Why can't we just recycle polluted air?

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just a question,

I mean, burning trash causes polluted air.
then
why can't we just filter the polluted air, separating the oxygen and other harmful gas and release only oxygen in the air?

thus solving trash and polluted air at the same time.
 

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  • #2
russ_watters
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It's difficult/energy intensive and we don't have a place to put the harmful gasses. The atmosphere is big!

Also, these days the "harmful gas" is mainly carbon dioxide. Anti-pollution regulations have mostly curtailed the emissions of other harmful gases.
 
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It's difficult/energy intensive and we don't have a place to put the harmful gasses. The atmosphere is big!

Also, these days the "harmful gas" is mainly carbon dioxide. Anti-pollution regulations have mostly curtailed the emissions of other harmful gases.
no, I mean, gas is basically a combination of chemical formulas right,

and just like carbon is CO2
why not just split the C and O2
thus will be able to give the air the O2 it needs,
while the C will be used as well carbon metal ?
 
  • #4
russ_watters
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no, I mean, gas is basically a combination of chemical formulas right,

and just like carbon is CO2
why not just split the C and O2
thus will be able to give the air the O2 it needs,
while the C will be used as well carbon metal ?
It takes exactly the same amount of energy to split CO2 as you got from making it. You're talking about burning and then unburning it.
 
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  • #5
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It takes exactly the same amount of energy to split CO2 as you got from making it. You're talking about burning and then unburning it.
oh, I mean what's the purpose of the filters then ?
don't the filters also kind of block the carbon in the CO2 ?

I have seen some Factories like have some sort of filters in their chimney.
 
  • #6
russ_watters
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oh, I mean what's the purpose of the filters then ?
don't the filters also kind of block the carbon in the CO2 ?

I have seen some Factories like have some sort of filters in their chimney.
Filters can block particulate pollution like soot, but can't filter gases. But these days there isn't much soot - that's caused by incomplete burning.
 
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so the challenge today is to,
somehow be able to burn and unburn a gas.

I mean I hear the news complaining about carbon emission.
I kind of think that separating C from CO2 is easy,

didn't know the current technology for that is requires a lot of energy.
 
  • #8
russ_watters
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so the challenge today is to,
somehow be able to burn and unburn a gas.

I mean I hear the news complaining about carbon emission.
I kind of think that separating C from CO2 is easy,

didn't know the current technology for that is requires a lot of energy.
It's not a technology issue, it is a chemistry/conservation of energy issue. Running a reaction forwards and backwards creates/requires the same amount of energy. It has to - it's the same reaction.
 
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  • #9
Astronuc
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oh, I mean what's the purpose of the filters then ?
don't the filters also kind of block the carbon in the CO2 ?

I have seen some Factories like have some sort of filters in their chimney.
Filters typical trap 'particulate' matter, which can be a combination of ash, or unburned metal oxides leftover from coal or oil, and carbonaceous products. Gases would pass through the filter.

so the challenge today is to,
somehow be able to burn and unburn a gas.

I mean I hear the news complaining about carbon emission.
I kind of think that separating C from CO2 is easy,

didn't know the current technology for that is requires a lot of energy.
There are various so-called 'carbon capture' programs in which CO2 is captured at the source, i.e., at the exit of the combustion system. For example,

https://energyfactor.exxonmobil.com/reducing-emissions/carbon-capture-and-storage/
https://www.battelle.org/government...esource-management/carbon-management-services

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

In the air, CO2 is about 400 to 500 ppm, and it takes energy to compress the air and separate into constituent gases. Then what does one do with the CO2? Or rather, to what process can it be used as a feedstock? Fischer-Tropsch synthesis is one possibility, but it would be more economical to capture CO2 at the source.

Algal systems are a possibility as are reforestation, or use of forests, both inland and coastal.

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

https://qz.com/1718988/algae-might-be-a-secret-weapon-to-combatting-climate-change/
https://www.frontiersin.org/articles/10.3389/fmars.2019.00029/full

https://www.energy.gov/fe/articles/...ects-develop-algae-based-technologies-capture

Integrating Algae with Bioenergy Carbon Capture and Storage (ABECCS) Increases Sustainability
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017EF000704
 
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  • #10
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Filters typical trap 'particulate' matter, which can be a combination of ash, or unburned metal oxides leftover from coal or oil, and carbonaceous products. Gases would pass through the filter.


There are various so-called 'carbon capture' programs in which CO2 is captured at the source, i.e., at the exit of the combustion system. For example,

https://energyfactor.exxonmobil.com/reducing-emissions/carbon-capture-and-storage/
https://www.battelle.org/government...esource-management/carbon-management-services

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

In the air, CO2 is about 400 to 500 ppm, and it takes energy to compress the air and separate into constituent gases. Then what does one do with the CO2? Or rather, to what process can it be used as a feedstock? Fischer-Tropsch synthesis is one possibility, but it would be more economical to capture CO2 at the source.

Algal systems are a possibility as are reforestation, or use of forests, both inland and coastal.

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

https://qz.com/1718988/algae-might-be-a-secret-weapon-to-combatting-climate-change/
https://www.frontiersin.org/articles/10.3389/fmars.2019.00029/full

https://www.energy.gov/fe/articles/...ects-develop-algae-based-technologies-capture

Integrating Algae with Bioenergy Carbon Capture and Storage (ABECCS) Increases Sustainability
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017EF000704
it's sad that the only way to actually manage CO2 is to capture it and put it underground.

I though we could use the carbon element in the air as carbon resource =_=

wish there is a way to just split the chemical compound so we can just reuse the elements.

oh well, it's just a fantasy then.


so the real options are Economical or Geological factors.

reduce the Factories - highly unlikely as this might affect the economic output of the country.
reduce the Use of Fossil Fuels or Coal = Highly Unlikely as the world need more Energy as I can understand right now ?

add more forest - semi probable?
or just have algae farms ?
 
  • #11
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or just have algae farms ?
Is there an "e-e-c-h-c-o-h-o" in here?
 
  • #12
russ_watters
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Yes, unburning fuel is roundabout vs reducing/stopping burning fuel. It's a lot easier to stop burning fuel than it is to burn it then unburn it.
reduce the Factories - highly unlikely as this might affect the economic output of the country.
reduce the Use of Fossil Fuels or Coal = Highly Unlikely as the world need more Energy as I can understand right now ?
It wouldn't be difficult to reduce the fossil fuel usage for electricity to near zero in a couple of decades if we wanted to do it. But unfortunately there is more political capital in saying we want to do it than in actually doing it, so we won't.
add more forest - semi probable?
Yes that would be good but unfortunately it is currently accepted (again as a political choice) that burning down forests is "carbon neutral" so we're going in the wrong direction with that.
 
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  • #13
HAYAO
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it's sad that the only way to actually manage CO2 is to capture it and put it underground.

I though we could use the carbon element in the air as carbon resource =_=

wish there is a way to just split the chemical compound so we can just reuse the elements.

oh well, it's just a fantasy then.


so the real options are Economical or Geological factors.

reduce the Factories - highly unlikely as this might affect the economic output of the country.
reduce the Use of Fossil Fuels or Coal = Highly Unlikely as the world need more Energy as I can understand right now ?

add more forest - semi probable?
or just have algae farms ?
Well, to add to what Astronuc said, there are some potentials in CO2 dissociation through solar energy. In my field (Photochemistry and Coordination Chemistry), this seems to be one of the bigger projects out there.
However, I have yet to see a scalable report; it can sound good at laboratory levels but it gets impractical at industrial level. For example, to bring it to an industrial level, it usually require a synthetic method that is usually quite different from laboratory level synthesis. Whether that method is available or not depends on what exactly is going to be synthesized, but a tremendous chemical engineering would be required. Not to mention that we are also neglecting the energy and resource costs in producing the compounds.
 
  • #14
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I think any carbon capture is actually immensely impractical, due to the enormous scale we would need to achieve in order to adequately deal with the problem. It would need to exceed the current size of the oil industry, in just a decade or two.
 
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Well, to add to what Astronuc said, there are some potentials in CO2 dissociation through solar energy. In my field (Photochemistry and Coordination Chemistry), this seems to be one of the bigger projects out there.
However, I have yet to see a scalable report; it can sound good at laboratory levels but it gets impractical at industrial level. For example, to bring it to an industrial level, it usually require a synthetic method that is usually quite different from laboratory level synthesis. Whether that method is available or not depends on what exactly is going to be synthesized, but a tremendous chemical engineering would be required. Not to mention that we are also neglecting the energy and resource costs in producing the compounds.

I think any carbon capture is actually immensely impractical, due to the enormous scale we would need to achieve in order to adequately deal with the problem. It would need to exceed the current size of the oil industry, in just a decade or two.


I kind of saw this in the youtube,
I thought, only I came to think of this method haha,
There are other companies doing it already hehe.

But from the looks of it,
Looks like it's quite expensive.

Reference article: From BBC
 
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  • #16
256bits
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Yes, unburning fuel is roundabout vs reducing/stopping burning fuel. It's a lot easier to stop burning fuel than it is to burn it then unburn it.

It wouldn't be difficult to reduce the fossil fuel usage for electricity to near zero in a couple of decades if we wanted to do it. But unfortunately there is more political capital in saying we want to do it than in actually doing it, so we won't.

Yes that would be good but unfortunately it is currently accepted (again as a political choice) that burning down forests is "carbon neutral" so we're going in the wrong direction with that.
You probably, and most people do not, is that N.American earthworms, or at least quite a lot of them, are an invasive species bought in with the European settlers..

The last ice age pushed the native ones south and they are slowly creeping northwards, but the ones actually further north are the invasive species type.
( and most people would say that they are great for gardening )

But undergrowth is affected, and a consequence is less carbon capture for the forest.
Rather than being a carbon sink, the Boreal forests of Canada do become a carbon source as the earthworms move in.
https://laidbackgardener.blog/2021/01/04/earthworms-are-bad-news-for-north-american-forests/

Tree planting, as you say, is slightly political.
 
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  • #17
gmax137
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Circling back to the original post idea of burning trash
thus solving trash and polluted air at the same time
The company I work for sold a few "trash-burners" back in the late 1980s to generate electricity using municipal trash as fuel. This seemed a good idea, as many cities suffer with ever-growing landfills. I don't know if any of these power plants are still operating. Combustion generates CO2, so maybe these units have been retired.

I had a friend who worked at one of the trash burners, and he related the biggest problem operationally was the fuel stream. Municipal trash is not uniform like nat gas or coal; the trash stream is not all combustible and contains all kinds of unexpected items. The conveyor system that brings the trash to the burner was frequently jammed by stuff like grocery carts, shutting down the unit until the system could be un-jammed. Hard to believe that people toss grocery carts into dumpsters, but my friend said it happened all the time.
 
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  • #18
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burning trash causes polluted air.
then
why can't we just filter the polluted air
Kind of that what happens. But 'polluted air' is a bit broad term, and can mean very different things depending on the context. Since you brought up burning trash, the release of CO2 and H2O is acceptable, and the focus is on everything else. Trash can contain a very wide variety of materials, so you have to filter against NOx, complex organic materials: even volatile metals and Sulfur.
They are removed by scrubbing. (Source is random google find, but I've found it acceptable starting point for further digging.)

Removing the CO2 is a different topic, as the turns of the topic already proved it.
 

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