Barrel Composting Toilet System

(Updated 5/14/2016)


For additional information, see our other web pages on composting toilets:
-Composting Toilets: An Introduction
-Composting Toilet Regulations
-Bucket-to-Barrel Composting Toilet


2016 Update:

The following 3 recommendations are based on a report by Darya Anderson of the Bureau of Applied Research in Anthropology, School of Anthropology, University of Arizona.  The report was a follow up to the Watershed Management Group's Composting Toilet Pilot Project in which approximately 18 Barrel Composting Toilet Systems were used in residential settings over a 2 year period in and around Tucson, Arizona.  The pilot project was funded by a grant from the Environmental Protection Agency and facilitated by the Watershed Management Group and the Arizona Department of Environmental Quality.

1) Urine diverting funnel has a better user interface with alternate installation (see Urine Diversion System)

2) Aluminum or concrete tops are recommended for outdoor installations (see bottom of Construction and Installation Manual). 

3) Insect plate is recommended for all outdoor installations (see Owners Manual)

A 3 barrel system suitable for full-time use by 2 people. 


Detail of toilet top.


The Barrel Composting Toilet system is similar to our Bucket-to-Barrel Composting Toilet system, except that it is designed to function without the bucket aspect.  Instead, a toilet seat and ventilation system are fitted directly on top of a 55 gallon polyethylene barrel which serves as a composting chamber.  By eliminating the need to empty buckets, the design comes a step closer to being permitted in some jurisdictions.  It has been chosen as one of 2 designs to be tested in a composting toilet pilot project being permitted by the Arizona Department of Environmental Quality and funded by an Environmental Protection Agency grant to the Tucson-based Watershed Management Group

The Barrel Composting Toilet system features zero leachate discharge to native soil, full vector control, effective aeration and moisture distribution and is constructed of durable, easily cleaned and non-corrosive materials. The design can be installed indoors or outdoors.  In outdoor locations, a prototype has performed well for the past 6 years in climates as diverse as Arizona and Oregon. In outdoor locations, it must be used in mild climates to insure sufficient heating for effective composting.  For more information, see our Guide to Appropriate Climates for Outdoor Installations webpage. 

In addition to the above mentioned features, we believe that pathogen elimination is equal to or better than many NSF certified composting toilets due to the thorough aeration and moisture management inherent in the design.  Also, whereas most proprietary composting toilets are continuous systems in which fresh material is continually being added to the same composting chamber in which finished material is being removed, the Barrel Composting Toilet System is a batch design in which aging material is completely segregated from fresh material, thus providing an extra degree of safety.  For information on microbial testing of compost from the Barrel Composting Toilet System, see our Pathogen Testing Methods and Results webpage. 

When managed according to instructions in the owner's manual, the toilet is simple to use and odorless. 

Material costs are about $325 for a 3 barrel system designed for 2 adults in full time use.  This assumes new and corrosion-resistant materials for which engineering specifications are available.

System Overview:

The Barrel Composting Toilet system is designed around multiple 55 gallon high-density polyethylene barrels that are standard in the container industry.  The barrels are food grade and fully recyclable.  A removable platform is secured on top of one barrel (the "active" barrel).  The platform features a toilet seat, ventilation system and vector control.  When the active barrel is full, the platform is moved to an empty barrel (this empty barrel is now the "active" barrel).  The full barrel (now called an "aging" barrel) is capped with vector control screen and rain cover.  The contents of the aging barrel continue to compost for a minimum of 4 months before being emptied.  The total number of barrels required for the system is based on the number of people using the toilet.

Aeration is provided by the use of a Compost Crank.  (Disclaimer: We do not sell this tool or have any financial connection with Lotech Products, the manufacturer of this product.)

The design incorporates urine separation, which allows urine to be used as fertilizer for plants. 

Details of the Barrel Composting System are provided in the various links below.      

--Appropriate Climates for Outdoor Installations

--Capacity Calculations and System Sizing

--Construction Material List

--Construction and Installation Manual

--Top Layout

--Owners Manual

--Instruction Sheet (to be posted beside toilet)

--Urine Diversion System

--Pathogen Testing Method and Results


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