We have cited, over the past months, several quite credible sources, including scientists at US National Laboratories, indicating that, if required, Carbon Dioxide can be captured more efficiently and, through the harnessing of site-specific environmental energy, at less cost directly from the atmosphere than by "scrubbing" it from the exhaust flues of cement kilns and other sources, where CO2 is emitted as a by-product of valuable industrial processes.
Sandia National Laboratory, for instance, posits the use of solar energy to accomplish both the capture of CO2, from the atmosphere, and it's transmutation into substances of commercial value, as opposed to inefficient, perhaps impermanent, geologic sequestration and disposal.
We have cited Klaus Lackner, of Columbia University, in those respects, as well. Herein, via the enclosed link, attached document and excerpt, he, too, again, argues that CO2 could best be captured at centralized, more remote, sites, where the CO2 could better be dealt with, one way or another.
Not only could environmental energy thus be harnessed to the task of CO2 collection, but the immense costs of building both dispersed collection sites at individual points of emission and the many, many miles of pipelines, or other infrastructure, necessary for CO2 transport, and the costs of transport, would thus be eliminated.
And, such a scenario would allow the recycling of the huge amount of CO2 emitted by "the transportation sector" - the world's widely-dispersed millions and millions of planes, trains and automobiles equipped with internal combustion, hydrocarbon-burning engines whose combined CO2 output at least rivals that all our coal-use industries. "Capturing Carbon Dioxide From Air" would account for the CO2 from all sources, and not unfairly burden coal use, and other, industries with specific over-assessment of responsibility.
Our contention is that CO2, once collected and concentrated, should be recycled, again using environmental energy, into methanol, using Sabaitier, Carnol, or one of the other available technologies, and thus returned to the train of commercial value.
However: If petroleum producers insist they must have Carbon Dioxide to scrub a last bit of oil out of nearly-depleted natural reservoirs, then, using Lackner's technology outlined herein, they can damn-well extract it themselves, on-site, at their cost, and not burden our coal-use industries with the expense of collection, transport, delivery and, if we read a Louisiana law we recently sent you correctly, the costs of assuring containment, and assuming liability, for decades.
Although Lackner, and his co-authors, herein don't address the issue of carbon recycling, they make it abundantly and thoroughly clear that, if we must collect Carbon Dioxide for the purpose of disposal, then it's far better to collect it from the atmosphere, at the place where it is to be disposed of.
As follows:
"Capturing Carbon Dioxide From Air
Klaus S. Lackner
Columbia University
500 West 120th Street
New York, NY 10027
Columbia University
500 West 120th Street
New York, NY 10027
Patrick Grimes
Grimes Associates
Scotch Plains, NJ 07076
Hans-J. Ziock
Los Alamos National Laboratory
P.O.Box 1663
Los Alamos, NM 87544
Abstract
Air extraction is an appealing concept, because it separates the source from disposal. One could collect CO2 after the fact and from any source. Air extraction could reduce atmospheric CO2 levels without making the existing energy or transportation infrastructure obsolete. There would be no need for a network of pipelines shipping CO2 from its source to its disposal site. The atmosphere would act as a temporary storage and transport system. We will discuss the potential impact of such a technology on the climate change debate and outline how such an approach could actually be implemented.
Introduction
The economic stakes in dealing with climate change are big and costs could escalate dramatically, if the transition to a zero emission economy would have to happen fast. Abandoning existing infrastructure is prohibitively expensive and as long as new technology is not yet ready to be phased in, improvements and additions to the existing infrastructure will tend to perpetuate the problem. ... For the portion of the CO2 that is emitted from small and distributed sources, capture of CO2 from the air may always the best solution.
In this paper we argue that capture of CO2 from natural airflow is technically feasible at a rate far above the rate at which trees capture CO2. The photosynthesis by plants seems to be more limited by sunlight than capture of CO2. We will provide a rough estimate of the expected cost and the scale of operation required to deal with the world’s CO2 emissions.
Utilizing the air as a temporary buffer makes this process easier and avoids the need for developing specific capture processes for each and every emitter.
Objective
... To stabilize CO2 levels, it is necessary to not only deal with CO2 emissions from power plants, but from all sources in an industrial economy. While it is generally agreed that the reductions demanded by the Kyoto Treaty would be far less than what would ultimately be required to stabilize CO2 levels in the atmosphere [5], it is also clear that even this goal would be too ambitious to be achieved by exclusively eliminating emissions from power plants. ... it is necessary to address all carbon dioxide emissions including those from small and mobile sources.
A source of carbon dioxide that is particularly difficult to manage is the transportation sector.
Distributed carbon dioxide sources account for approximately half of the total emissions. ... in the long term, they cannot be ignored.
Carbon dioxide capture from the atmosphere, in principle, can deal with any source, large or small. Indeed, the appeal of biomass for sequestration and of credits for growing trees is based on the very same premise. Since photosynthesis takes the carbon it needs from the air, it can compensate for any emission, and ideally it can be done at the disposal site eliminating the need for long distance surface transportation.
Thus, it is our objective to explore the feasibility of CO2 capture from air. We would like to find out whether it is physically possible, whether it could be done at acceptable cost,and whether the scale of such an operation would be acceptable.
(Note the following)
We will show in the following that CO2 capture is physically and economically feasible, and that the scale of operation is actually small compared to other renewable options that are considered as possible replacements for fossil energy.
(They do. And, they demonstrate that the costs, "the scale", of dispersed CO2 management "is ... small compared to ... renewable options ... as replacements for fossil energy.)
Approach
Carbon dioxide capture from air is certainly possible. Plants during photosynthesis routinely accomplish this task. Chemical processes also can capture CO2. A classic chemistry experiment is to bubble air through a calcium hydroxide solution and to remove the air’s CO2 in this fashion. Other means work as well and have been used in the past in industrial processes to generate CO2 free air. However, in capturing CO2 one is very much constrained by economic considerations.
Current annual world emissions from human activities equal 1% of the total CO2 in the air. (and) one can use the air as a conveyer that moves CO2 from its source to its sink.
(Note: As in "emissions from human activities equal 1% of the total CO2 in the air"; compared to volcanoes and such, as we have elsewhere thoroughly documented, all of us, and all of our coal, are pretty small potatoes when it comes to making greenhouse gas.)
... A windmill that operates by extracting kinetic energy from natural airflow needs to be two orders of magnitude larger than a CO2 collector that captures CO2 to compensate for the emissions from a diesel engine that generates the same amount of electricity. Since windmills appear economically viable, this suggests that the capturing apparatus should not be too expensive to build.
... we can also compare the efficacy of our approach to collecting solar energy. Peak fluxes of solar energy on the ground are around 1,000 W/m2. Average fluxes in desert climates accounting for weather and day and night are around 200 W/m2. Photovoltaic panels can capture maybe 25% of this flux. Under conditions of intensive agriculture, biomass growth can capture maybe 1.5% of this flux ... Typical unmanaged forest growth would fall far short of capturing even that much carbon equivalent.
The purpose of this discussion is to establish an estimate of a system’s size necessary to collect CO2 generated by an energy source of a given size. If one could maintain a flow of 3 m/s through some filter system, and collect half the CO2 that passes through it, then the system would collect per square meter the CO2 output from 15 kW of primary energy. This is more than the per capita primary energy consumption in the US, which is approximately 10kW. The size of a CO2 collection system would thus have to be less than 1m2 per person. Covering the same energy demand with wind-generated electricity instead would require an area at least a hundred times larger.
(In other words, as we understand this: One square meter, roughly a square yard, 3' by 3', of CO2 collection space would more than account for the CO2 emissions assignable per capita to each US citizen. To replace the power generated by burning fossil fuels with non-carbon emitting, wind-powered generators would require a space "a hundred times larger". Not an efficient use of land, it would seem.)
Even before having defined specific filters and sorbent materials, this discussion already suggests that the cost of CO2 collection is not prohibitively high.
(The authors include calculations and examples beyond our limited ability to fully understand, much less explain. Like much of what we submit to you, it begs study by qualified individuals who could help all the rest of us make good use of the information. We don't include those calculations and explanations herein.)
Thus, we need to develop a technology that would allow the capture of CO2 from natural or man-made airflows that would enable us to recycle the sorbent and create a concentrated stream of CO2. In the following section we shall discuss options for such processes.
Technology
A collector capturing CO2 from a natural airflow is akin to a windmill. In one case one extracts CO2 out of the airflow, in the other case one extracts kinetic energy. However, one should not pursue this analogy too far. A modern windmill has an aerodynamic design that maximizes momentum flow from the air to the airfoil. Unlike momentum that can be transported independently of mass flow, material flows are intimately tied to mass flow and thus require drastically different designs. The first task in developing CO2 capture from air would be to define an optimal design. Candidates include filter banks standing in the airflow like snow fences, designs that resembles leaves on a tree, or systems akin to cooling towers that actively move the air.
To illustrate this with an example: some years ago, a wind energy technology was suggested that could operate in a dry climate. Inside a large tower, water is pumped to the top, where it cools the air by evaporation. The cold air, being denser, would cause a downdraft inside the convection tower. The potential energy of the air falling down is eight times larger than the potential energy of the water that has to be pumped up. The air flows through the lightweight tower structure and escapes at the bottom where its kinetic energy is harnessed by a number of wind turbines. This effort had grown from preliminary designs to a consortium that was planning on building such a tower in the Negev desert . For such a tower to be economically viable it would cost maybe $3,000 per kWe. Such a cost does not appear unreasonable. Nevertheless in the end, these towers were not built. However, our point here is only to show how much more efficient such a tower would be at extracting CO2 rather than kinetic energy.
Figure 1 (Not displayed in our excerpt.) shows a simple design of a convective tower that would generate 3 to 4 MW of electricity. It also passes 9,500 tons/day of CO2 through itself, which corresponds to the CO2 output of conventional 360 MW coal fired power plant. The CO2 flux is also equivalent to the CO2 output of the vehicle fleet of a city of 700,000 people, indicating the usefulness of the concept for dealing with emissions from the transportation sector. The first comparison to the coal-fired power plant reiterates our earlier observation. The cost of the collection tower, even if it exceeded the $9 million implied by a cost of $3,000/kW for its electricity generating cousin, would still be extremely cheap compared to the cost of the coal fired power plant, which would be approximately $300 to $400 million. Thus, the cost of the collection tower would be dwarfed by the cost of the corresponding power plant. While we are not advocating this specific design for CO2 capture, it shows once again that the physical structure required to capture the CO2 is not going to drive the cost of the process. There are a number of different design options, and further work will have to tell which ones are most advantageous.
Results
Results of our dimensional analysis suggest that the collection of CO2 directly from air is feasible. Collecting CO2 from air is far more efficient than collecting wind energy. We emphasize that we can make this statement without having determined an optimal collection system or having settled on an optimal choice of sorbents. Even looking at the most simple implementations suggests that the cost of the effort is tolerable. Our simple analysis suggests, that filter systems using alkaline solutions of Ca(OH)2, or sodium or potassium hydroxide could easily capture CO2 from air. The major cost of any such process is in the recovery of the sorbent.
(Note: Even with the costs of carbon recovery "directly from the air", which is "feasible", "Collecting CO2 from air is far more efficient than collecting wind energy".)
A preliminary analysis assuming Ca(OH)2 as a possible sorbent suggests, that the cost will be on the order of $10 to $15 per ton of CO2 and that the additional CO2 generated in the process of collection is substantially less than the amount of CO2 captured. In any event, one would design the sorbent recovery system so that it would capture its own CO2. Since this process would be a large operation at a good disposal site, it is a prime candidate for on-site capture. The energy penalty for this approach is about 200 kJ for every 700 kJ of heat of combustion from gasoline. Per gallon of gasoline one would need 3 cents worth of coal to accomplish the CO2 recovery from lime. Other sorbents, with better chemical kinetics and lower binding energies could substantially improve the cost of the overall process design.
(And, if the CO2, once recovered, were then, using environmental energy, converted into valuable methanol, would the effective cost per ton, and energy penalty, not be further reduced?)
We have also looked at the overall scale of the collection effort. As mentioned earlier, the cross sectional area needed in the US is slightly less than 1 m2 per person. However, one could not combine all these units in a single location, as they would tend to interfere with each other. Units down wind from other units could not capture the nominal value of CO2 as they would be processing air already depleted in CO2.
Even a worldwide collection system does not have to be extremely large. Per person the cross sectional area facing the wind would have to be about 0.12m2. The area would increase 0.65m2 per person if the world’s per capita energy consumption would reach the current US per capita consumption. At present rate, 380,000 collection units each taking up 100 m × 100 m in land area could collect all the CO2 emissions from human activities. One would need one such unit – roughly two football fields – for every 16,000 people. These units could share the land with other activities. For example each unit could consist of 5 vertical subunits
19 m wide by 19 m tall. The 380,000 units would have to be spread out over an area at least 530 km by 530 km of which they would occupy 1.4%.
(In other words, two football fields would handle the carbon capture needs of 16,000 people. Not a lot of land, in the grand scheme of things, especially if we put the collectors in "waste" desert areas to take advantage of solar energy. - JtM)
Benefits
The method of extracting carbon dioxide from the air we outlined above could operate on a scale large enough to deal with all the carbon dioxide emitted in the world. The only limit to the use of this approach would be from other technologies that for specific emissions may be more cost-effective. One advantage of extraction from air is that it would be possible to sequester more CO2 than is generated, thereby reducing the total CO2 load of the atmosphere.
There are ... additional issues to consider. One is the cost of transporting CO2. Transport by the air comes free, and typical cost estimates for long distance transport of CO2 are around $10/ton. At that cost, a careful economic analysis would be required to decide whether in a given case atmospheric convection would not allow for a cheaper solution to the problem. The cost of carbon capture could well be comparable to the cost of shipping carbon. Furthermore, extraction from air would open up resource sites for carbon disposal, which are simply too far away from all sources to compete by any other means. This additional effect may well compensate for a slightly higher cost in capture relative to transport to a more nearby sink.
As we mentioned in the introduction, a major advantage of carbon capture from the air is that it does not require abandonment of existing infrastructure. Extraction from the air could be introduced in parallel to other methods that sequester carbon dioxide directly captured at the source. It would allow the removal of CO2 virtually immediately and it could be grown rapidly over the course of the next few decades. The cost of the process is independent of the amount of consumption. While on-site capture becomes more and more expensive as one is trying to drive emissions to zero, net-zero emissions obtained by matching extraction from air to the output of some plant, does not incur such increases in cost. Indeed one could aim for 80%, 100% or even 120% capture without substantively changing the cost structure. By having capture exceed emissions, one could actually aim for reducing CO2 in the air.
(And, again, once the CO2 is economically recovered, it can be profitably recycled.)
How fast such a method will be introduced depends on many variables. If we assume that the overall cost of the process is $15 per ton of CO2 and if we further assume that roughly half of this cost is in capital investment, then the elimination of 22 billion tons of CO2 would represent an annual cost of $330 billion worldwide. The capital cost involved would be on the order of 1.6 trillion, which is a huge number, but it is again not so large as to be prohibitive. If one were to aim at an implementation in the course of a decade, the total worldwide capital investment would be comparable to the current discussion on tax cuts in the US alone. New industries like the electronic industry have shown that investments on this scale can indeed be made in a matter of decades. Whether or not it will be done depends on the perceived urgency of the problem.
Bibliography
1. Lackner, K.S., H.-J. Ziock, and P. Grimes. Carbon Dioxide Extraction from Air: Is it an Option? in Proceedings of the 24th International Conference on Coal Utilization & Fuel Systems. 1999. Clearwater, Florida.
2. Lackner, K.S., P. Grimes, and H.-J. Ziock, The Case for Carbon Dioxide Extraction from Air. SourceBook--The Energy Industry's Journal of Issues, 1999. 57(9): p. 6-10.
3. Lackner, K.S., P. Grimes, and H.-J. Ziock, Carbon Dioxide Extraction from Air? 1999, Los Alamos National Laboratory: Los Alamos, NM.
4. Elliott, S., et al., Compensation of Atmospheric CO2 Buildup through Engineered Chemical Sinkage. Geophysical Research Letters, 2001.
2. Lackner, K.S., P. Grimes, and H.-J. Ziock, The Case for Carbon Dioxide Extraction from Air. SourceBook--The Energy Industry's Journal of Issues, 1999. 57(9): p. 6-10.
3. Lackner, K.S., P. Grimes, and H.-J. Ziock, Carbon Dioxide Extraction from Air? 1999, Los Alamos National Laboratory: Los Alamos, NM.
4. Elliott, S., et al., Compensation of Atmospheric CO2 Buildup through Engineered Chemical Sinkage. Geophysical Research Letters, 2001.
5. Climate Change 1994, Radiative Forcing of Climate Change and an Evaluation of the IPCC IS92 Emission Scenario., ed. J.T. Houghton, et al. 1995, Cambridge: Cambridge University Press.
6. Seifritz, W., Partial and total reduction of CO2 Emissions of Automobiles Using CO2 Traps. Int. J. Hydrogen Energy, 1993. 18: p. 243--251.
7. Gipe, P., Wind Energy Comes of Age. 1995, New York: John Wiley & Sons.
8. Ranney, J.W. and J.H. Cushman, Energy From Biomass, in The Energy Source Book, R. Howes and A. Fainberg, Editors. 1991, American Institute of Physics: New York.
9. Bishop, J.E., Wind Tower May Yield Cheap Power, in Wall Street Journal. June 9, 1993."
6. Seifritz, W., Partial and total reduction of CO2 Emissions of Automobiles Using CO2 Traps. Int. J. Hydrogen Energy, 1993. 18: p. 243--251.
7. Gipe, P., Wind Energy Comes of Age. 1995, New York: John Wiley & Sons.
8. Ranney, J.W. and J.H. Cushman, Energy From Biomass, in The Energy Source Book, R. Howes and A. Fainberg, Editors. 1991, American Institute of Physics: New York.
9. Bishop, J.E., Wind Tower May Yield Cheap Power, in Wall Street Journal. June 9, 1993."
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One point that shouldn't escape anyone, as we noted far above: If petroleum companies do want CO2 for enhanced oil recovery, they can get it cheaper on-site than our coal industries can ship it to them. And, they would be paying for it themselves, rather than sticking us with the freight and eternal sequestration site maintenance and liability charges, as in the Louisiana law we earlier brought to your attention.
To emphasize the efficiencies, we quote the Abstract: "Air extraction could reduce atmospheric CO2 levels without making the existing energy or transportation infrastructure obsolete. There would be no need for a network of pipelines shipping CO2 from its source to its disposal site."
Moreover, and it demands hammering: Once we recover CO2 from the atmosphere, we can use it to make more liquid and gaseous fuels, and useful plastics.
Carbon Dioxide is a valuable by-product of our coal use.