Onboard carbon capture and storage (CCS) is a promising technology that can significantly reduce greenhouse gas emissions from ships. By capturing and storing carbon dioxide, this technology can help the shipping industry meet its sustainability goals. According to Wartsila, let’s explore how CCS works and its potential benefits.
It’s Importance
Carbon capture is a method of capturing CO2 from fossil fuel after it is combusted in an engine before it can be released into the atmosphere. The technology can also be used with fuels such as methanol to make them net carbon-negative. It is an important new technology because it can be retrofitted to most vessels to immediately reduce carbon emissions. If a vessel currently running on fossil fuels were to install a carbon capture system with a 70% capture rate, it would be possible for that vessel to meet 2040 maritime decarbonization targets from day one.
Understanding The Working
The first stage is the pre-conditioning. This is where the exhaust gas is cleaned and cooled down. For high-sulphur fuels this requires a scrubber to remove SOx and then a WESP to remove PM. The pre-treated exhaust gas then travels to the bottom of the absorber.
The second stage is the absorber. A liquid amine-based solvent enters the top of the absorber where the gas and solvent mix. This captures the CO2 in the solvent. The cleaned exhaust gas exits the system and the CO2-saturated solvent is pumped via a heat exchanger to the stripper.
The third stage is the stripper. The solvent is heated, releasing the CO2. The lean solvent is recirculated to the absorber and reused.
The fourth stage is liquefaction. The CO2 is compressed, dried and cooled down to liquid form for storage.
The fifth and final stage is storage. The liquid CO2 is pumped through pipes to onboard tank(s), where it is stored until it can be offloaded.
Decarbonisation Strategy
The IMO’s target is for the shipping industry to be carbon neutral by 2050. There are many possible ways to achieve this target, but they can broadly be categorized into three areas:
- Increasing energy efficiency
- Moving to lower-carbon alternative fuels
- Investing in abatement technologies
Different vessels will require a different combination of solutions. Some technologies are still being developed, while others are already available and economically viable. Rotor sails, for example, can reduce emissions by up to 7–8% and a new optimised propeller by 10%. Synthetic fuels, which have zero CO2 emissions from a tank-to-wake perspective, will be an essential part of decarbonization. Many industry analysts predict that green synthetic fuels will become widely available at scale in the late 2030s and early 2040s. Existing ships will require significant retrofitting to take advantage of the benefits that these fuels will bring.
Carbon capture and storage (CCS) can be a key part of the shipping industry’s decarbonization strategy.
Challenges And Limitations
A wide variety of vessels can benefit from a CCS system designed for a straightforward retrofit. There are three main challenges to consider when deciding if the technology is right for your vessel. The first is that carbon capture comes with an energy cost. Vessels with a carbon capture system may choose to only capture as much CO2 as is needed to comply with regulations. This reduces the energy cost.
The second challenge is that a CCS system takes up space. In some cases this means some cargo space must be sacrificed. Individual operators can make their own cost-benefit analysis or ask their OEM to help them perform the calculation. Future legislation and carbon taxes will affect the payback time for a CCS system. The higher the carbon tax, the shorter the payback time.
The third challenge is what to do with the captured carbon. The industry is still debating who should take ultimate responsibility, but infrastructure is already being developed rapidly as CCS is being used in shore-based industries.
Estimated Cost
It’s hard to put an exact price on the cost of carbon capture as it will vary by vessel, desired capture rate and storage capacity. Based on Wärtsilä’s own calculations, a rough estimate would be €50–70 ($54–$76) per ton of CO2 captured including CAPEX and OPEX. The CAPEX of a carbon capture system includes the cost of buying and installing the system; the OPEX includes crew attendance, solvents, energy consumption and servicing.
When considering cost, it’s worth comparing the cost of fuels and the need for vessel modifications. Low sulphur fuel oil (LSFO) is much more expensive than heavy fuel oil (HFO), and alternative fuels like methanol and ammonia are more expensive again, as well as requiring significantly higher storage capacity. Switching to alternative fuels is one excellent option to ensure compliance for your vessel. If this isn’t an option in the short term, installing a carbon capture system can ensure compliance while still sailing on HFO.
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Source: Wartsila
