I've read that when rendering fat, you can add baking soda to the water/fat mix to get rid of the smell if it's gone rancid.  Having had a jar of baking grease that had done just that, I decided to try it.

Unfortunately, nothing has been said about not adding the baking soda while everything is boiling.

Oh well.  Guess it was time to clean the cooktop anyway.  *facepalm*