The Sunny John designed and prototyped by John Cruickshank of Going Concerns Unlimited

Table of Contents

·  Introduction

·  Just what is a Moldering Toilet anyway?

·  Advantages?

·  Disadvantages?

·  The Basic Operation

·  Design Considerations

·  Building Design

·  A Word About Costs


Design for a Solar Moldering Toilet


Introductory opening provided by Peter Bane, editor of The Activist, the premier journal of Permaculture consciousness in the Americas.

One of the most basic characteristics of any human community is how it deals with its body “wastes.” Rich societies have developed quite complicated and expensive systems for removing human wastes from houses and cities, usually by dumping them, treated to one degree or another, into subsoils or bodies of water. While this avoids most of the problem of contagious diseases which can be spread by contact with human wastes, it hastens the loss of soil nutrients from farmland and it carries other risks of contaminating surface and ground water.

In contrast, traditional peoples and societies with lower levels of energy and resources available to them have usually disposed of body wastes by returning them to farm and garden soils. While these practices are more ecologically sound because they close the nutrient cycle from field to table and back again, they have often been linked with high levels of bacterial, viral, and parasitic infection and mortality.

Historic advances in public health were associated with the installation of underground sewer systems in European and North American cities, ensuring that public officials in those countries remain heavily divested in technologies of disposal. No politician or government official wants to be even remotely connected with an outbreak of cholera! This common sense, but incomplete, view has become more and more entrenched as society has become increasingly regulated and homogeneous. Extending the mentality of “out of site, out of mind,” the septic tank and leach field system has become the disposal method of choice in rural areas, while an economic tug-of-war goes on in the suburban fringe between municipal sewers and septic systems. Since passage of clean water legislation nearly 30 years ago, city and town wastes have been more thoroughly treated by municipal sewage plants, mitigating some of the worst pollution of streams, lakes, and coastal water, but at a huge and increasing financial and energy cost.

In choosing an appropriate technology for treating human waste, how do we walk a middle ground? To render wastes harmless for reuse in the soil and to ensure that they are returned to the agricultural food web we need to look beyond the flush toilet, the pit privy, and the open sewer. To take responsibility for eating and shitting, we need new tools.

Appropriate methods

Waste treatment can be categorized as either “wet,” in which the wastes are diluted with water and the resulting sewage is settled, filtered, oxygenated and otherwise treated; or “dry,” in which the solid wastes, mixed with urine or not, are broken down by macro- and microorganisms, faster or slower, hotter or cooler. Hot composting destroys pathogens quickly, rendering the “humanure” safe for agricultural use, while slow cool composting, called “moldering” can accomplish nearly the same degree of sanitation with less handling over a longer period of time. Numerous approaches, from simple bucket systems through multistory inclined chambers, to rotating drums, to shallow burial have been devised, each with its advantages and disadvantages. Extensive private and government research and long-running installations have proven the ability of constructed wetland systems to remove pathogens, nutrients, BOD (biological oxygen demand), and even heavy metals and toxic chemicals from both grey- and black-water wastes on every scale from a single household to municipalities of many hundred thousand people. Many of these subjects have been explored in the journal PermaCulture Activist. Let’s focus here on cool composting or “moldering” toilets.

Peter Bane, editor, The Activist

To Table of Contents

Just what is a moldering toilet anyway?

Typically with a composting toilet, the human waste is deposited in the same container or vessel that will be treating the waste, transforming it on-site into a usable resource. A “composting” process is typically associated with fairly fast transformations, in the neighborhood of weeks and months. It necessarily requires quite specific conditions to do it’s magic in such short time periods. Usually, this requires elevated temperatures, enhanced oxygen and air mixing, proper moisture control and careful control of the waste material makeup and loading rate. The toilet itself will include anything from electric heaters and mechanical stirrers to sophisticated baffle arrangements. It sometimes incorporates a portable collection device, for the waste may have to be transferred to another location for composting. On the other hand, a moldering toilet is simply a composting toilet that is built to allow for very long term slow composting in place – the waste molders, rather than composts, much as leaves and plant debris “molder” on the surface of soil through the action of bacteria, fungi, and microorganisms. With moldering, the “technology” applied for waste treatment is mainly isolation, and time itself!

To Table of Contents


Composting and moldering toilets use no water. On the other hand, the flush toilet is pretty much the be all and end all of human living in much of the modern world. The major objection to all variations of water-based waste disposal is the expense of infrastructure. Rural septic leach field systems cost anywhere from $6,000 to $20,000, while municipal sewer connections are no less costly and require continual energy inputs to maintain. Basically both take drinking quality water, dump sewage into it, use the water to transport the waste, and then attempt to remove that sewage from the water somewhere else. Most water-based systems give little consideration to completing a cycle where it begins – on the farm or in the garden, instead they turn a locally useful resource into a regional waste nightmare. Worst of all, water-based systems are usually installed for the lack of knowledge of legal, workable alternatives.

There are immediate advantages to using a long-term moldering design that requires maintenance only once every few years. Besides the work saved (over hot composting), moldering lends itself to maintaining an atmosphere around the home of simplicity and repose. Traditional portable-sized composting toilets need frequent maintenance; their processing is much quicker and so their products need more frequent handling. A moldering toilet may only need attention every four to five years if you like. As the size of the moldering container or vault decreases, the time span can shrink to as little as one year and still yield properly treated products to cycle back into the system.

Portable composters are efficient waste processors, so their overall size is fairly small. They can handle their load quickly, and so do not need to have large amounts of internal storage. They are designed to treat quickly, and then need unloading. Herein lies the weakest point in their design. If the loading characteristics of a composting toilet ever change significantly beyond the design limits, it will stop doing its job of transformation. It will just fill up and need to be abandoned or cleaned of raw waste! (That workshop you dreamed of hosting at your site – with 35 people showing up for 14 days – will mean only one thing!) On the other hand, a design which incorporates large storage times will also be able to handle loading fluctuations without breaking down. The moldering approach to design leaves you with more time to play with and is more resilient.

The main reason for composting wastes, of course, is to make available to the soil, for which you are permanently indebted, all the products of your labor and partaking. Completing this one simple cycle quietly and with little effort stands out as the major advantage. Whatever the method, an important ritual for any and all can be letting the products of our bodies be returned to the Earth from whence they came.

To Table of Contents


The obvious reason not to choose any on-site dry waste treatment system is that sooner or later you will have to handle human waste directly. This will be the point of departure for many; the thought of it will send the squeamish running. That is just the way things are, and will always be the objection to any kind of composting of human waste. However, do not fear: when properly functioning, the moldering toilet produces material which looks and smells just like forest duff.

The second disadvantage is the size of the chamber required. Portable composting toilets and water-based systems don’t need a lot of building space, whereas a moldering toilet must incorporate a large chamber in order to store up several years’ wastes. And this chamber must be beneath the toilet room, sheltered from severe cold, and protected from vermin.

As well, with any new approach being prototyped and perfected, the lack of experience and skilled execution of designs may be a problem. While the general approach to this type of waste treatment may be well understood, a lack of the hands-on knowledge of the finer details of construction and use may put the whole process in jeopardy. (This report is intended to provide practical introductory guidance only. The perfect design always requires the application of the designer’s imagination to the basic principles. Workshops are available.)

The other possible hindrance is the legality (or lack of it) that may surround this approach. I don’t know of any law that makes it illegal to do your thing in a bucket (essentially, that is what all composting toilets amount to), but what you do with the bucket when it needs emptying may be an issue! Let common sense and the applicable codes determine the right and fitting thing to do. Composting toilets are accepted in many areas of the country now. Look for precedence in your area, and go from there.

The original impulse for the first design I considered sprung out of a need for a restroom at a working farm site that hadn’t a waste water system available to expand. It needed a second facility for farm hands and many visitors to relieve the strain on the existing septic system (not to mention the strain on the carpet and privacy of the farm manager’s household!) A simple pit outhouse was out of the question – a nearby well would be threatened. The whole idea of on-site recycling was not objectionable; it was being actively pursued in most areas already; and the opportunity to house the toilet in a structure built to Eco-friendly building standards came about by lucky providence – a project was needed to demonstrate timber frame and straw-clay wall construction methods. The vision slowly grew into a full expression of simple beauty and natural function. The reason why we built the moldering toilet as we did came to relate more to this expression of a vision than simply an effort to satisfy a need. It eventually became a symbol for all to see, and for all to know. Why would anyone want a moldering toilet? The answer to this question relates to the advantages of having one. Namely: on-site human waste recycling, infrequent maintenance and no water-based sewage infrastructure requirements and expense.

To Table of Contents

The Basic Operation

Implicit in the moldering process is a long resting period: the filled chamber must be left undisturbed for a minimum of six months, while bacteria and microorganisms break down the waste. This requires that you build a second vault to be used while the first is resting. The vaults can be sized to hold more than six months’ loading, allowing for a longer resting period, up to several years. As the first one is filled, it is capped off, and use directed to the other. Once the second vault is nearing capacity, the first vault’s contents can be harvested as finished compost, ready for the orchard and fields. The second vault can then be capped off, and the first brought back into service.

My first design used removable 55-gallon containers in each vault to allow for more flexible loading rates and easier handling of the finished product. Two of these barrels provide a year’s capacity for a family of four. Alternatively, the entire vault can be modified to be used as a collection vessel.

During the summer, the design relies on wind power for ventilation, and ambient air temperature for heating. During the winter, when the sun is lower in the sky, solar energy is used to boost venting and to heat both the space and the vault.

To Table of Contents

Design Considerations

If the waste is to be collected for long periods, there must be enough elevation from the floor of the vault to the level of the toilet stool to allow a pile to accumulate. Four feet or more is not unusual. The overall size of the vaults will be determined by the projected loading requirements and the space available.

Access to the vault will have to be provided for harvesting. A wheelbarrow, cart or vehicle will likely be required, as the volumes involved will be large. This means a large door which seals well, and a location adjacent a flat, unencumbered space for unloading and transferring the material.

The vault must be very well ventilated too. Ventilation provides the oxygen required to maintain aerobic bacterial activity, thus reducing odors. Ventilation will also evaporate excess urine and help to keep the toilet room fresh. A vent stack which draws air through the toilet seat, around and under the pile before exhausting it above the roof line will serve these purposes well. If free energies such as sun and wind can be harnessed for this purpose, operating costs will be low and reliability built in. Of course, if passive powering is not possible, the design will be forced to rely on mechanical ventilation.

The waste must not be allowed to get too cold. This means the vaults will need to maintain temperatures above normal ground and winter ambient temperatures. Temperatures approaching 90 degrees F are not too high, while 70 degrees F would be a good design target.

The last matter to consider is that the building must be built soundly and tightly. All entrances and accesses must be made vermin- and fly-proof. Door seals and gaskets must be used, a seal around the toilet seat must be used and the vault and its access doors must be weatherstripped as well. The vent piping, if used, must be screened as with all openings to the outside. Flies can be a major concern, as they can readily infest the vault and room. Spiders can cast an impenetrable web in the venting system if there is a payload of insects to harvest. Pay careful attention to the integrity of the structure!

Summarized, the following criterion need to be met:

· space,

· ventilation (for odors and moisture),

· heat (for breakdown, comfort and evaporation),

· integrity (to prevent unwanted vermin and pests),

· harvesting access.

To Table of Contents

Building Design

When I built my first moldering toilet it had to be placed in the central working area of the farm. There was no opportunity to add onto the farmhouse. We had no elevations to use to our advantage. The design had to be built around a modified pit setup. The space also did not allow direct solar exposure of the vault for heating.

I built a timber-frame, straw-clay structure, almost totally free of modern materials. Straw-clay walls lent themselves well to the needs of the building. Their permeability provides many air exchanges per hour to handle part of the ventilation requirements for fresh air. The mass of the walls makes heating easier. Robert Laporte of The Natural House Building Center provided the skilled know-how and practical guidance needed to apply this ancient European wall system to the project. The small size of the building required only a few framing members, so it was easier and cheaper to build with a timber frame. Since I was concerned with groundwater contamination I built a concrete foundation and vault. To take advantage of the investment in all this mass, I surrounded the foundation with closed cell insulation. Because much of the foundation was above ground, I sheathed it with galvanized sheet metal for protection from the elements. I used a solar collector and direct solar exposure through south facing windows to heat the building. To prevent overheating, we had to exclude massive summer solar gain with a large south roof overhang.

I had to design in more ventilation capacity than natural convection alone could provide. Winter sun coming in through the windows heats a 10-inch metal solar “chimney”. The solar chimney is effective only when the sun is low in the winter sky, however. In the summer a wind-driven turbine vent, of the type generally available for attic and roof ventilation, enhances airflow. A temperature-controlled automatic damper, sold as a companion to the turbine, regulates venting: it is adjusted to begin opening when the stack temperature reaches 50 degrees F and to open fully at 70 degrees F. For an extra heat boost in the winter months, we converted part of the south glazing into a solar hot air collector, directing the heated air into the room.

Access for harvesting was only possible on the north side of this small building. We built a small ramp down into the vault, and used a regular cellar door arrangement for sealing it off. We placed 55-gallon plastic barrels for collection containers, modifying them slightly to our needs. The tops were cut off in such a way as to re-use them as well-fitted perforated strainers on the bottom of each barrel. Each top was drilled full of 5/16-inch holes and supported up off the bottom with a few broken bricks. The sides of the barrels were heavily perforated with 5/16-inch holes for air exchange, and the very bottom has a ring of 3/4-inch holes for drainage. Each barrel had an initial 2-inch lining of coarse wood chip over the strainer to prevent solids from leaking. The portability and low cost of the containers ($10 as a “non-returnable, no deposit” item) makes it easy for us to cycle more of them into the operation if needed. The vault sizing is sufficient to allow for their use directly with shovel harvesting if you build a separating wall and modify the venting passages. Using the vault alone is an option, and would provide a 4 to 5 year cycle between the two chambers. To provide a thermal flywheel in the design, half the vault is filled with large stones, which are placed just before the vent openings in order retain extra heat in the building.

The range of options in moldering toilets is much wider than what I have built. If the toilet is to be integrated into an existing house, the scope of design alternatives changes. Ideally, the best arrangement will involve direct solar exposure to the vault, rather than the room. This means placing the room on the second floor, on the south side of the house, with the vault space at ground level. The venting can be set up to take better advantage of the sun and the wind, avoiding excessive solar gain to the room by rearranging the floor plan and using solar hot air exchangers exclusively.

I used two stools in a side by side bench arrangement, but you can just as well have the two stools facing each other, the sealed unused stool area used as a small counter instead. You can build one stool on a small bench that is portable and seal the other vault at the floor level. That way you will gain the extra floor space, moving the whole bench and stool to the opposite vault when needed. The toilet stools can be placed on the north or south side of the room, in the sun or the shade.

You need not feel bound to the idea of using portable containers. Two separate vaults, built large enough, function well if their access allows for easy shoveling when it comes to harvest time. Vault design like this usually requires sloped bottoms and venting of the heap. Just keep in mind the basic requirements: space, ventilation (for odors and moisture), heat (for breakdown and evaporation), integrity (to prevent unwanted vermin and pests), and harvesting access.

To Table of Contents

A word about costs

My first moldering toilet project (in 1993) involved the construction of a totally separate building, with it’s own foundation, framing and roof. If the toilet be included in a house design, most of this expense can be avoided. The cost of walls, roof etc., will already be included in the basic construction of the home. The added cost of the toilet may only be the hardware items involved. The building materials cost alone for my first design was only $357 off the shelf. New hardware costs came to a total of only $335. Since then I have contracted the construction of another moldering toilet locally for $1200 complete, including paid labor. A slightly smaller arrangement designed for the sloping site of the Central Rocky Mountain Permaculture Institute has been constructed for a cash outlay of only $150.

The original moldering toilet, now dubbed “The Sunny John” is open for viewing at:

Sunrise Ranch

5569 North County Road

Loveland Colorado 80538

(970) 679-4274

To Table of Contents


Occasionally Going Concerns Unlimited offers weekend workshops detailing the construction and operation of a new Sunny John to grace the planet. Keep in touch to hear about them as they are scheduled.

To Table of Contents

John Cruickshank runs Going Concerns Unlimited, dedicated to “getting your concern going!” He has provided electrical/mechanical and educational services at Sunrise Ranch since moving there from Calgary, Alberta twelve years ago. Fully detailed construction drawing plans for both the original flat land design and the sloped site design of the Sunny John are available for $20 postpaid. Contact the author at (970) 679-4342 for plans, advice and questions.