(110c) Shipping Decarbonization: Energy Assessment of Onboard CO2 Capture Technologies

The international shipping industry’s greenhouse gas (GHG) emissions are expected to reach 1,500 million tonnes of CO₂ equivalent per annum in the coming years due to the increase in global seaborne trade activities [1]. This would make the shipping industry one of the top 5 GHG emitters, surpassing Japan and ranking below only Russia, India, the United States, and China [2]. Furthermore, the World Economic Forum (WEF) has predicted that GHG emissions from the shipping industry could increase by up to 250% by 2050 if no substantial measures are taken by stakeholders and policymakers [3]. Recently, the International Maritime Organization (IMO) has set new targets aiming to reduce GHG emissions by 20% by 2030, 70% by 2040 compared to 2008 levels, and to achieve net-zero emissions by 2050 [4]. Achieving these goals will require exploring various technologies and solutions to enhance the ships’ efficiency and reduce GHG emissions. The shipping industry has already implemented the operational measures, such as optimizing vessel speed [5]. In addition, the adoption of alternative zero-carbon fuels is still lagging behind due to the technical and economic constraints [5]. Consequently, onboard CO₂ capture systems present an attractive option to reduce CO₂ emissions on the ship [6] and meet the IMO’s 2030, 2040, and 2050 goals.

The research into onboard CO₂ capture is still in its early stages. Few studies have investigated the feasibility of absorption, membrane separation, and cryogenic technologies for capturing CO₂ onboard and storing it in a liquid form. A comprehensive integration of energy between the ship’s main engine and the carbon capture system requires considering the heat and power requirements, which have not been addressed in previous work. Therefore, our study aims to investigate onboard CO₂ capture technologies for an LNG carrier vessel powered by LNG fuel. A comparative energy assessment was conducted to understand the performance of four alternative CO₂ capture technologies: absorption, membrane separation, adsorption, and cryogenic separation. This assessment involved the development of heat and power integration concepts to recover heat from the flue gas stream and meet the heat and power needs of CO₂ capture and compression. Organic Rankine cycles (ORCs) were applied as a heat-to-power conversion technology to fulfill the work requirements in the capture and compression stages. Finally, the liquefaction and storage step was achieved using the LNG fuel stream as a cryogenic source to cool and store the captured CO₂.

In conclusion, the results show that adsorption is one of the promising technologies for onboard applications, achieving a capture rate of approximately 50% using the available energy onboard. This work highlights the importance of thermal-driven CO₂ separation technologies, i.e. absorption and adsorption, in significantly reducing CO₂ emissions from the shipping fleet without the need to burn extra fuel onboard.

Acknowledgements: This work was made possible by joint funding provided by the American Bureau of Shipping (ABS) and Texas A&M University at Qatar.

References:

[1] L. C. Law, E. Mastorakos, and S. Evans, “Estimates of the Decarbonization Potential of Alternative Fuels for Shipping as a Function of Vessel Type, Cargo, and Voyage,” Energies, vol. 15, no. 20, p. 7468, Oct. 2022, doi: 10.3390/en15207468.

[2] J. Friedrich, M. Ge, A. Pickens, and L. Vigna, “This Interactive Chart Shows Changes in the World’s Top 10 Emitters,” World Resources Institute. [Online]. Available: https://www.wri.org/insights/interactive-chart-shows-changes-worlds-top-...

[3] WEF, “New Coalition Aims to Make Zero-Emissions Shipping Plain Sailing,” 2019.

[4] DNV, “IMO MEPC 80: Shipping to reach net-zero GHG Emissions by 2050,” 2023.

[5] G. Mallouppas and E. Ar. Yfantis, “Decarbonization in Shipping Industry: A Review of Research, Technology Development, and Innovation Proposals,” J. Mar. Sci. Eng., vol. 9, no. 4, p. 415, Apr. 2021, doi: 10.3390/jmse9040415.

[6] ABS, “INSIGHTS INTO ONBOARD CARBON CAPTURE,” 2022.