Environmental Engineering Reference
In-Depth Information
The capacity for geologic carbon sequestration is constrained by the volume and
distribution of potential storage sites. According to the U.S. Department of Energy,
the total storage capacity of physical traps associated with depleted oil and gas reser-
voirs in the United States is limited to about 38 gigatons of carbon and is geographi-
cally distributed in locations that are distant from most U.S. fossil fuel power plants.
The potential U.S. storage capacity of deep porous rock formations that contain
saline groundwater is much larger (estimated by the U.S. Department of Energy to be
about 900 to 3400 gigatons of carbon) and more widely distributed, but less is known
about the effectiveness of trapping mechanisms at these sites. Unmineable coal beds
have also been proposed for potential carbon dioxide storage, but more informa-
tion is needed about the storage characteristics and impacts of carbon dioxide injec-
tion in these formations. Scientists are developing methods to refine estimates of the
national capacity for geologic carbon sequestration.
To fully assess the potential for geologic carbon sequestration, economic costs
and environmental risks must be taken into account. Infrastructure costs will depend
on the locations of suitable storage sites. Environmental risks may include seismic
disturbances, deformation of the land surface, contamination of portable water sup-
plies, and adverse effects on ecosystems and human health. Many of these environ-
mental risks and potential environmental impacts are discussed in the sections that
fol low.
POTENTIAL IMPACTS OF TERRESTRIAL SEQUESTRATION
Potential environmental impacts associated with terrestrial sequestration include
ground disturbance and the loss of soil resources due to erosion; equipment-related
noise; visual impacts; air emissions; disturbance of ecological, cultural, and paleon-
tological resources; and conflicts with current or proposed land uses. Establishing
and managing a terrestrial sequestration plot could involve ground clearing (removal
of vegetative cover) to prepare the ground for planting, grading, vehicular traffic, and
pedestrian traffic. Management could require the use of water for dust control, and
in some cases water could be required to establish and maintain seeds, seedlings, or
crops. The addition of soil additives such as fertilizer and pesticides could have an
impact on water quality. Equipment used to maintain a terrestrial sequestration plot
could be a source of noise and air emissions and create a visual impact if frequent
and conspicuous use was required.
Ecological, cultural, and paleontological resources could be impacted, especially
if a terrestrial sequestration plot is going to replace an established ecological habitat
or otherwise impact undisturbed land that hosts important cultural or paleontologi-
cal resources. Impacts on land use could occur if there were conflicts with existing
land use plans—for example, if land zoned for future commercial or housing devel-
opment is used to establish a forest sequestration plot.
Soil resources can also be impacted by terrestrial sequestration. The careful man-
agement of a sequestration plot should result in an improvement of soil resources,
but poor management practices could adversely impact soils and the viability of the
sequestration project. Practices such as no-till cultivation and planting, crop rotation,
and the use of cover crops should result in the maintenance of soil organic material
