I am not captivated by carbon capture

Paul Gunton

Paul Gunton · 15 April 2020


I confess that I am a bit late bringing you news that a small UK company has been awarded government funding to explore the potential of using on-board carbon capture to deliver a carbon-free future for global shipping.

A reader drew my attention last week to a news item published in March by PMW Technology, which is based in a science park at Chester University. It reported that it had been awarded funding for a six-month project to evaluate the potential of its ‘A3C’ process to “capture engine emissions with delivery of the captured carbon dioxide to ports.”

Man 191127 114353
The LNG-fuelled engines on the 17,500dwt car carriers delivered last year to Siem are at the heart of one of the project’s case studies (Image: MAN Energy Solutions)

This would “avoid the huge cost of new fuel production and delivery systems [and] allow retention of existing vessel and high performance engine designs, potentially offering a much lower cost of marine decarbonisation,” it went on.

I do not share the company’s confidence, at least as far as large ships on long voyages are concerned. For specific applications – the study is focusing on its potential for a small hybrid ro-ro ferry and an LNG-fuelled car carrier – the results so far seem more promising but if it is to be a global game-changer, large conventionally-fuelled vessels cannot be ignored.

‘A3C’ is an abbreviation for PMW Technology’s patented and award-winning Advanced Cryogenic Carbon Capture process, which separates CO2 as frost. At 287kWh per tonne of CO2, it uses less energy than other CO2 capture techniques, a summary of the research behind the process records.

PMW Technology’s proposal is that ships would be fitted with A3C systems to remove the CO2 from their emissions and store it on board as a liquid at -40°C and 10 bar pressure. Once it is offloaded ashore, it would be transferred to “geological storage” and the scheme would cut the cost of otherwise transitioning to carbon-free fuels “substantially”, the company predicts.

Its funding has come from the UK Department for Transport’s (DfT) Transport Technology and Innovation Grants (T-TRIG) scheme and is listed by the DfT as a 2019 grant. Work has been under way since January with a mission to “evaluate the feasibility, costs, infrastructure impacts and potential benefits of using advanced carbon capture technology to decarbonise marine shipping.”

Siem Confucius and Siem Aristotle Siem image
Siem Confucius has been used as a case study in this project (image: Siem Car Carriers)

The two vessels it is looking at as case-studies are the 8,041gt hybrid ferry Victoria of Wight, which operates on the short route between the UK mainland and the Isle of Wight, and the 17,500dwt LNG-fuelled vehicle carrier Siem Confucius, which operates for VW between Emden in Germany and Mexico, via the US east coast. Although both ships’ owners are aware of the project’s work, there are no plans to modify either of them to capture CO2.

I have put many of the points in this commentary to Paul Wilson, who heads PMW Technology, and to Jonathan Strachan, director of ship design and engineering at the naval architect involved in the project, Houlder Ltd, which had worked with Siem in obtaining plan approval of Siem Confucius and its sister, Siem Aristotle.

More CO2 than fuel

First, how much CO2 will need to be processed? When a tonne of LNG is burned, this table shows that it produces 2.75 tonnes of CO2. LNG’s density is about 450kg/m3 while liquid CO2 has a density of 1,101kg/m3 in its liquid form. When I crunched those numbers, I found that the tank volume required for storing that CO2 is 12.4% more than for the original fuel. In the case study, storage is provided by designating one of the ship’s existing two 1,800m3 LNG tanks as a CO2 tank.

Siem Car Carrier Houlder image
The yellow tints on this GA of Siem’s LNG-fuelled car carrier design shows where carbon capture and storage equipment would be located (image: Houlder)

At first sight, the maths says that this will fill up before the fuel tank is empty, but Mr Wilson has told me that its concept takes advantage of the need for less insulation around the CO2 tank, which means that a larger tank can be fitted into the same space. And since not all the CO2 will be captured (see later in this article), he assured me that by the time the fuel tank is empty, the CO2 tank will be 88% full.

It will, nonetheless, be heavier than the original fuel but Mr Strachan pointed out that ballast could be reduced to reflect the added mass. “Our studies indicate that there is no impact on cargo deadweight or the draught,” he said. Another option would be “to reduce the range and bunker fuel and discharge CO2 at both ends of the voyage.”

With a 50% reduction in fuel load and thus range, that seems to be the case here, with Siem Confucius’ range reducing from its present 12,000 n-miles to 6,000. But “if the full range is required, there would be a reduction in deadweight or an increase in draught,” he said. And he provided a figure: “in the full range case for the study on the car carrier, we are expecting to carry approximately 4,000 tonnes of CO2 on arrival.”

That is obviously more than double the amount that can be accommodated in the single tank allocated in the case study scenario so, for the full range option, “we propose to add further tanks forward of those shown on the GA to hold the additional of CO2,” Mr Wilson said.

“We will assess the scale of any loss of cargo carrying capacity where it arises,” he said, but by my reckoning, even allowing for the 1,450 tonnes of fuel that can be deducted from that 4,000-tonne figure, the extra weight of 2,500 tonnes is a lot of capacity lost from the ships’ 17,500dwt. The project team uses slightly different figures than me for LNG density and its mass conversion to CO2, but when it comes to assess cargo impact, its estimate will be in the same ballpark.

For HFO-fuelled vessels, the corresponding figures are larger. When a tonne of HFO is burned, it produces 3.11 tonnes of CO2; because of the density difference, it would need slightly less than three times the storage volume of the fuel that created it but that still represents a near quadrupling of the space allocated for fuel and captured CO2 than is currently needed for bunker tanks. And the CO2 tanks would have to be more sophisticated structures than normally used for bunker storage.

For a large container ship, for example, the equivalent figures to those mentioned for the case study’s car carrier would be huge. I have not been able to confirm the fuel consumption of the world’s largest box ship, the 23,756TEU MSC Gülsün, delivered last year, but an online item published by ABB in 2015 provides extensive relevant data about what was then the world’s largest-capacity container ship, the 19,224TEU MSC Oscar.

ABB’s report quotes MSC as describing it as “the most energy efficient vessel on the planet” because it used 35% less fuel per box than other ships and therefore provided an equivalent reduction in CO2 emissions, so I have taken that as my basis ship in this article.

Using the fuel consumption figure (in litres/day) mentioned in ABB’s item and the density of HFO in the table linked above, it burns 274 tonnes of HFO per day, which creates 852 tonnes of CO2 that would have to be stored until it could be discharged in a port. It operates on MSC’s Albatross service on which the longest leg is between Tanjung Pelepas and Rotterdam, a sailing time of 19 days, during which time 16,188 tonnes of CO2 would be produced and would need accommodating.

Meanwhile, allowing for the fuel burned, its displacement will have increased by 10,982 tonnes, which represents a lot of cargo it would not be able to load.

Extra power

Second, how much engine power will be needed to capture all this CO2? For MSC Oscar, to generate the 287kWh required to process each of the 852t of CO2 produced each day at sea would need 244.5MWh per day, which would require a constant electrical supply of 10,200kW. That is 16% of MSC Oscar’s 62,500kW main engine output, so it would either have to slow down or have a major engine upgrade to support the A3C equipment. And that, note, does not take into account any of refrigeration power needed to maintain the CO2 in its liquid state.

I asked Mr Wilson about the extra power needed for the process including refrigeration, and he said the figure would depend on the fuel used, the percentage of CO2 captured and the vessel type, but “our case studies found it to be around 20% of cruise power.” I am sure a lot of owners and charterers will be concerned by that figure.

His reference to “the percentage of CO2 captured” may also stand out for those who are hoping for an entirely carbon-free industry. “The process can remove CO2 to very low levels but energy consumption rises significantly at higher rates so we expect 90-95% to be the preferred range,” he told me.

Space intensive

Third, how much space will this equipment need? Its award citation described the A3C plant as ‘intensive’ and reported that units with capacities of up to 250,000t/year of CO2 can be “delivered on a small number of conventional trucks.”

How much CO2 would MSC Oscar produce in a year? It calls at 11 ports on its Asia-North Europe run, so I guess it spends at least 100 days each year in port. Even if it burned no fuel in port, that leaves 265 days at sea, creating 225,780 tonnes of CO2 in a year. By the time days in port and the extra power required for the AC3 apparatus are added, it would certainly exceed 250,000t/year of CO2.

Victoria of Wight Hybrid ferry Wightlink pic
The hybrid ferry Victoria of Wight has been included in the project’s review (image: Wightlink)

I doubt there is enough spare room in MSC Oscar’s engineroom to fit the contents of one extra truck’s worth of equipment, never mind ‘a small number’ of them, plus the refrigeration plant. If I am right, that would require either lengthening the ship or further reducing its cargo capacity.

On smaller ships the space requirement will obviously be less and Mr Strachan told me that for the project’s case studies, it would be the equivalent of adding another generator and that there is room for that in Siem Confucius’ auxiliary machinery room. “There is also space on the top deck for the carbon capture and storage system [and] the stability check has confirmed that this works,” he added. While that might be an option for some ship types – such as car carriers and tankers –there is very little spare deck space on container ships such as MSC Oscar.

Shore infrastructure

Fourth, how will the shoreside infrastructure work? It will not be simple or cheap and I cannot imagine that many ports are conveniently located to transfer thousands of tonnes of liquid CO2 to geological storage. Norway is probably the country with the most experience of this but imagine Rotterdam or Tanjung Pelepas welcoming MSC Oscar’s 16,188 tonnes of CO2 every few weeks, repeated with varying quantities for every ship that calls. Where will they find geological storage for all this CO2 that will remain gas-tight for eternity?

You can tell that I am sceptical of this scheme and I asked Mr Strachan whether he thought it was practical. Based on the two specific vessel types the project is investigating, “the technology … has a very plausible application,” he told me. These may not be the most challenging vessel types, he acknowledged, but “compared with some of the zero-carbon alternatives – hydrogen, ammonia, batteries, nuclear – I do think it is worth considering.”

I think it will be a fine balance between its benefits and the alternative fuels Mr Strachan listed. For one thing, apart from nuclear, none of those four options requires complex shore-side post-voyage and long-term waste disposal infrastructure.

I accept that the technology may work on some vessels and on some routes but for large vessels on long routes, I believe this is a non-starter and for that reason I do not think it offers a serious alternative for reducing the industry’s carbon emissions. But then, none of the alternatives in Mr Strachan’s list is ready to fuel the world fleet, either.

So I am willing to be convinced that carbon capture can work and am looking forward to seeing the outcome of the ongoing study, which is due to finish at the end of June. After that “our next step is to undertake a basic design scope for the installation on a vessel and obtain approval-in-principle from a class society,” Mr Strachan said. Parallel with that, “we would work with PMW to complete sufficient design work to be able to build a prototype that could be connected to a marine generator test bed.”

If there is a path from this to an alternative means of decarbonising shipping, I will back it wholeheartedly, but it must address all the points I have described, any one which represents a major hurdle when considered for large scale application.

• Do you think carbon capture – in this or any other form – offers a real alternative to zero-carbon fuel? Email me now with your views.

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