Hydrogen-based propulsion and energy efficiency as options in international shipping

To reduce the climate impact of international shipping, research projects worldwide are testing hydrogen, ammonia, methanol and other energy carriers as alternative fuels for ships. "No single energy carrier has been broadly accepted yet and coexistence is likely," according to Jens Artz, head of the H2-Compass project at DECHEMA, the Society for Chemical Engineering and Biotechnology. "There is no fuel which is fundamentally superior to the others." The H2-Compass project is publishing its analysis on the use of hydrogen in international shipping today. "In addition to switching to climate-friendly fuels, there is also other climate protection potential in shipping: larger ships that sail more slowly and whose operation is optimised consume less energy per tonne transported," says Andrea Lübcke, head of the H2-Compass project at acatech, the National Academy of Science and Engineering.

Today, ships transport about 70 percent of all goods - in terms of transport performance, measured in tonne-kilometres. The International Maritime Organization (IMO) expects the demand for sea-bound goods transport to grow every year. This is because global economic growth also increases the need for international transport. The OECD predicts that the transport routes covered by ship will triple by 2050. By 2100, ships could be transporting more than three quarters of all goods.

Climate target for international shipping: minus 50 percent by 2050

Up to now, ships have mainly used heavy fuel oil, but also diesel and liquefied natural gas (LNG). Heavy oil as a fuel causes environmental pollution in the form of sulphur and nitrogen oxides, soot and particulate matter, as well as greenhouse gases (GHG). In order to reduce the climate impact of shipping, the IMO adopted a resolution in 2018 in which a GHG reduction of minus 50 per cent by 2050 compared to 2008 was agreed as a sector target for the first time. A tightening of this target is in the making.

Hydrogen, methanol and ammonia are the most likely heavy oil alternatives

Tests are still being conducted to determine which climate-friendly heavy oil alternatives are most suitable. There are more than 60 projects on this worldwide: Near the coast, battery-electric solutions and gaseous hydrogen, sometimes combined with fossil fuels, are favoured. For the long haul, liquid hydrogen is conceivable due to its energy density. Ammonia is also being tested as a ship fuel. The advantage: ammonia is easier to store than hydrogen and the volumetric energy density is about 50 percent higher. The disadvantage: in high concentrations, ammonia is toxic and flammable. Since it is lighter than air in gaseous form, appropriate ventilation must be available. Methanol is another candidate for replacing fossil fuels, as today's engines can be converted to methanol comparatively easily. However, the energy costs are significantly higher, since carbon dioxide will have to be extracted from the air.

Efficiency gains as another lever for climate neutrality

It is also important to improve the efficiency of ships. The energy demand per transported tonne can be reduced in shipping primarily through the use of larger ships, slower cruising speeds ("slow steaming") and efficient operation.

Analysis of hydrogen use in shipping is part of H2-Compass meta-analysis

The analysis on shipping published today is part of a meta-analysis conducted by the National Academy of Science and Engineering, acatech, and the Society for Chemical Engineering and Biotechnology, DECHEMA, as part of the joint H2-Compass project. The meta-analysis, which brings together a large number of different studies and scenarios, forms the basis for a coherent picture of the future use of hydrogen in various sectors.