What is a composting toilet, and how does it work?

What is a composting toilet, and how does it work?

Composting toilets save water and money with less environmental impact.

Key tips to remember

  • A composting toilet can help you conserve water and save money
  • Composting toilets use organic, carbon-based material to make compost
  • Composting toilets separate solid and liquid waste and require maintenance
  • A composting toilet system is expensive to install but saves money over time
  • There are two main types of composting toilets to consider

It may not be anyone’s favorite discussion topic, but if you’re serious about conserving water, you need to talk about your toilet. Flushing a toilet uses between a quarter and a third of the average household’s water. That’s a lot of wasted water, if you assume that the average person flushes five times a day, or nearly 2,000 times a year. It’s especially bad when you consider that toilet flushes were only limited to 1.6 gallons per flush in 1992 — and millions of older toilets that use up to an astounding 7 gallons per flush are still in service. Even if all your toilets are circa-1992 and newer, that’s still more than 2,300 gallons of water literally flushed per person every year. 

What if you wanted to conserve all that precious fresh water, along with all the money it costs to use it in your home every year, all while lessening your environmental impact? If you don’t mind considering something a little different, a composting toilet system, sometimes called a dry toilet, might be a great solution for you. While you’re here and we’re on the topic, you might also want to read our toilet maintenance checklist or learn how to unclog your toilet without a plunger. Read on for more about composting toilets.

What is a composting toilet?

Before you shake your head in disgust or make the mistake of eqwwwing a composting toilet with a port-a-potty or an outhouse, take a little time to learn how composting toilets work so you can make an informed decision. Hopefully, this post will help get your head around the facts before deciding on (or against) a composting toilet for cabins, condos, vacation homes, mother-in-law cottages or even your primary residence. Simply defined, a composting toilet is an alternative to a flush toilet. Instead of flushing with water, it mixes moss, sawdust or coconut with solid waste and minimal water to create viable compost (a fertilizing soil conditioner) that can be used to grow things. 

How does a composting toilet work?

As we’ll discuss later in this post, there are different types of composting toilets. In general, they work on the same principle for breaking down waste. Solid waste breaks down when the proper levels of moisture, carbon, nitrogen and temperature combine in the proper environment. Typically, composting toilets keep urine separate from solid waste so that nitrogen levels stay at reasonable levels. Airflow vents out as waste breaks down with oxygen and aerobic bacteria. As a result, the process eliminates odors and uses far less water. It’s a natural process that a highly engineered composting toilet is designed to facilitate. Temperature control is also important, so some systems employ sensors and thermostats that monitor the system, its moisture levels, chemical balances and temperatures at appropriate levels.

What are the benefits of a composting toilet?

If you’re interested in reducing your environmental impact, preserving your community’s freshwater supply, saving money on your water bill, and creating viable plant fertilizer from your own waste to enrich your soil for better luck growing food, a composting toilet could be a great choice. Perhaps you live in a rural area, where city sewer or expensive, carefully regulated and expensive-to-maintain septic systems are not even an option. Maybe you’re an avid gardener, eager to regenerate your soil with active microorganisms while reducing the need for chemical pesticides and fertilizers and increasing vegetable yields. You might want a solution for a boat or an RV that lacks plumbing options. Initial costs can be high, particularly in homes, so there’s also a good argument for upgrading your existing system to more-efficient traditional flush toilets. However, depending on your circumstances, a composting toilet can be an attractive solution that also saves in usage costs over time.

Different models of compostable toilets

There are two basic types of compostable toilet systems: self-contained and centralized. Self-contained systems are often used in more confined spaces, like campers, RVs, cabins or boats. They consist of a single unit with tanks that collect liquid and solid waste separately, where each must be removed manually for disposal. Composting occurs within the unit itself. Centralized systems, however, are much larger and typically installed under a home or outside, where a storage tank accepts all waste. Though centralized systems can vary in how they flush waste and how many chambers they contain, they are more akin to the traditional flush-toilet experience. The primary difference between the two types is where the composting happens.

Cost-effectiveness of a composting toilet

While self-contained models can range from $650 to $3,000, centralized (sometimes known as “split”) systems cost between $3,000 and $5,000. Though purchasing and installing a traditional flush toilet often costs considerably less, remember that a compostable toilet will save money over time due to the drastic reduction in water usage. If you compare these costs with installing a septic system, keep in mind that a compostable system typically installs for about a quarter of the price of a new septic system. Though both self-contained and centralized/split systems use electricity to operate fans, vent gases, power heaters or even operate vacuum-flush features, solar cells can power some of them. In addition to the costs of your composting toilet system and installation, remember you’ll need to set up an outdoor composting system as well, if you haven’t already. This will introduce additional expenses as you create an infrastructure for using your compost.

Disadvantages of composting toilets

Most people aren’t super enthused by the idea of manually removing their own waste products from self-contained compostable toilets, which is why centralized systems are popular. But for others, this isn’t a big deal. The inconvenience of collecting and disposing of liquid waste in addition to solid waste is also a dealbreaker for some, but at least you won’t have to consider 

DIY toilet tank repairs. Others won’t mind setting up a grey-water system to facilitate this process. There’s also the unexpected power-source requirement, which could be difficult in some rural or mobile applications. Setting up a system incorrectly and causing it to malfunction or require significantly more maintenance than a traditional toilet is also a risk, and things can get stinky in that case. The idea of constantly monitoring airflow, microorganisms, temperature, moisture levels and pH balances is also a daunting challenge for many. Speaking of toilet maintenance, you might be wondering whether home warranties cover toilets.

Misconceptions about composting toilets

Those unfamiliar with composting toilets might assume that they always stink, but this is not the case. When a composting toilet is installed and maintained properly, it should not omit odors any more than a traditional flush toilet. If liquid and solid wastes are separated effectively, the carbon-rich moss, sawdust or coconut byproduct mixes with the solid waste; the venting system maintains airflow; and moisture, temperature, pH and microorganisms are maintained, keeping odors at bay. Another misconception is that composting toilets encourage or harbor insects, but this too is incorrect. Insect infestations can happen, but they’re a sign of a bigger problem that needs correcting. 

We hope this post has helped you understand more about composting toilets and whether they’re right for you. Stick around and browse for more helpful posts on a wide range of home-improvement and DIY topics.

The information in this article is intended to provide guidance on the proper maintenance and care of systems and appliances in the home. Not all of the topics mentioned are covered by our home warranty or maintenance plans. Please review your home warranty contract carefully to understand your coverage.

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