Human waste is safe for vegetable growing, researchers say

Governments around the world are struggling to contain fertilizer costs and improve self-sufficiency after Russia’s invasion of Ukraine has pushed up prices for natural gas, a key feedstock for fertilizers.

European Union authorities are considering ways to speed up the development of manure-based fertilizers after the cost hike sparked fury among the bloc’s farmers.

In terms of safety, the researchers examined human excreta for 310 chemicals, ranging from pharmaceuticals to insect repellents, and found that only 6.5% of them were above the detection limit and at low levels.

“In general, the human health risk of pharmaceutical compounds entering the food system through the use of fecal compost appears to be low,” the authors concluded.

While they were able to detect two pharmaceutical products, the pain reliever ibuprofen and the anticonvulsant carbamazepine, in edible parts of cabbage, the concentrations were strikingly low. That means more than half a million cabbages would have to be eaten to accumulate a dose equivalent to a carbamazepine pill, they said.

The increase in fertilizer costs following the Russian invasion already prompted some farmers to turn to animal manure and even human sewage to replace synthetic plant nutrients, but these alternatives had not proven as effective.

However, this study suggests that some products processed from human waste may approach the efficiency of man-made alternatives.

“With the right processing and quality control, up to 25 percent of the conventional synthetic mineral fertilizers in Germany could be replaced by recycled fertilizers made from human urine and faeces,” says first author Ariane Krause.

Bloomberg