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Soil Stewards - Pioneering affordable and legal composting toilets

Watershed Management Group's Soil Stewards program is piloting a Composting Toilet project which aims to:

  • field test "site-built" composting toilets for performance and likeability
  • address onerous permitting requirements
  • tackle social and community barriers to what should be an abundant local resource

Through a special trial process in coordination with Arizona's Department of Environmental Quality, a mix of residential and organizational sites in southern Arizona, mainly in and around Tucson, will build, install, use, monitor, and evaluate four proposed composting toilet designs for a year and a half.

The four composting toilet designs are of two main types and with/without urine diversion:

  1. Omick barrel composting toilet
  2. 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 

An ADA design was also developed and will be field tested at the Community Food Bank's Las Milpitas garden to accomodate handicap access: Plan view | Section view

Urine Diversion

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 have the option to install this urine diversion system to accompany their composting toilet through the pilot process.