Kildwick Revolutionizes the Composting Toilet

Years ago, when we first wrote about composting toilets possibly replacing flush toilets in our homes, commenters were appalled, with one suggesting that "no one will want this inside their house. I know this, because I still have a few teeth in my head and a few friends in town." But as I have previously written, the reality is that "we can't continue using drinking water to flush away our waste, and we can't afford to keep wasting our waste; that's why you now see composters in Living Building Challenge certified buildings like the Bullitt Center and the Kendeda Building in Atlanta.

A problem with many composting toilets, including the one I own, is that they are big, to allow the air to circulate around the poop. They are also plastic, they draw a fair amount of electricity to run fans and heaters, and the fans can be noisy.

That is why I was so surprised to learn about the Kildwick composting toilet. It is not huge, it is made of Forest Stewardship Council (FSC) plywood, and except for one model, there does not appear to be a fan.

The Kildwick is a urine separating toilet, which we have seen in the Separett and Nature's Head toilets (both on our best composting toilets of 2021). This significantly reduces the smell, which Kildwick says "occurs mainly when urine comes into contact with faeces. Mixing them accelerates the decomposition process, resulting in stinking rot, bacteria, and ammonia. The separation of the two substances by means of a dry toilet is the ultimate odor solution." Kildwick tells Treehugger:

"Modern dry source separation toilets are nearly odorless. This is achieved by collecting the liquids and the solids in separate containers. There are a slew of international manufacturers who offer toilets based on this principle. There are also variations to this set-up. For example, there are toilets where the solids tank is equipped with a crank system that mixes the faeces with coconut fibre to facilitate the composting process. This system can have the downside of an unpleasant and inconvenient emptying process." 

"The handling of the Kildwick toilets is much simpler and will not cause this or similar 'exposure' issues. The separator insert creates a safe and clean mechanical separation of liquids and solids. Thus, the liquids are collected in a washable, stable urine canister. The solids are collected in another tank lined with a compostable bag for convenience. Each new and empty bag needs a handful of cover material initially (we offer sustainable, compostable organic Miscanthus bedding). Then, each new 'filling' needs to simply be covered with about 2 handfuls of bedding which causes the solids to dry. Once the solids tank is full, the bag is removed, tied up and brought to the composting bin. Toilet paper goes into the solids tank as well, which not all dry toilets systems allow for. The Kildwick separator is quite effortless to clean using a gentle detergent in a spray bottle and a soft tissue. Hygiene made easy!"

The cover material seems to be key to drying it out and absorbing the smell; you go through a lot of it, a 17-liter bag lasts two weeks when used daily by two people.

There is an optional fan available, what looks like a computer fan running on a USB power source. Kildwick tells Treehugger: "In regards of equipping dry toilets with fans: There are situations where we will always advise the installation of a fan. From our experience, we can say that approx. 60-70% of our customers operate their Kildwick composting toilet very successfully and happily without a fan."

However there are a couple of cultural differences that may be coming into play here, The Kildwick is made in Germany, and it may well be that Germans are not as sensitive to bathroom smells as others; they grew up with, and many still use "shelf toilets" where poop falls onto a ledge, so that it can be inspected for signs of parasites or intestinal diseases. I found them to be really smelly even though the urine is separated, and suspect that the Kildwick might smell a bit too until the Miscanthus bedding is added. In other words, if I was buying this composting toilet I would get the fan option.

Another complaint one often hears about urine separating toilets is that men have to sit down to pee, which many object to. Another writer who dislikes German toilets notes "The German toilet's shortcomings are not limited exclusively to Number Twos. It is almost impossible for males to urinate while standing without soaking the bathroom. Urine sprays everywhere. It's not uncommon to see little stickers on the underside of toilet lids, reminders to less civilized males that they really need to embrace their feminine side and sit the hell down."

But these are minor inconveniences compared to the environmental benefits. Kildwick tells Treehugger:

"When Perato GmbH acquired Kildwick in April 2019, [it was an English design] it was immediately clear that all production cycles would be re-designed in a way that’s as environmentally friendly as possible. The use of plastic is minimised. We refer to the use of recyclable plastics only and only in case there are no alternatives. The separators/ bowls that used to be made of glass fibre are now made of recyclable, lightweight and easy-to-care polystyrene. The packaging is as plastic-free as it’s currently possible as well.  The entire component production takes places in our region to keep the transportation routes short and the carbon dioxide emissions low. Fair payments for employees and suppliers are as important a part of our overall philosophy as is reducing our environmental footprint."

As for shipping it longer distances, the unit can be purchased flat-pack or kit form, which will reduce the cost and impact of transportation.

There is much to admire about this thoughtful design, which many people might be comfortable using instead of a flush toilet. If you follow our posts on the tiny house movement, it becomes obvious that dealing with waste is a fundamental issue when people go off-grid and off-pipe. But the day is coming when it will be an issue for everyone; Kildwick tells Treehugger that Europeans are embracing compost toilets for many of the reasons I mentioned earlier:

"We see a steady increase in the demand for waterless solutions. This is partly due to the rising public awareness on water scarcity. This makes more and more people look for sustainable toilet solutions. Water shortage doesn’t only affect emerging and developing countries. Many areas in continental Europe are experiencing a growing water crisis due to the dramatic change in climatic conditions and also due to the political mismanagement in the agricultural sector."

Coming soon to a bathroom near you. More information at Kildwick.