Composting toilet.jpg
FA info icon.svg Angle down icon.svg Project data
Authors Ryan LLamas
Location Arcata, California
Status Deployed
Instance of Composting toilet
OKH Manifest Download

Organic farms speak to the conventions of the modern world, and the way we eat our food. How the farmers on these CSAs go to the bathroom also speaks to these conventions. The composting toilet at Wild & Wise, which is a result of this project, serves to say, "our waste is valuable, and should not be wasted." This project outlines the basic components of composting human waste, as well as ways to make your own composting toilet.

Background[edit | edit source]


Wild and Wise is a developing herb CSA farm located in Arcata, California. The herbalists, educators, students, and farmers at Wild and Wise are dedicated to spreading holistic and alternative wellness practices in the community. Their current site is without toilet, a problem for those long volunteer days! This mobile composting toilet project is an experiment in Appropriate Technology.

Problem statement[edit | edit source]

The objective of this project is to provide the members and volunteers of Wild and Wise with a mobile composting toilet, as their current site is subject to change.

Criteria[edit | edit source]

These criteria were developed by myself, discussed and confirmed with Ami from Wild and Wise, and are meant to establish constraints on the design, that it may be more efficient.

Criteria Constraints Weight
Portability be able to be disassembled in < 10 minutes & carried by two people. 10
Aesthetic Must not stand out, must be subdued and out of sight, yet pleasant when used. 5
Educational Users of the toilet should use toilet properly after reading educational sign. 4.5
Safety No user shall be at risk of falling into the toilet. 5
Sanitation Must not present a health risk when used properly 10
Budget The budget shall not be exceeded 5
Functionality Toilet must be in working condition 10
Durability Toilet should last min. 2 years 6

Literature Review[edit | edit source]

The toilet as a fixture tells us about our aversion to our "toilet matter". Consider how it is whisked away in a fell swoop, and not considered again. We do not want to think about it because it makes us uneasy. The only word for our toilet material that does not make us squirm is perhaps "waste". "Waste" implies it is not only disgusting, but also worthless. Yet, the only waste involved in the way we go to the bathroom, is that we do not return our BMs to the earth. The composting toilet system, the Earth Closet, is is a sanitation system requiring neither waste nor disposal.[1] Provided a little bit more consideration and thoughtfulness in using the bathroom, dry toilets serve as a means of keeping our water clean and our soil healthy.

How to[edit | edit source]

Composting with organic human material is a more delicate process than without, since fecal matter contains unsafe human pathogens and must be removed properly. Microbes, worms and other organisms aid in the decomposition and purification of the pile.[2]

General Parameters[edit | edit source]

There exists a balance in compost piles that must be maintained closely.

  • Air: Decomposition takes place in the presence of aerobic bacteria, therefore the compost pile must be kept aerated that it may breath, so to speak.
  • Moisture: The compost pile must be neither too moist, nor too dry. Urine can be disposed of in a different receptacle, but will in this case be mixed. That being said, the moisture level should be that of a used sponge.
  • Carbon/Nitrogen: According to Sim van der Ryn, author of the Toilet Papers, there should be a 30:1 Carbon to Nitrogen ratio for prime aerobic decomposition.
  • Temperature: The compost must be hot in order to decompose. A temperature (that should approach 100°F will be created by the pile itself, provided appropriate aeration and moisture..[3]

To "flush", one simply covers the BM with a bulking agent such as sawdust, loose dirt, or toilet paper, eliminating the odor and ensuring aeration. The compost must also be turned often for the sake of aeration. This is done once the bucket into which the feces are deposited is emptied into the main pile.[4] Secondary materials like grass, hay, and even garden scraps should be added as well.[1]

Mobile Composting[edit | edit source]

The Earth Closet, being located on a farm whose location is subject to change, must be a mobile device. The composting toilet is a simple fixture: a single five-gallon bucked is used beneath the moveable seating unit. The bucket must be emptied once it is full and properly cleaned. When the toilet-compost is ready to be mixed with the compost pile, it is important to keep in mind that the toilet material should be fed into the large pile and well mixed, not just thrown on top. This will reduce the odor and again, provide aeration.[1]

Construction[edit | edit source]

The construction of the mobile composting toilet is incredibly easy. The entire system is made of the following materials. Be sure to sand the wood first! The dimensions and cuts of wood will differ from project to project, depending on context. Feel free to be creative.


Sand wood well, for it must later be sealed. Use an electric sander or sandpaper (this will take a long time).

it's fun.


These are the three walls. The roof must be angled, so make two of the posts that make up the side walls shorter, to allow for the roof to be placed there. Moreover, only use two wooden boards that connect the posts that make up the walls. This is a mobile composting toilet and must be as lightweight as possible. For a roof, I found a big piece of plywood; it just gets stuck on top.



Find a seat; I found an old desk and cut a hole in it.


Seal the wood with sealer; this protects the wood from rain.





It's similar to 'regular toilets


Proposed time line[edit | edit source]

This timeline proposes dates for the completion of the project in an orderly fashion. Dates are loose and subject to change.

Project Started Completion
Gather Supplies 22 February 24 February
Construction of Bench 26 February 2 March
Construction of Portable Walls 5 March 9 March
Build Educational Posts 10 March 12 March
Set up toilet at W&W 14 March 14 March
Follow up 5 April 12 April
Video 12 April 26 April

Costs[edit | edit source]

This table presents the hypothetical cost of constructing a compost toilet. In the case of the toilet being built in this project, I was fortunate to have had most of the material already donated. The costs presented reflect their value on hardware store websites. Material from other sources was acquired at the indicated locations.

Quantity Material Source Cost ($) Total ($)
1 Converted wooden desk unit serving as bench Angels of Hope Thrift store 30.00 30.00
1 Toilet Seat Ace Hardware 21.99 21.99
1 Bamboo fencing 20' Home Depot 23.97 23.97
8 Plywood 3/8" x 2' x 4' Ace Hardware 9.74 77.92
10 Wood boards 1" x 12" x 4" Ace Hardware 6.52 65.20
1 5 gallon bucket Ace Hardware 6.49 6.49
Total Cost $225.57

Informative[edit | edit source]

Here is a fun, informative video about the construction of the toilet.

Informative Sign

Conclusion[edit | edit source]

Testing results[edit | edit source]

Testing results were successful in that the toilet is standing. The farm has recently been placed at a new location (May, 2013) and has not yet begun planting, volunteer days, and the like.

Lessons learned[edit | edit source]

Mobile composting toilets are ideal when moving between venues, and the integration into the compost pile is simple. However, the mobile composting toilet does not allow for a lot of fun design features on a tight budget.

Next steps[edit | edit source]

As Wild & Wise has more volunteer days and begins growing as a CSA, the compost toilet will be given a true test, as farmers do their thing up in there.

Thank You![edit | edit source]

Thank you to Ami Brusca from Wild & Wise, and Lonny Grafman Instructor of Engineering 305!

Lonny Grafman
Ami Brusca

Team[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 1.2 Jenkins, Joseph C.. The humanure handbook: a guide to composting human manure. 3rd ed. Grove City, PA: Joseph Jenkins, Inc. ;, 2005.
  2. Holmgren, David. "Use and Value Renewable Resources and Services." In Permaculture: principles & pathways beyond sustainability. Hepburn, Vic.: Holmgren Design Services, 2002. 93-109.
  3. van der Ryn, Sim. The toilet papers: designs to recycle human waste and water: dry toilets, greywater systems & urban sewage. Santa Barbara: Capra Press, 1978.
  4. Hazeltine, Barrett, and Christopher Bull. "Composting Toilets." In Field guide to appropriate technology. Boston: Academic, 2003. 792-796.
FA info icon.svg Angle down icon.svg Page data
Part of Engr305 Appropriate Technology
Keywords composting, waste management
SDG SDG12 Responsible consumption and production
Authors Ryan LLamas
License CC-BY-SA-3.0
Organizations Cal Poly Humboldt
Language English (en)
Related 0 subpages, 5 pages link here
Impact 378 page views
Created February 2, 2013 by Ryan LLamas
Modified May 23, 2024 by Kathy Nativi
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