Composting Toilets Frequently Asked Questions

Composting toilet FAQs

Are composting toilets legal in the US?

In general, this question mainly applies to people wanting to build a new home and with a permit for a composting toilet instead of a sewer or septic system, or in public places.

Some states have codes regulating composting toilets, like Oregon, Washington, and many states on the east coast. These codes typically require a NSF certified toilet. Site built toilets are only recently becoming legal.  Arizona is working on a pilot project to create site-built designs approved by the Department of Ecology. Oregon’s REACH code includes guidelines for site-built toilets.
Generally, people who live in a house with an existing toilet can use a composting toilet without breaking any laws so long as they:
1) Have at least one flush toilet connected to an approved sewer or septic system.
2) Don’t transport the humanure across property lines.
3) Don’t create a public nuisance (odors, etc.)

Are there problems with all the pharmaceuticals excreted in urine?

Pharmaceuticals are being found at an increasing rate in fresh water, including the drinking water of many major cities. The following is an excerpt from the report: Urine Diversion: One Step Towards Sustainable Sanitation by EcoSanRes.

There are research projects going on to investigate the environmental effect of pharmaceuticals in urine. By far the majority of all pharmaceutical substances are derived from nature, even if many are synthetically produced, and they are thus found and degraded in natural environments with a diverse microbial activity. This has been verified in ordinary wastewater treatment plants, where the degradation of pharmaceutical substances improved when the retention time was prolonged from a number of hours to a number of days. Urine and faecal fertilizers are mixed into the active topsoil, which has a microbial community just as diverse and active as that in wastewater treatment plants, and the substances are retained for months in the topsoil. This means that there is plenty of time for the microbes to degrade any pharmaceutical substances and that risks associated with them are small.

Concerning both hormones and pharmaceutical substances, it thus seems far better to recycle urine and faeces to arable land than to flush them into recipient waters. Since the aquatic systems have never before been exposed to mammal hormones in large quantities, it is not surprising that the sex development of fish and reptiles is disturbed when they are exposed to wastewater effluent. Furthermore, the retention time of the wastewater in the treatment plants is far too short for many pharmaceutical substances to degrade and recipient waters are also usually connected to water sources.

There are many indications that the possible risk from pharmaceutical substances in the agricultural system is small and far smaller than the risks associated with the present system. One such indication is that in many countries the human consumption of pharmaceuticals is small compared to that by domestic animals, as in most countries most commercial feeds contain antibiotic substances, added as growth promoters. Furthermore, the human use of pharmaceutical substances is small compared to the amount of pesticides (insecticides, fungicides, bactericides and herbicides) used in agriculture, which are just as biologically active as pharmaceutical substances.

Can I use a composting toilet in a freezing climate?

Composting toilets can be used in all climates. The composting process will stop during very cold weather. If possible, keep the composting chamber a heated part of the home and/or insulate it.

Outdoor composting also works. A hot compost bin can be used even in the coldest climates. A cold climate composter writes on Joe Jenkins’s forum,

“This is our second winter of composting our humanure, and it has been a great success.
We’ve had a very cold winter so far. It has been consistently below zero for most of the last 3 weeks. It was -24 yesterday morning, but it was a sunny day so it warmed up to -12 and we decided we’d better take advantage of this “warm spell” to go empty the buckets.
When we checked the thermometer in the active bin, it was 112F. We’re so happy that our compost buddies (that’s what I call our microbe friends) are able to keep things toasty in spite of our very wintery weather.”
D and C
Alaska, January 2012
How can I retain moisture in my compost pile? (in a hot, dry climate)

To retain moisture in your compost pile try some of the following:

  • Do not divert urine.
  • Line the edges of the compost bin with cardboard or flexible plastic to avoid evaporation.
  • Cover the top of the pile with plastic.
  • Add rainwater or greywater to the pile as needed.

View some of David Omick’s moisture retaining compost piles in Arizona here.

How do I use urine to fertilize plants?

Urine should be used like a nitrogen based fertilizer, apply it to the roots of nitrogen demanding crops or plants. You can either dilute it one part urine to 3-5 parts water, or just water the plant with fresh water after you have applied the urine. Remember to alternate between plants and not overfertilizer with urine. We usually alternate between plants being fertilized so each plants receives urine once every two to three weeks. If you have a small yard and don’t need all the urine for fertilizer it can be added to the food or yard waste composting bin and will provide extra nitrogen to the compost.

I can’t find sawdust. What else can I use in my composting toilet?

Any fine, organic material will work, for example leaf duff, coffee grounds (ask at coffee shops, consider slightly drying out the grounds before using them), or rice hulls. Experiment and find what works for you.

I’m working internationally and want to recommend a composting toilet. Which type should I recommend?

The best type of toilet depends upon the situation. Questions like:

  1. Who will be using the toilet?
  2. Who will maintain it?
  3. What type of toilet do people want to have?

will determine the best design. Anytime you want to recommend a type of toilet make sure you have personal experience with it. What level of maintenance does it actually take to upkeep the toilet? If you haven’t done it yourself it’s not possible to give people honest, accurate, information about what they will need to do.

The book, “Community Guide to Environmental Health,” has resources for choosing composting toilets. Groups like the Sustainable Sanitation Network have an active forum on international projects. Composting toilet pioneers like Joe Jenkins have extensive experience working internationally and offer advice.

What are the pros and cons of urine diversion?

Urine can be diverted and collected separately from feces. It is easy to collect urine without having a composting toilet for feces. Sometimes it’s also beneficial to include a urine diverter with a full composting toilet.

Pros of urine diversion

  • Reduces the volume of feces to be composted.
  • Reduces the amount of sawdust needed.
  • Enables the collection of urine fertilizer, a nitrogen rich, easily usable product.
  • Can “fix” a poorly functioning composting toilet by removing the liquid portion. Some toilets don’t manage liquids well.

Cons of urine diversion

  • Requires two collection chambers to manage (one for urine and one for feces), or a place to soak away the urine.
  • Using a urine diverting toilet takes practice. New users are likely to clog the urine diverter which makes the toilet unusable until it is cleaned.
  • The compost from the feces is less nutrient-rich than in a toilet without urine diversion.
What do I do if flies get into my toilet?

It takes around two weeks for fly eggs to hatch into flies. Sawdust bucket type toilets that are emptied more frequently than every two weeks won’t have flies to worry about. Larger containers that fill for longer than two weeks will probably have an occasional fly outbreak. First, try to prevent flies from getting in. Make sure the toilet lid fits snugly onto the soil seat. Install screens on any vent pipes and caulk any cracks where flies could enter.

During an infestation, if possible, empty the toilet and clean out the container. Or, purchase neem oil from a nursery or garden store. Dilute it in a spray bottle and spray into the toilet for a few days. Neem oil is effective on both fly larvae and eggs.
Learn how to build a simple fly trap from compost toilet pioneer David Omick (scroll down to find the instructions here)

What is the difference between a “dry” toilet and a “composting” toilet?

In a composting toilet feces and toilet paper compost with a “bulking agent” like sawdust cover the poop to create air gaps for aerobic bacteria to break down the material. This process is the same as for a household food scrap compost. Urine can be diverted out of the toilet, but it is not necessary. If urine is included more sawdust is added to soap up excess liquid. Composting toilets are often used in areas with easy access to wood shavings, leaf duff, or other suitable cover. The finished product is a moist humus similar to garden compost.

In a dry toilet ash or lime mixed with dry soil are added to create a dehydrating environment for breakdown and die off of pathogens. Dry toilets are often used in arid, dry climates where lime and ash are more available than sawdust. Toilet paper can not be added to a dry toilet, it is usually burned or buried. Pathogens typically die off more quickly in the dry, high pH environment of a dry toilet. The finished product can be used as a soil amendment and resembles instant coffee.

What type of netting should I use for a net-barrel composting system?

Marine netting made from nylon is long lasting and works well in a net-barrel composting system. Landscape netting, made from jute, is lower cost and easy to find, but will also compost over time and need replacing every few years.

Where can I find sawdust?

The ideal type of sawdust is from a sawmill. Unfortunately, this type of sawdust is not available to many urban residents. Wood working shops that cut raw, kiln-dried wood (no pressure treated wood, no plywood, no painted wood) create sawdust and will usually give it away. Call around and ask. Be ready to drop off large plastic bags and pick them up later that day or week.