Mention a composting toilet for boats, and most people imagine the enormous throne-like box of the typical home composting toilet—an object that wouldn’t fit on any but the most capacious of boats.
However, there are currently two brands of composting marine toilets on the market, Nature’s Head, and Air Head, that are compact, occupying a footprint of about 18 by 14 inches, and are only a few inches taller than the standard marine toilet.
How A Marine Composting Toilet Works
A composting toilet made for home use collects both solids and liquids in the same compartment underneath the toilet. The liquid and solid waste products are mixed with peat moss, and, over time, decompose.
Due to the large quantity of liquids relative to the solid waste, the tank on the typical home composting toilet is quite large. Marine composting toilets solve the size issue by separating the liquids from solids.
What Happens to the Liquids in a Marine Composting Toilet?
When the marine composting toilet is used, urine runs into a separate plastic container that sits forward of the composting chamber, while the solids drop into the chamber below the toilet. Two people using the marine composting toilet exclusively, will need to empty the liquids every three or four days.
The container is easy to remove, has a cap to seal it, and a carrying handle. It can be emptied into any shore based toilet, rinsed and reinstalled in minutes.
What Happens to the Solids in the Composting Toilet?
Solid wastes, including toilet paper, collect in the composting chamber beneath the bowl. Most seasonal users say they empty the tank about once a year, usually in the spring before the season starts. The contents of the composting chamber look and smell like garden soil.
Two people living aboard full time would need to empty the compartment more frequently, approximately every two or three months.
Advantages of a Marine Composting Toilet
Composting marine toilets cost about $1000, which is usually less than the cost of installing a holding tank and flush toilet. They are simpler to install, use and maintain. The unit is self-contained, and requires no water or chemicals.
There is no overboard discharge of waste, nor any need for trips to a pump out station. Properly vented, both manufacturers of the composting marine heads claim the toilets are also completely odor free. One owner at the Seattle Boat Show reported a faint urine smell which she cured with a couple drops of Purell Soap on the drain holes for the urine container.
Disadvantages of a Composting Marine Head
The footprint of the toilet is somewhat larger and taller than the standard marine toilet so may require some reconfiguring of the head space before installing the composting toilet. Also, the toilet seat and bowl are hinged to swing up for access to the composting compartment.
In a small boat, it may be difficult to locate the toilet far enough from the hull or a bulkhead to allow access to this compartment. Also, the sphagnum peat moss used in the composting chamber is non renewable, but several composting toilet owners report good results with COIR, a renewable product made from dehydrated coconut husks.
Marine composting toilets offer an alternative to both the complex marine head systems, and the more basic, and labor intensive port-a-potties.
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