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| Sustainable Building Sourcebook | ||
| Chapter: Water | ||
| Composting Toilets, Graywater Reuse | ||
| CSI Numbers: 15414 Composting Toilet Systems | ||
| Introduction: | ||
There are several types of composting toilets, all based on the goal of water conservation. Waterless and forced-air composting toilets produce a valuable fertilizer. Electric toilets burn the waste. Some models use a very small amount of water or a chemical foam to assist the passage of waste to the composting chamber. When properly installed, none of them create odor or health problems. | ||
| At-A-Glance Notes: | ||
| Technology: | ||
| The technology for composting toilets is well developed. Newer models that offer complete self-contained wastewater integration with graywater systems are now available. | ||
| Suppliers: | ||
| Local off-the-shelf availability is limited. | ||
| Cost: | ||
| Composting toilets are cost-competitive with many septic systems. However, they are not cost-competitive with centralized wastewater systems, particularly in Austin, where sewage sludge is composted. | ||
| Public Acceptance: | ||
| There is limited appeal for composting toilets. Maintenance requirements vary by manufacturers, and although minor for many systems, they may prevent wider interest. People are typically interested in composting toilets when they do not have other satisfactory toilet options (e.g. lack of space for a septic field, impossibility of using heavy equipment on a site). | ||
| 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 (ATCHD) must issue a permit to install such toilets. Cost of the permit depends on whether the unit is National Sanitation Foundation (NSF)-approved or an engineered unit. A composting toilet is considered an alternative system and must be inspected annually by the ATCHD for a fee. Other municipalities may have other requirements for permits, inspections, and fees. Percolation tests do not apply if a sewer is present. | ||
| Considerations: | ||
Composting toilets are lawful in Austin provided the units are approved by the National Sanitation Foundation [NSF] or engineered by a registered PE. 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 cost 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 for standard toilets [1.6 GPF] makes the water savings from composting toilets quite low. If a home does not have central wastewater services, a composting toilet may be practical. Coupled with a sub-surface graywater irrigation system (see Graywater Systems), installing a composting toilet can alleviate the need for a blackwater septic system; however, current state law prohibits water from toilets to be considered graywater. Always check state and local regulations before deciding on depending solely upon such a system. There are commercial products available that range in cost depending on their complexity. In areas where these systems can supplant large investments in septic systems, they are cost-competitive. |
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| Guidelines: | ||
There are two types of composting toilets: self-contained and split units. Self-contained units combine the commode and the composting compartment in a single unit. Split units have separate commode and composting components. The composting component must be positioned below the commode section. Some designs may use a small amount of water or foam to flush the commode. The storage chamber must be accessible for compost removal. This is an important design consideration for homes that have a concrete slab floor or a flat site. Just like standard toilets, composting toilets have a vent to exhaust gases and prevent odors from entering the living space. Many models are fan-assisted. Several manufacturers offer heaters to accelerate the decomposition process in cold weather. Solar-powered models are available. Commercial composting toilets are available in a variety of sizes to serve different sized households. Water, Fig. 1
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| Resources: | ||
| Professional Assistance: | ||
See "Engineers" in the Yellow Pages |
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| Components/Materials/Systems: | ||
(Check with the listed companies regarding NSF approval) AlasCan of Minnesota, Inc. Biolet USA, Inc. Bio-Recycler Co. Bio-Sun Systems, Inc. Clivus Multrum, Inc. EcoTech Carousel Composting Toilet Eco-Wise The Home Place Jade Mountain Inc. Sancor Industries Ltd. Sun-Mar Corporation |
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| General Assistance: | ||
Austin-Travis County Health Department The Humanure Handbook; A Guide to Composting Human Manure , Jenkins Publishing, 1995. (800) 689-3233 National Small Flows Clearinghouse Texas Water Resources Institute |
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