Carbon Capture Cleans Up Shipping

The Dirty Secret of the Seas: Can a Box of Lime Clean Up Global Shipping?

A London-based startup, Seabound, is pioneering a novel approach to slash the immense carbon footprint of cargo fleets. By adapting established technology into a simple, modular system, they aim to offer a pragmatic answer for one of the planet's most polluting industries.

In Chingford, a suburb of London, an industrial park located near the River Lea presents an unlikely setting for a profound change to unfold. Within this space, a group of business innovators is fine-tuning an unassuming steel container with a monumental goal: to help purify the global shipping sector. This industry is a cornerstone of the world economy, with around 100,000 vessels traversing the oceans at any given moment, but it comes at a steep environmental cost. Maritime transport generates approximately three percent of worldwide greenhouse gas pollution, a figure surpassing the entire aviation industry.

The box contains thousands of tiny pellets, each the size of a cherry, composed of quicklime. A generator running on diesel funnels exhaust into one end of the container, where the lime material absorbs carbon from the fumes. This initiates a chemical process that ultimately converts the substance into ordinary limestone. Seabound, the firm behind this creation, aims to sequester significant quantities of carbon right from the decks of freight vessels, presenting a tangible way to mitigate the striking pollution of this essential sector.

An Idea Born from a Climate Warning

The driving force behind this venture is Alisha Fredriksson, a youthful business innovator whose professional path took a decisive turn. Originally dreaming of becoming a physician, her perspective shifted dramatically after she reviewed a key report issued by the Intergovernmental Panel on Climate Change. The document starkly detailed the differing global consequences of 1.5 degrees Celsius versus 2 degrees Celsius of warming.

This realisation spurred Fredriksson into action. She understood that the challenge of our changing climate would impact everyone globally, and if her goal was large-scale social benefit, tackling this issue was the most effective contribution she could make. The question then became how to do it. This led to the founding of Seabound in 2021, together with her co-founder, Roujia Wen, a physicist and material scientist whom she met at Minerva University. Their shared vision was to find a practical solution for the hard-to-abate shipping industry.

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Downsizing a Big Idea

The core concept for Seabound emerged from Fredriksson's previous experience at a maritime start-up focused on producing e-methanol as an alternative ship fuel. Ironically, a key challenge was sourcing enough captured carbon dioxide needed to create the synthetic fuel. This sparked the innovative thought of capturing CO2 from ships directly and creating a circular system by feeding it back into the production process.

Fredriksson and Wen decided to miniaturize the established carbon-capture methods that use quicklime, which are commonly used at industrial facilities. They constructed a prototype and quickly attracted significant interest, securing about $4.67 million in investment capital, including from venture capital firms like Lowercarbon Capital and major shipping companies such as Eastern Pacific Shipping. The rapid influx of capital meant they had to move fast, but Fredriksson has confidence that the industry was prepared for a resolution.

From Workshop to the High Seas

The journey from a London test-bed to the open ocean has been swift. Evolving versions of the Seabound container have been tested in Turkish shipyards and, most significantly, on a ship that holds 3,200 containers. During a 21-day expedition that passed through the Suez Canal, the system's efficiency was put to the test.

The trial indicated that a single Seabound unit could successfully trap 78 percent of the carbon dioxide from the exhaust stream that passes through it. In addition, the system captured an impressive 90 percent of the sulfur, a noxious air pollutant that contributes to acid rain and respiratory problems. These results proved that the technology works in a real-world maritime environment, a crucial step towards commercialisation.

Designed for a Working Ship

A key feature of Seabound’s system is its practicality. The newest model is being engineered to the specifications of a conventional 20-foot shipping container, a deliberate design choice that allows it to slot seamlessly among the cargo carried on deck. This modular design means shipowners can stack multiple units, which gives a vessel the ability to progressively enhance its carbon capture capacity based on the length of a voyage and its specific decarbonisation targets.

This flexibility is a significant advantage. It allows shipping companies to begin reducing emissions on their existing vessels without the need for a complete and costly fleet overhaul. The system is essentially a "plug-and-play" solution that can be retrofitted onto the current generation of ships, offering an immediate pathway to lower emissions.

The Green Quicklime Conundrum

When a vessel is in port, the units filled with limestone can be easily offloaded and replaced with fresh containers of quicklime. However, the production of quicklime itself presents an environmental challenge. This material is manufactured by heating limestone to very high temperatures inside kilns. The procedure is energy-demanding and simultaneously liberates the stone's inherent CO2, which makes its creation extremely carbon-heavy.

Seabound is actively looking to procure this "green" quicklime to close this loop. This involves partnering with companies that are developing new methods to produce lime, such as with kilns powered by renewable energy or creating techniques to capture the CO2 that is released so it does not escape into the atmosphere. Innovators like SaltX Technology are developing electric calciners that can create decarbonised lime, a crucial step for the entire value chain to become sustainable.

Navigating a Sea of Regulations

Pressure to decarbonise is mounting on the shipping industry from its global regulator, the International Maritime Organization (IMO). The IMO has set ambitious targets, aiming for a 40% cut in carbon intensity by 2030 and net-zero emissions by 2050. To enforce this, new regulations like the Energy Efficiency Existing Ship Index (EEXI) and the Carbon Intensity Indicator (CII) have been introduced.

The EEXI is a one-time certification for a ship's design, while the CII is an annual operational rating from A to E. Ships that receive poor ratings (D for three consecutive years or E for one year) must implement a corrective action plan. Furthermore, the European Union has its own measures, including the Emissions Trading System (ETS) for shipping, which puts a price on carbon. Seabound's technology offers shipowners a tool to help comply with these complex and tightening rules, improving their CII rating and avoiding potential penalties.

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The Great Decarbonisation Debate

Onboard carbon capture and storage (OCCS) is not without its critics. Some environmental groups and policy experts express concern that such technologies could serve as a reason to extend the use of fossil-based fuels. Blánaid Sheeran, from the nonprofit Opportunity Green, argues that the ability to retrofit current vessels with carbon capture for temporary benefit should not delay the essential move toward genuinely sustainable alternatives like zero-emission fuels.

The fear is that OCCS could become a convenient excuse for inaction, allowing the industry to avoid the more fundamental changes required to reach true net-zero. Critics point out that carbon capture does not eliminate emissions entirely and creates a waste product—the captured CO2—that must be managed, transported, and stored, adding complexity and potential environmental risks.

A Bridge to a Greener Future?

Fredriksson and the Seabound team position their technology not as a permanent silver bullet, but as a vital transitional tool. They argue that with long-term solutions like green ammonia and hydrogen still years away from widespread, affordable adoption, OCCS can bridge the gap. The technology can be fitted to the thousands of vessels already in service, allowing the industry to make significant emission cuts now.

This approach provides an immediate and practical way for shipowners to lower their carbon footprint while the infrastructure and engine technology for new fuels are developed. Seabound contends that its system supports the transition by allowing ships to meet regulatory targets today, buying valuable time for the longer-term solutions to mature.

The Rise of Alternative Fuels

The long-term vision for decarbonising shipping largely revolves around new, cleaner fuels. Green methanol and green ammonia are two of the leading candidates. Green methanol can be produced from biomass or by combining captured CO2 with green hydrogen, making it a carbon-neutral fuel. Green ammonia is created by combining green hydrogen with nitrogen and produces no CO2 when combusted, though it presents challenges related to toxicity.

Many major players in the maritime sector are investing heavily in vessels capable of running on these new fuels. However, scaling up production to meet global demand is a colossal task. It requires a massive increase in renewable energy generation to produce the necessary green hydrogen, making these fuels expensive and not yet widely available.

Harnessing the Power of Wind

In the quest for sustainability, some in the maritime sector are looking to its past for inspiration, with a modern twist. Wind-assisted propulsion systems are making a comeback, not as traditional sails but as high-tech innovations. These include towering, spinning Flettner rotors that use the Magnus effect to generate thrust, and enormous, rigid wing sails that function like aeroplane wings.

Companies are experimenting with these technologies, which can reduce a ship’s fuel consumption by 5% to 25%, depending on the system and the trade route. While not a complete solution, wind assistance can significantly improve the energy efficiency of a vessel, complementing other decarbonisation efforts and reducing reliance on fossil fuels.

The Cost of Going Green

Ultimately, the path to a cleaner shipping industry will be shaped by economics. The cost of implementing new technologies is a major hurdle for shipowners. A recent study by the Global Centre for Maritime Decarbonisation found that installing an OCCS system could cost between $269 and $405 per tonne of CO2 avoided. However, this could still be cheaper than the rising cost of carbon taxes or the price of premium eco-friendly fuels.

Seabound indicates its units will be valued in the tens of thousands of pounds sterling, positioning them as a cost-effective option. The financial case is strengthened by new emission levies, which will make polluting more expensive. By enabling compliance and reducing these new costs, technologies like Seabound's can offer a clear return on investment.

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A Recent Collaboration

In a significant step forward, Seabound recently partnered with STAX Engineering, a US-based company specialising in maritime emissions control. In a joint demonstration at the Port of Long Beach, they showcased a fully integrated system. STAX's technology first filters out harmful pollutants like nitrogen oxides, before passing the purified exhaust to Seabound's unit, which then captures the CO2.

This collaboration demonstrates how different technologies can be combined for a more comprehensive solution to port and ship emissions. The successful trial has paved the way for further deployments, including with Associated British Ports in Southampton, bringing the technology closer to widespread commercial use.

Scaling the Solution

Like many new businesses, Seabound must confront the difficulties of scaling its operations to meet the needs of a global industry. Manufacturing hundreds or thousands of units and establishing the logistical network to swap out the limestone containers in every key global port is a formidable task.

However, the company has already secured its first commercial commitment to fit full-scale containers onto ships this year. She has a definite view of what comes next: her company’s technology on hundreds, and eventually thousands, of vessels, with operational centres established in all key global ports. This ambition reflects the scale of the problem and the urgent need for workable solutions.

The Voyage Ahead

The decarbonisation of the world's shipping fleet is among the most considerable environmental tests of our time. There is no single, easy answer. The solution will likely involve a combination of approaches: operational efficiencies, transitional technologies like carbon capture, the eventual adoption of cleaner fuels, and the innovative use of wind power.

In this complex transition, the modest-looking steel box being perfected in a London suburb could play a crucial role. By offering a practical, affordable, and immediate way to cut emissions from the existing fleet, Seabound's invention may assist the maritime sector to finally alter its course and navigate towards a cleaner, more sustainable future.