The hopper dredger Pedro Alvares Cabral on the Elbe, with terminals, harbour cranes and the Köhlbrand Bridge in the background
Above water

Sediment management is climate protection

Transporting goods by large seagoing vessels is particularly climate-friendly. However, to ensure that these large container ships can get as close as possible to their markets, waterways and harbour basins must be continuously cleared of excess sediment. With the right sediment management, significant reductions in climate-impacting emissions can be achieved.

Large ocean-going vessels as climate-friendly modes of transport

co2 emissions of different modes of transport
Comparison of average CO2 emissions from individual modes of freight transport. Sources: umweltbundesamt.de and IMO

Our goods cannot be transported in a more climate-friendly way than with large ocean-going vessels. A container ship with 20,000 TEU only emits around a third as much carbon dioxide per transported tonne of freight as rail freight and only a twentieth of a truck. Even feeder ships emit around five times more CO2 than a large container ship. Every extra kilometre that the ocean-going vessel can travel to the destination of the goods therefore protects our climate. If the ship travels to the Port of Hamburg instead of Wilhelmshafen, for example, that's around 200 kilometres more by sea and around 20 kg of CO2 saved per tonne of freight compared to a truck.

In order for the climate-friendly mega-ships to be able to call at the Port of Hamburg (over 30% of the goods remain directly in the region), the access road and harbour basin must be reliably cleared of excess mud and sand. This is ensured by the sediment management of the HPA and the WSV.

However, the dredgers also consume fuel and emit CO2 . There are currently two approaches to minimising CO2 emissions: More climate-friendly fuels or ship propulsion systems and reducing the amount of dredging by minimising recirculating dredging.

Climate-friendly dredgers

The grey hopper dredger Kaishuu on the Elbe in front of Falkensteiner Ufer and the Wedel power station
The KAISHUU dredger from Jan de Nul used exclusively climate-neutral recycled fuel on behalf of the HPA in 2021.

Climate-friendly fuels are already being used. This can be done without having to make technical changes to the ships. In 2021, the relocation of sediments into the North Sea for the E3 tonne was carried out exclusively with climate-neutral recycled fuel made from production residues. This enabled CO2 emissions to be reduced by 85% compared to marine diesel. Around 30,000 tonnes of CO2 could be saved in this way. This corresponds to around 1000 flights from Hamburg to Munich. Climate-neutral fuel was also used proportionately in 2022, although it was not always available.

In addition to recycled fuel, there are other ways to reduce climate-impacting emissions. A reduction of around 13% is possible through the use of LNG. The use of hybrid drives, e-fuels (i.e. fuels produced from sustainably generated electricity) or hydrogen drives are also possible. The first hopper excavator that runs exclusively on hydrogen is currently under construction in the Netherlands.

However, it is not only climate-friendly drives that reduce CO2 emissions; the efficiency of dredging also has a decisive influence. Larger and modern dredgers consume less fuel per tonne of dredged material than older and smaller equipment. That's why we make sure that the most efficient equipment is used in our deployment plans and tenders.

Climate-friendly sediment management

In addition to these technical options, sediment management itself, i.e. the decision as to where which dredged material is relocated, has a significant influence on the carbon footprint. Our primary goal is to reduce the amount of dredging, because the less dredging is required, the less climate-impacting fuel is consumed. In addition to the dredging volume, the distance between the dredging site (i.e. the harbour) and the relocation sites is also crucial. The shorter the journey, the lower the emissions.

However, if the dredger does not take the sediment far enough towards the North Sea, for example only to the relocation site near the Elbe island of Neßsand, a large part of it is washed back into the harbour by the strong tidal current and has to be dredged again. This creates a dredging cycle, which in turn results in higher emissions overall. The aim of our sediment management is therefore to minimise these dredging cycles without having to cover unnecessarily long transport distances. Relocation sites in the Elbe estuary are ideal in this respect.

However, many other boundary conditions must also be taken into account when choosing the optimal relocation site, such as nature and environmental protection and shipping safety. However, calculations show that a sufficient discharge of sediments over the years can lead to significantly lower dredging volumes overall and therefore also to considerable savings in climate-impacting emissions. We are therefore working on developing sufficient dredging options from which the sediments are not returned to the harbour. This is another way we are contributing to climate protection.

Climate protection strategy of the HPA

For its sediment management, the HPA, together with other partner organisations of the sediment network SedNet, signed the "COP26 Climate Change and Sediment Management Pledge" in November 2021 and committed to measures for more climate protection. The HPA has been pursuing a climate protection strategy for the entire company since 2011. In this strategy, the HPA has set itself the goal of reducing its CO2 emissions by 50 per cent by 2025 compared to 1990 and by 100 per cent by 2040, or to be climate-neutral. By switching the power supply to the HPA facilities to green electricity, more than 50 per cent of CO2 emissions have already been saved, meaning that the interim target for 2025 has been achieved earlier than planned. Our Sustainability Report shows what the HPA is doing to achieve these goals.

FAQ on sediment management and climate protection

 

The CO₂ emissions can vary greatly in individual cases. However, large container ships are the most efficient means of transporting goods: they only emit 5 to 30 grams of CO₂ per tonne and kilometre transported (for comparison: truck 30 - 150 grams, rail 10 - 60  grams, plane 500 - 2000 grams).  

 

 

 

A large container ship with 20,000 TEU (Twenty-foot Equivalent Unit) requires significantly less energy per transported tonne and causes considerably lower emissions than rail, truck or aircraft. Feeder ships (smaller container ships that serve as suppliers and distributors for larger ocean-going vessels and ports) also emit more CO₂ than large container ships. The further a container ship transports goods, for example on the Elbe far inland, the more CO₂ can be saved compared to other means of transport.

 

 

 

Water depth maintenance is the most important prerequisite for the climate-friendly transport of goods by sea-going vessels. Targeted and flexible sediment management with several transport options also ensures that less dredging is required and that transport routes for sediments remain as short as possible. This not only saves costs, but also large amounts of CO₂ emissions.

 

 

 

The HPA has so far focussed on climate-friendly drives, the use of recycled fuels and efficiency improvements in dredging work. One example: in 2021, a large dredger was operated exclusively with climate-friendly recycled fuel, saving around 30,000 tonnes of CO₂ - the equivalent of around 1,000 flights from Hamburg to Munich.

 

 

 

Climate-friendly ship propulsion systems are constantly evolving. In addition to recycled fuels, LNG, hybrid drives, e-fuels and, in future, hydrogen and ammonia are increasingly being used. Modern, larger and more efficient dredgers also consume significantly less fuel per tonne of material.

 

 

 

The HPA had set itself the goal of reducing its CO₂ emissions by 50 % by 2025 compared to 1990 and becoming climate-neutral by 2040. The interim target has already been achieved by switching to green electricity. Further measures include a massive expansion of shore power capacities, as well as the development and implementation of projects for climate-friendly fuels, energy hubs and efficiency measures.

 

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