Many gardeners are interested in providing for themselves and living off their own skills and the land. To cultivate a successful garden, we often need to add additional inputs such as compost and fertilizers to keep up with the needs of soil nutrients for growing crops. Store-bought fertilizers and fertilizers often contain waste products from other animals such as worms, chickens, and even bats. What if we could produce our own endless and free supply using our urine as fertilizer?
The main components of commercial fertilizers, nitrogen, phosphorus and potassium, as well as micronutrients, are produced by the human body. In fact, long before modern chemical fertilizers were invented, humans used pee as a fertilizer. Urine is the original and free liquid gold.
According to the Stockholm Environment Institute, a person can produce as much urine per year to fertilize 300-400 square meters, or roughly 3200-4300 square feet of plants! Used at the household level, the urine a family produces is more than enough to sustain a home garden. If implemented across the board, the use of human urine could address both hygiene and food security issues around the world.
Why is pee used as fertilizer?
Using urine as a fertilizer may sound strange, but it is very effective. Source: Sustainable sanitation
In modern society we are used to our waste products being washed away and processed in sewage treatment plants. If you find the idea of using urine in the garden off-putting, it may help to know that urine was used for many purposes in the past. From softening leather to bleaching clothing, urine and other body waste have been valued commodities for many cultures around the world since ancient times.
What's in the urine?
Urine is a liquid waste product created by our kidneys cleaning and filtering our blood. Typically, urine contains around 95% water and the remainder is a mixture of salts such as sodium, potassium and chloride, urea and uric acid. Due to the high water content in pee, the more you drink, the more you have to go. For a healthy person, human urine typically has a pH of about 6.2 with a range of 5.5 to 7.0. A person's diet and alcohol consumption can also affect the pH of their urine.
The main organic component of urine is urea, a combination of ammonia and carbon dioxide that is our body's byproduct of breaking down proteins into usable amino acids. Urea is very rich in nitrogen, an important component for healthy leaf growth in plants. Not only is urine very rich in nitrogen, it also contains dissolved phosphorus, which is immediately available to plants, making urine a fast-acting fertilizer.
Social and Environmental Benefits of Using Urine
The environmental impact of the manufacture and use of chemical fertilizers is well documented. For example, phosphorus, an important component of commercial fertilizers, is normally degraded and is a finite resource. It has also been shown that using too much fertilizer that drains into the local water catchment area leads to algal blooms and dead zones in the water system.
In 2014, the city of Amsterdam launched a campaign to raise awareness of the phosphorus shortage by installing public urinals and educating the public about reusing urine as plant fertilizer. In parts of the world where chemical fertilizers are unaffordable, it is even more important to be able to recycle nutrients and use this free resource to create a closed system that turns waste into treasure. Using this free resource could help farmers increase their yields and address some of the global food insecurity challenge.
Is It Safe To Use Urine As A Fertilizer?
A sample of unfertilized basil next to one fertilized with urine. Source: Sustainable sanitation
If you own a dog, you may be familiar with yellow spots on your lawn where your pet peed. Dogs and cats excrete fresh urine with a higher amount of urea than humans, which can more easily burn a plant on contact. For the purposes of this article, we will look at human urine, which has less urea and therefore less ammonia.
Although Bear Grylls drinks urine on its popular survival shows, urine is not sterile. It picks up traces of bacteria when the sterile version passes through the bladder and urinary tract and comes into contact with the skin. Nonetheless, the health risks associated with using urine are very small, as urine typically does not contain any pathogens found in feces. Infectious diseases such as cholera are spread through water sources contaminated with feces. In areas with poor sanitation, there is no way to separate solid and liquid waste, so any untreated mixed sewage can pose significant public health risks.
When not to pee
For garden use, the health of the urine-producing person is important. If you are taking medication or having hormonal treatment, your urine is likely to contain chemical or hormonal residues. In this case, it is best not to use your urine as a fertilizer, as these micropollutants can be absorbed by plants and affect the microbial activity in the soil. In the same vein, it's best not to use your urine if you have a urinary tract infection, typically caused by bacteria including E. coli.
Urine naturally contains salt and the amount can vary depending on a person's diet. The use of urine in arid areas can lead to salinization of the soil and should be carefully monitored. Different plants have different tolerances to salt in the soil, but an excessive concentration of salt can affect the health and growth of the plants. For example, vegetables like potatoes and onions are very sensitive to salt, while olives and barley are tolerant. Some leafy vegetables like kale and are moderately tolerant.
How urine can be used as fertilizer
Keep urine in a completely sealed container. Source: Sustainable sanitation
Researchers around the world have tested the effects of urine on plant growth and production. Positive results have been documented for cereals in Europe and Africa, cabbage and spinach in South Africa, and bananas in India, to name a few. There is strong evidence in the literature and field research to support the use of urine to promote healthy plant growth.
There are a few rules of thumb when it comes to using pee in the garden. Keep or handle urine in a closed container and apply it directly to the soil rather than to plants. Creating a foliar spray is not recommended. Young plants tend to need more nutrients as they grow, and the time lag between fertilization and harvest can further help reduce health risks, especially if the plant is to be eaten raw.
Dilute urine with water or apply undiluted. Many of the papers mentioned above used a thinned version. There are variations of the dilution from 1: 1 to 1:15, with the most common formula being 1: 3. Add water to dilute the urine as close to application time as possible to ensure the solution is not harboring mosquitos. Applying urine near the bottom, pouring it, or using a thinner can help against the odor.
You may have heard of using blood meal as a compost activator to quickly heat up your pile. Blood meal is high in nitrogen, which is why it is a first choice. The same goes for urine. Adding pee to your compost pile or bale of straw can help kickstart an otherwise slow composting process.
Nepal is one of the countries with a long history of using urine to improve soil nutrients for agriculture. According to Nepal's Central Horticulture Center, urine should be kept in an airtight container for at least two weeks to a month and mixed with compost before use. Similarly, a 2020 study published by the University of Michigan found that aging human urine in sealed containers for several months may further reduce the risks of using urine as a fertilizer. This university study tested urine stored for 12-16 months and found that ammonia levels increased over time, killing most of the bacteria in fresh urine.
frequently asked Questions
Another comparison of urine fertilization with basil vs. no fertilization. Source: Sustainable sanitation
Q: is urine good for the garden?
A: Urine contains many nutrients that are beneficial for plant growth, such as nitrogen, phosphorus, and potassium. Many cultures around the world have traditionally used pee as a fertilizer, and many modern researchers have found similar results in field trials with cereals, leafy vegetables, and fruits. Urine is a free and sustainable source of nutrients that is suitable for both agriculture and the household.
Q: Does human urine kill plants?
A: All fertilizers, including human urine, should be used in moderation. Just as using too much chemical fertilizer can burn plants, using too much urine can damage plants by causing nutrient burns. To reduce the likelihood of urine killing plants, urine should be applied to the soil at the base of the plant rather than directly to the foliage.
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