Waste is always a tricky topic for boaters, because it’s something you’ve got to deal with. Keeping surrounding waters clean and free of contaminants is important. The primary environmental concern with sewage is not the urine, which is sterile, but feces which contain bacteria, pathogens, and nutrients, and should not go overboard. The septic tank may only be emptied, from at least, 3 miles from shore. Pump-out stations will help you get rid of waste, but are only available near a handful of cities.
A dry toilet is a good option for those who do not want to haul anchor and head offshore to flush their tank. Having a dry toilet aboard frees up much-needed space. It also means no holding tank to empty, no smelly hoses to unclog, and little to no maintenance. You can build your own dry toilet or buy one of the many models on the market. On the market most dry toilets are referred to as 'composting heads' despite the fact that they are not designed for true, full composting onboard. Humanure needs 12-24 months to become pathogen free, and no sailboat has the carrying capacity for this (esp considering that a tank is emptied once a month, or once every 2-3 months depending on usage).
Ideally, the contents of the composting head would have to be transferred to a separate container, and left alone to decompose. If the goal is to do full-composting, partnering with someone on land is ideal, but otherwise, bringing the solids to the trash in composting bags is the next best thing. Although, it is a shame to let this potentially rich material go to waste...
The ideal medium for processing your waste into compost depends on how you plan on using your toilet and vary between sawdust, peat moss or wood chips. Use what is available in your area.
Most dry toilets have a urine diverter, separating the liquids from the solids to ensure contamination-free composting. Some models also have fans, to help the solids dry out and remove odors. In composting heads, urine accounts for ~85% of the waste volume in tanks. Having a diverter is great because it increases capacity for solids, which means not having to empty the tank as often. If near a city, When full, it’s possible to empty jugs of urine into public toilets. If there are no facilities nearby, capping it off to dispose of later, and replacing the jug is a good option.
See our dry toilet.