Geoscience Reference
In-Depth Information
the Kona coast on the island of Hawaii. Environmental organizations opposed
the experiment on the grounds that it would acidify Hawaii's fishing grounds,
and that it would divert attention from reducing greenhouse gas emissions.
47
A
similar but smaller project with plans to release more than 5 tCO
2
into the deep
ocean off the coast of Norway, also in 2002, was cancelled by the Norway
Ministry of the Environment after opposition from environmental groups.
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Sequestering Under the Seabed
Deep ocean sequestration, as discussed here, is different from injecting
CO
2
beneath the seabed into depleted oil and gas reservoirs or deep saline
formations.
The Sleipner project discussed above is an example of injection beneath
the seafloor, but not injection into the ocean waters. Sequestering CO
2
under
the seabed on the U.S. continental shelf would eliminate the need to negotiate
with local landowners over the rights to surface land and to the pore space in
the subsurface.
However, it would also require developing an offshore infrastructure to
transport and inject the captured CO
2
, along with all the other challenges of
evaluating the potential offshore reservoir, including monitoring the injected
CO
2
, and providing for liability and ownership of the CO
2
after injection has
ceased.
M
INERAL
C
ARBONATION
Another option for sequestering CO
2
produced by fossil fuel combustion
involves converting CO
2
to solid inorganic carbonates, such as CaCO
3
(limestone), using chemical reactions. When this process occurs naturally, it is
known as ―weathering‖ and takes place over thousands or millions of years.
The process can be accelerated by reacting a high concentration of CO
2
with
minerals found in large quantities on the Earth's surface, such as olivine or
serpentine.
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Mineral carbonation has the advantage of sequestering carbon in
solid, stable minerals that can be stored without risk of releasing carbon to the
atmosphere over geologic time scales.
50
Mineral carbonation involves three major activities: (1) preparing the
reactant minerals—mining, crushing, and milling—and transporting them to a
processing plant, (2) reacting the concentrated CO
2
stream with the prepared
minerals, and (3) separating the carbonate products and storing them in a
suitable repository.
