The complete guide to Composting Toilets

New to composting toilets? Our guide will tell you everything you need to know, from our sustainability experts.

Which composting toilet should I buy?

The top two composting toilets on the market today are the Airhead and the Nature's Head. For our money, the Airhead is a superior product. Read our full reviews to see which one will work for you, or check out our Blog series where Nick and Fiona go through the whole process of installing an Airhead in both their RV and their canal boat, and share their experiences of living with it on a day-to-day basis.

ImageProductFeaturesPrice
Best Overall
Airhead Composting Toilet
Airhead Composting Toilet
  • Urine bottle with a capacity-indicator window
  • Ventilated Solids hatch
  • Removable 
  • Seals and lids
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Good Choice
Nature's Head Composting Toilet
Nature's Head Composting Toilet
  • 12-volt shroud fan
  • Spider and shifter handle
  • Power hook-up
  • Urine bottle with a capacity-indicator window

 

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How do composting (waterless) toilets work?

Composting toilets are an amazing way to save money while reducing your impact on the environment. Here, we explore the natural processes at work in a composting toilet, as well as the components which make it all happen with ease and without odor. 

Kinds of composting toilets

Before digging into the detail of how does a composting toilet work, it’s important to understand the differences between the main kinds of composting toilets that are on the market so you can see what is the best composting toilet for your situation

Traditional composting toilets

Dating back from the original outhouses and pit toilets, these come in a variety of shapes, sizes and complexities, but essentially are a big hole that you poop and pee in! 

There are some clear disadvantages when compared to modern composting toilets – the smell, the size of the hole required, and the risk of trouble in flood prone zones.

Active composters

Also known as self-contained composting toilets, active composters contain a larger storage unit than dry flush toilets. Solid waste is directly composted in the storage unit. The owner will need to put some effort into maintaining the right conditions for composition, such as adding a carbon material like coconut coir to encourage aerobic processing, and microbial starter cultures. 

These toilets are bulkier than their dry flush cousins, although they take up roughly the same floor space. 

Vermifilter toilets

A vermifilter toilet uses some flushing water and earthworms to aid with the decomposition of the compost. The solids (poop and toilet paper) are broken down by bacteria and the earthworms to produce a humus with a significantly reduced volume. 

Some users of dry toilets also add earthworms to their mix to help with the decomposition process.

Dry Flush (waterless) Toilets

Otherwise known as ‘slow composting’ or ‘moldering’ toilets, these are the most popular category of composting toilets, and the one that we’ll be focusing on in this article. Here, the initial part of the composting process takes place in the toilet’s in-built chamber. The chamber is then emptied regularly into a larger compost pile away from your residence. The main benefit of this is that the toilet unit can be smaller.

The most popular brands, Natures Head and Air Head, both separate the urine from the solid waste. This helps to prevent the foul odors that occur when urine and poop collide. You’ll actually be surprised how little odor there is. 

Composting toilets don’t stink!

For the rest of this article we’ll be concentrating on the dry flush variety of composting toilets. 

What processes are in action?

When thinking about how does a composting toilet work, its important to understand the processes in action. The main biological process of composition is a fairly simple one, but one that can be improved or hampered by external factors such as temperature, drainage, aeration and ventilation.

Composition

The best carbon to nitrogen ratio for composition is around 30:1. Urine has a high nitrogen content, but as dry toilets divert the urine you don’t need to worry about this. Instead, just add some sphagnum peat moss or coconut fiber to maintain the right consistency and you should be fine. 

Temperature

Heat will speed up the composting process in your dry toilet and kill pathogens that may be in the waste.  Decomposition will naturally generate heat, but if the chamber of your dry toilet is too small to get hot enough for quick decomposition or liquid evaporation, a heater may be used.

Aeration

Aerobic decomposition is faster and less smelly than  anaerobic decay [1]; therefore, we should maintain a certain amount of air throughout the pile to maintain aerobic conditions. Thankfully, this is easily achieved by turning the crank handle on the side of your toilet. 

The end result

Properly composted human waste does not contain any pathogens or viruses, as these are destroyed during the bacterial breakdown. You are then left with a nutrient-rich fertilizer which can be used in the garden, reducing your need for commercial fertilizers and preserving local water quality. Do note that human waste should not be used to fertilize any edible products. 

In 2006 the WHO set up guidelines on how human waste can be reused safely by following a ‘multiple barrier approach’ [2].

The components of a composting (dry) toilet

Another crucial step to understanding how does a composting toilet work, is learning about the components in the toilet itself.

Urine diverter

This is the crucial part of the system that separates the pee from the poop, and avoids all those awful smells. The design is simple but effective; you’ll get used to using it really quickly, but will have to explain how to use it whenever you have guests! 

Composting chamber

All the poop is collected in the composting chamber. The Nature’s Head is rated for 90 uses, or about 3-4 months of regular use per adult. Simply empty it out when the level gets to about the crank handle. Don’t use bleach or other chemicals to clean it as they mess with the decomposition process. 

Crank handle

This sits on the side of the composting chamber. Give it a turn after every use to keep some aeration in the mix.

How to use a composting toilet – the no-nonsense guide

This is a detailed guide on the day-to-day practicalities of how to use a composting toilet. We’ve mostly referred to the Airhead Composting Toilet as this is the model that we recommend, however the basic principles of how to use the Airhead are in line with other composting toilets, so there should be something for everyone.

How to use a composting toilet – day-to-day use

When thinking about how to use a composting toilet, its the small practical details that don’t make it to the instruction manuals which people really care about. Ever wondered what it will be like actually using a composting toilet in your home every day? Let’s dive into the nitty gritty.

Can I pee in it?

Of course you can pee in a composting toilet! One small potential drawback is that guys will need to adjust to sitting down to pee so as to prevent the dreaded splash-back! 

One key aspect of composting toilets like the Nature’s Head, is that liquids and solids get separated. This allows for proper composting action, and also reduces the risk of the nasty smells. 

Avoid the splash-back

Can I use toilet paper?

YES!! Toilet paper can be used with a composting toilet. Toilet paper can be thrown directly into the solid waste chamber of a composting toilet. It will break down in there along with the poop, but avoid using too much. 

Pro Tip: Avoid tearing off long strips of toilet paper as these can get wrapped around the crank.

What toilet paper should I use?

100+ Free Toilet Paper & Toilet Photos - Pixabay

We recommend 1-ply RV paper in a composting toilet because it breaks down faster. There’s no real loss of “wiping ability” when using RV paper, and you can give yourself a pat on the back for helping the environment. After you have washed your hands.

Use a base material

Before it sees any real action, you should add some compost material to the base of the unit. Pre-moistened coconut fiber or sphagnum peat moss are an excellent choice for this, and you should fill it up to the centerline of the agitator crank. You’re aiming for a material that is slightly damp yet a little crumbly.

Composting toilets and menstruation

200+ Free Period & Time Travel Photos - Pixabay

Don’t worry, a composting toilet definitely IS compatible with your period. Exactly how to use a composting toilet at that time of the month will depend on what options you choose for sanitation.

A cup

A cup is a reusable device which you insert to collect the blood. When you visit the bathroom you can simply empty it out. Brownie points for using these as there’s no environmental impact. 

With a compostable toilet you could pour the blood into either the liquid or solid chamber, we suggest using the liquid one as you don’t want to mess with the composting going on next door. You may want to treat the liquid differently if it’s been mixed with blood. 

Reusables

If you make your own or buy reusable pads (well done you!), you’re clearly not going to be throwing them down the toilet in any case. 

Disposables

Firstly, you shouldn’t be throwing these down a normal toilet as they create problems further down the line. While technically, most brands can compose, with a composting toilet such as the Nature’s Head, tampons can get stuck in the mechanism and cause issues for you.

What about diarrhea?

However nasty it might be, diarrhea is still just essentially poop and water. It’s fine to send it down into the solids chamber, however you may need to add a little more compost material like coconut fiber to dry out the mix a bit.

Keeping out insects

Keep the lid down when not in use to avoid any insects getting in, while also allowing for proper ventilation.

If you do encounter flies or gnats, add a few cups of natural Diatomaceous Earth to the compost.

Cleaning a composting toilet

As there’s no wet flush, we suggest keeping a spray bottle with diluted vinegar near to the toilet – this helps remove any stuck-on matter effectively.

Creative Commons Images - Cleaning Images

You should avoid using bleach and other chemicals as they will interfere with the natural decomposition process.

The Nature’s Head does a good job of sealing off the smell of urine. In fact you pretty much only get a whiff of it when you need to change the container. If you do get odors then consider adding a little sugar to the tank. After emptying the urine tank, just give it a quick rinse and you’re good to go.

Dealing with waste

One of the beauties of using a composting toilet is that it brings you closer to your link with nature. Your compost is a living thing, and you’ll come to love it! You can even throw in the odd slice of bread as an offering to the compost gods!

Do I have to empty it?

Oh yes. You have to empty a composting toilet

On the side of the Nature’s Head is a crank – this should be used daily to mix up the solid waste. After mixing you can add a little more coconut fiber. The solid contents should be kept a little moist, and when healthy, should emit a slight soil-like odor (which you should only really smell when changing the containers over).  

A trick which perhaps is for the more adventurous of compost lovers, is to add earth worms to your mix. They love to munch on your dark matter, and you’ll never know they are down there helping your waste to compost faster. If you do use  worms, don’t let them get too warm or too wet. 

Composting solid human waste

When thinking about how to use a composting toilet, one of the most common questions is about dealing with human waste. Solid human waste should be removed when the tank is about ¾ full. It’s rated for about 90 uses, which is around 3-4 months per adult. The best way to remove it is to take out the bowl, put a large bag over the top, then flip the whole thing upside down. You shouldn’t really need to clean out the container between uses, in fact this may be detrimental to the composting process. 

There are two ways to compost solid human waste:

  1. After removing the container, the remains can be added to a larger composting bin. They should be left for at least a year to fully decompose, and should be kept separately from normal compost as it should not be used on edible plants in the future. 
  2. If you’re unable to maintain a full compost bin, you can add the remains to a compostable bin bag and throw it out with the trash. 

How do you dispose of liquid waste?

The vessel holds around 2.2 gallons, which for a single adult is around 3-4 days of use. It can be easily thrown down the shower, however, this is tragic waste of human nutrients, as urine is really good for compost. As long as it is separated from the poop, urine can be safely reused. Simply dilute it in water (1:4), then use on plants or compost it!  

Troubleshooting

The fan isn’t working

Check the usual electric issues, battery voltage, fuses, wire connections etc. This has never happened to us.

My compost isn’t the right texture

Add a little peat moss and give it a good stir if it’s too wet, or simply add a little water if it’s too dry.

Is this the ultimate small footprint toilet?

With a growing global interest in climate change and sustainability, families nationwide are looking for actionable things that they can do in their own households to make a difference. But the big question weighing heavy on everybody’s mind is how.

How can they help? What can they do? With so many different trends and fads competing with each other  right now, it’s almost impossible to figure out what you should actually be doing.

One thing that almost anybody can do to reduce their negative environmental impact and improve sustainability without reducing their quality of life whatsoever is investing in the ultimate small footprint toilet – the composting toilet.

Okay, okay. But what are they?

A lot of people view composting toilets as something new, an evolution on the raging popularity of hipsters and veganism, but that’s not actually the case. Prior to the invention of indoor plumbing, outhouses and pit-style toilets were the norm.

At first, they were quite simplistic creations, like Henry Moule’s 1860 design that “flushed” a small amount of dirt over human waste to be buried in their gardens at a later date. While primitive, they got the jobs done.

Today, however, composting toilets have evolved to take a much different form. They’re typically waterless (though some use low amounts of water or foam to flush), and process generated waste on-site.

Are composting toilets more expensive?

Composting toilets aren’t exactly cheap, costing between $1,500 to $8,000 for a commercial unit (traditional toilets are only a few hundred dollars for comparison), so it’s important to really get into and think about what it’ll bring to your life and how it’ll improve it on a day to day basis.

One key thing to consider, however, is that a composting toilet can be built for a fraction of their market price if you do most of the work yourself. While this naturally won’t be an option for everybody, it’s an interesting idea for the mechanically inclined. All you have to do is buy the materials, watch a few tutorials, and you’re good to go.

More money in your pocket at the end of each month

Even if you go out and spend a lot of money upfront for your composting toilet, you’ll make some of that money back each month on your electric bill.

While electricity costs vary wildly from city to city and throughout various countries, they all have one thing in common. Composting makes that number go down, down, down. So if you can hold onto your composter for long enough, you’ll actually find yourself spending far less all-in than your neighbor down the street that keeps his household traditional.

Your small footprint toilet will generate a nutrient-rich fertilizer without spending a dime

One of the greatest, inadvertent benefits of owning a composting toilet is the waste itself. I know that it sounds crazy (it feels crazy to type out too), but it’s true. You’d never believe how multi-dimensional your own waste can be.

That’s where the true beauty of increasing your sustainability lies, reworking things you’ve been fooled into viewing as useless to solve problems in an environmentally conscious, forward-thinking way.

Revamp your composting pile, gardens, and even grow a few fruit trees

Your new small footprint toilet can also have a big impact. Naturally produced organic waste is the perfect addition to any composting pile, and the number one way people dispose of the waste generated from their composting toilets. Once the compost has been broken down sufficiently and looks like topsoil, you can even use it as a fertilizer for your plants and garden.

Additionally, your organic waste can provide soil with vital nutrients and microbes that will make it much healthier and help your plants grow. Be sure to not use your composting toilet on your edible plants, though. Restrict it to the non-edible ones to ensure everyone stays safe.

Perhaps the most exciting thing to do with your waste byproducts is starting a small fruit tree farm in your background. Not only will it provide you with delicious fruit for years to come, but it could be a fun family activity growing them. And once you’ve got a few trees planted and set up, spread some compost around them to increase the nutrient density of the surrounding soil.

The power of just one person

The average American family uses 74 gallons (280 liters) per day. About 33% of that gets flushed down the toilet. Perfectly clean, drinkable water swirling down the drain wasted.

Clean, drinkable water is a luxury a lot of people don’t currently have. According to an Oxford study, around 20% of the world don’t have immediate or easy access to drinking water. With that information in hand, it’s hard to justify the rate in which so many of us flush it down the toilet, especially when we don’t have to.
A single person can save 6,600 gallons of water each year while simultaneously producing around 80 pounds (roughly 36 kilograms) of highly usable compost. With a composting, small footprint toilet, not only can you do your part to keep things sustainable, but you can also take your non-edible garden to the next level. It’s pretty hard to say no to that.

Blog Series: Living With a Composting Toilet