Pee Power! Recycling Urine to Powder Makes Superior Fertilizer

Pee Separation For Recycling photo
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"Night soil" has for centuries been the fertilizer of choice for healthy gardens, and at TreeHugger we've tried all the bad puns there are when writing about the art of utilizing urine for garden fertilizing. Why are we so obsessed? Well, the Western penchant for flushing away the poo and the pee is an expensive and wasteful proposition. It can also be downright scary to think of someone else's antibiotics and Viagra eventually ending up back in our water supply. That's why Gothenburg researcher Zsofia Ganrot's new method of powdering pee (which also removes traces of pharmaceuticals) is such a great idea.500 liters of urine a year, 500 liters a year
Amazingly, each one of us contributes about 7-9 liters of urine a week to sanitary systems (minus amounts from boys and men with a thing for urination "au naturel"). In Sweden alone, collection of this resource could offset 1/5th the country's fertilizer use, according to Ganrot. Plus, she says, reduce pollution from the transport of liquid fertilizer.

Cure the urine or add MgO to get the precious white powder
Just letting urine sit for about 6 months will cause the formation of crystals that contain most of the nourishing minerals in the liquid. To speed things up, Ganrot's technique consists of adding magnesium oxide to liquid urine, which causes crystals to form quickly and drop to the bottom of any collection device. When zeolite is added, the crystals retain 70 to 80% of their nitrogen. The crystals are then dried to a white powder called struvite that can then be used for plant fertilization, and Ganrot says her trial tests show the powdered struvite works as well or better than commercial fertilizers (the powdered form helps it stay longer in the soil). It also is devoid of pharmaceutical leftovers, which remain in the separated liquid instead of in the powder spread on fields.

Urine recycling will be big?
Ganrot will now start a pilot at a farm in southern Sweden to collect animal urine and convert it to struvite fertilizer. She says the method is not particularly expensive or difficult, and could be adapter to smaller scales, such as households, as well as for use at existing sewage treatment plants. Separated toilets that divert urine from other waste are a Swedish specialty, but Ganrot hasn't yet outlined how a home toilet could be adapted to become a mini-fertilizer production unit. Via: MiljöAktuellt (Swedish)