Researchers propose a method for recycling wind turbine blades

A group of researchers from Kaunas University of Technology (KTU) and the Lithuanian Energy Institute have proposed a method for recycling wind turbine blades. Using pyrolysis, they broke the composite materials into their building blocks, i.e. phenol and fibers. According to the scientists, the mined materials can be reused and the process is virtually waste-free.

Wind turbine blades made from laminated fiberglass reinforced polymer (GFRP) composites can last up to 25 years. After that they end up in landfills – GFRP is known to be difficult to break down. This has become a real challenge for the renewable energy industry.

It is estimated that wind turbine blades represent 10% of fiber reinforced composite material waste in Europe. Researchers say that by 2050, wind turbine blade waste will reach around two million tonnes worldwide. As many countries ban composite materials from their landfills, recycling used wind turbine blades is becoming a challenge that researchers around the world are trying to solve.

“The goal of reducing global greenhouse gas emissions to near zero by 2050 was announced several years ago. Since then, more and more countries have committed to zero net by investing in renewable energy resources, including wind power.However, recycling wind turbine blades, which are as long as a football field, very sturdy and contain plastic, is the main problem. feasible solution, we cannot say that wind power is fully sustainable and environmentally friendly,” says Dr. Samy Yousef, researcher at Kaunas University of Technology (KTU), Faculty of Mechanical Engineering and design.

Aiming to address this challenge, the research group led by Dr. Yousef performed several experiments involving the breakdown of GFRP into its building blocks.

Waste-free conversion

Due to its strength, ease of forming and low manufacturing costs, GFRP composites are used for multiple purposes: automotive, marine vessels, oil and gas production, construction, sporting goods, etc Aerospace, wind power and electronics are among the industries using GFRP the most, with global demand growing at 6% per year.

“GFRP composites used in many industries, including the manufacture of wind turbine blades, are either thermoset or thermoplastic. In either case, they consist of roughly only two components – fiber and resin ( in some cases with different additions of micro or nanoparticles). As for the fiber, it is usually carbon fiber or fiberglass (the latter is cheaper)” explains Dr Yousef.

During the experiments, the research group applied pyrolysis (in the presence of zeolite catalysts and without) to different batches of composites — thermoset fiberglass and thermoplastic fiberglass — measuring the extraction of phenol (the main component in the production of phenolic resins and the manufacture of nylon and other synthetic fibres) in each case. After that, they would analyze the basic raw materials of each batch. Researchers also evaluated the effect that additive nanoparticles (such as carbon black) may have on the yield of useful components.

Although the yield of the extracted components during the pyrolysis differs according to the applied temperatures, the approximate measurement revealed that in all cases the numerous volatile compounds (up to 66%) and the fiber residues (about 30%) were extracts. Added fiber nanoparticles (carbon nanotubes and graphene) increased phenol yield.

“The volatile components are mostly phenol, which can be used for further resin production, and the fiber residues can have many applications after their chemical purification – for fiber-reinforced concrete, polymer composites, floor coverings Our method is virtually wasteful – zero emissions with low emissions, which is standard in this type of converting operation,” Yousef explains.

Needs a real wind turbine blade to continue research

The experiments were conducted using the samples prepared in a laboratory that had compositions similar to those used to make wind turbine blades, not the wind turbine blades themselves. Therefore, notes Dr. Yousef, it is necessary to assess the effect of the paint coating, which the real turbine blades are coated with, on the results. However, he believes that this will not be significant.

“We would of course be happy to receive a worn wind turbine blade, which is no longer usable, and to conduct our experiments with the samples obtained from the real object,” says Yousef.

Currently, the research group is creating a model that would scale and calculate the broader economic and environmental impact of the results.

This study is one of many conducted by the same research group, which focus on practical implementations of circular economy principles. Last year, their experiment in converting fluff microfibers into energy garnered widespread international attention.

“We develop research on many topics related to climate change, clean energy extraction (H2 and CH4) using membrane technology and the transition to the circular economy, because these topics are closely tied to the future of our planet,” says Dr Yousef.

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