Leibniz University

Recycling rotor blades and industrial plastic waste

The Institute for Plastics and Recycling Technology at Leibniz University is launching a research project on mechanical recycling. The goal is to make fiber-reinforced plastics from old wind turbines recyclable.

Hall with technical equipment. — At Leibniz University, researchers are working on new methods for recycling plastics.

Good for the environment, but difficult to dispose of: Wind turbines last an average of 20 years, after which they must be replaced. However, recycling old turbines is difficult. The rotor blades, in particular, pose a problem due to their composition of fiber-reinforced plastics. Other plastic-based waste, such as trunk liners from cars and smaller parts—for example, from healthcare and pharmaceutical applications as well as electrical and electronic applications—cannot currently be recycled, or can only be recycled with difficulty.

Recycling fiber-reinforced plastics

This is where a new research project at the IKK—Institute for Plastics and Recycling Technology at Leibniz University Hannover (LUH)—in collaboration with KraussMaffei Extrusion (Laatzen) comes in; the project launched on July 1, 2023. Under the leadership of Prof. Dr.-Ing. Hans-Josef Endres, the scientists aim to develop a new process to recycle industrial waste from engineering plastic components—that is, from fiber-reinforced plastics and plastic-based composite materials. The Lower Saxony Ministry of Science and Culture is funding the ReKon project with approximately 550,000 euros; the funding period is two years.

Closed-loop recycling

The idea behind the project is that recycled plastics should, wherever possible, be reused in industry in the same sector from which they originated (closed-loop recycling). A trunk liner could thus later be turned back into a trunk liner, or at least into another automotive component. “The quality of a product increases with the highest possible purity and the lowest possible level of contamination in the input material. The pre-treatment steps of sorting, separation, washing, and cleaning therefore play a crucial role,” says Professor Endres. The advantages of having the manufacturer of the original part also handle the recycling are obvious: The exact composition of the plastic and the components is known, making sorting considerably easier. Additionally, transport distances are short, avoiding long-distance shipping with a high carbon footprint. Ultimately, this leads to future generations of components being designed with recyclability in mind. This reduces the consumption of valuable raw materials.

Mechanical recycling methods

There are currently several options for recycling plastics: chemical processes are being used more and more frequently, and recently, solvent-based processes have also come into use. At the IKK, Professor Endres’s team relies on established—though by no means fully developed—mechanical recycling methods. In comparison, these mechanical recycling processes are characterized by significantly lower energy and resource requirements. The principle is simple and can also be applied to other feedstocks, such as textiles: The plastic waste is first shredded. The resulting material is then melted in an extruder using high pressure and high temperatures, cleaned, and finally processed into a type of granulate. This recycled material—fine plastic granules—then forms the basis for new components that can be reused elsewhere.

Focus on materials that have been difficult to recycle until now

The new research project focuses on components in which different plastics and other materials are bonded together in such a way that they can no longer be separated using currently available industrial recycling technologies. This primarily concerns fiber-reinforced plastics from rotor blades, composite materials from the pharmaceutical industry, electronic waste, and the so-called “light fraction” from shredders in the automotive industry, which, despite its high plastic content, is currently considered non-recyclable and is usually sent to incineration.

Increase in plastic waste from industry

The volume of plastic waste in industry is set to increase even further in the future. For example, a new car now contains more than 300 kilograms of plastic, and the EU has set ambitious recycling targets for future vehicle generations in its recently proposed End-of-Life Vehicles Regulation. The number of wind turbines that will need to be recycled in the coming years is also on the rise. A 2022 study by the German Federal Environment Agency estimates that up to 430,000 tons of glass-fiber-reinforced plastics will be generated by 2040 from rotor blades alone.