Every day, the average person flushes 10 gallons of clean drinking water down the toilet. This constitutes a waste of two precious resources: scarce water supplies and human manure, which could instead be composted to form a fertile soil amendment.
While composting toilets (CTs) of various styles are commercially available and legal for home use, they are often too expensive for many would-be users. There are excellent designs out there for affordable, easy-to-construct CT systems, but local laws typically prohibit their use.
Several years ago, the Tucson, Arizona-based nonprofit Watershed Management Group (WMG) set out to change this paradigm. Working with the Arizona Department of Environmental Quality, WMG launched a “Soil Stewards” pilot program to install and monitor 24 site-built CT systems in homes and organizations throughout southern Arizona. The end goal with this program is to develop a safe and effective, do-it-yourself CT design that is legally permitted for Arizona residents.
The group used two main designs in this project: the Omick barrel composting toilet and Nogales double chamber composting toilet.
Omick Barrel Composting Toilet
Designed, tested, and refined over the years by David Omick, a local southern Arizona expert, the Omick barrel is practical and cost effective. It is a batch-type toilet design featuring a series of 55-gallon high-density polyethylene barrels as the composting and collection container. A customized plywood panel that serves as a removable seat, vent, and light trap platform.
Visit www.omick.net/composting_toilets/barrel_toilet.htm for detailed information.
Nogales Double Chamber Composting Toilet
Developed and tested in the colonias of Nogales, Sonora, the tried and true concrete block double chamber is being adapted and piloted here in Arizona. The basic form using concrete masonry blocks can be built as a stand-alone structure or integrated into the home. Basic details in draft form are available here: Plan view | Section view
Urine applied appropriately is a perfect compliment to humanure to provide additional nutrients to plants. To compliment the proposed “site-built” composting toilet designs David Omick applied his ingenuity to develop a low-cost, practical approach to urine diversion and facilitate easy application in the home landscape setting. WMG’s Soil Stewards were given the option to install this urine diversion system to accompany their composting toilet through the pilot process.
After a year and a half of use, samples taken from these systems were tested by the University of Arizona and given the classification of Grade A compost, safe for agricultural and landscape use. With this data in hand, WMG is now working to get these designs approved for legal use in Arizona.
“Poo to Peaches”—Educating the Next Generation of CT Users
While the effort to get site-built CTs legally approved continues, another major hurdle to widespread composting toilet acceptance remains: public opinion. The idea of pooping in a barrel or bucket still lacks a certain appeal for many people who have grown accustomed to their flush toilet lifestyles.
In order to change this perception, WMG is focusing on teaching young kids about the benefits of composting toilets through a children’s book, Poo to Peaches. With colorful illustrations and a fun, rhyming style, the book explains the nutrient cycle and the basics of proper CT use for preschool and kindergarten aged children. In addition to the kids’ story, the book will include technical information for adults on the design and maintenance of barrel CT systems.
The group has recently launched a Kickstarter campaign to finish and publish the book, as well as to offer local educational programs at schools and libraries. Rewards include hard copies of the competed book, a special Q&A webinar with CT experts, and tours of the Soil Stewards CT sites in Arizona. For those that back the project at the $1,000 level, WMG will build a 2-barrel composting toilet system available to pick up at the group’s Tucson headquarters.