We need to start a wind turbine blade recycling company .
Great Idea- how do you start? About all you can do with windmill blades, which generally are a mixed composite of epoxy, balsa, dense wood, fiberglass, and sometimes other plastic, is burn them for heat and then mix the ash with some cement to make it solid enough to handle. A burner for this stuff will require a completely new design to contain the ash, prevent build up inside, and separate the ash.
It will NOT be economical and will require subsidies, in addition to the construction subsidies. Likely the ash will make a useful extender for cheap, non-structural concrete, again with a separate subsidy.