Carbon capture and storage (CCS) describes the process of extracting CO2 from emissions (produced from industrial processes), then transporting it (via ship or pipeline) for permanent storage. The aim of CCS is not to reduce or offset emissions, but instead to capture them at the source and stop them from entering the atmosphere in the first place. In this article, we provide a comprehensive overview of CCS, including what it is, how it works, and more specifically what it means for global shipping.
What is carbon capture?
Carbon capture technology is a key component in the quest to reduce CO2 emissions and address climate change. Carbon capture is the first of the three stages of carbon capture and storage. CO2 can be captured from large-scale industrial processes, such as power plants and the movement of vessels as part of global shipping.
How does carbon capture work?
The main aim of carbon capture is to prevent CO2 that is produced during industrial processes from entering the atmosphere. There are three main ways in which this is achieved:
- Post-combustion
This refers to removing CO2 after burning the fossil fuel. Post-combustion carbon capture sees CO2 captured from the exhaust and then transported and stored.
- Pre-combustion
This refers to capturing CO2 before burning the fossil fuel. In order to do this, the fossil fuel is partially burned in a gasifier to produce a synthetic gas (mainly a combination of CO2 and hydrogen). It is then relatively easy to separate the CO2 and hydrogen, with the former being transported and stored and the latter being used as an alternative fuel.
- Oxyfuel combustion
This refers to burning the fossil fuel in oxygen instead of air. As a result, mainly just CO2 and water vapour are produced. This is more environmentally friendly as the water condenses and the CO2 can be captured, transported and stored.
What is carbon capture storage?
Carbon capture storage describes the process of storing CO2 which has previously been collected. There are three steps to the CCS process:
- Capture the CO2
Separate the CO2 from other gases co-produced during industrial processes. - Transport the CO2
Compress the CO2 and transport it to the storage site via pipelines, road and/or ship. - Store the CO2
The CO2 undergoes the necessary steps required to permanently store it. These will vary depending on the storage method chosen.
There are a few different ways in which captured CO2 can be stored, including:
- ‘Unmineable’ coal
For various reasons, some coal is too difficult to mine, however if it is permeable enough, it can absorb CO2 and be used as a permanent storage option.
- Saline aquifers
These are deep rock formations with concentrated brine (salt water) in their pores. These act like big sponges, which are able to absorb previously captured CO2.
- Mineral storage
With this option, thanks to a process called mineral carbonation, captured CO2 reacts with the iron, magnesium, and calcium naturally found in rocks. This naturally occurring process prevents CO2 being released back into the atmosphere.
- Enhanced oil recovery (EOR)
Captured CO2 can be injected into depleted oil and gas reservoirs. This has the added benefit of helping to increase oil production, meaning the cost of CO2 storage can be offset by the money made from selling the additional oil.
How does carbon capture impact shipping?
The Paris Agreement in 2015 set an ambitious target to limit future temperature increases to 1.5°C. It will take a global effort across all industries to achieve this – and shipping is no exception. The need for more environmentally friendly operations is a high priority for all industries. This is particularly true for shipping, given it is responsible for approximately 2.5% of global carbon emissions.
There have been widespread global efforts to curb greenhouse gas (GHG) emissions in a bid to tackle climate change. A range of new regulation and legislation has been introduced, as well as a general move towards renewable energy as part of the wider energy transition. For example the International Maritime Organization (IMO) has introduced a target to reach net-zero GHG emissions by or around 2050, as well as a range of mandatory measures to help achieve this. This is having a range of knock-on effects for shipping as carbon storage efforts ramp up.
Carbon capture impacts shipping in a range of ways, such as:
- On board CCS technology may become commonplace in a bid to support decarbonisation
- The need to integrate onboard CCS systems with other onboard systems will increasingly influence vessel design and layout
- CCS offers a viable route for helping the industry become more sustainable
- Encouraging the development of a range of new carbon capture technologies ahead of predicted widespread deployment in future
- Installing onboard carbon capture technology offers a relatively fast way to reduce CO2 emissions across the shipping industry
What is onboard carbon capture and storage?
Onboard carbon capture and storage (OCCS) refers to the installation of carbon capture and storage systems directly on a vessel. This innovative approach involves integrating the CCS system with the ship’s fuel system enabling CO2 to be immediately captured and stored during the vessel’s operation.
There are two main approaches to onboard carbon capture and storage on ships:
- Pre-combustion
The ship’s fuel is converted into a gas mixture (usually hydrogen and carbon monoxide). The carbon is separated and captured as CO2 before the combustion process. The remaining hydrogen-rich gas is then used in dedicated energy conversion machinery.
- Post-combustion
CO2 is captured from the vessel’s exhaust, cleaned, separated, and then stored onboard. It can be stored either in liquid form in high pressure tanks, or in solid form as a mineral. The CO2 is then later offloaded.
Onboard carbon capture and storage on ships is attracting growing interest as it supports decarbonisation efforts while still allowing the use of traditional maritime fuels.