How To Safely Use Urine As A Fertilizer

by GardenAdvice · Published 13/09/2022 · Updated 16/09/2022

Chances are – if you’re a gardener, then you’re always looking for better ways to make your garden thrive. And if you’re environmentally conscious, then you’re always looking for impactful ways to reduce your effects on our ecosystem. So if you’re both, just hear me out…

If I were to tell you about a sustainable farming practice that’s not only scientifically backed to increase plant production, but also conserve water, minimize waste, and uses a natural fertilizer that’s readily available to anyone, anywhere in the world. You’d give it a go, right?

Now what if I told you that that fertilizer is actually human urine. Well, guess what? It’s true – urine is a great, all-natural fertilizer. And although many people these days might cringe at the idea, it’s actually been used for centuries throughout all corners of the world. But before you start peeing on your plants (and harm your garden), there are some key insights you need to consider before using urine as fertilizer.

In this article, we’ll dig into the many benefits of using urine as a fertilizer and show you how to properly and safely make the switch. So if you’re ready to learn more about this sustainable farming practice, then let’s get started!

Reimagining Our Liquid Waste As a Valuable Resource

Fact is, regardless of the gross-out factor, humans have been using urine as fertilizer long before the invention of modern chemical fertilizers. And for good reason, urine contains a wonderful bounty of nitrogen, potassium, phosphorus, calcium, magnesium, and sulfur — the key nutrients plants need to thrive and the main ingredients in common mineral fertilizers.

Plus, the average adult living on a typical Western diet urinates about 500 liters a year, enough to fill three standard bathtubs! So with a steady stream of this man-made plant food readily available to most of the world, recycling urine into fertilizer is a great, cost-effective way for gardeners to minimize their reliance on chemical fertilizers and be more self-sufficient in the process.

What Would Recycling Urine as a Fertilizer

Do for Our Ecosystem?

Urine, as we mentioned above, has lots of nitrogen and phosphorus — great as fertilizer, but a big problem as far as waste goes. In excess, nitrogen and phosphorus in our wastewater can stimulate algal blooms, create conditions dangerous to marine ecosystems, lake ecosystems, human health, and even threaten global food security.

What happens when we flush the toilet? When we flush urine into sewers its fertilizing potential ends up in the wrong places, with severe environmental consequences. But if we collect urine for recycling we can put it on farms and gardens where its fertilizer value is hugely beneficial, supporting the agricultural systems we all depend on.

Research shows that removing urine from wastewater and using it as fertilizer has the massive potential to:

● Decrease nutrient loading in water bodies

● Boost sustainability by making use of a common waste material

● Make agriculture & wastewater treatment more sustainable in industrialized countries

● Improve sanitation in developing countries

All of that on top of bolstering plant production, seems like a no-brainer right?

So instead of flushing these precious elements downstream, where they cause nutrient pollution and harmful algal blooms, we can reclaim these nutrients to grow gorgeous crops!

Urine is commonly and very successfully used to grow countless types of plants/produce including, but not limited to; cabbage plants, spinach, geraniums, cloves, peas, tomatoes, radishes, primroses, begonias, beets, as well as, most types of fruit.

How Can You Make the Switch Today?

Here’s 3 Steps to Get Started…

Step 1: Collect

Collect your urine in a sealable, watertight container OR in a composting toilet. Note: if you’re using a composting toilet, make sure not to let any solid waste mix with the urine. Tip: There are many different manufacturers for composting toilets like kildwick.com.

Step 2: Sanitize (if needed)

Will anyone outside your household eat your garden’s harvest? If so, then sanitation is recommended. In order to assure that your urine is properly sanitized: simply store the urine in an airtight container at 68°F (20°C) or higher for at least 2-4 weeks.

If you’re not planning on sharing your harvest with anyone outside of your household, then sanitizing is not necessary. Many people use urine in their home gardens without any treatment. The World Health Organization supports this practice if the urine comes from the same household that will be eating the produce, AND if the following guidelines are followed:

1. Wash hands after handling urine, or wear gloves.

2. Follow best practices for application (e.g. applying only to soil, diluting properly, etc.)

3. Wait at least one month after fertilization to harvest crops that you’ll eat raw.

Odor tip: Minimize odors by adding white vinegar or citric acid to the urine collection container before any urine is added. We use 1-2 cups of white vinegar or 1 tablespoon of citric acid per 5-gallon container. This also helps reduce nitrogen loss (via ammonia volatilization) during short-term storage.

Step 3: Fertilize!

How much do you need?

If you don’t apply enough fertilizer, your crops won’t receive enough nutrients and won’t grow as well as they would’ve. If you apply too much, the excess nutrients can run off and cause water pollution.

To avoid over-applying, make sure you don’t add more nutrients (especially nitrogen and phosphorus) than your crops can handle. To do this, you’ll need to consider your plant’s needs, the nutrients already in the soil, and how often you will apply.

Most gardeners apply whenever it looks like their plants are growing slowly or turning yellow, as these are telltale signs of inadequate nitrogen. A rough guideline is to apply roughly 1 gallon of urine per 100 square feet every couple of weeks.

When is the best time to apply?

Apply when your plants are actively growing. The best time varies by crop, but it’s generally after germination and before fruits/seeds appear.

Note: In principle, fertilization of freshly consumable fruits or vegetables should be avoided. Also, young plants (seedlings), ferns, azaleas, orchids, and bromeliads should never be fertilized with urine.

What about composting?

Composting may be a good solution if you don’t have enough space for storage or if you prefer to handle it as compost. Adding urine to a compost pile also accelerates the composting process. If you choose to compost urine, adding high-carbon materials such as dead leaves, straw, paper, or sawdust will help secure even more of the nutrients.

This option also allows you to collect using a compost toilet, with great choices from companies such as Kildwick compost toilets.

Should you dilute it?

If you follow the recommendations here and apply the right amount, undiluted urine will not harm your plants. However, dilution can be beneficial because it helps the urine soak into the ground, especially in dry soil.

There is no standard urine:water dilution ratio. Some reputable sources recommend anywhere ranging from 1:1 to 1:30. However, somewhere between 1:3 to 1:5 range does so happen to be the most common.

When Is It Unsafe to Use Urine for Fertilizer?

Keep in mind, the health/diet of the person producing the urine may have effects on your garden. For example, if you are taking medication or undergoing hormone treatment, your urine will likely contain chemical or hormonal residues. It’s best in this case to avoid using your urine since these micro-pollutants may become absorbed by plants and have a negative impact on the microbial activity of the soil.

Furthermore, urine naturally contains salt and the amount can vary depending on a person’s diet. 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 such as potatoes & onions are very salt-sensitive whereas olives & barley are much more tolerant.

Are You Saying Solid Waste Goes in the Garden Too? What About Pathogens?

There are a lot of benefits to composting solid waste, including reducing the amount of methane produced in landfills and improving soil health. However, there are also some potential risks associated with composting solid waste improperly. For example, if solid waste is not composted properly, it can release harmful pathogens into the environment. Using a compost toilet is one way to reduce the release of harmful pathogens into our ecosystems.

Urine and solid waste are two of the most commonly composted materials in the garden. However, it’s important to note that while compost toilets can help to reduce the risk of pathogen exposure, it is important to never mix urine with solid waste while composting and to always manufacture them separately.

Sources:

● https://arstechnica.com/science/2022/08/should-we-be-trying-to-create-a-circular-urine-economy/

● https://www.kildwick.com/en/discover/good-to-know/use-of-urine-in-the-garden

● https://www.kildwick.com/en/discover/good-to-know/composting-of-faecal-matter

● https://www.eawag.ch/en/department/eng/projects/vuna

● https://vuna.ch/en/urin-recycling-technologie/

● https://www.scientificamerican.com/article/human-urine-is-an-effective-fertilizer/

● https://www.heise.de/hintergrund/Geruchsloser-Duenger-aus-Urin-2639811.html

● https://www.epicgardening.com/urine-as-fertilizer/

● https://kommunen-innovativ.de/zirkulierbar

● https://richearthinstitute.org/get-involved/fertilize-with-urine/

● https://richearthinstitute.org/rethinking-urine/