[dredmorbius]

And after 4 generations, less than 1% of the original material remains.

   percent remaining = 100 * (r^generations))

Where r is expressed as a decimal 0 <= r <=1.

Even at 90% recovery, over 90% of the original material is lost after 22 generations. The highest recycling rate of any material in the US is lead (mostly from auto batteries). The USGS reports that rate as ~70%, though this may be the amount of recycled material in new production.