CO2 Sequestration through Deep Saline Injection and ...

Safety, Health and Environmental Risks
The geologic storage sites should be selected to minimize the potential for leakage. Although
CO2 at low concentrations is not directly hazardous to human health, it may detrimentally alter
environmental processes [4]. Leakages could occur over small areas from discrete point sources,
such as abandoned wells. Uncontrolled leakages would have widespread implications for the
environment. Leakages might damage crops, groundwater quality and/or human and animal
health. Other concerns include acidification, changes in biological diversity and species
composition and asphyxiation at high CO2 concentrations. In addition, biogeochemical processes
may be affected as increased CO2 concentrations could change pH, microbial populations and
nutrient supply [4, 5].
The risks of geologic sequestration fall in two categories: Global and local risks. Global risks
arise from leaks that return stored CO2 to the atmosphere. Additionally, global risks involve the
release of CO2 that may contribute significantly to climate change. Moreover, the global risk
may alternatively be viewed as uncertainty in the effectiveness of CO2 containment [6].
Local risks are classified as hazards for things like humans, ecosystems and groundwater [1].
Local risks arise from the elevated CO2 concentrations associated with the flux of CO2 through
the shallow subsurface to the atmosphere. Additionally, local risks occur as a result of the
chemical effects of dissolved CO2 in the subsurface. Moreover, local effects could arise from the
displacement of fluids by the injected CO2 [6]. If leakage to the atmosphere were to occur in
low-lying areas with little wind, or in sumps and basements overlying these diffuse leaks,
humans and animals could be harmed [1].
Catastrophic releases could occur as a result of a blowout of an injection well or existing well in
the vicinity, or as a result of seismic disturbance [7]. Groundwater can be affected by CO2
leaking directly into an aquifer or by brines displacement into overlying aquifers, with
concomitant potential to contaminate potable water supplies. There may also be acidification of
soils and displacement of oxygen in soils [8].
Risks can be minimized by the avoidance of vulnerable areas, monitoring of the injection process
and CO2 plume delineation. Remote sensing techniques and water quality analyses also may be
explored for near-surface monitoring of injection sites and for detection of leaks. Seismic
monitoring must be conducted to avoid potential seismic catastrophes [9].
Public Perception
Public perception is an interesting issue and is of significant importance. As yet, little has been
published on the question of whether people will find CO2 sequestration underground to be
acceptable. Some [10] state that CO2 removal, as a dedicated single technology, is an option that
does not enjoy enthusiastic public support and conclude that these barriers can only be overcome
by research and design and effective demonstration of the technology. It will not be possible to
overcome them by communication alone. The IPCC report of 2005 states that two conditions
will have to be met before the CO2 sequestration is considered as a credible technology namely
anthropogenic global climate change has to be regarded as a relatively serious problem and there
must be acceptance of the need for large reductions in CO2 emissions to reduce the threat of
global climate change. Also people in business, government, or NGO’s must seek out and hear
objections raised by skeptics and come out with answers to them for this technique to be
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