Whether or not carbon capture and storage (CCS) achieves commerciality in the next decade remains to be seen, but the Australian Government is clearing committed to developing several multimillion tonne per annum (MMt/a) projects. There is work to be done in all aspects of CCS to enable this to happen by 2020, and the transportation component is no different.

The US experience

While there is approximately
2,500 kilometres of carbon dioxide pipelines in the United States, transporting 47 MMt/a, the experience developed through these projects does not mean the transportation of carbon dioxide for CCS projects is a well defined proposition.

Generally, the existing US pipelines transport mainly naturally occurring, relatively pure carbon dioxide to be used in onshore enhanced oil recovery (EOR). EOR tends to yield an additional 4–5 barrels of oil for each tonne of carbon dioxide injected into a reservoir, providing a significant economic driver for these projects.

CCS projects will differ significantly from these, focusing mainly on anthropogenic sources from major emitters such as fossil fuel power plants, and the transport infrastructure will require long distance onshore and offshore pipelines.

Carbon dioxide specifications

The fossil fuel power plants at the source of CCS projects will produce carbon dioxide with varying combinations of impurities depending on the capture technology used.

These impurities have significant implications for the transportation of carbon dioxide and need to be managed. Some impurities have corrosive properties and implications for pipeline materials, others alter the fluid properties and phase diagrams for supercritical carbon dioxide and can impact the pressurisation of a pipeline.

More research needs to be conducted into the impacts each impurity can have on supercritical carbon dioxide properties. The Australian Pipeline Industry Association (APIA) was fortunate to have Dr Julia Race of Newcastle University in UK, a leading expert on carbon dioxide pipelines, visit in early June and inform several industry forums of her current research, in addition to further work that needs to be done in this regard.

It is important that, when seeking to regulate the emerging CCS industry, the Australian Government allows each case to be considered on its merits.

A national specification for carbon dioxide transportation is not desirable, as the types and quantities of impurities will vary across projects. It is envisaged that the long distance transportation component of the CCS industry will be based on large diameter, open access pipelines and it should be a matter of commercial negotiation between emitters, pipeliners and storers of carbon dioxide as to what specifications are to be allowed in each pipeline.

It is likely that carbon dioxide hubs will arise in areas with a high concentration of carbon dioxide emitters, and there may be sufficiently high levels of common impurities amongst these emitters such that it is more economic to build the infrastructure to accommodate them rather than build a processing facility at each emitter.

Safety considerations

While a catastrophic failure of a carbon dioxide pipeline is a highly unlikely event, especially given that the professionalism and expertise of the industry has ensured no major incidents have occurred in natural gas transmission pipelines in Australia, the consequences of such an event need to be understood so as to efficiently design the infrastructure.

Carbon dioxide is not explosive, but the implications of a rupture to a pipeline transporting supercritical carbon dioxide are serious. Carbon dioxide is heavier than air, meaning it can pool in valleys and ‘roll’ down slopes, and is lethal to humans in concentrations above 25–30 per cent. The decompression of a supercritical stream would lead to a rapidly expanding cloud of carbon dioxide in the vicinity and massive temperature drops to below -800 Celcius. To ensure appropriate design of pipeline and easements it is necessary to:
 

  • Determine risk contours for distances from the pipeline leak and therefore the safe distances.
    •  
  • Define zones in which the pipelines should avoid residential areas.
    •  
  • Define acceptable risk levels and exposure limits.

CCS information

Safety considerations and carbon dioxide specifications are just two areas of research required to enable the carbon dioxide pipelines of the CCS industry to achieve the efficiency and reliability enjoyed by natural gas transmission pipelines.

An overview of the technical research required, as presented by Dr Julia Race to an APIA audience in Melbourne, is available on APIA’s website and is recommended to any with an interest in this field.

Additionally, the Government’s Carbon Storage Taskforce has conducted extensive research into the possibilities for the CCS industry in Australia and the actions required to ensure the transportation and storage aspects are ready to go in time. The Taskforce is reporting to the Energy Minister at the end of June and the report should be publicly available by September.

Steve Davies is the Australian Pipeline Industry Association’s Policy Adviser