Is a composting toilet the answer for you?
A composting toilet is not so much a portable solution as it is a permanent alternative toilet to a standard water-flush unit.
They are ideal in a number of situations... particularly if your cabin does not have water and/or electricity. It also may be ideal if you simply want a more environmentally friendly solution. But there is a lot to consider... it's not a simple topic!
The premise is that human waste can be converted into useful compost - something that some of us may find somewhat distasteful! However, given the huge waste of water with conventional flush toilets - the average household flushes toilets 5,000 times a year - there is a lot to be said for an efficient composting toilet.
Waterless and minimal water units are available
A properly functioning composting toilet should break down waste material to 10 to 30 percent of its original volume. What's left is a beneficial humus that provides valuable soil nutrients.
One example is the SunMar Excel Self-Contained Composting Toilet, a waterless electric toilet that runs on standard household current. This unit is ideal for installations where water supply is non-existent or shut off part of the year. This is a high capacity unit that can be used just about anywhere.
The SunMar Excel NonElectric SelfContained Composting Toilet is a non-electric composting toilet that is ideal for "off-grid" use as it uses no water or electricity.
How they work
If you're familiar with a standard yard composter where vegetable matter is broken down to garden humus, you are well on your way to understanding a composting toilet! It's basically the same process.
Human excrement comes into contact with a wide range of microbial agents including bacteria, actinomycetes, fungi, algae, lichens, viruses and other organisms. These agents work in a controlled aerobic setting (i.e., they require oxygen) to decompose moist solid waste into a soil conditioning substance known as humus.
The composting process does this in such a way that it transforms potentially harmful residuals in the waste into a stable, oxidized form that, when applied to soil, adds valuable nutrients.
Odors and handling
Of concern to many people are issues around odor and handling the waste.
We'll address those concerns as best we can.
First, the issue of smell. Obviously when dealing with human excrement, there are thoughts of how the odors are contained.
Generally, if you're using a composting toilet and are having odor problems it's more than likely related to incomplete decomposition. As mentioned later on this page, issues such as and incorrect moisture level, temperature too warm or too cool, insufficient microbes, etc., can result in some odors. These issues can be addressed through carefully following the manufacturer's directions. That will usually take care of any odor issues.
Handling of waste is another thought a lot of people have and wonder if it's something they will want to do, and will it be an unpleasant undertaking.
As long as your composting toilet is working efficiently and giving you complete compost or humus, you will not be handling waste, but rather material that is broken down to its components as a fertilizing agent that has no resemblance to its original state.
A few key points:
- the material must be moist but not wet or saturated in order to allow the aerobic process to take place
- applying the waste directly to the soil without composting can actually tie up valuable nitrogen and make that nutrient unavailable to plants while the material is decomposing
- the organisms involved in the composting process actually converts the material into a stable product that builds soil it is applied to and releases its nutrients in a controlled manner
- the nutrient content of composted human waste, which is highly nitrogenous thanks to urine, is equal to that of many chemical fertilizers
Single or multi-chamber composters
Composting toilets are generally divided into two types:
- Continuous or single chamber (often used for cabins and other small applications)
- Batch or multi-chamber (where material is collected in a central compost locations that might service more than one toilet)
Continuous or single chamber composting
Continuous composting features a single chamber into which excrement is added to the top, and the end-product is removed from the bottom. It is simple in that it takes place in one fixed reactor. It allows urine to constantly moisten the process and allows the center of the mass to heat up through uninterrupted microbial activity.
Batch or multi-chamber composting
By not continually adding fresh excrement and urine, the material composts more thoroughly, uninterrupted by the added nutrients, pathogens, salts, and ammonia in fresh excrement. Also, by dividing the material, it can have more surface area, and thus better aeration. Batch composting also offers an opportunity for unlimited capacity, as one simply adds compost reactors to the process to add capacity.
Batch systems require monitoring the level of the composter to determine when a chamber has filled and a new one must be moved into place. However, because there is more surface area and the material is divided, there is often less or no mixing and raking of the material.
In continuous composters, urine or flush water can leach fresh excrement into the finished compost removal area. Segregating the material into batches reduces the risk of having living disease organisms in the finished products.
Active or Passive
As the names imply, composting toilet systems can be relatively hands off (passive) or require a certain amount of mechanical intervention.
In passive systems, only time, gravity, ambient temperature, and the shape of the container control the process.
Active systems may feature automatic mixers, pile-leveling devices, tumbling drums, thermostat-controlled heaters, fans, and so forth. Because of the efficiency of active systems (i.e., faster decomposition), the size of the composter can be smaller than in passive systems.
Some factors for successful composting
Get the right ingredients
Before any composting can take place, the right organisms must be present in the organic material. This can be accomplished through the purchase of a commercial compost activator, available through most garden centers.
Or you could simply take a few scoops of sifted compost from a garden compost pile. There should be adequate microbes present in the material to initiate the process in your composting toilet.
One gram of healthy soil may support 500 million bacteria, 20 million actinomycetes, 900,000 fungi, 100,000 yeast, 500,000 algae and 500,000 protozoa!
The Environment
Environmental factors must be right for aerobic decomposition to successfully take place.
- Oxygen
- Moisture
- Temperature
Is there enough oxygen for the processes to take place? Lack of oxygen creates a situation called hypoxia and the aerobes die to be replaced with anaerobes (organisms that can exist only in the absence of molecular oxygen). The result is odor caused by the production of hydrogen sulfide, ammonia and amines, and potentially flammable methane gas.
So... proper ventilation is essential for the proper functioning of the composting process.
Just as for Goldilocks, the amount of water needs to be "just right". Too much and the saturated conditions literally drown the microbes. Ideally the moisture level should be between 45 and 70 percent. Below 45 percent is simply too dry.
The ideal temperature to promote biological decomposition is 78° (25°C) to 113°F (45°C). The temperature at which almost no microbial respiration occurs (biological zero) is 41°F (5°C)
Summary
This is meant only as a brief introduction and overview to the topic of the composting toilet. Should you decide to pursue this solution to collecting and disposing of human waste you will undoubtedly delve much deeper into the topic. And specifically into the unique characteristics and requirements of the unit or system that you decide on.We have friends who had a composting toilet at their cabin (this was more than 15 years ago). They had a single chamber passive unit. I recall that the main complaint was the odor. After doing the research for this article I now realize that their problem may not have been the toilet, but instead could have been caused by other factors. Also, I'm sure the technology has improved considerably since that time.
Do you have (or have you had) a composting toilet? Share your experiences for benefit of others.
