thing.

This guy actually built an algae farm to test how much you need to breathe. https://youtu.be/AAbyUaLN2QA
The grow lights are only needed at night.

You can leverage a sunny window for free.

I would have liked a more how many plants can do it, rather than the its impossible route.

AI says a snake plant and spider plant can produce oxygen night & day. Now assume I live in a tiny hovel (kinda true) how many plants do I need for "net oxygen surplus" (?)

Apparently, AI says, high yield crops of say wheat under intense LEDs or Spirulina make for optimal oxygen producers.

So 15 m^2 of spirulina in an aquaponics garden with intense led fixtures to supplement natural light might do it.

I can’t find a single credential or scientific qualification of merit of the author and yet their commentary spans many topics, including cancer.

I’ll pass. The About page is not very helpful either. It says very little about the author except this:

> Like most people, I use AI “for research”, but I impose fairly strict limits to make sure I don’t use AI “for writing”.

I have had the same impulse to reduce CO2 to about half(Close to pre-industrial levels 200 to 280 ppm). Of course my first thought was CO2 scrubbing by chemical means, plants are obviously silly. But was convinced not to pursue given the fact that

1. Cognitive decline starts above 600 ppm according to air quality studies.

2. Levels below 200 ppm are actually dangerous.

Bamboo it is.
> Real plants do photosynthesis through a physical process

(nit) it is more accurate to call this a biological process, or chemical process

Saying "physical process" makes me think of inclined planes, free-body diagrams, and EM fields.

The vast interior of the world's oceans are a nutrient desert. It has been proposed to grow algae by spreading silt, the same way that Saharan winds do.
I’ve always wanted to jam on how to create an indoor carbon dioxide removal system. (I think that’s what this article is about but perhaps it’s indirectly about the changing climate)

1 kg per day of material adds up fast but that assumes zero ventilation. If I simply wanted a system to keep my office below 500 ppm all day, I wonder how much material that would produce.

Anyone ever build a little carbon dioxide zapping system for indoor air quality? I’ve also heard that indoor CO2 isn’t actually all that bad but it’s VOCs that are what make me feel sluggish.

4.6 kg is easily dwarfed by just one of the trees on my lot.

I do like the math though. Gonna be very useful for space colonization

Or you make like old times and use the sun: build sky windows, green houses and indoor winter gardens.
I figure answers to these questions are probably available online. Why discuss them here specifically?
Always seemed like algae or cyanobacteria are the only real nature based options that could be scaled up.
How is it that 132.5 watts is 3 light bulbs but 918 watts is 765 light bulbs? Is there a typo?
That one final number is all one needs as a reply for "but they help a little".
Get an HRV/ERV if you can't open a window.
Another way of looking at this is that--while it doesn't have to be edible--you have to grow plant matter inside your house at a rate equivalent to what everyone in there consumes as food.

Even if you found like an algae or something that converted CO2, light, and water into fat, 2400 kCal would be ~300g per person, per day, or not too short of a normal package of butter.

no, we are useing solar PV to eliminate the excess carbon bieng added to the atmosphere, and plants, rocks, and many other natural processes will return CO² levels to a more moderate level.
This seems trivial: if you could add enough plants to your room to reduce CO2, we could easily do the same thing at planet-scale and global warming wouldn't be an issue.
Sadly I am a bit hopeless about climate change. Even if every person on earth dropped everything and started making biochar to be buried it would not sequester enough carbon to make a difference.