New Finnish study: human urine is a good fertilizer

A “U” professor said people have fertilized with urine for about 6,000 years.

Devin Henry

A research team from Finland confirmed the effectiveness of an inexpensive, organic and abundant fertilizer – human urine.

In a study scheduled to be published in late October, researchers took human urine samples and used them to fertilize cabbage plants. The study found the urine-fertilized plants grew slightly larger than the cabbage that took conventional fertilizer.

Tom Halbach, a professor in the University department of soil, water and climate, said people have used urine as fertilizer for about 6,000 years, but it’s not commonly used.

Daniel Kaiser, an assistant professor in soil, water and climate, said he hasn’t directly researched urine’s use in fertilization, but understands the basis of the research.

Kaiser, who mostly studies manure as fertilizer, said organic chemicals found in urine, such as nitrogen, can be good fertilizers.

“A lot of the nitrogen in manure is coming from uric acid,” he said. “The uric acid will be converted over to nitrogen, so over time it should be like any other fertilizer source.”

Uric acid is a component of urine, and Kaiser said even though it came from manure in his studies, it’s the same uric acid that’s found in urine.

Kaiser said conventional fertilizer research focuses on manure and types of fertilizer that time-release nitrogen into soil, ensuring the crops are supplied with nutrients throughout the entire growing season.

Kenneth Smith, a urology resident at the University’s medical school, said he doesn’t agree with urine’s use as a fertilizer.

“You could wrap your head around maybe, that there is nitrogen in urine, and there is nitrogen in fertilizer, therefore, urine is fertilizer,” he said. “I don’t think that ‘calculus of nitrogen’ actually works.”

The Finland study found no health or taste side effects associated with the urine-fertilized cabbage. Smith said healthy people generally produce urine that is sterile, so consuming urine doesn’t cause any major health problems.

However, if a person drank human urine over an extended period of time, Smith said, waste materials would build up in the body.

“We don’t run into a lot of people who drink their own urine,” he said.

Halbach said the nitrogen in urine has little effect on humans, but that an excess of fertilizer, whether organic, like urine, or chemically based, can harm the environment.

Issues associated with over- fertilizing include increased growth of algae and, in extreme cases, the reduction of oxygen in lakes, Halbach said. This can have a serious effect on the fish population, he said.

“The trick in agriculture is to provide enough for the plants so they grow and are healthy, but not too much that you cause unintended environmental damage,” he said. “The trick is enough but not too much. That is true of any fertilizer.”