12.03.2024

Series of articles Carbon Management: How can CO2 be transported?

With the European climate neutrality targets for 2050 firmly in place, carbon management is moving into the focus of sustainable environmental practices. The challenge is not only to reduce emissions, but also to effectively manage unavoidable emissions. This requires the use of carbon capture technologies that enable either underground storage (Carbon Capture and Storage – CCS) or integration into a closed carbon cycle (Carbon Capture and Utilization – CCU). This series of articles provides an overview of carbon capture technologies, possible utilization of CO2, storage methods, transportation options and political efforts in the context of carbon management.

Figure 1: Factsheet for the transportation of carbon dioxide. The calculation of pipeline costs are based on literature values in [1], [2], [3] [4] and transportation conditions according to [5].

Why does CO2 need to be transported?

One important measure for achieving the climate neutrality targets is the capture of unavoidable CO2 emissions. There are two options for the captured CO2:

  1. It can be permanently stored underground so that it can no longer be released into the atmosphere (Carbon Capture and Storage – CCS, see article How can CO2 be stored?)
  2. It can be used as a carbon source, e.g. in basic chemicals (Carbon Capture and Utilization – CCU, see article What are possible ways to use CO2?)

Usually, there are neither storage facilities nor sites for the further use of CO2 directly at the site of capture. It is therefore necessary to transport the CO2 to the possible sinks. Sites for possible CO2 storage are located in northern Europe, offshore in the North Sea, but also in the Mediterranean and onshore in south-eastern Europe. In the future, refineries could be possible locations for the further use of CO2 for basic chemicals or for the production of synthetic.

Options for transportation

The current demand for the use of CO2 in Europe is primarily covered by truck trailers. The food industry in particular has high purity and traceability requirements [6], meaning that transportation in gas cylinders and liquid tanks by truck remains the best option. A single truck trailer can hold up to 18 tons of CO2 [3].

The wagon of a freight train has a capacity of approx. 62 tons of CO2, so that transport capacities of up to 190 kt per year over long transport routes are possible by using a freight train [14].

In view of the large quantities of CO2 that will be produced in the future, transporting CO2 by truck and rail is not a scalable option. In addition, the use of freight trains to transport large quantities of CO2 leads to a high utilization of the rail network. This is a particular problem for locations with large quantities of CO2 without storage facilities, as these quantities of CO2 have to be transported continuously and reliably on a daily basis. Nevertheless, trailer transport via truck and rail can play an important role for smaller point-to-point solutions and for the ramp-up of a CO2 infrastructure in the value chain [3].

Transportation by ship is particularly important in coastal areas with offshore storage facilities. The ships are designed to transport CO2 in the liquid phase and are therefore constructed in a similar way to LPG ships. On average, a ship the size of an LPG ship could therefore transport approx. 45 kt of CO2 [3]. Port terminals can handle up to 7 million tons of CO2 per year, according to the CO2next project.

When transported in pipelines, CO2 can be transported in both the gaseous and liquid phase, depending on the pressure and temperature in the pipelines. Figure 1 shows the phase diagram of CO2 at the bottom left.

The gaseous phase has a low density, which requires large pipe diameters and therefore leads to high costs in new construction. Accordingly, gaseous transport is a sensible option, especially for feeding small quantities of CO2 into a transport network. The lower pressure of gaseous transport makes it possible to convert existing natural gas pipelines to transport CO2 [7]. Cost savings of up to 80 percent are possible despite the costs incurred for integrity testing of the pipelines.

Due to its high density, a large transport capacity can be achieved in the liquid phase with small pipe diameters and is therefore the preferred phase for transporting large quantities of CO2. As the degree of purity of CO2 influences its thermodynamic properties [5] , a pressure of approx. 150 bar is required to maintain the liquid phase at an average ground temperature of 15°C throughout the entire transportation process. Existing natural gas pipelines are not designed for these pressures, meaning that new pipelines need to be built for pipeline-based transportation in the liquid phase.

The German Technical and Scientific Association for Gas and Water (DVGW e.V.) is currently working on a set of regulations for the transportation of CO2. The purity requirements for the pipeline-based transportation of CO2 are within the range of > 95% by volume, as impurities can lead to corrosion in the pipes [8].

Costs for transportation

The costs for the construction of new pipelines and their operation are shown for various diameters in the table at the top right of Figure 1. The calculation of the investment costs is based on literature values in [1], [2], [3] at transport conditions of 150 bar and 15°C (liquid). The calculation of the operating costs is based on [4] with an assumed electricity price of 0.225 €/kWh. A transport pipeline with a diameter of 800 mm can transport CO2 in liquid form at ground temperature (15° C) and a pressure of 150 bar and thus has a transport capacity of 15 Mt of CO2 per year. The investment costs for the pipeline construction amount to around 342 M€/100km. The operating costs for such a section of pipeline amount to approx. 48 M€ per year.

About 80% of the costs could be saved by converting an existing natural gas pipeline. However, since the use of natural gas pipelines is only suitable for the transportation of CO2 in a gaseous phase with low density, a pipeline with a diameter of 800 mm can only transport approximately 3 Mt of gaseous CO2 per year.

Due to economies of scale, the cost of transporting CO2 by truck and rail is between three and ten times higher per ton than pipeline transport [3]. Ship transport is an economical alternative to pipeline transport for distances over 1,000 km. Especially for comparatively small quantities of CO2 over long distances to the storage site, ship transport can be cheaper than an offshore pipeline, as pipelines require a continuous flow and are highly cost-dependent on distance [9].

As there are currently no unbundling regulations, the construction and operation of a CO2 pipeline network is attractive for various players. It could be possible to refinance the costs incurred via network charges, similar to the financing of natural gas networks. However, the problem could arise at the beginning of infrastructure development that there are only a few users. As a result, these few users might have to pay high grid fees, which in turn would represent a risk for the grid operator if individual users were to disappear [10]. The German government is therefore considering targeted start-up funding in the form of state subsidies for the ramp-up. Details of this are being worked out in the German Carbon Management Strategy [15].

Projects for the transport of CO2

In Germany, the grid plans of transmission system operator Open Grid Europe GmbH (OGE) are the most advanced. OGE is planning to build a Germany-wide CO₂ transportation grid that extends from Belgium via the Netherlands, northern Germany and Denmark to the North Sea. The planned transport network consists of the WHVCO2logne and Delta Rhine Corridor and the Elbe estuary and Rhine district clusters, among others. The aim is to rapidly develop the export options in Wilhelmshaven, Rotterdam and Antwerp/Zeebrugge. The network is intended to transport CO2 for storage in the North Sea. The collection network is being planned from north to south, with possible CO2 volumes from the south and transit volumes from neighboring countries already being taken into account in the design of the northern pipelines. The connection of the network in southern Germany is planned for the middle to second half of the 2030s [11].

The transmission system operator bayernets is already planning the first section of the “co2peline” project in southern Germany and Austria [12]. In cooperation with Rohrdorfer Zement, the project initially involves the construction of a new CO2 pipeline from the cement site in Rohrdorf for possible utilization in the Bavarian chemical triangle of Burghausen.

Numerous CO2 transport projects are also planned in an international context. As part of the Longship project, CO2 is captured at industrial sites on the Norwegian mainland and initially transported by ship to an onshore terminal on the west coast of Norway as part of the “Northern Lights” project. From there, the liquid CO2 is piped to an offshore storage site in the North Sea. In addition to Northern Lights, numerous other CO2 transport projects are listed as “Project of Common Interest” (PCI) [13]. The majority of them are planning to use a multimodal transport concept, i.e. a combination of pipeline, ship and trailer transportation.

Literature

[1] McCoy, Sean et al.: An engineering-economic model of pipeline transport of CO2 with application to carbon capture and storage. In: International Journal of Greenhouse Gas Control 2. Pittsburgh: Carnegie Mellon University, 2008.

[2] Energy Policies Beyond IEA Countries Ukraine 2012. Paris: International Energy Agency (IEA) Publications, 2012

[3] Carbon Capture, Use, and Storage (CCUS) Report – Volume III: Analysis of CCUS Technologies – Chapter 6: CO2 Transport. Washington D.C., USA: National Petroleum Council, 2021.

[4] Zhang, Z.X. et al.: Optimization of pipeline transport for CO2 sequestration. In: Energy Conversion and Management 47 (6). Brisbane: The University of Queensland, 2006.

[5] Munko, Björn: Relevance of Pipelines for CO2 Transport. In: ECRA 2nd Online Conference on CO2 Infrastructure; Duesseldorf, Germany: Deutscher Verein des Gas- und Wasserfaches e. V.

[6] MINIMUM SPECIFICATIONS FOR  FOOD GAS APPLICATIONS (MINIMUM SPECIFICATIONS FOR  FOOD GAS APPLICATIONS). Ausgefertigt am 2020-01-01; Brüssel, Belgien: EIGA, 2020.

[7] Wachsmuth, Jakob: Transformation der Gasinfrastruktur zum Klimaschutz. Dessau-Roßlau, Germany: Umweltbundesamt, 2023.

[8] Erfurth, Jens: Development of pipeline infrastructure for CO2 transport, Germany. In: 2nd ECRA Online Conference on CO2 Infrastructure; Duesseldorf, Germany: Open Grid Europe GmbH.

[9] Al Baroudi, Hisham: A review of large-scale CO2 shipping and marine emissions management for carbon capture, utilisation and storage. In: Applied Energy Volume 287. Cranfield, UK: Centre for Thermal Energy and Materials (CTEM), School of Water, Energy and Environment (SWEE), Cranfield University, 2021.

[10] Altrock, Martin: Rechtliche Rahmenbedingungen für Carbon Capture and Storage (CCS) in  Deutschland – Gutachten. Brussels, Belgium: Bellona Europa AISBL, 2022.

[11] CO₂-Transportnetz – Unser CO₂-Transportnetz startet. In https://oge.net/de/co2/co2-netz. (Abruf am 2023-8-18); Essen: Open Grid Europe GmbH, 2023.

[12] co2peline – carbon dioxid transport. In https://www.co2peline.com/. (Abruf am 2023-08-18); München: Bayernets GmbH, 2023.

[13] THE UNION LIST OF PROJECTS OF COMMON INTEREST AND PROJECTS OF  MUTUAL INTEREST (‘UNION LIST’) (Annex PCI PMI list). Ausgefertigt am 2023-11-28, Version vom 2023-12-28; Brussels – Belgium: European Commission, 2023

[14] Siegemund, Stefan: CO2-transport via Rail. From a niche to a large volume market. Opportunities, challenges, and necessary actions. In: 2nd ECRA Online Conference on CO2 Infrastructure; Duesseldorf, Germany: VTG.

[15] Carbon Management Strategie – „FAQ zu CCS und CCU“, Berlin: BMWK, 2024