spent grain vs residue

spent grain and residue both are nouns.

Word	Noun	Adjective	Verb	Adverb
spent grain	Yes	No	No	No
residue	Yes	No	No	No

As nouns, residue is a hypernym of spent grain; that is, residue is a word with a broader meaning than spent grain:

spent grain: the residue of malt and grain which remains in the mash-kettle after the mashing and lautering process.
residue: matter that remains after something has been removed

spent grain (noun)	residue (noun)
the residue of malt and grain which remains in the mash-kettle after the mashing and lautering process.	something left after other parts have been taken away
	matter that remains after something has been removed