Construction of a Composting Toilet
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| Written by Nick Moser |
| Friday, February 1st 2008 |
| Construction of a Composting Toilet |
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 This article discusses the recent composting toilet I built, along with the economic, design and aesthetic reasons composting toilets are ideal, especially in a rural setting. In a rural setting there is no reason to have anything other than a composting toilet. A composting toilet is a simple, elegant and economical solution to disposing of waste where there are no public utilities. In cities and densely populated suburban areas, pu blic health and space issues make the system more difficult to implement. However, in a rural setting the composting toilet is the ideal solution to using resources efficiently. Previous articles discussed the benefits of composting toilets as well as the societal burden that comes with waste disposal. In this article, I will discuss the specific economic advantages of composting toilets, how to build one, and ideas about making their use more widespread. Why Composting Toilet? The alternative to a composting toilet in an area without sewers is a septic system. In contrast to the composting toilet, the septic system is complicated, homogeneous, and expensive. The necessities of a septic system are as follows:
 And so now for $2000, the rural house can begin the exciting journey of flushing more money down the drain, if they are lucky enough to have a public water supply. If they are completely off the water grid, then a flush toilet wastes valuable harvested rain water, or pristine drinking water from a well. The water is instead mixed with urine and feces and sent to sit in the tank for awhile before slowly draining into the surrounding area. The soil then purifies the effluent so it does not contaminate the ground water. Instead of going to the expense of putting in a septic system, the composting toilet is the sensible option for disposing of human waste on a farm, ranch, or cabin. The materials I used to build a composting toilet do not even warrant bullet points: a hammer, nails, saw, lumber, bucket, funnel, a hose and plastic sheet. These materials all combined will not run over $500 even if the common tools are bought for the project. So which is the sensible option: an expensive, complicated system that creates harmful byproducts and wastes water, or a cheap, easy to build system that wastes no water and provides valuable resources? Well then, how? The basics of a composting toilet are much simpler than most people think. The most essential element to the composting toilet is the removal of water from the waste. Water in the feces is what keeps bacteria alive that create smell and hazardous waste. By removing water, the smell is reduced and valuable humanure results. This is done in two ways, the first being the addition of dry material after each use, similar to any good compost system. The dry material can be paper, bark, sawdust, or even dirt. The mixture I use is 45% sawdust to quickly absorb moisture, 45% ash from the fire pit to eliminate odor and kill bacteria, and 10% ceder mulch, which smells nice. The second way that water content in the toilet is removed is by separating the urine from the composting material. This is easily done by positioning a funnel in the front portion under the seat of the toilet to catch most of the urine. The urine should run from the funnel through a portion of hose and into a storage container, like a plastic jug. The jug should be checked regularly and sprayed onto non-food crops (more for the idea than necessity) as an excellent sterile pesticide. With most of the water removed, the feces will reduce 75% of its size, thus the container of humanure will not need emptying all that often, and if kept dry will not smell. So the basics are merely a bucket and funnel, but what about a bit of comfort? The project I recently undertook was to make a functional outhouse. An outhouse provides the comforts of shelter from the elements, privacy, and keeps curious animals away from your 'valuable resources.'  First, select the site. This should be near to living areas for ease of access and avoid placement uphill from food crops just for the off-chance of contamination. Next, dig the holes for placing the main support posts. This is when the dimensions of the outhouse are set in, well, soil. Mine was a five foot by seven foot rectangle, but this is where to decide how much room you need to walk in and sit. Keep in mind that holes need to be dug an average of 1/3 the full length of the pole. Thus a six foot pole needs a two foot hole. However, when that post is placed in the hole, two feet go into the ground leaving a very short four-foot outhouse. I used eight foot posts and dug the holes approximately 2.5 feet deep. Make the holes as narrow as possible, but wide enough for the posts to easily go in. I left around 3 inches on each side.  Then place the posts in the holes. For a sloped roof I cut the tops at an angle before placing them in the ground. Since these are the main structural support of the outhouse, I suggest 4x4 posts at least, which is what I used and are quite sturdy. Also, using cedar will increase the lifespan of the outhouse as it does not rot in the ground as quickly. Once the posts are placed, I used a style of rammed earth foundation, which is a mix of pea gravel, sand and clay. Sprinkle some of the mix at the bottom of the hole and pack it down with the post, making the bottom as level as possible. Then pour a small amount of the mix evenly around the edges of the post, packing it down with a rod that fits between the side of the post and the hole. I used two broom handles, for fast-paced packing with both hands. Then pour a bit more mixture and repeat the process until there is a small mound above the ground around the pole. Next comes building the throne itself. Nail two-by-fours a bit above the ground to use as a support for the floor and seat box. I left the back open so that the compartment holding the composting bucket would be entirely separate from the indoor space. Note the blocks bracing the  two-by-fours. I used three squares of chip-board to make the floor where you walk in, the face of the seat box, and the top of the seat box itself. I built this for use in the work area of my land and was not overly concerned with the look of bare chip-board. Nice plywood or tongue-in-groove roofing lumber are also excellent options. I would, however, highly suggest some sort of floor as you walk in. If not using lumber, build the floor up and place stones or poured earth. Leaving this part open and merely building a seat box is just asking for a muddy welcome to your outhouse. In the top of the seat box, cut a hole that feels comfortable for sitting on. I happened to have a chainsaw for cutting the hole. If lacking any sort of saw besides a handsaw, a series of nail holes around the hole works well. In placement, not too far back is key, but this is an excellent area for trusting your personal needs for the decision. I placed an old toilet seat over the hole for added comfort. Underneath the hole, place the funnel in the front portion and a large collection bin (old steel drums work great) underneath the entire hole. Connect a hose to the funnel and attach to separate collection container.  The next step is a roof. Nail more two-by-fours to the posts at the angle of the roof grade, extending at least six inches in front and back for protection from rain. Put horizontal supports (across the front door, not down the side) across the front and back, again extending six inches beyond the posts. Put a few more horizontal supports, depending on how much weight the roof is going to hold. The simplest option for covering this now is merely to place another piece of chip-board or plywood and waterproof it. However, I very much enjoy plants growing on the roof and I was not going to pass up the opportunity to put them here. Thus I strengthed my roof with additional supports. Whatever you use, the final step is to waterproof it. This can be done using plastic sheeting or metal roofing material easily found at hardware stores. If using premade roofing material (the ones with grooves), make sure the grooves flow down towards the back of the outhouse. If using plastic sheeting, make sure to tack the edges very well to avoid water seeping in. Now that there is a seat and a roof, the last thing before becoming operational is a wall. Again, many materials can be used for the walls. I recommend cob, merely because it looks great in nature and is very inexpensive. However, wood, stone or metal are all options for building the wall. Since the walls are more for privacy than structure, they can be works of art and individuality that will make this outhouse truly your own. I am currently putting the finishing touches on the living roof, and will add walls of woven sticks in the coming weeks. But already covered and waterproofed, my composting toilet is fully functional!  What more do you need? Well, nothing really. But just as the seat box, walls and a roof are "added" comforts that aren't necessary for a functioning composting toilet, there are many things that just make life more pleasant. The living roof on top of my outhouse is a good example. Not only do I enjoy the idea of living roofs, this one is planted with mint which will cascade down the outside walls making it truly beautiful and provide a nice treat to smell and eat. The main thing that would make composting toilets absolutely the only option for rural use is using them inside. When it is cold, or dark out, if we are warm and inside our homes, we don't want to venture out to use the bathroom. The most common problem with putting composting toilets inside is simply the smell. There are three things that eliminate this problem. The first is to make a chimney going from the box holding the composting bin outside the house. Thus when the toilet seat is closed, the smell escapes out of the house. The next is completely closing off the collection area from the inside of the house, making the access on the outside of the house. This helps the chimney suck the air from only the collection area. The last, and absolutely most important issue, is  the use, every time, of organic and inorganic material to soak up the moisture and smell. If built correctly, a composting toilet will not smell. For more widespread use, the indoor option is most essential. However, new technologies separate chambers so that the user is not adding the composting material. If made more accessible, this could even make composting toilets available in more densely populated areas. The intelligent management of our wastes will certainly include the composting toilet in order to reduce toxic runoff in rivers and use resources to their utmost potential. This is because the composting toilet is simple in its construction, elegant in its design, and economical in its sustainable use of resources. Last update: May 21, 2009
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