Urine is an exceptionally valuable source of nutrients. By comparison to manures, urine is an ideal source of ammonia-nitrogen which is a plant ready source of fertilizer. While there are issues related to medicines consumed, elevated levels of sodium and fecal cross contamination, urine is typically sterile and when stored for a specified period in a concentrated form, the ammonia level is so high, it is generally safe to assume there are no viable pathogens present, even when collected from toilets that are divided for solid/liquid waste streams. A latrine or hand held collection device is less likely to have cross contaminants.
When using urine as a fertilizer it may either be diluted and added directly to the soil or hydroponic growing systems or it may be biofiltered to lower ammonia. However, unless there are aquatic organisms in the system that are sensitive to ammonia, plants typically thrive with ammonia rich nitrogen fertilizers. Urine does not contain carbon and so is not literally “organic” though one would have a difficult time arguing it is “inorganic.” Technically though the ammonia/urea is not bound to carbon, as carbon is removed in the digestive tract and through the urea energy production cycle of the animal, prior to urine filtration through the kidneys.
Human urine in hydroponic systems is roughly equivalent to aquaponics, without the fish. The fish perform a similar task as does the human or animal body. After consuming foods, urea is produced by the kidneys which breaks down into ammonia. Solid waste is evacuated as a low nitrogen containing manure. Liquid, being in a relatively plant-ready form is ideal as it is relatively identical to fish waste, which similarly releases urea/ammonia in a liquid, plus a relatively unusable solid poop.
Researching alternatives to chemical fertilizers, BIoponica has explored the use of urine as a source of nitrogen in agriculture and hydroponics. The biggest issue we found is that humans, which seems to be the easiest source for collecting urine, typically contains high levels of sodium and medicines, due to the typical human diet, and condition. However, in growing things like duckweed, which is a high protein animal feed, urine is extremely useful and should be considered both as a means of fertilizing a low-tech healthy animal feed and as a way of recycling urine and creating an agricultural biproduct. Duckweed is the ultimate waste treatment “plant”. Urine is very practical for growing duckweed as well as lettuces, when collection of the urine is feasible.
Our preferred method of providing sustainable organic plant fertility is through nutricycling. When taking biomasses before they become urine, or manures, the nutrient content is much greater and useful in agriculture. We produce blends of dehydrated biomasses and convert them into liquid fertilizers that may be used in soils and in hydroponics systems. The process is very low tech and can be implemented worldwide with very little cost. The steps involved in making liquid fertilizer are anaerobic extraction biomass, which can be done in a simple bucket or barrel system. Once the leachate is collected, then the carbon is removed through biofiltration and aeration. We do this with a vortex and a biofilter substrate. The final product, depending on the biomass blends used are ideal for growing plants in all phases of growth. The same setup, sans anaerobic extraction, can be used to nitrify ammonia (nitrification) from urine, into a higher nitrate form of nitrogen.
A few years ago, I had the opportunity to visit the 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. This guide provides examples of how to use urine in soil based agriculture.