Onboard Carbon Capture for Circular Marine Fuels

The transition to low- and zero-carbon fuels is the primary driver for reducing emissions in the maritime industry, with methanol and natural gas emerging as the most promising options. However, carbon-based fuels will continue to emit considerable amounts of pollutants during their use phase. This work explores the application of circular economy principles in the shipping industry by integrating carbon capture and utilization technologies. Specifically, we propose a closed-loop system where carbon dioxide (CO₂) generated onboard is captured using a chemical absorption technology and stored until the ship reaches a port. The captured CO₂ is then unloaded and transported to a fuel production facility, where it reacts with electrolytic hydrogen to regenerate the required propulsion fuel. Here, we evaluate the economic, technical, and future environmental viability of methanol and natural gas as circular marine fuels. Our findings indicate that natural gas could achieve a 65% reduction in CO₂ emissions by 2050, while methanol could lead to 55%, both with a 91% carbon capture rate. However, there is an economic premium of 339 USD tonCO₂ ^-1 for methanol and 260 USD tonCO₂ ^-1 for natural gas. Additionally, the shift to circular fuels is expected to increase costs by a factor of 3-6 compared to conventional operations.