We want to reduce the discharge of pollutants, coating particles and biocides into the port waters. That is why bremenports is a member of the CLEAN project group which aims to promote transparency and provide clear specifications for environmentally compatible underwater hull cleaning. Until more sustainable antifouling strategies, such as hard coatings, have become standard practice, it is vital to prevent the uncontrolled discharge of toxic substances and particles from the currently used coatings into the sea.

Rules for eco-friendly hull cleaning

It is now mandatory to obtain a permit for underwater hull cleaning at the ports of Bremen. This is prescribed in the first nationwide guidelines for hull cleaning drawn up by the CLEAN project group. bremenports is also a member of this project group, which is funded by DBU, the German Environmental Foundation.

[Translate to English:] Collage: Taucher, Verschmutzung und Ablagerungen an Schiffen


Like all other underwater surfaces at the ports, ship hulls are prone to biofouling, i.e. the accumulation of organic growth. This increases fuel consumption, which is why antifouling coatings are used. But as these coatings decompose, they release biocides.

If the antifouling coating on the ship’s hull does not work effectively, for instance because the ship has been laid up for a prolonged period, moves too slowly or sails in trade areas other than its intended routes, the resulting growth leads to higher water resistance and thus significantly higher fuel consumption, higher emissions and additional costs for the shipowner.


That is why such biofouling coatings are increasingly removed, and this is done while the ship is in dock or simply below the water surface. However, when these underwater cleaning processes remove not only the biofouling, but also the old paint coatings, this leads to the uncontrolled discharge of biocides, microplastics and invasive species that have been carried in the biofouling into the sea. This is especially the case if the removed material is not properly collected and disposed of. It is not clear what quantity of pollutants enters the water, because most of these underwater cleaning processes are carried out “under the radar”, even though it is actually mandatory to obtain a permit. The CLEAN project research group has now drawn up guidelines for the issue of these permits.


Current research pursues a strategy that involves dispensing entirely with biocides and soluble coatings as protection against biofouling and instead advises regular hull cleaning to remove growth. Abrasion-resistant, biocide-free coatings can be cleaned in an environmentally compatible way.

In order to investigate this approach in further detail, a number of business enterprises and institutions, under the overall coordination of the Senator for Climate Protection, Environment, Mobility, Urban Development and Housing, have joined forces in the CLEAN project to promote “freedom from hull fouling thanks to proactive cleaning on abrasion-resistant, biocide-free coatings for the shipping business”. In addition to bremenports, other members of the CLEAN project group include Bremen’s Port Authority and the LimnoMar institute.

[Translate to English:] Collage: Reinigungsvorgang und Technik