People who have the compositing toilets have all mentioned they do not smell
http://minimotives.com/2014/02/13/how-my-composting-toilet-actually-works/
The pros: I like it way better than a flush toilet, honestly. There are NO smells at all (there is a fan that creates a constant vacuum of air going to the outside). It is warm when you use it (the unit I have has a small heater), no back splashing and no one can hear you peeing! All pros. I have the added benefit of knowing that I am not contributing to a waste system where drinkable water is treated, used to flush a toilet and then has to be treated again, there is quite the process to that and a lot of energy/chemicals which I get to bypass, naturally and safely. Like I said, I was very leery initially for the same reasons as many others but after six months I have had two issues and zero REAL issues, I will get to those in a moment. All of that being said, I have not yet had to empty the drawer (based on full time occupancy – 3-4 persons – that would happen after about one year, and about 4 times a year). Currently I am not even a quarter of the way to full but in spring I will do that drawer emptying deed, simply because it’s been enough time. I expect that it will be as painless as they say (pretty hands off and non-gross). Other than that, even as expensive as it is it is cheaper than installing a septic system and it is not as limiting to finding a location as having to hook up to sewer, it gives me more flexibility. So, those are my pros so far, now the cons…
The cons… 100% of people (I rounded up, there are those .001% that think differently) do assume it’s gross and disgusting and that I am a weirdo for choosing that option, that is the one drawback. I do have a brother who refuses to use it, my partner did too, for a little while, but he’s fine with it now.