KTU propose new method for wind turbine blade recycling

The KTU researchers said that as wind turbine blades reach the end of their operational lifespan, the issue of disposal becomes a serious concern.

Made from composite materials such as layers of fibreglass or carbon fibre reinforced with epoxy or polyester resin, the blades can be used for 20-25 years. While these materials ensure the strength, lightness, and stiffness of turbine blades, the researchers said they also complicate the recycling of the equipment.

In 2022, Dr Samy Yousef, a researcher at KTU’s Faculty of Mechanical Engineering and Design, and a team of researchers from the Lithuanian Energy Institute, began experimenting with different ways to recycle wind turbine blades.

The experiments included breaking down old composite materials, such as glass fibre-reinforced epoxy resin composites, by using the thermochemical treatment process of pyrolysis along with a ‘special’ catalyst.

The researchers said the aim was to separate valuable components for reuse and recycle old composite materials into useful energy, though limitations in the availability of samples interfered with the identification of the actual recycling outcome.

Last year (2023), Dr Yousef and his team continued their experiments on real wind turbine blade fragments supplied by Danish company European Energy A/S.

The researchers found that unsaturated polyester resins are predominant in the production of wind turbines in the Baltic region due to their cost-effectiveness compared to epoxy resins, and that styrene, a main component of polyester resin, poses significant environmental and health risks.

In a statement, Dr Yousef said: “When disposed of in landfills, [styrene] becomes highly toxic for humans and can cause lung cancer. In addition, styrene can pollute and poison groundwater and soil.

“The main goal of the research was to find a way to extract carbon fibres and resin from old wind turbine blades that are difficult to dispose of because they contain toxic substances and aren’t biodegradable.”

The research team successfully extracted styrene from blades in the form of styrene-rich oil using a pyrolysis reactor. They also recovered and purified fibres, carbon and fibreglass through an oxidisation process, which they said could be a sustainable filler material to enhance the mechanical properties of composite materials.

In addition, the environmental impact of blade treatment using the pyrolysis process was calculated. In conducting the life cycle assessment, the research team found a ‘significant environmental potential’ of blade waste pyrolysis compared to landfill disposal – particularly regarding global warming, stratospheric ozone depletion, and fossil and mineral resource scarcity.

The researchers, however, also emphasised that their strategy still raises certain environmental challenges due to post-treatment processes such as washing and oxidation.

“Results revealed remarkable improvements in various environmental indicators, with enhancements that range between 43–51 per cent. This is a great achievement,” said Dr Yousef. “[But] these issues need to be carefully managed, and only then should future developments take place.”

The study, published in Environmental Research, can be accessed in full here.