Carbon Capture and Sequestration: The Political Basis? The Scientific Basis? The Practical Basis?

By  Les Porter

In the 25 September 2009 issue of Science, the issue-featured subject of Carbon Capture and Sequestration (CCS) is discussed.

Most of us with an intelligent interest in species "survival" and the the avoiding of possible negative 'end-game' scenarios with energy generation from coal, recall with marked trepidation, the pre-election statements made by Barack Obama with respect to American Coal.  You see these statements played over and over by various utility interests. The clear sense of his campaign rhetoric was a recognition of Coal's potential role in replacing a very sizable volume of imported oil along with a  variety of home-grown energy production schemes.  Coal is a resource the United States has in abundance -- and during the 2008 Presidential Campaign -- Senator Obama noted the potential power of coal in the world's Energy Future making such campaign statements, [paraphrasing] as, "I can't see why we can't figure out how to get clean energy from coal."

One of the key individuals to explore and hopefully implement the "figure it out" task of making coal a clean energy source during the next 4 to 8 years is Dr. Steven Chu, as Secretary of the Department of Energy.

energy.senate.gov/public/_files/DrChuENRTestimony.pdf

During the confirmation hearings to seat Steven Chu as Secretary of the Department of Energy, those Senators largely supported by campaign donations from Big Carbon interests hammered away at Nobel Laureate Chu doubting his dedication to some Obama constituent political goals that were not spoken favorably about by Chu prior to nomination to head DOE.  

http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=111_senate_hearings&docid=f:47253.pdf
 

 
Image: DOE, Steven Chu, Secretary

"The scale of CCS needed to make a significant dent in worldwide carbon emissions is staggering. Roughly 6 billion metric tons of coal are used each year, producing 18 billion tons of CO2. In contrast, we now sequester a few million metric tons of CO2 per year. At geological storage densities of CO2 (~0.6 kg/m^3), underground sequestration will require a storage volume of 30,000 km^3/year. This may be sufficient storage capacity, but more testing is required to demonstrate such capacity and integrity."  ---- excerpt from an Editorial in Science 25 September 2009, by U S Secretary of Energy, and Nobel Laureate, Dr.Steven Chu

You can read the entire editorial here:

http://www.sciencemag.org/cgi/content/full/sci;325/5948/1599

This editorial covers a lot of ground and yet is one of the "briefest" editorials I've seen in many, many years.  If brevity is the compact distillation of meaning, this editorial is then one of the "densest" in content and "meatiest" in implications as to "where" we need to go and some of "how" we need to go, to get there.

We are in a mess with CO2, a mess that is cheaper to clean up now than meeting the consequences of global warming later.      -- Wallace Broecker, Climate Scientist at Columbia University,

My biggest concern is that truly forward-looking and important work that needs to be done is diminished while Chu expends both effort and budget to ramrod CCS for coal interests while directing DOE. The funding and the length of time we have to address not just emissions growth, which is not much time, but the industrial-scale capture of atmospheric CO2 already emplaced is what worries me.   Mankind already knows what level of CO2 promotes a climate favorable to creatures evolved in to it.  One track to a sucessful effort would be the outright recognition that these governmentally developed and supported energy developments and the atmospheric reclamation that would be developed from them, be operated under and by the US Government for the national good.  I say, National Interest -- Not Corporate Interests. What is good for General Bullmoose is NOT good for the USA.  Recapture is the catch word.

Think about Recapture.  But not just thinking.  If there is to be a viable future that is as good or better than what we have had -- Recapture has to be done.

With that for a stimulus, DOE would become the nation's major tool to address the global heat death we are in desparate need of addressing.  Using DOE as a coal burning tool is wasteful.  3 billion years of life taking C out of the air and sequestering it, along with removal by essentially geological inorganic chemistry has been reversed by hominids. 

DOE has other research ongoing, much more important than Coal CCS.  Solving the problems in them will hearld the promise of an unlimited future if we can ghange the mix.  Simply leaving the Coal in the ground and devoting research to generation 4 nuclear reactors, improved solar efficiencies, connecting the American Power Grid and scaling it for international connection; biofuels and over all non-emissive tactics must be speeded.

I started thinking about that 30,000 cubic kilometer volume needed for the storage of CO2 per year as per Dr. Chu's editorial above.  And I also got to thinking about the 6 billion metric tons of coal and how much CO2 it would "make" when burned, to be released into the air. By far, the largest component of coal is carbon.  6 billion tons of average to "good" bituminous coal is some of the "dirtiest" most poisonous stuff in the world. So just cleaning up things like mercury from coal is a "good" then; a good thing to do.,  But what is the Carbon level in coal?

Being generous, for the back-of-the-envelope, do-in-your-head-almost kind of examination, let's assume that "average" coal is 70% carbon, though lignite often ranges around 60% and anthracite some times exceeds 80% carbon.  6 billion tons burned per year containing 70% carbon = 4.2 billion tons of pure carbon.  When you burn 4.2 billion tons of pure carbon with air you add oxygen, and the final result weighs 3.6667 times as much as the carbon you started with, or 4.2 billion tons C x 3.6667 = 15.4 billion tons CO2. 

During this burn you have captured and removed from other uses, ~ 11.2 billion tons of oxygen.

So my figures are the "same order of magnitude" as those in the editorial.  Using the roughly 0.6 kg CO2 per cubic meter of storage medium, 15.4 billion tons is 15.4 trillion kg where each full kilogram of CO2 would require 1.6667 cubic meters of storage medium [porous rock] and would require 15.4 trillion x 1.6667 = 25.6667 trillion cubic meters of rock for the CO2.

25.7 trillion cubic meters of porous rock is a lot of rock. 25.7 trillion cubic meters divided by 1 billion cubic meters / cubic kilometer = 25,700 cubic kilometers of porous rock that would be filled each year. Our rough back-of-the-envelope figure of 25,700 km^3 is the "same order of magnitude" of Dr. Chu's 30,000 km^3 per year, and implies Dr. Chu's coal is much higher Carbon coal ["better" coal, more anthracite or better bituminous].  Now, Dr. Chu is a very scientifically smart guy, and also politically savvy, and quite practical too.  But we are in the ball park now.
 
To run this same figure from a different direction, suppose you efficiently burn 6 billion tons of 70% C coal at sea level, extracting energy from it and releasing the CO2 into the air.  You do this at a temperature 25 C [77 F.] and pressure of 1 atmosphere. Each ton of carbon dioxide made at atmospheric pressure and 25 C occupies ~556.2 cubic meters.  15.4 billion tons CO2 x 556.2 cubic meters = 8.56548 trillion cubic meters of CO2 is produced.  At 77 F each of those cubic meters of CO2 weighs 1000 kg / 556.2 = 1.798 kg.  so to store the CO2 at a density of 0.6 kg per cubic meter means 1.798/0.6 =  2.9965 cubic meters of porous rock for each cubic meter of CO2.

That yields 2.9965 cubic meters rock for each cubic meter of CO2, so for  8.56548 Trillion Cubic Meters of CO2  a total volume of porous rock = 2.9965 x 8.56548 trillion = 25.666 trillion cubic meters or 25,666 cubic kilometers of porous rock.

Again we are in Steven Chu's "order of magnitude range" for required volume of roughly 30,000 cubic kilometers of rock per year just to cover the sequestration of coal produced carbon dioxide each year. If we could find such a perfectly porous capped rock, so the CO2 put under ground would not leak out to the air, what kind of surface area over this volume are we talking about each year?

Granted, we are speaking "volume" of rock per year but those "area's" of the earth's surface having porous rock of the right kind to store CO2 are likely somewhat limited in area above that volume.

Let's take West Virgina, from which a lot of coal has been produced and choose to put the sinister gaseous CO2 that would have been placed in the air, back under ground so that we have reduced what would otherwise be cooking us in a solar oven in a few more years.   What would that look like?

Now, you know that the Great State of West Virginia covers 62,755 square kilometers of the earth's surface. and if we somehow could find porous rock for the sequestration of CO2, say covering the entire state at a depth of 1 km or even 2 km, and this porous rock was itself  1  kilometer thick --  that rock beneath West Virginia could store the global production of CO2 of 6 billion tons from 70%-carbon coal for 2.44 years, and then we would have to look "elsewhere." In 891 days, West Virgina would be "full," but good riddance to the coal-sourced CO2!

In actuality if we capture the gas from the burning chamber's exhaust, cool it and pipe it and deposit it, what is it we are doing?

15.4 billion tons of captured CO2 in a year, means the capture and piping of 490 tons of CO2 per second every second, at atmospheric pressure, which is the pressure of the source O2 used to make the CO2.

If we are working at atmospheric pressure, we must handle a volume CO2 gas consisteing of 272,538 cubic meters per second. If this CO2 were in a cubic box at 1 atm, the box would be 213 feet on a side, [65 m on a side]  It would take a lot of "fan" or a lot of fans to move that much CO2.  In heating and air conditioning "business" in the US it is common to describe the capacity of air handlers in Standard Cubic Feet per Minute (SCFM).  To describe the size of the gas handler needed the scale is astonishing -- 577.5 million SCFM  Right, nobody builds a gas-handler of that size right now.  The figure represents the volume on a planetary scale   

Now lets just assume that the porous rock with the needed geological structures underlies the entire United States, and that we stored all of the CO2 produced in the world at 6 billion tons per year in that layer of porous rock 1 km down and 1 km thick, and this is just from coal burning, how long would that give us?

The US area covers 9,629,091  square kilometers 9,629,091 / 25,700 = 375 years!  Of course, the porous rock is not that evenly distributed either in West Virgina or across the United States.  The US may not last that long, nor the rest of the nations of earth -- because not a bit of CO2 that is already airborne is being removed, nor is there any prohibition against burning, nor is there industrial-level taxing upon the act of burning the coal.

Essentially the ecologically unbalanced sources of CO2 without comparable sinks exacerbates the problem to a level far greater than a carbon cap and trade system will control.

Graph image from IPCC, Figure 5.2, modified by author with text added.

http://www.ipcc.ch/publications_and_data/publications_and_data_figures_and_tables_gr-climate-changes-2001-syr.htm

Reducing Emissions is not the REAL problem. Stopping Corporate Industrial emissions and their growth is the real problem.

Now, When the Wind Blows . . .

Take a look at this to realize how much energy there is in the CO2 passing through the fan of a windmill.

www.netl.doe.gov/publications/proceedings/04/carbon-seq/211.pdf
 
Depending on the wind speed, there is actually hope for technology that can remove the CO2 passively.