i would plan on using the compost...but if you fill up before you can make it home there are other options.
plus i'd say it would still hold several advantages over black tanks or cassette toilets. separating the liquids and solids so you have a solids tank that can last for weeks. the moss or coco coir you put in there begins the composting process so that doesn't reek when you empty it. also you have something that you can empty somewhere besides an rv dump.