Gachiakuta

Teenage Rudo is one of the hated "Tribesfolk" who lives in the slums of The Sphere – a partitioned society floating high above the clouds. Not only does he belong to a socio-economic underclass oppressed by the rich, wasteful, and cleanliness-obsessed city folk, his peers look down on him for being the son of a deceased murderer. When he's framed for the murder of his foster father Regto, Rudo is thrown down from The Sphere into The Pit, an enormous garbage dump from which no one has ever returned. <em class=de-emphasized>(from manga)</em>

Synopsis from Anime News Network