October 3 ------ Onboard carbon capture with chemical absorption on large tankers has the best business cases, according to a new report by Mærsk Mc-Kinney Møller Center for Zero Carbon Shipping. The technology has been on the receiving end of a lot of criticism as a costly and inefficient way of reducing CO2 emissions from vessels, especially when compared to its land-based counterpart. Nevertheless, with the ever stricter regulations emerging, OCC is likely to play a role as a bridging solution for vessels that exhaust the potential of energy efficiency initiatives but are yet unable to switch to alternative fuels amid limited availability or other challenges.
The center issued a report detailing the results of multiple case studies looking into the potential of onboard carbon capture, full or partial application, on large ocean-going vessels including container vessels, tankers, and bulkers using carbon-based fuels. The scenarios included newbuild and retrofit cases. The study used post-combustion liquid amine absorption with liquid CO2 storage, the system consisting of a liquid amine absorption capture unit, liquefaction unit, and storage tank. The key considerations taken into account when looking at the potential installation of an OCC were the required dimensions for CO2 storage tanks and their ideal location, as well as the resulting loss of cargo (volume and weight) since in some cases CO2 storage tanks must be installed in cargo holds.
According to the report, carbon reduction percentage does not vary much by vessel type, but fuel selection does have an impact. LNG-fueled vessels can achieve around 78% effective emissions versus around 75% on LSFO and MeOH vessels. On an annual basis, CO2 captured can range from around 22,000 tons for an LR2 tanker to over 97,000 tons for a 15,000 TEU container vessel. With regard to design integration, tankers allow for easier integration (with CO2 tanks on deck) and minimal impact on cargo capacity. Bulk carriers and container vessels present more integration challenges that can lead to significant cargo loss. Ship integration and cost impacts become larger for smaller vessels, so large tankers provide the best business case. The findings show that a very large crude carrier (VLCC) newbuild has the best business case when it comes to the installation of onboard carbon capture.
As disclosed, the CO2 abatement cost for a VLCC newbuild ranges from $220-290/tonCO2 with a tank-to-wake effective CO2 emission reduction of 74-78%. The VLCC’s endurance was based on a Persian Gulf (PG)-Japan round trip (13,400nm, 41days) at a speed of 14.5 knots. The case study assumed that CO2 would be discharged in PG for the VLCC case. For the LSFO fuel type, the OCC system increases CO2 emissions by 42% due to the additional energy demand. In case of LSFO version and maximum carbon capture, about 55% of the additional energy is required for electricity (for circulation pump, liquefaction, etc.) and another 45% for steam (for separation of CO2).
“With an 82% capture rate, the effective emission reduction compared to the base ship CO2 emissions is 74%, which is like the MeOH version at 75% effective emission reduction. The LNG-fueled version can achieve 78% effective emission reduction due to a lower baseline CO2 emissions and lower additional energy requirements,” the report said. “For the VLCC, there is no cargo volume loss, however, the lightweight increase leads to a deadweight decrease of 3-4% (2,800-3,600 tons). There is a small impact on the vessel’s bending moment that can be mitigated by adjusting loading conditions without strengthening the hull structure. As the CO2 storage tanks are placed on deck, the bridge height needs to be increased 4-5 meters.”
Overall, the study found that OCC with chemical absorption was technically feasible and expected to reach commercial availability by 2030. Installation of the OCC results in additional energy requirements and consequently higher total fuel consumption, of up to a 45% increase. The report added that partial carbon capture typically leads to higher CO2 abatement costs due to high initial CAPEX.
That being said, the solution holds the most promise for newbuilds as retrofits are costly and can require major modifications. “Although the emissions reduction potential of OCC is significant, currently its CO2 abatement costs are high. Still, with further development OCC could play a role in the mid-term to reduce the emission intensity of existing fossil-fueled vessels,” the center said, noting that further analyses and developments are required to maximize OCC emission reduction and minimize costs, as well as developing business models that would allow utilization and/or storage of the carbon captured onboard vessels.
Moving forward, challenges that might hinder the technology’s uptake could be delays in the development of a regulatory framework or market to get credit for CO2 reduction, and a lag in infrastructure development on shore. “Although OCC technologies are still in development, they will be commercially available soon and can provide significant emission reductions. As a result, ship owners aiming to decarbonize should assess their mid-term emission reduction targets and consider including OCC if it is an option for their vessel types, sizes, and trades.” As a continuation of this work, the MMMCZCS has initiated an onboard carbon capture working group to study additional OCC technologies, applications, and business models.