body waste vs faeces

body waste and faeces both are nouns.

Word	Noun	Adjective	Verb	Adverb
body waste	Yes	No	No	No
faeces	Yes	No	No	No

As nouns, faeces is a hyponym of body waste; that is, faeces is a word with a more specific, narrower meaning than body waste:

body waste: waste matter (as urine or sweat but especially feces) discharged from the body
faeces: solid excretory product evacuated from the bowels

body waste (noun)	faeces (noun)
waste matter (as urine or sweat but especially feces) discharged from the body	solid excretory product evacuated from the bowels