The maritime sector is facing enormous changes. The need for environmentally-friendly methods of transport is becoming more and more urgent in the light of the increasing intensity of the global climate crisis. Innovative drive system solutions have the potential to fundamentally change the maritime industry. We not only show how sustainable shipping works in theory, but also how it is already being put into practice with great success.
Shipping has been one of the most important means of transport for global trade for centuries. More than 90 percent of international goods are transported by ship,1 which makes this means of transport an indispensable element in the modern economy. Maritime traffic plays a central role in logistics chains, ranging from enormous container vessels transporting electronic goods from Asia to inland waterway vessels that ship agricultural products within Europe.
Despite its economic significance, shipping in historical terms has not, however, exactly been a pioneer when it comes to protecting the environment. The high level of consumption of fossil fuels, emissions of greenhouse gases or oil pollution are just some of the environmental problems that it causes. However, the tide is turning: A growing awareness of environmental issues and pressure from the general public during the last few years have created a situation where environmentally-friendly solutions have moved to the fore. The sector is now at a turning point where innovative technologies and advanced drive solutions have the potential to introduce fundamental change and make it much more sustainable. Promising developments and concepts in the field of sustainable shipping are emerging.
There is nowhere where climate change is being felt as strongly as on inland waterways. The transport companies, which ply the Rhine, Danube and Elbe Rivers, have been repeatedly confronted by low water levels for several years. This means that the inland waterway vessels have to unload part of their cargo according to the water level in the river in order to reach their destination. Then there is another challenge: While all the means of transport are competing to find the most innovative idea for alternative drive systems, the service life of an inland waterway vessel is much longer: A ship does not just operate for five to ten years, but for 50 years or even an entire century. At the same time, customers are demanding energy efficiency, for example, by saving fuel, and reductions in emissions. The sector is working on new concepts, but it will take some time until fleets that involve several thousand vessels across Europe have been equipped with alternative technologies.
One important component, for instance, is the engine that is used on board the inland waterway vessel. A great deal has taken place ever since the first inland waterway vessel was equipped with a diesel engine in 1937. The EU’s Stage V emissions regulations, which came into force in 2020, currently apply. They make the restrictions for non-road mobile machinery (NRMM) even more stringent and set stricter thresholds for emissions, particularly for particles and nitrogen oxides (NOx). Certification according to Stage V is mandatory for all engines that are used for new vessels operating along European inland waterways, but old, existing vessels are still exempt from these regulations.
Given the long service life of inland waterway vessels, it also makes sense to insert new engines into existing holds. A classic combustion engine is still directly connected to the propellor shaft as the drive system in the majority of European inland waterway vessels. However, more and more operators are moving towards replacing the combustion engine with an electrically powered motor. It will then make no difference for them which type of fuel supplies the energy for this engine in the future: It could be an efficient diesel engine or a combustion engine that is operated using hydrogen, methanol or ammonia. The benefit here is that it is only necessary to replace the engine, not the drive system. This saves considerable costs in terms of development and conversion work.
Rhenus is also modernizing its inland waterway fleet at this time. Vessels, which are being converted or renovated, are being fitted with Stage V truck engines that are suitable for maritime use, while current new vessels will be powered by a combination of hydrogen fuel cells, the latest Stage VI engines and electrical batteries in the future.
Another innovation on the inland waterways involves a new design for vessels. Rhenus is currently constructing new vessels for use on the Rhine River for its project partner, Contargo, and it will be possible to operate them even if water levels are extremely low. The vessel’s design has been developed in conjunction with the University of Duisburg and the Development Centre for Ship Technology and Transport Systems (DST) and corresponds to the latest scientific findings.
About 16,000 liters of diesel fuel are required for a round trip between Rotterdam and Mannheim if there is a conventional engine in the hold. It is possible to save approximately 5,000 liters on a round trip if the vessel is equipped with a diesel-electric drive system – and that means about 30 percent less fuel. The diesel-electric drive system combined with a battery and a fuel cell then requires up to 80 percent less, i.e. roughly 3,000 liters of diesel fuel. This in turn results in 80 percent savings in CO2 emissions for each round trip when compared to a conventional drive system.
Logistics specialists are not only looking for ways to achieve environmentally-friendly traffic on rivers, but also along coastlines: The need for eco-friendly processes has accelerated the development of alternative types of drive systems that aim to reduce the traditional dependency on fossil fuels.
Methanol, which was formerly a by-product of the coal and gas industry, is increasingly being viewed as a potential, environmentally-friendly fuel – as long as it is produced using green energy: The possibility of synthesizing methanol using renewable energy sources like wind, solar or hydro-electric power will offer a viable alternative to traditional diesel fuel in the future. Although methanol provides less energy density than diesel fuel, the advantages related to the reduction in emissions are significant. However, the challenge here involves higher production costs and the need to develop suitable infrastructure to distribute it. LNG, i.e. liquid natural gas, is particularly suitable for ships that operate on fixed routes. The investments in special fueling and bunker facilities pay off here because of the short and regular routes. An LNG drive system emits almost 100 percent less sulfur dioxide and particulate matter, 15 – 20 percent less CO2, 70 percent less nitrogen oxides and creates up to 50 percent less noise in comparison with a diesel-powered drive system. Battery-powered drive systems are also an increasingly attractive option for fixed routes where charging infrastructure is in place. They offer an emission-free alternative, particularly for fairly short distances and in regions where good charging infrastructure is available.
One example of implementing alternative drive systems in practice is to convert a coastal vessel, which has a payload capacity of more than 2,000 metric tons, to a methanol-ready drive system, as Rhenus is doing at this time. This approach enables the vessel to fully switch to methanol once the necessary infrastructure is available. Current restrictions, like the lack of fueling infrastructure, may still limit the immediate implementation, but the vessel is already equipped with the necessary alterations, for instance, special injection nozzles and stainless-steel pipes, which are relatively negligible in comparison with the effort and expenditure required for any full conversion work. This means that the coastal vessel is already equipped to meet the latest technical standards in order to satisfy current and future CO2 benchmarks.
Alternative drive technologies are best suited for ships that travel relatively short distances along coastlines. However, much of the world's trade is carried out over long distances on the high seas, from continent to continent. Although LNG, for example, is suitable for ships with high energy requirements over long distances, the current patchy infrastructure does not guarantee a continuous supply, especially with constantly changing routes. Passenger shipping shows how things can be done differently. For example, there are cruise ships that are powered by battery hybrid drives2 and LNG3. But even here, the ships sail on fixed, predictable routes - for example, along the Norwegian coast or in the Mediterranean.
The transition to more sustainable practices in shipping represents a complex challenge, but the advances being made with alternative drive technologies demonstrate that it is possible to introduce change. Provided that the correct regulatory support is in place and continual technological innovations are being made, the maritime industry can play a leading role in reducing emissions and minimizing environmental pollution. It faces the challenge of rethinking its business models and introducing future-oriented practices in order to safeguard ecological and economic benefits in the long term.
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