Marine composting toilets (boat composting toilets, or marine composting heads) can be a great addition to any vessel, and can help solve many problems that boaters encounter when it comes to holding and emptying toilet waste. However, many composting toilets may be considered too large to use on small vessels, although composting toilet manufacturers are increasingly working on creating models better suited for both the space requirements and the motion requirements needed for marine toilets.
Because the composting toilets manufactured for marine use are self-contained models, you will need enough space to accommodate both the toilet itself as well as room to pull out the composting drawer. There will be no additional plumbing required for most models. However, in order to lessen potential for odor and to help maintain the composting system in order, most system use a fan and your boat will need to have adequate power to be able to continuously run the fan (usually 4 watts, 12 volts).
In terms of cost, marine composting toilets can compare quite favorably against the cost of other marine toilet systems, particularly those that require a holding tank for waste. Most marine composting models run around $1200 or more. Although it may be tempting to go with a slightly cheaper self-contained composting toilet not built specifically for marine uses, you may regret this decision due to the specific challenges boats present in terms of properly containing the waste during bad weather.
For example, the Sun Mar Mobile composting toilet, probably one of the most sophisticated marine composting toilets currently on the market, currently costs around $1600. It can be used by one to two people full time use, and possibly accommodate even more for weekend outings. Sun Mar has put a lot of effort into designing a toilet that will deal well with “violent motion.” For their mobile unit, they made sure that the finishing drawer was gasketed in a manner so that absolutely no liquid could escape, and they also built a special drum locker that could ensure that the composting drum is continually held in an upright position. Additional special modifications for marine units include such features as fold-up foot rests and activated carbon and zeolite filters to ensure that there is no odors on the deck where the vent stack protrudes.
From an environmental standpoint, marine composting toilets are beneficial for multiple reasons, but not the least because they do not require any chemical additives, require no water to maintain, and create an end product (humus) that is a valuable soil additive that actually benefits the environment (instead of a waste product that needs to be treated and disposed of properly). The compost that is produced by marine composting toilets is absolutely sanitary and can used to fertilize a wide variety of plants and trees (for more, read “What are the Environmental Benefits of Composting Toilets?” and “What is Humanure and What Can I do with It?“)
Self-contained composting toilets are generally Coast Guard Certified Type III MSD. For more information about composting toilets, you can also read “Toilet Composting Basics” or return to the Toilet Composting Information Home Page, where you will find dozens of informative articles about composting toilets.