Tiny House, Tiny Living, The Tiny Life.

Compost Toilets and Biogas Systems

biogas4Top question when someone hears we live in a tiny house? What do you do about the bathroom? Everyone is curious what the is deal with waste disposal. We use a composting system-some folks buy incinerators, others buy fancy compost toilets and then there are those on a budget who use the bucket system.  After taking a permaculture course I became fascinated with going a step beyond the composting system. We had a lecture on biogas systems and the biofuels made available by the anaerobic decomposition of waste. Since that day I’ve been researching systems that have been widely used throughout India, Africa, and Latin America. In the US these systems have been used for some time by water treatement plants as an alternative form of energy for generators  in the case of emergencies.

biogas3Biogas systems take waste and capture the methane from the anaerobic decomposition of the effluent and supplies you with fertilizer and fuel when the cycle is complete. A digester is the apparatus that controls the decomposition and consists of a sealed tank or pit and a means by which to gather and store the methane. I’m so interested in these systems for reasons of sustainability and efficiency. Composting waste is an alternative to the current system of polluting a finite resource but biogas systems take it a  step further by gathering fuel that does not require invasive collection from the depths of the earth. It takes toxic waste, keeps it out of the environment and allows it to be used in multiple ways to human benefit.


There are many different shapes and models of biogas plants but by far the most popular and wide spread design is the Indian cylindrical pit design. It has proven to be reliable in many different environs and it’s widespread use dates to the 1970’s. There are two basic parts to the design, a tank that holds the slurry (manure and water) and a gas cap or drum on the tank to capture the gas.


My dreams were dashed for building one of these for our tiny house when I discovered that two people don’t make enough poop biogas feederto fuel even a small system. You need around 6 people and 6-8 cows for the system to function in a way that meets fuel needs. The first step of building such a system is getting community support and finding other folks who want to use such a system together. In a city this would make a lot sense but in our current situation out in a rural area, just me, Cedric and the pup it’s not a realistic option.


This technology is one that I will keep on the back burner for now but if this article has peaked your interest at all then definitely check out the via link at the bottom of this page. There is a detailed construction manual for the Indian cylindrical pit system that provides advantages, disadvantages, considerations, costs, labor input and more excellent graphics as well as charts on building this biogas system. I hope to be assisting with the construction of such a system in the near future so until then share you interest and experience if you have it with biogas and biofuel systems. I’d love to hear what folks think of the implementation of these systems and how the social perspective on waste treatment can be altered toward regenerative design.


Your Turn!

  • How do you see alternative systems fitting in to the philosophy and living of the tiny life?


  1. I too was disappointed at not being able to provide enough material to use one of these. Low volume of greywater produced by 1 person also complicates having a nice greywater pond system. Definitely something to consider for a larger group or people with livestock.

  2. Anyone out there tried the incolet or other incinerating toilet. I’m considering using one for my tiny home and wanted to know if anyone else has personal experience with that.

    • I can’t say I’ve used it, but I’ve heard a lot of negatives.

      It uses a lot of energy.
      It smells when cycling
      After it’s been used, It can’t be used again while it is cycling (1 1/2 hours)
      They break down.
      They create heat when cycling.
      they make noise when cycling due to fans in use.
      expensive- $2000 to $3000

      Good luck.

    • HI there Alan. If you end up going that route we have one in excellent shape that we are selling. You can email me at gabriellafreedom@gmail dot com if you want more info.

    • HI there Alan. If you end up going that route we have one in excellent shape that we are selling. You can email me at gabriellafreedom@gmail dot com if you want more info.

  3. Seems really … disgusting, complicated, and expensive.

    Simple is best for long term.

    I have a compost toilet with urine separator. The key in separating the liquid which is sterile and can be readily used as fertilizer or dumped on the ground.

    The solids, which have the consistence of cookie dough, I simply freeze.

    The freezing kills most of the harmful bacteria that makes solids a concern. It also kills smell.

    After the harmful bacteria is eliminated, the solids which are mixed with absorbants like shredded paper and toilet tissue, can be added to compost pile.

    My compost toilet has a fan down near the floor. When I’m using toilet any smell goes right out. I never smell anything.
    I used simple large cookie tin lined with shopping bag and absorbants.

    When done using toilet, the liquids have gone down the drain, and I simply close the bag, put the lid on the tin, and put it in the freezer.

    My natural waste materials cease being a pollutant right here, at the source.

    People who use flush toilets only send their waste materials elsewhere and in the process allow it to multiply. Defecating in drinking water is so not cool.

    Its funny. We tend to think of the refrigerator and freezer as something that preserves food. But they do totally opposite functions.

    A refrigerator preserves life at 40 degrees.
    A freezer kills life at 0 degrees. Use it to your advantage.

    So the question is

    • You might want to rethink that process. From what I understand freezing can slow down some pathgens but doesn’t necessarily kill them. E. coli is known to survive freezing. High heat is a more reliable method, as is proper composting. Prolonged winter temperatures of minus 20 F won’t kill pathogens either and once an outhouse thaws out in the summer it’s not rendered hazard free from being frozen all winter. 0 degrees F isn’t really that cold, labs often store bacteria at minus 80 F and revive them to work on.

    • What if one doesn’t want a freezer

  4. You’re right.
    As was stated, freezing kills most harmful bacteria. I’ve considered adding a second step AFTER the freezing of heating the waste. At that point only select bacteria will remain, I don’t think it would be a big burden.

    Apparently 185 degrees for XX period of time would kill all bacteria.

    Up to this point, I’ve simply been disposing in the trash, the small bags when they are full, after they are frozen. Usualy one a week. I wasn’t quite sure of procedure, didn’t want to do anything that might be a concern, and just haven’t had the time to take it that final step.

    The freezing is certainly better than flush toilet, and better than typical compost which can take up to a year to render solids safe.

    I’m in the process of building a better compost bin that is enclosed. I think I will get a pot, from Good will, for heating and a thermometer.

    I’m amazed what these worms do. I put frozen vegetable remains in the pile, burying it under tree mulch, give the pile a bit of water each day, and a month or so later it’s just wonderful garden dirt. With the new composter, I’ll be able to collect the compost tea as well.

    Thanks for the reminder.

  5. check out the humanure book on amazon. tells us all we need to know amd how to do it right, good luck.

  6. Ryan, you can use a digester for small amounts of pee and poo. Just don’t expect to get very much gas or fertiliser. First you have to figure out how much you actually produce as the volume will determine the size of the containers you make it out of. The simplest is to make it out of a 45 gallon barrel with a 30 gallon barrel turned upside down as the gas cap. This is still too big for one or two people, but you get the idea. BTW, the gas produced most closly resembles natural gas, not propane, so it is best used in devices equipped with natural gas orifices. It can be used, with some losses in performance, in propane burners if you can increase the gas pressure (ie put a brick on the gas cap). Don’t give up yet, you’ve barely started looking at it!

  7. John is right. The gas produced from compost will be about 45% methane (natural gas) as well as other inerts (CO2, O2, and Nitrogen). If you want it to be appliance-ready (say, for a stove), you will have to process or strip the gas of the 02 and CO2, which is basically useless in such small quantities.

    Methane has to have the proper ratio to ignite. What you get from composting just won’t do it. Hope this helps.

  8. Black water is the big issue. I have looked at multiple systems and emptying out the unit like a litter box is not what I want to do now or in the future. I’m out in the country and before I empty bins I’d invest in a septic system or separate the grey from the black and have a LARGE holding tank for the black and have it pumped out regularly. A 1000 gallon should last 500 flush cycles or more with a very efficient grinder system.

    I don’t want to dump anything, like e coli, in the ground near my house, garden, or anything downstream.

    Any comments appreciated.

  9. How much gas can you get from a 2-4 person household? I know it is far not enough to power a heating, hot showers and all that, but is it maybe enough to cook a meal a day? That would already be something. Hot water and heat can then still come from solar and wood. Or is the methane not enough for that even? Would it help to add other waste – food scraps, yard waste, Chicken manure? Is there a danger of explosion? If there is really O2 in addition to CO2 in the gas, that may be explosive. It would suck if the biogas barrel explodes (not to mention the gas line and the cooking stove).
    Thank you.

  10. Ryan,

    I found this blog by searching for this exact union of ideas. The potential here requires us to pursue the possibility a bit further.

    Firstly, manures of any kind or not actually ideal for an efficient biogas system. See here: http://completebiogas.com/B_ARTI.html. According to research cited, food scraps (high in nitrogen and oils) are one example of an alternative or complement to manure that will increase the productivity of your system.

    However, it is ideal to have a real use for our excrement, as well as that of our animals. Remember that the effluent is an even more valuable soil amendment than when it is first mixed with water and deprived of oxygen.

    My question is, can two homesteaders produce enough usable waste products to produce enough gas for themselves to cook a meal a day? And, what sort of regular labor input would we be looking at?

    I think that in the end, biogas will best be used in conjunction with wood or solar, depending on the time of year.


  11. Ryan,

    I’m a fellow smart poop passionista. Thank you for writing this article and doing this research. I’m getting certified in Boulder County, CO, a very cutting edge county full of rich people. Boulder County is pretty strict with its septic systems and requires a licensed contractor to install them. The same license though certifies the installation of composting toilets. I’ve been fired up about sustainability and Eco housing for more than 15 years. I’ve built several passive solar adobe homes in NM and some spared no expense and still went with the 5-gallon bucket system inside with great success. I’m also an excavator and I just recently helped with with some septic test holes on a new lot in Boulder County. The soil percolation and soil composition tests failed the standard requirements to allow for a standard septic system and leach field. So I’ve been thinking about how I might be able to offer an alternative solution for this potential homeowner and future builder. I thought about a compost system but those are still too strange for most mainstream Boulder folks. So I’m now thinking that because septic systems are required to provide service on the order of 75 gallons per person per day (doesn’t that seem like a ton of water? I don’t use anywhere near that much), I could design a system that only processes a much smaller amount of black water by way of separating greywater from the black water system. Greywater can then be processed safety with wetlands and retention pools while the black water is digested for fuel. I’m also wondering if at the very least we could find a way to splice our small amounts of poop fuel in with untility-provided fuel. Any thoughts on this? Have you ever heard of splicing together two fuel lines of unequal pressure?

    At any rate. I’m fired up that you’re on this planet thinking about these things too and the same goes for every other alternative-smart-poop-processing enthusiast out there.

  12. i need to start a human waste diogester

  13. I think biogas could still work for 1-2 people if you fed it weeds and food waste also, at least during warm months, and figured out how to keep it from freezing/ceasing digestion during the winter.

    Alternatively, you could do worm compost. Worms do a decent job of ridding the waste of pathogens, as I understand it. You may still not want to rub your face in the castings, but you could certainly put it outside or give it to flower-gardeners without worry. To compost toilet waste, you’d just need a big enough system that can handle the volume of feces but small enough that you can keep the worms above 50 degrees through the winter. This might be an issue unless you have a greenhouse or live somewhere mild, but you should figure out the math. You’d also need worms, something like sawdust to feed with the feces and minimize smell, and you’d need to separate out urine.

  14. Great article and comments folks. I butcher and get livestock butchered on my property. Both small and large. Could the offal from rabbits, chooks, sheep and pigs be used in a digester effectively as well?
    I currently compost or incinerate and then compost them but sometimes i don’t have a heap at the right stage to take any more, hence the incinerator which isn’t working too well. Ideally I’d design a better incinerator to deal with the bones and put the offal in the digestor.
    Alternatively I’d go back to putting them through a composting toilet process.

    • Oh wow. That’s an interesting idea. I think the answer is yes, with qualifications:
      1) offal I’m sure it could handle provided you have a big enough system to keep it digesting for 30+ days so as to fully digest it and kill pathogens. You’d also need to balance the carbon and nitrogen, like you have to in composting. All that said, the fat and protein would probably contribute to some high quality biogas!
      1) bones might be trickier. I keep reading pronouncements that bones and eggshells can’t go in digesters but nobody has explained why. My guess is that they’d disturb the acetic acid accumulation that the methane producing bacteria need to make their methane. I wonder if there’s some way to pretreat the bones with an acid so this isn’t a problem. But I don’t know. Barring that, you’d have to do something else with them.

      • Thanks Nick,

        I’ve seen plans somewhere for a high temperature incinerator and that’s what I’ll be dong with bones, eventually. Either that or a hammer mill when I end up with a surplus of ‘free’ power.

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