Reference: Fataawa Noor ‘alad-Darb – Question No.5968, Page 394, Volume 11
Question: What is the ruling regarding throwing away leftover food and drink?
Response: As for that which cannot be eaten, such as orange peel, apple [core] and banana skin – and that which is similar, then there is no harm [in throwing it away]; that it is because it is not sacred in itself. As for that which can be eaten, such as leftover bread, sauce and the like, then that is not to be thrown away in the rubbish; if it is necessary to throw away, then it should be put into a plastic bag [by itself], so that those who collect the rubbish know [it is food].
 How food waste is recycled