Follow Up of WMG Pilot Composting Toilets












Written by: Darya Anderson

Bureau of Applied Research in Anthropology

School of Anthropology

University of Arizona

May 2016

In October of 2011, the Bureau of Applied Research in Anthropology (BARA) and Watershed Management Group (WMG) initiated the composting toilet pilot program. The details of this pilot are described in Pedro Robles’ report. 1 A goal of the original project was to determine whether it would be possible to develop two reference designs for site-built non-proprietary toilets and to find out whether toilets built according to those designs would perform in a consistent enough manner to be permitted in Arizona. The two reference designs are the double chamber toilet and barrel toilet.

The Arizona Department of Environmental Quality (ADEQ) outlines regulations for composting toilets in General Permit 4.03 in Title 18 document on environmental quality. At the time of the pilot (and also presently) third party certified composting toilets were/are legal but there aren’t clear legal guidelines for site built non proprietary toilets. It is up to the local Pima Department of Environmental quality (PDEQ) to enforce these regulations. For the pilot project the state issued one experimental permit, in the summer of 2012, that would cover construction of up to 24 toilets.

At this time installation of the toilets (either double chamber or barrel toilet) began for 21 individual recipients and two institutional recipients. From May 2012 to June 2013 BARA interns monitored the toilets via researcher and user-led methods. In the spring of 2016 BARA and WMG initiated a follow up study of the toilets to understand the long-term use patterns of the toilets. 18 of 21 individual recipients were visited and completed a questionnaire. The institutional toilets were not visited during this follow up.

This report will summarize the results from the follow up interviews. The following are the three objectives that the interviews were designed to address:

  1. Describe and explain recipients’ experience related to composting toilets

  2. Describe and explain how the pilot composting toilets currently function

  3. Explore the support recipients need/want

Describe and explain recipients’ experience related to composting toilets

Currently 60% of participants are using their toilets (Figure 1). Reasons individuals are not using their toilets include personal reasons such as: physical limitations, children, moving, neighbors, unable to get cover material. Reasons for disuse were not related to a dysfunctional toilet. Though not all toilets were being used, 100% of recipients reported being generally satisfied with their toilets (Figure 1). The most commonly mentioned reasons for satisfaction with toilet were environmental (water conservation, close nutrient cycle, minimize waste, soil amendment) and function (i.e. the toilet is doing what it is supposed to do) (Figure 2). Commonly mentioned reasons for installing and continuing to use toilets were again related to the environment. Other reasons individuals mentioned for installing toilets were related to the need for an alternative to a flush toilet and also related to the pilot program opportunity. Other reasons individuals commonly mentioned continuing to use toilets included that the toilet works (Figure 3a and 3b). When individuals were asked whether they recommended a toilet to others, most said they did for reasons related to the environment, the resource (i.e. the compost), and ease of use. However, many responses also highlighted that it depends on the individual, available resources (for instance cover material source), and neighbors (Figure 4).

Describe and explain how the pilot composting toilets currently function

The most commonly mentioned structural issue related to the toilet was the delamination of the wooden top (Figure 5). Individuals attempted to fix this with paint, a new material for the top, or via protection from the sun. Recipients identified their own knowledge, WMG resources, or the advice of other individuals as the sources of solutions related to structural issues (Figure 6). In terms of maintenance, insect control was the largest issue both initially and recently. (Although the frequency has gone down slightly, in recent use compared to initial use, related to issues with insect control) (Figure 7a and 7b). Solutions indicated to deal with insects were moth balls, moving to another barrel/chamber, using another toxic insect killer for temporary treatment, adding a plate, or some other method (Figure 8). The plate was a very promising solution from observation and should be recommended to other users who are looking for a non-toxic effective solution. There are some recipients who expressed difficulty obtaining cover material. (Actually finding cover material may not have been an issue but finding cover material, which was also free, and accessible was commonly an issue). While many recipients found sources of cover material from neighbors, woodworker acquaintances, Bear Joinery (and other businesses), and personal on site resources, there is a need for i) the promotion of the already identified free sources of effective cover material & ii) the identification of more sources of free cover material.

Explore the support recipients need/want

The majority of recipients did not want/need future construction related support from WMG (Figure 9). However, all recipients said that WMG should continue to support future composting toilet recipients (Figure 10). In WMG’s support of future users, pilot recipients had various suggestions. The highest mentioned suggestion from recipients was related to communication. This included individuals who felt that there should be more social events or online group interactions and training sessions. Recipients also had suggestions related to the politics of the toilets. This included individuals who had suggestions about striving to make composting toilets legal across Arizona and clarifying the current issues surrounding legality to new users. Additionally, recipients had suggestions related to toilet resources. This included individuals who thought WMG should help to provide resources to solve bug issues and also provide examples of a larger variety of composting toilets. Recipients also had suggestions related to staff. This included individuals who thought a WMG point person was needed to answer questions related to the toilets. Finally, recipients had suggestions related to the scope of these toilets. These individuals felt that the project and idea of composting toilets should move into other cities and states (Figure 11). Lastly, when asked about any changes that would be made if the recipient could redo their experience with their toilet, the most commonly mentioned response was related to location. In other words, recipients wished they had put more thought into whether the toilet was inside or outside, distance of toilet from house, and orientation of the structure surrounding the toilet (Figure 12).

1 Robles, Pedro. (2014) Watershed Management Group’s “Closing the Loop—A Desert Soils Education and Action Program.” University of Arizona. Report.


Figures Report 1.pdf (this page will be uploaded soon)