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[[Image:Struvite.jpg|thumb|right|150px|A jar of Struvite]]
Urine is often used as a liquid fertilizer in rural areas due to its highly concentrated nutrient content. The main minerals required by plants are nitrogen, potassium and phosphorus. Urine contains roughly 80% of the nitrogen, 60% of the potassium and 55% of the phosphorus that humans excrete. While nitrogen is relatively easy to obtain from other sources, potassium and phosphorus are more scarce. The only readily available organic source of these is urine. However [[application Application of urineUrine]] is often unwanted since it is required in large volumes, is inconvenient to transport and has a bad odor. Also it cannot be applied through irrigation systems.
When urine is stored, a spontaneous reaction occurs, forming the precipitate: magnesium ammonium phosphate also known as struvite. However only 30-50% of the phosphate precipitates naturally. By reacting the urine with magnesium, over 90% of the phosphorus can be recovered. This can be filtered out and dried to produce a valuable powder fertilizer. The remaining effluent contains most of the urine’s nitrogen and potassium. Since there are no precipitates and can be applied to crops through irrigation systems.