Shevuot 12: Dessert on the Altar

What can be done with an animal designated for offering that is no longer needed for whatever reason (that does not include a blemish to the animal)? For example, if the owner (the one who sinned) died...so he can't carry out the plan for atonement? Several possible solutions are considered. Also, going back to the atonement of Yom Kippur and all the kinds of transgressions it applies to. Including, it seems, sins for which a person did not repent! (as long as the sinner isn't denying God's existence)