[WORKSHOP] Hack-a-Dixie Happening

For the Emergent Berlin Fest we want to do a hackathon of the typical mobile toilet (in Germany the most common brand name is ‘Dixie’) wich is currently mixing valuable nutrients with disinfectant chemicals and turn them into waste that cannot be composted.

These are the parts we want to ‘hack’:

1. Privacy/ protection from weather

walls, roof & door

door hinges with spring to keep the door from opening

door lock & handle

floor & space inside

The floor needs to be a non-slip surface, the cabin has to be at least 1 m2 to enable people to turn around without touching the walls.

All materials need to be hygienic, sturdy, water- and windproof, UV-resistant and look better than this to give a comfortable feel.

2. user interface


The anti-odour tablets can be replaced by a spray bottle with EM-solution (effective micro-organisms). The EM prevent pathogens from growing and digest the urea before it turn into ammonia that is responsible for the urine odour.

toilet seat

Urinal and seat need to be easily cleanable and resistant to moisture and urea

toilet paper & holder

needs to be sturdy and easy to handle for frequent maintenance (changing of rolls)

There also needs to be a dispenser for the wood chip/ terra preta substrate/ soil needed to cover the faeces. There should be a dispenser for disinfectant/ a hand wash basin with bio-degradeable soap. The more luxurious ‘Dixie’ toilets with a water inlet (connection for a hose) have one.

3. collection unit(s)

tank under the seat

there should be a separation device inserted under the seat to enable separate collection of faeces and urine. This makes them easier and safer to handle.

the tank will need to be devided to store urine (a lot) and faeces (very little) separately

pipe for ventilation to prevent odour

Results are best if the pipe is outside and painted black as this creates a natural draft when the air inside the pipe warms up and rises. If the urine is stored in airtight containers and the faees are kept dry by adding wood chip hardly any odour develops as the aerobic bacteria responsible come from the feaces and interact with the urea.

Tanks should be removable (the cabin needs an opening at the back) without having to re-open the containers/ touch the excrements. Alternatively the urine can be removed without air contact through an outlet and the faeces collector through the top if the seat and separation unit are removeable.

Connecting ideas for alterations on the Dixie toilet:

  • standardize the urine outlet to enable easy connection e.g. with a pee-ponics system for urban farming
  • install a water filter system to use rain water for hand washing
  • use old cooking oil for making soap
  • build a micro-methanizer to make use of the energy stored in the excrements
  • build a worm composting system to fast-compost the faeces
  • connect to a local CSA to find a user for the nutrients
  • develop a passive water extraction system to reduce urine volume for transport
  • develop standardized and fully recyclable pieces for the construction of cabin, seats and tanks, e.g. by using the 3erlin Grid or Open Structures model

Planning for the Emergent Berlin:

today Clemens and I researched how to buy a tradition plastic cabin from one of the rental companies:

Size of the standard cabin: ca. 1,20 m x 1,20 m x 2,30 m, tank ca. 200l
Weight ca. 70kg

Rarely sell their toilets and only rather used ones, currently none available, request through form on the website.
The lady on the phone was sceptical about our plans. Chemical toilets need servicing every 8-10 days to avoid odour, cost for removal of collected urine/faeces/chemo-mix ca. 25,- Euros. Rental toilets cost about 85 Euros for one weekend, 4 weeks is not that much more expensive. Other companies’ prices are similar.

MY conclusion: it looks as if the best option is to buy a new cabin in Falkensee. That way transport is easy, the toilet will last long and is more likely sellable after the event. I will try to speak to the Stadtmission about their request for a non-smelly solution to replace the chemical toilet there & call EcoToi about the price for a permanent service for removing collected material.

As the problems of obtaining and using a real portacabin could not be resovled up to date, and the concept of the Emergent Berlin Festival has changed, too, we did not buy and change a Toilet yet. We did introduce Cyceloo and the Dicxie-Hackathon at the opening session of the Festival and will join their programm on ecological transformation on

Sunday 2.10.2016 at 2pm

with a workshop that includes building a carton model of the planned changes and discussion how to solve the problems we are still facing.

We were 8 people at the workshop, most had experienced composting toilets as a user, some had experience with composting excreta.

We talked about the different modules of the Dixie toilet and discussed various use scenarios for the converted toilet. One is a potential cooperation with a local social NGO where homeless people sometimes queue on the pavement in front of the building. They had a Dixie but removed it because of the smell, now people use the bushes. The situation means: flat surface, no room for tanks in the ground; people don’t all read German, it needs to be intuitive to use correctly; mainly men, mainly urine; there’s danger of vandalism, needs to be fire-resistant and not easy to topple over.


We discussed materials for the walls:

  • Wood looks and feels nice, the three companies in Germany that provide composting portacabins (EcoToi, Goldeimer, Nowato) build with wood. It’s also easier to use for construction, depending on the varnish fully recyclable, after some time becomes less easy to clean if there is no-one there to do it as soon as it gets wet (sprinkled or puked on)
  • Metal is fire-resistant, only looks good if coated which makes it less recyclable, harder to work with, very heavy which is only good if the cabin is intended to stay in place, easy to clean but not all metals are urine-resistant
  • Dixie uses fire-resistant plastic, there are many cabins of this type already out there, mainly one type of plastic so it’s fully re (down)cyclable but fire retardands are highly toxic, looks shabby but is very easy to clean with a power hose (the tank has an outlet for the cleaning water at the bottom that can be connected to the sewers)

Seat/ tank/ separation

We discussed possible seat designs

  • For men it’s better to provide a urinal, much cleaner to use and it separates at source (that’s the thing on the left)
  • A separation seat like this one is not that expensive but it clogs up easily and get dirty because people don’t know ho to aim right, experience shows that it’s not suitable for public toilets unless someone is there to do cleaning all the time
  • the easiest model to achieve separation is a bucket under the seat with a sieve or some small holes to allow liquids to drip to the tank underneath. In a Dixie there is very little room for such a bucket as the tank is a flat rectangle of ca. 40 -50cm deep. A bucket that fits into that space would leave the colleted faeces very close to the bottom of the next person using it: even when covered people wouldn’t like it
  • a possible solution is to open the tank at the bottom and build the Dixie on a pedestal to make room. Problem her is: it makes it less attractive to simpy try it out as you cannot go back to chemical if you find it doesn’t work for that location. The price for such an experiment is rather high and it would then be easier to just build a toilet that is designed for this purpose right away. Dixie is designed to be used with the liquid that can be pumped out through the hole where the seat is.

Odour prevention
A composting toilet doesn’t stink if the feaces and urine are kept separate, the urine is kept anaerobic and the faeces are kept dry and aerated

  • urine can be colleted in a container with a valve. We discussed different types of valves: Ping-Pong ball, commercial valve models (with holes as an inlet), disc valve (like the simple artificial heart valve models), rubber valve made of a condom/ ballon or any other flexible narrow tube that can be pulled over the end of a funnel, inserting a long tube into the container all the way to the bottom so the surface area in the tube is very small and the surface area in the container is not connected to outside air.
  • Maike thought of using oil to cover the surface of the urine to prevent it from getting in contact with oxygen. She tested a EM-Solution: they don’t ‘eat’ the oil, it still needs to be tested with actual urine to see if it works, downside: makes cleaning the container much more difficult. It may not be necessary if we have a good valve.
  • faeces can be covered with (resin and dust reduced) sawdust, activated charcoal or simply a soil and leave mix. There needs to be enough material to cover (see experience at the Berlin OSCEdays 2016) and using a shovel is not intuitive: some people pour water into the toilet to ‘flush’, others loose cover material all over the place, especially the toilet seat which incombination with misaiming will cause it to stick there and make a mess.

Maike suggested installing a ‘flush’ system with a closed box at the top containing the cover material, a turning piece at the outlet of the box that will automaticaly measure the right amount and is turned by pulling a chain, so the box and chain look like a traditional water toilet. The material then falls through a pipe that leads directly into the bucket at an angle that will cover the faeces

  • Stefan has experience with aeration, they use a tube with holes that leads air into the colleted faeces from the side (holes in it facing sideways and down for easy cleaning). That is not so feasible when you want to remove the bucket upwards through the hole, it would need to be inserted from the top. Stefan says there’s no problem with cleaning in their version of the toilet.

Ayumi from the Dycle project has experience with making Terra Preta from Diapers (very similar material)

  • toilet paper needs to be compostable
  • charcoal works well but you need space to store the colleted material
  • if you store on private land German law is not such a problem
    Stefan has experience with leaves: works very well too, no smell

We will advise the NGO that it may be much easier to simply put up a urinal and maybe provide a separate toilet for women (and urgent cases). We will also point them towards Nowato to discuss further options as they have more variations on offer

We will not continue to hack an actual Dixie because it is not well suitable for the necessary changes. Separation is rather difficult to achieve and the toilet tank needs to be cut open to provide access for a removable collection container. We currently have no funds to run such an experiment.

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