Hi,
last year I contacted Peggie Hall on her thoughts regarding the composting toilet systems for boats. Her reply (from Sept 2011) is below. Hope this helps.
You may also be interested in this article
http://www.mysailing.com.au/news/composting-toilet-passes-the-test
which gives another view on the composting toilet
cheers
Ron
Mundora 1726
Hi Ron,,,
Composting is a terrific concept, but IMHO, it's not quite there for onboard use yet, and definitely will cause more problems than it solves if only used occasionally.. "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.
IMO, an "MSD" portapotty ("MSD " designation means designed to be permanently installed and is fitted for pumpout and/or dumping at sea) makes a LOT more sense, espcially for occasional/weekend use,
--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/books/detail-books.htm?fno=0&sku=90&cat=1304
last year I contacted Peggie Hall on her thoughts regarding the composting toilet systems for boats. Her reply (from Sept 2011) is below. Hope this helps.
You may also be interested in this article
http://www.mysailing.com.au/news/composting-toilet-passes-the-test
which gives another view on the composting toilet
cheers
Ron
Mundora 1726
Hi Ron,,,
Composting is a terrific concept, but IMHO, it's not quite there for onboard use yet, and definitely will cause more problems than it solves if only used occasionally.. "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.
IMO, an "MSD" portapotty ("MSD " designation means designed to be permanently installed and is fitted for pumpout and/or dumping at sea) makes a LOT more sense, espcially for occasional/weekend use,
--
Peggie
----------
Peggie Hall
Specializing in marine sanitation since 1987
Author "Get Rid of Boat Odors - A Guide To Marine Sanitation Systems and Other Sources of Aggravation and Odor"
http://shop.sailboatowners.com/books/detail-books.htm?fno=0&sku=90&cat=1304