Environmental Engineering Reference
In-Depth Information
FOSSIL-FUEL SYSTEMS AS A BASIS FOR CARBON-CYCLE
MANAGEMENT
The last case study is also conceptually simple. Carbon dioxide resulting
from the combustion of fossil fuel in power plants is captured and then
sequestered for centuries in the ocean, in deep aquifers, in geologic for-
mations, or in other reasonably long-term sinks. Technologies to capture
the CO
2
emissions and inject them into various sinks exist, and, especially
if carbon capture is implemented at the initial design stage, rather than
retrofitted, such systems appear to be technologically and economically
feasible.
33
This technology is already in use: in the first instance of carbon
sequestration for environmental reasons, Norway's state-owned petroleum
company, Statoil, is sequestering the carbon dioxide content of the gas it
is extracting from the North Sea Sleipner gas field back into an aquifer
about 1,000 meters below the sea bed. (The CO
2
content of the gas is
about 9 percent.) Statoil finds this economically preferable to paying the
$55-per-ton CO
2
tax that would apply if the gas were simply vented.
34
This is only a proof of concept, however; issues of environmental impacts,
of technological and economic feasibility, and of liability remain to be
resolved.
When combined with the possibility of a hydrogen economy, such car-
bon sequestration raises the possibility of being able to exploit reserves of
fossil fuel without a substantial increase in CO
2
emissions; thus, global
climate change forces us, essentially, to decarbonize fossil-fuel con-
sumption.
35
But an industrial ecology approach allows one to explore a
more visionary, and perhaps far more important, possibility: the im-
plementation of such carbon sequestration/hydrogen technologies as
the basis of a deliberately engineered system of governance for the
human carbon cycle (figure 4). Here, the global set of fossil-fuel plants
are designed as a system to be tunable to help produce over time the
desired atmospheric concentration of carbon dioxide, given other vari-
ables (e.g., impacts on vegetation, desired degree of global climate change,
lag times of various components of the systems involved, changes in inso-
lation, other carbon dioxide emissions, concentrations of other green-
house gases, use of other mitigation technologies). The control functions
of such a system are twofold: the ratio of biomass and municipal waste to
fossil fuel input into the system, and the ratio of CO
2
emitted to CO
2
