Make different varieties of scrap, depending on where it is.
For instance, scrap armour, scrap engines, scrap machinery etc might be different types. Different sorts could overlap, perhaps. Perhaps scrap fields might occasionally drop bits of ore, making scrapping slightly less reliable than regular mining, but giving occasional lucky strikes.
Different sorts of scrap could offer a variety of routes, though. Different sorts of wreckage, different sorts of sell-points, maybe?