Onboard carbon capture is the most pragmatic idea in shipping decarbonisation: rather than wait for green fuels to become available and affordable, capture the CO2 from a conventional ship's exhaust before it reaches the atmosphere, liquefy it, store it on board, and offload it in port for permanent storage or use. It lets a vessel keep its existing engine and well-established fuel while still cutting reported emissions — a transitional bridge across the years before alternative fuels scale. In 2026 the concept has crossed from laboratory to sea: the world's first full-scale onboard capture retrofit, a 7 MW Wärtsilä system on Solvang's tanker Clipper Eris designed to capture around 70% of main-engine CO2, has entered pilot operation, and other projects on gas carriers, bulkers, and liner vessels are reporting stable capture rates of roughly 50 to 70%. It is not free — capture costs energy, weight, and space, and creates a CO2 logistics chain to and from the ship — and its economics rest largely on avoiding carbon costs under the EU ETS. For R&D and innovation officers weighing it against fuel-switching, the questions are concrete: how the technology works, what it captures, where the CO2 goes, what it costs in efficiency, and which vessels suit it. This overview answers each. To track emissions, fuel, and captured-CO2 data across a decarbonising fleet, book a Marine Inspection demo.
Green shipping · onboard carbon capture
Carbon Capture on Ships: Maritime CCS Technology
An overview of shipboard carbon capture and storage — how post-combustion capture works, the capture and storage technologies, onboard storage and shore offloading, the energy trade-offs, and the economics driving adoption.
1Pre-condition
2Absorb
3Strip
4Liquefy
5Store
Why Onboard Carbon Capture
The appeal of capturing carbon on board is that it works with the fleet that exists today, sidestepping the cost and availability problems of green fuels. It is positioned as a transitional decarbonisation measure rather than a permanent answer. See emissions tracking in a demo.
Keep existing engines
Capture lets a vessel continue using its well-established engine and conventional fuel while still cutting the CO2 it reports — no fuel switch required.
Avoid the fuel race
Green ammonia, hydrogen, and methanol face fierce, expensive competition for supply; capture is an alternative that does not depend on securing them.
A retrofit option
Systems can be retrofitted to existing ships or specified on newbuilds, offering a path to lower emissions on tonnage already in service.
A revenue angle
Captured CO2 can be offloaded for permanent storage, generating carbon credits, or for utilisation — turning an emission into a potential revenue stream.
How Onboard Capture Works
Most maritime systems use post-combustion capture, treating the engine's exhaust after it is produced. The process runs as a chain of stages that separate CO2 from the exhaust and ready it for storage. See the process in a demo.
1
Pre-conditioning
The exhaust gas is cooled and cleaned to prepare it for the capture stage, removing contaminants and bringing it to the right condition for absorption.
2
Absorption
The conditioned exhaust passes through an absorber column where a chemical solvent — typically an amine — binds the CO2, separating it from the rest of the gas.
3
Desorption (stripping)
The CO2-rich solvent is heated to release the captured CO2 as a concentrated stream, regenerating the solvent so it can be reused in the absorber.
4
Liquefaction
The released CO2 is compressed and cooled into liquid form, dramatically reducing its volume so it can be stored practically on board.
5
Storage
The liquid CO2 is held in dedicated onboard tanks until the vessel reaches a port where it can be offloaded into the shore-side CO2 value chain.
Physically, this adds a block of equipment near the funnel — ducting, an absorber column, pumps, a liquefaction unit, and one or more CO2 tanks, with control screens in the engine control room. The leading systems target capturing around 70% of a vessel's main-engine CO2, building on decades of exhaust-treatment integration experience and adapting amine technology long used on land.
The Capture Technologies
While post-combustion amine capture dominates maritime applications, several capture approaches exist, each with different maturity and fit. Understanding the landscape clarifies why one has led. See technology tracking in a demo.
Post-combustion (amine)
Extracts CO2 from exhaust after combustion using chemical solvents like amines. The most practical for ships, as it adapts to existing engine configurations and is furthest along in development.
Pre-combustion
Converts the fuel into hydrogen and CO2 before combustion, separating the carbon upstream. Less common at sea due to its complexity and the need for dedicated machinery.
Cryogenic separation
Separates CO2 by cooling, and can exploit the cold energy of LNG fuel on gas-fuelled ships for efficiency — a promising route for specific vessel types.
Membrane & oxy-fuel
Membrane separation and oxy-fuel combustion, which burns fuel in pure oxygen for a CO2-rich exhaust, are alternative approaches at earlier stages for shipboard use.
Measure what you capture
Track Captured CO2, Fuel, and Emissions Together
An onboard capture system only pays back if the captured CO2, the fuel burned, and the net emissions are measured and reported credibly. Marine Inspection logs fuel consumption and emissions per voyage, helps document captured-CO2 volumes and offloading, and feeds EU ETS and CII reporting — turning capture into verifiable compliance value. Book a 30-minute demo to see emissions tracking, or start a free trial today.
Onboard Storage and Shore Offloading
Capturing CO2 is only half the system; the other half is holding it and getting it ashore. This logistics chain is what distinguishes maritime capture from a land plant, and it shapes which ships and routes suit the technology.
Liquid CO2 storage
Captured CO2 is liquefied and held in dedicated pressurised tanks on board, the most compact practical form for storing it between port calls.
Tanks compete with cargo
CO2 storage tanks and capture skids take space that may compete with cargo capacity, and their location and foundations can affect vessel stability.
Port offloading
At port the liquid CO2 is offloaded into shore infrastructure for permanent geological storage or industrial use, completing the value chain.
Regular port calls help
Ships on fixed trading routes with regular calls suit capture best, giving consistent, predictable opportunities to offload the stored CO2.
The need to offload makes the shore-side CO2 value chain a real dependency. A capture-equipped ship is only as effective as its ability to discharge what it captures, so the build-out of port reception and CO2 transport-and-storage infrastructure — part of a global CCS sector now spanning hundreds of projects — is as important to maritime capture as the onboard equipment itself.
The Trade-Offs: Energy, Space, and Maintenance
Onboard capture buys lower reported emissions in exchange for real costs, and an honest assessment weighs them carefully. These are the practical issues the early pilots are surfacing. See operational tracking in a demo.
Energy penalty
The capture process, especially solvent regeneration and liquefaction, demands extra power, raising the vessel's energy use and partly offsetting the gain.
Weight and space
The added equipment and CO2 tanks impose weight and footprint penalties, competing with cargo and constraining where the system can be fitted.
Solvent degradation
Trials have highlighted amine solvent degradation over time, a maintenance and consumable cost that designs are being refined to reduce.
New maintenance tasks
The system adds an exhaust-treatment plant to maintain, including integration with any existing scrubber, and new operational routines for the crew.
CO2 logistics chain
Managing the captured CO2 to and from the ship is an entirely new logistics task that conventional fuel operation never required.
Partial capture
Real-world capture rates of around 50 to 70% of treated exhaust mean it reduces, rather than eliminates, a vessel's CO2 emissions.
Which Vessels Suit Capture
Onboard capture is not equally viable across the fleet. Its space, power, and route demands point clearly toward certain vessel types where the business case is strongest.
Large & medium vessels
Tankers, bulk carriers, and container ships suit capture, given their high exhaust volumes and the space available to integrate the system.
Tankers & LNG carriers
Tend to have more usable deck space for capture skids and CO2 tanks, and LNG carriers can exploit cold energy for cryogenic capture.
Large containerships
Can use their variable loading factor and large electrical propulsion capacity to optimise the system's CO2-reduction performance.
Fixed-route operators
Ships with regular, predictable port calls offer the consistent offloading opportunities that capture depends on; most pilots run on liner vessels.
Economics, Regulation, and Readiness
The business case for capture is, today, largely a regulatory one — it is driven by the cost of carbon a ship would otherwise pay. That makes the policy framework central to its future.
EU ETS drives it
The EU ETS is currently the main regulation that rewards capturing carbon, so avoiding its rising carbon cost is the core of the OCC business case.
Rising carbon price
Carbon prices in the range of roughly €65 to €75 per tonne in 2025 are projected to climb substantially through 2030 and beyond, strengthening the case over time.
Framework still forming
The IMO began developing a relevant framework, but FuelEU offers no capture credit yet and dedicated IMO safety guidelines for onboard capture are still to be set.
First systems at sea
Full-scale systems are now operating in pilots on real vessels, with vendors refining designs to cut energy use and footprint as experience accumulates.
The readiness verdict for 2026 is that onboard carbon capture has moved from concept to credible pilot, but its economics and rulebook are still maturing. The technology works at scale, the first full-scale retrofits are at sea, and a rising carbon price improves the case each year — yet the energy penalty, the space and cost burden, the immature CO2 offloading chain, and the lack of capture credit outside the EU ETS keep it a selective, route-and-vessel-specific option rather than a universal one. For an innovation officer, capture is best read as one tool in a decarbonisation portfolio: compelling for the right large vessel on the right fixed trade, complementary to fuel-switching rather than a replacement for it. Whichever path a fleet takes, the constant requirement is credible measurement of fuel, emissions, and — where capture is fitted — captured CO2. Book a demo to see emissions and compliance tracking.
Frequently Asked Questions
What is onboard carbon capture on ships?
Onboard carbon capture (OCC) is the capture of CO2 from a ship's engine exhaust after combustion, before it reaches the atmosphere. The CO2 is separated, liquefied, and stored in onboard tanks for offloading at port into permanent storage or use. It lets a vessel keep its existing engine and conventional fuel while cutting reported emissions, as a transitional decarbonisation measure.
How does shipboard carbon capture work?
Most systems use post-combustion capture in five stages: pre-conditioning cools and cleans the exhaust; an absorber column uses a chemical solvent, typically an amine, to bind the CO2; the solvent is heated to release a concentrated CO2 stream; the CO2 is liquefied by compression and cooling; and it is stored in dedicated onboard tanks until offloaded ashore.
How much CO2 can onboard capture remove?
Leading systems target capturing around 70% of a vessel's main-engine CO2, and early full-scale projects on gas carriers, bulkers, and liner vessels report stable capture rates of roughly 50 to 70% of the treated exhaust stream, depending on engine load and configuration. It reduces, rather than eliminates, a ship's CO2 emissions.
What are the main drawbacks of onboard capture?
The process demands extra power (an energy penalty, especially for solvent regeneration and liquefaction), adds weight and takes space that competes with cargo, brings amine solvent degradation and new maintenance, and requires a CO2 logistics chain to offload captured carbon. Real-world capture is partial, so it cuts rather than eliminates emissions.
Which ships are best suited to carbon capture?
Large and medium vessels with high exhaust volumes and available space — tankers, bulk carriers, LNG carriers, and large container ships — suit capture best. Tankers and LNG carriers tend to have usable deck space, and ships on fixed routes with regular port calls offer the consistent CO2-offloading opportunities the technology depends on.
Is onboard carbon capture economically viable?
Its business case is largely driven by avoiding carbon costs under the EU ETS, currently the main regulation rewarding capture. With carbon prices around €65 to €75 per tonne in 2025 and projected to rise, the case strengthens over time, and captured CO2 can generate credits or revenue. But the energy, space, and logistics costs keep it a selective, vessel-specific option for now.
Built for decarbonisation tracking
Whatever the Path, Prove the Carbon
Whether you capture carbon, switch fuels, or both, track fuel consumption and emissions per voyage, document captured-CO2 volumes and offloading, and feed EU ETS and CII reporting — so every tonne avoided is measured and verifiable. Marine Inspection turns decarbonisation into documented compliance value. Book a tailored walkthrough or start a free trial today.
