Is it safe to eat cabbage grown in “composted human feces”?
In the 2015 film The Martian, Matt Damon manages to survive on Mars after using his feces as fertilizer to grow potatoes.
Such a thing may seem far-fetched or even unnecessary here on Earth, but a new study has found that cabbage made from human feces compost is safe to eat.
This discovery could be a game-changer because while modern fertilizers might seem good to deal with the climate crisis, biodiversity loss and pollution, humanity will need to move on to a more recyclable existence.
That’s why scientists question the benefits of the nutrient-rich fertilizers people bury in our oceans and landfills when they can be easily put back into the soil.
Composting instead of throwing it away will reduce water use, and adding it to the ground will also reduce the need for synthetic fertilizers, which can be washed off fields into rivers and lakes and require fossil fuels to produce.
One method of making them, known as the Haber-Bosch process, is responsible for about 1.8% of global carbon dioxide emissions.
Thus, human fertilizers certainly have their advantages if there is no risk that harmful microbes or drug traces can enter crops, as confirmed by the University of Hohenheim in Stuttgart, and study author Franziska Haffner said: obtained from recycled circulating human urine and faeces, are safe and effective nitrogen fertilizers for cabbage cultivation. The combined application of nitrogen in urine and faecal manure slightly reduced crop yields, but in the long term may increase soil carbon content, stimulating climate-resilient food production.”
Most of the nutrients needed for plant growth are found in human urine and faeces, with nitrogen and potassium present in urine, as well as trace amounts of minerals such as boron, zinc, and iron, as well as phosphorus, calcium, magnesium, and organic carbon in faeces. .
In their study, doctoral student Hafner and her colleagues compared the yields of white cabbage grown between June and October 2019 at the Leibniz Vegetable Institute.
The soil was enriched with four recycled fertilizers applied gradually over the growing season, and commercially available organic wine was used as a benchmark against which to compare human urine and feces.
Two so-called “urea nitrogen fertilizers” (NUFs) were also tested, which are new products made from human urine collected separately from faeces, in which nitrogen-containing compounds are converted by microbes into valuable ammonium and nitrates.
Finally, fecal manure recycled from dry toilets was used, with or without NUF mixing.
Marketable yields, defined as the fraction of cabbage that can be sold, range from 35 to 72 metric tons per hectare.
It was highest for lands fertilized with NVF and vinasse, and lowest for lands fertilized with faecal manure only.
And somewhere in between was faecal compost combined with NUF.
The researchers say their results show that soils enriched with non-systemic nutrients are just as productive as those supplied with widely used commercial wine.
In the study, they also examined the presence of 310 chemicals in fecal manure, from pharmaceuticals to rubber additives, flame retardants, UV filters, corrosion inhibitors and insect repellents. Only 6.5% of these were present in the compost above the detection limit, albeit at low concentrations.
Only the pain reliever ibuprofen, the anticonvulsant and the mood-stabilizing drug carbamazepine were found in low concentrations in the edible parts of the cabbage.
That means you need to eat more than half a million cabbages to accumulate the equivalent dose of one carbamazepine, the researchers say.
Along with the agricultural transition, which involves reducing the number of livestock and growing forage crops, it will be necessary to reduce the use of synthetic fertilizers, which will lead, for example, to a reduction in the consumption of fossil natural gas.
The study is published in the journal Frontiers.
Source: Daily Mail