Discussion is related to Conservation. Conservation is the opposite of Waste. 
Separation is related to Put. Put is related to Placement. Placement is a synonym of Arrangement. Arrangement is a synonym of Organization. 
Discussion <--RelatedTo--> Conservation <--Antonym--> Waste 
Separation <--RelatedTo--> Put <--RelatedTo--> Placement <--Synonym--> Arrangement <--Synonym--> Organization 