Indoor CO2 may reach levels harmful to cognition by the end of this century | Hacker News Reader

Indoor CO2 may reach levels harmful to cognition by the end of this century

agupubs.onlinelibrary.wiley.com

119 pointsbeefield162 comments

A good deal is spent explaining rising CO2 levels in the atmosphere and the effects of CO2 on cognition, but it wasn't immediately obvious to me how indoor CO2 levels would be rising. Towards the end, here is their explanation:

> in steady state, indoor CO2 concentration is always at least as high as the outdoor concentration (as neither generation nor ventilation rate can be negative) and simply scales with the ratio of generation to ventilation. For reasonable values of G and Q for elementary school students (0.004 L/s per student) and classrooms (10 L/s per student), respectively, a ratio G/Q equates to 400 ppm (Persily, 2018; Persily & de Jonge, 2017). Under such assumptions, then, an outdoor CO2 concentration of 477 ppm (411 ppm as in 2019, plus a 66‐ppm urban enhancement) would equate to 877 ppm inside the classroom upon reaching equilibrium.

The equation and explanation can be found about 60% of the way down.

Most classrooms (at least here) aren't well-ventilated (windows are generally kept closed because of "draft" or alternatively "we aren't heating for the air force!", and buildings generally don't have AC/air exchange), CO2 levels are often far beyond 1000 ppm in classrooms anyway, which is obviously not good (there may be debate if going from 450 ppm to 600 pm leads to worse outcomes, but it's pretty obvious that nausea-inducing levels of CO2 and air so stale it feels like breathing water most definitely lead to worse outcomes).

If climate becomes warmer, then we'll open the windows more often :-)

Not if you're running AC.

I'm from a place where you only need AC one week per year so naturally no one has it except in cars, but I've heard that decent systems, especially central ones, don't recirculate the same air over and over again but take it from the outside.

Check out HRVs: (air exchangers)

Gwern raised some cautions about the studies indicating that these moderate levels of CO2 have cognitive impacts. I haven’t read enough to have an opinion, but any HN readers interested in this should probably follow up on the studies he references: https://news.ycombinator.com/item?id=21569947.

Their conclusion is that we should emit less CO2. Certainly a good idea, but their data clearly point to better ventilation.

Better ventilation is something we can do right now, that will improve things immediately and 100 years from now.

Maybe the best thing would be the mandatory installation of powerful ventilation systems with heat exchangers for new buildings, and incentives to upgrade existing installations. That would help with both problems: getting more fresh air and limiting energy expenditures which can, in turn, reduce CO2 emissions.

> mandatory installation of powerful ventilation systems

In my country that's already been a thing for the last few years. The HRV system is around €1000, so it isn't a major cost for the benefits you get. From this year all newly installed units need to be 90% efficient.

Also "powerful" is probably not needed, the system I have at the lowest speed changes the air in my entire apartment every 3 hours, and is basically the same noise level as a barely audible computer fan.

The difference in scale between your apartment and most schools is no trivial matter.

At my high school, our one building, with tall ceilings, large cafeteria and so forth, housed around 1300 people every day. Some are smaller, some much bigger.

Moving all of that air at least once a day would require powerful exchangers indeed. If nothing else, it would probably be cheaper and better for students to have plants everywhere. One of my teachers' classrooms was like a tiny jungle. I can't say that it made a significant difference, but it was pleasant at least.

Plants sadly don’t make a significant impact to indoor co2.

I see a future indoor co2 sequestration device being incredibly popular

> indoor co2 sequestration device

If you're happy for it to have rechargeable cartridges, you could easily build one with a once/week cartridge change. The cartridge needs to be ~the same weight as all the food eaten by all the people in the building.

The material the cartridge is made from is dirt cheap (literally limestone!), and recharging is a simple matter of heating it up.

With a pipe to the outdoors and some vents on a servo, the machine could even auto-refresh its cartridge every day, making it almost maintenance free.

I'm curious about this cartridge idea. I'm picturing a pipe with quicklime inside and coffee filters on the ends, with a blower to force air through. How tightly would the contents be packed?

This is a little different from what I'd been thinking before your message, which would be more of a fluidized bed reactor -- like quicklime swirling around in air in a garbage can. I think that's closer to how some powerplants treat exhaust.

I've read that there are microscopic changes to the quicklime particles after a couple absorbtion/heating cycles (their pores fill up or something), after which you need to do something to further refresh it, maybe by dissolving it and precipitating it back out of solution.

This led me to considering whether aqueous chemistry might be better.

The simplest would be to react air with calcium hydroxide (would you use a bubbler? Or a packed counterflow tower? Or a spray tower?) and collect the calcium carbonate that precipitates out.

But, based on my shaky chemistry, I understand solubility of calcium hydroxide is low, so you do better with a two-stage process like the Kraft Process:

1. Absorb CO2 in contactor:

2NaOH + CO2 -> Na2CO3 + H2O

2. Regenerate solution in causticizer:

- CaO + H2O -> Ca(OH)2

- Na2CO3 + Ca(OH)2 -> 2 NaOH + CaCO3

3. Decompose calcium carbonate:

CaCO3 -> CaO + CO2

The concentrated NaOH solution would be very caustic, so you'd have to be careful with that, but apart from that none of this seems too terribly scary?

Some parts of the above are endothermic, others exothermic, so maybe this could even let you shift energy from the summer (solar furnace?) to the winter when you need it, as part of the deal.

Or maybe this is all too complicated and you should just use a canister of soda lime granules, like an anesthesia machine? ( https://en.m.wikipedia.org/wiki/Soda_lime )

I'd be interested to hear more from people whose chemistry is better than mine.

Let's do the thermodynamics:

First, some enthalpies of formation (at 298 K and 1 atm, in kJ/mol) (from [1] unless otherwise indicated):

  H2O(l)       -285.8
  
  CO2(g)       -393.509
  CO2(aq)      -419.26
  
  NaOH(g)      -425.93 
  NaOH(aq)     -469.15
  
  Na2CO3(s)   -1130.77
  Na2CO3(l)   -1108.51  (from [2])
  Na2CO3(aq)  -1157.34  (from [3])
  
  CaO(s)       -635.09 
  CaCO3(s)    -1206.9
  Ca(OH)2(s)   -986.09
  Ca(OH)2(aq) -1002.82

The reactions:

1. 2NaOH(aq) + CO2(g) -> Na2CO3(aq) + H2O(l) ... -111.33 kJ/mol (exothermic)

Here I assume that the gas has to dissolve as part of the reaction so use CO2(g) instead of CO2(aq) on the left hand side. I get an enthalpy delta of -111.33 kJ/mol. This differs from some homework answers I find online like [4] because I use NaOH(aq) while they use NaOH(s), etc; I hope I'm right for this application.

2a. CaO(s) + H2O(l) -> Ca(OH)2(aq) .... -81.93 kJ/mol (exothermic)

2b. Na2CO3(aq) + Ca(OH)2(aq) -> 2 NaOH(aq) + CaCO3(s) .... 14.96 kJ/mol (endothermic)

3. CaCO3(s) -> CaO(s) + CO2(g) ... 178.30 kJ/mol (endothermic)

Energy issues:

The easy thing would be to run at least (2b) (causticization) concurrently with (1) so you're always precipitating out CaCO3 and don't accumulate any Na2CO3 solution. It would also be easiest to combine (2a) with (2b) in a single causticization chamber. And it'd be simplest to skip (3) entirely, just treat CaO as a consumable, and be happy that you've sequestered carbon as CaCO3.

However, in a temperate climate, you can imagine doing the following to shift energy around the year (how realistic this is I don't know):

- Only run (2a) during the winter, to heat your home; you'd accumulate Ca(OH)2 solution to be used during the summer in (2b).

- Only run (2b) during the summer, to cool your home. During the winter you'd accumulate Na2CO3 solution from (1), which you'd need to store.

- If you're doing (3), do it during the summer, when a solar furnace can be operated. This gives you a reagent that you'll use in (2a) during the winter.

- You'd want to run (1) all year round, to scrub the CO2.

The main inefficiency this is trying to make useful is that you need to go down in energy with (2a) and back up in (3). And down in energy with (1) and back up in (2b).

I'll next need to understand the soda lime method to compare.

[1] https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation [2] https://webbook.nist.gov/cgi/cbook.cgi?ID=C497198&Mask=2 [3] http://chemistry-reference.com/reaction.asp?rxnnum=454 [4] https://answers.yahoo.com/question/index?qid=20131119075117A...

Human's ability to concentrate is just one of many, many problems associated with increasing atmospheric CO2. We can't ventilate the troposphere.

Large scale carbon capture would be more economically beneficial and would provide more direct control over atmospheric levels of CO2. Bonus points if you can find a good use for the carbon.

Is there any practical way to have less indoor CO2 than outdoor CO2, without needing to buy expensive single-use scrubber chemicals? Maybe presuming you live somewhere with cheap electricity and/or a cheap fresh water supply?

Basically I’m asking whether there’s a Maxwell’s Daemon-like device for separating the CO2 from the air, and venting the CO2 back outside, while bringing in the rest of the air. Like a CO2 scrubber, but without any need for CO2 sequestration, since you exist inside an open system instead of in a space station/bunker/submarine.

I don't think this exists on a small scale yet.

On industrial scales, CO2 is commonly removed with reusable scrubber chemicals, referred to as a group as amines. The amine acts as a CO2 solvent, removing the CO2 from the bulk gas. The 'rich' amine is then cycled to a separate location in the process where it is heated up, causing the CO2 to bubble out of solution, regenerating the amine for reuse, etc.

I don't see any reason in principal why this can't be miniaturized, but it would be a challenging engineering problem.

https://en.wikipedia.org/wiki/Amine_gas_treating

Another solution would just be to pump in cleaner air. You could imagine a truck that drops off a few tanks of CO2-free air.

Perhaps we can install oxygen lines next to our natural gas lines.

I get your sarcasm but it'd probably mostly nitrogen.

There are these things called plants that do that kind of stuff, so maybe if you have enough of them inside your house, they eat the CO2 away... :)

I don’t think there’s any practical level of plant-having that would result in there being less CO2 in the house than in the atmosphere.

IIRC, there’s some point in running an indoor grow-ops where you start needing to worry about spraying CO2-enriched air on the plants; but that’s just to accelerate growth, like a fertilizer. Or, sometimes, it’s because OPSEC requires you to not vent your smelly waste air — and because no human or animal lives in the grow-op house to convert O2 to CO2, the air becomes gradually CO2-poor. But that wouldn’t happen if even one human lived there; humans convert metabolize a lot faster than plants do.

came here for this.

Regenerative CO2 scrubbers exist: https://en.wikipedia.org/wiki/Carbon_dioxide_scrubber#Regene...

Sounds like aquariums sometimes use CO2 scrubbers, so regenerative CO2 scrubbers might be commercially available for that market: https://www.youtube.com/watch?v=5_GM5ZBzvdk

> Regenerative CO2 scrubbers exist

AFAIK those still need consumables. NASA says there are ways to reduce the amount of consumables, but not eliminate them [1]:

In the current [...] configuration, carbon dioxide is removed from the cabin and discharged overboard. The gases lost during venting must be replaced, and thus represent a consumable. By comparison, a closed-loop CDRA system could selectively remove carbon dioxide from the cabin air supply, and the concentrated CO, would be routed to a carbon dioxide reduction system, where the oxygen would be recovered, thereby reducing the consumables.

[1] https://ntrs.nasa.gov/citations/20050210002

I think that quote is considering the oxygen in the CO2 to be a consumable, not the scrubber material itself. That's relevant on a spacecraft. But here on earth we've got plenty. :)

Yes, better ventilation is part of the solution. But the authors point out that in many urban areas a "dome" of increased CO2 hangs over the city. Ventilation won't solve that problem. Only reducing fossil fuel burning will.

My recommendation is to get an indoor CO2 monitor for your bedroom that can alarm whenever levels go above 1000 ppm. From what I understand high end office are being equipped with such systems with direct control of the ventilation systems for exactly this reason.

For home use a mid-range unit is sufficiently accurate, precise, and reliable. I use the Extech CO200 personally. Don’t but a cheap unit because those have calibration drift after a few months. And recalibration is not trivial.

To set the frame of reference for the parent's "not cheap" recommendation, the model they use seems to retail for $300-$400, based on a quick search.

I did some quick search end the very cheapest sensors seem to calculate something called eCO2. Like e.g.

https://www.adafruit.com/product/3566

What I was not able quickly to figure out is:

- What this eCO2 actually is?

- What is the real world accuracy I can expect from this kind of sensor, with and without calibration?

- is it enough for calibration just to go outside and assume some number between 400 and 500 (assuming outside means not just next to industrial chimney)? If not, what would be better calibration process?

Why not use a real one? MH-Z19 or Z14.

because my google-fu was not good enough to find those.... Regardless, I would be curious on the same questions about real world accuracy on those as well.

I have two of them, one inside and one outside. They both go down to roughly 400 ppm and the indoor one goes very high when it's all cooped up inside. The outdoor one fluctuates since I'm in an urban area. I believe they are accurate to within about 10%.

During the smoke event, they combined with my indoor/outdoor pm2.5 sensors have been extremely useful.

They should go down to 400ppm because the periodic autocalibration which is on by default assumes the lowest level seen in 24 hours is 400ppm.

You should be using the newer version, MH-Z19B, not MH-Z19.

The protocol is compatible though.

Also note they come in up-to-3000ppm and up-to-5000ppm variants. Be sure to get the latter.

In case it helps anyone: a very fast way to get it working and get graphs is to connect it to a Raspberry Pi running HomeAssistant. Takes a few clicks and 3 lines of config.

For portability, you can also hook up to an ESP8266/ESP32 and configure to talk to HomeAssistant via ESPhome: https://esphome.io/components/sensor/mhz19.html

I found this on what eCO2 is:

https://ec.europa.eu/eurostat/statistics-explained/index.php...

Re your other questions; yeah I gather there is some experimentation involved, even with out of the box commercial products.

If others have suggestions on chips or products to buy for the household, I would greatly appreciate it! The MH-Z19 looks like an option for me. Commercial products seem too unreliable for the price.

I think that is CO2e, which should be a different thing to my understanding. (CO2e is used to estimate the greenhouse gas potency of other gases like methane. Whereas I think eCO2 is some kind of estimate of amount of CO2 in the air, but what, exactly, I do not know)

Mine from Amazon is accurate enough to remind me of opening the window

> it will return a Total Volatile Organic Compound (TVOC) reading and an equivalent carbon dioxide reading (eCO2) over I2C.

It's an estimated reading of CO2, so it's not a direct reading, the sensor has to do some math to estimate the CO2

It's not very precise and/or dependent on temperature, etc

I'm using an NDIR-based USB-CO2-meter (~40 €, allegedly USB only for power, but it actually spits out measurement data over USB) and I think it's pretty accurate. When I put it outside it generally reflects ambient CO2 pretty accurately (440-450 ppm) and I found through blind-testing that "air staleness" correlates very well with CO2 concentration. For me, air feels noticeably stale at around ~700-800 ppm, which seems largely inline with academic results.

You can actually see when the device acquires a reading, because the tube flashes.

Even your unit has a trivial calibration. But in most cases you only need relative not absolute accuracy.

Yes, that’s the limitation of current technology. thankfully it’s doable with only a few minutes of attention and no tools or specialized requirements.

1000 ppm is an absolute limit, the vast majority of the population will experience measurable effects above this threshold. And it’s surprising how often that’s exceeded in normal everyday environments.

Would it be sufficient to just sleep with the bedroom window open? If so how large an opening would be needed?

A few cm are enough

Yes, modern buildings are really well sealed compared to before. A few cm is an enormous gap, relatively speaking.

I agree, I've measured this as well. Window in adjacent room (with open door between rooms), window opened 5-10cm, CO2 level stays pretty much down.

I've also found that when all windows are closed, an air purifier seems to help (or a fan, lowest level is fine). Obviously it doesn't remove the CO2, but it seems to prevent buildup in the one corner where you are (bed, desk). I'm sceptical it's a problem but the data shows it is.

Even keeping the bedroom door open helps. I did some tests with a CO2 meter - with the door closed it reached 1100ppm after a nights sleep. With the door cracked open it was around 700ppm.

One thing is that air diffuses out fairly effectively even with the door closed, presumably through gaps in the door frame. Quick calculation (welcome any corrections, numbers pulled from quick online searches):

Resting breathing rate is ~6 liters/minute.

Sleep ~8 hours = ~500 minutes = 3000 liters exhaled.

CO2 exhaled is 5% concentration, so 150 liters of CO2

Room = 30 m^3 = 30000 liters

Expected additional CO2 concentration in morning in perfectly sealed room = 150 / 30000 = 0.5% = 5000ppm

Actual additional CO2 = 700ppm (1100 reading - baseline 400ppm)

I think this wasn't about compromised air quality indoors. Rather general level of CO2 in the atmosphere. What help are ventilation systems then? You'd need to have submarine scrubbers in place to do something about it, and/or cans of liquid oxygen.

I think their point was that increasing CO2 in atmosphere makes it more difficult to keep indoor levels acceptable.

First, if you start from 600pm instead of 300, you reach 1000 ppm faster. Adding to the insult, it is much more difficult to ventilate the excess CO2 away, if the air you use to ventilate contains in itself already 600ppm instead of 300ppm.

Couldn't have said it better!

Indoor air usually has significantly elevated CO2 levels compared to outdoor air.

More ventilation cannot push the levels below the levels of outdoor air, but it can get them close.

Their argument that assuming today's already inadequate ventilation systems don't change, more outdoor CO2 = more indoor CO2, pushing it above some arbitrary threshold (which is far above predicted outdoor CO2 levels).

Can you recommend an affordable device? $100 for the Extech CO200 is just too expensive to suggest to people who have just a passing interest.

I do think we should think about passing out personal CO2 alarms now and in the future. The problem would be calibration like you said and cost for a new unit.

A regenerative CO2 scrubber that people could install inline with existing whole house AC systems would be a big success. I would buy it in a heartbeat.

So, we're burning fossil fuels, increasing CO2 output, don't have an idea which will reliably improve the situation and are getting stupider by the day, decreasing our chance to ever getting one. Yay...

We in fact have multiple ideas how to improve the situation. The problem is not a lack of ideas, or deployable technology, the problem is a lack of political will to implement the necessary measures.

We do. It’s called nuclear power and it‘s fought by those who claim they are fighting for the environment.

> https://www.giss.nasa.gov/research/briefs/kharecha_02/

Honest and good faith question here: assuming all electricity on the grid was nuclear, how much CO2 emission would remain? You can't just swap massive cargo ships to nuclear overnight. Would "just" making the power grid green be enough?

No, power generation is about a quarter: https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...

Transportation could push that total to 50% if all ICE cars were converted or destroyed and only electric vehicles were used (ignoring ships and trains). "Industry" includes CO2 waste byproducts which are much harder to reduce as many processes may struggle to eliminate that byproduct. Instead capture and sequestration would be needed. This is another 25%

The rest are small, but since we need virtually all CO2 emissions to be zero, we are left with nearly another 25% that isn't tied to electric production and is difficult to replace.

So, 50% of all CO2 isn't power generation related.

In the US we generate on average 0.99lb of CO2 per kWh. The total output is 1.87b tons of CO2. Total CO2 emissions in the US were about 5.17b tons.

So about 1/3 of emissions. It’s worth doing, considering we can reasonably execute this in a decade.

https://www.eia.gov/tools/faqs/faq.php?id=74&t=11

https://www.statista.com/statistics/183943/us-carbon-dioxide...

It’s possible to synthesize hydrocarbon and other liquid fuels using CO2 from the air, or hydrogen which has no carbon in it. If you have a closed loop with your carbon, you eliminate the problem (still have particulates, NO etc, but that’s separate)

Enough for what? Cheaper nuclear power on the grid may actually increase demand for other goods, so it's not clear how much the benefit would be.

No, it's opposed by people who are numerate enough to understand that nuclear is ludicrously expensive and completely unnecessary.

I live in Scotland. In the past 20 years we've gone from around 12% electricity from renewable to around 90%. The last coal fired station closed in 2016 and we've not added any new nuclear in that time.

This is usually the point that someone handwaves that having more money and more people makes you less capable than Scotland...

What's the lower proportion renewable sources produced in the last 12 months (in one minute intervals)? If that is much lower than 90% you have to have some other source (or accept frequent randomish power cuts).

Well, we don't have"randomish power cuts" so I guess someone solved that problem.

I think it's interesting that someone has to insist on something that doesn't exist to prove their point...

https://news.ycombinator.com/item?id=24529301

Fossil fuels provide the backup power source.

Yes, that's why we only get 90% from renewable. 10% is not.

Out of interest, what percentage are you at?

Well, we're linked to the English grid, and via connectors to Northern Ireland, continental Europe, etc. In practice the difference is made up by natural gas, and the large pumped hydro storage at Cruachan.

It has been some years since I had a power cut.

So fossil fuels provide the base load...

>This is usually the point that someone handwaves that having more money and more people makes you less capable than Scotland...

No a rebuttal on HN will usually be on the lines of something something small homogeneous population something something

While your point is accurate, I'm not sure it's in any way relevant to this. Perhaps a different discussion on bigotry within tech would be the place for this.

.. and the nuclear that we do have is in trouble: https://www.theguardian.com/uk-news/2020/aug/27/hunterston-s...

Not to mention the pile of nuclear warheads parked in fallout radius of our largest city. Which is the real origin of a lot of the opposition to nuclear.

>...I live in Scotland. In the past 20 years we've gone from around 12% electricity from renewable to around 90%.

Scotland has done an amazing job of decarbonizing the energy sector. That said, the important thing about electricity is that storage is very expensive so you have to export when the wind is too strong and import when there is no wind. From the "Annual Compendium of Scottish Energy Statistics 2020" Aug 2020 update available here:

https://www.gov.scot/publications/annual-compendium-of-scott...

>...For almost three quarters (74.4%) of the time in 2019, Scotland met its own demand with its domestic low carbon generation only (renewables and nuclear), down from its peak of 77.8% in 2017. This is likely to be related to outages in Hunterston nuclear power station in 2018 and 2019. Scotland’s rapid rise in renewable electricity generation means that renewables alone met electricity demand for an estimated 42.3% of the time in 2019, rising from 0.0% as recently as 2012.

>...In recent years, imports have increased as well, rising from approximately 200 GWh in 2014 to more than 1 TWh for every year since 2016. This is possibly a consequence of the closure of the coal-fired power station at Longannet in 2016, which has meant that there has been a potential need for Scotland to have non-intermittent electricity generation available.

Obviously it is the intermittent nature of renewables that is the challenge. As the Royal Society of Edinburgh wrote in "Scotland’s Energy Future":

>...The reality of where we find ourselves, however, is that the planned closures of both of Scotland’s remaining nuclear power stations by 2030 will see Scotland lose the source of generation for almost 43% of its electricity, going into a period where it is widely expected that demand for electricity will increase. These closures potentially coinciding with the end-of-life of the first wave of offshore wind only adds to this problem.

https://www.rse.org.uk/wp-content/uploads/2019/06/Energy-Rep...

There are actual safety and environmental concerns that I wouldn't dismiss as "claiming to be fighting for the environment".

I do agree though that even I used to be completely against nuclear power because of the unsolved waste problem. However in light of the last 25 years not having brought enough progress to prevent an environmental collapse I'm inclined to accept that now, as yet another thing we'll just have to figure out at some point.

http://www.deepisolation.com has solved the waste problem.

>...I do agree though that even I used to be completely against nuclear power because of the unsolved waste problem.

In terms of the waste, right now nuclear waste could be recycled which would reduce the amount of waste: https://en.wikipedia.org/wiki/Radioactive_waste

Soon it will be possible to use most of the waste as fuel:

"...Fast reactors can "burn" long lasting nuclear transuranic waste (TRU) waste components (actinides: reactor-grade plutonium and minor actinides), turning liabilities into assets. Another major waste component, fission products (FP), would stabilize at a lower level of radioactivity than the original natural uranium ore it was attained from in two to four centuries, rather than tens of thousands of years"

http://en.wikipedia.org/wiki/Integral_fast_reactor

https://en.wikipedia.org/wiki/Generation_IV_reactor

While there are issues with nuclear power, the worry people have about nuclear waste is greatly overblown to say the least. The amount waste is very manageable (the Netherlands actually stores their waste in an art museum) and in a relatively short amount of time we will likely be able to use most of this "waste" to generate electricity.

We also need carbon tax to pay for carbon extraction plants: https://www.theguardian.com/environment/2018/feb/04/carbon-e...

Put these plants in USA deep red states to create high paying blue collar jobs in construction.

Help level out impact of coal mining ending.

Nuclear arms proliferation is a bigger risk than global warming, though there are reactor designs that try and minimize it.

There are, anything that isn’t a breeder won’t build up enough plutonium or it will burn that too but it doesn’t mean you can’t convert them to breeders by changing the fuel cycle.

To combat proliferation reactor designs aren’t the issue, you need to control the source of the fuel and it’s entire lifecycle.

Building nuclear weapons isn’t hard, but it’s a project that requires a huge investment in infrastructure so proliferation has always been a question of will and consequences not capability.

Will you still be saying this if/when renewables are providing >80% of grid electricity?

If nuclear power was the safe clean panacea that people say. The dirty hippies would have be steamrolled long ago.

most critically electrifying everything in a city will both reduce that localized increased C02 level while also reducing ozone.

Has anyone experimented with supplemental oxygen for cognitive benefit?

Increasing O2 has physiological effects different from the effects of decreasing CO2. It is not just the ratio or difference between the concentrations that matter.

For example, a major effect of increasing CO2 is to make the blood more acidic (or to put more stress on the homeostatic mechanisms that maintain a target pH), and my guess is that no amount of increasing O2 will cancel that out.

> a major effect of increasing CO2 is to make the blood more acidic (or to put more stress on the homeostatic mechanisms that maintain a target pH), and my guess is that no amount of increasing O2 will cancel that out

True. More details on this mechanism:

The body uses buffer systems in order to minimize blood pH changes. For example, the bicarbonate buffer system which is catalazyed by carbonic anhydrase.

  CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃- + H+

It is converted back to carbon dioxide in the lungs and exhaled. The rate at which this process occurs is mainly influenced by respiratory rate. Oxygen doesn't directly influence it. O₂ enables aerobic cellular respiration, the process which produces carbon dioxide.

The hydrogen ions are buffered by proteins such as hemoglobin. They are also excreted by the kidneys.

https://en.wikipedia.org/wiki/Buffer_solution

https://en.wikipedia.org/wiki/Bicarbonate_buffer_system

https://en.wikipedia.org/wiki/Acid%E2%80%93base_homeostasis

https://opentextbc.ca/anatomyandphysiology/chapter/26-4-acid...

I don't think anyone's studied it for every day cognitive benefit but oxygen supplementation is common in medicine. Note that increasing oxygen concentration is not the same as decreasing carbon dioxide concentration.

https://en.wikipedia.org/wiki/Oxygen_therapy

https://en.wikipedia.org/wiki/Hypercapnia

https://en.wikipedia.org/wiki/Arterial_blood_gas_test

Obese people can also experience cognitive symptoms due to hypoventilation.

https://en.wikipedia.org/wiki/Obesity_hypoventilation_syndro...

I suppose this could be considered analogous to breathing in air with high carbon dioxide concentrations.

This is already a problem in classrooms etc, and shows itself by tiredness and headaches. As I understand it, this will only push harder towards better ventilation.

Not just indoor. Just google what a 400ppm increase does and look at projections. The IPCC predicts that major cities might reach 1000ppm outdoors.

Looks like in a few decades the AC units will be coming with CO2 scrubbers standard. Just a one more way the global warming is going to tax our economy/society.

Wouldn't home CO2 scrubbers need fairly frequent filter replacement? I can easily imagine units being sold with a subscription, e.g $14.99/month and you get a new filter every month.

Just get one of this: https://www.amazon.co.uk/gp/product/B01DY30PG8/

So. What are you going to do when it shows you levels of CO2 too high? Opening a can of Perry Air, search for https://duckduckgo.com/?q=air+quality+improvement+with+plant... , or what? Using it as an indicator of when to finally move elsewhere?

Right now? Open the window :)

How is that helping when the outdoor CO2-levels are elevated too much?

(Unter Schmutzatmosphäre verkackt! https://en.wikipedia.org/wiki/Packaging_gas)

It still takes time for outdoor normal co2 level to reach those levels.

We gain 2 co2 per year.

And you can have an indoor garden

Invent a way to put a square peg in a round hole, rapidly.

Plants + grow lamps. Get something easy to grow quickly indoors, say some random type of weed, and start letting it absorbing co2.

Open a window. Those grow lamps use energy and might contribute to the problem, depending on where you live.

The reason energy use is a problem is the electricity production.

And electricity production might not be that carbon-intensive depending on the place, hence "depending on where you live" :)

I feel like I have to combust some random type of weed to that, indoors even! :-)

Burning it back into CO2 is certainly more environmentally friendly than dumping it to decompose into methane.

Excellent reasoning. I need to remember that one.

You could capture and consume the methane as part of your home's energy cycle.

But composting both avoids methane production and sequesters carbon.

My understanding is that aerobic composting does not produce methane, but anaerobic composting does. If you're doing the composting at home you can set it up for aerobic composting. But if the waste material is going into a landfill, it's more likely to end up in an anaerobic composting process. Unless you happen to live in one of the few regions that actually have people separate out different types of waste products properly.

Don't plants take oxygen and release CO2 at night?

YES! Many websites recommend having plants in the sleeping room to produce O2. Plants actually consume O2 and produce CO2 at night, through not very much.

I sleep terribly at home and I am trying out to find out why. Two people and a dog in a room should not be an issue if the window is a little bit open.

you might want to consider temperature as a possible culprit. a lower temperature is a signal to the body to curl up and sleep, and a consistently cool (relative) temperature keeps you in that state. when we wake up, our bodies ramp up our metabolism/temperature to rouse us out of slumber. i know i'm ready for sleep when i impulsively reach for the sheets. with two people, a dog, and only a cracked window, the temperature might be rising above your sleep signal during the night (i wake up often in the middle of the night and can literally feel the heat rising as i gain consciousness).

They do and they don't. The net result of a growing plant is the absorption of CO2 and H2O to create O2 and various hydrocarbons, oxygen and plant matter. The carbon is fixed in the body of the plant. But i did mention grow lamps. Keep them lit and there is no night.

Plants still need to use the glucose, though. It's misleading to say that plants produce CO2 at night (since they produce it all the time); rather, they become a net CO2 producer at night because they're not offsetting it with photosynthesis.

I'm not convinced that grow lamps are an effective way to offset that, since photosynthetic efficiency is fairly low (3-4%), and the electricity for the lamp has to come from somewhere. Not to mention that lamps (even LEDs) are also fairly lossy. I'm also not convinced that's even worth optimizing.

This is about indoor air pollution. I assume the coal-fired power plant is at least not in the same building.

It is simply not feasible to lower co2 in a space with a few plants. Ventilation is the only method that works.

This is trivial to test. Just get a monitor, walk into a room with plants, close door, and start breathing. Check change in co2 after 15-30 min.

Vent the room, remove plants, repeat. Results should be equivalent.

Plants store co2 by growing. They do not grow quickly enough to deal with emissions from your breath.

To put a number on it, you exhale ~2.3lb of CO2 a day. You should also consider that much of a plants mass is water, so it would require a significant amount of plant matter to scrub the air.

I once did the math, and found that an algae tank can theoretically offset a person’s entire CO2 emissions but that it would require a large external tank and I was living in an apartment at the time.

There have been studies on indoor plants and air quality. The most well-known of which, I believe, was the NASA Clean Air Study [0]. The study suggested 1 plant per 100 sq. ft. but a space station obviously isn't the same thing as a dwelling.

[0]: https://en.wikipedia.org/wiki/NASA_Clean_Air_Study

That’s air quality, not co2. Air quality usually means particulates and VOCs.

Oof, you're totally right. Thanks for the correction!

Once you have the carbon in biomass, what do you do with it? Dry it out and heat it enough to make biochar?

Very good question. I had two avenues in mind, fungus and compost.

I’m definitely on team climate change but this just feels alarmist to me.

I don't think teams and feelings are useful tools for addressing physical problems.

Yeah, what happened to being solution-oriented?

It's odd how on HN you're not supposed to be negative of anything technical even if it's flaming crap, but also at the same time you're also supposed be assuming certain doom when it comes to climate change. How about we try to solve the technical problem at hand?

I don't understand what you're trying to say. The paper just observes that outdoor and indoor CO2 concentrations are related, and that high CO2 impacts cognition. Therefore increasing CO2 in the atmosphere has an impact on indoor cognition. What is the problem with that? Why is it "flaming crap"?

> Why is it "flaming crap"?

You 100% misread my post. I did not claim the article was "flaming crap". Please re-read it, this time reading every word.

I'm sorry, English is not my first language. I did in fact read every word in your post, but still don't understand it. Can you maybe rephrase it? I am pretty sure that this discussion here is not about climate change, but about the effects of higher CO2 concentrations in the atmosphere, on CO2 concentrations indoors.

Is there anyone opposed to trying to solve the problem? I don't understand this dichotomy you're trying to illustrate.

It's a comment in general on the discourse regarding climate change here.

I agree. We're at 412 ppm outside and there is a long way to go before indoor levels are an environmental issue rather than an HVAC one.

> there is a long way to go before indoor levels are an environmental issue

Well of course. It's right there in the title of the article "...by the end of the century."

That doesn't make it uninteresting to consider given current trajectories.

Correct me if I'm wrong but that graph they show compares averaged numbers over hundreds of years or even thousands of years, with year over year numbers once we started measuring this regularly the last +100 years.

This seems just straight out disingenuous to say the least unless I am missing something or is this kind of misrepresentation the new standard for research papers today?

Perhaps but that graph has little to do with their argument. Their argument is simple. If CO2 levels go up its going to make indoor CO2 levels worse. At some point this causes cognitive impairment.

It actually has a lot given that they are saying IF CO2 levels goes up to a certain level at the end of the century. They are using that graph as one of the reasons for why it's likely to go up.

This is their conclusion

"We conclude that indoor CO2 levels may indeed reach levels harmful to cognition by the end of this century, and the best way to prevent this hidden consequence of climate change is to reduce fossil fuel emissions. Finally, we offer recommendations for a broad, interdisciplinary approach to improving such understanding and prediction."

That's a big if especially since one of the reasons they believe it might increase to those levels is exactly this mix of averaged measurements and year over year.

Keep in mind the IPCC models range for nothing to worry about to the world is going under.

With regards to the CO2 levels having an impact on our cognitive abilities at the end of the century thats also a lot of speculation and a lot of assumptions.

This is not science this is speculation. Interesting but so filled with assumptions and guesses and speculation about what might happen in 2100.

And if that wasn't enough they just straight out claim the have the solution which is hindering fossil fuel.

This is just activism put into research format from what I can see.

You're confusing the effects of CO2 on climate (which you might argue are not too bad if you enjoy playing russian roulette), with the concentration of CO2, which we can measure extremely accurately and for whose increase the mechanism is very well understood: We burn carbon, it ends up in the atmosphere as CO2, increasing the concentration there for a long time. We also understand the impact of CO2 on cognition very well, because we can simply run experiments.

I don't think I am.

The causality of the article is.

Outdoor CO2 might be rising dramatically > dramatically rising outdoor CO2 leads to dramatically rising indoor CO2 > too high a concentration of indoor CO2 might have an impact on our cognitive abilities.

That's not the worst part of that paper the worst part is that they then just throw in things like this:

"The best way to prevent indoor CO2 levels from reaching levels harmful to cognition is through reduced fossil fuel emissions."

What about better ventilation? Just like we do with a lot of other things today. But no instead they just go for the most extreme recommendation based on absolutely nothing.

Keep in mind we are talking at the end of the century.

I don't understand how anyone can read this and think this is quality research.

> Outdoor CO2 might be rising dramatically > dramatically rising outdoor CO2 leads to dramatically rising indoor CO2 > too high a concentration of indoor CO2 might have an impact on our cognitive abilities.

Are you really claiming there is some uncertainty whether the burning of fossil fuels will actually raise CO2 levels of the atmosphere? I have thought that the discussion is whether the rising CO2 causes global warming or not.

And if we agree that burning the fossil fuels increases CO2 in atmosphere (forget the damn global warming, we are not talking about that) Do you claim that there is no reason to believe that the indoor CO2 will also rise? I hope you understand that kind of claim to be so weird that I would expect you to elaborate a bit more why you think that would not be the case.

Finally, whether the increased CO2 actually has any effect on cognitive capabilities, that is of course the main topic in the discussion here. I have no further comments on that one.

I am claiming that the research paper is not about cognitive capabilities (as that is taken for granted in the headline) but about fossil fuels effect on CO2 hence the title of the paper.

"Fossil Fuel Combustion Is Driving Indoor CO2 Toward Levels Harmful to Human Cognition"

If it was just about CO2 there would be no need to include fossil fuel combustion unless of course they know exactly how much CO2 is caused by fossil fuel combustion and how much is natural variation. There is no conclusion on that which is why you don't find an actual number of how much humans affect.

It's one thing to talk about CO2 levels and it's affect on human cognition, even that is not conclusive as is also obvious when you read the paper. But they go way way further to conclude that if we want to avoid that we should decrease fossil fuel use.

On what basis do they do that? No one knows how much is driven by humans and how much is natural

Do they have any evidence that; 1) that's without consequences, 2) it's the only way to deal with increasing CO2 if if it is harmful.

This is not research this is mixing together a bunch of different assumptions and using CO2 effect on cognitive abilities to talk about fossil fuel.

It doesn't seem hard to me to get at least a good ballpark estimate on the amount of CO2 we put into the atmosphere, say in the last 50 years. We know roughly how much coal and oil and gas we've burnt so far. Calculating how much the atmospheric concentration changed from that amount is easy enough. I'm sure someone did the math and would've published a paper about it if it turned out that human activities don't account for most of the CO2 concentration change. That would be kind of a big deal.

yet we dont have a ballpark number that says how much is human made and how much is natural. It doesent exist even in the IPCC report. You are welcome to prove me wrong.

I think this satisfies your desire for a "ballpark number"

https://ourworldindata.org/contributed-most-global-co2

Come on. You're just putting your head in the sand and pretending the sand is the real world.

That talks about countries contributing relative to each other NOT relative to natural. Please point to the number. It's not there because it doesn't exist because we don't know.

And let me put it like this. If you know the number send it to the nobel committee and you would be getting one.

It is pretty uncontroversial that CO2 increase in the atmosphere is almost all from human activity, and that a large part of that comes from burning fossil fuels. For example the US EPA website says:

https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...

Human activities are responsible for almost all of the increase in greenhouse gases in the atmosphere over the last 150 years. The largest source of greenhouse gas emissions from human activities in the United States is from burning fossil fuels for electricity, heat, and transportation.

and there is a link right on that paragraph to the IPCC report. Given the current EPA director, you might expect that to have been removed if there was any controversy about it.

And there are multiple lines of evidence to indicate fossil fuels are the major source, including carbon isotope ratios:

http://www.realclimate.org/index.php/archives/2005/06/how-mu...

Finally, if there was any doubt about it you could be sure the oil companies would be trumpeting it.

So in other words. You can't give me a number, not even a ballpark number. Why do you think that is? Why isn't it important to you if it's 10% or 51% or 99%?

The EPA quote clearly implies that for the US it is > 50%.

The realclimate article says: "the rise in atmospheric CO2 is entirely caused by fossil fuel burning and deforestation". So then the question is what is the ratio between those two sources. Quote here says ~10% of total is from tropical deforestation:

https://www.climatecouncil.org.au/deforestation/

So ballpark figure is 90% from fossil fuels? The exact number doesn't matter for the basic argument of the paper though, as long as it is the vast majority of the source.

ask yourself why they cant be precise

Just by following references in the Wikipedia about the carbon cycle I found this book chapter https://scihub.wikicn.top/https://doi.org/10.1016%2FS0070-45... that contains numbers (and error bars), alas from 1985. I'm confident that our knowledge about the carbon cycle has improved since then, given the amount of research climate change has gotten in the last thirty years.

Yes it's from 1985 and no it doesn't actually give a number either.

The fact that you can't find it and have to go to 1 article which isn't even giving you that number, should tell you that maybe you haven't gotten all the facts here.

This is exactly what started my journey from worrying about the climate to understanding it to realizing the base for all this is much much much fragile and much much much more politisized.

I spent about 20 minutes looking for that reference. I'm sure an actual climate scientist could provide you with a better reference.

Page 450 has a table. Historic CO2 concentration: 280ppm, "current" concentration 341ppm: a 21% increase. From that and the 60 * 10^15 moles C in the atmosphere in 1982 we can deduce around 50 * 10^15 moles C in 1800 in the atmosphere. That seems to be in the right ballpark of 14 * 10^15 moles of emissions from fossil fuels: not all of the carbon ends up in the atmosphere, e.g. some is dissolved in the ocean. Certainly the difference is not large enough (and doesn't have the right sign!) to support the theory that man made carbon dioxide didn't contribute the majority of the extra carbon in the atmosphere.

Increased CO2 in outdoor air both increases the baseline CO2 in indoor air and reduces the efficiency of ventilation (because the replacement air has higher CO2 too). The math is in the paper and several other comments, but if you passed high school you should be able to derive the result yourself.

You are missing the point. You are assuming all their assumptions are correct and apparently as the only person in the world you know how much human made emissions contribute to the total CO2 levels. As I wrote in another post. Write the Nobel Price committee if you know and you will be famous.

Edit:

"This is a complex problem, and our study is at the beginning. It's not just a matter of predicting global (outdoor) CO2 levels," he said. "It's going from the global background emissions, to concentrations in the urban environment, to the indoor concentrations, and finally the resulting human impact. We need even broader, interdisciplinary teams of researchers to explore this: investigating each step in our own silos will not be enough."

https://www.news-medical.net/news/20200421/Atmospheric-CO2-l...

If this is what you call certainty we have different standards of what is required to call something scientifically proven.

For the problem at hand it does not really matter if the carbon dioxide in air is from combustion, or put there by wizards who want to destroy America. In my personal opinion it's a huge logical leap to assume that fossil fuel use just doesn't add to carbon dioxide in air, and regardless of other sources, this is one source we can control.

Anyway, what matters is the result C = G/Q + C_out (see how it applies to all concentrations, not just carbon dioxide). Before it there is a differential equation and I know those are scary, but the steady state solution should be easy to understand. Solve for Q (ventilation) and you'll see why adding ventilation helps less and less with increased C_out.

Nothing scary about it you are confusing two things.

In 2100 we will be able to suck out CO2 even if that was a problem which isn't even established yet.

The math is the math, it's the premise that's wrong.

> In 2100 we will be able to suck out CO2

Citation needed.

> even if that was a problem which isn't even established yet.

Could you explain what isn't even established yet? So far it looks like your belief system prevents you from understanding any physics or chemistry where the results do not fit your values. You might want to look into that or maybe present a new system that explains other observations but where carbon dioxide behaves in a way that is your liking.

I had thought that something pretty undeniable was that burning fossil fuels increases the CO2 in the atmosphere. Most climate arguments are around the level of impact, if there's impact, if it's worth the cost of mitigating or how to/who should actually make a change. I've never seen a disagreement on the point of "burning fossil fuels releases co2".

Neither have i seen disagreement there. The point is that the graph is used to claim that we will get to these levels and that combustion is the reason we will reach them in 2100 and that the solution is to reduce fossil fuel combustion.

The other comment is right, the graph has little to do with the argument that indoor levels are important (and one of our ways of combating climate change has been to make houses have less ventilation, increasing indoor levels). I would like to add that every point on the year over year numbers is higher than the highest averaged numbers. It would then follow that the average will also be higher.

That's not my point. The point is that the article claim that rising CO2 levels are likely based on the graph which will lead to increased indoor co2 which might lead to impaired cognition at the end of the century.

Thats one hell of a long set of assumptions not a single one of them demonstrated scientifically and even if it was true at the end of the century we will be able to deal with CO2 through ventilation just like we improved our indoor climate when we didn't burn open firesplaces inside and got ventilation systems and gas or electricity instead.

Again if this mishmash is considered serious research it's doesn't bode well for our future.

Edit: Instead of just downvoting me, why not show where I am wrong here. I am open to argument, there might have been things I have missed but on the face of it, this is an extremely biased and sloppy research paper and frankly nothing but pure speculation.

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