What is done with used wind turbine blades?

Wind turbine blades are made of composites, fiberglass or carbon fibre, strengthened together with polymeric resin. They are designed to withstand harsh natural conditions. Strong winds, rain, frost, and ultraviolet radiation from the scorching sun. This is definitely not a material that can be easily destroyed. But even so, they have a lifespan of about twenty years. After that time, the wind turbine usually retires.

Sometimes the old blades are just replaced with new, longer ones with better aerodynamics and are therefore more efficient and sometimes the whole plant is scrapped. The concrete base is ground up and used for example, as a base for road construction. The steel column is recycled. The nacelle with the generator is dismantled and its parts are sent for recycling or landfill. The copper from the rotor windings, for instance, is a valuable material.

But what about solid blades? They are usually just cut into shorter pieces and covered with soil in a giant wind turbine blades graveyard. At best, they're chopped into sections so they don't contain air-filled cavities. It is estimated that by 2050, up to two million tonnes of blades would need to be "buried" in this way every year worldwide.

Methods are therefore being developed to recycle the spent blades or find other uses for them. For example, they can be crushed and used as a feed material for cement production. Normally, cement is made by burning a mixture of crushed limestone and clay in a kiln. The resulting material, called clinker, is mixed with gypsum to form cement. The silica-rich fiberglass fibres of the crushed blades can replace some of the limestone, and the resin contained in the blades burns well, saving on fuel too. In theory, burning one 6.3 tonne blade saves 4.5 tonnes of coal, 2.4 tonnes of silica and 1.7 tonnes of limestone.

Methods for the disposal of blade grit by pyrolysis are also being developed. An alternative is to use whole blades or large parts of blades as bridge structures, pedestrian shelters or children's climbing frames and slides.