Michel Riechmann (Ogmo), David Hasler (Ogmo)
Every year, large quantities of phosphorus are literally flushed down the toilet in Switzerland. Now, Ogmo, a spin-off of the Swiss aquatic research institute Eawag, is hoping to close the loop with its product Nutrient Harvester, a urinal that produces high-quality plant fertiliser on site. In this way, valuable nutrients are collected rather than sent to the sewage treatment plant.
If there is one thing that epitomises hygiene and progress, it is the disposal of wastewater and its treatment by means of sewage systems and sewage treatment plants. However, this concept is already more than a century old and has become outdated in some cases.
For one thing, a centralised solution like this is only possible thanks to the immense use of resources such as water and energy. And for another, urine is a source of valuable nutrients such as nitrogen, potassium and phosphorus. Recovering these would be vital for the circular economy and security of supply, but this has not yet been fully achieved.
These issues are particularly relevant in the case of phosphorus: Switzerland imports 15,000 tonnes of phosphorus for agriculture every year, but it could fully meet this demand by recovering the mineral from urine and meat and bone meal ash (see Technology “Phosphorus recycling”).
This is where the Nutrient Harvester from Dübendorf-based spin-off Ogmo comes in – in the form of a urinal. At first glance, the Nutrient Harvester looks like an ordinary urinal. But behind the façade, three steps take place to turn urine into a valuable plant fertiliser.
First, the urine is stabilised by adding acid so that it does not decompose into ammonia and ammonium. This also eliminates a source of unpleasant odours. The urine is then evaporated by 95 percent. This increases the storage capacity of the toilet and thus reduces the maintenance frequency.
The resulting urine concentrate is dried in a final step. The result: A ready-to-use plant fertiliser in powder form. As a by-product, the process even produces clean and germ-free water, which is used as service water due to a lack of certification. All steps take place directly in the urinal for a decentralised and energy-saving solution.
While this may sound like a recipe for success, in reality it’s not so easy to put into practice. The real hurdles faced by the two founders of Ogmo, Michel Riechmann and David Hasler, supported by Kai Udert, Professor at Eawag and ETH Zurich, do not lie in the process of fertiliser production, but in Swiss legislation. The law stipulates that every house must be connected to a central sewage treatment plant, unless this is not possible for compelling reasons. This is not a bad idea in principle, but it has a negative impact on decentralised systems such as the Nutrient Harvester. As a result, Michel Riechmann and David Hasler invest a lot of time in identifying the right business case and developing their idea into a product that creates added value for customers.
It is logical to think that they should take their toilets to countries that do not have such a well-developed and mandatory wastewater system as Switzerland. But Michel Riechmann explains why this is particularly problematic from the outset: “Experience has shown that serious problems can arise when solutions developed in industrialised countries are imposed on other countries. We therefore prefer to demonstrate that innovations work in our own comfort zone and thus create confidence in the sustainable export of the systems.”
The two founders see potential in niches such as mountain huts, where a connection to the sewage supply is simply not possible, or toilets in public spaces. This could include toilets in parks where there is no connection to the sewer system. Connecting a toilet costs on average between CHF 20,000 and CHF 30,000. At those kinds of prices, the Nutrient Harvester is already competitive.
The aim is to make the components cheaper and more robust as they become more widespread, so that the Nutrient Harvester can become a new standard for toilets. Ogmo shows that there is no waste in nature.
