Sun Frost “Human Humus Machine” Composting Toilet

"This composting toilet is not only a great way to recycle waste products, but it is the cleanest composting toilet we’ve used.  Our facility is on a city park and is heavily used, yet it never smells and requires very little maintenance.  It is a great way to close the waste production to fertilization loop."
–Kevin Cunningham
 Arcata Educational Farm
 Arcata, CA


“Finally, a simple composting toilet that really works! It’s easy to deal with… and produces a compost you would never guess to be human waste. It even handles urine without becoming anaerobic.”
Eddie Tanner – Human Humus Machine user for 3 years

The Human Humus Machine produces high quality humus, which has the same appearance and aroma as high-quality topsoil. Heat-generating and pathogen-consuming microbes control pathogens in the finished compost.

The Human Humus Machine is available in a relatively low-cost kit form. The kit consists of all the parts necessary to convert two 55-gallon drums into a state-of-the-art composting toilet. The drums have a plastic liner to eliminate rusting. The kits are easy to assemble and can be completed in less than 2 hours. The installer would obtain the drums locally. We can also offer fully assembled units.

The Human Humus Machine is a batch-type CT. After the drum is full, the contents of the drum are allowed to sit for a number of months to complete the composting process. In non-batch type composters, newly deposited material can contaminate compost ready to be removed.


Composter top with pump, exhaust vent and mixer

Top of finishing composter

Drum fitted, with rustproof liner and grate

Contamination From Conventional Sewage Treatment

The National Resources Defense Council (NRDC) has reported that

“there were more than 20,000 days of closings and advisories in 2005, at ocean, bay and Great Lakes beaches.” The bulk of these closings are the result of improperly operating sewage treatment plants and septic systems.

The EPA estimates that each year, one billion gallons of raw sewage are dumped into U.S. waters. That is 3000 gallons for each person in the United States. Composting toilets could conserve water and change this hazard into a valuable resource.

Advantages of Composting Toilets
Advantages of the Sun Frost Human Humus Machine
  • Water and the energy are conserved. Saves over 3000 gal/year when compared to typical toilet and 1500 gal/year when compared to a low-flush toilet
  • Turns a waste product into a valuable soil amendment, a key for sustainable agriculture
  • Nutrients and pathogens don’t end up polluting waterways
  • The infrastructure is much cheaper than a conventional sewage system
  • Self-contained, no runoff
  • Low cost
  • Produces high-quality compost
  • Excellent odor control
  • Vent system requires only several watts to power – can be run on either AC or DC
  • Deposited material is immediately buried below soil-like compost
  • Will give many years of trouble-free service
  • Excellent control of pathogens

Control of Pathogens
A unique feature of the Human Humus Machine is that the compost can be pasteurized before it is removed from the composter. The temperature needed to attain pasteurization depends on how long that temperature is maintained; pasteurization can be accomplished at 130°F for 3 days or at 180°F for 10 minutes.

When the composter is filled and about 10 pounds of easily compostable material such as unbleached flour, cottonseed, or alfalfa meal are added, temperatures high enough for pasteurization can be obtained.

Even without pasteurization, we found that the level of E. coli in the compost was low enough to allow its use as a soil amendment. The EPA has developed standards for acceptable levels in sewage sludge. Sludge is the solid material settled out in a sewage processing plant. The un-pasteurized compost we tested had an E. coli levels five times lower than the standard set by the EPA for use as a soil amendment.

To be extra cautious, we recommend that the finished compost not be used on crops that are uncooked or are in direct contact with the soil.

compostingOptimal Composting Conditions
The Human Humus Machine is designed to provide optimum composting conditions: a warm environment with good aeration and moisture control. The Human Humus Machine is one of the few composting toilets in domestic use that is insulated and can attain temperatures significantly above ambient temperature. The center of the compost pile is typically about 50° above the ambient temperature. If the composting chamber is kept warm, the capacity of the composting toilet is significantly increased because the composting process is faster. Very large composting toilets typically do not heat up because of the large surface area of the uninsulated outside shell.

The grate in the bottom of the composting chamber allows liquid to drain to the bottom of the composter. This liquid is incorporated into the compost pile by adding dry material to the composter, such as dry grass or wood shavings, and them pumping the liquid to the top of the pile. The composters are typically filled after about 1400 uses.

Excellent Odor Control
The composting toilet incorporates either an AC or DC fan.. The DC fan can be connected to a battery or directly to a solar panel. The fan typically requires 4 watts to operate. The exhaust fan provides a constant flow of air so that odors generated while using the toilet or during the composting process are directly exhausted outside. The composter incorporates a 4-inch exhaust tube, which can be connected to 4” dryer vent fittings. It is amazing how odor free the composting material can be kept.

Mixing
The Human Humus machine incorporates a highly efficient and easy-to-use stainless steel mixer. Each time the composting toilet is used, instead of flushing, the mixer is rotated several times and the newly deposited contents are buried in the soil-like material in the composter. The mixer is conveniently stored inside the composting toilet.

A step stool is provided to so that the seat is at a convenient height. An alternative would be to build the composting toilet so that the floor of the restroom is about 18” above the bottom of the drums.

For additional info on recycling bio-solids to promote sustainable agriculture, please read the letter to the editor of Acres USA written Larry Schlussler PhD. Dowload here as a PDF file.