Future of sustainable fuels

Sailing towards a carbon-neutral future

Big changes are afoot in the shipping industry as a whole, and in marine propulsion generally, as the urgent need to find a path towards zero-emissions shipping confronts a dramatic projected increase in world shipping by 2050. Shipping accounts for 90% of global trade, and while it is still the most efficient way to move goods, it also is responsible for 3% of the world’s emissions, a figure that is projected to increase by as much as 250% by 2050 as demand grows.

Big changes are afoot in the shipping industry as a whole, and in marine propulsion generally, as the urgent need to find a path towards zero-emissions shipping confronts a dramatic projected increase in world shipping by 2050. Shipping accounts for 90% of global trade, and while it is still the most efficient way to move goods, it also is responsible for 3% of the world’s emissions, a figure that is projected to increase by as much as 250% by 2050 as demand grows.

To mitigate the environmental impact of this increase, the International Maritime Organization (IMO) recently adopted a new strategy aimed at reducing greenhouse gases (GHG) from shipping by 50% by 2050 compared to 2008 levels. This comes on top of the previously established NOx and SOx caps that should be in place by 2020. The shipping industry needs to quickly explore new solutions to cut emissions.

The challenge is that there is no panacea yet that will create such a zero-emissions shipping ecosystem. Instead, available opportunities and acknowledged trends include large scale roll-outs of alternative fuels, (fully electric ships and hydrogen fuel cells, as popularised in the media), and increased digitalisation of the industry and the on-board utilisation of wind and solar energy.

The inside (industry) and Wärtsilä’s perspective, in particular, include exploring these opportunities while bearing in mind profitability, scalability and the urgency. It is increasingly understood that the internal combustion engine together with fossil (and later bio or synthetic) LNG provides an excellent platform for actually achieving the set emission targets for 2050 and beyond.

If the industry really wants to address emissions, the consensus is that the internal combustion engine still offers the most realistic emissions-reduction potential. Additionally, this solution requires only existing infrastructure, minimising the amount of investment needed. Generally speaking, a de-fossilised future could take this path: LNG->bioLNG->synthetic LNG, which would maximise the utilization of existing infrastructure.

The estimated cost of synthetic LNG in 2030 is on par, or lower, than other alternative fuels, and this combined with the world’s decade-long experience with marine LNG fuel makes it a safe and reliable bet. Bare in mind that other alternative fuels would take between 10-20 years to be accepted by marine classification societies, not to mention the time required to develop infrastructure and bunkering facilities etc...

Regardless of the potential of future fuels, the internal combustion engine still has the flexibility to burn most combustible substances. By burning LNG in a modern combustion engine we can immediately reduce the GHG emissions by 20-25% compared to the diesel engine. Methane leakage during production and combustion is still a challenge that negatively impacts the GHG footprint of using LNG, being 28 times more potent than CO2. At the same time, this is an opportunity for the industry to improve, something Wärtsilä, Shell and others have committed to doing.

Trends of the future

Recent efforts have successfully reduced local emissions of nitrogen, sulphur oxides and particle matter from ship engines across different regions of the world — a result of ongoing and increasingly stringent emission regulations by the IMO which began in the 1990s and continue to the present.

But GHG emissions are widely acknowledged as the primary source of global warming, with all their well-publicised consequences to the planet. Thus far, there has not been a large-scale industrialised solution to solving the emissions problem. In the short- and medium-term, there is no known single solution to the challenge. There is more potential for the long-term, however.

There are currently four long-term technology trends that can help mitigate climate change.

  • Alternative fuels using internal combustion engines;
  • Fully electrical propulsion enabled by batteries, applicable mostly for smaller vessels;
  • Hydrogen-based operations using fuel cells;
  • Optimised vessel operation through digitalisation

Alternative fuels using internal combustion engines

There is a plethora of fuels that can be used in marine engines. But with carbon-neutral biofuels, it’s necessary to consider what renewable energy sources are used in the production to start with. Other critical aspects to consider in the selection of fuel for a new vessel are its availability and energy density. For fuels based on biomaterial, the main challenge is the local availability of sustainable feedstock. For most fuels, the current supply chain is unevenly developed and will require substantial investment to accommodate future needs.

Bio-LNG has a big advantage in that many different kinds of sustainable feedstocks can be used, from manure via sewage residue to forest residue and many other types of waste.

Fully electric propulsion enabled by batteries

There are many challenges in developing battery technology. First, capacity and cost are still not at a feasible level for the marine industry. In 2018, the first fully electric cargo ship was launched in China. It had a range of 80 km after two hours of charging. This example demonstrates that battery operation for larger vessels today is mainly restricted to port areas for tugs and ferries, or for peak-shaving operations.

We believe this will remain true for the foreseeable future, meaning that other solutions are needed for the business of long-distance shipping which also is responsible for the bulk of total shipping emissions.

Secondly, charging batteries is time-consuming and requires high charging power and related infrastructure to limit charging times. Another challenge with respect to emissions is that any pollution from the on-shore generated electricity must be attributed to operating the vessel. Therefore, the electricity used should stem from hydro, solar and/or wind power to achieve zero-emissions in a true sense.

Finally, many of the materials used to produce batteries are precious metals. Cobalt, an integral component of the lithium-ion battery, for example, is being hailed as the ‘new gold,’ a cause for alarm since scarcity may create vulnerability in the supply chain. In addition, batteries are often categorised as hazardous, requiring special disposal procedures.

Hydrogen fuel cells

The almost too-good-to-be-true proposition of providing energy without emissions from hydrogen fuel cells is attracting the attention of the entire world. As renewable energy sources are already today the cheapest energy source in many places, hydrogen can be used and produced in a sustainable way.

This great potential is offset by some serious challenges, however. As with other renewables, one of the main issues related to developing this fuel cell is cost. Significant progress has been made within the automotive industry that could eventually improve the feasibility of marine applications as well, though recent developments in the automotive industry indicate a preference for batteries over fuel cells for most applications; this can possibly curb further fuel cell development. But as in the case of large-capacity batteries, the investment cost likely will plateau at a higher level than for automotive applications, due to the need for technology to mature and lower sales volumes.

The availability of hydrogen is another problem. Large-scale hydrogen production based on electrolysis demands large amounts of energy and has low total efficiency. This is perhaps the biggest challenge for hydrogen as a fuel itself, and for any other synthetic fuels based on hydrogen.

If renewable energy is available with even lower costs, the production of hydrogen is not the biggest challenge, unless the electrolysis is difficult to scale up. Another, if not even bigger challenge is the storage of hydrogen as fuel, as well as the operations: bunkering and transportation.

Therefore, synthetic fuels are actually more attractive than H2 and can be considered as a hydrogen carrier, when bound to CO2 or N2 in the form of CH4 (methane) or NH3 (ammonia).

Onboard hydrogen storage solutions pose another problem. High-energy density hydrogen can be stored physically as either gas or liquid. As a gas, it typically requires high-pressure tanks, while storage as a liquid requires cryogenic temperatures because the boiling point of hydrogen at one atmosphere is -253 degrees Celsius. Some applications centre around linking it with solids or within solids. Storing hydrogen in liquid form moreover will require storage of the fuel below – 253 C, under normal pressure, which adds to the complexity.

The most probable use of Hydrogen is as a component in producing synthetic fuels such as synthetic LNG, ammonia or methanol. However, large scale adoption of the hydrogen fuel cell as the primary energy source is unlikely for many years to come and cannot be considered a solution for meeting the IMO 2050 GHG targets. 

Optimised vessel operation through digitalisation

Shipping is by far the most cost-effective way to move goods around the world, and yet it is characterised by waste, pollution, and a multitude of inefficiencies, all of which present opportunities. A major reason for these inefficiencies is the lack of transparency between the huge number of actors involved in shipping goods today. The complexity and lack of real-time communication create congestion in high traffic areas, leading to increased emissions, operational costs, and significant delays.

Eliminating this waste is the basis for Wärtsilä’s Smart Marine Ecosystem. It focuses on connecting all agents and parties in the shipping industry to create the needed transparency and dynamics to optimise the complete logistic chain rather than sub-optimising the individual steps. This involves taking joint responsibility for operations, working together, ensuring that the right parties have access to the necessary information, and can access it at the right time. Smart Marine is about understanding that ships are only one element within the complete logistics chain. Vessels have to interact with ports, and they, in turn, have to interact with land-based transportation modes, all the way to the end customer. In the end, the main driver for this development is the end customers’ need for transparency, Just-in-Time arrival delivery, and low costs.

Optimising the connections between these elements will reduce fuel consumption and the related emissions significantly for the whole logistics chain as well as reduce delays in the deliveries. Digitalisation will not by itself create zero-emission vessels, but it will significantly lower the energy needed for transporting goods.

As the Smart Marine Ecosystem becomes the industry’s preeminent operating model, shared capacity will improve fill rates and reduce unit costs, big data analytics will optimise both operations and energy management, intelligent vessels will enable automated and optimised processes and smart ports will deliver smoother and faster port operations.


Despite the significant challenges, a roadmap towards zero-emissions shipping is beginning to crystallise. Already, sulfur, particle or black carbon emissions and NOx emissions of a low-pressure engine are already compliant with Tier III. But in order to reach the 2050 target set by the IMO, the industry must focus on rooting out inefficiencies, utilizing on board wind and solar power, increasing LNG investments globally, working on fuel flexibility for engines, expanding capacity investments for biogas and synthetic fuels to be mixed with LNG.

To reach the targets of the Paris agreement and IMO 2050 we need to start acting NOW and today the only established fuel that takes us towards these goals is LNG. Fossil LNG is however only an intermediate fuel and a parallel increase in production capacity for making bio- and synthetic-LNG using renewable energy sources is imperative as we recover waste/side streams from agriculture, food industry, landfills and waste water treatment and turn that into biogas or bio-LNG (LBG). In the future, there will be other fuels and technologies that will help us de-fossilise the shipping industry, such as Ammonia, Methanol, fuel cells, etc. However, today the combustion engine with LNG is the only way to put a real concrete dent in the GHG emissions.  And the longer we wait, the bigger the challenge will become. We have the means, we know the goal, so the time to act is now.

To comply with the IMO targets, radical change is needed – both in vessel design and power generation. However, the main challenge is fuel, and the related global investments in its production and infrastructure.

Written by
Fredrik Östman
Fredrik Östman
Fuel Conversion and Decarbonisation
Sebastiaan Bleuanus
Sebastiaan Bleuanus
General Manager Research Coordination & Funding, Technology Strategy & Innovation
Reetta Kaila
Dr. Reetta Kaila
Director, Sustainable Fuels & Environment