Shipping wants to become climate neutral – and is looking for solutions. The first ships are being retrofitted with systems for CO₂ storage. Corporations are testing other types of drive. Is that enough?
Samskip Kvitbjörn: Gas powered and soon equipped with special technology. Photo: picture alliance / Hinrich Bäsemann
CO₂ capture filters carbon dioxide from ship exhaust and is installed on the ships Clipper Eris and Samskip Kvitbjorn to reduce emissions.
The International Maritime Organization (IMO) wants to reduce emissions by 20 to 30 percent by 2030 and allow ships to sail as CO₂-free as possible from 2050.
Methanol from renewable sources is considered a climate-neutral second fuel, but its supply is decreasing worldwide, which is why shipping companies sometimes have to resort to fossil methanol.
Ammonia is being tested as an alternative fuel for shipping.
Düsseldorf, Berlin. At first glance, the “Clipper Eris” from the Norwegian shipping company Solvang has few special features. But the liquid gas tanker, currently underway off the Chinese coast, represents a pioneering achievement.
The Seatrium shipyard in Singapore equipped the ship, which was completed in 2019, with a CO₂ capture system in 2024/25. It filters out the climate-damaging carbon dioxide from the exhaust gases so that it does not enter the atmosphere.
The “Samskip Kvitbjorn”, which regularly sails along the Norwegian coast on the route from Rotterdam to Hammerfest, is also being retrofitted with a CO₂ capture system. The conversion of the ship, which unlike the “Clipper Eris” will not run on heavy oil but rather on liquefied natural gas (LNG for short), is scheduled to be completed in 2027.
This is intended to help reduce CO₂ emissions from shipping. The sector is under great pressure to act. Heavy oil and marine diesel dominate shipping worldwide by a wide margin.
They are available globally and cheap. But they are harmful to the climate. When they are burned in a ship's engine, large amounts of CO₂ are released. Almost three percent of CO₂ is emitted into the world's oceans.
The International Maritime Organization (IMO), which is supported by 176 member states, has therefore committed to reducing emissions by 20 to 30 percent by 2030. From 2050 onwards, ships should be as completely CO₂-free as possible.
Although the time is still decades away, it is anything but a future issue for the industry, as tankers and container ships are usually in use for 25 to 30 years.
That's why operators are already faced with the question of which drive technology they should use for new orders. Do the “Samskip Kvitbjorn” or the “Clipper Eris” show the solution – or does the answer lie in other types of propulsion?
Proven technology, new field of application
CO₂ capture is a tried and tested technology. The cement and lime industry as well as waste management have no alternative to capturing and permanently storing CO₂. The CO₂ emissions from these industries are considered unavoidable.
Things are different in shipping. There are alternative fuels and drive concepts that can make shipping climate-friendly even without CO₂ capture. However, CO₂ capture on board has an advantage: it can be subsequently docked to an existing drive, as the examples “Samskip Kvitbjorn” and “Clipper Eris” demonstrate.
According to Pauline Leroi from the think tank Future Cleantech Architects (FCA), CO₂ capture on ships should therefore be viewed as a bridging technology. It can be particularly interesting for existing fleets that will be in use for a decade or longer.
“It’s important to realize that CO₂ capture on board ships is not the ‘silver bullet’.” What is meant is a simple and immediate solution to a complex problem. “But it is one of many solutions to make progress in reducing CO₂,” says Leroi.
CO₂ capture is not climate-neutral anyway. In the case of the “Clipper Eris”, for example, the project partners claim that they can remove up to 70 percent of greenhouse gases from the exhaust. In addition to the shipping companies Solvang Wärtsilä, Everllence (formerly MAN Energy Solutions), the research institute SINTEF and the shipyard Seatrium are involved.
On the “Samskip Kvitbjorn” and the “Clipper Eris”, the entire process chain of CO₂ capture and storage (CCS for short) is depicted on a small scale - with the restriction that CO₂ storage on the ship is only temporary. It is only pumped out and processed in the port. CO₂ can be stored or processed directly in onshore facilities; the infrastructure is closed.
Limestone production on board
Leroi points to an alternative solution developed by the British company Seabound. It is implemented on the “UBC Cork”, which is used by the German cement manufacturer Heidelberg Materials.
Seabound's CO₂ capture system captures the ship's engine exhaust on board and directs it into a pressure chamber filled with calcium hydroxide pebbles. The CO₂ contained in the exhaust gas reacts with the stones and converts into calcium carbonate.
Calcium carbonate, also known as limestone, is the central raw material in cement production. This limestone is stored on board and unloaded in Norway, where it is delivered to Heidelberg Materials' cement plant in Brevik. There it is used to produce environmentally friendly concrete on an industrial scale.
Seabound says its system can capture up to 95 percent of CO₂ emissions from ship exhaust. This solution can also be installed later. The advantage, compared to solutions on the “Samskip Kvitbjorn” and the “Clipper Eris”: The limestone is an easy to store solid. The complex intermediate storage of CO₂ on board is no longer necessary.
Seafaring relies on different drives
In addition to CO₂ capture, other experiments with alternative types of drive have long been underway. Many new ships use so-called dual-fuel engines, which can be fired with alternative fuels in addition to ship diesel if necessary.
Most shipping companies rely on methanol as a secondary fuel, especially the Danish major Maersk and its German alliance partner Hapag-Lloyd.
Because methanol remains liquid at normal pressure and room temperature, refueling is similar to ship diesel. The alternative fuel can already be refueled at more than 125 ports worldwide, according to the provider Methanex.
But methanol is only CO₂-neutral when it is produced synthetically using wind power or solar systems. However, there are bottlenecks on the world market. The supply is even decreasing.
Last year, Maersk was only able to fuel its freighters with half as much green methanol as the previous year. Due to the shortage, the company had to increasingly resort to gray methanol, it said in the annual report, i.e. methanol that was obtained from fossil energy sources such as natural gas or coal.
Another alternative is so-called biodiesel. Because it is made from crops or organic waste, it is considered climate neutral. In addition, ship engines can use it as fuel without major adjustments, as has already been shown in practice.
However, in order to make biodiesel widely usable in global shipping, huge areas of grain cultivation would be necessary. Experts say this would worsen the nutritional situation in many countries. The potential for producing biodiesel made from organic waste is again limited.
Ammonia is corrosive
Part of the shipping industry therefore relies on ammonia. The chemical mixture in which the energy source hydrogen is bound is considered to be available in large quantities. Ammonia has been used worldwide in the production of fertilizers for decades. The biggest disadvantage: The colorless gas with an extremely pungent, unpleasant smell burns the eyes, nose and throat even in small quantities.
There are still attempts to operate ships. In June of this year, the Belgian shipping company Exmar put the “Antwerp”, the world's first ocean-going ship powered by ammonia, into service. The engine of the tanker, which comes from the Korean shipyard HD Hyundai Heavy Industries, was developed by the plant manufacturer WinGD from Winterthur, Switzerland. Another 40 orders have already been received, it said.
But in addition to the question of which alternative fuels will prevail, another one has been causing uncertainty for some time: US President Donald Trump's policies are calling the IMO's specifications into question. It had originally announced a legally binding framework to reduce greenhouse gas emissions from ships with a payload of more than 5,000 tons to zero by 2050.
Trump has vetoed it: The United States will not accept global taxes on shipping that are fraudulent, he wrote on Platform The formal adoption of the IMO catalog of measures has since been stopped.
