A Guide to Composting Toilets: Making Compost Happen

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Photo Courtesy Sun-Mar
Composting toilets, such as this one by Sun-Mar, turn human waste into compost and can reduce household water consumption by at least 25 percent.

Have questions about composting toilets? We have answers:

How does a composting toilet work?

Composting toilets utilize bacteria and fungi (similar to what’s in garden composters) to turn human waste into a dry, fluffy, odorless material called humus.

What’s included?

A composting toilet has a place to sit, a composting chamber and a drying tray. Most models combine all three elements in a single enclosure, although some models have separate seating, with the composting chamber installed in the basement or under the house. In either case, the drying tray is positioned under the composting chamber, and some sort of removable finishing drawer is supplied to carry off the finished product.

What options are available?

Composters are available in batch (multiple-chamber) or continuous (single-chamber) processors. Some composting systems include incinerators that require gas or electricity. Self-contained units can be installed by homeowners; systems require a professional.

Do they smell?

Unlike outhouses or port-a-johns, a composting toilet is not supposed to smell. If it does, something’s wrong, and it’s time to call a professional.

What’s the end product and what do you do with it?

You’ll find humus–a fluffy, dry, odorless material–in the finishing drawer. Empty the drawer every few months. Humus is compost and can be used to fertilize fruit trees and ornamental plants. Check state and local regulations to see if it’s legal to use humus as fertilizer in your area or whether you need to bury it or have it hauled away by a licensed seepage hauler.

Where should you put (or not put) a composting toilet?

If you’re thinking about installing a composting toilet in an apartment or single-family home that’s hooked up to a municipal sewer system, check state and local regulations first to see if that’s legal; in some areas it’s not.

The most popular uses for composting toilets are vacation cottages and weekend cabins that don’t get constant use.  

Composters offer a great waste-processing option in areas that aren’t connected to sewer systems and where conventional septic systems aren’t feasible, such as in lakeside cabins and on clay soils.

How much do they cost?

Consider a composting toilet an investment. Prices start at $1,000 and go up–way up.

Sources: Oikos Green Building SourceGaiam Real GoodsComposting/Toilet.org

Composting Toilet Resources:

(800) 387-5126

(800) 524-6538

Clivus Multrum
(800) 425-4887

(888) 341-0782

Further Reading: The Composting Toilet System Book by David Del Porto and Carol Steinfeld (Center for Ecological Pollution Prevention, 1999)

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