Carbon capture – a ropax case study

2021-10-28T08:14:32+00:00 October 28th, 2021|Environment|

Deltamarin is investing in R&D to gain and maintain the industry-leading knowledge of the technologies implemented on ships, especially in the field of carbon capture.

The company explained that one of the emerging technologies that has received less attention in a maritime context is post-combustion carbon capture.

These systems can extract CO2 from a ship’s exhaust gases, after which the CO2 is liquefied, stored on board and eventually discharged to shore for either permanent storage or further use.

Deltamarin has recently participated in a joint project with Total, Minerva and DNV, where pathways to zero emissions were studied for tankers.

Carbon capture technology was studied among many other options and one of the conclusions was that it could provide ‘the 30% step’ in carbon footprint before going into more expensive low or zero carbon fuels.

This project was described as thought-provoking and led the company to examine the potential applications of carbon capture in more detail.

As a result, earlier this year, Deltamarin joined forces with Wärtsila Exhaust Treatment to study how the system could be implemented on board ropaxes. Wärtsilä has recently announced that it has product development under way and the company is also installing a pilot plant at its test facility in Moss, Norway.

Deltamarin opted for ropaxes, as they operate on fixed routes where the captured CO2 can be frequently discharged to shore and less volume is needed for on board storage.

In addition, several ferry operators have selected LNG as a fuel. LNG has some inherent benefits for use with an absorption-based carbon capture system, as it offers clean exhaust gases, and the engine fuel supply can be used as a heat sink for the captured CO2’s liquefaction.

It could also be possible to use the captured CO2 to produce synthetic LNG when combined into electrolysis and methanation processes, the company explained. As a result, some of the CO2 could be circulated back into the fuel supply.

However, this infrastructure would also need some adjacent industrial users for it to work.

The study compared a medium-size 155 m ropax newbuilding with alternative arrangements for MGO, HFO and LNG fuels, where two of the latter were also combined into a carbon capture system.

Exhaust gas treatment, the carbon capture system and related auxiliaries dimensions, were calculated in close co-operation with Wärtsilä, taking into account the heat balance of the ship.

The vessel was then compared in the technical aspects of CAPEX, OPEX and emissions on three different routes. Compliance with the current and upcoming regulations, such as EEDI and CII were also checked.

It was concluded that carbon capture is technically feasible within the given arrangement of the study ship without compromising cargo or passenger spaces.

Achievable CO2 capture rates would vary, depending on the operating profile from roughly 25% at the lowest for the HFO ship to nearly 40% for the LNG ropax. When comparing the emissions against an MGO burning vessel, the aggregate reduction with LNG and carbon capture could exceed 50%.

Additional CAPEX required for carbon capture and related auxiliaries was calculated in detail using Deltamarin’s cost modelling, plus information received from Wärtsilä. Taking into account the ropax total newbuilding cost, carbon capture implementation requires about 5-7% extra investment.

Deltamarin explained that achievable capture rates depended on a number of factors, one of which being – how much waste heat is available for the system. Capture rates can be analysed when heat balance of the ship, the systems’ space restrictions and their configuration are known.

Following these parameters, the carbon capture systems payback time depends on two main criteria: how much fuel is burned during the operation (frequency and speed on the route) and the level of tax applied on CO2 emissions (ie, the CO2 tax and CO2 disposal cost difference).

An HFO ship with carbon capture reached a return on investment (ROI) of less than five years at around €110 per tonne on the most intensive route. In general, the LNG fuelled ropax showed a faster ROI, as the capture rates were higher and the investment in the system was slightly less.

As a result, an LNG vessel reached five-year ROI at €50 per tonne on the fastest route. On slower routes, the ROI for both fuels was longer, but each of the examined combinations was under 10 years, and half of them below five years at €150 per tonne CO2 tax.

In conclusion, the study confirmed that carbon capture looked technically feasible for ship integration and a very interesting option in reducing CO2 emissions from ferries. The technology looks particularly promising for LNG-fuelled vessels, due to some inherent benefits of the fuel, Deltamarin said.

As the technology will be developed on existing knowledge of exhaust gas cleaning systems, it could become available on the market sooner than some of the low- and zero-carbon fuels that might require longer timelines to ensure that the supply and distribution infrastructure was available.