Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Efficient method to capture carbon dioxide from the atmosphere

helsinki.fi

Post reply on HN
Print view View original

161–170 of 349 posts

Re: Efficient method to capture carbon dioxide from the atmosphere

#161

Post by mapt »

malfist wrote: post #90
lokar wrote: post #74

Earlier quoted context omitted.

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

I find it extremely unlikely that homes are routinely at 2000-3000 ppm. That is extremely high and would mean multiple people in a small area with no air exchange for a long while. I monitor my indoor co2, but don't take any action because it's extremely rare to be above 700 or 800. I can only remember a handful of times its reached 1k ppm. And my house should be prime candidate for co2, it was built during the era o…

It happens a lot in efficient houses that don't cover all bases with HVAC (the vast majority of recently built houses), where the room door is closed, maybe the vents are not ideal, and there is usually no makeup air or forced air ventilation other than a furnace intake.

This change in scientific literature actually causes a ~quadrupling of recommended airflow ratios for tight homes versus ASHRAE's previous guidelines, putting strong emphasis on an ERV. Previously, ventilation needs tended to be dominated by air quality and smell, by humidity buildup, or by theoretical house parties that maxed out the system.

This ventilation adds capital expense, but it's substantially more controllable and significantly cheaper in the long run in colder climates than 'just open a window' or 'just don't build the house so tightly sealed'. Reserve the operable window for the aforementioned house party, which is out of a reasonable design envelope.

Re: Efficient method to capture carbon dioxide from the atmosphere

#162

Post by LargeWu »

nine_k wrote: post #144
LargeWu wrote: post #137

Earlier quoted context omitted.

I've wondered if capturing carbon emissions from industrial-scale compost facilities would be a net positive. It would have the added benefit of the carbon initially being captured by natural organic processes (i.e. growing food), so it avoids the problem of the energy requirements from trying to just pull carbon from the ambient atmosphere. I don't know if this is feasible but I haven't seen any research on it.

What we need to offset the last 3 centuries of coal use is to reverse the process. Plant large amounts of trees, cut them, burn the hydrogen part of them, producing char and reclaiming some energy, then bury the resulting coal back in the abandoned coal mines.

Yeah, that too. There's not going to be one single solution, the problem is just too big for that. The idea with compost is that growing plants for food and dealing with the waste and excess (which is substantial) is something we're already doing, so can we tack carbon sequestration on top of that

Re: Efficient method to capture carbon dioxide from the atmosphere

#163

Post by henearkr »

bobfromhuddle wrote: post #113
jiehong wrote: post #68

Earlier quoted context omitted.

Could something like this be used to make cement? Imagine capturing CO2 to turn it into cement, used for constructions. Pardon my ignorance, though.

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

Do you know ferrock?

It is a kind of cement that uses CO2 to cure.

Re: Efficient method to capture carbon dioxide from the atmosphere

#164

Post by henearkr »

jiehong wrote: post #68
condiment wrote: post #45

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…

Could something like this be used to make cement? Imagine capturing CO2 to turn it into cement, used for constructions. Pardon my ignorance, though.

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).

Re: Efficient method to capture carbon dioxide from the atmosphere

#165

Post by sokoloff »

yodon wrote: post #37
cyphertruck wrote: post #2

Economics rules everything. How much does this cost vs simply planting trees, when the value of harvesting the trees is included? Since tree farms are generally profitable, and wood is expensive, it seems this method is likely to be economically less efficient.

>Economics rules everything Physics rules everything, once you start trying to run at scale. The density of carbon per unit volume in solid materials of interest doesn't vary that much, whether you sink it in trees or in exotic materials like diamonds. That means you can calculate the volume of material required so sink a desired amount of atmospheric carbon. If you want to have a measurable impact on the atmosphere,…

If we pull this off, I would not expect people 500 years from now to undo it.

Re: Efficient method to capture carbon dioxide from the atmosphere

#166

Post by codeulike »

progbits wrote: post #156
ifwinterco wrote: post #154

Earlier quoted context omitted.

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

https://www.sciencedirect.com/science/article/pii/S036013232... > In this study, a systematic review and meta-analysis of fifteen eligible studies was performed to quantify the effects of short-term CO2 exposure on cognitive task performance. > The complex task performance declined significantly when exposed to additional CO2 concentrations of 1000–1500 ppm and 1500–3000 ppm

Additional

Re: Efficient method to capture carbon dioxide from the atmosphere

#167

Post by marcosdumay »

three14 wrote: post #150
marcosdumay wrote: post #87

Earlier quoted context omitted.

> you're talking not about making a pile of stuff but about making a mountain range that's a mile high and hundreds of miles long. Just to put it into numbers, wikipedia has the total amount of CO2 on the global warming page, if we assume it's in a 2 kg/l substance it totals to around 180 km^3.

But if you release the O2 and convert it into diamond, then by my highy-suspect back of the envelope calculations, it'd be a diamond that would fit into one square kilometer, 87 meters high. It would make quite the tourist attraction.

My number is without the O2.

It's a literal mountain chain of plastic. We do have uses for it, but it's a lot.

Re: Efficient method to capture carbon dioxide from the atmosphere

#168

Post by carbonguy »

marcosdumay wrote: post #87
yodon wrote: post #37

Earlier quoted context omitted.

>Economics rules everything Physics rules everything, once you start trying to run at scale. The density of carbon per unit volume in solid materials of interest doesn't vary that much, whether you sink it in trees or in exotic materials like diamonds. That means you can calculate the volume of material required so sink a desired amount of atmospheric carbon. If you want to have a measurable impact on the atmosphere,…

> you're talking not about making a pile of stuff but about making a mountain range that's a mile high and hundreds of miles long. Just to put it into numbers, wikipedia has the total amount of CO2 on the global warming page, if we assume it's in a 2 kg/l substance it totals to around 180 km^3.

To put it further into numbers -

1). Wikipedia does have a citation [1] saying 2,450 gigatonnes of CO2 have been emitted by human activity, of which 42% stayed in the atmosphere and 34% dissolved in the oceans, with the rest already sequestered by plant growth and land use. As we start to pull CO2 out of the atmosphere, it will begin to be emitted from the oceans as well; therefore, let's assume we have to recapture all excess atmospheric and oceanic CO2:

:: 2450x10^9 tonnes CO2 x .66 fraction to sequester ~= 1.6x10^12 tonnes CO2.

2) Let's convert the CO2 to something more stable for long-term storage: HDPE.

- Convert mass of CO2 to mass of carbon:

:: 1.6x10^12 tonnes CO2 x 12/44 mass fraction of C in CO2 ~= 4.4x10^11 tonnes C

- Convert mass C to mass HDPE; assume HDPE is effectively (CH2)n. Then:

:: 4.4x10^11 tonnes C x 14/12 mass fraction CH2 to C ~= 5.2x10^11 tonnes HDPE

3) That's a lot of plastic! How much volume? Wikipedia says HDPE is ~930-970 kg/m3; let's be conservative again and take the low figure:

:: 5.2x10^11 tonnes HDPE x 1.0/0.930 m3 per tonne HDPE ~= 5.5x10^11 m3 HDPE

4) Those are cubic meters; how about cubic kilometers?

:: 5.5x10^11 m3 x 1.0/1.0x10^9 km3 per m3 ~= 5.5x10^2 km3

In other words, if you turned all the [excess potentially climate-change impacting] CO2 that humanity has emitted since 1850 into plastic (a process that would certainly emit a large additional CO2 fraction given the industrial buildout required) then we'd end up with about 550 cubic kilometers of the stuff. Coincidentally, that's about the volume of Mount Everest according to an intermediate calculation in [2].

So, a mountain of carbon: more than a pile but less than a mountain range.

[1] https://en.wikipedia.org/wiki/Carbon_dioxide_in_the_atmosphe...

[2] https://www.quora.com/What-would-the-estimated-weight-of-Mou...

Re: Efficient method to capture carbon dioxide from the atmosphere

#169

Post by ifwinterco »

progbits wrote: post #156
ifwinterco wrote: post #154

Earlier quoted context omitted.

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

https://www.sciencedirect.com/science/article/pii/S036013232... > In this study, a systematic review and meta-analysis of fifteen eligible studies was performed to quantify the effects of short-term CO2 exposure on cognitive task performance. > The complex task performance declined significantly when exposed to additional CO2 concentrations of 1000–1500 ppm and 1500–3000 ppm

It looks like there might be a very small effect starting at around 1000ppm but so small that many studies find no difference at all, and reliable effects are only noted at 3000ppm or more.

So we're a long way from needing to scrub co2 from the atmosphere to get any work done

Post reply on HN