The challenge of wind turbine blade disposal has captured attention around the world. North Dakota alone has more than 1,500 turbines using 4,500 blades. Many wind blades will soon be upgraded or retired, and finding secondary value will help offset costs for decommissioning and disposal while setting the state ahead of the curve in developing a blade-recycling infrastructure.
A team at the EERC led by Joshua Strege, Principal Process Engineer, has received State Energy Research Center (SERC) funding to address the need for further research into the reuse, recycling, or repurposing potential of wind blades in North Dakota. The goal of this project was to determine the feasibility of separating blades by material type for more efficient reuse.
Depending on what they are made of, different sections of a wind blade have very different properties. For this reason, the ideal process for repurposing old wind blades might be to separate the blade by material type so that each can be optimally reused. This project helped to identify the key properties of each material, the best methods for cutting and grinding each material, and the end applications possible for each material.
Three types of material were cut from two decommissioned wind blades in different conditions: solid laminate (thick layers of fiberglass), sandwich (balsa wood or foam sandwiched between thin layers of fiberglass), and bonded (two pieces of solid laminate bonded together with rigid adhesive).
The recovered blade sections were first scanned using existing technology to look for material boundaries. It was possible to find the boundaries using a portable handheld scanner. If decommissioned blades could be scanned in the field, then it would be possible to find material boundaries and cut blades into different material types before shipping. This would help to reduce transportation costs and to reuse each material type more optimally.
Solid laminate varied greatly in strength. Very damaged or aged solid laminate was among the weakest blade material tested. Although the strongest of the solid laminate would be a good candidate for reuse in structural applications, some screening would be needed to separate solid laminate by quality for this to be a commercial possibility.
Sandwich material that was laminated and made with balsa wood ground easily, while sandwich material that was well-consolidated and made with foam core required more time and energy to grind. The ground sandwich material combusted quickly and had heating values and ash chemistry suitable for direct use in U.S. cement kilns. However, the foam core contained high levels of chlorine that could limit the maximum feed rate in kilns or other combustion applications. Sandwich areas are engineered to be lightweight, and they carry less load than the solid laminate regions, making them a poor candidate for structural applications after separation.
Bonded sections from the trailing edge were challenging to grind but also relatively weak. This layer has also a thick adhesive which burns poorly and splits easily. These properties make the bonded sections of a wind blade a poor candidate for use as either a fuel or a structural element susceptible to bending. Further study would be needed to determine what potential end uses might exist for the bonded sections of decommissioned wind blades.
Separating the wind blade components would likely improve the ability to reuse, recycle, or repurpose the various materials.