Removing CO2 from the Air? (aside from Calcium Hydroxide)

Discussion in 'Chemistry' started by kwhilborn, Apr 11, 2007.

  1. Roman Banned Banned

    Messages:
    11,560
    Grow more green things.
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. one_raven God is a Chinese Whisper Valued Senior Member

    Messages:
    13,406
    Exactly!
    It seems to me there does not need to be any "device" to do such a thing.
    All we need to do is cut back pollution, re-establish lost jungle acreage, live more sensibly and let the plants do the rest.

    Am I missing something here?
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. Nasor Valued Senior Member

    Messages:
    6,221
    I googled around for numbers and did a quick calculation. There is about 3*10^18 g of CO2 in the air. So if it takes 390 kJ/mole to turn the CO2 into C and O2, and we wanted to reduce the amount of CO2 by 1%, that would take around 2.7*10^20 joules. If we reduced it by 1% over the course of a year, that would require 8.4 terrawatts of power, which would be about half of the total electricity consumption of the world.

    Remember, the fact that CO2 has so much less energy than solid carbon and oxygen is the very reason that we use it for fuel in the first place!
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. one_raven God is a Chinese Whisper Valued Senior Member

    Messages:
    13,406
    We use CO2 for fuel because it has little energy?
    I don't get it.
     
  8. orcot Valued Senior Member

    Messages:
    3,429
    It's a strong bond if it was a weak bond then it would fall apart out of itself.
     
  9. Nasor Valued Senior Member

    Messages:
    6,221
    Solid carbon (or liquid, if you prefer to burn oil) and oxygen gas have a lot of energy stored in their bonds. CO2 has relatively little energy stored in its bonds. The energy released when you burn carbon in the presence of oxygen is the difference between the energy of your starting materials (carbon and oxygen gas) and your products (CO2 gas). Since there is little energy in CO2, most of the energy stored in the carbon and oxygen gets released. If there was a lot of energy in CO2, burning carbon for energy wouldn't work as well because not as much energy would be released (since more of it would be stuck in the CO2 product).

    But if you want to go back the other way and turn the CO2 back into solid carbon and oxygen, you have to put the energy back in.

    But where are you going to put them? Remember, we're talking about 24 billion tons of CO2 being put into the atmosphere every year. You would have to plant a lot of trees.
     
    Last edited: Apr 12, 2007
  10. kwhilborn Banned Banned

    Messages:
    2,088
    The Moss idea, though inspirational would only touch the problem. The paper I read and posted a link to in #9 calculates that 3/4 of the worlds oceans would need to be covered in seaweed to touch natural co2 sequestration.

    In line with READONLY's idea. Perhaps it is possible to BREED a new form of plant that loves photosynthesis. Choosing a plant that already is high performance and raising them in high carbon environments, etc. Help out evolution a bit.

    The idea of requiring energy to sequester co2 could be solved in several ways. Giant Towers (twice the size of the cn tower); also mentioned in the above link, would create high speed wind tunnels in the centre. I believe this idea was proposed for and could double as an energy source.

    They are already experimenting with co2 dumping in the oceans, with co2 removed from natural gas.
     
  11. Nasor Valued Senior Member

    Messages:
    6,221
    Yeah, but the point is that the amount of energy needed to sequester a meaningful amount of CO2 is on the same order as the energy that the world is getting from the CO2-producing processes in the first place. If we had a way to generate that much energy cleanly, we could just use the energy directly and stop putting carbon into the atmosphere.
     
  12. Read-Only Valued Senior Member

    Messages:
    10,296
    Yep, you're missing something.

    Please Register or Log in to view the hidden image!

    It's no different than your idea about the moss on the roof. Once all the jungle, etc. reaches maturity, it dies and the CO2 it extracted from the air goes right back in again as the plants die.

    Granted, it would initally store more than it returns but that's only for a limited number of years - then you're right back where you started. Gained only a very, very little and not enough to make any difference at all.
     
  13. one_raven God is a Chinese Whisper Valued Senior Member

    Messages:
    13,406
    But the jungle is not somethign that grows to maturity and dies like a single tree.
    Properly taken care of, the jungle will last for many milennia.
    And if we are putting less CO2 in the air, and less pollutants in general, and growing more plants (such as on roofs of buildings, where there is currently asphalt and other manufactured materials) will teh balance not turn?
     
  14. Read-Only Valued Senior Member

    Messages:
    10,296
    The jungle is like a million trees (and ferns, vines, etc.) that grow to maturity and die to be replaced by an equal number of the same. You can't possibly get it to hold more carbon unless the jungle grows in area - and that's not about to happen.

    Why do you suppose all the jungles and rain forests were cut/burned in the first place? For the timber, yes, but mostly for the cleared land that people wanted. It's not about to turn around the other way except in very small, isolated protected areas.

    It's a very simple thing, Raven. An acre of land will only support so much vegetation before growth and death reach an equlibrium. And when that point is reached (fairly quickly, too), there's just as much CO2 leaving that acre as is being absorbed by it. Therefore, we've gained nothing.
     
  15. kwhilborn Banned Banned

    Messages:
    2,088
    The wind tunnel creates wind through natural processes when the structure is in place. The removal could be by bubbling this wind through Calcium Hydroxide. There is NO energy used. In fact these wind towers could produce "clean energy". (link to website earlier)

    Even if energy was used to power wind through heated or cooled parts, a machine built specifically for removing large amounts of carbon would produce the tiniest fraction of what it is removing.

    "trees are not enough" (all rights reserved for use of this slogan).lol
     
  16. Read-Only Valued Senior Member

    Messages:
    10,296
    Major, major flaw there, Kwhiborn - it would take a TON of energy to produce all that calcium hydroxide. The stuff simply isn't found in nature. And there's a lot of logistics involved that you haven't even begun to consider that also require energy, besides the production of the calcuim hydroxide - like mining, milling, transporting, etc.
     
  17. kwhilborn Banned Banned

    Messages:
    2,088
    I see your point. So the smart money would have to go where the the most efficiently produced co2 sequestration chemicals could be produced.

    Transportation/mining/production. Good factors. Another flaw in the wind tunnel theory would be that the liquid end would cork it up.

    Assuming there is a co2 crisis (conflicting theories and all), what would your solution be? Or should I start burying bottled water in my fields.
     
  18. Read-Only Valued Senior Member

    Messages:
    10,296
    It can be solved. The first and foremost thing is to begin at the beginning, so to speak - where most of the CO2 is originally produced. In the majority of the world (including the US, China and other industrial nations) is our power generating stations. The vast majority of them burn coal, to a lesser degree natrual gas, and even lesser, oil. It would require expensive equipment but a great deal of it could be caught right there.

    As for the rest of it in the air (from cars, etc.), some very fast growing vegetation, like algae, could catch it directly from the air. It would then be separated from the water and then stored in deep, abandoned mines (old salt mines are ideal) before it begins to decay. It would remain there forever and would never get back into the carbon cycle.

    The absolute final - and lasting - approach is to convert energry production to nuclear. First, it would put an end to the current greatest sources of CO2. Secondly, it could be used to make electrical vehicles a true reality and end a very large part of the dependence on oil.

    I do realize that there's still the matter of disposing of the nuclear waste but that could be solved with a concerted effort that wouldn't require as much funding as is currently being pumped into the system in the form of subsidies for the production of ethanol from corn.
     
  19. kwhilborn Banned Banned

    Messages:
    2,088
    Algae. Hmmm. Nuclear energy scares the hell out of me when I think of it in dictatorship countries, I think we'd need to clean all of the air in civilized countries. Would not Algae need still unchlorinated water. Sounds a little unsanitary. mosquitos, etc. Interesting ideas.
     
  20. one_raven God is a Chinese Whisper Valued Senior Member

    Messages:
    13,406
    That's exactly what I am talking about.
    I think it is preferable to all the other suggestions I am seeing here.
    I also think it is possible to have a great deal more greenery growing in populated areas than there is now.
    There is also the possibility of reforesting many, many smaller deforested areas.

    We already know what works, it works well, it is clean, it has no toxic chemicals to have to dispose of, it doesn't require nuclear power, it doesn't require huge construction projects...
    Rather than trying to "fix" our mistakes and make invent a machine to make reparations, we should learn from our mistakes create less polution, and treat nature with greater respect.
     
  21. leopold Valued Senior Member

    Messages:
    17,455
    yes. with genetic engineering you can develop a process based on photosynthesis.

    maybe even use the process in combination with water to produce gasoline.
     
  22. MetaKron Registered Senior Member

    Messages:
    5,502
    Hemp seeds can be scrounged in many places. Efforts to eradicate hemp by harvesting and burning it in the fall have been especially effective at scattering the seeds and planting the next harvest, and this is a very good carbon sink, able to sequester several pounds per plant.

    I don't think that it's really necessary to do it, but if it was, consider the fact that merging the plant waste with the soil keeps the carbon out of the atmosphere for many years, like in peat bogs. Converting it to plastic also works.
     
  23. Positron Agony: Not all pain is gain Registered Senior Member

    Messages:
    171
    A device that could remove carbon from the air, if not already engineered, would not take long to come upo with. The problem of course lies in the fact that we put out so much CO2 it would be so difficult to counteract it. I suppose, however, that if we spent a lot of money making these machines, we would be smarter by then and not putting out as much.
     

Share This Page