A Sourcebook for Green and Sustainable Building

Composting Toilets

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Contents:

CSI NUMBERS
DEFINITION
CONSIDERATIONS
COMMERCIAL STATUS
IMPLEMENTATION ISSUES
GUIDELINES

RESOURCES

CSI Numbers:

DEFINITION:

 A waterless composting toilet uses no water and produces a valuable fertilizer. There are some composting toilets that use a very small amount of water or foam. The water using kinds will typically be part of a total wastewater system.

CONSIDERATIONS:

 Composting toilets are lawful in Austin provided the units are approved by the National Sanitation Foundation (NSF) or engineered by a registered Professional Engineer.

Austin presently composts sewage waste derived from its central wastewater system. The composted product is marketed as a landscape fertilizer called Dillo Dirt. For this reason, it may be difficult to justify the extra expense and maintenance needs of a composting toilet in order to gain compost when a city sewer line is available. Additionally, the low volume of water required to be used by toilets in Austin (1.6 GPF) makes the water savings from using a waterless toilet quite low.

If a home does not have central wastewater services, a composting toilet may be practical. Coupled with a sub-surface greywater irrigation system, the composting toilet can avoid the installation of a blackwater septic system. Although kitchen sink wastewater is defined as blackwater along with toilet wastewater, the Austin-Travis County Health Department may permit the discharge of kitchen wastewater with greywater in a sub-surface irrigating system if the site conditions are suitable.

There are commercial products available that range in cost from $1000 for simpler units to $10,000+ for fully integrative wastewater/composting systems. In areas where these systems can supplant large investments in septic systems, they are cost competitive.

Commercial
Status		 Implementation
Issues
technology suppliers cost financing public regulatory
Composting Toilets green yellow red black black red
Legend
green Satisfactory
yellow Satisfactory in most conditions
red Satisfactory in Limited Conditions
black Unsatisfactory or Difficult

COMMERCIAL STATUS

TECHNOLOGY:

The technology for composting toilets is greatly improved from models offered over 10 years ago. Odor problems are eliminated in the better models and performance is satisfactory. Newer models that offer complete self contained wastewater integration with greywater systems are now available.

SUPPLIERS:

Local availability limited.

COST:

Composting toilets are cost competitive with many septic systems. From a user's standpoint they are not cost competitive with centralized wastewater systems, particularly those that compost the sludge such as Austin's.

IMPLEMENTATION ISSUES

FINANCING:

Fear of limited resale opportunities and values may affect lenders.

PUBLIC ACCEPTANCE:

There is limited appeal for composting toilets. The maintenance requirement, although minor for many systems, prevents wider interest.

REGULATORY:

Ordinances #880310-H and #880310-I address composting toilets and are a part of Chapters 6-10 of the Austin City Code. The Austin-Travis County Health Department must issue a permit to install a composting toilet. The permit cost is $200 for an NSF-approved unit, or $300 for an engineered unit. The composting toilet is considered an alternative system and must be inspected annually by the Health Department. The inspection fee is $30. When the composting toilet is outside of the City, there is not an annual inspection requirement. The licensing procedure outlined in the Greywater Irrigation Section is required for composting toilets (percolation tests do not apply if a sewer is present).

GUIDELINES

  • 1.0 Types of composting toilets

    •

  • 2.0 Characteristics

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  • 3.0 Suitability for Austin conditions

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    This file last updated on Wednesday, March 21, 2007