Composting is a terrific concept, but IMHO, it's not quite there for onboard use yet. "Nature's Head" seems to be very similar to the AirHead..
http://www.airheadtoilet.com Neither of which is a true composter but a dessicator. The main drawbacks to onboard composters and dessicators are:
1. What to do with excess liquids. 90% of human waste IS liquid...mostly urine, but even solids are at least 75% liquid. Excess liquids have to be drained off , or you have wet soggy organic material...and wet soggy material doesn't compost, it rots. Adding dry material--peat moss is the recommended material 'cuz it breaks down quickly--regularly helps some, and there's usually more liquids than the evaporator--which, btw, requires power--in the self-contained units can handle either. Both the AirHead and Nature's Head separate urine from solid waste the urine is directed into in jugs (or a tank). You can't legally drain 'em overboard (unless you're at sea beyond the 3 mile limit), so the jugs must be stored and carried off the boat or the tank must be pumped out same as any other tank. So I can't see much advantage to this over a portapotty.
2. Even though urine is collected separately, solid waste is 75% liquid, so peat moss is needed to keep it dry. Enough peat moss to keep the thing working during an extended cruise can take up more storage space than a holding tank.
3. Composters need a 3" vent stack... AirHead originally specified a 3 vent but is now claiming that a 1.5 vent is adequate.
4. Continuous power 24/7 to run the evaporator.
5. Composting only works in temperatures above 70 F....and only works really well above 75. Below 70, bacterial activity becomes increasingly sluggish--TOO sluggish to make anything happen. So you have to keep it warm all winter--that's 24/7--or waste will just sit there. The good news is, nothing stinks much in cold weather either.
That's my $.02 worth...But you may decide that this thing is greatest idea since the pop up toaster.
