Human waste could help tackle a global shortage of fertiliser

Cabbage plant tests suggest fertilizers derived from human urine and feces are safe and could help keep food prices down

To Brian Owens

Cabbage plant trials show that fertilizers derived from recycled human urine and feces are as safe and effective as conventional fertilizers. Fertilizer shortages contributing to the rise can be mitigated – if people can be persuaded to use them.

Nitrogen-based fertilizers are produced in an energy-intensive process using natural gas as a raw material. Human waste can be a good source of phytonutrients such as nitrogen and phosphorus, but it can also carry disease-causing pathogens and parasites, so be careful to keep it safe. It must be treated. It is used as fertilizer in some low-income countries, sometimes untreated, but is largely abandoned in high-income countries.

Franziska Hafner and her colleagues at Agroscope in Zurich, Switzerland, used cabbage grown using organic fertilizers derived from Vinas, a by-product of ethanol production, and fertilizers made from processed human urine and feces. compared.

Yields of cabbage grown on nitrogenized urine fertilizer (NUF) were comparable to those grown on Vinas. Cabbage grown using faecal compost, or compost and his NUF together, had lower yields, but the study found that this fertilizer could increase soil carbon content in the long run.

Researchers also tested over 300 chemicals in the manure, including pharmaceuticals, flame retardants and insect repellents. Only 6.5% were detected, all at very low concentrations. Of the 11 drugs found in the compost, only two were found in the edible portion of the cabbage: ibuprofen, an analgesic, and carbamazepine, an anticonvulsant and mood stabilizer. As low as it gets, you need to eat 500,000 cabbages to get a single dose.

“The product obtained by recycling human urine and feces is a safe nitrogen fertilizer suitable for growing cabbage,” Hafner said in a statement. “They yielded similar yields to conventional fertilizer products and showed no risk of pathogen or pharmaceutical transmission.”

Researchers estimate that if properly prepared and quality controlled, up to 25% of Germany’s traditional synthetic mineral fertilizers could be replaced with those recycled from human urine and feces. . In some regions, the trend has already started. His one of the NUFs they tested, Aurin, is approved for agricultural use in Austria, Switzerland and Liechtenstein.

Benjamin Wilde of ETH Zurich had similar results in yield and safety when testing NUF in field trials in South Africa. But it takes a certain amount of persuasion to get people to use them. The Zulu farmers he worked with, like people in many cultures, have strong social taboos about human waste. But long discussions about the process and field trips to where the fertilizer was produced helped them overcome them. he said, but noted that farmers may have a hard time convincing customers.

Fertilizer made from recycled human waste could have a serious impact on fertilizer shortages, if people could be convinced to overcome their own squeamishness. of available nitrogen, says Wilde.