[condiment]

At current rates of emissions, we’re only about 20 years away from people needing to install CO2 scrubbers in their homes.

Soda lime, or calcium hydroxide, is the current state of the art. We use that in an anesthesia and in saltwater aquariums and in scuba rebreathers. An idealized system can capture 500 mg per gram, but in practice you only capture around 250mg/g. This outperforms the method in the article but it’s one-shot. There are interesting proposals to use this for direct capture at industrial facilities and to turn the waste material into bricks for building.

The key advantage of this new material appears to be that it can be heated and reused. That would be very valuable in an interior direct air capture use case. Think about filtering the CO2 from an office or a home to get us back to pre-industrial levels indoors.

[UniverseHacker]

I think it’s little appreciated that high CO2 levels cause cognitive impairment, and with the same amount of (often very poor) air exchange, higher outdoor concentrations can push indoor spaces to levels that cause impaired cognition and poor sleep. I’ve already been seeing this in my home, and will often open windows even when cold just to keep co2 levels reasonable. One solution that can help is an external air heat exchanger, which can exchange air with the outdoors without compromising your homes heating and cooling like an open window will do.

Noticeable cognitive impairment starts in the 700-1000ppm range, whereas it is very common for homes to reach 2000-3000ppm, especially when in a closed bedroom.

[wcoenen]

> Noticeable cognitive impairment starts in the 700-1000ppm range

The US navy failed to detect such effects in submarine crew, even at much higher levels like 10,000 ppm.

Another reason to be skeptical is that exhaled breath is 4% CO2 (40,000 ppm!). Therefore a few thousand extra ppm in the inhaled air should not make much of a difference to the homeostasis mechanisms in our bodies.

[nehal3m]

>One solution that can help is an external air heat exchanger

I have one of those, it blows fresh air in through the bedroom and sucks it back out through the kitchen (loft house, this route prevents food smells from wafting into the bedroom). Aside from just feeling fresh all year, this system also prevents mosquitoes from entering in summer while still allowing air circulation, it automatically bypasses the exchanger at night to provide cool air and it has some pollen filters installed which helps with hay fever.

So great economic return and a bunch of upsides, but it does require space for the exchanger and the ducts throughout the house.

[cassepipe]

I have been monitoring for high CO2 for a few months now. I easily find myself in the 1000 - 1400 range for some time before I finally let some air in in winter.

I have not noticed significant cognitive impairment (not saying it did not happen)

[ProllyInfamous]

My quality of sleep/life have greatly increased since installing an Energy Recovery Vent (ERV) — it exchanges outside/inside air through a membrane, which is about 60-80% efficient for both humidity and temperature re-capture (depending on fan speed).

[•] <https://en.wikipedia.org/wiki/Heat_recovery_ventilation#Ener...>

I use a Panasonic model — readily available from Big Box Retail (~$700 + $100 in vent/conduit) — which can do 20 - 60 cfm (in my 900 sqft home this can easiliy exchange the entire volume several times per day).

[ctoth]

> higher outdoor concentrations can push indoor spaces to levels that cause impaired cognition

I am somewhat skeptical of this:

https://www.astralcodexten.com/p/eight-hundred-slightly-pois...

[thangalin]

> I think it’s little appreciated that high CO2 levels cause cognitive impairment

Have you been telling representatives? Here's a letter I wrote to mine:

https://pdfhost.io/v/bRJEGptatL_climate-change

[ifwinterco]

This is a meme on hacker news that's usually stated as a fact, but I'm not sure there's any robust evidence of cognitive impairment at <1000ppm

[lokar]

Really? Wow, I try to keep my place at 500-600, without that much effort.

[deadbabe]

Ok this sounds like BS, what kind of sensor is being used to get such readings? What do you use?

[ekianjo]

> high CO2 levels cause cognitive impairment

Sounds seriously unlikely. How would this work in practice, at the level of bodily functions?

[marcosdumay]

> The ease of releasing CO2 is the key advantage of the new compound.

I have no idea why the journalist that wrote this article choose to highlight the carbon density of the sub-header. It's almost completely irrelevant for carbon capture plants.

Another clear benefit is that it's a liquid.

Today people mostly use the substances that you called non-reversible in research plants (AFAIK, all plants are research right now). They are perfectly reversible, but that uses a lot of energy.

[nine_k]

> perfectly reversible, but that uses a lot of energy

Looks like a perfect match to a solar plant, which provides basically free energy periodically. All you need is a large enough cistern to hold the liquid during night time.

[netcraft]

160F, non toxic, this already sounds like something that could feasibly be used in the home. I would already be interested in installing one. And would absolutely love to see what it would do to school performance.

The hard part is capture and disposal.

[yodon]

Do you have a citation for that 20 years estimate?

[marcosdumay]

https://gml.noaa.gov/ccgg/trends/

Extending the current exponential for 20 years, we get into the 500ppm region.

I don't think that's enough to need scrubbers.

[mort96]

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.

[netcraft]

I was also a bit skeptical, but chatgpt gave a pretty good answer I think: https://chatgpt.com/share/69553e26-ea28-8011-bc17-8658fbea4e...

Buildings with higher people/sqft could already take advantage of indoor co2 scrubbers today.

[idiotsecant]

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

Just extrapolate.

[jiehong]

Could something like this be used to make cement?

Imagine capturing CO2 to turn it into cement, used for constructions.

Pardon my ignorance, though.

[bobfromhuddle]

We don't use CO2 to make cement, we use limestone, and CO2 is the byproduct of heating the limestone to make reactive calcium.

[henearkr]

You can store CO2 and sell it to construction companies (to cure ferrock), to energy storage companies (who like to put the CO2 in huge bubbles nowadays, go figure), or to agricultural corporations (who enrich greenhouses air in CO2 to accelerate growth).

[adrianN]

You can heat definitely heat NaHCO3 to get CO2 and NaOH back. It just takes a lot of energy.

[DivingForGold]

"outperform" by only one metric too often fails usefulness. It's a one shot unless you heat the calcium carbonate to 900C, the compound in the article only requires 70C, and has quite a bit of ability to re-process CO2 absorption multiple times. Although solar ovens could reach over 900C, probably too dangerous for residential use.

[omgJustTest]

citation for the co2 scrubbers in home need?

[bilsbie]

Just to counter your extreme prediction, if co2 levels halve from here all life on earth goes extinct.

https://www.researchgate.net/post/Minimum_necessary_concentr...

[gspr]

Please stop trying to hurt every single human being with these derailments. There is no plausible mechanism by which carbondioxide levels would halve. That means you're just trying to derail the discussion by appealing to people's instincts about how fragile atmospheric composition is. Stop.

[loeg]

They aren't at risk of halving, though?

[belorn]

Comparing it to sofnolime (the more common used scrubber material for rebreathers), the cost sits around $10 per kg.

Cost will be the biggest question. A reusable scrubber need to be cheap enough that the reduce efficiency is worth it.

[29athrowaway]

Maybe we just need to make cyanobacteria that multiplies faster.