Urine As Fertilizer: Does It Work?

To cultivate a successful garden, we often need to include additional inputs like compost and fertilizers to boost nutrients. Store-bought fertilizers often contain waste products from other animals like worms, chickens, and even bats.  But what if we can produce our own endless and free supply?

Some of the main components in commercial fertilizers (nitrogen, phosphorus, potassium, and micronutrients) are produced by the human body in urine. In fact, humans have been using pee as fertilizer long before the invention of modern chemical fertilizers. 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 roughly 3200-4300 square feet of crops! Used at a household level, the urine that a family produces is more than enough to help sustain a home garden. If adopted at scale, capitalizing on human urine could tackle both sanitation and food security challenges around the world. 

Why Is Pee Used As Fertilizer?

If the idea of using urine in the garden grosses you out, maybe it helps to know that urine has been historically used for many purposes.

From softening leathers to bleaching clothes, urine and bodily waste have been used since antiquity in many cultures around the world. We are just accustomed to our waste products being flushed away and processed at wastewater treatment plants.

What Is In Urine

Urine is a liquid waste product that is produced by our kidneys by cleaning and filtering our blood. Typically, urine contains around 95% water. The rest is a mix of salts including 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 around 6.2 with a range of 5.5-7.0. 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, which is the byproduct of our bodies breaking down proteins into usable amino acids.

Urea is very high in nitrogen, a key ingredient to healthy leafy growth in plants. Urine also contains dissolved phosphorus that is immediately available to plants, making urine a quick-acting fertilizer.

Social and Environmental Benefits

The environmental impact of producing and using chemical fertilizer has been well documented. For example, phosphorus, a key ingredient in commercial fertilizers, is typically mined and is a limited resource. Using too much fertilizer that runs off into the local watershed has also been shown to cause algal blooms and dead zones in the water system. 

In 2014, the city of Amsterdam launched a campaign to raise awareness of phosphorus shortage by setting up public urinals and educating the public on repurposing pee as a plant fertilizer.

In parts of the world where chemical fertilizers are cost-prohibitive, it’s even more important to be able to recycle nutrients and create a closed-loop system using this free resource, thus converting waste into treasure. Tapping into this free resource could help farmers increase their yields and address a piece of the global food insecurity challenge. 

Is It Safe To Use Urine As A Fertilizer?

If you own a dog, you may be familiar with yellow patches on your lawn where your pet has peed. Dogs and cats excrete fresh urine with a higher quantity of urea than humans do. That can easily burn a plant upon contact. But we are discussing human urine, which contains less urea and thus less ammonia. 

Urine is not sterile. It picks up trace amounts of bacteria as the sterile version passes through the bladder, the urinary tract, and comes in contact with the skin.

Still, the health risks of using urine are very low because urine does not typically contain pathogens found in feces. Infectious diseases like cholera are spread through water sources contaminated by poop. In areas with poor sanitation, there is no way to separate solid and liquid waste which is why all untreated mixed sewage can pose significant public health risks.  

When Not To Use Urine

The health of the person producing urine does matter for use in the garden.

If you are taking medication or undergoing hormone treatment, your urine will likely contain chemical or hormonal residues. It is best in that case not to use your urine as fertilizer. The micro-pollutants can be taken up by plants and may negatively impact microbial activity in the soil.

In the same vein, it’s best not to use your urine if you are experiencing a urinary tract infection, which is typically caused by bacteria including E.coli. 

Urine naturally contains salt. The amount varies depending on a person’s diet. Urine use in arid areas could cause salinization of the soil and should be carefully monitored.

Different plants have different tolerances to salt in the soil, but an excess concentration of salt could adversely impact plant health and growth. For example, vegetables like potatoes and onions are salt-sensitive whereas olives and barley are tolerant. Some leafy greens like kale are moderately tolerant. 

How To Use Urine As A Fertilizer

Researchers around the world have been testing the effect of urine on plant growth and production. There is strong evidence 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. Store or handle urine in a closed container, and apply it directly to the soil instead of on plants. Creating a foliar spray is not recommended. 

Space out the timing between applying the fertilizer to harvesting. This will decrease health risks, especially if the crop is to be consumed raw. 

Dilute urine with water or apply as an undiluted solution. Researchers often use a diluted version. There are variations to dilution from 1:1 to 1:15 with the most common formula being 1:3.

Add water to dilute urine as close to the application time as possible to ensure the solution will not harbor mosquitos. Apply close to the soil and water it in or use a dilution to help with the smell. 

You may have heard about using blood meal as a compost activator to heat up your pile quickly. Blood meal is high in nitrogen which is why it’s a go-to choice. The same can also be said for urine. Adding pee to your compost pile or strawbale can help kickstart an otherwise slow composting process. 

Aging Urine As Fertilizer

Nepal is one of the countries with a long history of using urine to improve soil nutrients for farming. According to Nepal’s Central Horticulture Center, urine should be stored in an airtight container for at least two weeks to a month and mixed with compost before use.

Similarly, in a 2020 study published by the University of Michigan, the research found that aging human urine in sealed containers over several months can further decrease the risks of using pee as fertilizer. This university study tested urine stored for 12-16 months and found that ammonia levels increased over time and killed most bacteria found in fresh urine. 

Frequently Asked Questions