 "Terumah" and "terumat ma'aser" must be discarded in a manner consistent with their sanctity.The reason for discarding in such a manner is that the set-aside produce is still considered "mikudash" or sacred.While dedicated offerings cannot actually be offered in their traditional form in the absence of the Temple, because one must consume "terumah" and "maaser sheni" in a state of purity, they also cannot be used for mundane purposes.