«Circular Cities» of the future are expected to reuse as many resources as possible. Today, human faeces from toilets are the most important source of nutrients in wastewater. The recovery of these nutrients is easier with dry toilets than with our current water flushing system. But how can this idea be technically implemented without impairing community sanitation?

Collected material from dry toilets can be hygienized by means of pyrolysis (a heat process of > 350 °C). Experiments and measurements have shown that most nutrients from faeces are found in biochar after the pyrolysis process. These could easily be reused in agriculture or transported, which would complete the cycle. Our current research focuses on the optimal operating concept, the availability of nutrients in pyrolysis carbons and the role a system such as this could play in the future circular economy (or in space stations).