EXECUTIVE SUMMARY 181
4.1 Introduction 181
4.2 Pipeline systems 181
4.2.1 Pipeline transportation systems 181
4.2.2 Existing experience 182
4.2.3 Design 184
4.2.4 Construction of land pipelines 184
4.2.5 Underwater pipelines 185
4.2.6 Operations 185
4.3 Ships for CO2 transportation 186
4.3.1 Marine transportation system 186
4.3.2 Existing experience 186
4.3.3 Design 186
4.3.4 Construction 186
4.3.5 Operation 187
4.4 Risk, safety and monitoring 187
4.4.1 Introduction 187
4.4.2 Land pipelines 187
4.4.3 Marine pipelines 188
4.4.4 Ships 188
4.5 Legal issues, codes and standards 189
4.5.1 International conventions 189
4.5.2 National codes and standards 189
4.6 Costs 190
4.6.1 Costs of pipeline transport 190
4.6.2 Costs of marine transportation systems 190
Transport is that stage of carbon capture and storage that links sources and storage sites. The beginning and end of 'transport' may be defined administratively. 'Transport' is covered by the regulatory framework concerned for public safety that governs pipelines and shipping. In the context of long-distance movement of large quantities of carbon dioxide, pipeline transport is part of current practice. Pipelines routinely carry large volumes of natural gas, oil, condensate and water over distances of thousands of kilometres, both on land and in the sea. Pipelines are laid in deserts, mountain ranges, heavily-populated areas, farmland and the open range, in the Arctic and sub-Arctic, and in seas and oceans up to 2200 m deep.
Carbon dioxide pipelines are not new: they now extend over more than 2500 km in the western USA, where they carry 50 MtCO2 yr-1 from natural sources to enhanced oil recovery projects in the west Texas and elsewhere. The carbon dioxide stream ought preferably to be dry and free of hydrogen sulphide, because corrosion is then minimal, and it would be desirable to establish a minimum specification for 'pipeline quality' carbon dioxide. However, it would be possible to design a corrosion-resistant pipeline that would operate safely with a gas that contained water, hydrogen sulphide and other contaminants. Pipeline transport of carbon dioxide through populated areas requires attention be paid to design factors, to overpressure protection, and to leak detection. There is no indication that the problems for carbon dioxide pipelines are any more challenging than those set by hydrocarbon pipelines in similar areas, or that they cannot be resolved.
Liquefied natural gas and petroleum gases such as propane and butane are routinely transported by marine tankers; this trade already takes place on a very large scale. Carbon dioxide is transported in the same way, but on a small scale because of limited demand. The properties of liquefied carbon dioxide are not greatly different from those of liquefied petroleum gases, and the technology can be scaled up to large carbon dioxide carriers. A design study discussed later has estimated costs for marine transport of 1 MtCO2 yr-1 by one 22,000 m3 marine 4.2.1 Pipeline transportation systems tanker over a distance of 1100 km, along with the associated liquefaction, loading and unloading systems.
Liquefied gas can also be carried by rail and road tankers, but it is unlikely that they be considered attractive options for large-scale carbon dioxide capture and storage projects.
(liquefied petroleum gas) and LNG (liquefied natural gas). This existing technology and experience can be transferred to liquid CO2 transport. Solidification needs much more energy compared with other options, and is inferior from a cost and energy viewpoint. Each of the commercially viable technologies is currently used to transport carbon dioxide.
Research and development on a natural gas hydrate carrying system intended to replace LNG systems is in progress, and the results might be applied to CO2 ship transport in the future. In pipeline transportation, the volume is reduced by transporting at a high pressure: this is routinely done in gas pipelines, where operating pressures are between 10 and 80 MPa.
A transportation infrastructure that carries carbon dioxide in large enough quantities to make a significant contribution to climate change mitigation will require a large network of pipelines. As growth continues it may become more difficult to secure rights-of-way for the pipelines, particularly in highly populated zones that produce large amounts of carbon dioxide. Existing experience has been in zones with low population densities, and safety issues will become more complex in populated areas.
The most economical carbon dioxide capture systems appear to favour CO2 capture, first, from pure stream sources such as hydrogen reformers and chemical plants, and then from centralized power and synfuel plants: Chapter 2 discusses this issue in detail. The producers of natural gas speak of 'stranded' reserves from which transport to market is uneconomical. A movement towards a decentralized power supply grid may make CO2 capture and transport much more costly, and it is easy to envision stranded CO2 at sites where capture is uneconomic.
A regulatory framework will need to emerge for the low-greenhouse-gas-emissions power industry of the future to guide investment decisions. Future power plant owners may find the carbon dioxide transport component one of the leading issues in their decision-making.
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