Scientists from Kaunas University of Technology (KTU) and the Lithuanian Energy Institute suggested a technique for recycling wind turbine blades. They managed to break the composite materials into their basic parts, i.e., — fiber and phenol using pyrolysis. The researchers state that the extracted materials can be used again, and the method is essentially waste-free.
Dr. Samy Yousef, a researcher at KTU Faculty of Mechanical Engineering and Design. Image Credit: Kaunas University of Technology.
Wind turbine blades composed of glass fiber-reinforced polymer (GFRP) laminate composites have a lifespan of up to 25 years. Once they wind up in landfills — GFRP is said to be hard-to-decompose. This has become a real issue for the renewable energy sector.
It is projected that wind turbine blades make up 10% of fiber-reinforced composite material waste in Europe. Scientists assert that by the year 2050, wind turbine blade waste will grow to approximately two million tons worldwide. With a number of countries prohibiting composite materials from being dumped in their landfills, recycling the old wind turbine blades becomes a challenge that scientists globally are attempting to solve.
The aim of cutting global greenhouse gas emissions to close to zero by 2050 has been voiced several years ago. Since then, more and more countries have been committing to the net-zero goal by investing in renewable energy resources, including wind energy.
Dr. Samy Yousef, Researcher, Faculty of Mechanical Engineering and Design, Kaunas University of Technology
“However, the recycling of the wind turbine blades, which are as long as a football field, very sturdy and include plastic, is the main problem. Without a feasible solution to it, we cannot say that wind energy is fully sustainable and environmentally friendly,” Dr. Yousef added.
Aiming to resolve this challenge, the team headed by Dr. Yousef has carried out many experiments involving the breaking down of GFRP into its basic parts.
Waste-Free Conversion
As a result of its shaping simplicity, strength and low production costs, GFRP composites are employed for a host of purposes — for maritime vessels, car manufacturing, construction, oil and gas production, sporting goods and more. Wind energy, aircraft and electronics are among the sectors that use the majority of GFRP, with the international demand increasing yearly by 6%.
GFRP composites used for many industries including wind turbine blades manufacturing are either thermoset or thermoplastic. In either case, they roughly consist only of two components— fibre and resin (in some cases with different micro or nanoparticle additions). As for the fibre, it usually is carbon fibre or fibreglass (the latter is cheaper).
Dr. Samy Yousef, Researcher, Faculty of Mechanical Engineering and Design, Kaunas University of Technology
While conducting the experiments, the researchers applied pyrolysis (in presence of zeolite catalysts and in the absence) to diverse batches of composites — fiberglass thermoplastic and fiberglass thermoset — and assessed the extraction of phenol (the key component in the making of phenolic resins and the production of nylon and other artificial fibers) in each case.
Next, they were examining the rudimentary raw materials from each batch. The scientists also measured the impact that the additive nanoparticles (e.g., carbon black) can have on the yield of beneficial parts.
Though the yield of the components taken out during pyrolysis varies based on the temperatures used, the proximate measurement showed that in all the cases many volatile compounds (up to 66%) and fiber residue (approximately 30%) were extracted. The incorporated fiber nanoparticles (graphene and carbon nanotubes) raised the yield of phenol.
The volatile components are basically phenol, which can be used for further production of resin, and the fibre residue can have numerous applications after purifying it chemically— for fibre-reinforced concrete, polymer composites, fibre flooring. Our method is virtually waste-free with some small emissions, which is standard in this kind of conversion operation.
Dr. Samy Yousef, Researcher, Faculty of Mechanical Engineering and Design, Kaunas University of Technology
Needs a Real Wind Turbine Blade to Continue Research
The experiments were carried out using the samples made at a lab that had compositions akin to those used for manufacturing wind turbine blades, and not the wind turbine blades per se. Thus, Dr. Yousef observes that there is a need to measure the effect of the paint, that the real turbine blades are coated with, to the outcomes. However, he feels that it will not be significant.
“We would of course be happy to receive a worn-out wind turbine blade, which is no longer usable, and to conduct our experiments with the samples obtained from the real object,” says Yousef.
Presently, the researchers are developing a model, which would facilitate scaling and measuring the wider environmental and economic effects of the results.
This research is one of the many carried out by the same team, which concentrates on the practical applications of the theory of the circular economy. The year before, their experiment of lint microfiber conversion into energy garnered extensive global attention.
We are developing research in numerous topics related to climate change, extracting of clean energy (H2 and CH4) using membranes technology, and transition to the circular economy as these topics are closely related to the future of our planet.
Dr. Samy Yousef, Researcher, Faculty of Mechanical Engineering and Design, Kaunas University of Technology
Journal Reference:
Yousef, S., et al. (2022) Catalytic pyrolysis kinetic behaviour of glass fibre-reinforced epoxy resin composites over ZSM-5 zeolite catalyst. Fuel. doi.org/10.1016/j.fuel.2022.123235.