Doppelnull - Using the potential of the toilet

What it does

Europe's linear sanitation system produces toxic waste, consumes drinking water and wastes valuable nutrients and energy from our faeces. The "Doppelnull" toilet is a sustainable alternative that keeps the nutrients in circulation.

Your inspiration

Many research projects in the field of sanitation show sustainable toilet solutions that make use of our faeces. However, these promising projects rarely leave the academic sphere, as it is a taboo subject for the general public. This frustrated us! So we used the power of good design to overcome our inhibitions about a new approach to sanitation. User-friendliness and aesthetic design make the toilet marketable. In this way, "Doppelnull" closes the gap between technology and people and creates acceptance for a taboo subject.

How it works

The innovative toilet operates in a closed loop. This means that urine and faeces are collected separately using an innovative toilet bowl geometry. The urine flows through the existing pipe system in the house to the cellar, where it is processed into fertiliser in a four-stage process. The faeces falls into a container under the toilet. The airtight container is transported every week to a nearby composting plant. There the contents are turned into humus soil. A subscription system ensures a clean, empty faeces container. The toilet has a cleaning function that cleans the toilet with a small amount of water when necessary. The urine outlet is sealed with an odour trap membrane and the waste-holding tank is sealed with a two-stage lid system. This maximises comfort and meets our high standards for toilets.

Design process

Throughout the process, we were keen to understand both the user and the technology. To do this, we tested existing urine-diverting toilets and interviewed long-term users. This experience helped us understand what was important to maximise the comfort of a toilet. We tested our new mechanism with fake faeces. Interviews with experts in research and the sanitary industry brought us up to date with the latest technology. This knowledge and literature research fed directly into our work.

How it is different

"Doppelnull" favours a modern aesthetic without relying on eco-narratives. It stands out with its soft purple colour and surprising cantilevered element. Our research showed that existing projects in the area of commercial, circular sanitation solutions for separating and dry toilets are currently aimed at a small target group - camping enthusiasts, for example. With an appealing toilet design, we invite a wider audience to imagine the new toilet in their own bathroom. We stage the use of the toilet with a trendy fashion aesthetic. To do justice to the highly complex sanitary system, we present our project in a multi-dimensional way. From the technical to the social, user and system levels, we have taken a close look at everything. The toilet has its sophisticated sanitary system.

Future plans

Our aim is to launch "Doppelnull". We are in contact with a plumbing company. We want to work with users to see how we can improve "Doppelnull". In this way, the project can be a catalyst for change in sanitation.

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