If your mobile home or tiny house lacks the plumbing to support a traditional flushing commode, a composting toilet could be the solution. This unusual kind of toilet uses aerobic bacteria to break down human waste and stows it in a neat, easy-to-remove package. The toilet separates liquids from solids, breaking down solid waste with organic materials and bacteria to become human manure (a.k.a. humanure). While you can dispose of this waste in a trash bag if your local regulations allow, you can also use it in your garden—yes, even on edibles!—if you so choose.
A top-quality composting toilet will prevent odors and leaks, perhaps most important for a smaller living space, but there are numerous other factors to consider when making your choice. This guide will help you make that decision and describe why the following products are among the best composting toilets available.
- BEST OVERALL: Separett Villa 9215 AC/DC Composting Toilet
- RUNNER-UP: Sun-Mar Excel Electric Waterless Composting Toilet
- BEST BANG FOR THE BUCK: Nature’s Head Self Contained Composting Toilet
- BEST PORTABLE: SUN-MAR GTG COMPOSTING TOILET
- HONORABLE MENTION: Nature’s Head Dry Composting Toilet with Crank Handle
Types of Composting Toilets
Before purchasing a composting toilet, be sure that it will work in your location. There are two types—self-contained and split/central systems—and while they both break down waste, they work a bit differently and have different requirements.
A self-contained system consists of a small toilet with a detachable tank and a liquid drain for removing waste. Some self-contained systems are portable, which works for camping trips or boat rides, and can be set up in a space where plumbing won’t reach, like a workshop or garage.
The entire composting process occurs within the toilet, hence the name. When full, remove the tank and empty the manure. These systems sometimes have freshwater tanks or supply lines as well, to flush waste into the chamber below.
Split System or Central System
Composting toilets that work with split or central systems are similar to a traditional toilet. They connect to a system of pipes that take the waste to a central bio-drum, hopper, or tank, which is where composting takes place. The hopper churns the waste, allowing it to break down while also venting the odorless gases. When the tank fills, empty it just like a self-contained toilet.
Split systems are much more expensive than self-contained composters, as they require a hopper, usually installed below the toilet. The hoppers are a benefit because they significantly increase the amount of compost they can hold. They can be an attractive solution for permanent off-grid or eco-conscious homes, but the setup makes these composting toilets a poor choice for portability.
What to Consider When Choosing the Best Composting Toilet
Keep the following considerations in mind to make the best choice of composting toilet for your needs.
Composting toilets take up a bit more floor space than a traditional toilet, and they don’t have an additional holding tank to contend with. For a tiny home or boat, look for a compact model with a smaller waste tank.
If space for a split-system is available, it might be worth the investment to get the increased holding capacity. Areas like garages and cabins sometimes have flexibility for adding a hopper. In warmer climates, installing the tank outside is an option.
Portable vs. Composting
A portable toilet and a composting one may seem similar, but there are some very significant differences. Composting toilets use bacteria to break down human waste. They separate liquids from solids, allowing the bacteria to feed upon the organic compounds in each. After the composting process, the humanure can fortify a lawn or garden. The byproduct of the composting process fertilizes soil and brings nutrients to plants.
A portable toilet does nothing of the sort. With portable toilets, everything goes into one waste tank where liquids from solids are not separated. Even after pouring enzymes and deodorizer down into the tank to break solids down and offset odor, the end product still needs to find its way into a sewer or septic system. So while a portable toilet can be handy for camping and boating trips, they may not be the best choice for permanent residences like mobile homes and tiny abodes.
When searching for the best composting toilet, how many people will be using it should determine how big of a tank is required. Manufacturers often break this down by family size and appropriate use.
For instance, a split system with a high-capacity tank might handle waste from three adults or a family of five, while a self-contained composting toilet with a five-gallon tank would be more than enough for one adult. The idea here is that by sizing the tank correctly, waste will have enough time to break down into manure before the tank fills.
Some composting toilets use electricity to power a fan that draws air into the tank and across the waste. The air is rich in oxygen to feed the aerobic bacteria breaking down the waste. This also exchanges the carbon dioxide created by the bacteria, venting it into the air. Many work with a home’s 110V system, while some work with both 110V AC and 12V DC from a car or RV battery.
A composting toilet may also need a water line. While this seems counterintuitive, the composting toilets that use water consume very little with each flush—far less than a standard residential toilet. Waterless and non-electric models are available too, so consider the utility setup and household budget when choosing a toilet that will work best.
The gases created by a composting toilet’s bacteria need to be vented. Otherwise, odors could build up, or the bacteria’s performance could suffer from a lack of fresh oxygen. The fan some models use to draw air into the tank also forces the gases out through the vent, banishing unpleasant smells. Adding organic materials, like sawdust, on top of the waste after each use can block the odor while still allowing the bacteria to break down the solids.
Our Top Picks
Now that you know a bit more about the best composting toilets, here are some of the best available products. Whatever your needs, you may be able to find the best composting toilet here.
For an all-around high-quality composting toilet, check out the Separett Villa 9215. This waterless self-contained composting toilet has an electric fan to exchange gases, operating on both 110V in a house or on a 12V system in a boat or motorhome. It’s lightweight at only 34 pounds, making it easy to install.
The kit provides the toilet, adapters for both 110V and 12V power, and all the parts for direct venting and for tying the liquid drain into a gray water system. The tank is large enough for around three weeks of use by an average-size family.
The Sun-Mar Excel Electric Waterless Composting Toilet is worth looking into when shopping for an eco-friendly model. This composting toilet uses an electric fan to dry liquids, but it also draws air into the tank and pushes waste gases out of the vent to purge odors. The self-contained tank is large enough for three adults or a family of five.
Even with the Sun-Mar’s large capacity, it weighs just 60 pounds, and installing should be fairly easy. It may, however, require an additional electric kit to wire it for 12V power in a boat or camper.
When it comes to a durable, easy-to-use composting toilet, it’s tough to beat this Nature’s Head model. It diverts urine into an easily removed tank and features a side-mounted “spider” handle for churning the solid waste inside the tank. The waste tank is large enough for two adults to use full-time, which will require emptying every four to six weeks.
This waterless toilet uses an electric fan to draw fresh air in and push odors out, helping to keep smells at bay. While the fan uses 12V power, it can convert to 110V with a kit purchased directly from Nature’s Head.
The Sun-Mar GTG Composting Toilet is worth a look when searching for a compact, portable design that also composts. Unlike other travel models that still need emptying into a sewer, the self-contained GTG produces the same type of compost as other, much larger toilets.
The GTG is a waterless toilet with a 12V-powered fan. It separates liquids from solids, dividing them into two easy-to-remove containers. It weighs just under 30 pounds, a plus for portability, and measures 24 inches deep by 15.75 inches wide and 19.8 inches tall, so it will fit in most bathrooms of tiny homes, RVs, and campers without issue.
Whether it’s for a cabin, boat, or RV, the Nature’s Head Dry Composting Toilet with Crank Handle is a reliable and easy composting toilet option. This self-contained toilet has a rugged, molded plastic design, tough enough for boats and RVs, as well as stainless steel hardware that won’t rust. It separates liquids and solids, with a removable liquid jug. It has a 12V fan and comes with a 5-foot vent hose for removing gases.
The Nature’s Head has a crank handle instead of the typical spider handle. While this does require a little bit more clearance from the wall, the handle is swappable between sides and provides plenty of leverage for churning solids.
FAQs About Composting Toilets
Still not feeling flush with knowledge about these toilets? Here are the answers to some important frequently asked questions. If you need more info, contact your toilet’s manufacturer.
Q. How do composting toilets work?
Composting toilets hold waste in a tank and allow aerobic bacteria to break it down to a material similar to rich, moist soil.
Q. How do you install a composting toilet?
Installing a self-contained, non-electric waterless unit is straightforward. The only concern is venting it outside. The directions that come with the toilet will have suggestions for vent-pipe sizes and heights.
Q. Do you put toilet paper in a composting toilet?
Moderate amounts of toilet paper should be fine. Single-ply is probably best, but most composting toilets won’t have an issue since toilet paper is biodegradable.
Q. Can you poop in a composting toilet?
Yes. The manure you end up with after the composting process is poop—just broken-down poop.
Q. How long does a composting toilet take to work?
This depends on how often you’re supplying the toilet with fresh waste. The bacteria in your composting toilet will begin breaking down waste immediately, and it should take a few weeks to fill with humanure.
Q. Where should I empty a composting toilet?
If you don’t want to use your compost for your lawn and garden, check with your local code enforcement about disposal. Some jurisdictions allow you to bag it up and throw it in your garbage.