Mother's Compost Commode

Image Gallery Solar-heated air enters the composting cabinet via a 3-inch duct, and a 72-inch vent pipe assures rapid airflow for proper compost drying and odor elimination. MOTHER EARTH NEWS STAFF

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It's pretty hard to deny that the common flush toilet is the easiest, most "euphemistic" apparatus yet invented for disposing of human waste. Trouble is, it's also the most wasteful: Just flip that chrome lever and — whoosh! — five gallons of potable water take the plunge, to carry away a few ounces of solid or (even more wasteful) liquid effluvium.

So what's the best alternative available to the growing number of environmentally minded folk who are hunting for a convenient, economical way to dispose of human waste without creating a water-squandering situation? That's the question Eco-Village staffer Jay Herndon asked nearly a year ago when he decided to assign himself to Project Privy. His mission: to build a good, ecological commode.

The Search is On

By examining and weighing the options — water-saver toilets, nonrecycling waterless commodes and waterless waste recyclers (better known as composters ) — Jay saw almost immediately that the all-around most sensible choice would be a composter. In addition to disposing of sewage without the use of any water, this improved outhouse system offers the bonus of organic fertilizer.

Once Herndon had decided on waterless waste recyclers, his next step was to look around at what composting toilets others had come up with, both commercially and on a homebuilt basis. He soon learned that the U.S. Forest Service in his neck of the woods was using a composter. It was a "stair-step" model, the type that requires a large (4-by-4-by-12 foot) subfloor space, and needs close to a two-year accumulation period for a batch of composted material to work its way down to the bottom, where it can then be removed. A good effort on the part of the forest service, but not what he was looking for.

A second model, called a "two batcher," had been tried by several local do-it-yourselfers, but it wasn't all Jay hoped for either: It required too frequent shoveling of the heap from one composting bin to another. Moreover, both of the units he inspected evidenced some degree of insect infestation and, you guessed it, odor.

The next step in the search for the perfect waterless toilet was to scout out the commercial offerings. Here, the main problem was price: The average cost of commercial composters is in excess of a thousand dollars, and such units almost always require an external source of power to provide venting and drying heat.

So, by identifying the characteristics that he wanted to avoid, Jay came up with a set of standards for his composter: It should take up as little subfloor space (especially vertical) as possible, use no conventional power to supply heat, require minimal servicing and handling of waste heaps, produce no odors, be bugproof, and be considerably less expensive to construct than even the least costly commercial model.

The Evans Coprophage No. 3

Our compost sleuth now made a thorough survey of the available literature. Of the many designs for owner-built systems Jay studied, the Evans Coprophage No. 3 (presented in Rodale's excellent book Goodbye to the FlushToilet ) seemed to make the most sense. This unit met many, but not all, of the requirements, the primary shortcomings being that it offered no provision for the sanitary disposal of liquid wastes (they were simply dipped out) and that it depended on a small electric fan for venting. Furthermore, there was no heat source — an important, almost mandatory, element in any truly efficient composter.

But, despite these undeniable flaws, the overall design of the No. 3 was sound. A two-stage composting process employed a rotating basket drum that was set above a second-stage decaying shelf. So Herndon decided to adopt the model as the starting point from which he created his own composting toilet.

An Inside Look at Mother's Outhouse

Today, what you first encounter when you visit the final product at the Mother's 622-acre EcoVillage research center is an outhouse-type structure of rough-sawn pine. In fact, if you approach the commode from the front, that's all you'll see. (You'd have to go around back to spot its subfloor portions, which are partially buried in the side of a hill.)

Open the door and you'll be standing inside a screened-in porch, a feature added to help bar bugs. An inner door, this one weathertight, opens into a fresh-smelling room that's illuminated by a small photovoltaic-powered light. A glance around reveals the source of the pleasant aroma: split-cedar shingles covering the walls. A small urinal is attached to one wall, and an outhouse-type bench with a tight-fitting lid completes the scenery. Lift the lid and you'll see a conventional toilet seat. To lessen visibility "down below," the inner walls of the composter's lower parts have been painted flat black.

Each of these touches serves a purpose. The toilet lid is airtight to keep out insects and to help maintain a rapid vent flow when closed. The urinal helps direct liquid wastewater around the drying heaps and sends it down a drain at the bottom of the cabinet, where it's eventually released into a small, gravel-filled subterranean leaching trench.

The wall covering of cedar shingle not only gives the interior of the privy an attractive appearance and fragrance, but also helps to fend off bugs (there's something about cedar that the little crawlers and fliers can't stand). In addition, there's a sandwiched layer of rolled fiberglass insulation between the inner shingles and the outer pine. To see more of the composter, you'll have to walk down the hill (it's not all that much of a hill) and around behind the privy.

The subfloor portions of the commode are enclosed within a 4-by-4-by-5 foot poured-concrete-block cabinet, the inside of which is water- and lightproofed and — as mentioned earlier — painted black. The outside surface of the cabinet is lined with inch-thick, foil-faced insulation (if you want to get technical, it's called polyisocyanurate) and is finished with a coating of stucco.

On the west side of the building you'll spot a crank handle that's used for periodic rotations of the composting drum. Up the east side of the structure runs a 12-inch diameter galvanized duct pipe that vents the composting cabinet to prevent odors from entering the "comfort room" when the seat lid is raised. The pipe is painted flat black to increase upward venting flow, extends high enough to exhaust its gases above head level, and is capped with a wind-driven turbine ventilator.

At the lower back of the concrete composting cabinet you'll see a 3/4-inch-by-2-by-4 foot plywood door that provides easy access for removal and cleaning chores. An insulation-wrapped, 3-inch diameter galvanized duct pipe is vented in through the plywood access door and carries a flow of high-temperature solar-heated air into the composting chamber. That warmth comes from the flat-plate solar collector that stands just behind the privy. It has a collection area of 32 square feet and is of the inexpensive-to-build fluorescent-light-tube type. (For more on the subject, see Mother's Fluorescent Tube Solar Collector, September/October 1978.) Jay used this particular suncatcher because it was "just lying around," but he points out that any type and any size of solar air-warmer will work, as long as it provides heated air to the composter.

As a final, high-tech (and expensive!) touch, the south-facing slope of the building's roof sports a photovoltaic panel to provide power for the interior light.

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