Alisha Fredriksson says she had one motivation for starting her latest business venture: “to tackle the climate crisis and to have as big of an impact as possible.”
Fredriksson is CEO of UK climate tech startup Seabound, which is developing an onboard carbon capture device for cargo ships.
Global shipping, which accounts for about 3% of global greenhouse gas emissions, aims to reach net zero by or around 2050, like many other industries. However, it’s still looking for solutions that will help companies achieve that target. “I think I’m maybe an impatient person, but for me, shipping is not moving fast enough to decarbonize,” says Fredriksson.
Seabound’s technology, which can be housed in one or more standard shipping containers, takes the exhaust fumes from the engines and runs the CO2 contained in them through an accelerated version of a natural process that’s been happening in the oceans for billions of years.
The container is filled with pebbles made of calcium oxide, known as lime, which absorb the CO2. “You can basically picture a box of rocks,” Fredriksson says, “the exhaust gasses pass through there and the CO2 is soaked up and turned into limestone, while the rest is released.”
It’s a fairly simple process, she adds, because the CO2 is simply trapped. “That’s everything we do on board — we don’t separate the CO2, we don’t purify it or compress it, because those steps are really energy intensive and quite complicated to do on board. So we’ve shifted the complicated stuff to happen on shore instead.”
Once the ships docks at a port, the pebbles can be offloaded for further treatment at a specialized plant, including separating the CO2 to use them again, or recycling them as construction material.
Seabound has run tests that it says confirmed the viability of the process, by capturing 80% of the carbon and 90% of the sulfur, a pollutant that is already captured aboard about 5% of the global merchant fleet using similar systems. Fredriksson says the company is in talks with several shipping companies and is gearing up to launch commercially before the end of 2025.
A simple retrofit
Fredriksson, with co-founder Roujia Wen, started Seabound in 2021, aged 26 but already boasting a resume that included launching a climate program at a global non-profit and building a maritime green fuel startup called Liquid Wind. In 2023, she made Forbes’ 30 Under 30 Europe Social Impact list and the MIT’s Tech Review Innovators Under 35 list.
“It’s still fairly uncertain what the future of decarbonized shipping will look like,” she says. “There’s alternative fuels, the main contenders being green methanol and green ammonia, but there isn’t a fuel supply (for them) yet, and those fuels aren’t compatible with the existing fleet. So we have about 100,000 ships on the water today that will keep releasing CO2 for the foreseeable future.”
One of the advantages of the Seabound system, Fredriksson adds, is that it generates heat and therefore doesn’t require additional energy or burn any fuel. The space occupied onboard – which determines how much money the ship will lose in reduced cargo capacity — depends on the size of the vessel and the amount of CO2 to capture. “Picture a 20-foot shipping container,” she says. “You could have as many as you want, depending on how much you want to capture. We work with our customers to figure out what is the target percent of CO2 to capture, but in general, we’re looking to cap (the space we use) at ideally less than 1% of cargo capacity.”
The installation is relatively simple as it only requires piping to connect the Seabound container to the engine exhaust system. Once the ship has completed its journey, the pebbles — which become slightly heavier but not larger — are offloaded by swapping the Seabound containers with new ones.
Once at port, the pebbles can go through the opposite reaction that occurred onboard, by heating them up in a kiln to separate the CO2 and make them ready to absorb it again; the resulting pure CO2 can be made into products like fuels or chemicals, or be sequestered underground. This closed loop model would make the pebbles reusable, but requires specific infrastructure to be built at ports or nearby, to complete the process.
Another option is to use the pebbles as building material, as they are made of limestone, a common ingredient in concrete. This would require less infrastructure at ports, but there are still uncertainties about the applications for the limestone, because it’s been exposed to impurities from the ship’s exhaust. “It wouldn’t be suitable for super high-grade applications like water purification, for example, because there might be contaminants,” says Fredriksson. You could think of it as an aggregate, for instance, in concrete or road construction, where there’s less sensitivity to impurities.”
Seabound completed a pilot run last year with global shipping company Lomar, putting one of its devices aboard a medium-sized, 3,200-container vessel, where it achieved the 80% carbon capture. “While this was a prototype device, it was a critical technical proof and a milestone for us. And since then, we’ve essentially been building up our commercial products. Long term, we want to be able to capture carbon on any type of ship all over the world.”
A short-term solution?
There is growing interest in onboard carbon capture systems (OCCS) like Seabound’s, but their implementation is not straightforward.
A project carried out by the Oil and Gas Climate Initiative (OGCI), an association of large oil and gas companies looking for climate change solutions, and the Global Centre for Maritime Decarbonisation (GCMD), a Singapore-based climate nonprofit, tested a different system that produced liquefied CO2, made using non-proprietary equipment and processes — so results could be shared publicly — on a medium-range oil tanker. Results suggest a potential reduction in CO2 emissions by up to 20% per year, with a fuel consumption penalty of just under 10%.
However, it also found that the cost of building and installing such a system on the ship was an estimated $13.6 million. “The adoption of OCCS faces significant challenges, particularly its high capital cost for retrofit and operational cost associated with additional fuel consumption,” says Lynn Loo, a professor of chemical and biological engineering at Princeton University and CEO of the GCMD. While at scale costs could go down by as much as 75%, she adds, the test revealed other critical bottlenecks, such as the lack of port infrastructure for liquefied CO2 offloading and the absence of a global regulatory framework for managing CO2 that is captured in international waters.
According to Fredriksson, that project used a “more conventional” form of carbon capture compared to Seabound’s second-generation one, which leaves most of the complex tasks and machinery off the ship to reduce costs and increase scalability.
Similar technologies that don’t involve unloading anything at ports are also in development, such as one being tested by Calcarea, an offshoot of The California Institute of Technology, which is designed to discharge the CO2 directly into the sea as carbonate-rich water.
“We know and like the team there, and I’m actually really curious about the potential combination of our solutions,” says Fredriksson, “because we make limestone, and they start with limestone. If we could integrate our technologies, we could potentially capture double the amount of CO2 onboard using the same amount of lime as in Seabound’s current system.”
According to Tristan Smith, a professor of Energy and Transport at the University College London, OCCS could take on “a transient role” before hydrogen-derived fuels become more competitive by the mid-2030s. “There is not a positive outlook for (OCCS) use in shipping,” he says. “This does not mean it isn’t popular — it is attractive to imagine a technology that could allow continued use of fossil fuel. But a positive view is linked to a simplification of the realities of the business case fundamentals, which are less compelling than solutions that are coupled to renewable energy (green ammonia).”
Faisal Khan, a professor of chemical engineering and petroleum engineering at Texas A&M University and the director of the Ocean Engineering Safety Institute believes that forms of carbon capture aboard ships will become “almost mandatory in the coming years, similarly to what happened in the automobile industry with catalytic converters.”
He sees potential in Seabound’s technology due to the benefits of mimicking a natural process. “The bottleneck remains the efficiency of these processes, because the exhaust (gas) is unfortunately not pure carbon dioxide, it comes with a lot more impurities. And these impurities affect efficiency,” he says.
However, he is optimistic about the commercial prospects of OCCS. “Whether it will last or stand the scrutiny of time until we have better options is unsure,” he says, “but in the short to medium term, these are promising technologies.”
