CO2 Sequestration

  1. Andrew Mason

    Andrew Mason 6,864
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    There is a big move in the fossil fuel industry, particularly coal, to solve the problem of green-house gas emissions by sequestering CO2 in the earth in geological formations that are believed to be stable. This gives rise to a number of questions to which I would like to see comments, particularly from regular posters to this board.

    1. Is burying CO2 really a reliable way to prevent it from entering the atmosphere? Since a concentration of 5% CO2 will kill a human being, and since CO2 is heavier than air, a release of CO2 from one of these storage seams could be an environmental and human disaster.

    2. Since we would be burying an O2 with each C, we would be permanently depleting the atmosphere of Oxygen as well. In the normal carbon cycle, this O2 would make its way back into the atmosphere eventually. Not so if it is buried. What are the environmental implications of this? I have not seen any mention of this anywhere.

    AM
     
  2. jcsd
    Earth sciences news on Phys.org
  3. What can I say.

    First of all, there are a number of people, who still think that also greenhouse gasses should follow physical laws and due to saturation effects an increase of global temperature due to a higher concentration of CO2 is very small. Therefore the current warming should have another cause, be it anthropogenic or natural. Possible candidats are:

    - decadal scale changes in cloud cover (albedo) wich are actually measured.

    - decadal to century scale solar activity governing cloud forming, (phytoplankton seems to do the same: http://www.physorg.com/news82115682.html )

    - High troposphere water vapor due to aviation

    - Albedo land change.

    Next, CO2 of course is the most basic building block of life, the fuel for photo synthesis. As the element carbon is cycling in the biosphere, large amounts are semi permanently tied to calcium oxide forming limestone rocks. Therefore the amount of available carbon tends to decrease until some catastrophe (Vulcano or so) recycles the limestone back to CO2 and calcium. So carbon dissapears naturally and in doing so reduces the available biomass. Therefore, speeding up that process by sequestering CO2 will once be known as the singlemost stupid action ever.

    But it's happening already for years on a smaller scale. It's used to re-pressurize oil and natural gas fields, and increase the production of thouse fossil fuels. Oil industries will probably have nice dreams of doing that for their own production process and being paid for it as well.

    I don't think that the dangers are bigger than natural releases of CO2 that happen every once and a while.
     
  4. Bystander

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    No.

    No.

    No.

    No.

    None.
     
  5. Andrew Mason

    Andrew Mason 6,864
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    So are you saying that oxygen is not removed from the atmosphere or that it is not a problem because there is so much of it?

    And why would not a release of CO2 be a concern to human safety? Is it because it would not escape quickly or because it would not result in unsafe concentrations?

    AM
     
  6. Bystander

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    I'm saying that it's unwise to marry the "all atmospheric oxygen is derived from photosynthesis" model that has become a cornerstone of grade school earth science.

    Both. There are no gas tight formations that are permeable enough to be used for storage; they'll be leaking like sieves, carbonating ground water, blowing sand in the air ten miles away, cracking foundations, and being enough a general nuisance to keep the ABA fully employed for centuries.
     
  7. Andrew Mason

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    So what is wrong with the theory that the carbon in the ground came from higher levels of CO2 in the atmosphere? What other explanation is there?

    This is an interesting comment. Data from injecting CO2 into the oil reservoirs in southern Saskatchewan shows that the CO2 increases the concentration of bicarbonate and this causes a dramatic increase in concentration of CO2 in the ground- apparently a 10 fold increase. I am not sure what this means. But if by injecting CO2 into the ground we are actually increasing by 10 fold the amount of CO2 that could leak out of the ground, I am thinking this may not be a good idea.

    AM
     
    Last edited: Nov 10, 2006
  8. LURCH

    LURCH 2,514
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    I think that most of the CO2 slated for sequestration is the same gas being released by mining and drilling, so I don't think there's much reason to fear depletion. We're not talking about taking the naturally-occurring carbon out of the air, only reducing the rate at which we are artificially adding carbon to the air.
     
  9. Andrew Mason

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    Well the idea is to use the CO2 produced by burning coal or other fossil fuels and put it into the ground rather than the atmosphere.

    AM
     
  10. LURCH

    LURCH 2,514
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    Ah yes. So the CO2 being put into the ground is the same that is being taken out of the ground and released into the air by man. So the same principle applies, the CO2 being put into the ground will not create a change in the atmosphere, it will only minimize the change that is being caused by mining the carbon and burning it for fuel.
     
  11. Andrew Mason

    Andrew Mason 6,864
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    Except that the CO2 being put in the ground includes the O2 that was taken from the atmosphere. So not only is the C being removed from the biosphere in being reinterred, oxygen is being removed.

    It appears that no one has been looking at the long term effect of removing O2 from the atmosphere.

    If the primordial atmosphere was rich in CO2, as the current scientific consensus seems to be (I don't know how else one could explain the enormous amount of fossil carbon in the earth), our current abundance of O2 comes from the capture (and subsequent interrment) of the C and the release of the O2 from the CO2into the atmosphere (by photosynthesis).

    If we were to burn all of the fossil carbon and introduce the CO2 back into the atmosphere we would recreate the primordial atmosphere. But if, instead of releasing it into the atmosphere, we were to sequester the CO2 in the earth, we would be reducing the total quantity of gases (ie oxygen) in the atmosphere. I don't see how this can be a sustainable solution.

    AM
     
  12. Bystander

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    Two tons of atmospheric oxygen per square meter of earth's surface implies how much reduced carbon (methane, elemental carbon, cellulose) per square meter? The biological origin of oxygen in the atmosphere gets a little tough to defend once you do the mass balance. Explains the amount of work being done on atmospheric evolution. There are no conclusions from which to go leaping to conclusions.
     
  13. Andrew Mason

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    Two tons of O2 per m2 implies that there could have been a little less than 3 tons of CO2 per m2. Is that not plausible?

    AM
     
  14. Bystander

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    Where's the carbon?
     
  15. Andrew Mason

    Andrew Mason 6,864
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    Now? It is in the earth and oceans.

    AM
     
  16. Bystander

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    Where's the reduced carbon?
     
  17. Andrew Mason

    Andrew Mason 6,864
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    If by reduced carbon you mean chemically reduced carbon, it is in the hydrocarbons buried in the earth and seabeds.

    AM
     
  18. Bystander

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    Half ton of methane, 2/3 ton of elemental C, to 2 tons cellulose per square meter? I say again, "Where is it?"
     
  19. Ivan Seeking

    Ivan Seeking 12,535
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  20. Bystander

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    "Current best guesses suggest that maybe 500 to 2000 gigatonnes of carbon may be stored as methane clathrates (5-20% of total estimated reserves). Some estimates are as high as 10,000 gigatonnes." That takes care of 4% --- now, where's the rest?
     
  21. my chemistry might be rusty, but when you mix CO2 and water, you get acid, (sulfuric i think), (or soda water).

    acid melts, or dissolves lime stone, (alkline).

    so you geosequestrate your co2, a bit of water seeps in, turns to acid, melts the rock, and releases the CO2 !. Soon or later.. !!!

    im from a region, and country thats makes HUGE $$$ mining and exporting coal, and natual gas.
    but i believe that if fossel fuels were outlawed tomorrow, or general consumption and power generation, within 6 months, we would have electric cars, and alternative power systems, and reusable fuels to meet our requirements.

    there is little incentive to use science and technology, when its just SO CHEAP to dig up and burn coal at 31% efficiency.
    releasing co2 thats been stored in the ground 100% safely for millions of years.

    its 2006 now, surly we can do better than dig up rotten plants and animals, liquify it or crush it up and burn it as our primary sources of energy !!. future generations will look back at our generation and ask "what were we thinking".

    or do we just keep going until we run out, or we have runaway global warning. ? we cant re-run the experiment if it fails.
    so you want to make sure your right, for us all !!
     
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