Carbon Capture and Storage
Capture methods, how CO₂ stays underground, operating projects and the tank arithmetic of onboard capture.
Carbon capture and storage (CCS) separates carbon dioxide from a large source before it reaches the atmosphere, compresses and transports it, and injects it into deep geological formations for permanent storage. The Global CCS Institute's 2025 report counts 77 operating facilities with about 64 million tonnes of annual capacity.[1] That is under 0.2% of the roughly 38 billion tonnes of energy-related CO₂ emitted each year.[10] CCS works best on concentrated streams such as gas processing, fertiliser and ethanol. Capture on board ships is at the first-installation stage, and its international rules are unfinished.
Capture Methods
The difficulty and cost depend largely on how concentrated the CO₂ is. A more dilute stream means more gas to treat and more energy per tonne removed. There are three basic arrangements.
| Method | Process | Main use |
|---|---|---|
| Post-combustion | Flue gas passes through a chemical solvent | Power, cement, retrofit of existing plant |
| Pre-combustion | Fuel is turned into synthesis gas and CO₂ is removed from the pressurised stream | Hydrogen and fertiliser production |
| Oxy-combustion | Fuel burns in pure oxygen, leaving CO₂ and water vapour | Few plants, cement trials |
The range is wide. Gas processing and ethanol fermentation give almost pure CO₂, which is why the earliest projects were built there. Coal flue gas holds about 12% to 15%, gas turbine exhaust about 4% and the open atmosphere about 0.04%, which explains the very high energy demand of direct air capture.
Post-Combustion Capture with Amines
In the most common design, flue gas meets an amine solution in an absorber column, where the amine binds the CO₂ at low temperature. The loaded solution moves to a second column and is heated. The bond breaks, pure CO₂ comes off and the solvent returns to the start. Most of the energy goes into that heating step. On a power station the heat is taken from the steam turbine, so less electricity is available to sell. A feasibility study by the US National Energy Technology Laboratory for Canada's Shand plant calculated this parasitic load at 22.9%.[2] Modern design capture rates are generally around 90%, but operating results can fall short.
Transport and Storage
Captured CO₂ moves by pipeline or, once liquefied, by ship. Storage sites are deep saline aquifers and depleted oil and gas fields. Below about 800 metres the CO₂ becomes supercritical, its critical point being 31 °C and 74 bar. In that state it has a density close to a liquid, so the same mass takes up far less space.
Four mechanisms hold it in place. In structural trapping, an impermeable cap rock blocks upward movement. In capillary trapping, the CO₂ is held in the pore spaces of the rock. In solubility trapping, it dissolves into the formation water. In mineral trapping, it reacts with the rock to form solid carbonate. The later mechanisms grow in share as time passes, making storage more secure. The main operating concerns are pressure management, monitoring and leakage through old wells. Injecting CO₂ into oil fields, known as enhanced oil recovery, is also widespread, but the climate accounting is more contested since the result is more oil.
Operating Projects
| Project | Country | Start | Capacity | CO₂ source |
|---|---|---|---|---|
| Sleipner | Norway | 1996 | About 1 million tonnes a year | Gas processing |
| Boundary Dam | Canada | October 2014 | Design about 1 million tonnes a year | Coal power |
| Northern Lights | Norway | August 2025 | 1.5 million tonnes, phase two at least 5 million | European industry |
Source: Equinor; US Department of Energy; SaskPower data as reported in the press.[3][4][5]
Since 1996, Sleipner has injected CO₂ stripped from North Sea gas into a saline layer beneath the seabed, storing over 19 million tonnes by the end of 2022.[3] It remains the leading source of long-term monitoring data.
Boundary Dam is a commercial-scale capture plant fitted to a coal unit in Saskatchewan. Technical problems marked the early years, and its operator SaskPower paid penalties under its CO₂ delivery contract. An analysis by David Schissel found an average capture rate of 57% when flue gas vented directly is included. SaskPower disputes that framing and points to the first quarter of 2024 as its best period.[4] The case shows why design figures and operating figures need reading separately.
Northern Lights is a partnership of Equinor, Shell and TotalEnergies, and made its first injection in August 2025. CO₂ captured at an industrial plant is loaded into tanks at that plant's port, shipped to the Øygarden terminal in western Norway, then piped into a formation about 2,500 metres below the seabed.[5] The first phase is sold out and the second raises the total to at least 5 million tonnes. Linking emitter and storage site by sea creates a cross-border storage service, which the 2009 amendment to the London Protocol made legally possible.
Onboard Carbon Capture
Onboard carbon capture and storage (OCCS) separates CO₂ from the funnel gas and keeps it on the ship as a liquid in tanks. Like a scrubber it goes on the exhaust line, but it asks for far more energy, cooling and tank space. A Wärtsilä system on Solvang's LPG carrier Clipper Eris targets about 70% of the CO₂ in the exhaust, and one full-scale installation is showing capture of around 50 tonnes a day.[6]
Tank requirements follow directly from fuel burn. One tonne of VLSFO yields 3.114 tonnes of CO₂ on the FuelEU default factor.[7] At 70% capture, that leaves about 2.18 tonnes to store for each tonne of fuel. A ship burning 50 tonnes a day collects 109 tonnes daily and about 2,180 tonnes over a 20-day voyage. Taking liquid CO₂ at about 1.1 tonnes per cubic metre, that is close to 2,000 cubic metres of tank. The fuel burned on the same voyage is only 1,000 tonnes, so the CO₂ tank ends up larger than the fuel tank. Capture also takes energy, raising consumption. One scenario discussed by Maritime Executive pairs 75% capture with a 20% energy penalty.[6]
The hard limit lies ashore. Port facilities able to receive captured CO₂ are very few, and early discharges such as the Ever Top project remain trials.[6] On rules, the IMO approved an OCCS work plan at MEPC 83 in April 2025, and MEPC 84 in 2026 tasked a correspondence group with guidance on accounting, verification and certification. The full framework is targeted for 2028.[8] The European Commission has said OCCS is not currently recognised as a compliance technology under FuelEU.[6] The class society DNV has published its own recommended practice for measurement.[9]
Scale, Cost and Objections
Facilities rose from 50 to 77 in one year and capacity grew 25%.[1] Even so, 64 million tonnes is a very small part of global emissions. Costs vary widely with sector and CO₂ concentration, and most projects need a carbon price or state support. A common objection is that CCS may prolong fossil fuel use. Supporters answer that in cases such as cement the CO₂ comes from the chemistry and not the fuel: limestone breaks down and releases it, and changing fuel will not remove that source.
CCS enters carbon neutral plans as one way to shrink remaining emissions, and the footprint of blue hydrogen depends directly on the capture rate.
Frequently asked questions
What is carbon capture and storage?
Carbon capture and storage (CCS) separates carbon dioxide from a large source before it reaches the atmosphere, compresses and transports it, and injects it into deep geological formations for permanent storage.
Does stored CO₂ leak?
At well-chosen, monitored sites the cap rock holds it, and dissolution and mineralisation strengthen that over time. Old wells and faults are the main risk, which makes site selection and monitoring essential.
Is onboard capture an accepted compliance route?
Not fully. The IMO is working on a framework with a 2028 target, and FuelEU does not currently recognise it.
Are CCS and carbon utilisation the same?
No. CCS puts CO₂ permanently underground. Utilisation turns it into fuels or chemicals, and the CO₂ can return to the air when the product is burned.
Sources
- Global CCS Institute. Global Status of CCS 2025, October 2025, press release and summaries.
- National Energy Technology Laboratory. Shand CCS Feasibility Study presentation, 2019.
- US Department of Energy. DOE Study Monitors Carbon Dioxide Storage in Norway's Offshore Sleipner Gas Field; Equinor Sleipner data as reported in the press.
- Global News and CTV. Reports on SaskPower Boundary Dam performance and penalties, 2015 to 2024.
- Equinor. Northern Lights, project page.
- gCaptain. The State of Onboard Carbon Capture at Sea in 2026; Maritime Executive. Ship-Ready Onboard Carbon Capture Has Arrived.
- European Commission. Guidance on the FuelEU Maritime Regulation for Shipping Companies, 8 October 2025.
- International Maritime Organization. MEPC 83 meeting summary, 2025; ENGINE. MEPC 84: China Calls for More Progress on Onboard Carbon Capture Rules, 2026.
- DNV. New DNV RP Establishes Measurement Framework for Onboard Carbon Capture and Storage Systems, 2026.
- International Energy Agency. Global Energy Review 2025, CO₂ Emissions.
