Q. Kvod Horav Shlit'a. Can one use the threads of old discarded Tzitzis as wicks for Chanuka candles? Is it even recommended to use them as wicks?
A. Talmud Suka (51a) teaches that it was customary to use old and discarded pieces of holy clothing from the Cohanim that were used during the Avoda in the Beis Hamikdosh as wicks for the lights of the Simchas Beis Hashoeva. It is also customary to save and use the Lulav, Hadassim and Arovos that were left over after Sukos for burning the Chometz during Erev Pesach.
See Rema (664: 9) that we save used Arovos and use them to bake matzos. The reason mentioned (Talmud Shabbos 117b) that RavAmi and Rav Asi would make a meal of the bread that was used for an Eiruv, stating since it was used for one mitzva, let us use it for another.
It would therefore seem reasonable to use the discarded threads of Tzitzis as wicks.
An important issue is if the treads made of wool are proper material for wicks. Regarding Shabbos lights Shulchan Aruch (O.H. 264: 1) rules they should not be used as the flame flickers. Yet for Chanuka lights they are permitted. (See Shulchan Aruch 673: 1). Some maintain that they can actually be treated for proper burning.
Horav Shlomo Miller's Shlit'a opinion is that if indeed they light well they can be used.
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu Shlit'a.