Carbon Capture and Storage (CCS)

Carbon Capture and Storage is recognized as one of several tools available to help reduce atmospheric carbon dioxide levels. As a potential temporary solution, it can play a valuable part in global efforts to mitigate climate change.

The London Protocol (LP) under IMO is the only international treaty providing a legal framework to regulate and enable the safe injection and storage of CO₂ in sub-seabed geological formations for permanent isolation.

What is Carbon Capture and Storage?

Carbon Capture and Storage (or "Sequestration") - known as CCS - refers to technologies that capture the greenhouse gas carbon dioxide (CO₂) with the aim of the storing it safely underground (sequestration) for permanent isolation. It could be one of the key tools to help tackle global warming.

How does CCS work?

1. Capture phase

The CO₂ from point sources such as large industrial facilities, including steel mills, cement plants, petrochemical facilities, coal, and gas power plants, is captured before it is emitted to the atmosphere, or from the atmosphere. Different capture methods are applied depending on the emissions source, but it generally involves the purification of CO₂ so that it can be economically sorted.

2. Transport phase

Once separated, the CO₂ is compressed into a liquid state for transportation. The compressed CO₂ is then dehydrated before being sent to the transport system. Commercial-scale transport of CO₂ uses tanks, pipelines, or ships for gaseous and liquid CO₂.

3. Storage phase

Following transport from the source to the storage site, the CO₂ is injected into deep underground rock formations, often at depths of one kilometer or more, where it is permanently stored. The rock formations are similar to what has held oil and gas underground for millions of years.

What are the cost and benefit of CCS overall?

According to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6), CCS is a critical technology for mitigating CO₂ emissions, especially in sectors where emissions are hard to eliminate.

Cost of CCS

The IPCC's AR6 Working Group III Summary for Policymakers presents an overview of mitigation options, including CCS, in Figure SPM.7. This figure illustrates the estimated ranges of costs and potential for various mitigation strategies in 2030.

Benefits for CO₂ reduction

CCS offers significant potential for reducing CO₂ emissions, particularly in cement, steel, and chemical production sectors, where alternative mitigation options are limited. By capturing CO₂ emissions at the source and storing them underground, CCS can prevent large volumes of CO₂ from entering the atmosphere.

CCS can be combined with bioenergy (BECCS) to reduce harmful emissions, effectively removing CO₂ from the atmosphere. This combination is vital for scenarios that limit global warming to 1.5°C or 2°C.

Parties to the LC/LP have, however, also stressed that CCS should not be considered as a substitute to other measures to reduce carbon dioxide emissions, but is one of a portfolio of options to reduce levels of atmospheric carbon dioxide and as an important interim solution (see resolutions LP.1(1) and LP.5(14)).

How does IMO's London Protocol regulate offshore CCS and protect the marine environment?

The London Convention (1972) and the London Protocol (1996), two free-standing global treaties, form the core of the IMO's legal framework to control marine pollution from disposal of wastes and other matter.

The LP is the more modern and comprehensive of the two treaties, providing a precautionary framework for Parties to effectively prevent marine pollution caused by dumping activities at sea. As this treaty aims to protect and preserve the marine environment from all sources of pollution, the Parties to the LP have been responding to emerging technologies and threats to the oceans by regulating new climate change mitigation technologies - including CCS in sub-seabed geological formations and marine geoengineering activities such as ocean fertilization. This preventive approach helps ensure that such interventions are carefully assessed and managed in order to protect the ocean environment and biodiversity.

What is the legal basis for CCS under the London Protocol?

In 2006, recognizing CCS technology’s role in achieving the net zero goals and the rapidly growing interest in CO₂ storage projects, the LP Parties adopted amendments to Annex 1 of the Protocol. This includes CO₂ streams from CO₂ capture processes for storage to the list of wastes or other matter that may be considered for dumping. These amendments provided a legal basis in international environmental law to regulate the injection of CO₂ streams into the sub-seabed geological formations for permanent isolation.

Under these amendments, which entered into force in 2007, CO₂ streams may be considered for dumping at sea only if the disposal is into a sub-seabed geological formation and they consist overwhelmingly of CO₂ and no wastes or other matter should be added for the purpose of disposal.

One significant consequence of these amendments is that such offshore CCS activities are now subject to the licensing arrangements contained in the instrument, as well as a mandatory impact assessment.

What about exporting CO₂ streams for storage?

Article 6 of the LP prohibits the export of waste or other matter for dumping in the marine environment, therefore, cross-border transport of CO₂ for permanent geological storage of the seabed was prohibited.

In 2009, the LP Parties amended Article 6 banning the export of waste to permit the export of carbon dioxide streams for disposal following Annex 1, provided that an agreement or arrangement had been entered into by the countries concerned. This enabled transboundary CCS projects—as long as all environmental protection standards and other requirements under the LP are fully met.

One consequence of including CCS under the London Protocol is that such activities are now subject to the licensing arrangements contained in the instrument as well as a mandatory impact assessment. To facilitate the licensing process, the Contracting Parties adopted, in 2012, a “Risk Assessment and Management Framework for CO₂ Sequestration in Sub-Seabed Geological Structures” and the “Specific Guidelines on Assessment of CO₂ Streams for Disposal into a Sub-Seabed Geological Formations”. These documents provide advice on how to capture and sequester CO₂ in a manner that meets all the requirements of the LP and is safe for the environment, both marine and atmospheric, for the short- and long-term.

Although adopted in 2009, the amendment to allow the export of CO₂ for sub-seabed storage under the LP has not yet entered into force. It requires formal acceptance by two-thirds of the Contracting Parties - only then will it become legally binding 60 days later. New Parties joining the LP can accept the amendment immediately, helping to build momentum toward its entry into force. The up-to-date list of acceptances can be found here.

Until the amendment is in effect, cross-border CCS under the LP remains legally restricted. Its eventual entry into force would mark a significant milestone in advancing safe, internationally coordinated offshore CCS, reinforcing the LP’s role in supporting climate action while safeguarding the marine environment.

What about provisional application of the 2009 amendment?

In 2019, the Parties adopted a resolution to allow the provisional application of the 2009 amendment as an interim solution, pending sufficient acceptance by Contracting Parties. This enables countries that wish to do so to implement the provisions of the 2009 amendment before its formal entry into force (Resolution LP.5(14)).

Following the resolution, Parties that have deposited a declaration on the provisional application of the 2009 amendment are allowed to export CO₂ in line with its provisions. This resolution also urged Parties to consider accepting the amendments to Article 6 of the LP. The up-to-date list of declarations can be found here.

*Provisional application allows countries to temporarily apply provisions of a treaty or amendment before it formally enters into force. In the case of the London Protocol, this enables Parties to begin exporting CO₂ for sub-seabed storage under the 2009 amendment, provided they submit a formal declaration and notify the IMO of any relevant agreements. This approach supports early action while legal entry into force is still pending.

Table. Contracting Parties accepted 2009 amendment and declared its provisional application

	Acceptance of 2009 amendment	Declaration of provisional application
Contracting Parties	Australia, Belgium, Croatia, Denmark, Estonia, Finland, the Islamic Republic of Iran, the Netherlands, Norway, the Republic of Korea, Sweden, Switzerland, and the United Kingdom	Australia, Belgium, Denmark, the Netherlands, Norway, the Republic of Korea, Sweden, Switzerland and the United Kingdom
Number of Parties	13	9

What about CCS systems on ships?

IMO is advancing efforts to regulate Onboard Carbon Capture and Storage (OCCS) systems—procedures designed to capture CO₂ emissions directly from ships before they are released into the atmosphere. At its 83rd session in April 2025, the Marine Environment Protection Committee (MEPC 83) approved a work plan to develop a regulatory framework for OCCS.

This includes creating technical guidelines for testing and certifying capture systems, as well as protocols for measuring and verifying emissions, including methane (CH₄) and nitrous oxide (N₂O), potent greenhouse gases. A dedicated Correspondence Group was also re-established to continue developing the framework and report progress to MEPC 84 to finalize the regulatory structure by 2028. These steps mark a significant move toward integrating OCCS into the IMO’s broader climate strategy for international shipping

What about transportation of captured CO₂ by ships?

The CO₂ captured and temporarily stored on board may be offloaded at terminals for either use as a feedstock to create products or services, or for permanent storage. Currently, liquefied CO₂ (LCO₂) shipping is mostly used in the food and beverage industry with fairly pure CO₂ and at a relatively small scale. However, with the increasing need to reduce GHG emissions and the scaling up of the global CCS capacity, the need for LCO₂ to be transported by ships between the capture site, including carbon captured on board, and storage locations, is expected to increase. Currently, technical requirements and standards for transport of LCO₂ by ships are given in the IGC Code and the IMDG Code of the IMO regulation.

The IGC Code sets out mandatory provisions for the design, construction, and equipment of ships to ensure the safe use of liquefied gases, including CO₂. This Code mandates robust containment systems, and precise temperature and pressure control mechanisms to ensure that potential hazards, such as leaks, explosions, and environmental contamination, are effectively managed. Currently, the IGC Code, including provisions on carriage of LCO₂, is under review by the CCS Sub-Committee of the IMO.

The IMDG Code was developed for maritime transport of dangerous goods in packed form, to enhance and harmonize the provisions concerning safe carriage of dangerous goods and to prevent pollution of the environment. This Code classifies LCO₂ as dangerous goods and outlines specific requirements for labeling, packaging, and emergency response procedures.