Urine as Fertilizer: Useful or Just Disgusting?

Is human urea suitable for fertilizing plants? Here you can find out what speaks for and against fertilizing with urine.

Four things are essential for a plant to grow: light, water, CO₂ and nutrients. The nutrients include mainly nitrogen, phosphate and potassium. These nutrients are usually made available to the plants on the field in the form of artificial fertilisers. Isn't that more natural? In this article, we address the question of whether our urine is suitable as fertilizer.

Artificial fertilizers require huge amounts of energy, for example to convert nitrogen from the air into a form that plants can use. For this reason, the use of mineral artificial fertilizers is not exactly good for the environment. Of course, the thought of simply feeding our plants human urine doesn't sound particularly appetizing. However, the question is not far-fetched, after all we fertilize our plants with the legacies of birds and cows (guano and liquid manure). Then why not with our urine?

Is human urine suitable as fertilizer?

Human urine has a central task in our body - the elimination of metabolic waste products. Above all, the breakdown products of proteins get out of our body in the form of urea via the urine. Urea is almost 50% nitrogen, making it an extremely concentrated nitrogen fertilizer. Even today's artificial fertilizers cannot keep up.

To illustrate the amount of nitrogen, here is an example: An adult human produces 20 g of urea per day. With this amount, over 3 kg of tomatoes could be produced. Applied to the entire German population and calculated over the whole year, that would be 9 million tons of tomatoes! In addition to the very high nitrogen content, human urine also contains a lot of phosphate, potassium and calcium. If we judge human urine only by the nutrients relevant to plants, diluted it would be a perfect fertilizer.

Dangers of fertilizing with human urine

But unfortunately it is not so easy to fertilize with our urine. Because the use entails many dangers - on the one hand for the fertilized plant, but also for us. First of all, there is a very banal problem: as soon as the urine has left our bladder, millions and millions of bacteria start working on it. Ammonia is released and the pungent, unappetizing smell of urine develops. The assumption that human urine is sterile is also incorrect. If you fertilize with urine, bacteria always get to the fertilized plants. However, we cannot say with certainty whether these bacteria are dangerous.

Of course, drug residues and other unsightly substances can also get into the soil of the fertilized plant with the urine. This can also include table salt, because depending on how we eat, urine can also contain a not inconsiderable amount of salt. As we know, most plants don't like salt at all and die quickly if overdosed. Another important point is the pH of urine. Most plants prefer a pH between 5.5 and 7.0. However, the pH value of our urine can fluctuate greatly between 4.6 and 7.5 (on a daily basis). The pH of 4.6 may appeal to ericaceous plants like this rhododendron, but most other plants will not be able to cope with this pH in the long term.

Urine as fertilizer: Potential for the future

In summary, it can be said that our urine is not necessarily suitable for fertilizing plants permanently. However, the image should not arise that every garden plant dies immediately as soon as someone has relieved it. We see great potential in human urine in the future if the nutrient rich fertilizer is processed prior to use. Germs could be killed and unwanted substances such as table salt can be removed relatively easily. Research is already being carried out into urine treatment plants so that human urine can be used on a large scale as a valuable fertilizer. This could reduce the use of artificial fertilizers, with the result that the environment would be protected overall.

Alternative to urine as fertilizer

Since we cannot currently recommend using your own urine as fertilizer in the garden, we offer an alternative below. Our Plantura organic fertilizer made from primarily organic raw materials provide your plants with long-term and natural nutrients. They are therefore perfect for gardeners with an awareness of sustainability.