Fertilizers containing human waste could combat global warming

By Mark Waghorn via SWNS

Fertilizers containing human waste could combat global warming, according to new research.

Recycling pee and poop is safe and effective - and provide excellent alternatives, said scientists.

And our toilets may become 'manufacturing plants' for the agricultural industry, according to German researchers.

Producing traditional fertilizers is energy-intensive, resulting in significant carbon dioxide (CO2) emissions.

Franziska Hafner, a Ph.D. student at the University of Hohenheim, Stuttgart, and a first author of the study, said: “Here we show that products derived from recycling human urine and feces are viable and safe with nitrogen fertilizers for cabbage cultivation.

"The fertilizers from nitrified human urine gave similar yields as a conventional product, and did not show any risk regarding the transmission of pathogens or pharmaceuticals.

"The combined application of nitrified urine fertilizers and fecal compost led to slightly lower crop yields, but may increase soil carbon content in the long term, promoting climate-resilient food production."

Greener fertilizers will also bring down prices. They soared over 300 percent last year because of the war in Ukraine.

Ms. Hafner and colleagues compared the marketable crop yield of white cabbage grown between June and October 2019 at the Leibniz Institute of Vegetable and Ornamental Crops.

Plots were filled with sandy, loamy, or silty soil enriched with four recycled fertilizers, applied gradually over the growing season.

The benchmark was commercially available organic vinasse, produced through the fermentation of biomass residues from bioethanol production.

They also tested two 'nitrified urine fertilizers' (NUFs) synthesized from human urine collected separately from feces.

Nitrogen-bearing compounds are converted by microbes into valuable ammonium and nitrate.

The first was Aurin, recently approved for use in human agriculture in Switzerland, Liechtenstein and Austria.

The other was CROP (combined regenerative organic food production), developed by the Institute of Aerospace Medicine of the German Aerospace Center to recycle wastewater on Moon or Mars bases.

Effects of the NUFs on cabbage growth were tested both when applied separately to the soil, or in combination with fecal compost, recycled from dry toilets.

The marketable yield, defined as the parts of the cabbages that can be sold, ranged from 35 to 72 metric tons per hectare.

This yield was highest for plots fertilized by Aurin, CROP, or vinasse. The best results were on sand followed by silt and loam.

The results indicate that soils fertilized with NUFs are as productive as those supplied with widely used commercial vinasse.

Screening for the presence of 310 chemicals in the fecal compost found only 6.5% of them were present above the limit of detection in the compost.

Only the painkiller ibuprofen and the anticonvulsant and mood-stabilizing drug carbamazepine were detectable in the edible parts of the cabbages - at markedly low concentrations.

More than half a million cabbage heads would need to be eaten to accumulate a dose equivalent to one carbamazepine pill.

Ms. Hafner said: "In general, the risk for human health of pharmaceutical compounds entering the food system by means of fecal compost use, seems low."

Around the world, prices of fertilizers have been breaking records over the past year, amidst extreme weather, transport disruptions, and now the Russian invasion of Ukraine.

Russia, which is contending with Western sanctions, produces large quantities of key chemicals used in the production of fertilizers.

It also supplies much of the natural gas used to produce ammonia - a major component of nitrogen fertilizers.

The conflict is making other countries aware of their dependency on Russia for fertilizer.

The US government has responded by investing in innovative, domestically made fertilizers, but it will take time for those investments to pay off.

Soaring prices are causing farmers to adjust their planting strategies. They're also driving interest in alternatives.

Lead author Dr. Ariane Krause, of the Leibniz Institute of Vegetable and Ornamental Crops, said: "Our study results demonstrate that nitrified urine fertilizers such as Aurin and CROP have a huge potential as fertilizer in agriculture.

"If correctly prepared and quality-controlled, up to 25% of conventional synthetic mineral fertilizers in Germany could be replaced by recycling fertilizers from human urine and feces.

"Combined with an agricultural transition involving the reduction of livestock farming and plant cultivation for fodder, even less synthetic fertilizer would be necessary, resulting for example in lower consumption of fossil natural gas."

The study was published in the journal Frontiers in Environmental Science.