Neither is practical on a sailboat
Composting is a terrific concept, but IMHO, it's not quite there for onboard use yet. First there's the matter of size. Although there have been some attempts at maller self-contained units, the only one that works as advertised is the Sun-Mar unit...and their smallest self-contained "marine" composter---the "Ecolet" model--needs a space 29" high x 20" deep x 25" wide (includes enough room for the handle on the side thatrotates the drum and enough space to pull out the drawer), which is too big to fit in 99% of heads. The specs are the Sun-Mar website at: http://www.sun-mar.com Because there has to be enough room in the drum to "fluff" the contents so it gets enough aeration--otherwise it just rots (and stinks), it's just about impossible to make one any smaller than the Sun-Mar unit...the Sun-Mar people have tried, because they'd love to have a major piece of the marine market. Composting is a wonderful solution in on-land situations where there's no sewer and septic is impossible, but in addition to the size problem, there are also other issues onboard that don't exist in land situation: 1. what to do with excess liquids. 90% of human waste IS liquid...mostly urine, but even solids are mostly liquid. Excess liquids have to be drained off, or you have wet soggy organic material...and wet soggy material doesn't compost. Adding dry material--peat moss is the recommended material 'cuz it breaks down quickly--to each flush helps some, but not enough, and there's usually more liquids than the evaporator--which, btw, requires power--in the self-contained units can handle either. You can't legally drain 'em overboard (unless you're at sea), so they have to go into a holding tank...and there goes any advantage to installing a composter even if you have room in the head for it. 2. Enough peat moss to keep the thing working during an extended cruise can take up more storage space than a holding tank. 3. It needs a 3" vent stack...where are you gonna run THAT to??? 4. It needs power to run the evaporator. As for incinerating toilets, forget it. They only run on 115/ac, and contrary to popular belief, everything doesn't turn to ash in a "whoosh" of heat with each flush. The burn time is 90 minutes at something like 1100 degrees F...which means you don't run it after each flush, but when it gets full--so it's kinda like a portapotty with a burner...and even 90 minutes isn't enough time to completely reduce everything to ash. Plus, incinerators also need a 3" vent/smoke stack, and no matter what the mfrs claim, the smoke STINKS! On a boat the size of yours, your best bet is a Lectra/San and a small holding tank for use only when you have no other choice. Because the Lectra/San discharges by overflowing--there's no pump in it--you don't have to run it when you're at sea where there's no need to treat the waste. Maybe once a day to macerate any solids in it. So power consumption is only an issue while you're in coastal waters where you'll prob'ly have to spend a lot of time motoring anyway.
