Simon Bregar

Sana urban composting toilet

Sana was a result of an one week design sprint, where teams of interdisciplinary design students were confronted with a challenge of rapid environmental and social changes in urban areas, which are occuring in big cities across the world. Our team challenge was how to tackle with ever increasing city waste footprint and closing the loop by transitioning from linear to circular economy. We tried to implement this topic to urban services such as making public toilets sustainable, zero-waste and user friendly. 

Designed as proposal for the city of Prague. 

Industrial design, sustainability


doc. MA Ivan Dlabač
MgA. Vlastimil Bartas

Lea Baniariova, David Navratil, Dominik Novak

Department of Industrial design, Academy of Arts, Architecture and 
Design in Prague

How can we get from here              

Primary problem

              to here?

Secondary problem

Research & analysis

»Promoting a waste product that some consider hazardous as a resource to grow your food may seem like a paradox, but in Britain, a world leader in recycling sewage into agriculture, it is recognised by the government and the EU as the best environmental option

»In Britain, sewage sludge goes through a tertiary anaerobic digestion process that kills off up to 99.99% of pathogens. The treated sewage sludge this produces is referred to as ‘biosolids’ and most commonly comes in the form of dried cake digestate.«

»Biosolids can increase agricultural yields and improve soil condition. They provide nitrogen, phosphorous and potassium in a less soluble form than farmyard manure and artificial fertilisers, which means they remain in the soil for longer and are less prone to leaching into groundwater or run-off, which pollutes waterways.«

»On a global scale we could be recovering much more phosphorus from human waste. It’s estimated that only 10% of the phosphate lost from human excreta is recycled back to the land due to inefficiencies in wastewater treatment or the absence of wastewater treatment altogether. Results from a 2009 study in Chemosphere suggest that, if properly collected, the phosphorus available from urine and faeces could account for 22% of the total global phosphorus demand.«

»Heavy metals are the main concern. These are strictly monitored, however, and regular testing shows that the levels of heavy metals in soils fertilised with biosolids are significantly below the maximum permissible levels. In fact the levels are so low now that the Soil Association has recommended the European Commission lifts the ban on using biosolids in organic farming.«


»Ecological sanitation systems are starting to come into use all over the world that separate human excreta from other waste streams. Ecological sanitation (ES) includes urine diverting toilets, high-tech vacuum systems and composting toilets. These inexpensive systems can be used in various contexts from small villages to large municipalities. ES separates greywater, human faeces and urine and stores them in underground tanks.«

»WaterUK estimates the total value of nutrients in biosolids recycled to agricultural land in Britain at £40–£50 million per annum. The value of preserving life in our oceans, the health of our soils and the quality of our water is priceless, and as water and energy become more scarce and costly, and phosphorous reserves run out, ES could become a much more attractive and cost-effective prospect.«

»According to the UN 90% of wastewater in the developing world is expelled, untreated, into the oceans. Whilst rich countries have had the finances and governance to manage sewage effectively, there’s still a long way to go in making this universal. How will we, as a global community achieve it?«

Solution? Let’s close the loop!

Ecological sanitation studycases

Public sanitation studycases

Design concept


©Simon Bregar