Proven land-based technology for capturing CO2 emissions, carbon capture and storage is being examined for shipboard use, but high capex, opex and complexity problems must first be solved
Well proven in land-based industrial applications since the 1970s, carbon capture and storage (CCS) is a promising technology to remove CO2 emissions from vessel exhausts, but before that happens, developers must overcome several challenges, namely system size, complexity, cost and high energy consumption.
These technical and commercial challenges were discussed in great detail by three expert panellists at Riviera Maritime Media’s Carbon capture for shipboard use and monitoring webinar, part of Carbon Capture & Storage Webinar Week produced by LNG Shipping & Terminals and Marine Propulsion. Held in May, the event was sponsored by TECO 2030, with support from the Carbon Capture & Storage Association.
One of the panelists, Mitsubishi Shipbuilding deputy manager, strategic planning and operations Kazuki Saiki said ship-based CCS should be part of the same discussions as those around alternative fuels in achieving zero emissions.
“IMO 2050 goals are accelerating the discussions around hydrogen, ammonia, biofuels and synthetic fuels. Along with that, we believe that onboard carbon capture is one of the options,” he said. He added that the Japanese shipbuilder, however, was also researching ammonia fuels and electrification of small ferries, emphasising it was taking an open-minded approach to support shipowners in meeting their decarbonisation targets.
Fellow panellist TNO research scientist Jaspar Ros explained that the concept of shipboard CCS involves capturing CO2 emissions from a ship’s exhaust, then liquefying and storing it on board. Once the ship reaches a port with the proper CO2 infrastructure, the liquefied CO2 is offloaded for storage or sequestration – eliminating the carbon dioxide from entering the atmosphere. Additionally, the captured CO2 can be utilised in the production of products, such as cement or converted for use in chemicals and new synthetic carbon-neutral fuels.
“We need a level playing field from the legislators, and that challenge is as big as our technology challenge”
TNO first proposed shipboard CCS in 2017 and has conducted two funded projects, CO2STS and DerisCO2. In the DeriCO2 case study, TNO worked with Dutch marine contractor Heerema Marine Contractors (HMC) on the LNG-fuelled semi-submersible crane vessel Sleipnir. These projects, Mr Ros said, lifted the technology from TRL 4 to 5. ‘TRL’ refers to ‘technology readiness level’, estimating the approximate maturity of the technology. TRL 4 means the technology was validated in the lab, while TRL 5 would mean it was validated in a relevant industrial environment.
One of the issues examined in the DerisCO2 study was opex. While land-based CCS systems experience constant loads, this is not the case in shipping, explained Mr Ros. “You can capture 100% of the time or can handle 100% of the flue gas in the system, but the problem is that you have quite a high capex. So, there will be some kind of optimisation where you limit the size of your carbon capture plant, and thereby also limit the gain,” he said. Additionally, TNO examined the effect of ship motion on the CCS plant to see if rolling would impact the carbon capture rate. Initial tests were encouraging, showing no ill effects from such motion.
Through its studies, TNO examined seven LNG-fuelled ships to determine the cost of shipboard CCS. The analysis did not take into account costs related to port sequestration. Mr Ros said the studies showed a strong economy of scale. “If you go for very small ships, it will be expensive, but if you go for large ships it will become much cheaper.”
TNO’s analysis showed carbon capture costs for all the ships it studied would be somewhere around €100 to €200 (US$122-US$244) per tonne of CO2. It expects with widespread implementation of the technology, the costs should drop below €100 (US$122) per tonne of CO2.
The next steps: a demonstration
“We have done a lot of analysis on these ships, and the next step is now a demonstration of the technology,” said Mr Ros. Under a project called EverLoNG, TNO would work with HMC on the technical feasibility and economic viability of a shipboard CCS. This would lift the technology to TRL 7 said Mr Ros – a prototype demonstration – laying the groundwork for installing a full-scale CCS plant onboard Sleipnir by 2024.
Previously, HMC has said the overall objective of this project was to implement a safe and economic CCS system on board Sleipnir in order to “virtually eliminate carbon emissions while running on LNG, without jeopardising operational performance and capabilities. Preliminary results show that up to 90% of all carbon emissions can be captured on board Sleipnir while working offshore, although the exact details and optimal economic performance of the plant have yet to be determined.”
Named for the eight-legged horse ridden by Odin in Norse mythology, 220-m Sleipnir is truly a powerful ‘beast’, with 12, 8-MW four-stroke, Tier III-compliant MAN 8L51/60DF dual-fuel engines capable of burning marine gasoil or LNG.
Shipboard CCS figures strongly into HMC’s ambitions to go carbon neutral, announcing its intentions in October 2020. “This will be achieved by means of prevention, reduction and compensation of carbon emissions,” said the company.
In principle, Mr Ros said, the technology can be applied to every fuel containing carbon. Heat from the exhaust gas stream can be used to drive the solvent-based CO2 capture system.
Mr Ros said TNO is proposing an aqueous amine-based CO2 capture because it is a proven commercial technology.
Mr Ros cited three main differences between shipboard CCS used on an LNG-fuelled ship and land-based carbon capture. First, heat recovered in the waste heat recovery system from the engine exhaust is used to extract the CO2 from the solvent. Second, while land-based CCS are optimised for energy demand, ship-based systems might be limited by height restrictions on ships. This might mean restricting the heigh of columns on board. And third, since LNG must be evaporated before being injected in the engine, and then using an intermediate refrigerant, you can perform the liquefaction of the CO2 before storage in the CO2 storage tanks.
“We expect commercial deployment of this technology from 2025 and onwards,” said Mr Ros.
Demonstrating CCS on bulk carrier
In his presentation, Mr Saiki detailed the Japanese shipbuilder’s research with K-Line and ClassNK, supported by the Japanese Government on a demonstration test of a marine-based CCS on an 88,000-dwt coal carrier Tohoku Electric. Mitsubishi Heavy Industries (MHI) supplied a modified version of its onshore carbon capture technology for the marine demonstration project. As in the case of TNO’s studies, Mr Saiki said that amine chemical absorption is used for the small-scale mobile demonstration plant. Under the CC-Ocean project about 0.1 tonnes/day of CO2 will be captured, compressed and bottled for laboratory analysis. The plant will be operated for about seven months on the bulk carrier. ClassNK will verify the technology, with a HAZID study on the equipment operation and chemical handling on board.
“Sadly, this is only 0.1% of the entire emissions from the ship,” said Mr Saiki, although the compact carbon capture plant could collect 65% from the ship’s exhaust gas. He believes that technically 90 to 95% could be achieved.
As it is a pilot project, CC-Ocean is not storing the captured CO2, “meaning that we whilst we confirm the separation of CO2 from the exhaust gas, then we release it back to the atmosphere,” noted Mr Saiki.
In the CC-Ocean demonstration, exhaust gas from the engine is fed into a cooling tower, where it is doused with an amine-based water solution. Through physical contact the CO2 is collected from the exhaust into the water solution. The clean exhaust gas is released, and the amine-based water solution is fed into a heating tower where the CO2 is separated and captured from the amine solution. The captured CO2 is compressed, refrigerated and liquefied for storage.
This process, noted Mr Saiki, is energy intensive. He says “almost 50% of the extra energy” required to run the CCS is spent cooling down and heating up this amine-based solution.
Besides additional energy consumption, a full-scale ship-based CCS would be “larger than a scrubber,” said Mr Saiki.
Expectations are that the pilot ship-based carbon capture plant will be installed in July onboard the K-Line coal carrier that operates between Australia and Japan. The testing will be broken into two segments, with the first month of operation conducted by MHI technicians and the next six months by the ship’s crew.
While the technology is feasible, Mr Saiki said the pilot testing wants to gather information on the effects of ship motion on the plant, how the sulphur content in the fuel used in the two-stroke engines affects the amine-based solution and the handling of the solution by crews in order to assess safety.
Joining the panel, TECO 2030 AS chief executive Stian Aakre, discussed the use of a shipboard CCS in combination with a hydrogen fuel cell. The CCS plant would capture CO2 from the ship’s main engine, while the hydrogen fuel cell would replace the ship’s auxiliary engines, powering the vessel. For the concept, a bulk carrier sailing on a 12-day voyage between Australia and Japan, the shipboard CCS plant would have a capture rate of 30% of the ship’s CO2 emissions. “It’s an important number to remember,” said Mr Aakre, “because the more you capture, the more you need to store.” For the concept, the ship would need to be equipped with four tanks for liquid CO2 storage and one for liquid hydrogen storage, all on the aft deck.
A key element of the concept is the TECO Future Funnel, which can be installed on all types of vessels, both retrofits and newbuildings.
Adaptable to future emissions regulations, the current Future Funnel ‘Gen 0’ uses a wet scrubber, removing about 98% of the SOx from a ship’s exhaust. An additional benefit, said Mr Aakre, is that “there’s a CO2 reduction of 20% by using a scrubber compared to utilising desulphurised fuel because when you desulphurise the fuel in the refinery, there is a significant energy penalty.”
Future Funnel Gen 1 will enable owners to comply with Tier III NOx regulations using SCR technology, with Gen 2 removing PM and black carbon in line with the expected rules in 2023 and Gen 3 incorporating CCS technology. Mr Aakre said the ambition is to capture about 90% of PM from ship’s emissions in order to meet future regulations.
“If you go for very small ships, it will be expensive, but if you go for large ships it will become much cheaper”
By 2030, TECO 2030 is aiming to capture about 30 to 40% of CO2 emissions. This will help shipowners comply and meet IMO’s targets of reducing GHG emissions by 40% by 2030 compared to 2008 levels. “If we assume that most shipowners and operators have come … by other measures … 10% towards the 2030 goal, then we will help them with the rest,” he said.
Indeed, TECO 2030 believes shipboard CCS can help shipowners meet IMO 2050 goals, too, through the reduction of carbon emissions by 60 to 70%.
Mr Aakre emphasised the importance of creating a level playing field to implement these emissions-reduction technologies. “It’s a big task that lies on the shoulders of the legislators,” he said. Legislators will have to address carbon accounting across the entire value chain. The accounting mechanism would depend on whether the CO2 is reused in industry to make products or permanently stored. “It’s a complex thing,” concluded Mr Aakre.
Oslo-headquartered TECO 2030 has examined both amine-based and cryogenic carbon capture solutions and looked at options for storing the CO2 in either compressed, liquid or solid forms. TECO 2030 has drawn up a solution using liquid CO2.
When the ship comes into port, it must offload the liquefied CO2, but this, of course, requires the port to have reception facilities – none of which currently exist.
This, however, believes Mr Aakre, will be resolved. He says it is analogous to when the first ships came into port with scrubber washwater. “Everyone was a little puzzled what to do, how to treat it, what it would cost, but today that is not a problem. It’s a regular commodity.”
In summing up, Mr Aakre said: “I think we have established beyond a reasonable doubt that onboard carbon capture is complex, expensive, and power consuming. So, to work with this, we need a clear and level playing field, from the legislators, and I think that challenge is equally big as our technology challenge.”
In wrapping up his remarks, Mr Aakre recommended shipping keep an open mind when addressing decarbonisation and assessing alternative fuel options. “There is no silver bullet and I urge everyone to not become religious in the belief in one [solution] rather than another because all good forces must pull together. The objective is bigger than one technology or another. [The objective] is to reach the environmental targets for the planet.”
A series of polls taken during Riviera Maritime Media’s Carbon capture for shipboard use and monitoring webinar revealed delegates’ attitudes towards the potential of ship-based CCS. See the results of those polls here.