Basically, a solar oven with a toilet seat. The power of the sun roasts the “product” at extremely high temperature and turns it into powder. Solar Toilet require full sun, so a stretch of cloudy days simply make the solar toilet into a composting toilet. A rotation mechanism is built in and a small drain allows any liquid to drain away into the septic out line just before the septic toilet

Solar Toilets do work and have been tested by the New Mexico state Health department as being safe. Solar Toilets require constant maintenance and are for a specific type of person. Most of the general public will probably not begin using solar toilets beause you really get to see the waste. This is un-acceptable to the average person on this planet as we want to flush it away.

There are solar toilets in use around the world. The contained sewage treatment system, called Botanical Cells that are used in Earthships to treat sewage is the most effective way to treat residential sewage while still providing what people want, to flush our waste away. This is fine, our lifestyles do not have to change to live sustainably.

A solar toilet can be installed in any building whether it is an Earthship or not. They must however, be palced on the south side of the structure (in the northern hemisphere), as the sun is what makes them work.

The solar toilet should be in a little closed off room (see Earthship Volume III) with a small gravity operated skylight. The solar toilet will function as a compost toilet during cloudy weather. For extremely cloudy weather the tumbler model is the only choice. At this point the scraper model is great for areas with 200 or more sun days per uear and the tumbler model will extend the use o areas with only 150 sun days per year. You need one for every 2 people in areas down around 200 sun days per year. Optional reflectors will enhance the performance of either model.

Both Solar Toilet units are available through Earthship Biotecture. The DC fans and construction drawings for the scraper model are also available.

solar toiletProduct List:

DC Fan
Solar Toilet Scraper Model
Solar Toilet Tumbler Model
Construction Drawings and Procedures for Scraper Model
SunMar Excel-NE
SunMar Centrex-NE
Sealand 910 Traveler

A Solution
We found ourselves looking for a dry toilet situation that required less effort and that produced a more acceptable “product” to put back on the land. We were also looking for a fool proof process that was not as tedious as taking care of a rabbit. The bottom line is, at best, the SunMar units require too much care for the average busy twentieth century human to want to deal with. The ultimate unit must do everything itself and leave you with a truly transformed product that no building inspector or environmental authority would have a problem with. The reason compost toilets are not acceptable in many areas is that the final product is often too rich and the widespread production of this product could create an undesirable situation. The final product must be something so benign that you could hold it in your hand and would want to put it in your yard or hallway planters. Many people have seen and/or heard about solar ovens. They are a well insulated black box with tempered glass on the front. They really work. You can boil water and cook turkeys in them.

We tried using a large solar oven with a toilet seat built into the top side. The results blew us away. Have you ever left a casserole in the oven on “warm” over night. What you end up with is ash – crackling ash.

The Solar Toilet Concept

The concept of this toilet is a cross between a solar oven and a compost toilet. It uses no water and no electricity. It uses sun. The excrement goes into a basket that holds the solids and lets the liquids drip through. This basket is placed against the solar front face of the Earthship (or south side of any house) in a black insulated space similar to a solar oven. Extreme temperatures (200 to 400 degrees) and direct sun simply fry the solids and evaporate the liquids. The fried solids turn to black ash and fall through the basket into a pull-out tray where it almost turns to dust. This tray is emptied once a month. This black ash is not going to scare anyone. It can even be put on an interior planter. We have put this black ash/powder into water and had the water tested. The test showed no bacteria in the water.

The volume of fried ash that is emptied out once a month is remarkably small. The ashes from two people using a solar toilet for one month will half fill a quart container.

Regular toilet paper can be used. It simply dries up and turns to flakes, then dust. You can drop a match in and burn it for instant disappearance in the scraper model. This unit can be totally built in with the architecture with no plumbing. It essentially costs no more then the Excel-NE. It vents like a wood stove and requires a scraper to be moved back and forth once a day. The following picture illustrates the final product – fried ash.

Our first working prototype, (the scraper model) worked great but had one drawback – you could see the fecal matter through the glass. Obviously, many people couldn’t handle this. We have since evolved a tumbler model which is more expensive, but contains the contents in a steel tumbler drum. In this circumstance, you can see nothing through the glass nor through the seat. Yes, tampons can be put in. On this tumbler model we have moved the door opening that allows the tray to be removed to the inside. This pull out plug is easier to operate (inside the building) and cheaper to build than the “glass door” on the front.

Both units require a D.C. fan similar to the SunMar units. An important factor here is that the electric fan is only turned on during use and kept off the rest of the time in order to maintain high temperatures in the “oven”. It is not on all the time like the fans in the Sun Mar units. We have a set of construction drawings available for the scraper model. The tumbler model is more involved and we simply manufacture it. Both units are designed to fit into the front face of an EARTHSHIP.

The tumbler model works much the same as the SunMar composter when the sun is not out. Then when the sun comes out it fries the back tumbled compost. Thus the tumbler model extends the use of the concept to cloudier areas and minimizes the visual contact with the compost.