What type of composting toilet you choose will depend on your tiny house design, location, and portability. Many tiny houses aren’t permanently installed and connected to services so alternatives to traditional fixtures are necessary.
Composting toilets are a great choice for any tiny house – even those with full plumbing – because they are inexpensive, efficient, and sustainable. If your impression of a composting toilet is that it will be messy I’m happy to tell you that you are wrong. Although they work differently than water toilets they are not intrusive.
How composting toilets work
Instead of using water to wash away waste a composting toilet works by evaporation and decomposition. Excess fluid evaporates and is vented outside. The remaining waste decomposes using natural bacteria in a controlled environment. Organic material such as coconut husks, sawdust, or peat moss is added to maintain the right balance of moisture, heat, and airflow.
The waste material mixed with added organic material naturally breaks down into a rich soil that can be used to add nutrients to the soil around trees and landscaping. The entire operation of a composting toilet is done without adding water, which greatly reduces the amount of clean water contaminated by one household.
Choosing a composting toilet
There are different models of composting toilets and some factors to consider when choosing one for your tiny house.
The basic components of a composting toilet are the seat and the composting chamber. A good composting toilet also has a mechanism for diverting at least some of the liquid to keep the volume in the composting chamber low. Without this feature your toilet might compost slower and some odors may escape. The problem with composting toilets is that all of these components add up to a much larger unit than a traditional water toilet.
This can be a problem in a tiny house where the entire bathroom is probably just a few square feet. To keep the bathroom small look for a composting toilet with separate seat and container components. These types of composting toilets are designed to have the collection container installed below the floor or outside the bathroom where it won’t get in your way. You will need to make sure you can access the container because it will need to be emptied from time to time.
These compact composting toilets are worth considering for your tiny house:
1. Nature’s Head Self Contained Composting Toilet
22 x 20.5 x 21.7 inches
Read the reviews
2. Sun-Mar Excel Self-Contained Composting Toilet, Model# Excel
26.5″ X 22.5″ X 46″
Read the reviews
Organic materials for your composting toilet
All composting toilets use added organic material to enable the decomposition process by keeping the moisture, air and heat levels consistent. Different toilet manufacturers recommend different types of organic materials and it will probably be a bit of trial and error to find the right mix for your particular toilet type depending on its frequency of use.
You will also need a container and scoop to keep the organic material in near the toilet so don’t forget to include space for that in your design.
Wood shavings or sawdust
A local lumberyard or mill might be able to give you their waste sawdust for use in your toilet. For this type of organic material it will work better if the particle size is smaller. Different types of wood will also add a different fresh tree scent when used.
If you live somewhere near coconut palms you probably can find a local source of castoff coir from coconut husks. Like wood shavings you don’t want to use pieces that are too big to easily breakdown so you may need to shred it a bit.
Peat moss can make a good covering material for your composting toilet as long as it isn’t too moist or too dense. If it is lumpy break it up before use.
Some people use shredded newspaper in their composting toilet. It doesn’t have the same fresh scent as wood shavings and can clump up if the pieces are too large, however if sufficiently shredded it will do the job.
Hay or straw
If you live near farms and have a source of hay or straw you can use this as an organic additive for your composting toilet. Hay is a bit trickier to store in your bathroom.
Cleaning your composting toilet
Because you aren’t flushing the bowl with water each time you use it you will need a different way to keep the toilet clean. A well designed toilet will have a straight channel where the waste generally doesn’t touch the walls. Keep a spray bottle with some water or vinegar solution handy just in case.
You will also want a small brush to wipe any stray sawdust off the seat!