The energy generated by wind turbines may be viewed as clean and green but decommissioned turbine blades are not. With blades spanning up to 260 ft and weighing an average of 36 tons, old or broken blades pose a disposal dilemma problem, with landfilling the most commonly selected option. Prospects for recycling these renewable energy components were recently explored by the Electric Power Research Institute and the American Composites Manufacturers Association.

Up to 50,000 tons of blades per year are projected to enter the end-of-life stream in the U.S. by 2023. The bulk of the blades is composed of fiber-reinforced composite, which presents size reduction challenges (either glass or carbon fiber). The use of pyrolysis, burning in a cement kiln and grinding blades so particles can be used as filler were examined as feasible end-of-life routes.

Mechanically size-reducing the composite and using the resulting material as a filler or combining the low-Decommissioned wind turbine blades are typically cut up and transported by truck for solid waste disposal. Source: Derek Berry/National Renewable Energy LaboratoryDecommissioned wind turbine blades are typically cut up and transported by truck for solid waste disposal. Source: Derek Berry/National Renewable Energy Laboratoryvalue end-product with other materials for use in decking, insulation and building panels, is hampered by market and economic challenges. Grinding can create a fine dust irritant, and shards pose handling problems. A large decline in the mechanical properties of the recycled material is also noted.

Recycling using the cement kiln eliminates the need for landfill, recovering both energy and raw materials needed to produce cement. The inorganic glass fiber is reprocessed into cement and the resin provides an energy offset. Barriers to widely deploying this recycling option include a loss of material characteristics and the need for a high volume of composites to make the additional processing economical, as the composite portion of the feedstock must be combined with other materials to provide the required consistency and BTU.

The pyrolysis process generates clean fuel gas to heat the primary reactor and yields char with recoverable carbon fiber and glass fiber reinforcement for re-use in other polymer systems. This option offers more attractive economics for recovery of carbon fiber than for glass fiber, but it requires more technology development and a higher initial investment than the other options.

Recommendations for improving the economics and logistics of options for wind turbine blade management include continued development of a commercial-scale facility for front-end processing of composites scrap for use in recycling, cement kiln feedstock and/or pyrolysis demonstration.

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