Climate Change 2001:
Working Group III: Mitigation
Other reports in this collection Transmission and Storage of CO2

CO2 can be transported to storage sites using high-pressure pipelines or by ship. Pipelines are used routinely today to transport CO2 long distances for use in enhanced oil recovery (Stevens et al., 2000). Although CO2 is not transported by ship at present, tankers similar to those currently used for liquefied petroleum gas (LPG) could be used for this purpose (Ozaki, 1997).

CO2 exists in natural underground reservoirs in various parts of the world. Potential sites for storage of captured CO2 are underground reservoirs, such as depleted oil and gas fields or deep saline reservoirs. CO2 injected into coal beds may be preferentially absorbed, displacing methane from the coal; sequestration would be achieved providing the coal is never mined. Another possible storage location for captured CO2 is the deep ocean, but this option is at an earlier stage of development than underground reservoirs; so far only small-scale experiments for preliminary investigation have been carried out (Herzog et al., 2000); the deep ocean is chemically able to dissolve up to 1800GtC (Sato, 1999). An indication of the global capacities of the major storage options is given in Table 3.34. The capacities of these reservoirs are subject to substantial uncertainty, as purposeful exploration has only been conducted in some parts of the world so far. Other published estimates of the global capacity for storage in underground aquifers range up to 14,000GtC (Hendriks, 1994). Other methods of CO2 storage have been suggested but none are competitive with underground storage (Freund, 2000).

Table 3.34: Some natural reservoirs which may be suitable for storage of carbon dioxide
Freund, 1998; Turkenburg, 1997)
Reservoir type
Storage option
Global capacity
Below ground Disused oil fields
  Disused gas fields
  Deep saline reservoirs
  Unminable coal measures
Above ground Forestry
1.2 GtC/yr
Ocean Deep ocean

Substantial amounts of CO2 are already being stored in underground reservoirs:

The cost of CO2 transport and storage depends greatly on the transport distance and the capacity of the pipeline. The cost of transporting large quantities of CO2 is approximately US$1-3/t per 100km (Ormerod, 1994; Doctor et al., 2000). The cost of underground storage, excluding compression and transport, would be approximately US$1-2/tCO2 stored (Ormerod, 1994). The overall cost of transport and storage for a transport distance of 300 km would therefore be about US$8/tCO2 stored, equivalent to about US$10/t of emissions avoided (US$37/tC).

If the CO2 is used for enhanced oil recovery (EOR) or enhanced coal bed methane production (ECBM), there is a valuable product (oil or methane, respectively) which would help to offset the cost of CO2 capture and transport. In some EOR or ECBM projects, the net cost of CO2 capture and storage might be negative. Other ideas for utilizing CO2 to make valuable products have not proved to be as useful as sequestration measures, because of the amount of energy consumed in the process and the relatively insignificant quantities of CO2 which would be used.

If no valuable products were produced, the overall cost of CO2 capture and storage would be about US$40-60/t CO2 emissions avoided (150-220/tC). As with most new technologies, there is scope to reduce these costs in the future through technical developments and wider application.

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