I personally believe spell ingredients should be disposed of safely, ethically and also how it relates to the spell… whether the spell was successful or not. For instance, if the spell was of a banishing nature, it may be wise to burn the ingredients (that are safe to burn). If it was wish related, perhaps send the ingredients off down the running water of a river (if safe to do so). If it was a curse, perhaps churn the ingredients (that are safe to do so) in a blender, and toss them straight in the trash. Spell jars may be cleansed and re-used, however, this is a personal preference and you shouldn’t feel obliged to re-use spell jars or ingredients if you don’t feel comfortable doing so.