The Wynn’s YouTube channel has several videos about their RV composting toilet experience. Composting Toilet Secret Tips and Tricks is a good place to start if considering this option. Nature’s Head Dry Composting Toilet / Standard Crank Handle (Amazon affiliate link) is a popular example of the appliance. There are a few things to consider about composting toilets in an RV:
- The RV composting toilet costs 3 times (or more) that of a typical RV toilet.
- Proper composting requires aeration, 50F or better temperatures, 50% (+/- 10%) moisture content, and weeks to months of time.
- Disposal of waste remains an issue. The Wynn’s experience is that they need to dump the urine bottle every 2 or 3 days and the compost bucket every 2 to 3 weeks.
- The RV toilet needs a continuous electrical supply to keep its ventilation running. That is key to smell management, aeration, and moisture removal.
- Water use may be a bit less. The typical RV toilet needs enough water to keep solid waste in the tank covered. A composting toilet only needs enough to clean the bowl.
- A composting toilet needs to be ‘primed’ with peat moss or something like Worm Factory COIR250G10 Coconut Coir Growing Medium 250g – 10 pack (Amazon) to help aerate the feces and optimize decomposition.
- Flushing the RV composting toilet involves cranking the aeration and maceration paddles.
Some cabin and house type composting toilets can get really sophisticated. The big issues that complicate the operation are that of removing moisture, allowing for a proper composting time, managing temperature, and facilitating final disposal.The RV toilet manages moisture by operator attention to separating feces and urine into separate containers, depending upon mild ambient temperatures, forced continuous ventilation, and removal of waste prior to complete decomposition.
The comments I see indicate some of the same issues and attitudes regarding waste disposal as occur with gray water. With regulations and laws getting ever more strict, disposal of any biologic waste outside of specially designated places should be assumed to be prohibited. You might get away with dumping the urine bottle in a privy or toilet but the compost is another issue.
RV toilet compost should be handled and treated much the same way as cat litter. It should be considered dried out rather than composted. Some toilets allow rotating compost buckets to help further composting but the RV situation with a total bucket time of only a week or two with additions within a day or two of disposal isn’t going to do much other than start the initial phases of composting. The week or two does provide a good composting start and does remove a lot of moisture and that tends to reduce the volume and weight of the waste. The result isn’t the sort of thing to put in a privy or other toilet. It also isn’t the sort of thing to spread out in the open. That leaves bag and trash or shallow burying (if allowed).
There are a number of DIY composing projects out there. The RV provides a few opportunities for such a system. For example, the air feed for the toilet could come from the top of the refrigerator heat exchanger. That would help refrigerator efficiency as well as provide pre-warmed air for the compost pile. Both the compost pile air exhaust and the urine bottle could be routed into the RV black tank to reduce the necessary waste disposal intervals.
The standard RV toilet works well for most RV needs and provides a fairly high barrier for competing technologies. What seems to give composting toilets an edge for some are ideological fantasies. These center on ‘green’ ideas like saving water or recycling or personalized waste handling. Perhaps the old style gopher hole should be considered for comparison. As with all waste, the issue is really more a problem of concentration than it is with where it goes.