This post has me confused.
I've never thought the Geo Method was to eliminate odors, only a method to insure the tank (and sensors) gets cleaned out during dumps. The soap and water softener doesn't have any odor masking properties.....does it?
Odors coming out of the vent is normal....that's one of the reasons it's there.
I don't think there is any way to keep your black tank from having odors when it is being used...even Happy Camper. Altho I do assume HC has some odor masking ingredients, but to eliminate the odors inside the tank...naw, I don't think so.
Ice is NOT part of the Geo Method....in fact, ice has no effect at all on the black tank except making it colder, and I'm not sure that's a good thing.
Ron