Within the project “Chemical Emissions from Offshore Wind Farms” (OffChEm), methods have been developed to assess possible chemical emissions from the corrosion protection of wind farms. Thus, for the first time, an extensive data set on the current situation in the North Sea could be collected.
The research was done from 2017 to 2021 by the Federal Maritime and Hydrographic Agency in cooperation with the Helmholtz-Zentrum Hereon (formerly known as Helmholtz-Zentrum Geesthacht). Trace metals in seawater and in the sediment could then be quantified with the help of the newly developed methods. In the laboratory, the researchers analysed the components of various galvanic anodes, known as sacrificial anodes. These are often used as corrosion protection for offshore wind farms.
The researchers identified the following elements for further investigations in the field: aluminium, zinc, indium, gallium, lead and cadmium. The elements indium and gallium can be used as tracers for sacrificial anodes. They rarely occur naturally and no other human sources are known in the open sea.
In total, four ship campaigns were conducted in the area of offshore wind farms in the Exclusive Economic Zone in the German Bight. The collected data shows that concentrations of the selected elements in both water and sediment are within the range of the known variability for the study area.
However, the researchers observed locally elevated concentrations for the elements indium, gallium, zinc and aluminium in the water during certain weather conditions. Locally elevated concentrations were also found in the sediment, especially for lead.
Nevertheless, no direct effects from the use of sacrificial anodes on the marine environment are currently apparent based on this data as well as the prevailing dilution and distribution processes. However, such chemical emissions could increase further as a result of the ongoing development of offshore wind energy.
Therefore, the Federal Maritime and Hydrographic Agency supports the development and use of procedures, which are as environmentally friendly as possible. In the future, wind farm projects should increasingly use impressed current cathodic protection systems. These are associated with very low chemical emissions into the marine environment.