Fifteen years ago, some friends installed a composting toilet in their home. I admit that I found the idea gross at first. However, I soon saw that using a composting toilet was easy, didn’t smell, and was a smart move towards self-sufficiency and sustainability.
Back then, my friends were mostly considered wackos for their decision. In the past few years, though, there has been a huge push toward composting toilets. Some people want one for off-grid living. Others are interested in them as an emergency toilet for disaster preparedness.
You no longer have to make a DIY composting toilet as my friends did. Plenty of composting toilet models are designed to resemble “normal” toilets and are virtually foolproof to use. Some of these have cool features.
So, if you want to install a composting toilet in your home, you are in luck. There still aren’t too many options for small, portable composting toilets available, but the ones that do exist are great.
Here are the top picks for best composting toilets and how they compare.
Best Composting Toilet Reviews
Right now, there are only two composting toilets that I’d recommend: Nature’s Head and Separett Villa. These are two-chamber urine-diverting composting toilets. They require no water and can be installed in a home, cabin, RV, or outhouse. They have vents with fans for keeping the compost dry, aerated, and odor-free.
The only difference is that you must rotate the chamber on the Nature’s Head model (with an external crank). The Separett turns the chamber automatically but requires electricity to do so.
Use the Nature’s Head composting toilet if you have no off-grid power source (solar, generator, etc.). If you have off-grid power, the Separett is the more straightforward solution and only costs slightly more.
1. Nature’s Head Composting Toilet
This composting toilet was initially designed for RVs and boats. Thus, it is very small and compact.
Many people use it in their homes and cabins now, though. You can get about 90 uses of out it before emptying. You’ll want to empty the urine chamber every day.
The unit is entirely self-contained with a two-chamber system. One chamber is for urine, and the other chamber is for solids.
How to Use:
To use the composting toilet, you must first add peat moss (or other dry carbon material) to the solids chamber. Each time someone goes #2, you turn the agitator handle on the side. The handle spins the waste in the chamber so it stays aerated. You don’t have to do anything after urinating.
Installation and Electricity:
You will need to connect to an outside vent. Putting this in an outhouse means hooking up the vent pipe to a hole going to the outside. Indoors can be a bit more complicated – especially if you want to install the toilet someplace without plumbing venting. However, it could also just mean cutting a small hole in the wall for the vent pipe to go out of.
You’ll also need to hook up the toilet to an electric supply. The electricity will power the vent fan. If the electricity goes down, the composting toilet will still work. However, some smells might occur. Generally, composting toilets (even without vents) don’t smell. But, to play it safe, you might want to empty it more often if the power goes down.
There is only one model of composting toilet by Nature’s Head. However, you can get it with a “standard handle” or a “spider handle.” The difference is that the spider handle takes up less room to the side, so is great if you are putting the toilet in a very tight spot.
- Two-chamber system
- 12v plug for running vent fan
- 72-watt fan vent
- Uses 1.7amps in 24 hours (comes out to about 4 cents per month)
- Height: 21.5″
- Width: 19″
- Empty weight: 28lbs
- 5-year warranty
- Made in USA
Get this composting toilet if: You want a very affordable, simple composting toilet that does exactly what it’s supposed to.
Buy Here (with Spider Handle)
Buy Here (with Standard Handle)
Note: Order the 12v transformer if you want to power it with 110v power.
Separett 9215 Composting Toilet
Separett is a brand originally from Europe but is now available in the USA. Their toilets are made to resemble regular flush toilets as closely as possible so guests won’t be confused or put off by using them.
The Separett Villa is probably the most accessible composting toilet to use. However, it has a significant downside: you can’t rotate the chamber manually. If the power goes out, the chamber won’t be rotated, and composting will slow down. So, this is only the best option if you have a reliable off-grid power source.
The difference between this composting toilet and the one by Nature’s Head is that they have an electric rotator: you won’t have to rotate the chamber each time you go #2.
To use, start with some peat moss in the chamber. You don’t have to do anything else but occasionally empty the waste chamber. If the urine is set up to go in your normal plumbing drain, you never even have to empty a urine chamber.
Installation and Power:
To install the composting toilet, you’ll need a power source for running the rotational chamber and vent fan. It works on AC or DC power, so it is great if you are alternating between normal and off-grid power.
The vent can be connected to a direct vent or US-pipe sized vents. All the direct venting equipment is included with the composting toilet. The fan will work with venting of up to 20 feet.
The liquids can be set up to drain into a plumbing system. Or you can have the liquids drain into a container (which will need to be manually emptied) or to an external filtration system, such as a sand bed outside the bathroom.
- Two-chamber system
- AC or DC power for rotating chamber and running vent fan
- 5 watts
- Uses 5amps in 24 hours
- Vent matches US pipe sizing
- Height: 21″
- Width: 18″
- Length: 26″
- Empty weight: 33lbs
- 5-year warranty
Get this composting toilet if: You don’t want to bother rotating the chamber and are willing to pay more.
Sun-Mar Composting Toilets (NOT Currently Recommended)
Editors note: This toilet is not currently available.
The Sun-Mar brand is one of the most popular composting toilets. I do NOT recommend them.
However, I decided to talk about them because you’ll find Sun-Mar listed in virtually every review of the best compost toilets. Obviously, the reviewers haven’t tried them or talked to people who’ve used them.
Sun-Mar toilets only have one chamber. That means the urine doesn’t get diverted. It goes right into the chamber with the solid wastes. The urine is supposed to collect at the bottom.
In the Sun-Mar electric models, an internal heating device evaporates the urine, maintaining the correct moisture. In non-electric models, there is a drain pipe in case the liquid amounts get too high.
While this removes the need to empty a urine chamber, it also makes composting less efficient. The compost chamber is wet, so more anaerobic bacteria will grow and smell nasty. Plus, some crystals will form at the bottom of the chamber. These are impossible to remove without power-blasting them with a hose – and that WILL stink!
When would I recommend this unit? If you are only looking for a toilet that can be used in emergencies, then the Sun-Mar Non-Electric Excel would be okay. It beats using a twin-bucket toilet.
However, it’s VERY pricey for something that will only be used during emergencies.
Choosing a Compost Toilet
Parts of a Composting Toilet
Most compost toilets are designed to resemble flush toilets as closely as possible. There will be a seat, bowl, and flush lever. However, no water is released when flushing. Most manufacturers recommend spraying the bowl with vinegar after each use to keep it fresh.
The other parts of a compost toilet are very different, though. There’s some variation between types/models of compost toilets, but these are the parts you can expect to find:
1. Urine-Diversion Device
It is essential to separate urine from solid waste. Otherwise, the nitrogen content and moisture will be too high for the waste to compost quickly.
Urine diverters for compost toilets are straightforward devices but work remarkably well—a funnel-like shape channels urine down a tube and into a collection device. When the urine tank is full, it can be dumped outside safely.
2. Waste Chamber
After using the toilet this is where waste drops. Before using a compost toilet, add some compost material to the bottom, such as sawdust or peat moss. Each time you empty the chamber, you’ll have to add some new material.
Depending on the model of composting toilet, there may be multiple chambers. The final chamber is the “finishing” chamber, where composting waste is completed. By the time the waste is removed from the chamber, it is safe to spread in your garden. These multi-chamber composting toilets are huge, though, and usually not portable.
Some very advanced compost toilets have sensors and thermostats inside the chamber. The toilet automatically adjusts the temperature, so conditions are ideal for composting. These composting toilets are expensive and not great for off-grid or emergency planning.
Each time you go #2 in a compost toilet, you should add a bit of peat moss or sawdust. Then, you need to rotate the chamber. To do this, portable compost toilets have a handle on the outside. The handle rotates the chamber to agitate and aerate it.
4. Vent and Fan
Venting the toilet’s chamber allows more air to reach the waste inside, thus helping aerobic bacteria thrive so composting occurs faster. The vent also helps any foul odors escape. Adding a vent fan drastically improves the results, but the fan will require electricity.
Electric or Not?
Almost all portable compost toilets require electricity to work. Electricity will power fans, rotate chambers, and even control temperature.
Having electric parts means that composting happens much faster. However, the obvious caveat is that you’ll need electricity for your compost toilet to work. For example, if a blackout occurs or you must repair your solar panels, your toilet may not work.
Keep this in mind when choosing. It is nice to have all of those electric features, but:
- Make sure it will still work without power or
- You have a reliable form of energy (such as an emergency generator).
As I discussed with the Sun-Mar composting toilets, you typically want a composting toilet that will divert urine. Otherwise, the compost gets too wet, and stinky anaerobic bacteria will form. It will take forever to get clean fertilizer if your compost is too moist. The nitrogen in the urine also doesn’t help with composting.
The only time it’s okay not to divert urine is if the waste goes into a giant external tank or ground pit. The tank or pit can be lined with sand to drain the moisture. However, these pits aren’t allowed everywhere because the waste can contaminate groundwater.
The bottom line? Stick to urine-diverting composting toilets.
In theory, it shouldn’t matter what your composting toilet looks like. However, if you plan on having guests over, it is beneficial if your composting toilet resembles a standard toilet as much as possible. Otherwise, your guests might be confused about how to work it.
*It helps to put a poster in your bathroom telling guests how to use the toilet. Nature’s Head has one that you can download and print here (PDF).