Are the buckets made from metal? In that case you can burn out the remaining oil. But that’s something you should only do if you know what you‘re doing obviously. German garbage disposal sites have special oil containers where you can get rid of larger amounts. Is there something similar where you are?
Well, this one caught me off guard. Welcome to Neon Genesis Lemmygelion I guess.
I would go as far as saying I wish the upvote button were gone too.