(80d) Evaluating on-Board CO2 Capturing Methods for the Ship with Outlook on Storage and Utilization Options

Today there are around 60,000 large-scale ships that are moving in the oceans contributing to 2.9% of total global CO₂ emissions. They are faced with a significant challenge to meet the strict and ambitious upcoming regulations planned by the International Maritime Organization (IMO) to reduce carbon intensity by at least 40% by 2030 and aim towards 70% by 2050. CO₂ capturing technology options available from on-shore applications do not fit directly the ship requirements in terms of space limitation, limited resources, and sources of energy, and it is mobile and dynamic not like the typical stationary emission sources of power plants and those in the chemical industry.

This work aims first at (1) reviewing the published studies concerning onboard ship carbon capture, storage, and utilization and synthesizing gaps in existing knowledge to provide a focus for future studies. Then (2) it evaluates five captured CO2 technologies from the perspective of the shipping industry as absorption, adsorption, membrane, cryogenic, and chemical looping. Till now, a limited number of studies have been carried out for onboard CO2 capturing mainly focused on absorption with MEA as the most studied solvent. Techno-economic studies showed a wide range of achieved capture rates for onboard capture systems from 54% to 90% and wide costs ranging from 77.5 to 389 €/ton CO₂. In addition, seven CO₂ storage conditions were reported in the literature for onboard capture systems. Our work reviewed the potential of CO₂ capture technologies, highlighted the ship requirements, and proposed potential energy integrations between the ship energy system and CO₂ capture unit. A visualization was developed and demonstrated to quantify the emitted CO₂ per distance crosses for containerships. It is shown as the number of lost Twenty Equivalent Units (TEUs) on a containership per 1000 km crossed in a sailing mode. Reports for onboard CO₂ utilization work was limited to one study so far. We listed two high-level utilization routeways for captured CO₂ on a ship. Direct utilization works by converting CO₂ to a fuel or chemical while in-direct utilization integrates captured CO₂ with onshore applications.

In the second part, the integration of the above CO₂ capture technologies, compression, and storage as well as utilization options are explored in the context of the existing energy system onboard an LNG carrier ship. Close attention is paid to achieving efficient heat and power integration for overall energy efficiency as well as vessel-specific design constraints including space limitations and motion. The work culminates in the identification of the most suitable technologies and an outlook on required future development efforts.