Some help:
The composting head (Which I do not have) works at making the Black solids into Dirt!, if not, it is not working. The best way of disposing of the finished compost is to find a flower garden to dump it into, the flowers will grow and grow (There should be NO smell whatsoever and you can touch it with your hands (it is dirt)!) Please do not put it on food plants, as there is a very remote possibility pathogens could make it through the plant into the fruit (Unlikely, but why do something that could harm some one) also please wash your hands after touching any dirt composted or otherwise.
As for the liquid; the same plants would love the watering. Best way to see this for your self is to rent (Watch) the dvd "The worlds fastest indian" and check out the lemon tree, it is also a pretty good move. If your flower garden is only as big as a wine barrel, adding something to assist the urea conversion into a salt would be helpful.
For the record, I have a 20Gal mixed solids holding tank in the head compartment with a y-valve and in CA the pumpouts are still free+/- the y is locked when I am not more than 10 miles off.
Composting is a good direction, and in 10 or 20 years when my head gives out I will likely go there, but for now the old fashion holding tank works for me. Also in a marina I never use the head on the boat, I always! use the ones on shore.
Norm