In this section, clicking on an image will usually enlarge it

For additional analysis based on responses to this web page visit “UK Zero Carbon Ship”

Can Commercial Shipping achieve net zero carbon by 2050?

My basic assumption is that IPCC are correct in their assesment of the impacts of Climate Change and what needs to be done to mitigate its effects. 

There are less than 30 years between now and 2050 when IPCC are seeking a zero carbon world. 30 years is (roughly) the life cycle of a ship. If we are going to achieve a useful result, then we need to start acting NOW. What, if anything, can the shipping community contribute to that target?

In summary, the development aims for ships that have applied during the last decade need to be refocused. The only way the shipping industry can approach zero carbon operations is by switching to hydrogen, or hydrogen derivative, fuels. Development focus over the last decade that has led to lower pollution from ships (for example, the LNG powered P&O cruise ship Iona) simply does not generate sufficient reduction in CO2 to impact on climate change

On the one hand, I am encouraged that the technologies exist to transform the shipping industry into something close to zero carbon operation (though some aspects need to be scaled up to industrial use). On the other hand I doubt the political will to make it happen in the timescale required.

One problem is that hydrogen is difficult to store safely, and even derivatives such as ammonia require pressurised and/or cooled storage, and a greater volume per unit of energy too. This will make it difficult to convert existing ships to the new fuels. Success at scale may have to rely on fleet replacement.

There is a circular problem. Shipowners will need confidence that there will be sufficient supply of appropriate hydrogen based fuels distributed to where ships need to load bunker before they will commit to building new ships, or converting existing vessels. On the other hand, governments and/or investors will be reluctant to construct new renewable hydrogen generating plants (from which safe hydrogen derivative fuels can be made) until they are assured that there will be sufficient ships passing their coasts and requiring bunker; and/or suitable tankers exist to transport the hydrogen derivative to where it is needed. An additional frustration about this loop is that the generation of renewable hydrogen could generate much needed revenue for countries most affected by climate change because of the availability of plentiful and reliable solar power or wind.

The International Maritime Organisation (a UN Body) has proved to be far too slow to achieve results. The shipping industry itself has demonstrated that it will adopt new technologies, but only when they are proven to work. The essential Hydrogen based energy will be more expensive than classic fossil based fuels. It will probably take a mixture of seed grants, research grants, taxation, regulation and penalties to make the industry move at the pace required. Above all, an effective carbon tax will be required designed to make sure that shipowners that adopt the new hydrogen based technologies are not placed at a competetive disadvantage  to the remaining traditional shipping stock. In an international environment,  this will be difficult to achieve.

I cannot claim this is a scientifically rigorous exercise. None of the data is mine. I have tried to acknowledge sources, and if I have failed to do so anywhere, I sincerely apologise, I am simply an observer trying to make sense of a complex subject.

I started by wondering whether the shipping industry might be able to make a constribution to a zero carbon world. My journey had many surprises, and I can only describe what I have found out.

It goes something like this

Until about 2018 the shipping industry was focused on reducing pollution. Luckily this work would also lead to significant potential reductions in GreenHouse Gas emmissions( GHG), but not enough

A lot of work was done and it was realised that significant GHG reductions were possible. I have used the JOULES project (An EU research programme running from about 2016)  to indicate how the industry was thinking. This project took a  number of “application cases” that demonstrated that, from a 2018 starting point, certain progress could be achieved by 2025. Much more, with new technologies, might be achieved by 2050

But the reality is that, even if the projects proposed in the Joules Project had been implemented, the scale of the problem is so large that there was no chance that the proposed gains could have been achieved to a meaningful extent by 2025 across the world fleet.

Looking further ahead to 2050, some new technologies were proposed

But the intervention of IPCC changed the rules, lifted the bar. Instead of pollution, the goal had been shifted to Climate Change. The rumours grew, but eventually in 2021, IPCC declared that the goal had to be close to zero carbon dioxide emissions by 2050,

This left the shipping industry (and the legislators) on the back foot.

According to the 3rd IMO GHG study. shipping was responsible for about 2.5% of global greenhouse gas (GHG) emissions (probably an underestimate). That does not sound a lot, but it is a clearly measurable contribution to the climate change problem

Projects like the Joules report clearly established a direction of travel, but the new requirements showed that improvements in hand at 2021 were simply not enough.

Shipping (and aviation) had been left out of the progressive international agreements, such as the Paris Agreement, because they were too difficult to regulate.

In my opinion, the European Union has set up and funded useful research projects that have investigated what might be done, even if, until 2018 they were focussed on, pollution reduction rather than climate change targets.

There has been a growing appreciation that in order to achieve a zero carbon shipping world, there needs to be a migration towards hydrogen and hydrogen derivative fuels. One of the strongest candidates for this is ammonia. No progress in this direction can be made unless and until this technology shift reaches wide acceptance. It seems to be the only pathway that could be achieved widely by 2050 because it relies broadly on existing technologies.

One of the few companies that has engaged this paradigm is Ricardo PLC  in the UK who have demonstrated that there are strong economic drivers toward the production of hydrogen derivatives such as ammonia in places like South America and Morocco by utilising the potential availability of hydrogen produced by renewable solar processes.

Other processes such as the pyrolysis process may make it possible to produce ammonia without having carbon dioxide as an unfortunate “waste” product. Such technologies are important, if not critical to the attempts to tame energy without adverse side effects.Various medium scale demonstrators of this process are already under way.

While it is tempting to think that in a world without oil (!) we will not need tankers, the reality is that we will still need some oil as feedstock to important chemical processes, and tankers for transporting hydrogen based fuels to where they are needed.

There may be opportunities to reduce the miles steamed by cargo ships. There are signs that the covid19 pandemic has forced some questioning of the desirability of very long just in time supply lines. That could lead to some manufacturing being relocated nearer to markets. Also, climate change has yielded a major benefit to shipping by opening the sea routes through the Arctic, shortening the sea journey from the far east to western Europe by about 40%.

There may also be limited opportunities to reduce the requirement for energy from fuels by using wind power on some ships. However, trials in the 1980s demonstrated that such gains are route sensitive, and there are operational issues, especially the need to avoid impeding cargo handling operations, and air draught in estuaries and rivers.

So, in a sentence, I am optimistic about the technology and pessimistic about the delivery timescale.

Graham Rabbitts

August 2021

#1.1 Ships at Sea – source:

Even before the report of IPCC Working Group 1 (WG1) had been published in August 2021, there were mutterings of concern, verging on alarm at the pace at which Climate Change was becoming evident, with flood, fire and drought proceeding to extremes on all continents’

#1.2 IPCC WG1 Report cover

It was clear that even lower targets would be set for Greenhouse Gas (GHG) emissions than had been current beforehand. I began to think about the impact on shipping. I soon discovered that shipping was responsible for about 2.5% of global greenhouse gas (GHG) emissions according to the 3rd IMO GHG study. Later, I came to the conclusion that this was probably an underestimate.

My original plan was to start a discussion in the Southampton Climate Conversations group on Facebook, but it quickly became clear that the problem was too nuanced for that to work, so I decided to publish this exercise as a section of my website.

When the WG1 report hit the media it became clear that at long last people are recognising that Climate Change is happening.

Recently there has been a focus on the Green House Gas (GHG) contribution from shipping, particularly in the Southampton area.

So I thought I would try to scale the problem. The first stop was to look at the extent of shipping. I chose to use the public database from Marine Traffic

The first image (#1.1) is shocking. Nearly all these ships are burning diesel fuel and emitting CO2. Recently there has been a ban on the worst kind of bunker fuel which has a very high sulphur content (though some think that there are so many exemptions that the ban will be ineffective). References to shipping in the Paris agreement discussions were ineffective because it was too difficult to deal with. Clearly we have a problem!

But hand wringing will not do. We need to understand the problem

The history of environmental concern may surprise some

In the late 1970s, the concern was that we would run out of oil by the 1990s, Few could even spell the word “environment”

#02.01 The Cockerell Raft –>

Then, Christopher Cockerell, the inventor of the hovercraft, proposed the use of a hinged raft to generate energy from waves. It was calculated that with the wave climate to the west of the UK, these rafts could provide 7% of UK energy.

At the time I was working for A&P Appledore, a marine consulting company. I was attracted to this scheme and eventually persuaded government to give us £100k to evaluate the practicality of using the Cockerell raft

A highly compressed summary is that, as each raft required 3000 tonnes of steel (the steel weight of a typical 15000 tonne dry cargo ship), it would take the entire berth capacity of British Shipbuilders (as it then was); and the entire plate production capacity of British Steel (as it then was) to support the programme. It would take 25 years to build the line of rafts along the west coast, by which time the rafts first built would need to be scrapped and renewed. It would be a project in perpetuity! This revealed that the key question was the net energy balance. Taking account of the need for support vessels, social support for the workers and so on, was it worth it? Would we get more energy out than we put in? Note that in this discussion there is no mention of environment. If we took that much energy out of the wave climate, what would it do to the coast? We did not even consider that question!

What we had done was refocus the question, but the establishment was not yet ready to accept that. The project languished.

By the mid 1980s I was Business Development Manager for Associated British Ports (ABP). This gave me access to a large number of shipping lines. We were still concerned about the possible shortage of oil by the late 1990s (yes, it seems absurd now). I became interested in a device called the Walker Wingsail, and in 1987 I persuaded a shipowner to fit one to a 4000dwt bulk carrier. It turned out to be an expensive trial because of the strengthening of the structure needed to accept the thrust created by the wingsail. But it was done. I spoke to the owner a year later and the Wingsail had been removed.

It seems that it worked well and produced the predicted fuel savings, but when the vessel was transferred to a different trade, the wind climate was less favourable (either ahead or astern) so the wingsail could not easily develop meaningful thrust. After that John Walker concentrated on a small unit for pleasure craft, but the concept never really caught on.

#2.02 Walker and SGS Wingsails

However, as I was writing this post in 2021, a new development by a company springing out of Southampton University emerged. It is from a company called Smart Green Shipping (SGS) . Maybe the time has come for the idea of wind propulsion/assistance for commercial ships to take root and flourish. To find out more, visit

The earlier experience suggests that care must be exercised in selecting the routes on which wingsails can provide real benefit; and attention needs to be paid to minimising the need for supporting structure and interfering with cargo handling operations when in port. At first glance, SGS seems to have addressed these issues. The earlier attempt in the 1980s avoided interference with cargo operations by mounting the wingsail aft on the superstructure, but this is not the strongest part of the ship, and it seems the consequence was expensive under deck strengthening.

#3.1 The infamous Hockey Curve

In 1988, under UN auspices, the International Panel on Climate Change (IPCC) was formed. The scientific community had seen the beginning of the infamous ‘hockey stick’ curve that showed a sudden and dramatic increase in the rate of world temperature rise. IPCC was tasked with understanding what was going on and predicting the likely outcomes. Their conclusions would become increasingly serious over the following decades, a theme to which I will return later.

In the early 1990s I was asked by ABP to set up an environment department to work out how ABP should respond to the deluge of environmental legislation that was emerging from Brussels. At that point few in industry were aware that well organised lobbying by major NGOs had produced an unquestioned momentum to legislate on environmental issues, both in the UK and Brussels. Indeed we did not even understand the distinction between an NGO, a government Agency, and a government department!

Some of the legislation was not well thought through, or overlapped with other legislation. Directives from Brussels had to be interpreted into UK Law by some legislation and many regulations. It was pretty daunting. An attempt to unravel the designations is on the Environment Page of my website, select the Designations Explained tab

Some NGOs were so convinced of the justice of their cause that they bypassed scientific justification in favour of emotional assertion. At ABP we were the only port Group (responsible for 25% of UK trade by weight), with our own marine research company (which to this day has an enviable reputation for scientific integrity). Uniquely in the Ports industry I had the resources to understand, and where appropriate, challenge the headlong dash for environmental regulation.

There are some 42 coastal designations of which 11 are statutory. Safetec produced a useful series of maps showing the different types of designation as part of their work to evaluate means of identifying the  Marine Environment High Risk Area called for by Lord Donaldson after his Braer accident enquiry.Though these maps are a bit out of date, they illustrate the extent to which UK coasts are already protected. Click on the items below to see the maps.

  1. Wildlife importance
  2. Vulnerability of birds to oil pollution
  3. Sensitive fishing sites
  4. Amenity and economic designations
  5. Landscape designations
  6. Designations considered but not included in the MEHRA evaluation
  7. Sites of geologiasl importance

By challenging some of the science, I became regarded as a bit of an environment denier. That was far from the truth, but I did regularly (at conferences and at meetings) challenge the methodology and logic of what was being proposed. For example, I caused great consternation by pointing out that “Sustainable Development” (which became a fashionable concept in the 1990s) was meaningless unless there was development. Some NGOs, and even some government agencies saw it as their role to stop development altogether. Or at least to dominate the environmental management of the coastal zone.

This tension came to a head when English Nature (now called Natural England) tried to introduce Schemes of Management for the Special Areas of Conservation. These applied to many of the estuaries where ports were located, and in ABP we were affected by 7 of them (Humber, Wash, Essex Rivers,Solent, Severn, Morecambe Bay,Solway). As I had to attend all the discussions on all of them, I was probably the only person outside English Nature and some major NGOs who had an overview. The crunch came when a ‘manager’ or ‘coordinator’ was appointed in each estuary to ‘run’ the scheme. We were pressed to “sign up to” an agreed plan. I was not against a plan as such, and indeed initiated the development of the Solent Plan (named Solent European Management Scheme), but I pointed out that, as statutory bodies,the ports (and many others affected by the SAC designations) could not share their statutory duties and responsibilities. When I suggested that signing the the plan might imply that all the signatories shared all the liabilities that the Scheme of Management placed on what were called the Relevant Authorities, pressure to ‘sign up to’ a scheme waned. In practice the Schemes of management have been a useful forum for sharing information and working out what management actions were appropriate, and which Relevant Authority should take action.These plans are not statutory, but rely on the existing statutory bodies that participate in the plan process.

I became quite sceptical about the Environment Industry that was emerging. Were decisions really being made for environmental gain? Or were they being taken to enhance the status of NGOs and government agencies? Yes some environmental legislation was needed but the desire by some in the NGO community to regulate, ban and prosecute was excessive. [And with hindsight it is interesting how many key people in some of the major NGOs have moved into pensionable government agency posts]. There is a discussion about this problem on the “Eco-Bureacracy” tab of my website

In my defence, I spoke to a senior Civil Servant in DoE (now DEFRA) when he was promoted elsewhere to say that even though we had crossed swords on occasion I had appreciated the thoroughness and clarity with which he had set out his proposals. (to which, in true Sir Humphrey mode, he replied “Oh Dear! Did I get it that badly wrong?!”). His reply was that although I had often challenged their proposals, I always offered an alternative and made them think. (Among other things, I had given a 100 page response to a 250 page consultation document on the Marine Bill that led to several changes making the Bill more practical. Only eco-nerds would tackle such a task)

As we approached the end of the 1990s, IPCC were consolidating their views on the existence of Climate Change and that the probable cause was Carbon Dioxide emissions from human activities. It was pretty clear that even then, a considerable amount of climate change, including some sea level rise, had already been built into the system, though the science at that time was indicative rather than proven. As the heads of NOAA and the UK Met office said in a joint statement “While the evidence is incomplete, all the indicators are pointing in the same direction”.

I recall putting a question at an environment conference in London to Dame Barbara Young (former head of RSPB and at that time head of the Environment Agency). “Why” I asked “was government paying no attention to adaptation to inevitable climate change. and simply concentrating on mitigation measures to slow down the climate change drivers?”. Her answer was direct, simple and startling. “If we started talking about adaptation, all the NGOs would cry ‘foul’ . We simply cannot do it right now”.

#3.2 Map showing possible polar routes

In 2001, I retired. But my final act in ABP was to do a presentation to the ABP board. Among many other things, I suggested that when ABP had built Dibden Bay (I was convinced that they would be given approval), their next container terminal should be at Stavanger (there are no unused estuaries on the east coast of England that are deep enough) This was because the polar ice would, I thought, be sufficiently melted for the much shorter passage from the Far East across north Russia to be available, possibly within 20 years. Many ships from the Far East would arrive from the north! I also suggested that if the extreme forecasts for sea level rise came to pass, then beach huts at Nottingham would be a good idea. I suspect they thought I was going demob happy. But look at the current reality 20 years later! I was not far wrong. (See this article on the Marine Traffic web blog: )

What a pity we have wasted those 20 years.

As I retired, I published my thoughts on the environment industry on my website. On several occasions, I have reviewed it, and there is very little that in my view has changed. This can be seen at:

That brings us to the start of the 21st century…..

A good background is the Wikipedia entry on the United Nations Framework Convention on Climate Change

“If everybody does a little, we will achieve a little. The issues raised by Climate change are on a country sized scale. Only country sized solutions will have a significant effect” That is only a slight paraphrase of the wise words of the late David Mackay.(For more on David Mackay, visit Environment on my website and select  “Climate Change“)

While many broad principles had been set out at the Rio conference in 1992, progress on reaching international agreement on actions was painfully slow. By 1997 in Kyoto, a baseline was established with commitments to reduce production of greenhouse gases. It was a major achievement but it had some flaws. For example, claims by the UK government that emissions have been reduced in line with commitments ignore the fact that globalisation has meant that emissions from many UK industries (for example steel) have been exported to emerging nations. No meaningful carbon tax has yet emerged. Worse, the Kyoto ratification process is so complex that the protocol did not formally come into effect till 2005.

Fundamentally, Kyoto did not include much reference to international industries such as aviation or shipping. However, the International Maritime Organisation, which is an arm of the United Nations, was asked to consider the issues. The problem with IMO is that voting is related to the ship tonnage registered in each country. Some decisions have to be unanimous. That means that flag of convenience countries such as Liberia and Panama massively outvote traditional maritime nations. Progress happens at a snails pace. For example it has probably taken 25 years to achieve a ban on polluting heavy fuel oil used in some ships, and that agreement is very porous due to numerous exceptions. It took nearly as long to agree standards for connecting ships to shore power, a practice much demanded by environmentalists and which is beginning to happen in the UK (e.g at the new Southampton Cruise terminal).

So Kyoto was a limited success, but it was clear more was needed. December 2015 saw the Paris climate conference at which specific targets were offered by individual states. Mechanisms were also set up to assist developing countries to proceed directly to a low carbon economy. Fortunately the withdrawal of the USA from the Paris agreement was temporary and corrected when Donald Trump was not re-elected. But the fact remains that, especially in USA, there is a strong and powerful lobby group of climate change deniers.

There are also those that agree that Climate is changing, but question the conclusion that the cause is human generated CO2. My oldest son is in this group. He points out that water vapour is in some ways a more powerful greenhouse gas, and leans towards the view expressed by some serious scientists (and some charlatans) that solar variation is the principle cause. My own view is that these two factors are not mutually exclusive, but you are unlikely to get research funding unless you subscribe to the human CO2 explanation. I am content to rely on the bulk of scientific thinking, but I think that it would be wise to allow some people to explore other possibilities provided their results are peer reviewed. But even within this divided world, all agree that the things that cause pollution are bad, and addressing pollution issues responds well to either view of the causes of climate change.

More frequent climate related crises since 2015 including massive forest fires in Australia, parts of Europe, and West Coast USA, more frequent hurricanes in the Atlantic, floods and drought on several continents, have raised awareness that climate change is not a distant threat but a current reality. The mood is right for change. “Tipping points” where climate change could race away uncontrollably are closer than we care to think about too much.

#5.1 Snapshot of worldwide ships at sea

So what could shipping contribute to the whole?

Despite the horrific appearance of the Marine Traffic plot of worldwide shipping, maritime transport emits around 940 million tonnes of CO2 annually and is responsible for about 2.5% of global greenhouse gas (GHG) emissions (3rd IMO GHG study). So cleaning up shipping is not going to solve the climate change issue. However this would appear to ignore emissions from fishing vessels, harbour support craft, warships, and the leisure sector. Also recently there has been more understanding of the adverse impact of particulate emissions from diesel fuels.

In recent times there has been a realisation that the particulate emissions from diesel engines are harmful to health and the general well-being of people and animals. Considering that Southampton Water supports cruise ships, container ships, tankers, tugs, ferries, dredgers and general cargo ships (as well as a large leisure fleet), it is not surprising that it is one of the worst towns in England for air pollution issues. So determination to tackle the air pollution problem will also make a contribution to reducing GHG emissions.

So, in the next section we can start to look the Marine Traffic plot in more detail.

When Automatic Identification of Ships (AIS) was almost universally adopted, the University of Athens seized the initiative and created the Marine Traffic website. In the early days, it relied on vhf signals from the ships to local shore stations, frequently run by national coastguards. It proved so valuable that many, if not most shipowners extended the system to include satellite tracking. Marine Traffic. Com was able to keep up and their website is now a widely used worldwide resource. (see figure #5.1 in previous section)

By zooming out to show the whole world, the extent of shipping activity can be seen. The main trade routes are obvious. One can even see a few ships transiting the newly opened route from the Far East to the Atlantic via the coast of Russia. But there remain a few questions.

It is clear that Marine Traffic are using many satellite sources, but are there any major gaps? For example, the apparent lack of reporting of vessel movements from inland China (i.e. the Yangtse River); or from Central Europe (Lower Danube) makes one question how many ships are being missed in those regions. (By contrast the Great Lakes, the Amazon -up to Manaus, and Mississippi all show heavy traffic) . What is the extent of tracking of vessels operated by Russia and China? Many smaller vessels including some fishing vessels and many leisure vessels are not equipped with AIS equipment. So we can be fairly sure that the total traffic is being underestimated.

Even efficient shipping operations can spend up to a quarter of their time in port, so port generated emissions are significant.

To further confuse analysis, the Covid 19 pandemic has seriously impacted world trade. Energy demand was thought to have been significantly reduced; and crew rotation has become extremely difficult.

Counter intuitively, freight volumes have been very high. As Mike Garratt, Chairman of MDS Transmodal (probably the leading company analysing freight trades) , commented:
“Q4 2020 saw the largest ever quarterly volume of container traffic globally while annual volumes almost reached. 2019 levels despite the pandemic, carried on a fleet capacity that had hardly changed. Demand growth was at its strongest on the East-West routes linking Far East manufacturers with consumers in North America and Europe.
As a mathematical consequence Q4 utilization levels hit record levels, with the apparent consequence of deteriorating service reliability, more port calls missed and rapidly rising freight rates. The impact on connectivity and emissions was broadly neutral.”

[The Container Shipping Market Quarterly Review for Quarter 4  2020 produced by MDS Transmodal may be downloaded from:  ]

What has been revealed is the fragility of long supply chains vulnerable to problems like difficult crew rotation in response to COVID 19 and unforeseeable events such as the stranding of the “Ever Given” container ship in the Suez Canal. Such situations are bound to cause some rethinking with possible long term consequences.

So there may be opportunities to reduce the total amount of shipping required, but there are also opportunities for generic reduction in GHG producing fuel burn per tonne mile, which we will consider in the next section before considering the threats and opportunities associated with each specific trade type.

There are several ways in which the amount of GHG emissions per tonne mile can be reduced without affecting fuel, including

Slow steaming
Theoretical maximum (non planing) speed of a hull is determined by the interference between the wave systems generated by the bow and stern of the hull. This is given roughly by Vmax(kts) = √2 xwaterline (ft). Beyond that speed, fuel burn rises exponentially until the hull starts to plane across the surface (which only smaller lighter vessels can achieve). Even below Vmax, the fuel burn rises at a greater rate than speed. So slow steaming will almost always save fuel burn per tonne mile.

A corollary is that slow steaming does not eliminate fuel burn, so will never achieve a zero carbon solution, which has to be our objective.

Slow steaming is not zero cost because there are many fixed costs in operating a ship, but it is an immediately available way of reducing GHG emissions until better solutions can be implemented.

Slow steaming has been adopted by shipowners during periods of low shipping demand such as the financial crisis of 2008.

Reducing ship drag (friction, windage)
Speeds are generally too low to justify the greatly increased shipbuilding costs of producing above water shapes that would reduce wind drag.

During the last 100 years the principal method for producing a smooth, low friction hull has been the application of paint coatings. For much of the 20th century the principle biocide used to reduce the amount of marine growth on a hull was lead, which produces a soft antifouling that had to be applied close to launch time and which quickly eroded or was pulled off by the marine growth. Lead is a dangerously toxic substance for humans. Then various chemicals were tried including TBT. This worked well but led to build up of toxic deposits in the seabed. As usual, IMO reacted very slowly and it was not till 2008 that a ban on TBT was finally implemented.

Since 2008 antifouling paints containing copper (and other poisons) have filled the gap. But in certain hotspots, copper levels have exceeded accepted limits. Although it is small scale, levels of copper in the Hamble river (where there are many yachts moored) have become a problem. Also zinc from anodes that protect propellers and other metals below water have exceeded limits originally set by the EU.

Current thinking is moving away from paint like coatings to surfaces which are so shiny that marine growth cannot attach itself. These include vinyl like plastics that are “ironed” on to the hull surface. It is claimed that these can be repaired or removed relatively easily, but there must be a risk of adding to the plastics burden in the oceans. Some ceramic type surfaces have been developed, but I have no information on these.

Yet another approach is the use of ultrasonics.. This appears to have some success, The electricity demand is very very small and there seem to be few downsides. However, it probably needs to be combined with one of the newer antifouling systems above to be fully effective.

At the turn of the century the pressure on shipowners was to reduce pollution. Acid rain caused by sulphur emissions from power stations had been brought under control through legislation, but shipping was slower to react. The IMO ban on heavy fuels only came into effect in 2011.

Even in 2013, a very thorough report from International Energy Agency concentrated almost exclusively on pollution reduction, and one of the conclusions reads “Natural gas stored as LNG is definitely a viable alternative propulsion fuel for ships and has been demonstrated many times in vessels on fixed and coastal trade routes and is continuing to appear in newbuilds that will be using LNG fuel systems and gas engines. Development of a global LNG bunkering system is critical to the expansion of use of this fuel to the larger ship sizes that travel on international routes……..The use of LNG as a marine fuel is projected to grow to 15 MT a year by 2020 to a possible 66 million tonnes in 2025″.

LNG fuel is now (2021) beginning to appear, for example on the new P&O cruise ship Iona.

But the plain fact is that even LNG will not get close to a zero GHG emissions target by 2050. The bar has been raised, and the shipping industry is rushing to catch up – or is it?  There is only one passing reference in the IEA report to climate change, and the only reference to ammonia is as an intermediate in the production of hydrogen derivatives.

It is however, truly amazing how thinking has moved on rapidly since 2013.

A major step forward was taken in 2016 (i.e before the Brexit vote) when the Marine Industry Decarbonisation Council (MIDC) was formed in Belgium. Its membership has a strongly European flavour and the absence of any significant British interest is noticeable (although some UK universities and companies such as Rolls Royce have participated in some projects). The organisation claims to be a think tank which is “ a-political, commercially independent and most importantly evidence-led”.

The declared vision of MIDC is “…to bridge the gap between shipowners, charterers, shippers, engine makers, ship builders, fuel producers, the research community, banks and classification societies to ensure the development of an evidence-based policy on GHGs that will enable the sector to reduce its GHG emissions in the most cost-effective way.”

An undated general MIDC report is available at .

#5.2 MIDC projection for Marine GHG Reduction

It is perhaps disappointing, but probably realistic that MIDC has an expectation of 50% reduction in GHG emissions from ships by 2050,with zero emissions by that date being a target “if possible”

On the same MIDC web page, there is a link to MIDC Downloads, where there are several very interesting reports. Of particular interest for our purposes is the Joules report (Joint-Operation-for-Ultra-Low-Emission-Shipping). It introduces the concept of Global Warming Potential (GWP) which is defined as “The Global Warming Potential (GWP) in the context of the JOULES project is defined as combined climate impact by CO2 emissions and Methane Emissions taking into consideration contributions of emissions from Well to Tank (WTT) and Tank to Propeller (TTP). The climate impact refers to the 100 year horizon”


#5.3 Joules Report Case Studies

The report examines a series of case studies for different classes of ships and estimates the GWP for each ship class. Even the results for the next generation ships are still disappointing.


#5.4 Joules Report Case Study Results

Most ship classes would expect a reduction in GWP of the order 40%, with only special cases like river ferries reaching an 80% reduction.



#5.5 Joules Report Conclusions and recommendations

The recommendations at the end of this report are a bit of a plea for clarity, further research, and action.

This report will be referred to in several sections of this study.

Since the Joules report was published, some developments in fuel technology have occurred in areas that could not have been taken into account by the report. These could be regarded as Alternative Fuel Technologies.




A lot of research is taking place in this field. It clearly has attraction to owners of existing ships as they do not wish to face the capital cost of re-engining their ships – even if that is economically possible

#6.1 MIDC Marine BioFuels Overview

A number of fuels are under consideration. Including Bio diesel blend, Butanol (fermentation process), Producer gas, Dimethyl ether. Few if any of these solutions can totally replace diesel fuel without encountering other serious problems including production and distribution at scale.. Therefore, while they may contribute to transitional solutions, it is unlikely they can contribute to a zero carbon solution.

Theoretically, Hydrogen could be burned in diesel engines, but only at higher temperatures which would induce maintenance and other issues.

# 6.2 SailingOnSolarAmmoniaPluses

An interesting paper prepared by Ricardo Energy & Environment for the Environmental Defence Fund entitled “Sailing on Solar” reviews the benefits (and risks) of migrating the shipping sector to using ‘green ammonia’ as a fuel. It can be downloaded  from the EDF website

At first sight, the most practical way of delivering hydrogen into a diesel engine is by using ammonia (NH3), which is already produced on an industrial scale. If a carbon free method of producing ammonia can be developed at scale, then, ammonia may offer a way of getting close to a zero carbon solution, so it is considered separately.

If ammonia is to be given serious consideration as a proxy for hydrogen fuel, it is first necessary to verify that the manufacture of Ammonia does not generate GHG emissions.

#6.3  Hydrogen Options from Zero Carbon report

There are various ‘flavours’ of ammonia depending on how it is produced, a broad classification is given in a report for Ocean Conservancy by Ricardo Energy & Environment




 #6.4 Usual methods of ammonia production

The diagram, is taken from a Wikipedia page about Ammonia Production. From that page it is clear that some conventional processes have carbon dioxide as an unfortunate by-product.


#6.5 Recent methods of ammonia production

The same Wikipedia page discusses alternative sustainable sources of ammonia. It would appear that one, known as methane pyrolysis avoids the Carbon Dioxide problem by producing solid carbon as a by-product which can be used elsewhere or stored in landfill. Volume production is being evaluated in the BASF “methane pyrolysis at scale” pilot plant,the chemical engineering team at University of California – Santa Barbara and in such research laboratories as Karlsruhe Liquid-metal Laboratory (KALLA). Power for process heat consumed is only one seventh of the power consumed in the water electrolysis method for producing hydrogen. (For more information consult the Pyrolosis page in Wikipedia).On that basis, it is reasonable to proceed on the assumption that GHG free production of Ammonia at scale will be possible.

It seems Ammonia can be used as a direct fuel in existing diesel engines. Set out below is the summary of a paper presented in 2010 at a technical conference of the internal combustion division of the American Society of Mechanical Engineers. The paper was presented by Aaron J Reiter and Song-Charng Wong, and this is the abstract.

“ Ammonia combustion does not produce carbon dioxide and thus can be regarded as a carbon-free fuel. Ammonia was used as a fuel in a compression-ignition engine in this study. Vapor ammonia was introduced into the engine intake port, and diesel fuel was injected directly into the cylinder to initiate combustion. This dual-fuel approach was chosen because ammonia has a high resistance to autoignition. A liquid ammonia tank was used for fuel storage and a high pressure relief valve regulated the ammonia flow rate, and ignition was controlled by diesel fuel injection. Ammonia was used as an energy replacement for diesel fuel. The results showed that the peak engine torque could be achieved by using different combinations of diesel fuel and ammonia. During testing, a maximum energy replacement of 95% was measured. It should be noted that, if more ammonia is added, a higher than rated power can be achieved depending on engine load conditions. It was also shown that CO2 emissions were reduced monotonically for the same engine torque output as the amount of the ammonia in the fuel mixture increased. Additionally, burning ammonia in engines does not necessarily increase NOx emissions despite the fuel-bound nitrogen. Lower levels of NOx emissions were obtained as long as energy substitution by ammonia did not exceed 60%. This is thought to occur because of the lower combustion temperature of ammonia.”

So it would seem that ammonia could be a useful proxy for hydrogen. Assuming that no increase in NOx is permitted, and using the IMO estimate that shipping generates about 2.5% of GHG emissions, it would appear that the figure could be reduced to 0.6×2,5%=1.5% if all ships in the GHG study were to use ammonia. Could the remainder be resolved using carbon trading mechanisms?

As Hydrogen is an intermediate in most of the industrial processes to produce ammonia, it begs the question as to why we do not use pure hydrogen as the fuel.

As already noted, hydrogen burns at a higher temperature leading to maintenance and wear issues

Hydrogen is difficult to store. Its boiling point is -253 degrees C.

If the ship were involved in an accident involving serious hull damage (collision or stranding) the design should be such that a breach of the fuel tank(s) would be unlikely. In any event, loss of power (probable in such an accident) would mean that the low temperature could not be maintained. The hydrogen would have to be vented in a controlled way so as to avoid fire or explosion risk.

If hydrogen were to become a major fuel source, then there would need to be a significant distribution system by sea. The points made above would apply on a greater scale if an accident to a hydrogen ‘tanker’ occurred. Imagine the consequences if Amoco Cadiz (230,000 dwt), which was wrecked on a populated part of the North Brittany Coast, had been carrying hydrogen! A major cargo breach could have resulted in an explosion on a Beirut scale. Such risks could present serious challenges to the insurance industry that may have the result of lowering maximum ship size (as happened in the case of supertankers)

By contrast, the boiling point of ammonia is -33.6 degrees C, which makes ammonia much easier to manage than hydrogen, and pressurised containers are more practical than would be the case with pure hydrogen.

Whether ammonia or some other medium is used, it seems inevitable that some form of proxy for hydrogen will be used. The options then become

▪ Option A: burn ammonia (or another proxy) in existing (modified?) diesel engines and accept a (hopefully slight) reduction in GHG avoidance.
▪ Option B: Use a process to release pure hydrogen at point of use to be processed by Fuel Cell technology directly producing electricity to power an electric motor

An alternative technology to release hydrogen to be burned in a turbine as part of a turbo electric drive. This would mean replacing ship diesel engines.

It is improbable that option B could be retrofitted to existing vessels (mainly because of the special requirements of the fuel tanks), which means it would only be available at scale to new build ships. As the life of a ship is about 25-30 years, this would place the implementation of Option B beyond the required timeframe of 2050. Option A would seem to be the only deliverable way forward in the short term, but option B could be a more successful solution as the fleet is replaced. It would therefore seem that the timescales recommended by MIDC are realistic.

#7.1 Harmony of the Seas in Southampton

Reducing fuel burn in port is a minor area for GHG savings from shipping compared to the savings potentially available for ships at sea. But the emissions and noise produced by diesel generators has become a major issue with communities living near ports, including Southampton.

Two years ago there was a vigorous campaign to persuade the port management in Southampton to provide shore power to visiting ships to reduce pollution in the town and surrounding area. It was debated in several forums including a facebook page called “Southampton Climate Conversations”. I tried to point out the practical difficulties and at least one former port engineer argued that it was virtually impossible to do, and would never happen.

Shore power has been available to cruise ships in Miami USA and, I believe San Diego on the Pacific . However it has taken IMO a long time to establish suitable international standards. Issues include the wide variety of ship sizes and types; the fact that ships tend to use 110v 60hz electricity compared to the 240v 50hz supply common in Europe. Providing shore power is not like plugging in a toaster!

#7.2 Multiple cruise ships in Southampton (photo ABP)

Modern cruise ships are the size of a small town, so availability of supply becomes an issue, especially when, as in Southampton there can be as many as 5 or 6 large cruise ships in port at the same time. As it happens, Hampshire, the area surrounding Southampton, is a net energy importer, especially since the closure of the Marchwood and Fawley power stations. Furthermore, the commissioning of two new aircraft carriers based in Portsmouth has added greatly to the demand. Indeed, those 2 ships made it necessary to add a new connection to the National Grid. Supply has been slightly increased as a new interconnector from France enters the country at Lee on Solent.

Despite all these obstacles ABP is now providing shore connection at the new cruise terminal opened recently. It is far from clear how quickly they will be able to provide supply to the whole dock complex (including the other three cruise terminals, the container port, and numerous general berths). Shore Power should also be provided at the Hamble and Fawley tanker berths, and the the commercial berths in Portsmouth where cruise activity appears to be expanding.

In conclusion regarding general emissions from ships, it seems that while demand for shipping might be constrained, there will continue to be a significant requirement for cargo to be moved. There appears to be no form of propulsion that would result in zero GHG emissions. However, of the options examined, it would appear that the use of ammonia as a proxy for hydrogen offers the best possibility, within the time window available for reducing emissions to the level where any residual GHG emissions could be compensated by an effective carbon trading market.

The conclusion is dependent on 4 assumptions

▪ Current trials of the pyrolysis process (or a successful alternative) for delivering zero GHG emissions ammonia at scale are successful

▪ Procedures to manage the combustion of ammonia in a wide range of large diesel engines can be developed that allow a sufficiently high replacement of fuel by ammonia without unacceptable level of NOx pollution

▪ Development of a clear carbon tax and an effective international carbon trading market which will be required to ‘mop up’ the residual GHG emissions. Given this, there should be enough commercial pressures to provide the motivation for adaptation to the new requirements.

▪ Retrofitting the main propulsion machinery of commercial ships within the available time window is impractical..

The result could be accelerated or improved by

▪ Systems such as the SGS wingsail that reduce the fuel burn (accepting that this is route dependent)

▪ Development of improved antifouling systems that are non-polluting.

▪ Provision of shore power for ships in port.




In the 2018 Joules Studies (see section 5.5), there were two deep sea cargo case studies.

(a) Application Case Arctic Cargo Vessel
An existing container ship trading on Arctic routes was used as a baseline. Improvements realistically achievable by 2025 were examined. These resulted in a reduction in Global Warming Potential (GWP) of 21%.

#9.1 Joules Project Arctic Container Ship Case Study

A new design shown in diagram 9.1 was developed as a concept to be available by 2050. LNG was chosen as the fuel, coupled with other modifications, The result was a reduction in GWP of 56%. That perhaps is disappointing, but at the time of the Joules Studies, Hydrogen or Ammonia (or other very low carbon derivatives) were not considered as a fuel. Perhaps this result confirms the need to think about the extra mile toward zero carbon hydrogen based fuels.

The choice of an Arctic vessel is interesting. The mileage saving resulting from using this route is discussed later.

#9.2 Flettner rotor fitted to baseline cargo ship


(b)Application Case Wind Assisted Cargo Vessel
For the 2025 case, a conventional cargo vessel was chosen. After investigating a number of options the Flettner rotor was chosen for the case study. Diagram 9.2 shows it was proposed to be fitted on the bow. While this keeps the cargo working area clear, and avoids the strengthening costs associated with fitting the rotor abaft the bridge, there must be concerns about the potential for storm damage when placed in such an exposed part of the ship. Obliquely, the Joules results report acknowledges that the success of these devices is route sensitive depending on prevailing winds.

The 2025 modifed vessel achieved a GWP reduction of 28%.

#9.3 Joules Project 2050 Wind Assisted Cargo Ship

For the 2050 design, a total and very radical proposal was made. It is not clear how this complies with the need to keep cargo working areas clear. However, the resulting GWP reduction was a remarkable 82%.

Wind assistance therefore does seem to be worth pursuing, though its benefits will be very route specific. Where gains are made, it will help compensate for the significantly larger size of bunker fuel tanks needed when alternative fuels such as LNG or hydrogen derivatives are used. At present shipowners are said to be interested, but unwilling to invest in wind assistance until the concept is proven. This must be a strong candidate for a government supported pilot. We know from the Walker Wingsail that the concept works, with limitations (see section 2.2 above)

The wingsail concept is unlikely to work well on container ships because the side decks (where they could be mounted ) are narrow, and the containers are stacked above the upper deck. However, looking at the Arctic container ship (case (a ) above) shows the possibility that containers would be below decks on future designs. Interference with cargo operations will be difficult to avoid

Reducing fuel burn on bulk carriers by using wingsails could be attractive as the side decks are available for their installation. The savings however would be route sensitive as discussed earlier. For smaller ships on short sea routes (including estuaries and rivers) air draft considerations may prevent the use of wingsails unless stowing mechanisms are efficient.

#9.4 Marine Traffic Plot – Cargo Ships

The dominant forms of cargo ships in recent times are Container Ships and Bulk Carriers (Tankers are regarded as a class on their own), .

#9.5 Container Ship Emma Maersk

When I retired in 2001, the average container ship visiting Southampton was about 4000 teu (OneTrailer Equivalent Unit = a container 20x8x8 ft). There were a few 6000 teu ships and we were expecting vessels of 8000 teu with in months. In 2021 16-18000 teu vessels are not uncommon. Even bigger vessels occur mainly on the Trans Pacific routes. To give one specific example of a mid range vessel, Emma Maersk is powered by a Wärtsilä-Sulzer 14RTFLEX96-C engine, which at the time of build was the world’s largest single diesel unit, weighing 2,300 tonnes and capable of 81 MW (109,000 hp) when burning 14,000 litres (3,600 US gal) of heavy fuel oil per hour. At economical speed, fuel consumption is 1,660 gal/hour. This equates to about 200 long tons per day.

The engine on such a vessel rotates at about 100 rpm to get as close as possible to the most efficient propeller rpm which will be well below 100rpm. These engines are colossal and are frequently referred to as “cathedral” engines.

It is improbable that wingsails will be used on container ship as installation is difficult, because the side decks are very narrow, and containers are stowed well above the upper deck effectively obstructing the wind flow.

Bulk carriers have broadly similar propulsion systems, though ship sizes can be even larger.

The drive toward increasing ship size has been driven by the lower costs per tonne mile, including the fuel burn. The limit to ship size is largely constrained by available port facilities and the depth of approach channels. In most places the limit has been reached with only minor further increases being possible. Insurers are also reluctant to see too much value (of cargo and the ship itself), and pollution risk, in one ship (see the discussion on tankers).
So it seems little can be achieved by increasing ship sizes.

The widening and deepening of the Suez Canal has shortened the main route from Far East to Europe by one third of the distance. For example

  • Hamburg to Yokohama via Suez 11430 miles
  • Hamburg to Yokohama via Cape 14767 miles

Yet it is obvious from the Marine Traffic Plot (#9.4) that many vessels still use the Cape route. Some ships will have calls on the east or west coasts of Africa, or are heading for South America, and many bulk carriers will be too big for Suez.

The Panama Canal has also been widened and ships of just less than 20,000 teu have recently passed through. This is probably of less significance in terms of saving distance steamed.

#9.6 Proposed Kra Canal

Other canal opportunities include the Thai Canal, also known as Kra Canal or Kra Isthmus Canal, which refers to proposals for a canal that would connect the Gulf of Thailand with the Andaman Sea across the Kra Isthmus in southern Thailand. It is envisaged that such a canal would improve transportation in the region, similar to the Panama Canal and Suez Canal. The Kra Canal would relieve the pressure on the Malacca Straits which is one of the busiest waterways in the world The proposed canal is probably more important in terms of ship safety by reducing the congestion. However, it would undoubtedly save considerable miles for ships transiting from E Asia and Japan on routes through the Indian Ocean. The concept has been around for half a century but no secure means of funding the project has emerged.

#9.7 Arctic Routes  – source: The Times

The real prize in terms of mileage saving is the opening of the Arctic routes.



#9.8 Polar route comparisons from the Arctis Report

The tables from the Arctis Knowledge Hub show the mileage comparisons for routes across Canada (North West Route NWP) or across Russia (North East Route NEP) and (if it ever became available) the Trans Polar Passage (TPP) versus travelling via Suez

Already (in 2021) there are some cargo ships using the passage across Russia (see #9.4)

Major companies such as Maersk are watching the situation carefully, but are not quite ready to commit to regular use of such routes (which may not be available year round for some years yet). Many of the larger container ships built in recent years have had ice strengthening added in anticipation of this route opening up. There are political considerations with NATO countries, in particular, having serious concerns about a major world trade route being under the control of Russia. It seems however, that the alternative North West Passage across Canada is longer and in navigation terms more intricate than the North East Passage. Environmentalists may also have serious concerns about the possible risks to the fragile Arctic ecology in the event of a marine accident. This is going to be a serious and ongoing debate, but it has to be concluded soon if use of this route is going to contribute to massively reduced emissions by mid century.

Renewable energy for ships is difficult to deliver, so the alternative of transfer to rail could be considered. But according to Wikipedia, “All rail freight from China across the Eurasian Land Bridge must pass north of the Caspian Sea through Russia at some point. A proposed alternative would pass through Turkey and Bulgaria but any route south of the Caspian Sea must pass through Iran.On 7 November 2019 the first Chinese freight train through the Marmaray tunnel to Europe ran, from Xi’an using a Chinese locomotive. This demonstrated a China to Turkey transportation time reduced from a month to 12 days, and is part of the Iron Silk Road.

The Iron Silk Road development is fraught with technical issues such as gauge changes and is likely to suffer from much political posturing.

It is also worth pointing out that average capacity of a container train worldwide, is 66 20 ft containers. So to move the capacity of a ship like Ever Given (capacity about 20000 teu) would require 300 trains. Ships are very good at moving very large volumes!

Similar considerations apply to bulk carriers the largest of which which can carry upwards of 200,000 tonnes.

The two primary bulk cargoes are coal and iron ore. In an ideal low carbon world, the coal trade would disappear. Data from Statista suggests that we are looking at about 1,2 billion tonnes of coal shipment per year. Iron ore shipments were about 1,3 million tonnes

#9.9 Iron Ore trade – source Open.Pro blog

Much of the coal usage worldwide is for electricity generation. Can we create enough renewable or nuclear alternatives to completely eliminate coal from the mix? Lets hope so.

It is, however, difficult to believe we can achieve a world without steel in the time frames available.The alternative to coal in steel production seems to be Hydrogen which some say is the new coal.The alternative is to get rid of the blast furnace and electrify steel production, most prominently through using green hydrogen, produced from water with renewable electricity. That sounds like a formidable challenge!

I have not found statistics for the movement of timber by sea, but it must be a considerable tonnage. That makes it difficult to unravel a complex picture. For example the Drax power station in Yorkshire has been converted from coal (hurrah!) to burning wood chip imported in bulk carriers from America (what?!). I find it hard to believe that that operation is genuinely sustainable and carbon neutral.

Damage to carbon sequestration by burning rain forests or logging for hardwood and/or deforestation for palm oil plantations, or beef production ought to be reduced, and that should reduce the volume of timber shipped. On the other hand, increased use of sustainable timber for housing helps reduce GHG emissions if it substitutes for bricks and cement, both of which can be large GHG emitters. Add to that mix the arguments over biodiversity protection and it is clear that the timber industry will be the subject of intense debate. Shipping can only respond to the outcome of those arguments.

One of the largest GHG emitting industries is cement. According to Carbon Brief, “If the cement industry were a country, it would be the third largest emitter in the world.In 2015, it generated around 2.8bn tonnes of CO2, equivalent to 8% of the global total – a greater share than any country other than China or the US.” However most of the GHG emissions are from the manufacturing process, or from the heat required in the kilns. Only 10% (approx) of the GHG emissions generated by the cement industry arise from mining and transport. Therefore Shipping is unable to address that problem.

Much of the foregoing is concerned with ocean shipping, but it is common for there to be a short sea, or inland waterway sector for the distribution of cargoes to the hinterland or the broader region. Feeder container ships fall into this category. Special factors relating to short sea trades are discussed later.




The technical developments that apply to Cargo Ships, in the main, also apply to tankers.

It is possible that wingsails could more easily be fitted to tankers because there is no need for top access as there is to the holds of cargo ships. However, the low freeboard may make the devices more vulnerable to storm damage.

The location of oil deposits and areas of demand make it unlikely that tankers will use the Arctic route. Where large tankers are still used, they may still have to proceed via the Cape from the Middle East to the Atlantic seabord countries.

Tanker traffic is generated in 2 principal phases

▪ Phase 1: Movement of crude oil from source (whether on- or off-shore) to a refinery
▪ Phase 2: Distribution of refined product.

#Fig 10.1 Petroleum Products consumption by source and sector USA 2020 source USEIA 

The diagram from the US Energy Information Administration indicates (for the US) that even if oil is eliminated from the transport sector, a proportion of the remaining 34% will still be needed for materials like lubricants,and petrochemical feed stocks for materials such as essential durable plastics and many other industrial chemicals .

While a major reduction in oil movements can be expected, there is likely to be a need to transport the raw material and product for the fuel substitute, probably methane to feed the manufacture of ammonia, and hydrogen itself. Transport of pure hydrogen would appear to be unlikely on safety grounds.

#10.2 MarineTraffic Tanker Plot

From the Marine Traffic Plot, it can be seen that tankers tend to be more sharply focused on main trading routes compared to other cargo types.

Many of the factors that applied to cargo ships (see above) also apply to tankers, but the following constraints apply

Scope for mileage saving for tankers is more limited because major oil sources are not well located for using the Polar route, and environmental pressure to restrict use of the Arctic route by tankers may prove to be strong.

The economics of VLCCs (Very Large Crude Carriers) going via the Cape versus Suez max vessels are difficult to predict and depend on the shift in cargo type and route.

There are however some major differences that will affect both the amount and distribution of tanker traffic.

Assuming that the demand for hydrogen (or its proxy, ammonia) will grow to meet the need for marine fuel and for use in steel production, there will be greatly increased demand for methane, which will continue to be the principal feedstock for ammonia/hydrogen production unless and until some other processes are brought to industrial scale. This may open up opportunities for new sources to be exploited, such as North Africa, Indonesia.This could change the balance of ship sizes, and hence the proportion of tankers using of Suez.

If there is an increase in the use of hydrogen derivatives in deep sea diesels, ammonia may need to be redistributed from where it is currently manufactured to where it will be needed to refuel ships. Capacity could increase where naturally occurring methane feedstock (natural gas) is available.. Countries with opportunities for plentiful solar power may be able to economically generate hydrogen by electrolysis. Ricardo Engineerring, for example, have done studies on producing ammonia based on solar produced hydrogen in Morocco and South America

Ammonia plants for the production of fertiliser are widely distributed., But support may be needed to expand capacity to meet the new demands.

Oil and gas are well suited to transport by pipeline provided that politically secure routes can be found. (damage to pipelines in Southern Nigeria is an example of political risk).

So The future of tanker trades is that

▪ the amount of crude and refined oil carried will reduce, but will not disappear because of the need for oil as feedstock for essential chemicals, many of of which will generate only a small amount of GHG.
▪ The substitutes for oil, possibly hydrogen derivatives, will generate replacement traffic at a scale which is difficult to determine at present.
▪ The replacement tanker trades may not be suitable for the existing stock of vessels, because of the need to maintain specific temperatures and/or pressures. So the rate of transition to low carbon fuels in the shipping industry could be dictated by the rate at which the replacement vessels can be built, or converted from existing vessel stock. This will apply to the short sea distribution routes as well as the main deep sea routes. These aspects are reviewed in the section on short sea trades.

Tankers may be suitable for the installation of wingsails on certain routes, but in addition to wind direction and strength, the risk of storm damage may need to be considered on some deep sea routes, e.g. the Cape. Despite that, reduced fuel burn created by wingsails would be a useful offset for the need to increase the volume of fuel tanks because the energy density of most subsitute fuels is less that that for oil.





#11.1 Joules Project Concept Passenger Cruise Ship

(a ) Joules Project Application Case Ocean Cruise Ship

This French contribution to the Joules Project is typically very academic. It has the advantage that it seeks to set out all the energy reduction options, and model them together. It looks as though the individual designs were not taken beyond the broad concept stage.

#11.2 Joules Project Concept Wind Assisted Cruise Ship

The results, however, are encouraging. If the concepts were applied then it was expected that by 2025, a reduction in Global Warming Potential (GWP) of 49% would be achievable with a 90% reduction in pollution. By 2050,Improvements are expected to be supported and developed: fuel cells, sails, energy recovery, efficiency, etc; so the GWP reduction might achieve 70% with total elimination of pollution. While these results may be aspirational, they still fall short of what may be needed to approach a true zero carbon ship.

#11.3 Joules Project Potential GWP savings areas

Since the Joules study was completed there have been major advances in fuel cell technology, and the possibility of using hydrogen derivatives such as Ammonia has increased. Cruise chipping is a luxury product, so it will have to get close to these targets to remain an acceptable trade. In 2021 we saw new LPG cruise ships appearing (see Below)

#11.4 Joules Project Ropax vessel

(b) Application Case RoPax Ferry

In the short term, The Joules report suggests reductions in Global Warming Potential (GWP) by 2025 of 18% by using a blend of MDO and Biomass-to-liquid fuel. In the longer term to 2050, improvements in fuel cell technology and the introduction of renewable hydrogen based fuels could increase the GWP reduction to 90%.

This seems to be one of very few application cases in the Joules report that anticipated the need to progress beyond LPG type fuels.
This is an important class of ship.There are numerous examples of this ship type. Taken together they are said to account for 3.8% of GHG emissions from shipping according to the 3rd IMO GHG study 2014

#11.5 Marine Traffic Plot; Passenger Ships.

The Marine Traffic plot for passenger vessels reveals that there are no strong deep sea passenger routes. That traffic was lost to airlines in the second half of the last century. This implies that

▪ Deep sea passenger operations are cruise ships
▪ There are many short sea or inland ferry services that do not show up clearly on the Marine Traffic plot

Cruising is an optional activity, It is however very popular, and has been growing at a very fast rate over the last 20-25 years. When I retired in 2001 I think Southampton was looking at 250 cruise calls a year, by ships with a capacity of up to 2500 passengers. By 2019 this had risen to 500 cruise calls with ship capacity ranging from 1500 to 5000 (or more) passengers, with more of the latter. The cruise industry which has shown a compound growth rate approaching 7% pa over the last 20 years has been brought to a halt by the COVID 19 pandemic, and in the late summer of 2021 is only just starting to get going again. But the ships of the British based cruise fleet have been at anchor, with generators running, and with a need for regular port calls for crew changes and replenishment of fuel and stores. It remains to be seen how quickly market confidence is restored.

Doubts have been expressed about some of the impacts of the cruise industry on home ports and destinations.

Southampton is now the base port for a number of European cruise operations including Carnival, Cunard and P&O. On a busy weekend, there can be as many as 5 ships turning round, with an average passenger load of at least 2500 each ship. That is 12500 Pax disembarking and 12500 pax boarding. There is also a requirement to restock with food and drink, fuel, laundry, and goods for the on-board shops. The plus is that it generates a lot of jobs and income for the city, but the downside is that the city roads become jammed and generate a lot of pollution (in addition to the pollution produced by the ship generators, unless and until shore power is provided). Apart from services like cruise parking and perhaps taxis, the passengers do not contribute income to the local community. The port is privately owned.

Some years ago I was in Oban (Scotland) which had just started to be a cruise destination. I commented to the harbourmaster on how the cruise visits must be contributing to the port revenues. He was very negative. Apart from direct port charges to the ship, there was virtually no income. Passengers were ferried ashore in the ship’s own launches, clogging up the landing areas. Passengers went immediately on to coaches that took them to inland destinations (Castles, Gardens, Highland events) without any opportunity to spend in the town. It is said by some that the flood of cruise passengers to some Caribbean islands is overwhelming the local economy and in some cases is destroying the asset that people have come to see.

An extreme viewpoint would be to regard the cruise industry as “unnecessary”. Like some of the more ardent environmentalists there would howls to Ban, Regulate, and Fine the industry.. That would be a hair shirt solution and is unacceptable.So incentives are required to migrate the cruise industry to zero carbon solutions.

The overburdening of destinations is a matter for each local administration to determine how many cruise calls it can accept, and perhaps a limit on number of passengers landed to avoid swamping local facilities.

With regard to fuel burn, based on an estimated total number of about 25.8 million cruise ship passengers in 2017, it can be estimated that the average cruise ship passenger emits 0.82 tonnes of carbon dioxide-equivalent for their cruise. (Source

Many new cruise ships are being powered by LNG which brings about one third reduction in GHG emissions, and even better reductions in sulphur and Nox emissions.

Taken from the CruiseCritics website in summer 2021, here is a list of some cruise vessels relying on LNG.

AIDAnova (2018)
AIDAcosma (2021)
AIDA unnamed (2023)
Carnival LNG Ships
Mardi Gras (2020)
Carnival unnamed (2022)
Costa Cruises LNG Ships
Costa Smeralda (2019)
Costa Toscana (2021)
Disney Cruise Line LNG Ships
Disney Wish (2021)
Disney unnamed (2022)
Disney unnamed (2023)
Princess Cruises LNG Ships
Princess unnamed (2023)
Princess unnamed (2025)
MSC Cruises LNG Ships
MSC Europa (2022)
MSC Meraviglia Class unnamed (2023)
MSC World Class unnamed (2024)
MSC World Class unnamed (2025)
MSC World Class unnamed (2027)
P&O Cruises LNG Ships
Iona (2020)
Royal Caribbean International LNG Ships
Royal Caribbean Icon Class unnamed (2022)
Royal Caribbean Icon Class unnamed (2024)
Royal Caribbean Icon Class unnamed (2025)
TUI Cruises LNG Ships
TUI unnamed (2024)
TUI unnamed (2026)


Note: Tankers will be required to move the LNG from the refineries to where the ships need to refuel.

While it is evident that the cruise industry has made major investments in reducing GHG emissions, LNG powered vessels will not achieve zero carbon, so the next generation of ships may need to go further. The use of ammonia as a fuel for passenger ships may be questionable as even small leaks would result in considerable odorous inconvenience to passengers. The industry seems confident it can cope with LNG fuel in this regard, so it may not be too serious an issue. However, in the medium term it may be the only practical solution until new fuel cell units are available. Even in the short term, fuel cells may replace generators. This would solve the problem of generator emissions and noise in ports where shore power connections are not available. .

Reduction in fuel burn by adding wingsails may be attractive on cruise ships as a marketing ploy, as well as saving fuel. However, the upper decks of cruise ships are, of necessity, lightly built and strengthening the structure to take the wind thrust may prove to be expensive. Smaller, specialist cruise ships may benefit proportionately more from use of wingsails. But, in certain cruise areas, considerations of air draft may be an issue. Also, in all cases, the open upper deck of a cruise ship is a popular passenger space. This may lead to reluctance by designers and marketing teams to include wingsails in the design

The cruise industry is a luxury product, but it would reduce human wellbeing if it was phased out. It is already taking steps to reduce GHG emissions, but may need to go further with the next generation of ships.

In addition to cruise ships, there are numerous ferries. At the larger end are the short sea vessels (including the RoPax example included in section 11.2) ranging from seagoing vessels seen in the North Sea, Irish Sea, Cook Strait (NZ), British Columbia (Canada), Scandinavian, Baltic and Norwegian routes, Inter-island (e.g. Balearics, Aegean, Philippines and Indonesia), Trans Mediterranean. Smaller vessels are usually used on routes of less than 40-50 miles and on inland waterways.

Smaller very short sea, urban and inland waterways vessels are considered in section 12.2.




Click here to go to Zero Carbon Ships 2