Synthetic polymer ropes are increasingly replacing metal chains as mooring lines for floating offshore wind farms (FOWF) due to their lightweight, yet high-strength properties. Key functional requirements for mooring lines include high fatigue and abrasion resistance to endure dynamic loads from wind and waves, low creep rates for long-term station-keeping stability, adequate stiffness to prevent excessive tension, and UV resistance for durability in harsh marine environments. These ropes typically feature a multi-layered structure consisting of an inner core surrounded by a filter and a protective jacket. The core is commonly made from high-performance synthetic fibres like HMPE, PA6, PET or aramid, each material containing a range of additive chemicals. New mooring materials should be developed according to Safe and Sustainable by Design (SSbD) principles, where environmental risk assessment is essential. Ecotoxicity data for materials and chemicals are used to support the environmental hazard assessment phase of SSbD, identifying substances of concern, supporting safer design choices, and informing life-cycle assessments. By integrating ecotoxicity data into the SSbD framework, material choices that minimize the risks of ecological harm and contribute to overall sustainability of the FOW industry can be made.

This study assessed if chemicals leaching from mooring materials pose a risk to the health of marine organisms, and if ecotoxicological effects differ between materials. Six different polymeric (the jacket, filter and four different core materials HMPE, PA6, PET and aramid), as well as a traditional metal mooring chain, were immersed in natural seawater in a closed system, allowing mobile chemicals to leach into the water phase. Ecotoxicological properties of these leachates were then assessed by exposing marine organisms from different trophic levels in the marine food chain; the marine algae Skeletonema costatum and Atlantic cod (Gadus morhua) embryos. Tests were conducted according to ISO guideline 10253:2024 for marine algae and an adapted OECD 236 protocol for cold water marine fish. The seawater leachates were chemically (ICP-MS, GCxGC-MS) characterized to identify potential drivers of toxicity.

While the HMPE core and the chain displayed no signs of toxicity against marine algae, the filter, jacket and remaining core materials all displayed toxicity in descending order: PA6 > jacket > filter > PET > aramid. For the fish test performed with core materials, reduced survival and sub-lethal impacts on fish morphology and development were only observed in larvae exposed to PA6. The jacket material exhibited some toxicity, but not the filter material. The approach combining chemical leaching with ecotoxicity testing was successful in distinguishing the potential toxicity of different mooring materials and provide iterative input to material selection and rope design. It is important to emphasize that, for material comparison, the leachates were prepared with a high material to water loading, not representative of real scenarios. Further experiments with continuous leaching over time will be conducted to shed more light on the leaching kinetics and subsequent environmental toxicity of the different materials. Furthermore, chemicals identified in toxic leachates with potential hazardous properties will be highlighted for further investigation, allowing more benign replacements to be sought.

The offshore wind energy sector is rapidly evolving, with floating wind turbines playing a pivotal role in expanding renewable energy capacity in deep-water regions. Central to the stability and safety of these floating structures are mooring systems, which have traditionally relied on steel wire ropes. However, in recent decades, synthetic fiber ropes have gained prominence due to their favorable mechanical properties, including high strength-to-weight ratios, ease of deployment, and resistance to corrosion. Commonly used synthetic fibers include: polyester, polyamide, ultra-high molecular weight polyethylene (HMPE), and aramid, each offering distinct advantages and challenges in marine environments (Weller et al., 2015).
Despite the increasing deployment of synthetic mooring lines, the end-of-life management and recycling of these materials remain underexplored. While polyester and polyamide ropes have established recycling pathways—particularly informed by practices in the aquaculture and fisheries sectors—the circularity potential of HMPE and aramid ropes is less well understood.  Emerging evidence suggests that polyamide ropes can be recycled into yarns for textiles such as swimwear and activewear, while aramid fibers are currently repurposed into pulp for use in brake pads and other industrial applications. Novel technologies, some at the patent stage, are showing promise in enabling closed-loop recycling of HMPE and aramid ropes back into yarns, potentially enhancing material circularity (da Silva et al., 2025).
Several fiber rope manufacturers are actively pursuing sustainability initiatives, including take-back programs and recycling schemes aimed at reducing environmental impact. Current efforts focus on mechanical and physical repurposing strategies, such as converting decommissioned ropes into non-woven fabrics for use in industries like automotive, construction, home furnishings, and geotextiles. These approaches offer an alternative to thermal recycling, which involves melting and repalletizing the ropes. Aramid producers, for instance, are developing circular systems that incorporate mechanical, physical, and chemical recycling pathways to recover and reuse materials at the end of their operational lifespan. Similarly, HMPE manufacturers have demonstrated the feasibility of pyrolysis-based recycling and are engaged in initiatives to collect and process used ropes. This study synthesizes insights from scientific literature and direct communication with fibre producers and recyclers to map the potential post-decommissioning value chains for each of the four rope types. We assess the technological readiness levels of mechanical, chemical, physical, and thermal recycling methods specifically for offshore mooring applications. For each fibre type, we present a Sankey diagram illustrating the flow of materials from decommissioning through intermediate processing steps to the creation of new recycled products. These visualizations aim to support stakeholders in identifying viable recycling pathways and inform future strategies for enhancing circularity in offshore wind systems.
By providing a comprehensive overview of current and emerging recycling technologies, this work contributes to the broader discourse on sustainability in offshore wind infrastructure and highlights opportunities for innovation in fibre rope lifecycle management.

Offshore wind energy is a cornerstone of the global transition to low-carbon energy systems. While its contribution to reducing greenhouse gas (GHG) emissions is well established, its broader environmental impacts—particularly on biodiversity—remain underexplored in life cycle assessment (LCA) studies. LCA is a widely applied framework for evaluating the environmental impacts of a product or a service throughout its entire life cycle. Its holistic approach allows the comparison of multiple impact categories, identification of trade-offs, and detection of unintentional problem-shifting. Traditional LCA applications in renewable energy emphasise climate change metrics, often neglecting biodiversity loss, which is driven largely by land and ocean use. For instance, while large-scale offshore wind development contributes to reducing GHG emissions, it can negatively affect migrating birds through collision, disturbance, and habitat loss. Recent modelling developments now enable the inclusion of biodiversity impacts on affected species groups within the LCA framework. We propose here a critical review and synthesis of emerging approaches to integrate biodiversity impacts into the LCA framework for offshore wind farms. We focus on the life cycle impact assessment (LCIA) phase, where processes from the life cycle inventory are translated into comparable impact indicators. We review available LCIA models that estimate the biodiversity impacts of offshore and onshore wind farms, examining their impact pathways, units, geographical regions, and taxonomic groups. Despite these advances, several challenges persist. Many LCIA models are not yet integrated into mainstream LCA software, and essential inventory data—such as species distributions, migration routes, and habitat sensitivity—are often missing or difficult to obtain. This abstract contributes to the EERA DeepWind priority theme of Sustainability and Circularity by identifying the current gaps and challenges, and proposing a roadmap for integrating biodiversity into offshore wind LCAs.

In this work, we introduce a control strategy for actively mitigating single-bird collisions with wind turbine blades.
The proposed architecture consists of a high-level controller with bird avoidance capabilities interfaced with a regular wind turbine rotor speed controller on a lower-level. In this study, the lower-level controller is based on open-source ROSCO controller. Using an estimation of the time to collision and location of a potential collision in the rotor plane, the bird avoidance problem is formulated as an angle avoidance problem. Consequently, the higher-level controller modifies the speed setpoint of the lower-level controller, to steer the blades to a safe angular position at a given time.
The higher-level controller design is based on Model Predictive Control (MPC). It entails formalizing the control problem as a constrained optimization problem, solved at each control time step. The constraints encompass operational limits (ex. rotor speed, actuator capabilities), the bird-blade clearance constraint, and a Linear Parameter-Varying (LPV) model of the closed-loop wind turbine.
The effectiveness of the resulting control law is validated in a numerical simulation environment with the IEA 15-MW reference turbine, showcasing its potential for improving bird safety when provided with reliable bird detection and collision prediction data.