If physics has the law of the conservation of energy, then Judaism has the law of the conservation of holiness. We believe that once something is imbued with kedusha, sacredness, it remains there. For example, any item that is used for a holy purpose must be disposed of respectfully, even if the object is worn and tattered. The kedusha results from something’s purpose, not its appearance.
Many are aware that religious objects like a Torah scroll, tefillin and tallit must be buried rather than thrown out, but even objects that are used with these things must be treated with respect due to their proximity to holiness. Therefore the mantle that surrounds a Torah, as well as a tefillin bag must also be disposed of properly, in a geniza, a storage area for religious objects.
Even perishable items can become holy as well. On Sukkot, the Lulav, Etrog, and s’chach (branches used as the roof of the sukkah) all contain holiness because they were used for the mitzvot of the holiday. One should not merely throw these items in the trash, but you can’t put them in the geniza either.
The simplest way to dispose of these things, according to Jewish tradition, is to let them sit for a while until they decay and then respectfully place them in the garbage, or compost. Some people, however, like to reuse these objects to do other mitzvot.
Each year in my family we save our Lulav and let it dry out until Passover when we use it as the kindling to burn the hametz, bread products, we have removed from our house. There is something beautiful about taking an object that helped you perform a mitzvah during one holiday and letting it help you do a mitzvah at the next holiday.
Every year I struggle coming up with something to do with the Etrog. After past holidays I have tried to make Etrog jam with little success. Either it was too bitter or the consistency was off. This year I resolved to make Etrog-infused vodka until I searched for a recipe online.
That is when I discovered that most Etrogs are not grown to be eaten. In order to produce the perfect fruit without any blemishes that can be used to fulfill the mitzvah of gathering the four species, farmers toss tons of pesticides on their Etrog trees. The chemicals cannot be washed off because they get absorbed into the skin of the fruit so unless you can find organic Etrogs, it’s probably best to avoid eating them.
This year we are going to turn our Etrogs into spice holders for Havdalah by inserting cloves into the skin. As the fruit dries its scent combines with the cloves to produce a beautiful smell, and the best part about it is we are reminded of the beauty of Sukkot each week as we say goodbye to Shabbat.