My son brought me a pamphlet produced by Yeshiva Sh'or Yoshuv (Far Rockaway, NY) that discussed the laws of the 4 minim. (If I can locate an online copy, I'll edit in a link.)
Near the end of the pamphlet, it discussed some special laws of how to handle shmitah (Sabbatical) year etrogim after Succot. It said that it may not be disposed as long as it is in an edible state. It must either be eaten, or left to rot until it is inedible.
My question is, must it be used just as food or would anything useful that doesn't just dispose of the etrog be permitted? E.g. I see many people stud the etrog with cloves and use it for havdalah besamim. Would either that be permitted or using the etrog rind into making a deodorant spray for your bathroom or furniture polish be permitted with the shmittah etrog?
Related question - How about if I just placed the etrog itself into my bathroom to deodorize it, somewhat? (I've never tried this, but, as the etrog starts to rot, it does emit a rather strong lemony scent, actually.) Is this OK, or considered disrespectful?