Recycling large wind turbine blades is no easy task because they are made of strong materials that can withstand decades of wind and rain erosion. Researchers at Washington State University have developed a way to exploit these properties, using discarded leaves to create strong and durable plastics without the use of harsh chemicals.

Wind turbine blades are huge, and those produced in the 1990s are now obsolete and difficult to recycle

The challenge was breaking down the solidified lightweight material used in many vintage blades from the 1990s: glass fiber reinforced polymer (GFRP). But in research published this month in the journal Resources, Conservation & Recycling, the team found another way. They explained:

"For this work, we didn't need to completely break down all the bonds and push the reaction to completion," explains Baoming Zhao, a co-author on the paper. "As long as we can break the cross-linked network into smaller pieces and they can be melt-processed, we can compound it with nylon and get a new composite material."


Left: Wind turbine blade scrap. Center: Treated and dried glass fiber reinforced polymer (GFRP) for a wind turbine blade. Right: Injection molded plastic containing 70% recycled GFRP

The team's approach involves cutting discarded turbine blades into two-inch (about 5 centimeters) pieces and then crushing them into pieces. The pieces were soaked for two hours in a mild solution of zinc acetate, a low-toxic organic salt, in pressurized hot water.

The process recycles intact fiberglass and resin, which is then mixed with molten thermoplastic (a material commonly used to make milk bottles) and nylon plastic to produce higher-grade composites. Composite recycled nylon plastic is more than three times stronger and eight times stiffer.


Turbine blades are cut into chunks, shredded into pieces, treated with solutions to recover fibers and resins, and then melted down with thermoplastics to produce a stronger material

The researchers' approach has several other benefits. First, the zinc acetate catalyst can be simply filtered and recycled for reuse. Second, the process can be applied to other common plastics, such as polypropylene, which is used to make products such as food containers, stationery and toys.

This could make used turbine blades very valuable to plastic recycling plants, while also allowing for a relatively environmentally friendly process. The researchers' next steps are to reduce the pressurization requirements of the method, making it easier to apply on a large scale, and to explore the development of recyclable materials that could be used to make new turbine blades.


Wind turbine blades made from composite materials to withstand decades of harsh weather conditions