View Full Version : Is CO2 Sequestration a viable technology?
10-13-2004, 12:46 PM
Burning oil, coal, or wood generates CO2, and that, according to most scientists, is leading us into unknown territory with regard to climate change. One proposal is to capture and sequester the CO2, but I donít know much about the systems and technology for that purpose. Is there real technology out there that could accomplish this in an effective way (including getting net energy out of the system after accounting for the energy used to do the capturing and sequestering)?
Using atomic weights I calculate that almost 4 tons of CO2 would be generated for each ton of carbon burned. Thatís a lot of mass to capture and find a place for.
10-13-2004, 01:09 PM
Most things I've seen are capturing CO2 by conventional methods and injecting it deep underground or in liquid form at the bottom of the ocean. I know some experiments are proposed but don't know the progress of any of them. I'm a bit puzzled by your remark about getting "net" energy out. As far as I can tell this will require a tremenous amount of energy to accomplish. Do a google search as there are a lot of sites out there with info.
Ironically it was inadvertent CO2 sequestration at Biosphere 2 that almost caused the system to fail. We found that oxygen levels dropped far more than anyone predicted until they realized the concrete structure was absorbing large amounts of CO2. The outside looks like a huge greenhouse but there is a huge basement level, the "tehnosphere" containing all the "man behind the curtain" bits that made it wall work. The concrete structure had a stainless steel liner but there were a few acres of exposed concrete.
Getting rid of excess carbon was great but they didn't have a lot of O2 to spare in such a small sealed space. The concrete problem combined with microbe rich soil taken from a cattle ranch pond depleted a lot of the oxygen. At one point a candle flame could not be sustained and crew living inside would become exhausted climbing a flight of stairs. They decided to pump in oxygen. Some folks may condiser that invalidating any integrity of the experiment but the eight folks inside really wanted to breathe. After that crew came out all the concrete inside was sealed with paint but the apparatus didn't have much future left as a sealed environment.
10-13-2004, 02:34 PM
Natural CO2 sequestration takes place in the deep ocean, where CO2 in the form of carbonic acid is deposited in solid form as calcium carbonate. The limiting factor in natural carbon sequestration is the mixing of shallow ocean waters (where the CO2 from the atmosphere initially dissolves) with deep ocean water (where it can be deposited). There is some concern that climate change may interfere with this mixing, which may mean that the Earth's natural capacity for CO2 sequestration may decrease, with a consequent increase in atmospheric CO2. Getting around the mixing step by injecting CO2 directly into deep ocean waters sounds viable, provided that the CO2 can be captured. Using a scrubber system of some kind to produce calcium carbonate at the site may also be viable.
Note also that CO2 sequestration in the biosphere (by planting trees, etc.) is not really permanent since the CO2 will be released when the organism decomposes. There is some evidence that the world's biomass may increase as a result of increased atmospheric CO2 (since it allows plants to grow faster), but the CO2 removed in this way is only temporarily removed from the atmosphere. The fundamental problem with what we're doing to atmospheric CO2 is that the carbon we release into the atmosphere was formerly sequestered (in fossil fuels), so we're adding to the total amount of CO2 in circulation.
10-20-2004, 12:08 PM
I'm a bit puzzled by your remark about getting "net" energy out. As far as I can tell this will require a tremenous amount of energy to accomplish.
That's basically the point.
We burn the coal, oil, gas, whatever, to produce energy but produce CO2 in the process. If it takes more energy to do the sequestration than was generated by the burning, then we haven't generated anything; we have a net enrgy loss. If that is the case, anyone promoting deep sequestration as a solution to CO2 production is truly blowing smoke.
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