Build a Composting Toilet: Information and Plans

Suppose you are looking for a way to lessen your ecological footprint and participate positively in solutions to improve the environment. In that case, you should seriously consider switching from a flush toilet to a composting toilet system. Flush toilets waste enormous amounts of water each year, but composting toilets operate with little or no water, and their end product (compost) is a valuable soil amendment as well.

However, one downside of switching to composting toilets is that the manufactured brands can be quite expensive – generally starting around $1500 for a basic, no-frills model. However, building a composting toilet on your own for well under $50 in materials is possible.

Owner-built (also called site-built) composting toilets are generally passive in design – meaning they rely on natural instead of mechanical forces. Since they do not have a built-in electrical unit, they will need to be monitored more closely than manufactured composting toilets. Also, they need more labor in terms of their care and maintenance. However, some would say that with this responsibility comes rewards, including an intimate knowledge of how your body is literally recycling waste positively into the environment.

To assemble this project will only take a few hours once all items are collected. The finished composting toilet will be 18” wide and 21” long.

Materials You Will Need to Build a Composting Toilet

  • Four to five identical 5-gallon buckets with lids
  • A standard sized toilet seat
  • A hinged plywood top for the seat to rest on made of 3/4” plywood. The main portion of the top should measure 18” by 18”, attached with hinges to a 3”x18” board.
  • A box for the plywood top (and seat) to rest on, measuring 18 by 21 inches in width and 10” deep. This can be built from two 10”x18”x1” boards and two 10”x21”x1” boards screwed together.
  • Four legs to be attached to the box (3/4” x 3” x 12”) using screws (or a nail and hammer).

You will need to cut a top in the plywood where the seat hole is (draw a circle to cut out using the seat as a template on the top of the composting toilet). The hole should be set about 1 ½ inch back from the front edge of the plywood. During screwing or nailing the legs to the inside of the box, make sure this box’s top edge is about 1/2” below. The top edge is the five-gallon bucket so that the rim will sit tight against the underside of the toilet seat.

How to Use Your New Composting Bucket

Now that you have finished your composting toilet, it’s ready to use. Well, yes, technically, but there are some additional materials you will need to keep the composting process in order:

1) A Compost Bin. Unlike most manufactured, active designs where the composting process takes place inside a chamber attached to the toilet when you build a composting toilet based on the above passive design, you will have to transport it to a composting bin outdoors to undergo the composting process. You may want to locate this composting bin in your garden next to your normal garden composting pile, and you may need more than one bin if there are many people in your household. For more information about purchasing or building your own composting bin, visit The Composting Bin Website.

2) Organic “Brown Matter.” This will be used to cover your “deposits” when using the toilet to create a balanced compost formula. This can be sawdust, peat moss, leaves, hay straw, rice hulls, or other relatively dry and brown organic matter.

You want to ensure that your composting toilet creates nutrient-rich compost that is clean and odor-free (this finished compost is often called “humanure”). To create this, you will need to ensure that the organic brown matter is sprinkled whenever anyone uses the toilet. The material in the bucket should be moist but not wet.

Once a bucket is full, you will need to transport it outside to your composting bin while placing an empty five-gallon bucket in the toilet to replace the full one. In my experience, people often wait until they have three or four full containers (depending on how many they have in reserve) to do all the emptying and cleaning at once. This is not a pleasant task, although it is also not as unpleasant as you might imagine it to be as well. Be sure to cover the emptied waste with additional brown material and to clean the buckets well so that no odors will linger. You should not need to turn this material, and it should compost on its own to create a rich humus material in six months to a year.

For additional information and articles about composting toilets, please return to the Toilet Composting Home Page. I hope you have found this information about how to build a composting toilet to be useful.

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