4 ms·

It's meant to be injected underground.

by uvdiv 14y ago

Gravityloss 14y ago
But given coal has perhaps 500 kg/m^3 of carbon while pure CO2 at ambient pressure has about 0.5 kg/m^3. A thousand fold difference. How are you going to dig something up from the ground, expand it thousand fold and put it back in to the same hole? I don't understand this carbon storage business. Clearly coal is the best carbon storage method by far, and it doesn't cost anything as it's already stored.
- wlesieutre 14y ago
  You can also store it in the holes that you took natural gas out of. I'm not aware of it being done on any large scale, but it's been talked about a lot.
- nitrogen 14y ago
  It would be pressurized before storage. However, to reach 500kg/m^3 it looks like it will be close to becoming a liquid: http://www.wolframalpha.com/share/clip?f=d41d8cd98f00b204e9800998ecf8427equv6b77jb http://www.wolframalpha.com/share/clip?f=d41d8cd98f00b204e98...
  - Gravityloss 14y ago
    The critical point is at 7.4 MPa (74 bars) and 304 K (30 C) - there the density is 470 kg/m^3. Here's the phase diagram. http://www.wolframalpha.com/input/?i=co2+critical+point&a=*MC.~-_*Thermodynamic- http://www.wolframalpha.com/input/?i=co2+critical+point&... According to this http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/45_4_WASHINGTON%20DC_08-00_0726.pdf http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/45_4... the pressures in depleted natural gas wells are 20-40 bars so it's not as bad as I expected. Never seen any numbers so had to go look.
    - nitrogen 14y ago
      I think once you consider the water vapor that is also generated from burning natural gas, storing the resultant CO2 in the same space might actually be possible. I suppose I could do an actual calculation based on the molecular weight of H20 and reading up on the combustion stoichiometry of methane et al., but I'm not a chemist by any stretch of the word, and I've got other things to do :).
      - Gravityloss 14y ago
        1 CH_4 + 2 O_2 -> 1 CO_2 + 2H_2O So the amount of CH4 and CO2 is the same in number of molecules, which also means they are the same volume of gas (at low pressures). Of course the mass of CO2 is about three fold but that doesn't mean much.

It's meant to be injected underground.

by uvdiv 14y ago

It's meant to be injected underground.

But given coal has perhaps 500 kg/m^3 of carbon while pure CO2 at ambient pressure has about 0.5 kg/m^3. A thousand fold difference. How are you going to dig something up from the ground, expand it thousand fold and put it back in to the same hole? I don't understand this carbon storage business. Clearly coal is the best carbon storage method by far, and it doesn't cost anything as it's already stored.

wlesieutre 14y ago
You can also store it in the holes that you took natural gas out of. I'm not aware of it being done on any large scale, but it's been talked about a lot.
nitrogen 14y ago
It would be pressurized before storage. However, to reach 500kg/m^3 it looks like it will be close to becoming a liquid: http://www.wolframalpha.com/share/clip?f=d41d8cd98f00b204e9800998ecf8427equv6b77jb http://www.wolframalpha.com/share/clip?f=d41d8cd98f00b204e98...
- Gravityloss 14y ago
  The critical point is at 7.4 MPa (74 bars) and 304 K (30 C) - there the density is 470 kg/m^3. Here's the phase diagram. http://www.wolframalpha.com/input/?i=co2+critical+point&a=*MC.~-_*Thermodynamic- http://www.wolframalpha.com/input/?i=co2+critical+point&... According to this http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/45_4_WASHINGTON%20DC_08-00_0726.pdf http://web.anl.gov/PCS/acsfuel/preprint%20archive/Files/45_4... the pressures in depleted natural gas wells are 20-40 bars so it's not as bad as I expected. Never seen any numbers so had to go look.
  - nitrogen 14y ago
    I think once you consider the water vapor that is also generated from burning natural gas, storing the resultant CO2 in the same space might actually be possible. I suppose I could do an actual calculation based on the molecular weight of H20 and reading up on the combustion stoichiometry of methane et al., but I'm not a chemist by any stretch of the word, and I've got other things to do :).
    - Gravityloss 14y ago
      1 CH_4 + 2 O_2 -> 1 CO_2 + 2H_2O So the amount of CH4 and CO2 is the same in number of molecules, which also means they are the same volume of gas (at low pressures). Of course the mass of CO2 is about three fold but that doesn't mean much.