User blog comment:Darknesslover5000/What happen to Souls who are by Hollows?/@comment-893506-20100510035844

I don't think it was ever stated what happens when a being other than a Quincy or a Shinigami kills a Hollow/Arrancar. Theoretically, what Lemursrule says may be correct, but all-in-all, it was never specified what would happen to Hollows or Arrancar if killed by Hollow-ish beings (Grimmjow, Chad via his powers, Nnoitra, etc.) or other types of powers (Orihime, the Bounts, etc.). We only know that if a Hollow is killed by a Shinigami's Zanpakuto, it is purified and sent to either the Soul Society or Hell (this depends on the nature of the soul in question BEFORE it was a Hollow), and that if killed by a Quincy, Hollows are destroyed completely.

And I think we may have it stated somewhere here what happens with the souls that Hollows eat, but once again, I think Lemursrule's theory about that is correct.