Looks like a business opportunity for someone to me. Imagine if you created a business that breaks down that fiberglass to a size that landfills or recycles could handle. You'd be the only one in it for at least a couple years and could charge whatever you wanted especially if you made a deal with the landfills so they turned away full sized blades.
Again, ground up fiberglass and components are an excellent carcinogen (cancer causer) and that's about it.
Once the dozer or packer rolls over them they will be completely flat and without releasing very much debris into the air to get breathed in.
Yea they will probably never break down to any inert form so years from now our future generations will be wondering how in the heck to deal with the pile of crud that we left behind.
"Fiberglass is nearly impossible to recycle, yet we must be careful to handle it properly and not let its toxins collect in landfills".
"The disposal of spent blades is a growing problem that tends to be ignored ... Crushing a blade yields about 15,000 pounds of fiberglass waste, and the process creates hazardous dust."