Question:What are the halachot of treatment of bread at the end of a meal?
Answer:There are clear halachot in the gemara (Berachot 50b; 52b) and poskim (Shulchan Aruch, Orach Chayim 171, 180) regarding "respect" due to food in general and especially bread. Two related issues are involved: not causing food to be wasted; not degrading food.
First we shuld mention that if one plans things as he or she should, there should little waste of sizable pieces of bread (or other foods). Leftover bread can be frozen, used for breadcrumbs (while avoiding meat/milk issues), or left for birds. Where this is difficult is at semachot, where there can be half-eaten rolls, etc.
One is not allowed to involve food in non- eating, in a way that it is likely to become soiled and become unappetizing (Shulchan Aruch OC 171:1). It is forbidden to throw any food that could get soiled upon falling and to throw bread even if it will not become soiled, due to bread’s extra importance (ibid. - see Beit Yosef, ad loc.). The gemara (Berachot 52b) explains Beit Shammai’s opinion that one should clean the eating area before washing with mayim acharonim so that the water not fall on and ruin the food. Beit Hillel is not concerned because people will know to remove k’zayit-sized pieces of bread. We are not concerned about smaller pieces, as Rabbi Yochanan says these can be destroyed. Seemingly then, sizable pieces are due respect, while small ones are not, as the Shulchan Aruch (OC 180:3-4) assumes.
However, the matter is complicated. The gemara in Shabbat (143a) says in the name of Rabbi Yochanan that one may not destroy even pieces smaller than a k’zayit. The gemara in Chulin (105b) also says that not being careful with small pieces of leftover food makes one susceptible to poverty. Tosafot (Shabbat 143a) says that our text in Shabbat, which follows Rashi, is incorrect, as the gemara in Berachot says that one is not required to care for small pieces. On the other hand, Tosafot (Berachot 52b) says that even if there is no prohibition, disgracing small pieces could cause poverty. The Magen Avraham (180:3) distinguishes based on different types of lack of care. One is not required to preserve small pieces; however, he may not disgrace them, e.g., by having people trample them. Water falling on them and making them not usable is not a disgrace. Bigger pieces must not even get soiled by water. The Pri Megadim (ad loc.) claims that according to the Rambam, there are no halachic limitations on small pieces, although perhaps there is a danger of poverty.
Even regarding big pieces, if one has decided not to eat them and there is no issue of not wasting them, what should one do with them? Presumably one should discard them without disgracing them, but what is considered a disgrace? Is putting them in the garbage, the normal place to discard things, a disgrace? Every written source I found on the topic (see V’zot Haberacha, p. 16; Etz Hasadeh 19:4; Rav E. Melamed - online) said (without classical sources) that one must put k’zayit -sized pieces in a bag before throwing them into the garbage, and many people, especially in Israel, are careful about this.
Is there any explanation for at least most of the American community within which I grew up, who are not careful about this? We have mentioned in the past (Beshalach 5768) that Rav Yisraeli’s ruled that one can put food with the sanctity of Shemitta in a bag before throwing in the garbage even together with foods without sanctity, as long as those other foods are not spoiled. Touching and even getting a little soiled by other foods before being thrown into the garbage dump may not be a disgrace. One could claim, then, that most kitchen garbage bins contain bags in which there are various leftover food and disposable matters; thus, putting bread in there may not be a disgrace. However, the easier position to justify, in regard to halacha and avoiding poverty, is to put bread leftovers (at least, bigger pieces) that cannot be salvaged, in a separate bag before putting it in the garbage.
58 - Publicizing a Sin as Part of Repentance
59 - Treatment of Leftover Bread
60 - Delay Between Birkat Kohanim