human waste vs excreta

human waste and excreta both are nouns.

Word	Noun	Adjective	Verb	Adverb
human waste	Yes	No	No	No
excreta	Yes	No	No	No

As nouns, excreta is a hypernym of human waste; that is, excreta is a word with a broader meaning than human waste:

human waste: the body wastes of human beings
excreta: waste matter (as urine or sweat but especially feces) discharged from the body

Other hypernyms of human waste include body waste, excrement, excretion, excretory product.

human waste (noun)	excreta (noun)
the body wastes of human beings	waste matter (as urine or sweat but especially feces) discharged from the body