The Carbon Quandary: Essential and Detrimental - Sustainable Design: The Science of Sustainability and Green Engineering - page 291

Figure 7.9 Carbon dioxide that
is produced at the Sleipner
natural gas complex off the coast
of Norway is removed and
pumped into the Utsira
Formation, a highly permeable
sandstone. In this case, the
sequestration cost is less than the
Norwegian carbon emission tax.
Courtesy of Øyvind Hagen, Statoil.
atmosphere. Thus, green engineering is part of an overall comprehensive geopo-
litical strategy.
Even a system as large as the ocean has its limits in greenhouse gas sequestration.
For starters, most of the CO 2 generated by human activities (i.e., anthropogenic)
resides in the upper layers of the ocean (see Fig. 7.10). Carbon compounds move
into and out of oceans predominantly as a function of the solubility of the com-
pound and water temperature. For CO 2 , this means that more of the compound
will remain in the ocean water with decreasing temperature. Ocean mixing is
very slow. Thus, the anthropogenic CO 2 from the atmosphere is confined pre-
dominantly to the very top layers. Virtually half of the anthropogenic CO 2 taken
up by the ocean for the previous two centuries has stayed in the upper 10% of
the ocean. The ocean has removed 48% of the CO 2 released to the troposphere
from burning fossil fuels and cement manufacturing. 5
Thus, to keep CO 2 sequestered, one factor is to help it find its way to the
cooler, deeper parts of the ocean. When it resides near the warmer surface,
it is more likely to be released to the atmosphere. The actual mass of carbon
can be increased by management. For example, certain species of plankton are
often limited in growth by metals, especially iron. Thus, increasing the iron
concentrations in certain ocean layers could dramatically increase the ability of
these organisms to take up and store carbon. Obviously, any large-scale endeavor
like this must be approached with appropriate caution. Too often, the cure can