The Status and Challenges of CO₂ Shipping Infrastructures

Publication Overview

Large-scale CO₂ storage will entail substantial transportation of CO₂ from either point-sources or hub collection points to geological formations capable of storing thousands of tonnes of CO₂ in supercritical form. In many parts of the world the most suitable storage options for large-scale capacity will be in offshore formations such as the North Sea. Consequently, it is important to build an understanding of the most suitable techno-economic solutions for the trans-shipment of CO₂ from shore facilities to offshore storage locations. This study has explored a series of options to gain a more detailed comparison of shipping CO₂ either directly by sea tanker to a storage site, or via an intermediate stage, to a shore facility in closer proximity to a storage site prior to transfer via pipeline. These options have also been compared to direct transfer via pipeline.

Publication Summary

• The results from this study demonstrate that for long distance transport of low volumes of CO₂(~1-2 Mtpa), such as in cross-border shipping from several industrial CCS clusters acrossEurope, shipping can provide a cost-effective option.
• Based on the four different scenarios modelled in this study, more CO₂ could be stored annuallyby shipping to an intermediate port, and then transporting CO₂ to a storage site via a pipeline,compared with direct delivery to the site by tanker.
• Of the four scenarios modelled here, based on a shipping distance of 1,000 km, there is littlecost advantage from increasing the ship size above 10,000 tCO₂. Conversely, there is also littlepenalty in cost by using larger ships. However, the optimum ship size will be highly dependenton the flow rate (Mtpa). Ideally, size and capacity could be customised for each specificlogistics chain.
• A comparison of the levelised cost of four different scenarios conducted in this study suggeststhat direct injection at a storage site from a ship is the most cost-effective solution (32 €/t CO₂).The cost advantage may vary under different scenarios.
• Transfer of CO₂ from a tanker into a floating storage injection (FSI) unit is the least costeffective solution even though it can allow continuous injection (41 €/t CO₂). Moreover, thissystem is unproven and less well understood compared with onshore facilities therefore directcomparison needs to be treated with caution.
• The modification of LPG tankers for CO₂, or dual purpose, will be influenced by the contrastin fluid density of the different gases. Consequently, only 50-60% of a tank capacity designedfor LPG can be used for CO₂. Partially filled cargo tanks will also have a structural impact ona ship and its motion.
• Tankers specifically designed for CO₂ transportation can be optimised for maximum capacityand investment cost.
• A comparison between CO₂ delivered by sea tanker and a pipeline to an offshore storage site,based on minimum unit costs, shows that the pipeline option is cheaper over shorter distances.The break-even distance depends on the volume of CO₂ and whether tankers are pre-pressurisedor non-pressurised (see Figure 9).
• A review of the legal instruments (international treaties, EU law & Norwegian Law), that relateto the movement of CO₂, shows that there are no evident showstoppers to the internationalshipment of CO₂.
• A decision taken at the 14th meeting of the Contracting Parties to the London Protocol on 7th –11th October 2019 means that Contracting Parties who choose to are able to legally transshipCO₂ for storage.
• An unfortunate result of having two monitoring reporting and verification (MRV) regimes forCO₂, is that ship operators will have to manage two separate reporting schemes for the fuel thatthey use. The European Commission has reviewed the MRV regulation and is consideringpotential alignment with the International Maritime Organisation Data Collection System (IMODCS).