Nowadays, we don’t have a Beis HaMikdash with a Mizbei’ach that needs its ashes to be cleaned off. But we do something similar with holy objects we don’t need anymore.
If you have an old worn out Chumash, Siddur, or pages of the Talmud on which holy words of the Torah are written, it is called Sheimos, and it is forbidden to throw it in the trash. It doesn’t matter whether it was handwritten, printed, or photocopied, they are still holy and deserve burial.
After all, a holy object always remains holy and must be treated with the proper respect.