*** SEE UPDATE AT END OF POST
This is the most interesting idea I’ve encountered in awhile.
CO2 Snow Deposition in Antarctica to Curtail Anthropogenic Global Warming
Ernest Agee, Andrea Orton and John Rogers
A scientific plan is presented that proposes the construction of CO2 deposition plants in the Antarctic for removing CO2 gas from the Earth’s atmosphere. The Antarctic continent offers the best environment on Earth for CO2 deposition at 1 bar of pressure, and temperatures closest 26 to that required for terrestrial air CO2 snow deposition, 133K. This plan consists of several components, including: (a) air chemistry and CO2 snow deposition, (b) the deposition plant and a closed-loop liquid nitrogen refrigeration cycle, (c) the mass storage landfill, (d) power plant requirements, (e) prevention of dry ice sublimation and (f) disposal (or use) of thermal waste. Calculations demonstrate that this project is worthy of consideration, whereby 446 deposition plants supported by 16 1200-MW wind farms can remove 1 B tons (1012 kg) of CO2 annually (a 32 reduction of 0.5 ppmv), which can be stored in an equivalent “landfill” volume of 2 km x 2 km x 33 160 m (insulated to prevent dry ice sublimation).
The individual deposition plant, with a 100m x 100m x 100m refrigeration chamber, would produce approximately 0.4m of CO2 snow per day. The solid CO2 would be excavated into a 380m x 380m x 10m insulated landfill, that would allow one year of storage amounting to 37 0.00224B tons of carbon. Demonstrated success of a prototype system in the Antarctic would be followed by a complete installation of all 446 plants for CO2 snow deposition and storage (amounting to 1B tons annually), with wind farms positioned in favorable coastal regions with 40 katabatic wind currents.
This paper is in press at the Journal of Applied Meteorology and Climatology [link to abstract, full paper] which is behind paywall. Ernie Agee has given me permission to to post the final version of the manuscript [CO2_Snow_Deposition]. Please abide by the AMS copyright guidelines.
From the Introduction:
NASA’s Mars Global Surveyor and Odyssey missions have revealed the presence of a CO2 ice cap on Mars’ South Pole, which is annually subjected to deposition and sublimation. The presence of this CO2 ice cap triggered the idea to consider the possibility of terrestrial air CO2 deposition at the Earth’s South Pole, considering that this is the coldest location on Earth and the energy required to sequester CO2 from the atmosphere (and to maintain insulated storage) might be within the scope of reality. A depositional plant constructed on Antarctica could conceivably pull air into a refrigerated chamber, where sufficient cooling could result in CO2 snow deposition. To pursue this idea, it is first noted that N2, O2 and Ar all would remain in the gas phase as terrestrial air CO2 is brought down to its depositional temperature. Since the atmosphere is only 392 ppmv of CO2, the Clausius-Clapeyron Equation, in conjunction with the CO2 vapor pressure curve, can be considered to calculate the atmosphere’s depositional temperature for CO2. Appendix I is presented to show that the relevant depositional temperature for terrestrial air CO2 snow is 133K, an achievable chilled temperature for the deposition plant. Alternatively, one could consider placing the ambient air under 10 bars of pressure, and the depositional temperature would increase to 152K. It is noteworthy that liquid N2 has a very high efficiency as a cooling agent at this depositional temperature (considering that pure N2 at 10 bars of pressure condenses at 105K). A more reasonable target for deposition is the use of liquid N2 at T = 120°K (under a pressure of P = 29.61 bars), within a closed loop vapor- compression refrigeration system.
Regarding the selection of Antarctica:
The coldest surface air temperature ever measured on Earth was at the Vostok Station in 1983 , a reading of T = -89.2C (or 184K), which is reasonably close to CO2 snow deposition temperature of 133K (1 bar) or 152K (10 bars). In fact, much of Antarctica has been getting colder although the Western Antarctic Ice Sheet (WAIS) is warming. The mean annual temperature of the Antarctic interior is approximately = 226K (-57C), and this continent will continue to be the most favored location for implementing the proposed CO2 sequestration methodology. It is further noted that the vastness of the Antarctic interior with multiple international scientific participation lends itself to the global theme of this paper. The Antarctic Treaty provides a forum for international governance and scientific cooperation. As discussed later in this paper, the construction of CO2 snow deposition plants that are supported by wind farms, offer the opportunity for unique international expertise to join forces to develop the CO2 sequestration facilities that can substantially curtail the effects of anthropogenic GHG warming.
The components of the proposed facility are summarized here:
The components of the proposed Antarctic facility are illustrated in Figure 4, which shows environmental air (A) entering the right side of the depositional chamber (B). Refrigeration is powered by wind farms that drive a closed loop liquid N2 cooling facility. CO2 snow deposition, at rates of approximately 40 cm per day (falling to the bottom of a 100 m x 100 116 m x 100 m chamber), is excavated into the insulated dry ice landfill (D). Appendix II shows the appropriate calculations and design criteria that would remove 1 B tons of CO2 per year, which could be accomplished by approximately 16 1200-MW wind farms. An example of a wind farm that exists in Antarctica can be found at http://www.antarcticanz.govt.nz/scott-base/ross-island-wind-energy.
The refrigeration cycle and energy requirements for CO2 snow deposition are based on a “Closed Loop Liquid-Vapor Cooling System.” Liquid nitrogen is the refrigerant of choice and is effective at the required depositional temperature for CO2 in terrestrial air. Current plans for a 45- 131 MW wind farm (15- 3MW towers) will run one prototype deposition plant. The wind farm should be designed to expand to 1200-MW to supply energy to 28 deposition plants. The CO2 snow landfill for this prototype plant will be 380m x 380m x 10m (for each year of CO2 snow deposition). [The snow deposition] chamber consists of a 100m x 100m x 100m cubical volume on four support pillars with reversible air intake and exhaust fans for the refrigeration process of the ambient air. The front and back sides of this chamber will have embedded coils of liquid nitrogen coolant. The “floor” of the depositional chamber will be allowed to open for excavation into an insulated CO2 landfill. The prototype system will process ambient air at a depositional rate of 0.4m of snow per 24-hour operational day. This amount of solid CO2 can be stored in an insulated CO2 snow landfill that is 142 380m x 380m x 10m, which amounts to 0.00224B tons. The intake-exhaust fans will allow reversed air flow to permit the chamber to operate with the ambient wind direction . It is further noted that five insulated landfills (380m x 380m x 10m for each) will be constructed in a semicircle in close proximity to each deposition plant to accommodate for five years of CO2 sequestration (one landfill filled per year at each deposition plant). [The landfills] will be insulated with polyisocyanurate (effective down to 93°K). Snow cat excavators will operate in groups of five to move the dry ice rapidly into the insulated landfills. A partial vacuum or even refrigeration could be some alternative considerations for maintaining solid CO2.
JC comments: Ok auditors and engineers, will this work? Note this is a scientific concept paper, not a fully vetted engineering design. The authors helpfully provide details of their calculations in appendices.
What are some unintended consequences of this, assuming that it works? The only one I can think of is this. The development of of a CO2 ‘hole’ over Antarctica won’t really be a true ‘hole’ since carbon rich air will be advected into the region, supplying a continued source of CO2 for sequestration. But on average, the CO2 concentration over Antarctica will be low. This will have a cooling effect on the continent, while at the same time not necessarily diminishing snowfall too much at least in the coastal regions. So this would probably be a positive effect.
Relative to other CO2 sequestration proposals that I have seen, this one doesn’t seem to have any negative consequences. And if for some reason it was deemed desirable to return this CO2 to the atmosphere, this could easily be accomplished.
Moderation note: this is a technical thread that will be moderated strictly for relevance and civility. I hope to attract Ernie Agee here to join in the discussion.
UPDATE 9/18:
Judy – I am attaching some comments, in response to
some of the criticism received on our paper. Also, we are grateful for
the many positive comments and emails received, which are encouraging.
Feel free to post the attached on your blog. Ernie
| Rebuttal to some Blogosphere Comments on the CO2 Sequestration paper by Agee, Orton and Rogers 1. Folks working in the Antarctic have commented that 6 months is a more likely working window than the 12 months used in the calculations. (Ok, double the de-sublimation units.) 2. CO2 snow can be compacted into the landfills, and not simply placed in storage as loose snow. 3. Once CO2 has been formed at 133K, it can be maintained in storage at 195K. 4. Please note that 1200MW turbines are NOT being proposed (e.g.400 x 3MW wind farms). 5. Refrigeration units could be placed in a series to allow continuous discharge of CO2 snow. 6. Energy costs can be engineered down, and efficiency engineered up (above 20%). The concept is scientifically sound, and as stated, the engineering details were not provided. 7. Excess heat generated can be used to support more controlled environment facilities. 8. How does the CO2 get to the Antarctic? The same way it does now, and probably more so, as a CO2 hole is created. 9. Steel becomes brittle at -130C (143K) and iron at -196C (77K). Again this is an engineering problem, and an appropriate alloy could be used. 10. Too expensive..! Compare the cost to the economic losses with continued global warming. 11. Confusion between 1B tons of Carbon and 1B tons of CO2 has been clarified in the galley proof. 12. A prototype facility should be planned and constructed in Antarctica asap. Given that the top 5 oil companies in the USA made $137B last year, it would be appropriate that they finance the effort. |