Abstract
Understanding the environmental impact of floating offshore wind is critical at this stage of the industry’s development to ensure that is commercializes sustainably. WFO’s Floating Offshore Wind Environment, Biodiversity & Cohabitation Subcommittee has spent the last two years discussing known and expected impacts as well as associated mitigation measures across three main themes: lifecycle carbon emissions, marine biodiversity (various species, habitats, wider ecosystems), and commercial fishing.
With over a hundred floater concepts on the market, it is not straightforward to estimate floating wind’s carbon footprint. This is because the fabrication stage is the hotspot for carbon emissions, where material extraction and component fabrication are intrinsic to the floater design. As a result, floater designers are conducting lifecycle assessments (LCA) to provide transparency on their technology’s anticipated footprint and enhance their competitiveness. Innovation in materials (concrete, steel, hybrid or other) is an important part of the discussion to improve not only reliability but also environmental performance. Ultimately, the main takeaway is that offshore wind contributes to 8-32 gCO2e/kWh and is one of the lowest carbon emitting sources of energy production. While floating wind is considered to emit in this same range or slightly more than bottom-fixed wind, it is important to weigh these values against our other options for energy production in the context of the climate and biodiversity crises as well as security of supply.
Although FOWTs share similar impacts to bottom-fixed offshore wind (e.g. risks to avifauna, seabed disturbance from export cable installation), the anchors, moorings and dynamic cables create unique interactions at the seabed and in the water column. For example, more compliant FOWTs may have sweeping mooring lines from platform excursion that create a continuous disturbance to benthic habitats in addition to their installation; mooring lines and free-hanging dynamic cables can potentially cause primary or secondary marine mammal entanglement; operational noise from turbine vibrations as well as EMFs from the dynamic cables need to be studied further in comparison to bottom-fixed wind technology. Finally, bio colonisation and attraction of life at the floater, mooring lines and anchors can have more spatially distributed ecosystem effects, especially in deeper waters.
Continuous, high-resolution and multi-parameter monitoring across longer time frames are needed to confirm the “positive” impact of FOWTs acting as artificial habitats for marine life. Results from the demonstrators and pilots are promising, but these are still preliminary and hence cannot be extrapolated to larger-scale floating wind farms. The initial findings are nonetheless foundational to our understanding of floating wind’s impacts and the effectiveness of mitigation measures. Pilot projects are notably valuable testing grounds for novel monitoring methods (e.g. eDNA, AI-supported data analysis) as well as nature-inclusive design approaches (e.g. artificial nurseries, more environmentally friendly materials), which need validation before being widely adopted.
Floating wind’s impact on commercial fishing cannot be understated. The spatial footprint of the turbine, station-keeping system and dynamic cables are expected to restrict allowable fishing areas more than in bottom-fixed wind farms. Across the world, the fishing community is concerned with how their activity will be affected. Unfortunately, the early stage of our industry makes it difficult to quantify and communicate expected impacts, as these depend on the floater and mooring system design, which at the moment are not yet commercially deployed or standardised technologies.
Despite the many unknowns, innovations to improve technology performance and lower cost can also support biodiversity or coexistence with fishing: larger WTGs, smaller mooring footprints and strategic array configurations can increase the allowable area for fishing to continue; taut mooring systems can also minimise seabed contact that damages benthic habitats; innovative installation and O&M activities (e.g. onsite major component replacement) can reduce the number of vessel trips; innovative components can lower carbon footprint or attract marine life. The requirements for engineering robustness and cost competitiveness are thus not at odds with environmental sustainability. A holistic approach is key to ensuring that these issues are all balanced in a project’s final design.
Finally, tackling the environmental impact of floating wind is a microcosm of the challenge our human societies face in understanding complex marine ecosystems and managing their services. Therefore, this paper synthesizes the relevant issues on regulation, spatial planning and environmental research to support the sustainable growth of our sector.
There is a unique opportunity at this stage of our industry, where large-scale projects are in early development or waiting to tender, to avoid negative impacts as much as possible. This can be achieved with MSP-informed site selection that maximises coexistence with the fishing industry and ecologically sensitive areas, amongst other aspects. It can also be supported by tender requirements that incentivise the incorporation of mitigation measures in project design. As for the projects already in the development phase, there is a chance to take advantage of early-stage design flexibility to minimise environmental impacts and consenting risks. Meaningful stakeholder engagement – with the fishing industry, scientists, coastal communities and more – is essential throughout these processes to develop effective, evidence-based mitigation measures.