Project COLOSSUS reveals where onboard carbon capture sits within maritime decarbonisation strategies and emerging regulatory frameworks
The prospect of using onboard carbon capture and storage (OCCS) as a decarbonisation tool in commercial shipping has attracted both attention and investment. Yet questions remain about its actual emissions reduction potential when examined beyond the vessel. Project COLOSSUS delivers a comprehensive lifecycle assessment (LCA) study of OCCS technologies and their associated carbon value chains.
The study evaluates not only emissions produced and captured onboard, but also those associated with fuel production and the eventual storage or utilisation of captured CO2. GCMD described the objective as an attempt to “provide a coherent emissions accounting framework across upstream and downstream stages of the carbon lifecycle.”
To assess the emissions reduction potential of carbon captured onboard a vessel, Project COLOSSUS built upon an earlier study called Project REMARCCABLE, a collaboration between GCMD, the Oil and Gas Climate Initiative (OGCI), and Stena Bulk.
In that study, a conceptual and front-end engineering design study and cost estimate were conducted to retrofit a monoethanolamine (MEA)-based OCCS system onboard the Stena Impero, an MR tanker. The vessel, operating on heavy fuel oil (HFO), regenerates the solvent and liquefies the onboard captured CO2. It served as the reference vessel for Project COLOSSUS.
A practical limit of 40% gross capture was imposed due to volume constraints of the CO2 storage tank: “A 90% capture rate may be technically achievable, but storing such volumes of liquid CO2 onboard a tanker is unfeasible,” the study notes. Under these conditions, and considering energy penalties from operating the OCCS system, the net well-to-wake (WtW) emissions reduction is calculated at 28.5%. The estimated cost of avoided CO2 under this configuration, including transporting the captured CO2 within a range of 1,000 km to permanent storage, ranges from US$269 to US$405 per tonne.
