<p>Will a 3D scanner capture internal details within an enclosure?</p>
<p>I'm contemplating buying a 3D scanner, but they're pretty expensive so I'm looking for advice on whether they will actually be useful for the projects I have in mind. So with the picture below as an example, could I expect to generate a usable STL file by scanning this?</p>
<p><a href="https://i.stack.imgur.com/iYiDz.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/iYiDz.jpg" alt="Object" /></a></p>

You can certainly get large nozzles, but the material for extrusion still needs to be consistent.  So any chunked plastic would have to be melted and that will produce an erratic flow at the extruder.
By reforming your shredded plastic into a consistent string of filament, then the printer has a steady supply of material to use.  There are already filament extruders for the small shop, but they're still expensive for the home user.  The main problems are getting consistent thickness of filament, and minimising contaminants.  Also colours tend to be lost and muddied.  These might be economical if you have a print farm and are consuming a spool a day on average.
On a large scale, there are "3d printers" that can place a special quick-drying concrete and produce small buildings as homes in a matter of days.  However they're fed a special mixture of smooth cement and accelerators to set the concrete ready for the next layer.