Application of Stored Urine

The guidelines for urine use are based on storage time and temperature (see WHO guidelines on excreta use in agriculture for specific requirements). However, it is generally accepted that if urine is stored for at least 1 month, it will be safe for agricultural application at the household level. If urine is used for crops that are eaten by people other than the urine producer, it should be stored beforehand for 6 months.

Another beneficial use of urine is as an additive to enrich compost. Technologies for the production of urine-based fertilizers are currently under research (e.g., struvite, Emerging Sanitation Technologies).

From normal, healthy people, urine is virtually free of pathogens. Urine also contains the majority of nutrients that are excreted by the body. Its composition varies depending on diet, gender, climate, water intake, etc., but roughly 88% of nitrogen, 61% of phosphorus and 74% of potassium excreted from the body is in urine.

Stored urine should not be applied directly to plants because of its high pH and concentrated form. Instead, it can be:

• mixed undiluted into soil before planting;
• poured into furrows, but at a sufficient distance away from the roots of the plants and immediately covered (although this should take place no more than once or twice during the growing season); and
• diluted several times, whereby it can be frequently used around plants (up to two times weekly).

The optimal application rate depends on the nitrogen demand and tolerance of the crop on which it will be used, the nitrogen concentration of the liquid, as well as the rate of ammonia loss during application. As a general rule of thumb, one can assume that 1 m² of cropland can receive 1.5 L of urine per growing season (this quantity corresponds to the daily urine production of one person and to 40-110 kg N/ha). The urine of one person during one year is, thus, sufficient to fertilize 300 to 400 m² of cropland.

A 3:1 mix of water and urine is an effective dilution for vegetables, although the correct amount depends on the soil and the type of vegetables. If diluted urine is used in an irrigation system, it is referred to as “fertigation”. During the rainy season, urine can also be applied directly into small holes near plants; then it is diluted naturally.

Urine poses a minimal risk of infection, especially when it has been stored for an extended period of time. Yet, urine should be carefully handled and should not be applied to crops less than one month before they are harvested. This waiting period is especially important for crops that are consumed raw (refer to WHO guidelines for specific guidance).

Social acceptance may be difficult. Stored urine has a strong smell and some may find it offensive to work with it or to have it nearby. If urine is diluted and/or immediately tilled into the earth, however, its smell can be reduced. The use of urine may be less accepted in urban or peri-urban areas when household gardens are close to peoples’ homes than in rural areas where houses and crop land are kept separate.

Over time, some minerals in urine will precipitate (especially, calcium and magnesium phosphates). Equipment that is used to collect, transport or apply urine (i.e., watering cans with small holes) may become clogged over time. Most deposits can easily be removed with hot water and a bit of acid (vinegar), or in more extreme cases, manually chipped off.