Bioponica has found that the use of urine as a plant fertilizer in soilless systems, aka peeponics, is highly effective, as proven by the performance of tomato plants raised in a Biogarden in 2014, entirely from human urine fertilizer.
Most gardeners are familiar with the use of fish urine fertilizer with aquaponics. The logic is straight forward. Urine contains high percentage of ammonia plus phosphorus and trace minerals. With but a little biofiltration, urine is converted to a more plant available nitrate with NPK values that rival other fertilizers such as chicken feathers and cotton seed meal. In fact, the range of NPK from a liquid urine fertilizer is in the range of 10-18/1-2.5/1.
Food consists of nutrients that are high in protein and various forms of nitrogen, phsophorus and potassium. While the feces contains some of this NPK, most ends up in the urine. So, while the logic of recycing manure is sound for the additional fiber and cellulose that ends up in the compost, it falls significantly short of capturing the most important elements of NPK.
Considering the massive amount of urine excreted by 7 billion people on a daily basis it’s a wonder this source of urine fertilizer has not been capitalized on more widely.
I had the opportunity to visit the non-profit, university based organization ECOSANS on a trip to Sweden a few years ago. Their work was brought to my attention by a UN FAO publication that outlined the steps recommended for handling urine in developing nations agriculture.
Another good use from human urine is the production of struvite. This is a phosphorus compound that can be dried, stored and applied to soil as a self sufficient, sustainable method of sourcing phosphorus. Considering we are near “peak phosphorus” this is no insignificant matter.
Because urine is typically low in minerals, a good means of bringing the NPK values closer to the needs of heavy feeding plants is the addition of wood ash. Wood ash is high in calcium, magnesium and potassium.
Urine and wood ash, two abundant waste products that give us all the NPK the planet could possibly need.