Q. Is there a source to save the challah separated from dough & to burn it by Biur Chametz before Pesach or should it be burnt asap? Is there an issue if your own oven is used for burning it?

A. We generally sponsor the idea that an object that was used already for the performance of a mitzvah, should be kept and used again for the accomplishment of another. An case in point is saving the used hoshanos branches from Sukos, for burning in the fire when baking matzos (Remoh O.H. 664: 9), or setting aside the challah bread of eiruv tavshilin to be used for lechem mishneh during the Shabbos meals (Mishna Berura 527: 48).

However, we also maintain that one should not keep in his domain for a long period of time, an object or food that is prohibited in use or consumption, as he may forget and transgress. An example is contaminated terumah. (Pesachim 33b), or non kosher meat or animals that a person may have acquired unwittingly (Y.D. 117: 1, see also Tosafos on the beginning of Pesachim)

Horav Shlomo Miller’s Shlit”a opinion is that challah separated from the dough, should not be kept for more than a week prior to being burned. (See also; Shach Y.D. 57: 47 and Chidushey Chasam Sofer – Beitzah 18a).

He also advises to double wrap in aluminum foil the challah to be burned in your own oven. You can burn it then, even while other food is being baked.

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