Charting the path to greener shipping with onboard carbon capture

The global shipping industry faces growing calls to become more sustainable – and fast. At the beginning of the year, the sector became part of the EU’s extended Emissions Trading System (ETS) to combat climate change, which means that shipping companies must now monitor their emissions and surrender EU allowances for every ton of greenhouse gases (GHGs) they emit. The aim of ETS is to promote the uptake of energy efficient, low-carbon solutions, and reduce the price difference between alternative and traditional maritime fuels. Yet for an industry that generates around 3% of global emissions and is still largely powered by fossil fuels, overnight change is a big ask. Many proposed solutions, such as alternative fuels, green corridors and nuclear power, are still in their infancy, forcing leaders to look for more immediate ways to reduce their environmental impact. One interim measure gaining attention is onboard carbon capture (OCC).

Already a well-known technology on land, the premise of carbon capture is to capture and store carbon emissions at source before they are released into the atmosphere. Companies are now looking at how they can apply this technology onboard ships. Called OCC, it involves capturing the carbon dioxide (CO2) vessels produce from carbon-based fuels and storing it onboard in tanks or containers before it’s later offloaded to a special facility on land.

A key benefit of OCC is that it would allow shipowners to reduce their GHG emissions while continuing to use conventional maritime fuels. It’s estimated that by installing OCC technology onboard maritime vessels, ship owners could reduce tank-to-wake emissions by around 75 to 80%.

Buoyed by this promise, industry regulators such as the International Maritime Organization (IMO) are looking into how to support and drive the uptake of OCC in the maritime industry as an effective carbon emission reduction measure.

What is onboard carbon capture (OCC)? 

OCC is a broad term used to describe a range of systems and technologies that integrate with ships’ existing fuel systems, capture the carbon dioxide they emit and store it onboard. There are two main ways that this can be done:

1. Pre-combustion: the ship’s fuel is converted into a gas mixture consisting of hydrogen and CO2 and the carbon dioxide is captured before combustion
2. Post combustion: the carbon dioxide is captured once it has been emitted from the ship’s exhaust. It’s then stored onboard as a liquid, gas or mineral before it’s eventually offloaded.

How does onboard carbon capture work?

While several OCC technologies are suitable for maritime applications, post-combustion capture currently leads the way, in large part because of its high technology readiness. In this instance, the carbon is stored onboard once it has been separated from the exhaust fumes after combustion. There are two main ways that the carbon can be stored:

1. Liquid: Carbon dioxide is compressed and cooled to a liquid where it is then stored in tanks.
2. Solid mineral: The carbon dioxide reacts with minerals to form a solid, such as limestone, and is stored in containers.

The captured carbon is then transported and stored offshore in expended oil and gas reservoirs and coalbeds.

Is carbon capture on ships feasible?

Yes, carbon capture on ships is feasible. Although certain types of vessels are more suited to OCC than others. Bulk carriers and tankers will be the most viable because of their scale and the fact that they have more available space on deck compared to other vessels such as cargo and container ships.

Generally speaking, though, installing OCC technology on ships is a more complex undertaking than onshore facilities. Maritime classification society DNV lists some of the challenges that will need to be considered and overcome:

• Increased fuel consumption: The OCC system will require energy to capture, separate and liquefy the carbon, meaning that the vessel will burn more fuel.

• Integration with existing ship systems: OCC systems will need to integrate with existing onboard machinery without affecting the operational performance of the vessel.

• Making space for OCC: All the equipment for capturing, separating, liquefying and storing the carbon takes up space and will need to be accommodated onboard while limiting the impact on cargo capacity.

• Compliance with industry regulations: Shipowners will need to comply with new regulations around safety, performance and emissions.

• Setting up an integrated value chain: Ports, bunker suppliers and fuel producers will need to work together to establish a suitable transportation, storage and transfer arrangement. Ports will need facilities in place to support the de-bunkering of captured carbon.

Is carbon capture being used now?

Carbon capture technologies, particularly within the maritime space, are still in the early stages of development. Globally, there are currently more than 35 carbon storage projects in operation with the capability to store 37 million tons of carbonper year. If we are to succeed in reaching net-zero by 2050, that capacity will need to be more than 100 times higher, according to DNV.

Here are some notable maritime projects underway:

• Northern Lights: Northern Lights is on track to be one of the first projects to deliver cross-border carbon dioxide transport and storage as a service. It involves the development of both a carbon storage value chain and the required liquefied CO2 carriers. The ships will deliver CO2 from capture sites to a receiving terminal in western Norway for intermediate storage, before its transported via pipes to a permanent storage reservoir 2,600 meters under the seabed.

• Porthos: Expected to be operation by 2026, the Porthos project will capture carbon emissions from the Port of Rotterdam and transport it through an offshore pipeline network to an empty gas field three to four kilometers beneath the North Sea.

• Acorn: In Scotland, a group of industrial, power and hydrogen companies have joined together to develop a CO2 transport and storage infrastructure capable of capturing their carbon emissions and moving them permanently into geological stores deep under the North Sea.

• Marine engineering company Deltamarin and Greek CO2 services company ECOLOG have partnered up to design a liquified CO2 carrier complete with LNG dual-fuel propulsion, shore power and wind assistance to keep its environmental footprint to a minimum.

• HD Hyundai Heavy Industries and Capital Gas Ship Management have secured approval in principle for the design of their liquified CO2 carrier from classification society Lloyd’s Register. The vessel will be capable of transporting 40,000 cubic meters of CO2.

As more projects like this get underway, one of the main obstacles to OCC adoption remains a lack of regulatory guidelines around the technology and clarity as to whether or not OCC will be deemed a sufficient enough measure to meet carbon reduction goals in the short to medium term. To boost commercial certainty in OCC, IMO has set up a correspondence group to develop a regulatory framework for the use of OCC systems. It’s hoped that by making OCC economically viable, shipowners will increasingly use it as part of a wider strategy to decarbonize the industry and help to reduce demand for alternative fuels in the process.

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