Impact of offshore wind farm decommissioning on marine biodiversity

To support this, Vattenfall has initiated a series of projects focused on generating empirical impact data and developing decision-support tools that integrate environmental evidence to inform decommissioning. 

We are advancing several R&D initiatives that address some key knowledge needs with more studies underway.

Biodiversity and decommissioning: To further strengthen the scientific foundation for decommissioning strategies, Technical University of Denmark and Vattenfall have conducted a PhD research project examining how different decommissioning scenarios influence marine biodiversity. 

The research developed a modelling framework that integrates ecological effects into life cycle assessments, supporting transparent evaluation of structural end-of-life options. It also included a national survey exploring public perspectives on alternative approaches, assessing how information on reef effects biodiversity, and climate considerations shapes societal support.

Biodiversity and non-native species: Aarhus University’s biological monitoring during the removal of the Stor Middelgrund metocean mast has documented the establishment of a diverse native marine community over 16 years of operation, alongside a limited number of non-native species that are already widespread in Danish waters.

These findings provide valuable empirical insight into ecological communities associated with the artificial reef formed by offshore wind infrastructure. Read more here.

Underwater noise during decommissioning activities: Field measurements collected during mast removal operations showed that dredging and jack-up vessel activity generated higher noise levels than cutting operations. Analysis indicated a low risk of auditory injury to harbour porpoises, with any behavioural responses expected to be localised and short-term.

These measurements provide an important baseline for future planning and mitigation of decommissioning-related noise impacts.