Offshore Wind Energy: Paint Peeling? Leichtweiß Institute for Hydraulic Engineering and Water Resources examines how paint particles spread in the ocean

In the coming decades, the expansion of offshore wind energy will result in the construction of numerous new structures in the oceans. In the Oostende Declaration, the countries bordering the North Sea set themselves the goal of achieving 300 gigawatts of wind energy capacity in the North Sea by 2050. This corresponds to around 20,000 new wind turbines. The planned expansion of wind farms also raises questions about their environmental impact. Particles can come off the foundations, which are coated with an anti-corrosion coating, and enter the sea. These unwanted chemical emissions have now been analysed for the first time by the Leichtweiß Institute for Hydraulic Engineering and Water Resources (LWI) at Technische Universität Braunschweig.

In a study carried out as part of the European Anemoi project, the scientists have analysed how the paint particles get into the water, how they spread there and which transport routes can be identified in the marine environment. The aim is to further reduce chemical emissions from wind farms. The results of this study have now been published in the Marine Pollution Bulletin.

Paint particles reach the seabed

Corrosion protection coatings for particularly demanding applications are mixed with additives such as zinc and glass flakes to increase their effectiveness and durability. This gives the paint particles a much higher density than seawater. This has a significant effect on transport: the particles sink in the water and are also transported horizontally by waves and currents as they sink. Once the particles have reached the sediments of the seabed, they are carried further by bottom currents and can reach the marine sediments. However, mixing processes on the seafloor can also trap particles in deeper layers of sediment, preventing further transport. The sediment then becomes the final sink for the particles. Throughout the transport process, marine organisms influence the processes, for example by forming biofilms on the particle surface, by ingesting particles during foraging, or by bioturbation, i.e. the burial of particles in the sediment by biological activity.

“The compilation of all possible transport pathways of spalled particles from the corrosion protection systems is the fundamental step towards being able to carry out future field studies and assessments. On this basis, possible future emission quantities can now be estimated in scenarios and later verified by field observations,” says Professor Nils Goseberg, Head of the Leichtweiß Institute for Hydraulic Engineering and Water Resources and co-author of the study.

Predicting the amount of particles from offshore wind farms

As there have been no studies to date on the amount of particulate matter to be expected, the LWI scientists have, for the first time, predicted what the emissions from coating could be in the regions with the highest density of offshore wind farms in the coming years. “The results show that a wind farm with an installed capacity of 250 megawatts could release between 430 and 2,200 kilograms of particles over a planned operating period of 25 years, assuming that one to five per cent of the applied coating flakes off during this time,” says Niklas Czerner, researcher in the department of Hydromechanics, Coastal and Ocean Engineering at LWI. Worldwide, this means that all offshore wind farms built by 2024 could release a total of 166 to 832 tonnes of particles into the marine environment over their entire lifetime. With an ambitious expansion of offshore wind energy, these emissions could increase to between 610 and 3,052 tonnes for all wind farms built by the end of 2035 in the study areas of the North Sea and South East Asia.

The question of whether particulate emissions have a negative impact on the environment cannot yet be answered by the current study. However, the study confirms that there is an urgent need for research into the impact on the marine environment of further expansion of energy production capacity. “Offshore wind energy is an important key technology for the transition to a sustainable and independent energy supply,’ says Niklas Czerner. “It is therefore very important to make this transition as environmentally friendly as possible and to identify and assess all potential risks so that countermeasures can be taken if necessary – such as the use of more environmentally friendly coating protection.”

Anemoi project

The Anemoi project is funded from 2023 to 2027 with around 3.2 million euros via the Interreg North Sea Programme. Around 470,000 euros of this will go to the Leichtweiß Institute for Hydraulic Engineering and Water Resources. Researchers from eleven European institutes are working closely with political decision-makers and industry on the project. Anemoi has the following objectives: Identify relevant chemical emissions of known and unknown pollutants from offshore wind farms, assess the impact on ecosystems and aquaculture measures, review current regulations and propose sustainable solutions and options for reducing chemical emissions from wind farms.