Q: Dear Rabbi, After Pesach Seder are the remainder of the pieces of matzoth eaten at the seder considered to be a used hefetz shel mitzvah, that has to be disposed accordingly and not thrown in the garbage even if they are small pieces less than a kezait?

How about the remainder Lechem Mishne Hallah every Shabath?

A: A hefetz shel mitzvah would be an object that was used for the performance of a mitzvah and carries certain restrictions in its disposal such as the discarded tzitzith strings from a talith. On them, the Remoh (O.C. 21,1) advices that they should not be thrown into the refuse with the common waste, but rather removed in honour into a genizah if possible. The talith however, does not require such treatment, but it should also not be disposed off disgracefully into the garbage. While still in use, the talith should be treated only in an honourable way (ibid 21,2).

Horav Shlomo Miller Shlit”a pointed out that in the case of Pesach matzah, the hefetz shel mitzvah would be the matzah that was already eaten but not the remainder. This unused matzah would only be restricted to the normal prohibitions of bizui ochlin, which don’t affect pieces less than a kezait, even on bread. (It is still prohibited to tread with your feet on the crumbs on the floor, Mishnah Berurah 180, 10).

As a hidur mitzvah only (enhancement of the mitzvah) it would be better to collect those pieces and place them inside a plastic bag prior to their placement in the refuse bin or to use them in any other honourable way.

Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit”a