The better question is what gets expelled from black hole mergers?

Nothing is infinite, even if it is a number so large it is beyond a primate’s comprehension. Black holes are using their immense gravity to convert matter into energy and expel it as radiation. A very inefficient process, but absolutely stunning.

All elements heavier than lead were forged by the collision of two neutron stars, as a main sequence star quickly dies after becoming ferrous, as there is no more energy to be gained by fusion of heavier elements, and supernovae rarely form fusion reactions past lead.

That’s mind boggling to try and even fathom… The heavier than lead elements started as super giant stars that turned into neutron stars at death, then later merged with another, to explode its strange matter into the cosmos.

White Holes are a layman’s cop out for misunderstanding the rules of Black Holes.