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Human Urine Essential to Sustainable Farming?

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A prospective research study published in One Earth, a scientific review dedicated to environmental issues, considers that using human excreta could be essential for Europe to be self-sufficient in food by 2050.

The increased use of synthetic nitrogen fertilizers during the second half of the 20th century led to increased productivity. But an excess use of fertilizers, which seem to have reached a limit in yield gains, leads to nitrogen pollution and harmed ecosystems.

The study suggests three pillars to be able to feed the European population in 2050, which is forecasted to increase by 12% in the paper, and to “close the nitrogen cycle of the European agro-food system“. According to the blueprint, the proposed solution could provide all food necessary to the European population by 2050. Furthermore, it would stop import of maize from the USA or soybeans from South America, as well as provoking a reduction of nitrogen pollution by 50%.

The new agricultural system would be based on a dietary with fewer animal products and a better use of crops, for instance with a rotation with legumes fixing the nitrogen dioxide rather than sparing land. But the perspective of European food self-sufficiency also includes a third pilar, far less common: human excreta.

urine diversion toilets in Sweden and Germany
Urine diversion toilets in Germany (left) and Sweden (right). Human urine could be collected and treated for fertilizing lands | L. Ulrich (2009)

Treat and use human urine as a fertilizer

Over the years, the specialization of crops according to the territorial specificities led to neglect the benefits of complementary crops. The increase of livestock and decrease of permanent grasslands brought an unbalanced use of animal manure and an excess dissemination of nitrogen in soils and waters. But with fewer animal farms, the organic manure at disposal would reduce. And it could then be replaced by human excreta, especially urine.

Their hypothesis is actually based on recycling 70% of human excretion containing nitrogen, and notably human urine. In fact, human urine is full of nutrients, including nitrogen, phosphorous and potassium that are essentials in a plant growth.

Recycling urine could potentially be used for fertilizers instead of ending up in sewage treatment plant. It burgeoned in Sweden in the 1990s, with specific toilets for source treatment avoiding urine to be mixed with other faecal matter or paper. Urine diversion facility also exist in Germany or the Netherlands. But those types of toilets, including outhouses during music festivals specifically collecting urine, still remain marginal.

Fabien Esculier, a French researcher in urban water management systems, estimated that the urine from the agglomeration of Paris – 10.8 million people – could help produce wheat for making 25 million baguettes a day. That’s 90% of what the French buy at bakeries daily.

Some companies, such as Toopi organics, are making some tests at greater scale. In fact, research on treatment still needs to be performed before widespread use. For instance, potential residuals of medicines in urine could pose an issue for spreading it on crops. Water management systems in Europe are yet not made for source separation and treatment of human urine either.

Moreover, other than the population aversion of the technique for a widespread use on their vegetables and legumes, a further headwind faces the projection: European organic farming regulation prohibits such use of human urine.

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