Synthetic fuels could be the answer to shipping’s net-zero goals, but don’t count on them yet

Here’s the dilemma: shipping accounts for 90% of goods transported around the world, and it’s also the most energy-efficient mode of international freight transport. But it’s also a major source of global greenhouse gas emissions. Greener alternatives are often viewed as prohibitively expensive in a highly competitive market. And change is often desperately slow.

Today, international shipping accounts for 681 million tons of CO₂ every year. While the sector is improving in terms of energy efficiency, emissions are likely to stay at about 600 megatons as seaborne trade is expected to grow by 15% by 2030. So, we’re going to look at the business case of synthetic shipping fuel as a technology fix to reduce carbon emissions. We’ll assess where we are right now and the pressures companies are under to meet net-zero targets. And we’ll examine which alternative fuels could be front-running technology as science improves and adapts.

It’s worth adding that we’re working with the consensus view of expected demand for shipping against the current policy backdrop.

Shipping is a ‘hard-to-abate’ sector. That's where it's prohibitively costly, or the technology's just not there yet to meaningfully reduce harmful emissions. For instance, the full electrification of maritime shipping is not a feasible strategy, given the technological limitations. So any transition pathways are gradual and long. And the international nature of maritime shipping doesn't help much. You can argue that any policy intervention should be globally aligned and implemented by the global authority, the International Maritime Organization (IMO).

Unfortunately, the IMO is not exactly a fast-moving beast. It's still targeting a 50% reduction in CO₂ for shipping by 2050 from a 2008 base rather than from 1990, where the Paris Agreement looks at. That's far away from both the 2015 agreement and the net-zero target for the global economy.

On the other hand, it is encouraging to see some large container liners such as Maersk, MSC, and Hapag Lloyd are already committing themselves to net zero emissions by 2050.

Given these technical and policy limitations, there are three main strategies to reduce emissions:

1. Tempering the demand for shipping, which basically means reducing growth in international trade. For example, through nearshoring and the transition towards a circular economy which aims to lengthen the life cycle and duration of consumer goods and to recycle goods locally.
2. Improving the efficiency of current bunker fuel engines and vessels
3. Apply a technology fix by replacing fossil fuels with biobased and synthetic fuels

We absolutely underscore the importance of demand reduction in sector pathways towards a net zero economy, in particular in hard-to-abate sectors like shipping and aviation. But we also realise that it is not the most likely route given the consensus view for growth in maritime shipping, which is linked to global GDP and population growth.

Furthermore, efficiency improvements in practice tend to stop the growth in emissions but do not reduce emissions in a way that sets the sector on a net zero pathway.

Lastly, the supply of biobased fuels is likely to be limited given the vast amount of shipping fuel that needs to be replaced and the fact that net-zero pathways for other sectors rely on biofuels too (such as aviation, road transport and the chemical sector).

We believe that synthetic fuels are likely to be a crucial ingredient of the transition pathway of maritime shipping towards a net-zero economy. And we're going to explain why.

Today, outside the emission control areas, VLSFO (Very Low Sulpher Fuel Oil) and HFO (Heavy Fuel Oil), in combination with an installed scrubber, are the main fuels used by large marine vessels. HFO is the remnant from the distillation and cracking process of crude oil. It contains compounds such as sulfur and nitrogen. The use of HFO, therefore, has several environmental impacts. Besides being a large emitter of CO₂, it also emits polluting compounds such as sulfur and black carbon. So, you have the policy dilemma of trying to decide which pollution to reduce.

We focus on the Paris Agreement's goal to limit global warming to 1.5 degrees Celsius. Since limiting global warming is all about reducing the level of global carbon emissions, the shipping industry also needs to decarbonise. This calls for the transition to synthetic fuels that emit no or little CO₂ from well to wake.

Apart from HFO, there are other oil-based fuels ships use. They include Marine Gasoil (MGO), Very Low Sulphur Fuel Oil (VLSFO) or Ultra Low Sulphur Fuel Oil (ULSFO, which are obligatory in emission control areas like the North and Baltic Seas). Liquid Natural Gas (LNG) is an emerging fuel, which is an alternative and ‘cleaner’ fuel compared to oil-based fuels, but it's still a fossil fuel that emits CO₂.

Many new ships being built today are being designed to be highly energy efficient, and IMO regulations are playing their part here. Many vessels are also making the switch to operate on LNG to reduce emissions. But it's not a permanent solution and is seen more as an intermediate step towards full decarbonisation of the shipping industry.

This is where synthetic fuels come into play. Synthetic fuels are made in a chemical plant through a chemical process rather than being mined from the earth and refined. Ideally, this production process wouldn't involve fossil fuels (the green route).

In this article, we are going to shed light on the production costs of synthetic fuels (well-to-tank cost) and the use case of synthetic fuels in shipping (tank-to-wake costs). Given the current state of technology, methanol, ammonia and hydrogen are considered relevant synthetic fuels in shipping. The table at the end of this article describes these fuels.

Remember, these fuels are not just theoretical concepts. In the past six months, there has been a range of orders for methanol-capable and methanol-ready vessels in container shipping. These are dual-fuel vessels, able to switch to green methanol after a future retrofit. Maersk, for example, has 19 such vessels on order.

When traditional fossil-based marine fuel is burnt in the engine of a ship, carbon atoms (C) react with the oxygen in the air (O₂), which delivers energy and creates CO₂. This option is often seen as the ‘black' or 'dirty' technology’ that increases carbon emissions and contributes to global warming. As an indication, oil-based fuels emit 3.5 to 3.7 kilograms of CO₂ per dead weight tonnage per kilometre. A similar ship on Liquified Natural Gas saves about 30% of carbon emissions but still emits 2.7 kilograms of CO₂ per kilometre.

The magic of synthetic fuels is that carbon emissions from ships can be drastically reduced or even nullified in the case of hydrogen-propelled vessels or ships that run on ammonia. And that's especially true when the hydrogen needed to produce ammonia is produced with electrolysers that fully run on renewable power (the darkest green hydrogen).

Methanol is made from syngas, which is a mixture of hydrogen and carbon monoxide and thus still contains carbon atoms (see the appendix table at the end of this article). Ships that run on methanol still emit CO₂. Our calculations indicate that emissions are reduced by about 20% compared to oil-based fuels if the methanol is fully green (that's to say, it's produced with green hydrogen and 100% renewable power). When the methanol is produced with blue hydrogen, the vessel emits about 13% less CO₂ on a net basis.

Synthetic fuels must be produced in a sustainable way

Note too that LNG emits less than green and blue methanol, but the standard view is that natural gas – and hence fossil-based LNG - should be phased out in a net-zero economy and therefore is a ‘transition fuel’. That should equally apply to methanol as it emits more carbon emissions than fossil-based LNG. In the future, synthetically produced LNG (also called E-LNG) could be part of the fuel mix in shipping, but we'll be looking at that another day.

Finally, note that grey ammonia and grey methanol are actually much more polluting than fossil-based marine fuels. The production of synthetic fuels is bound by physical laws that imply high energy losses. As a result, the climate impact of synthetic fuels is worse compared to fossil fuels unless they are produced in a more sustainable way (that is, with blue or green hydrogen instead of grey). It's fair to say that the shipping sector can actually make things worse if it uses synthetic fuels in a non-sustainable way.

So, it is clear by now that synthetic fuels can radically 'green' the hard-to-abate shipping sector and put it on a pathway to net-zero emissions. The necessary condition is that the required hydrogen is produced with few carbon emissions, so with blue or green hydrogen.

The obvious questions then are, why hasn’t it already happened? And why aren’t we using synthetic fuels in ships already?

The answer is pretty simple. The technology is still in its infancy, and the production process is very energy intensive compared to conventional fuel, even with mature technology. Therefore, production costs of synthetic fuel are much higher. Currently, the green options increase fuel costs by 4 to 9 times compared to fossil-based fuels, the blue options increase fuel costs by 2 to 5 times.

This price differential is very important for ‘dual fuel vessels’ that can run on synthetic fuels like methanol or ammonia and fossil fuels with minimum adjustments. For these ships, it remains an option to switch to burning fossil-based bunker fuel if it is not during a trip, then at least between trips.

There are two ways of looking at this large price difference:

One way is to say that synthetic fuels are currently too expensive. This can partly be solved with subsidies and innovation, as hydrogen production costs could come down. There are many studies out there that predict large cost declines for green hydrogen. But these only emerge if capital costs for electrolysers decline strongly, power prices reduce and carbon prices increase further. That’s not unthinkable, but also not yet a done deal. It might also be that clients are willing to pay a premium for green shipping, but it remains to be seen to what extent container shipping rates will be impacted.

It is almost impossible to predict the future competitiveness of synthetic fuels in shipping

One could also say that fossil-based fuels are currently too cheap and synthetic fuels are not in a ‘fair fight’. The EU Fit for 55 package starts to address this point by extending the EU Emissions Trading System (ETS) to maritime transport. This pricing of carbon emissions will narrow the cap between fossil fuels and synthetic fuels, in particular the green and blue ones. And the EU carbon border adjustment mechanism might trigger other regions in the world to tax carbon in shipping, too, so that they can use the tax revenues themselves instead of paying the carbon cost to Europe, for instance.

But the price of fossil fuels will also heavily depend on the pricing strategies of oil-producing countries. And we don't know how these countries will respond during the energy transition. Will they flood the market with oil in anticipation of lower oil demand, making it harder for synthetic fuels to compete with fossil fuels (the green paradox)? Or will they be able to keep prices high by reducing production in a coordinated way, which is needed to close the price gap with synthetic fuels?

Given these big uncertainties, it is almost impossible to predict the future competitiveness of synthetic fuels in shipping. And those routes which do exist shouldn't necessarily be relied on to guide as to what may happen many years from now. Shipping companies will be watching these developments closely and should be thinking in price scenarios rather than exact forecasts.

Synthetic fuels also pose a not-so-nice trade-off between fuel costs and freight revenues. While synthetic fuels could have a positive climate impact in terms of lower CO₂ emissions, they come with lower energy densities, especially on a volumetric basis.

The poor volumetric physics of synthetic fuels means that ships that run on them have to install bigger tanks to travel the same distance, but that implies less space for cargo and lower revenues. Or they could ship the same amount of cargo with a similar tank size, but then they have to refuel more often. And since the ship is docked while refuelling, it does not make money by shipping cargo around the world.

Our calculations indicate that vessels that run on methanol would have to tank 2 to 2.5 times more often compared to vessels that run on HFO, MGO or VLSFO (14 times during the year compared to 6-7 times). Note, however, that the number is pretty similar to ships that run on LNG.

The picture is even worse for vessels that run on ammonia or hydrogen. Due to the chemical characteristics, they have to tank about five times more often if they install a similar tank size compared to vessels which run on oil-based fuels. But tanking around 30 times a year is not a realistic option, so the tank size for ammonia and hydrogen-propelled vessels needs to be larger, which implies less space for cargo if the ship size stays the same.

It's important not to get carried away. Synthetic fuels clearly will be part of a net-zero pathway, in particular for hard-to-abate sectors such as shipping and aviation especially as the ‘easy technological solutions’ such as electrification and end-of-pipe solutions such as Carbon Capture and Storage hold little promise. But we can’t take it too easy, there are downsides as well.

So while synthetic fuels can be produced in a green way, they won’t fly simply because they are green. Synthetic fuels have to beat the incumbent fossil technology, but that won’t be a slam dunk, given the poor physics and economics of synthetic fuels. Therefore, we find it hard to envision a future in which synthetic fuels fully replace fossil fuels in marine shipping.

That does not mean their future role will be marginal either. After all, there are very few other zero-carbon options for marine shipping available other than bio-fuels, of which the supply will be limited. Zero-carbon shipping simply means zero-carbon fuels! That’s why synthetic fuels will be part of the sector’s pathway towards a net-zero economy, but to what extent is yet hard to anticipate.

Finally, policy developments are likely to push for synthetic fuels too. The European Union aims to reduce the greenhouse gas intensity by 80% in 2050 compared to 2020 levels, starting with 2% in 2025. And the IMO is facing mounting pressure to raise its ambition to reduce carbon emissions. That will also mean that shipping will be forced to start using low-carbon fuels.

To conclude, synthetic fuels come with higher costs. The direct costs of higher fuel prices and the indirect costs of more frequent refuels or less cargo that can be shipped. Hence shipping rates need to be higher for vessels that run on synthetic fuels. Secondly, fossil fuels damage the climate, but they are often superior in terms of chemical characteristics. In that regard, they are hard to beat.

It’s still too early to say when shipping will become verifiably sustainable. Even today, the routes to zero emissions are unclear. And they're expensive. But at least we can see a potential path to a cleaner maritime industry, even if we can’t say when we’ll get there nor which of the available synthetic fuels will finally become dominant. Shipping will need to rely on a multi-pronged approach, starting with energy efficiency and one which includes biofuels and Liquified National Gas, if it's going to make good progress.