A team of French and Swiss engineers is working to make human urine a credible alternative to chemical crop fertiliser.
Tests have already begun west of Paris, with the human urine fertiliser said to help the crops just as much as conventional petrochemicals.
Fabien Esculier, geochemist at the Ecole des Ponts Paris Tech, said: “Last year, we did tests in greenhouses and we realised that the yield was the same between chemicals and urine. We produced the same amount of vegetables with chemical fertiliser as with human urine fertiliser.”
Tristan Martin, engineer at Paris Tech, said: “There was no difference between a field fertilised with chemicals and a field fertilised with human urine.”
Proponents of the technique say that its widespread use would reduce oil imports, which are currently used to make synthetic fertiliser, and reduce the use of high-polluting phosphate mines.
The technique also means that less drinking water and toilet water would be wasted, which is a priority in today’s ever-increasing drought conditions and hot summers.
Scientists say that human urine is free and widely available, with each human estimated to produce 500 litres of urine per year. Human urine is also between 100 and 10,000 times less likely to be contaminated with antibiotics when compared to usual levels found in organic fertiliser from cattle.
Engineers also found that human urine contains nitrogen (N), phosphorus (P) and potassium (K) – the NPK trio required for all good farming fertiliser. It also contains other necessary elements to help plants grow.
Mr Esculier, from Paris Tech, said: “If we send urine into toilets and flush it into sewers and treatment plants, then we are sending good nutrients straight into our rivers. That could be food for plants. In the river, it helps algae grow, which can cause pollution. Whereas on our fields, it can help crops grow.”
The technique was actually accidentally discovered by Swiss scientists who were working on reducing water pollution.
The process requires a means of separating water from urine, and two buildings on the campus of the Swiss Federal Institute of Technology in Zurich (ETH Zurich) are now dedicated to this, with “separation toilets” one of the principal methods.
The system uses pipes, enabling the separation of greywater – including washing up water, cooking water, showers, and urine. Scientists have even suggested that in future, each property could have a mini wastewater treatment plant installed – no bigger than a usual washing machine – to allow for this wastewater recycling.
To create the fertiliser, the urine is filtered, to “take out the long molecules, any pollution, and the short molecules. Nutrients come through and we use them for the fertiliser”, researchers said.
A version of the product named Aurin has already received federal approval, and is sold commercially in Switzerland and Lichtenstein. Further large-scale tests are taking place in Sweden and Germany.
Some farmers in France are also already using it.
One, Renaud de Looze, a tree grower based in the Isère department (Auvergne-Rhône-Alpes), has been using the Swiss product for several years.
Speaking to news network France Info, he said: “The plants love it.”
M. de Looze even makes his own fertiliser with human urine, by pouring the liquid into a significant quantity of compost, and letting it soak for two weeks, neutralising any smell or bacteria with vinegar.
He then mixes 25cl of the product with 10 litres of water, and uses that on his plants every two weeks.
He said: “That is enough, because any fertiliser – whatever it is – will burn when it is too concentrated and applied too frequently.”