Glass fiber and glass fiber-reinforced polymers are of interest to engineers for a wide variety of applications, owing to their low weight, high relative strength, and relative low cost. However, management of glass fiber waste products is not straightforward, particularly when it is part of a composite material that cannot be easily recycled. This is especially the case for physically large structures such as wind turbine blades. This chapter deals with the challenges of managing this growing waste stream and reviews the structure and chemistry of glass fiber and glass fiber-reinforced polymers used in wind turbine blades, the separations processes for extracting the glass fiber from the thermoset resin, and end-of-life options for the materials. Thermodynamic evidence is reported and evaluated for a novel end-of-life solution for wind turbine waste: using it as a supplementary cementitious material.