Introduction
Our reasons for choosing to switch to a composting toilet were a mix of practical and pragmatic. From a practical point of view, having a composting toilet means not having a holding tank, with its limited storage, propensity to emit a very distinctive odour, and constant potential for overflow. On top of all that, you have to regularly pay $20 or more to have the holding tank pumped out, and always keep your fingers crossed when traveling that you'll be able to find someplace to get a pump out before your tank gets full. There is also the space that a holding tank takes up. On a boat, storage space is always at a premium, so the space taken up by a holding tank could be better used for other things.
To understand the pragmatic reasons, head on over to Joe Jenkin's Humanure site (http://humanurehandbook.com/), and take a bit of time to read The Humanure Handbook. It is a very eye opening and enlightening look at the costs and waste of our 'modern' waste treatment systems.
More information on the why and how of our composting toilet can be found on our blog;
- Composting Toilet Background Info: http://www.7kts.blogspot.com/2013/09/frankford-and-boat-projects-2013-09-09.html
- Composting Toilet Build Project: http://www.7kts.blogspot.com/2013/09/composting-toilet-build-project.html
- Composting Toilet - Six Month Update: http://www.7kts.blogspot.com/2014/03/project-update-composting-toilet.html
Usage
Usage is quite similar to the use of a standard toilet, except that the solid and liquid waste is captured in different containers. Due to this, men will need to accept having to sit to urinate. After your first holding tank overflow, this would seem a small price to pay.
Depending on the amount of time spent on board (weekends vs weeks at a time) the time between emptying the storage containers will vary. The urine container being used by two people will typically need to be emptied daily. The solid waste container will take longer to fill up and require emptying. With two of us on board full time we were getting one to two weeks between emptying the solid waste container.
To prepare the solid waste container for use you start by putting an appropriately sized garbage bag into the bucket. We typically secured it with a bungee cord. Add a couple cups of cover material to the bottom of the bucket. The cover material can be saw dust, wood chips, coconut coir, or, in our case, peat moss.
After each deposit add a small amount of cover material, just enough to cover the deposit.
Once the bucket starts to get full remove the bag, compress and tie it off and dispose of it as noted below.
Odour
There is very little odour from the composting toilet. The exception of course is during the act of deposit, but an open window and a bit of air freshener can mitigate this quickly. Because the solid waste is encapsulated in cover material, it quickly dries out and stops giving off any odour. Depending on the cover material used, typically the only odour from the composting toilet will be a bit of an earthy smell.
Sometimes the urine container can develop a bit of a smell. To stop this use a mixture of 50% water and 50% vinegar in a spray bottle, and give the urine section of the urine diverter a spray after each usage.
Disposal of Waste
Because this is a urine diverting composting toilet, disposal of the waste can be accomplished differently for the solid and liquid waste.
Disposal - Solid Waste
There are three main methods to deal with emptying the solid waste receptacle, and disposing of the solid waste. First off, it is legal to dispose of human waste in the standard garbage system. Normally this is limited to infant diapers and adult sanitary undergarments, but it can logically be extended to the solid waste from the composting toilet. It is already bagged just from the bag that is placed in the solid waste receptacle, but I always double bagged it just to be sure.
For some people, throwing the solid waste out in the trash might be objectionable, so an alternative would be to simple flush down a toilet it in any shore based bathroom. Obviously you'd have moderate how fast you dump it, to be careful not to clog the toilet. Vault type toilets wouldn't have this problem.
Finally, if you have an ornamental garden at home you could take the solid waste home, complete the composting process in a compost bin specifically for this waste, and then use as compost to fertilize your ornamental garden.
Disposal - Liquid Waste
Disposing of the liquid waste is relatively simple. Just cap the bottle and bring it in to a shore based bathroom and simply dump it down the toilet.
Regulations
Canadian Marine Regulations are still a bit fuzzy where composting toilets are concerned, and lag behind United States Coast Guard (USCG) regulations. Basically, urine diversion composting toilets qualify as a Type III MSD (Marine Sanitation Device) according to USCG regulations [1] , and are approved for use in all US waters, coastal or fresh water.
In Canadian regulations, You have to interpret the stated rules for holding tanks in Section 88 [2] and note how a composting toilet satisfies most of the points, with the exception of pump out capabilities, of course. Also of note is the system has to prevent discharge of waste into the waterways, and be permanently mounted in the vessel. Composting toilets satisfy both of these requirements. As well, composting toilets are implicitly allowed based on the vessel being non-commercial, less than 15 gross tonnage, and not certified to carry more than 15 persons.
[1] https://www.dco.uscg.mil/Our-Organization/Assistant-Commandant-for-Prevention-Policy-CG-5P/Commercial-Regulations-standards-CG-5PS/Design-Engineering-Standards/Systems-Engineering-Division/Mechanical-Engineering/msd/#vessel"
[2] https://laws-lois.justice.gc.ca/eng/regulations/SOR-2012-69/page-14.html
