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12.7 CO 2 Transportation 381

pressure is in the range of 84.9–207.3 atm where CO 2 is a dense-phase fluid over a
wide range of temperatures. Nonetheless, the gas properties also depend on
impurities such as SO x ,NO x , and other air contaminants. A complex model is
required to accurately predict the fluid property along the pipeline. Interested
readers have to dig deeper into the literature for in-depth knowledge.

12.7.2 Ship Transportation

For CO 2 transport by ship, it is most efficient to transport CO 2 as a cryogenic liquid.
The best condition for CO 2 transport by ship is about 6.4 atm and −51.2 °C[7]. As
it is stored in containers during transportation, there is no pressure drop concern.
The optimal transport pressure depends on the state of the fluid. In short, large-
scale transport of CO 2 by ship could be achieved by semi-pressurized vessels of
3
around 20,000 m at pressures of 6.415 atm and −52 °C in order to use existing ship
and infrastructures. This condition also allows low unit cost in transport. The total
costs of ship-based transport are estimated to be $20–30 per ton CO 2 .

12.8 CO 2 Storage

It would be ideal to convert CO 2 into valuable products, such as methanol. A small
portion can be used for production of soda drinks. Unfortunately, applications and
consumptions of CO 2 are very limited compared to its production rate in fossil fuel-
fired power plants and vehicles.
More practically, the captured CO 2 must be then stored properly without escape
from its sinks into the atmosphere. Options listed below are considered relatively
feasible both economically and environment-friendly.
(1) Geological storage
• Enhanced oil recovery (EOR),
• Deep saline reservoirs and aquifers,
• Unmineable coal beds.
(2) Deep ocean storage
(3) Ecosystem storage
Geological storage is the only CO 2 storage method that has been well developed
globally at a commercial scale. Ocean storage is under extensive research and
development owing to its potentially large capacity. Ecosystem storage is another
promising approach that is under investigation. These options are introduced as
follows.