Cheap, 100 Year Global Warming Solution (without reducing emissions)

Few people are left who deny the existence of carbon dioxide induced global warming. Politicians throughout the world have been struggling with a variety of global warming solution. Most of the rhetoric refers to limiting the burning of fossil fuels, and investing into alternative "green" technologies such as wind and solar power, fuel cells, and even nuclear fusion (still). In the US we've been talking about cutting greenhouse gas emissions by anywhere from 15-70% by 2050. Even if the best case scenario happened, the increasing global demand for energy, namely in China and India (by 2050 today�s developing countries will contribute about two thirds of the world�s greenhouse gases), the only thing these political proposals do is to delay the inevitable.

What we need is a method of removing CO2 from the atmosphere on a large scale. Many so-called carbon sequestering technologies are in existence, but most are extremely expensive and impractical to implement on a global or even local scale. Plants do a great job of sequestering carbon, but the Amazon forest is still losing area daily.

According to the "snowball Earth" theory, there was a real danger of the Earth getting so cold that all the carbon dioxide would freeze, thereby effectively eliminating the greenhouse effect of the atmosphere and sealing the planet's fate as a barren ball of ice. Luckily we were just close enough to the sun to keep temperatures high enough to avoid this.

What if we could freeze the carbon dioxide out of the atmosphere, and collect it as a large reservoir of dry ice? Carbon dioxide freezes to dry ice at -78.5 degrees C. There is about 1.72 trillion metric tons or 387 parts per million (ppm) of carbon dioxide in the atmosphere. Historic levels were around 200 ppm meaning we would have to freeze 187 ppm (888.9 billion metric tons) out of the atmosphere. The density of dry ice is about 1.6g/mL, or 1.6 metric tons/one millionth of a cubic km (1x10^-6 km3). With this density, the volume that 888.9 metric tons of dry ice would require turns out to be 555,555 km3. We would need to cool off that much volume to -80 degrees C or so in order to freeze the carbon dioxide out of the atmosphere. What better place than Anarctica? Its area is 13.72 million km2. As an example, a giant insulated and refrigerated cylinder, cooled to -80 degrees C, with radius 421 km and a height of 1 km would achieve slightly more than 555,555 km3. Of course, if it is easier/cheaper/more technically feasible, several smaller cylinders could be constructed to have a total of 555,555 km3.

The good news is that since carbon dioxide is in the air (thus a gas), it will freeze out at -78.5 degrees C, and no purification of carbon dioxide from air is necessary (as opposed to if it were dissolved in a liquid it's freezing/evaporation point would depend on many variables and would likely have to be seperated from its solvent). However, the energy required to freeze such a huge volume is enormous. Is this even feasible? Exactly how much energy would this require? 1 Joule (J) is about the amount of energy required to heat 1g of dry, cool air by 1 degree C. Since it is less efficient to cool air than to heat it, let's say it would take about 1.5 J to cool off 1g of dry cool air by 1 degree C. 1kg of air at room temperature and atmospheric pressure takes up about 5 billionths of a cubic kilometer (5x10^-9 km3).

This means there is about 111 trillion kg of air in 555,555 km3. To cool off that much air would take about 167 quadrillion Joules, or 46.3 trillion Watt-hours (4.63x1013 WH). Sound like a lot? It is; the largest nuclear power plant in the world has a peak output of about 3 gigawatts (3x10^9 W). If this plant powered thousands of giant refrigeration units in Antarctica, it would take a little over 15,000 hours (625 days) to cool off 555,555 km3 of air by 1 degree C. The coldest areas of Antarctica in the winter average around -50 degrees C, so the temperature would have to drop by about 30 degrees C. Assuming near-perfect insulation by the giant freezer(s) from warm summer weather, that would take 51 years.

Once the giant cylinder reaches -80 degrees C, carbon dioxide will begin to precipitate out of the atmosphere, dry ice snow, and accumulate in the cylinder. I don't think it can be accurately predicted (due to weather patterns, wind, etc�.) how long it will take for all the 888.9 billion metric tons of carbon dioxide to diffuse from all across the world to Antarctica, but I will venture a guess at 50 years. Note that methane, the second most important greenhouse gas, will not precipitate at -80 degrees C, it freezes at -162, and all the other major gases in the atmosphere (except of course water) freeze at even lower temperatures.

The cost of a large nuclear reactor like the one needed is in the realm of 10 billion dollars. The refrigeration units may cost around that much also. Transportation of materials and construction equipment, along with the actual labor may be the largest expense, I would guess around 50 billion dollars. If this project costs as much as 100 billion dollars, will it be worth it? According to the International Energy Agency (IEA), the world will need 45 TRILLION dollars (1.1% of the global GDP) to cut greenhouse gas emissions in half by 2050. See this article IEA on Global Warming Solution. Of course, as stated this cuts emissions in half, which will mean that by 2050, the concentration of carbon dioxide will be around 550-600 ppm, much more than the proposed 200 ppm with this project.

I have just outlined a plan for a global warming solution to reduce the concentration of carbon dioxide in the atmosphere by 187ppm (pre-industrial revolution levels) in around 100 years, without the need to reduce emissions. It is far cheaper than the IEA�s estimate of 45 trillion dollars, and will actually reduce the atmospheric carbon dioxide concentration, instead of simply limiting its growth. But will a politician ever see it?

I am not an engineer, and I do understand a cylinder or conical structure of this scale would be a huge feat on par with the 8th wonder of the world, so it is almost certainly more feasible to construct several smaller structers, but I will refer to it as one large structure for ease of language. Anyway, I am confident that it is possible with existing technologies. Outlined below are some initial technical issues I have thought of:

1. What will it be made of? Must be a superb insulator, and resistant to cracks from ice buildup as well as the relatively harsh environment of Antarctica.

2. How to keep it open to the air (for free diffusion of carbon dioxide) while retaining good insulation. Possibly a relatively small hole in the top, this would allow minimal loss in insulating abilities while letting carbon dioxide in.

3. How to keep normal ice (water) from accumulating in the structure and taking up the volume reserved for dry ice. Could possibly dehydrate the air prior to entry to the structure, or could have an initial ice collector at a temperature at which carbon dioxide will not freeze, and have some automated cleaning process. Note that Antarctica is a very dry place to begin with (it rarely snows, but when it does it never goes away).

4. What type of refrigeration units would be used? Would there be enough surface area on the outside of the structure to embed all the units necessary to cool such a huge volume? Also, there could be a meshwork of vents from the units to evenly cool the interior, as opposed to the space directly next to the units. Note that several smaller cylinders could be constructed instead of one big one, making the surface area to volume ratio larger if need be.

5. How much heat would this structure produce on the outside? Conservation of energy states, if you cool a space, another space will be warmed. Will this melt the ice in Antarctica? (Which would raise ocean levels and change oceanic convection currents and salt-mediated diffusion currents). If so, how can the heat currents be controlled so this doesn�t happen? Note that the power plant and structure do not have to be in Antarctica, I simply suggested it because it is the coldest place on Earth, so it would take the shortest time there, but could also work elsewhere. If it is determined the heat generated will melt the ice, a different location could be used, where there is no large body of ice to melt.

6. How to run the power plant. Workers aren�t going to like having to live in Antarctica. (Again, other locations will work, but will take longer to cool to -80 degrees C).

7. Finally, what to do with all the dry ice. Could ship it to enclosed greenhouses around the world to aid and speed up plant growth, transforming the carbon dioxide into biomass, however this process would take a very long time. Note that this project is a cheap, short-term solution, certainly not a long-term one. It will simply buy us time to develop the technologies needed to become free of dependence on limited natural resources and production of greenhouse gases.

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