Life cycle assessment of circular economy strategies for high-strength connection bolts in wind turbines

Wind turbines are an important element of renewable energy systems, but their manufacturing requires significant amounts of materials such as steel, copper, aluminum, rare earth metals, fiberglass, and concrete, with considerable environmental impacts. One approach to reduce the environmental impacts of wind turbines and their components is the application of circular economy strategies. This study focuses on high-strength connection bolts, specifically M36 threaded steel bolts with a length of 660 mm. A comparative life cycle assessment is conducted to analyze the environmental impacts of two scenarios: recycling all bolts at the end of the wind turbine’s life cycle, and reusing some bolts after inspection. The product system is modeled in openLCA, where the processes of the foreground system are linked to the Ecoinvent database in the background system. For life cycle impact assessment, the ReCiPe 2016 method is applied, focusing on climate impact. Results show that after five life cycles, reusing bolts reduces the climate impact by 48%, compared to a 42% reduction through recycling alone. Sensitivity analyses reveal that the potential for impact reduction through reuse is primarily driven by the achievable reuse rate, while factors such as production technology, electricity mix, and transportation distances play a smaller role.