Our neighbor which is an old woman is collecting cartons around the community and I think she sells them in a junk shop afterwards. As we always buy tray of eggs every week I keep the trays and when I saw her outside I gave it to her. I do not throw them immediately at the garbage site.
Egg carton has a lot of usage one of them is for soundproofing, I remember when we are still in college our English instructor asked us to bring egg carton for the language room, the egg carton will served as soundproofing the room. The cartoon was taped around the room that made the room so dark and cold.