Wind turbine blades could one day be recycled into sweets

Wind power is an increasingly popular form of renewable energy. However, when it comes time to replace the huge turbine blades that convert wind into electricity, disposal is an issue. Now scientists report a new composite resin suitable for making these giants, which could later be recycled into new turbine blades or a variety of other products, including countertops, car taillights, diapers and even gummy bears.

The researchers will present their results today at the fall meeting of the American Chemical Society (ACS).

“The beauty of our resin system is that at the end of its use cycle we can dissolve it and that releases it from the matrix it’s in so it can be used again and again in an endless cycle,” says John Dr. Dorgan, who presented the work at the meeting. “That’s what the circular economy is all about.

Made of fiberglass, wind turbine blades can be half a football field long. Although some companies have found ways to recycle fiberglass into lower value materials, most discarded blades end up in landfills. And the disposal problem is likely to get worse. “Bigger wind turbine blades are more efficient, so companies keep making bigger and bigger ones,” says Dorgan. “Often wind farms will actually replace turbine blades before the end of their useful life because the farms can generate more electricity with larger blades.”

Dorgan and colleagues at Michigan State University made a new turbine material by combining glass fibers with plant-based polymer and synthetic. Panels made from this thermoplastic resin are strong and durable enough to be used in turbines or automobiles. The researchers dissolved the panels in fresh monomer and physically removed the glass fibers, allowing them to reprocess the material into new products of the same type. Importantly, the redesigned panels had the same physical properties as their predecessors.

In addition to new wind turbine blades, the new resin can be used for a variety of other applications. By mixing the resin with various minerals, the team produces a cultured stone that can be transformed into household items such as countertops and sinks. “We recently did a bathroom sink with cultured stone, so we know it works,” says Dorgan. The researchers could also crush the recovered material and mix it with other plastic resins for injection molding, which is used to make items like laptop covers and power tools.

The material can even be processed into higher value products. Degrading the thermoplastic resin in an alkaline solution releases poly(methyl methacrylate) (PMMA), a common acrylic material for windows, car taillights and many other items. Elevating the digestion temperature turns PMMA into poly(methacrylic acid), a super-absorbent polymer that is used in diapers. Alkaline digestion also produces potassium lactate, which can be purified and made into candy and sports drinks. “We recovered food grade potassium lactate and used it to make gummy bears that I ate,” says Dorgan.

Now that the researchers have shown that the resin has the right physical properties for wind turbines, they hope to make some medium-sized blades for field testing. “The current limitation is that we don’t have enough bioplastics that we’re using to satisfy this market, so there needs to be significant production volume brought online if we’re really going to start making wind turbines from these materials,” Dorgan notes.

And is there an “yum” factor in eating candy that was once part of a wind turbine? Dorgan doesn’t think so. “A carbon atom that comes from a plant, like corn or grass, is no different than a carbon atom that comes from a fossil fuel,” he says. “It’s all part of the global carbon cycle, and we’ve shown that we can go from biomass in the field to durable plastic materials and back to food.”