There are many reasons to consider switching to a marine composting toilet for your boat. Composting toilets provide an excellent alternative to holding large amounts of waste during sailing expeditions, or to discharging chemically treated waste into open waters. Even though the starting costs run around $1200 for most composting toilet models, they can still be quite a bit cheaper than outfitting a boat with a standard marine head and holding tank.
And besides these practical advantages, composting toilets have additional environmental advantages to consider as well. A compost toilet will help save on water usage, eliminate the need for chemicals to treat waste, and produce a valuable end product that can be used in place of chemical fertilizers around trees, flowers and other plants.
However, composting toilets also present certain challenges for boaters as well. They must be constructed so as to be able to handle a considerable amount of turbulence. There is a problem regarding the space requirements of many self-contained composting toilets, and the power requirements as well: most composting toilet models require that a vessel have enough power so that they can run a 12-volt, 4 watt fan continuously, and a heating unit occasionally (to control moisture and prevent odors).
Fortunately in recent years several manufacturers have stepped up to the challenge and started to produce composting toilets meant specifically for marine use. The Sun Mar Mobile is one such example. With this model, the Sun Mar corporation created a special mechanism to ensure the composting drum is always held in upright position during “violent motion.” They also developed a special gasket system around the finishing drawer to ensure there are no leaks from it as well during rough weather. Space modifications features were put in place to that more vessels can accommodate them (such as fold-up foot rests) and special filters were installed for the vent stack so there are no odors at deck level. The model is not cheap, however, and starts around $1600, but it is an excellent example of a composting toilet built specifically for marine uses.
The space requirements will still be a challenge for smaller craft, however. If you are considering purchasing a composting toilet you need to ensure that it will be able accommodate the number of people using it, otherwise you will end up with an overflowing toilet with unfinished compost inside. The Sun Mar Mobile is suitable for one person, possibly two, but would not be able to accommodate any more people except for occasional outings. You will also need to provide some space to store the dry carbon matter that is used instead of water for these models (sawdust and peat moss are probably the most commonly used materials). And you need to ensure that there is adequate space to be able to remove and empty the finishing drawer once the compost is ready.
If you are interested in learning more about the composting process, you should read the article “Toilet Composting Basics.” If you would like to learn more about what you can do with the finished compost from a composting toilet, read “What is Humanure and What Can I Do with It?“ Otherwise, return to the Toilet Composting Homepage, where you will find many additional articles and resources regarding composting toilets.