Containerized Carbon Capture
A London-based startup, Seabound, has developed a pioneering technology housed within standard shipping containers to tackle the considerable challenge
of CO2 emissions from cargo vessels. This innovative system is designed to capture an impressive 95% of these harmful emissions directly from ship exhausts. Following extensive development and successful pilot tests, Seabound is now on the cusp of its first commercial deployment, preparing to install these specialized containers on a cargo ship. The maritime industry is notoriously difficult to decarbonize, often referred to as one of the 'last hard-to-abate sectors'. While cleaner fuels like green methanol and ammonia are emerging, their availability is limited, and they come with a significantly higher price tag – projected to be two to three times more expensive than conventional fuels. Furthermore, these cleaner alternatives are highly sought after by other industries, creating fierce competition. Adding to the complexity, cargo ships have a long operational lifespan, meaning vessels currently in service cannot easily transition to entirely new fuel types. As the industry gradually shifts towards cleaner alternatives and other low-emission technologies, Seabound's approach focuses on addressing the pollution generated by the vast number of ships already operating globally. In 2024 alone, cargo ships were responsible for emitting 973 million metric tons of CO2, accounting for approximately 2.5% of worldwide emissions.
From Exhaust to Limestone
Within Seabound's modular containers lies a sophisticated yet straightforward process: millions of marble-sized pellets of calcium hydroxide, commonly known as lime. These containers are strategically positioned near the ship's engines and are integrated with the exhaust system. As exhaust gases flow through the lime pellets, a chemical reaction occurs, transforming the CO2 and soot into limestone, or calcium carbonate. Each pellet undergoes a subtle color change, shifting from pure white to an off-white hue, visually indicating the capture of carbon and particulate matter. A single container is capable of processing roughly a day's worth of pollution generated by a ship during its voyage. For longer journeys, multiple modules are interconnected to ensure continuous capture. Upon reaching port, a standard crane can easily offload these containers, which essentially become 'fancy boxes of rocks,' as described by the company's CEO. The resulting limestone has potential applications as a building material. Alternatively, Seabound's process can be reversed: the captured CO2 can be extracted from the limestone for sequestration or repurposed into new fuels and chemicals. In this regenerative cycle, the processed lime can be reloaded into the containers and returned to service on ships, ready to capture more carbon. The company's inaugural customer, Heidelberg, is set to implement this technology on a cement ship later this year, utilizing the captured limestone in their cement production process, thereby creating a closed-loop system.
Efficient and Cost-Effective Capture
Seabound's core carbon capture mechanism, termed calcium looping, shares similarities with technologies employed by some direct air capture firms. However, by directly connecting to a ship's exhaust pipe, Seabound achieves a significantly higher efficiency in CO2 capture. The process is further enhanced by the waste heat generated from the ship's engines, which accelerates the reaction. This approach contrasts with the often costly carbon capture systems found in industrial facilities. Seabound's technology is designed for simplicity, allowing for relatively low operational expenses once scaled up, according to its CEO. The company has projected that their method could be one to two orders of magnitude more economical than other carbon capture solutions being developed for the maritime sector. While the production and transportation of lime do generate some emissions prior to its use, Seabound aims to mitigate this by sourcing lower-carbon 'green lime' in the future. Initially, the system can capture up to 95% of CO2 directly from the exhaust stack; however, the overall efficiency of the entire process, considering all stages, is expected to be around 80%. With future advancements, it is anticipated that the process could achieve a 90% reduction in emissions. This technology offers a vital pathway for cleaning up the emissions from the vast existing fleet of cargo ships.
Driving Adoption and Future Potential
Seabound has successfully secured approximately £8.5 million (equivalent to $11.6 million) in funding, comprising both equity investments and grants from shipping companies and climate technology venture capitalists. The company is initially focusing its efforts on European markets, where stringent environmental regulations are compelling the shipping industry to expedite emissions reductions. Within the European Union, maritime transport is now fully integrated into the EU's emissions trading scheme, and supplementary policies are increasing penalties for emissions from fuel combustion by ships. Additionally, shipping companies are experiencing mounting pressure from major clients, such as Ikea, which have set ambitious climate targets. Seabound's strategic plan involves concentrating on shorter shipping routes within Europe, establishing operational bases at key ports where vessels refuel. Future expansion is planned for Asian markets. Despite a global policy setback in 2025 when the International Maritime Organization deferred a vote on a proposed global carbon price for shipping, the organization is scheduled to revisit the proposal later in the year. Globally, there are approximately 60,000 cargo ships currently in operation. While retrofitting all of them would be a considerable undertaking, the industry has demonstrated its capacity for major adaptations in the past, such as the widespread adoption of sulfur scrubbers to capture other pollutants. A concern sometimes raised is the potential for a 'moral hazard,' where companies might delay adopting zero-emission technologies if they can rely on carbon capture as an alternative. However, the CEO emphasizes that given the slow progress of alternative fuels and other solutions, carbon capture remains an essential interim measure. She notes that the projected timeline for future fuels has not significantly changed since the company's inception. Importantly, even if alternative fuels become widely available, Seabound's technology could still be adapted to capture emissions from those cleaner fuels, potentially enabling 'carbon-negative shipping'.
