[Burning in Hell]

My guess is that we would create a system where those deemed "unworthy" (probably insane people or people suffering from severe mental disorders, or perhaps criminals like you've said) would serve as breeding stock and would be kept in something similar to farmhouses where they would be slaughtered as soon as their brains would attain maximum size. Their bodies would then probably be re-cycled in one way or another...

Of course, many would rather starve to death, but some would prefer to survive whatever the cost.