Review

Are Composting Toilets Safe? Portable, Permanent, RV – Decide Outside – Making Adventure Happen

Whether you’re an RV camper who is on the go, constantly, or whether you’re a tent camper out for long periods at a time in locations without flushing toilets, or even if you are a homeowner thinking about using a composting toilet, one of the first concerns you might have is safety. You don’t want to trade one problem for another, so you are doing some reasonable research.

Image by Andrew Martin from Pixabay

I researched the answer to the question, and decided to compile the results in this post so you can save some time.

Are Composting Toilets Safe? Composting toilets are as safe as flushing toilets to use. However, since composting toilets involve more handling of waste, they require extra precautions to protect against composting toilet’s inherent additional risks such as contamination with fecal-borne pathogens.

Composting toilets have many potential environmental and long-term cost benefits that are definitely worth exploring. However, there are some risks to consider and prepare for. Let’s dive into more detail!

Safety Of Composting Toilets

The process of using a composting toilet itself does not present significant risk. The main purpose of a toilet is to allow you to “do your business” with as little contact as possible, and composting toilets typically follow similar designs to conventional flush toilets, making this straightforward.

Composting toilets have a few additional risks that flushing toilets do not:

1. Taking Out the Poo

Unlike flush toilets, the poop isn’t magically whisked away to “Pleasure Island” like in the story Pinnochio or some other mystery destination. Rather, the poop just sits right where you put it. This means that you have to empty your composting toilet when it gets full.

For composting systems attached to a house, this means you may be emptying your composting toilet 3 or more times per year, while for portable composting toilets used in RVs or cabins, this may be much more frequent, such as every 3-4 weeks during active use.

For car campers, composting toilets can be achieved with a simple 5-gallon bucket with a bag to capture the waste. The bag can be a compostable bag made from organic materials, or another option is to skip the bag altogether and put bulky materials directly in the bucket which helps aerate the poop and aids in decomposition.

Since you are typically using your composting toilet every day (or at least I hope you are), then you will be handling, at best, partially composted poop. This poop may contain dangerous pathogens which can re-enter a body causing disease.

Simply put, because you have to empty out the compost container at some point in every composting toilet design, there is a higher risk of contamination since you are handling the poop, yourself.

2. Where to Put The Compost?

The risks don’t stop there, though. It turns out that partially composted human waste can continue to have dangerous pathogens, even if the compost does not smell or has the appearance of soil.

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As we’ll talk about in more detail, it can take a very long time for all pathogens to die, and there are specific conditions that must be met before composted human waste is considered safe.

So even after you feel you have composted a load of poop successfully, there is still a risk of contamination. This means that you should only use composted human waste on plants that you do not plan to eat. So using it on flower beds, shrubs, trees, and the like and you should be fine.

One exception I haven’t found a source to confirm why this is the case, but apparently many believe that human waste compost, or humanure (as it’s called) is safe to use on fruit trees. *shrug*

3. Improper Use

So, the above risks cover the big ones you’ll face with composting toilets. However, there are other risks if you do not properly use your composting toilet. Composting human waste requires correct temperatures, aeration, liquid separation, regular emptying, and additional bulky organic material (sawdust or coconut husks).

If these steps aren’t followed, then you’re at risk for:

Trapped Gas

Many composting systems require ventilation into the poop chamber. Proper airflow is pivotal to successful composting, as the composting organisms need air to grow and make the compost work.

Without airflow, the smells and sewer gas will get trapped which causes bad smells and is also unsanitary.

Bad Compost

If the proper composting process doesn’t start working, then you effectively have a portable toilet, but without the water. The wrong kinds of bacteria may continue to survive and may make matters worse. When it comes time to empty the composting toilet, you now have more unsafe bacteria to work with.

If you do not put the poop in a better composting system, and try to use it as fertilizer, then you could be spreading disease into groundwater and have more risks of hand-mouth contact, making people sick.

Safety Summary for Composting Toilets

Composting Toilets are safe to use, and they can be safe to empty and take care of if you care for it properly and do not make assumptions. A few important safety tips are here:

  • Ensure that the urine is properly separated from the poop. Too much liquid slows down the composting process.
  • Make sure enough bulky organic matter is used (peat moss, sawdust, or coconut husk). This provides essential nutrients as well promotes airflow in and around the waste matter.
  • Wear gloves and wash your hands carefully as you would after cleaning out a flush toilet when caring for your composting toilet.
  • Just because it might not smell does not mean it is safe to handle.
  • For Portable composting toilets, after 3-4 weeks, the post-poop is not ready for use as fertilizer. Although it’s theoretically possible to fully and safely compost waste in 3-4 weeks, it’s difficult to achieve the perfect conditions with a portable composting toilet. Make sure to continue the composting process after you empty the toilet.

As a reference, the ideal ratios from one study by the Department of Civil Engineering in the University of Toledo are listed here:

Composting Factor Optimum Range
Moisture Content 50-60%
Temperature 40-65°C or 113-149°F
Carbon (bulky organic matter) to Nitrogen (poop) 25-35 parts
pH 5.5-8.0

How Long Do Bad Organisms Live?

The answer is, it depends. A bad compost system can lead to surviving dangerous pathogens for well over a year.

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Composting works through organisms that feed off of the bacteria and nutrients, which generates heat. A compost can achieve temperatures of over 70°C/158°F. Heat is essential for effective composting.

Not only is the correct temperature necessary for composting organisms (mesophilic or thermophilic bacteria) to survive, but the proper ratio of carbon to nitrogen is also required, as well as proper aeration. For a list of the correct ratios for different composting materials, such as sawdust, woodchips, straw, and more, visit Composting in the Home Garden from the University of Illinois Extension.

Different virii and bacteria die off at different temperatures for different periods of time. Here’s a small re-representation of data available at this
phenomenal study completed by World Bank Studies. This temperature is the die-off temperature for all the listed organisms and virii (Enteric, Taenia, Ascaris Shigella, Salmonella, Entamoeba histolytica, Vibrio cholerae), and it assumes all other composting conditions are good.

Temperature of Compost Die Off Time
53°C/125°F 1 Day
47°C/117°F 1 Week
43°C/110°F 1 Month
41°C/106°F 1 Year

These results come from specific testing conditions, therefore, these conditions are very difficult to consistently replicate with home composting toilets, especially portable composting toilets.

If you are not taking careful temperature samples and mindfully keeping the proper carbon to nitrogen ratios, then you should assume that pathogens can still exist well over a year in your human waste compost. Furthermore, temperatures can vary in your compost, so you have to take several samples to ensure consistency.

What Diseases Can I Catch From Using a Composting Toilet?

Great question. To clarify a little, you are at as just as much risk of catching a disease from a composting toilet as you are using a flushing toilet. The danger lies in handling poop such as when you are shuttling the poop to a new compost pile, or when you are using the compost as fertilizer (and some pathogens still survive).

Most of the diseases you can contract from working with a composting toilet are the same diseases and pathogens you can get from contact with feces. A few examples listed in this document from the World Health Organization include:

  • Salmonellae
  • Cholera
  • Viruses
  • Tapeworms
  • Protozoan cysts

Most of the time our body removes infections eventually by getting them out in our poop. This is why we’ve been washing our hands since we were kids so we can prevent infection. Not everyone’s poop has pathogens, but it’s possible to be a carrier and not have any symptoms, so it’s important to take precautions.

Aside from fecal matter contracted pathogens, composting, in general, has other potential bacteria or funguses that can cause issues. The following is a list of potential hazards from the International Association of Certified Home Inspectors:

  • Aspergillosis 
  • Histoplasmosis
  • Legionnaire’s Disease 
  • Paronychia 
  • Tetanus

These are diseases known to trouble compost piles–while the primary ingredients of your compost pile may be different, there are enough similarities for a need to be cautious.

Always wash your hands whenever you use your composting toilet, and make sure to wear gloves, wash your hands, and wear a mask in dry conditions whenever you handle the resulting compost.

Flushing Toilet Safety Vs. Compost Toilet Safety

Flushing toilets still have the same risks because we are still dealing with poop, here. The difference is that when the poop enters the water, it has passed a barrier that keeps the smells and bacteria separated from us.

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As far as safety goes, flushing toilets simplify our lives a bit at the personal level, and we are only required (usually) to deal with our toilet by regularly cleaning the bowl. However, flushing toilets use a lot of water, and processing the poop requires extensive sewer systems that take their toll on our resources.

Is Human Waste Compost Safe To Use In Your Garden?

Any purely composted material is safe to use for food fertilizer. However, the difficulty in knowing if your human waste is purely composted is out of reach for most people. Because of this, it’s much safer to err on the side of caution and when your waste has been sufficiently composted (at least a year if you are not 100% sure on its temperature environment) to not use it for fertilizing food.

Is Human Waste Compost Good Fertilizer?

If you read the Wikipedia article on Night Soil, you can see in the history of using human waste as a fertilizer that humans have been using human waste as a fertilizer for at least hundreds of years. Humans would not have gone through the effort if they didn’t see a benefit in their crops, even if they didn’t necessarily know the health risks.

Composting makes human waste safer, and still maintains a lot of the nutrients, but it’s not as simple as composting the human waste as fast as possible.

The effectiveness of human waste as compost is complicated by additional factors. The speed in which you went through your human waste compost has an effect on its effectiveness.

We know that using high heat for certain time periods will kill pathogens (check out the table in this post to see a reference of time and heat for human waste compost), but too high of heat also kills nutrients. If you compost with thermophilic bacteria at high temperatures, your compost will be safe, sooner, but perhaps at the cost of the nutrients of your compost.

Anaerobic composting means that less air is allowed in the process. Since air brings heat, the composting process slows down but preserves nutrients.

Composting Toilet Options

Amazingly, there are not a ton of options for self-contained composting toilets. Nature’s Head makes a composting toilet ideal for cabins or RVs that comes with a crank that allows for turning the waste, a vent with a fan that speeds up the composting process, and has a split urine collection design to allows for separating the urine and the poop. Pretty darn cool!

There are many other budget options that involve a lot more DIY composting and are a lot more ideal for car camping! For example, this is a snap-on seat that attaches to a 5-gallon bucket for a makeshift toilet. You can use dry bulk materials to help contain the smell, but you will need to quickly transfer to a larger compost pile so you can get enough air flow and turn it appropriately. I wouldn’t do a lot of turning in a bucket as that probably will get messy, quickly.

Summary

After reviewing this post, it kind of makes it sound like I think composting is not a good idea. However, I think composting is a wonderful idea! Just remember that there are additional risks and work is necessary for successful (safe) composting.

Recommended Reading

For practical guidance: The Humanure Handbook

For more academic research: Guidelines for the Safe Use of Urine and Faeces in Ecological Sanitation Systems. This is a fantastic report that explains the stages of composting for human waste.

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