Decommissioning Offshore Wind Fixed Steel Pile Foundations: A Critical Review

Offshore wind has rapidly developed over the past three decades, with over 6000 fixed-bottom substructures installed in Europe alone as of 2022. Despite this progress, there has been limited focus on the end-of-life stages, particularly decommissioning, which is currently the default option. Sustainable offshore wind development hinges on effective decommissioning strategies for fixed-steel pile foundations. This review critically examines state-of-the-art pile-foundation-decommissioning methods recently tested in industry and academia, including partial-removal techniques like internal cutting and external cutting and full-removal approaches such as excavation and novel extraction methods. Key factors influencing decommissioning decisions, such as seabed disturbance, environmental impact, reuse potential, and cost, are discussed. Analyses reveal that current partial-removal strategies could render vast swaths of marine areas inaccessible for future development. In contrast, full removal through extraction may enable complete recycling and minimise post-decommissioning monitoring. However, significant knowledge gaps remain regarding novel extraction methods' scalability, technical feasibility, and economics. Extensive research encompassing engineering, environmental, and economic dimensions is essential to develop holistic pile-foundation-decommissioning solutions that facilitate the sustainable long-term growth of offshore wind.