Jökull - 01.01.2005, Page 14

Wallace S. Broecker
drogen which could then be used to generate electric-
ity in fuel cells. The reason is that the infrastructure
required to separate hydrogen gas from the carbon
monoxide produced during the steaming would be far
cheaper than that required to scrub CO2 from the flue
gas emitted by traditional coal-fired electrical power
stations.
Although the idea of recapturing CO2 from the at-
mosphere, at first thought, might appear to be an im-
possible challenge, it turns out to be quite feasible. To
see why this is the case, let us contrast the amount of
kinetic energy carried by a given wind stream with the
amount of CO2 it carries. This might sound like the
comparing of apples and oranges, but actually, it’s not.
The amount of CO2 carried by the air stream can be
thought of in terms of the amount of fossil fuel which
would have to be burned in order to create it. Thought
of this way, we’re comparing energy with energy. The
comparison shows that CO2 wins out over kinetic en-
ergy by more than a factor of 100! Further, CO 2 can
be absorbed into a basic solution and then released in
pure form allowing the absorbent to be recycled.
So, if wind turbines can compete with coal-fired
electrical power plants, then it should be possible
to economically recapture CO2 from the atmosphere
(see Figure 10). Indeed, a small company in Tucson,
Arizona has, for two years, been hard at work creating
the prototype of such a capture device. It is their hope
that it will be ready for field testing early in 2007.
They estimate that the cost of capture will be on the
order of 15 percent that of the energy derived from its
generation. In other words, were the cost of capture
passed along to the consumer, the price of a gallon
of gasoline or of a kilowatt-hour of electricity would
increase by a factor of about 1.15.
Of course, once captured, whether it be from a
power plant or directly from the atmosphere, the CO2
must be put into storage. Several options have been
suggested, each with its own cost, its own capacity
and its own environmental consequences. In each, the
first stop would be to convert the captured CO2 to liq-
uid form. At room temperature this involves pressur-
izing the CO2 gas to 14 atmospheres. In liquid form,
it could be transported to the storage site through the
same kind of pipe lines used to transport petroleum.
Among the disposal options are burial in salty aquifers
(found at one or two kilometers depth in sedimentary
terrains), in lakes beneath the Antarctic ice cap, in the
abyssal ocean and in porous zones which separate suc-
cessive basalt flows. Another somewhat more expen-
sive option would be to mine, grind and dissolve sili-
cate rock rich in the element magnesium. The magne-
sium recovered in this way would be reacted with the
CO2 to form the highly stable magnesium carbonate
mineral, periclase.
Figure 10. Artist’s conception of a device for captur-
ing CO2 from the atmosphere. – Framtíðarsýn á svo-
kallaða Lackner-vinnslustöð til brottnáms koltvíoxíðs
úr andrúmsloftinu.
A few pilot projects are already underway. The
Norwegian company, Statoil, is separating at the well
head the CO2 contained in natural gas from beneath
the North Sea. The CO2 is liquefied and pumped back
down into an aquifer overlying the natural gas-bearing
stratum. British Petroleum is planning to use the pipe
lines constructed to deliver North Sea petroleum, to
export liquid CO2 derived from coal burning for stor-
age in the now depleted reservoir.
As might be suspected, Green Peace vigorously
opposes moves to even test marine disposal. Even
stronger opposition would likely arise if disposal be-
neath the Antarctic ice cap were to be seriously pro-
14 JÖKULL No. 55, 2005