PFC vs greenhouse emission

PFC and greenhouse emission both are nouns.

Word	Noun	Adjective	Verb	Adverb
PFC	Yes	No	No	No
greenhouse emission	Yes	No	No	No

As nouns, greenhouse emission is a hypernym of PFC; that is, greenhouse emission is a word with a broader meaning than PFC:

PFC: a powerful greenhouse gas emitted during the production of aluminum
greenhouse emission: a gas that contributes to the greenhouse effect by absorbing infrared radiation

Other hypernyms of PFC include fluorocarbon, greenhouse gas.

PFC (noun)	greenhouse emission (noun)
a powerful greenhouse gas emitted during the production of aluminum	a gas that contributes to the greenhouse effect by absorbing infrared radiation