Can I reuse 3D printed parts?
I ground up some prints and extruded them into new filament. The quality of recycled filament is not very high so I would not recommend it. 

As pointed out earlier, the shredded bulk material you would create from your old prints would cost more in time and energy to produce than buying new raw material (pellets, not filament), and you still need to extrude it into filament to be able to use it in a printer.