Tiny House Details: Composting Commode – Questions Answered

Composting Toilet – Photo by Tammy Strobel

About a month ago I decided to write an article describing our tiny house composting toilet system. As the delay in posting suggests, writing an article about composting has turned out to be a bigger project than I realized. While writing the article I made the rookie blogger mistake of “writing the perfect post”. I tumbled down a rabbit hole of tangents and details and decided I should include some information on the laws and regulations regarding composting in California and Oregon. I quickly felt paralyzed by the sheer volume of information on the topic and yet the lack of technical legal details. Because of this silly fear of being overwhelmed I stopped writing.

With time I realized that all I really wanted to do in the blog post was share what I know and describe the materials and tools we use for our composting toilet. I also wanted to answer any questions that readers have about our composting process. Whenever we do public tours or host the media, our composting commode generates the most curiosity by far. I’ll be writing more on this topic in the future but for now I thought I would answer the questions that were left in the open comment thread. Also I’ve included a video conversation below regarding a composting system that is nearly identical to ours. Laura Allen and her organization Grey Water Action inspired us and we now have a similar compost design. In the video Laura also describes some of the basic legal framework regarding composting toilets in Oakland, California.

Questions from the open comment thread are answered below:

I’d love a general overview, your thoughts and experiences, etc….
I’ll do my best to share my experiences in my answers below and in future articles. The video above also does a great job of explaining the context, philosophy, and experience of using a composting toilet.

Is there a smell?
No. The experience is similar to a traditional flush toilet where the only offending odors occur during use. When the composting toilet is not in use the only smell that I can detect is the earthy aroma of peat moss that we keep in a container by the toilet. We use peat moss to cover the solid waste after use. You can use many different carbonaceous materials to cover the solid waste and typically the composting toilet area will smell faintly like this material (e.g. sawdust, coconut coir, grass clippings, or peat moss are the most common).

How do you use the jar of dirt that’s always in the corner?
It is difficult to see from the image but that “jar of dirt” is actually peat moss. We use the peat moss to cover the solid waste. The peat moss neutralizes any odors and initiates the composting process. To start the composting process you need three basic materials: carbon, nitrogen, and microflora (bacteria). The solid waste (from us) contains the nitrogen and microflora and the peat moss is the carbon. The microflora metabolize the nitrogen and carbon (and oxygen from the air) creating heat and eventually finished compost that is ready for use as top soil.

What about showering, dish washing, hand washing, etc.
I’m not sure what this question has to do with composting toilets but I’ll answer it anyway. We have a hose from a garden faucet for running water to our sink and our grey water is captured through traditional plumbing pipes in the house to a container outside the house. We use only biodegradable soaps in our hand washing and dish washing so we can use our captured grey water to irrigate trees and shrubbery on the property. We currently shower at my parents house during the winter but this spring and summer we will have an outdoor shower set up with a similar system as the grey-water capture described above.

Where does your water supply to the tiny house come from?
We do not use water in our composting toilet system. For our drinking and washing water we have a well on the property with an electric pump. We retrieve our water from a frost-free faucet through a potable water hose to the house. Unfortunately, in the cold winter weather, we have to switch from running water to “walking water” (carrying water to a counter crock) as the water freezes in the potable water hose. On the bright side, when we have to haul water by hand, we become very conscious of our water consumption and typically consume about 1/3 of the volume compared to normal.

I’m very interested in how it is with you two living on such tiny space with a toilet.
The experience is fine and we’ve never had a problem with privacy or odor. We have a door and window blinds to seclude the space. I’m sure some people are intensely private and need more distance from others to feel comfortable but again we’ve never had an issue.

What’s it like when you both are home or have guest and someone needs to use the toilet?
When a guest needs to use the toilet we give them a quick lesson on how the composting process works. If guests feel comfortable with more space we’ll go outside for a bit and give them the whole house.

Why did you choose composting? What other options are there for off grid living. What type is the most like a “normal” toilet?
We chose our composting system because it was the simplest, lowest cost option for us. There are many options for off-grid toilets. Our system is one of the simplest but they also get much more complex. You can even put in a traditional flush toilet septic system off-grid if you desired it. It is important to remember though that all systems require upkeep. Our system requires a small time investment twice a week whereas large septic systems typically require a relatively big time and money investment about once a year.

What is the upkeep like? I’m curious how often you have to empty the bucket? What do you do with the compost when you remove it from the toilet?
The upkeep is pretty easy. About twice a week I empty the container of peat moss and solid waste into our large (50 gallon) recycled plastic composting barrels. I briefly aerate the compost with a long auger tool, rinse out the container with vinegar and water and reinstall the sparkling clean container in the toilet. The liquid waste is separate and we empty that container once a day by diluting it with grey water (1:8) and irrigating the trees and shrubs. The plastic composting barrels (recycled from use as apple juice containers) keep any waste from entering the environment until it has been fully composted and tested to be free of harmful bacteria. Urine is sterile and is not harmful to the environment. To the contrary, when diluted appropriately, urine provides a rich nitrogen source to plants and trees.

Did you look at the Marine composting toilets like the Nature’s head or the Swedish “Separett” toilet systems.? Separating urine and fecal waste makes a lot of sense to me.
Yes, we use a “Separett” in our composting system like Laura in video above. We did also look at Nature’s Head. I really like the self contained aspect of the Nature’s head but the expense and anesthetic all plastic construction made us reconsider. Our friends Audrey and Tomas have a Nature’s head and seem to like it in a recent review.

22 thoughts on “Tiny House Details: Composting Commode – Questions Answered

    • @et and Tyler, Thanks for your interest! The compost barrels take about a year to complete the process. At the end of the process the compost will be tested for colliforms and harmful bacteria. Once the compost is verified to be safe it will be removed from the barrels and applied as an earth/soil amendment around trees and shrubs here on the ranch. We likely won’t put the finished compost on gardens (just to be conservatively safe). Here is a link to more specific information on the process from the Oregon REACH code committee: http://www.cbs.state.or.us/bcd/committees/11reachcode/20110511/051111_Composting-Toilets_JoshuaKlyber.pdf

      • Hi Logan,
        I confess that I haven’t read all of the pdf you posted there. I’m interested in the testing part of your composting. Can you do that yourself or do you have to hire someone? Is there a kit? Is it an expensive process?
        Thanks!

        • Hi Colm,

          I’m unaware of a kit but its typically pretty inexpensive to get a chloroform test done by a contracting lab through the mail. Depending on the extent of testing it requires a microscope and tools for bacterial culturing.

  1. I live in bear country and I would be worried that the barrels curing would be an attractant- even if they do not smell to us. Logan are there any animals in your area that try to get in the barrels?

    • Hi Patti,

      Great concern! I don’t have any bears to worry about but I do clamp metal wire fencing (chicken wire) over the insect netting to keep out anything big or small. However, the biggest critters we have are raccoons. I’m not sure how you could keep a bear out, you may have to build a concrete wall or something. Good luck!

  2. Hi Logan! Thanks for this detailed writeup. I plan to use this type of composting toilet in my tiny house, but I have a question regarding the “separett” unit. In the Humanure Handbook, they specifically recommend not separating solid and liquid waste, because the compost needs moisture to thrive, and that if you use the appropriate amount of cover material, the smell shouldn’t be an issue.

    Were you having issues with smell from the composting toilet and then switched to the “separatt”, or did you start out with it from the beginning? Just curious to find out what I need!

    • Hi Ethan,

      It wasn’t particularly a smell issue. For us it was too much liquid waste to manage mixed in with the compost. Combining the liquid and solid waste was really consuming alot of cover material to soak up the liquid and the heft of carrying liquid waste was considerable. Separating the the liquid waste allowed us to control these issues more effectively and go longer in between cleaning of the compost container (liquid waste combined with the cover material will start the fermentation process and require more frequent changing). We still add water back to our solid waste once its in the barrel but it much easier for us to tirate the liquid amount and reduce our expense in cover material (peat moss and sawdust).

      Cheers and hope we get a chance to meet you in Vermont. It was wonderful to meet you at WDS in Portland!

      • Thanks Logan! That totally makes sense. I never thought of it being a weight issue, but with water coming in at 8lbs per gallon, I can imagine that the 5 gal bucket would get heavy! Do you bring your compost barrel set up with you when you move?

        Likewise about meeting in VT! I hope it all works out. It was great to meet you and Tammy at WDS too.

        • Maybe its just all the coffee, tea, beer and wine we drink but it adds up over time. ;) We have compost barrels that seal up so yes, we will likely be moving with them.

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  4. Logan — I’m glad I discovered your post on composting toilet. It along with your link to the Grey Water Action video clarified things for me.

    I’m wondering whether the composting toilet in your tiny house has venting analogous to what they have in the full-size house in that GWA video. I assume some kind of venting to the outside is required to get an odor-free installation? Or no?

    Again, thanks for your writeup.

    • Hi Herbert,

      Venting is not required but it is recommended. We don’t have special venting beyond the window. It depends on how long your store your compost in the house, how many people are using the toilet, and how often you use the toilet. We have a small 3 gallon container so we change it frequently. With a larger system its likely you would want to start the aerobic breakdown sooner. We don’t have issues with bad smells, mainly because we separate the liquid and solid wastes. Liquid waste can activate a fermentation process with the carbonaceous material leading to unpleasant smells. Although, even this isn’t an issue with a reduced indoor storage time.

  5. Thank you for sharing this great write-up. A quick question- I live in Wisconsin, where it can get pretty cold for five (or more) months of the year, often below freezing. Is this a viable option for my future tiny home? Is there anything I might need to do to prep or protect my storage barrels during that time?

    • Technically compost piles can produce their own heat and be fine if carefully managed. I’ve even seen compost piles used as a heat source for keeping green houses warm or heating water for household use. However, I’m not careful and my piles freeze solid in the winter and go dormant. When spring roles around the compost thaws and starts the break down process again…

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