Humanure and Composting Toilets

The topic of composting toilets and managing bodily fluids comes up again and again and it is one that I’ve touched on in numerous podcasts over the years.  But just recently I visited Missoula’s wastewater treatment plant with Heath Carey, a local environmental scientist who spearheaded the Missoula Hybrid Poplar Demonstration Project (while a graduate student at the UofM), which focused on the reuse of treated wastewater as a source of irrigation and fertilization for a 1.6 acre poplar plantation – and way to reduce the amount of “poop Kool-Aid” going into the Clark Fork river. We recorded a two part podcast, in which Heath and I talk about the plant, the energy and money needed for its maintenance, and the negative effects of wastewater on waterways due to their pharmaceutical, heavy metals, chemicals, and nutrients content.  We also discuss the alternative idea of poop beasts,  trees (such as poplar, cottonwood and willow) that use the nutrients for growth, binding chemicals and pharmaceuticals and building soil over time which in turn will be able to take in more water and nutrients.

The huge volume of water that is used in sewer treatment plants is another concern when thinking about waste management.  Reducing the amount of water going into the system in the first place is a good first step.  Even better would be to use a composting toilet with urine diversion and a greywater system which would eliminate the need for sewers altogether.

But, when composting people poop, or humanure, many factors come into play. Odor, concern over mixing pee and poop, venting, adequate heat … all considerations when switching the old outhouse into an effective composting system … and there are loads of alternative approaches.  The video below is a tour of four outhouses – the last one is a piece of art and is a fully water tight system.

All of the systems in the video minimize pee. There is no pee diverter, just the request that pee go elsewhere when convenient (easy for the guys, and with a little knowledge, relatively easy for the gals).

Urine-diverting systems can be purchased or made.  Carol Steinfeld, author of Liquid Gold, shared her experience, in a permies.com post, on how to make a urine-diverting composting toilet:

…after making these, you’ll see the value of the manufactured diverters. However, a funnel can be just fine. Make the diverter with an auto parts store large funnel or with a cut bottle. You can make a waterless urinal out of a bottle or funnel or purchase the oil-trap versions or the no-trap versions. I install low-cost waterless urinals with no trap when then drain to a graywater system or gravel trench. Urine is a great additive to a graywater system because it adds nitrogen to the carbony water that is graywater, creating a more complete diet for microbes and plants. Much of this is shown in my book, Liquid Gold, and somewhat in my books, The Composting Toilet System Book and Reusing the Resource.”

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