Building a compost Toilet
Allow me to start with an anecdotal account that contextualises the need for this guide and then I move on to sharing some details about how we build our first compost toilet.
My first experience with compost toilets (or rather “dry toilets”) dates to my school years, and it is one that I remember fondly—despite being questionable in light of today’s sanitary standards.
My parents had accepted an invitation to spend a few days at an old (more than a hundred years, it was said) countryside house near a remote village in Colombia. The house was located high on a mountain and, to get there, we had to cross a river on what I also remember being my first experience on a sizeable bridge made out of timber. Once on site, everything about the place was lovely. The architecture of the house was ancient, and it had an unpolished, rustic feel to it; not to mention its location surrounded by dense tropical vegetation.
Around the house grounds one would find all sorts of intriguing objects that would have me wondering about their intended purposes. Some of these included a child-size rock place on top of a wooden scaffolding (which I later learned it filtered water), a huge stoned hole in the ground resembling an empty swimming pool with a small channel leading to one of its edges (which I then learned it was a shower system using nearby streams), and of course, the “latrine”. I can recall it, as if it was yesterday. I only discover it at the time when I actually needed a WC, and when I asked where the toilet was, to my surprised I was pointed in a general direction outside the house, towards the edge of the mountain. When I finally spotted a shed through some of the vegetation, I was eager to finally be able to release myself.
I opened the door and stood there, staring. My brain—once more—was having difficulty in reconciling what I was seeing and what I expected to find. Inside there was only an elongated slate rock, it could’ve been a stone bench for all I knew. As I stepped forward to inspect the “bench” I immediately went into a catatonic state, afraid to make a move. There was a circular hole in the centre, and one could see a freefall drop in the air all the way down to what I guessed to be the vegetation bordering the river at the foot of the mountain. When I regained the ability to move and think clearly, I then became aware of and paranoic about whether it was safe to stand on the shed’s floor made from wooden planks; never mind sitting on the bottomless latrine! I can’t recall exactly how long I hesitated. In the end, physiology had its way and I had to overcome my inclination to run away. I will admit, however, that once I got “down to business”, I found the whole enterprise to be incredibly entertaining. I mean, which kid doesn’t enjoy throwing stones down a cliff and seeing them fly?
It wouldn’t be until I started visiting some hippie-ish camps and eco-farms that I would come across “dry toilets” again. In fact, in many of the places that my partner and I have visited in the capacity of volunteers we’ve seen compost toilets. As somebody who appreciates self-made structures (and is constantly thinking about the next DIY project) I always pay close attention to how other people set up their systems. The “composting” part always remained a mystery to me though. So, at times I would ask some questions and sometimes I would get half-informative answers about why they’re supposed to work. Yet, curiosity would always creep up and I would have nagging questions on aspects about which I’ve been given unconvincing answers. As time went on, in spite of my lack of understanding, after seeing commonalities in the composting systems that some of these places employed, I figured, there must be something right about it. Little did I know that a lot of places that claim to compost organic matter didn’t really know what they were doing… they might’ve as well throwing shite down a cliff! Of course, I was just as ignorant, and believe the lovely people I’ve met in these wonderful places were doing so inadvertently. If it wasn’t for my tendency to rely on my own research, I probably would’ve ended up replicating such flawed practices, however well-intentioned they are. Therefore, in what follows, we share some of what I’ve learned about compost toilets, and what to bear in mind when building one.
Compared to modern toilets, there are many advantages to composting one’s body waste, particularly for those seeking environmentally friendly and sustainable options. Some of these include:
Water conservation: Unlike traditional flush toilets, compost toilets require minimal or no water for operation.
Nutrient recycling: The waste produced by compost toilets can be turned into nutrient-rich compost, which can be used to fertilize gardens and other plants. This helps to reduce the need for synthetic fertilizers and promotes sustainable agriculture.
Reduced environmental impact: Compost toilets eliminate the need for sewer systems and wastewater treatment plants, which can contribute to pollution and energy consumption.
Suitable for remote locations: They are ideal for areas without access to municipal water or sewer systems, such as rural or off-grid properties.
Cost-effective: In the long run, compost toilets can be more cost-effective than traditional toilets, as they require less maintenance and eliminate the need for water bills; not to mention the costs involve in building one in the first place.
Reduced odours: When properly maintained, compost toilets can produce minimal odours. This is achieved through proper ventilation and the addition of materials (e.g., wood dust/shaving, dry leaves) that help to absorb moisture and control odours.
Neutralising pathogens in human organic material: When done properly, humanure composting by thermophilic processes (thanks to beneficial micro-organisms such as bacteria, fungi, earthworms, and tiny insects) can be one of the best and safest methods for treating human matter so it does not represent any biological hazard.
In addition, separating urine and faeces in compost toilets offers several additional benefits, in particular for indoor and enclosed spaces:
Reduced odours: Urine is often a major contributor to odours in compost toilets. By separating it, you can significantly reduce the overall odour production.
Enhanced nutrient recovery: Urine can be processed separately to produce a highly concentrated liquid fertilizer that is rich in nitrogen, phosphorus, and potassium. This can be used to fertilize plants without the need for additional nutrients.
Reduced pathogens: Some pathogens can survive in faeces, but it is thanks to the high acidity of urine that they are activated. By separating the two, you can reduce the risk of pathogen transmission (but this is not something to worry about if you have a good composting method).
Having said that, we advise against separating urine, both for practical and composting reasons. After all, having to design a urine separator can be tedious and women may feel uncomfortable with the idea of having to clean the separator for a few days every month. More importantly, however, urine is a highly nitrogenous liquid that can accelerate the composting process.
While compost toilets offer numerous advantages, they still require some maintenance and may not be suitable for all situations. So, before embarking in building one, do assess if compost toileting is the right choice for your specific needs. In our case, besides the aforementioned ecological reasons, building a compost toilet represented convenience and ease of use. We’d be the first ones to admit that this is not a revolutionary invention: humans have been laying bodily waste on earth since our existence, but anybody who’s been on a camp site knows how inconvenient it can be having to crouch every time “nature calls”—even for fully able individuals. Not to mention the logistics of ensuring that nobody steps/unearth somebody else’s burial or simply keeping track of depositing spots. Above all, composting not only is advantageous from an agronomist point of view, but “open defecation” can facilitate the proliferation of pathogens and is indeed a vector for disease; so, don’t do that!
A compost toilet could be any structure that temporarily houses digested organic matter and facilitates its management. In other words, any box upon which one can sit and keep our organic matter before being relocated to its permanent composting location will do the job. The essential build of a compost toilet can be done irrespective of the “containing” or “receptable” system (more on this later). Also, if wished, the “separator” feature is something that can be incorporated later on as DIY’ing the separator entails further preparation and additional materials (although nowadays one can find these on the market, the demand isn’t that great to make them affordable to what we consider a reasonable price—in terms of the quality of the material and judged against the time it would take to make one yourself).
In addition to the basic structural characteristics, such as being robust enough to withhold a person’s weight and being comfortable, it was important for us that the toilet was easy to carry for constant relocation in uneven terrain. This meant making it not too heavy, add some way to lift it, and equipping it with a three-point support (viz. three legs as opposed to the conventional four). Additional features included a compartment to store composting “additive matter” (e.g., wood dust/dry grass), easy/wide access to the container/receptacle for the human faeces, as well as a standard rim-seat. Final touches consisted of bottom corner-braces and sealing the wood panels with varnish to prevent humidity damage.
Materials: besides plenty of screws and the obvious already mentioned, we used 18mm MDF panels, and “piano-hinges”. Make sure to check out some of the pictures of our build in the DIY gallery, and you can also get a blue print of the measurements we used here.
