Composting toilet a great way to go for many. I hate dumping black water tanks, and porta potty's get old really quick. Plus, you don't need a 15 gal **** tank and weight. I just ordered a composting toilet for my trailer. I'll be in Flagstaff at Overland Expo in May for you to see it, if that is not to late. Here is the one I'm going to use, or it real similar.
http://natureshead.net
http://natureshead.net