We spoke to Dr. Johanna Rauchenberger, Head of Group Quality & HSE, and Dietmar Pinkernell, Head of Sustainability & Product Safety at MAN Energy Solutions, about their strategy for sus-tainable maritime transportation.
Pilot projects such as the »green corridors« are particularly important to us. They are more than just a test bed – they mark a real turning point for shipping. In an industry facing fundamental change, initiatives like these create the space to test new technologies under real-world conditions. For us as an engine manufacturer, they are a welcome opportunity to show what is already technologically possible – and where there is still a concrete need for action.
Above all, they offer the opportunity to not only discuss low-emission propulsion solutions in theory, but to actually test them in everyday use. And with every ship that is tested and moves through such a corridor, we learn more about how these fuels behave in operation – how reliable they are, how efficient they are, and how well they can be integrated into existing systems.
In addition, »green corridors« also help at the regulatory level. They make it easier for legislators to create suitable regulatory frameworks – faster, more targeted and with a better understanding of the technical background. At the same time, such projects also drive infrastructure development: Where ships run on new fuels, you automatically need supply networks, refueling facilities and logistics solutions.
Developing large engines for such alternative fuels is technologically demanding and presents entirely new challenges. Until now, marine engines have been designed primarily for heavy fuel oil or marine diesels – proven fuels whose behavior in engines we have known in detail for decades. With new energy sources, we are entering uncharted territory in many areas. This applies not only to the combustion properties themselves, but above all to material behavior, safety, and the entire engine architecture.
A key issue is corrosion resistance. Ammonia is extremely reactive and attacks many conventional materials, especially copper-containing alloys. This means that we have to switch to highly resistant materials, including special stainless steels and nickel-based alloys. The problem with methanol is somewhat different: Although it is less corrosive, it attracts water, which can increase material fatigue in the long term. Here, too, specially coated or stainless materials are used to ensure the service life of the components.
Besides the materials, another focus is on the injection and combustion systems. Ammonia has a high ignition temperature and is relatively difficult to ignite. In order to burn it efficiently, we either have to resort to pilot ignition with diesel or hydrogen, or develop completely new ignition systems. Methanol, on the other hand, is easier to ignite but has a lower energy density. This means that more fuel must be injected, which requires larger injection systems and carefully adjusted compression.
The safety requirements should not be underestimated either. Ammonia is toxic, which means that any leak in pipes or tanks poses a serious risk. The entire fuel system must therefore be extremely leak-proof, complemented by sensors and emergency systems. Methanol is less toxic but highly flammable. Here, too, a well-designed safety architecture is required.
An aspect that is often underestimated is the industrial scaling. It is not enough to build individual prototypes – what is crucial is that these new technologies are transferred to economical series production. In order to do this, we need to develop new processes for reliably and efficiently processing specialized materials in large quantities. The test procedures must also be adapted to new chemical and thermal loads in the engine.
Dual-fuel engines are a key component of the maritime energy transition. Especially at a time when the industry is under intense pressure to reduce emissions without losing its economic foundation, they offer a way to combine both: immediate progress in reducing the carbon footprint and long-term investment security.
Methanol and ammonia will not be available in sufficient quantities in the foreseeable future. The DF concept is a way to make the switch gradually, and it can be adapted to how the supply infrastructure grows because ships can use whichever fuel is available. This gives shipping companies some breathing room to invest in the fuels of the future now and avoid stranded investments.
There’s more: Simply building new, climate-friendly ships is not enough to achieve global climate targets. On average, ocean-going ships are in service for 25 to 30 years. These existing fleets must also be modernized. The dual-fuel concept makes this possible because many ships can be retrofitted for DF operation with synthetic fuels without having to replace the engine.
Dual-fuel systems also accelerate technological development toward real zero-emission solutions. Those who operate a methanol or ammonia engine in dual-fuel mode today are gaining valuable insights into combustion behavior, material stress, and into how the systems interact. All of this feeds directly into the next generation of emission-free engines.
That is precisely why we see dual-fuel technology not only as a practical compromise, but also as a strategic decision. It combines environmental protection, economic sense, and technological foresight.
Green hydrogen is an exciting and significant building block of the energy transition in the long term. But for the maritime industry, which needs solutions today, methanol and ammonia offer a clear advantage. The limitations of hydrogen quickly become apparent at sea, especially when you consider the requirements for range, safety, and infrastructure. In many cases, methanol and ammonia are simply the more practical solutions.
Methanol and ammonia have a significantly higher energy density per volume than hydrogen. This is an unbeatable argument for long-distance maritime transport, where space and weight play a key role. Hydrogen, on the other hand, must either be extremely compressed or liquefied at minus 253 degrees Celsius – both of which place enormous demands on storage and insulation. In comparison, methanol can be stored at ambient temperature and ammonia under relatively simple conditions.
Another point is the integration into existing drive concepts. Methanol can be used in modified diesel engines with manageable effort. Ammonia can also be used in large engines if certain technical adjustments are made. In contrast, we see hydrogen primarily in stationary applications.
Nor should we forget the energy losses along the chain: Liquefying hydrogen is extremely energy-intensive and can cost up to a third of the original energy content. When green hydrogen is used to produce methanol or ammonia, however, these energy carriers can be stored and transported much more efficiently.
Ammonia is toxic, highly volatile, and has a corrosive effect. It requires a well thought-out safety concept, because the protection of the crew, the ship, and the environment must have the highest priority. The challenge already begins with storage and handling. Ammonia can be kept liquid either under pressure or at low temperatures – both of which require specially designed tanks and piping systems. Double-walled structures with integrated leak warning systems are used to prevent leaks in the event of a malfunction. And instead of copper or zinc alloys, specially coated or highly resistant materials are used as sealing materials.
A key element is permanent gas monitoring. Highly sensitive sensors are installed in engine rooms, storage tanks, and all safety-relevant areas. These sensors reliably detect even the smallest amounts of ammonia and trigger automatic safety mechanisms: The fuel supply is interrupted, exhaust air systems are activated, and endangered zones are ventilated or sealed off. This makes it possible to respond quickly and effectively in an emergency.
The fuel supply itself must also be designed for the highest level of safety. Injection systems are equipped with multiple safety valves to prevent the uncontrolled introduction of ammonia. After each operation, the system is automatically flushed – usually with an inert gas such as nitrogen – to remove any residues. Since ammonia is also highly flammable, great attention is paid to the combustion process and its control to make sure that the combustion process remains stable and controlled.
Of course, the protection of the crew is also the focus of attention. The crew must be specially trained, not only in handling the fuel, but also in emergency management. Personal protective equipment, respirators with ammonia filters, protective suits, and mobile eye wash stations are part of the basic equipment. Every refueling and every maintenance operation is carried out in accordance with established safety protocols, accompanied by emergency plans and regular training exercises on board.
The overall approach is rounded off by international safety standards. The IGF Code issued by the IMO, which regulates the safe use of gaseous or low-flashpoint fuels, provides the legal framework here. SOLAS and MARPOL guidelines are also adapted to the specific properties of ammonia in order to maintain a consistent level of safety worldwide.
There are many factors at play here. What is clear, however, is that both fuels have the potential to play a key role in the decarbonization of shipping. The difference lies primarily in the time frame and the infrastructure conditions.
Green methanol currently has the edge in terms of availability and scalability. It can be produced in two ways – either from biomass or by combining green hydrogen with CO2 from industrial processes. The big advantage is that many existing production facilities can be converted to these new sources. This means that methanol can be made available relatively quickly and in larger quantities – especially if there is political support and clear demand from the market.
Ammonia is a bit more complex, though. Its production is based on the synthesis of hydrogen and nitrogen – an established process, but one with high energy requirements, especially if the hydrogen is to be obtained from renewable sources through electrolysis. The expansion of wind and solar energy is the critical bottleneck here. Large-scale industrial plants for producing this green variant are still lacking, but there are numerous projects underway around the world that could deliver initial quantities in a few years.
Methanol also is a globally traded commodity, it is transported in large quantities and can be handled with manageable effort using existing storage and bunkering systems. Liquid at ambient temperature and not overly toxic – this makes it a fuel that can be used without fundamentally redesigning port systems. Ammonia, on the other hand, requires more: closed systems, special sensors, and high safety standards. Although it is already being used globally, especially in the fertilizer industry, targeted investments are necessary for its use on board ships and in ports.
In terms of economic viability, both fuels are currently still more expensive than conventional fuels. But that will change. The more production capacity is created, the more economies of scale will come into play. At the same time, the political and regulatory costs of fossil fuels are rising – for example, because of the EU Emissions Trading System and CO2 taxes. This is shifting the price structure and making green alternatives increasingly competitive.
Methanol will therefore be available more quickly in the short term, while ammonia offers major advantages in the long run – such as its potential for CO2-free combustion – but this will require more time and investment. There are also differences in the areas of application: Methanol may be preferred in passenger shipping due to its lower toxicity. Ammonia, however, is predicted to have great potential in the transport of goods. The bottom line remains: Alternative fuels complement each other – and together they could have a decisive impact on the transition to emission-free shipping.
studied computer science at RWTH Aachen and went on to earn a doctorate in engineering sciences at the Fraunhofer Institute for Production Technology IPT in Aachen.
She moved into mechanical and plant engineering in 2009, initially taking over quality management at MAN Energy Solutions at its Zurich location. After various positions in Germany and abroad, she now heads the central quality department at MAN Energy Solutions SE with global responsibility for quality, management systems, occupational safety, environment, sustainability, and product safety.
»What particularly impressed me during my time at Fraunhofer was the interdisciplinary collaboration. Mobility is not an isolated topic, but rather an interplay between a wide variety of sectors: Drive technologies, infrastructure, political conditions, market mechanisms – everything is connected. The recipe for success is to combine the different perspectives and work toward a common goal.«
studied technomathematics and began his professional career in 1995 at MAN B&W in Augsburg, now MAN Energy Solutions SE. He progressed through various development positions and, among other responsibilities, led the engineering design for large diesel engines.
In 2016, he moved to the company’s central quality department, where he was responsible for occupational safety, environmental protection, and product safety in a staff function. Today, he leads an interdisciplinary team as Head of Sustainability & Product Safety and coordinates company-wide sustainability initiatives, strategic projects, as well as internal and external reporting in his area of responsibility.
Fraunhofer Institute for Production Systems and Design Technology