By Sigurd Jenssen

Shipping is at a crossroads. It moves more than 80 percent of global trade, yet it produces around 2 percent of global greenhouse gas emissions. Without intervention, those emissions could rise by as much as 45 percent by 2050, even as other sectors decarbonize. The International Maritime Organization (IMO) has set clear milestones: a 20 to 30 percent reduction in emissions by 2030; 70 percent by 2040; and net-zero by 2050. The EU has added its own measures, including the Emissions Trading System (ETS) and FuelEU Maritime, that place a direct price on carbon.

For shipowners, carbon-neutral fuels, such as green methanol or ammonia, remain expensive and scarce, with supplies unlikely to meet full industry demand for at least a decade. Against this backdrop, Wärtsilä’s onboard carbon capture and storage (CCS) technology offers a proven pathway to slash emissions today. Installed aboard Solvang ASA’s 21,000-cubic-m ethylene carrier Clipper Eris, this is the world’s first full-scale CCS deployment on a seagoing vessel, designed to capture more than 70 percent of carbon dioxide from all onboard combustion sources.

How the System Works at Sea

Wärtsilä’s system comprises several stages or modules: exhaust gas pre-treatment, chemical absorption, desorption, liquefaction and storage. These stages can be tailored for different fuel types and capture rates. Exhaust gases from the main and auxiliary engines, as well as the boilers, are cooled and scrubbed to remove SOx, NOx, and particulates, achieving reductions of over 97, 80, and 90 percent, respectively. The cleaned stream enters an absorber tower, where an amine-based solvent captures the carbon dioxide. This blend was selected for its stability across fuel types, low degradation rate, affordability and global availability.

Once saturated, the solvent passes to a desorber, where captured CO₂ is stripped using heat recovered from the ship’s systems to reduce additional fuel burn. The stripped CO₂ is compressed, liquefied, and transferred to onboard tanks; in Clipper Eris’s case, two 360-cubic-m units mounted on deck to avoid cargo disruption. This configuration supports roughly 14 to 20 days of operation before offloading. The system handles up to 50 tonnes per day on Clipper Eris, with Wärtsilä’s Moss, Norway, test center confirming 10 tonnes per day under controlled conditions.

The installation connects to every combustion source on board, the 7,100-kW main engine, auxiliaries, and boilers, without requiring modifications to the prime mover. Operational results have shown consistent capture rates above 70 percent during typical voyages and peaks exceeding 90 percent during low engine loads. Energy integration has been a critical part of the design. Total electrical demand equates to roughly 8 to 10 percent of propulsion power: 3 to 5 percent for the carbon capture processes and 6 to 8 percent for CO₂ liquefaction. Thermal demand sits at around 35 percent of the capture cycle’s energy needs, largely offset through heat recovery systems. Engineers continue to refine solvent formulations and heat integration to lower this figure, with ongoing testing at Moss aimed at extending solvent life and further reducing parasitic loads.

Wärtsilä’s Moss, Norway, testing facility has validated the system under more than 5,000 operational hours, trialing multiple fuel types, including heavy fuel oil and marine gas oil, as well as simulations of exhaust from LNG and methanol, to confirm solvent stability and capture efficiency across a range of load conditions. Testing also validated tank insulation standards designed to prevent boil off during extended voyages, which is critical for operators trading globally who may not discharge CO₂ for several weeks. Solvent degradation rates have been kept under control by reclaim systems that filter contaminants and recycle usable solution, extending operational life and lowering consumable costs over time.

 

 

Engineering and Design Challenges

Unlike industrial carbon capture systems, which benefit from stable flows and unlimited space, maritime CCS must operate within compact footprints and variable conditions. The absorber towers on Clipper Eris use a counter-current packed column design, where upward flowing exhaust gas meets downward flowing solvent over structured packing that maximizes contact area. This configuration ensures high capture efficiency even as exhaust characteristics change between heavy fuel oil, LNG, and methanol operations. The tower’s internals are fabricated from corrosion-resistant alloys.

Liquefaction follows a staged compression process, stepping CO₂ up to storage pressure before cooling to roughly -26° C. Each stage recovers heat for reuse elsewhere in the system, cutting electrical demand. Automated controls balance compressor loading and heat integration dynamically, so energy use remains proportional to capture volume. Crew monitoring is simplified by integrated dashboards showing solvent levels, capture rates, and tank fill status, enabling operators to maintain performance through routine checks rather than constant oversight. Filtration and reclaiming systems extend solvent life, reducing the frequency of top ups and waste generation.

Wärtsilä’s system is built to cope with the realities of life at sea. Skid-mounted absorber and desorber units are reinforced to handle constant vibration and ship motion, while flexible piping and shock absorbing supports limit stress on key components during heavy seas. Fluctuating CO₂ concentrations in exhaust streams, caused by changing engine loads, are addressed through adaptive automation that adjusts solvent flow rates and desorption energy input in real time, keeping capture steady. Crew involvement is kept to a minimum by intuitive interface that consolidate key data, enabling quick decisions without specialist training. These design choices make continuous CCS operation feasible even for vessels with small crews and long voyages. Wärtsilä’s approach also allows systems to be broken into smaller skid-mounted subunits for ships with restricted deck space or power budgets, making phased retrofits viable on more constrained vessels. Tank insulation and cryogenic management were optimized through multi-layer insulation and active boil off control, preventing evaporative losses even in warm climates. Heat recovery from economizers and jacket water circuits reduces auxiliary boiler load and helps offset the roughly 35 percent thermal energy requirement for desorption. These design refinements mean CCS can be integrated without disrupting propulsion efficiency or voyage economics.

Scaling CCS Across Fleets

Early adopters, across emissions reduction technologies, are targeting their most carbon-intensive ships first, typically large tankers, bulk carriers, and gas carriers, to achieve the greatest reductions in both emissions and carbon cost exposure. These vessel types offer more deck space and higher power availability, making the integration of absorber towers, cryogenic tanks, and liquefaction systems for CCS simpler and less intrusive on cargo operations. The sectional nature of Wärtsilä’s system allows subsequent installations to benefit from shorter lead times and economies of scale, as major components can be prefabricated and tested ashore before delivery.

Fleet strategies are evolving toward averaging, where operators balance CCS-equipped vessels with non-equipped ships to achieve portfolio-wide emissions targets. Rather than retrofitting every ship, some owners are prioritizing 10 to 20 percent of their fleets for CCS, typically those with the longest trading ranges or the highest fuel consumption, and using the emissions reductions from those vessels to bring down their entire fleet’s carbon intensity. Wärtsilä’s modeling indicates that for many owners, fitting CCS to just a small share of their fleets can offset enough EU ETS liability to keep overall operating costs steady through the 2030s. This approach is especially viable for operators with mixed fleets, as the CCS-equipped vessels can shoulder more of the compliance burden while the remainder of the fleet transitions to low-carbon fuels at a pace that suits operational and market realities.

Modular construction and Wärtsilä’s global support network also help minimize disruption and off-hire. Most retrofits would not require extended drydocking but could be done alongside. Because the systems are built in skid-mounted sections, with pre-planning, owners can add or expand capture capability as regulations tighten, making it easier to manage capital expenditure and adapt to evolving carbon pricing regimes. Wärtsilä’s Sustainable Fuels analysis projects that, as methanol and ammonia take time to scale, deploying CCS fleet wide could cut over 70 percent of carbon output across a mixed fleet when combined with fuel efficiency upgrades and pooling strategies. For many owners, this means CCS will act as the backbone of compliance in the 2030s, with low-carbon fuels gradually assuming a larger share of the mix by 2040. Comparative modeling also shows that over a 10-year horizon, CCS retrofits can deliver lower-cost-per-tonne compliance rather than relying solely on low-carbon fuels, particularly given the high production costs and limited availability of methanol and ammonia in the current decade.

 

 

A Bridge to Future Fuels

Carbon capture is not a competitor to low- and zero-carbon fuels; it is a bridge that enables their broader use while extending the life of conventional options. Projections from Wärtsilä’s 2024 transition modeling show that even with rapid growth in green methanol, ammonia, and hydrogen-based fuels, sustainable options may only cover one-third of shipping’s energy demand by 2035. This gap would leave many operators exposed to compliance penalties and high carbon costs if bridging technologies were not deployed in parallel.

By incorporating CCS, shipowners can continue to operate vessels using heavy fuel oil, LNG, or methanol while meeting tightening emissions limits and avoiding escalating costs under frameworks such as the EU ETS. These systems do not lock operators into any one fuel pathway, as the capture process is fuel agnostic, working effectively across conventional and low-carbon fuels alike. This flexibility helps owners protect the value of existing assets while positioning them to integrate alternative fuels when prices and supply chains mature.

As production of e-methanol and synthetic diesel scales up, in the future, captured CO₂ could be supplied back to fuel producers as feedstock, closing the carbon loop and enabling owners to participate directly in the circular economy. This approach extends the utility of CCS hardware beyond the fossil fuel era, letting shipowners spread the capital investment across multiple fuel transitions. For many operators, this dual role—providing compliance today and supporting the emergence of synthetic fuels tomorrow—makes CCS a cost-effective and strategic choice. Wärtsilä’s projections indicate that although green methanol could begin closing the price gap with fossil fuels in the late 2030s, and ammonia may become competitive in the 2040s, CCS enables fleets to bridge that gap without incurring untenable penalties or scrapping viable ships prematurely.

Wärtsilä’s involvement in the Clipper Eris project demonstrates that full-scale carbon capture at sea is no longer an experiment or a proof of concept; it is a functioning, commercially deployed system capable of capturing the majority of onboard CO₂ emissions. With capture rates consistently above 70 percent, integration alongside existing exhaust treatment, and a design tailored to the space, power, and operational constraints of oceangoing ships, the technology provides owners with a tangible solution to today’s regulatory and economic pressures.

Its significance lies in its ability to help shipowners avoid being cornered by unpredictable developments in the decarbonization landscape. Alternative fuels, while important, remain scarce and expensive, with infrastructure years away from matching global demand. Regulatory frameworks, from the EU ETS to the International Maritime Organization’s Carbon Intensity Indicator and potential market-based measures, will continue to evolve, and carbon prices are expected to rise sharply through the 2030s. By adopting CCS now, owners can keep fleets compliant while continuing to run proven fuels, avoiding costly scrapping or premature investment in unproven alternatives.

CCS also helps safeguard the value of vessels by enabling them to remain in service longer, even as fuel supply and regulatory conditions shift. This future-proofing is amplified by the system’s modularity and fuel-agnostic design, which keeps capture units relevant as fleets transition from fossil fuels to methanol, biofuels, or e-fuels. By supplying captured CO₂ as feedstock for synthetic fuel production, operators can also integrate into the future fuel economy, creating an additional revenue stream and further offsetting the cost of adoption. For Wärtsilä, this technology represents more than a hardware offering. It positions the company as a partner to shipowners navigating the complex transition, providing not only systems but also life cycle support, operational data, and decarbonization modeling. As more vessels come online with CCS, costs will fall and performance will improve, benefiting the wider industry.

For shipowners, early adoption can deliver direct cost savings through avoided carbon penalties, competitive advantage in emissions-conscious charter markets, and resilience against future regulatory shifts. As part of a layered decarbonization strategy that includes alternative fuels, energy efficiency upgrades, and evolving operational practices, Wärtsilä’s onboard carbon capture stands as one of the few technologies capable of delivering immediate, material reductions in greenhouse gas emissions while keeping fleets commercially viable. It is not the end state for shipping, but it is a critical bridge to get there; a tool that enables the industry to move forward decisively while the long-term fuel transition takes shape.

 

Sigurd Jenssen is the director of exhaust treatment at Wärtsilä Marine.