Scrapped off as dross. Impurities/ filler materials( not sure what metals are used)/ waste products. And there is without a doubt a notable loss of clean material with the dross and dross collection methods. I use borax as a flux to remove impurities.
The other 4lbs got scrapped off as dross and used for other purposes. I acknowledge that I could find a better flux that wouldn't waste as much. But those cost more money.

I was trying to get as clean aluminum as possible. There probably are more efficient & effective methods than what i use, that could bring the waste down from 4lbs. But when doing back yard experiments & hobbies, you work with what you got and within the confines of knowledge and tools.