By Eric Huang    Photo：CANVA

The shipping industry is one of the major contributors to global greenhouse gas (GHG) emissions, accounting for approximately 3% of global carbon dioxide emissions. The International Maritime Organization (IMO) has set ambitious targets to reduce GHG emissions from shipping, pushing the industry to seek innovative methods of cutting carbon. While most efforts have focused on transitioning to low-carbon fuels and improving vessel energy efficiency, another promising solution is the use of Onboard Carbon Capture Systems (OCCS). Carbon capture technology involves capturing carbon dioxide from a ship's exhaust gases before it is released into the atmosphere. The captured CO2 can be stored in tanks onboard or unloaded at designated ports for storage or utilization.

Recent studies have explored the potential and challenges of implementing OCCS. These reports not only demonstrate the technical feasibility of applying carbon capture technology to existing ships but also examine its commercial viability and integration with the broader Carbon Capture, Utilization, and Storage (CCUS) value chain. While OCCS may play a key role in decarbonizing the shipping industry, significant hurdles remain to be overcome.

A study conducted by the Oil and Gas Climate Initiative (OGCI), the Global Maritime Decarbonization Centre (GCMD), and Stena Bulk examined the feasibility of retrofitting OCCS technology on a mid-sized tanker. The results showed that OCCS could reduce carbon emissions by up to 20% annually, with less than a 10% increase in fuel consumption. Despite the high initial cost, estimated at $13.6 million, the study concluded that further research and development could lower costs, making OCCS a more economically viable solution for the shipping industry.

Meanwhile, a study by DNV and TMS Tankers explored various retrofitting scenarios on a Suezmax tanker, demonstrating that advanced OCCS technology could reduce emissions by up to 38%. Although the cost of operating such a system is relatively high, the study found that OCCS is competitive in terms of cost per ton of CO2 reduction compared to alternative solutions like biofuels.

These findings highlight OCCS as a key tool in the shipping industry’s decarbonization efforts. By capturing a significant portion of a vessel’s CO2 emissions, this technology offers a way to extend the economic life of existing ships while complying with increasingly stringent emissions regulations. However, the successful deployment of OCCS will depend on overcoming various technical, commercial, and regulatory challenges.

The engineering study by OGCI, GCMD, and Stena Bulk indicates that the system could capture up to 20% of a ship’s carbon emissions annually. However, the study also identified several technical obstacles, such as the space required for equipment like absorption towers, liquefaction units, and CO2 storage tanks. Additionally, the capture process demands substantial thermal energy and electricity, potentially reducing a ship’s overall energy efficiency. In the DNV and TMS Tankers study, researchers explored three different retrofitting scenarios, with the most advanced configuration using a solvent that regenerates at ambient temperature. This setup could reduce emissions by up to 38%, but it requires optimized mechanical systems and CO2 compression units, underscoring the complexity of implementing state-of-the-art carbon capture technology on ships.

Another major technical challenge is how to unload the captured CO2. Currently, ports lack the infrastructure needed to handle CO2 unloading and storage. As noted by the OGCI and GCMD study, the success of OCCS depends on the development of port infrastructure and policies that promote the permanent sequestration or utilization of CO2.

For OCCS to be widely adopted in the shipping industry, it must not only be technically feasible but also commercially viable. Although the current cost of retrofitting OCCS is high, costs are expected to decrease as the technology matures and scales up. The OGCI and GCMD study estimates that retrofitting the Stena Impero with OCCS currently costs $13.6 million, with a CO2 abatement cost of $769 per ton. While this cost is relatively high, further research and development could lower it, making OCCS more attractive to shipowners.

The shipping industry is at a critical juncture in its decarbonization journey. OCCS presents a promising solution that can reduce carbon emissions while allowing existing ships to continue operating. However, for OCCS to become a mainstream decarbonization option, significant investments in research, development, and infrastructure will be required. If these challenges can be overcome, OCCS has the potential to play a pivotal role in helping the shipping industry meet its emissions reduction targets and contribute to global efforts to combat climate change.

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