Pees and Carrots

Researchers say human urine works great as sustainable fertilizer

July 23, 2010

They were perfectly lovely, the beets Surendra Pradhan and Helvi Heinonen-Tanski grew: round and hefty, a rich burgundy, their flavor sweet and faintly earthy like the dirt from which they came. Unless someone told you, you’d never know the beets were grown with human urine.

Pradhan and Heinonen-Tanski, environmental scientists at the University of Kuopio in Finland, grew the beets as an experiment in sustainable fertilization. They nourished them with a combination of urine and wood ash, which they found worked as well as traditional mineral fertilizer.

“It is totally possible to use human urine as a fertilizer instead of industrial fertilizer,” said Heinonen-Tanski, whose research group has also used urine to cultivate cucumbers, cabbage and tomatoes. Recycling urine as fertilizer could not only make agriculture and wastewater treatment more sustainable in industrialized countries, the researchers say, but also bolster food production and improve sanitation in developing countries.

Urine is chock full of nitrogen, potassium and phosphorus, which are the nutrients plants need to thrive — and the main ingredients in common mineral fertilizers. There is, of course, a steady supply of this man-made plant food: an adult on a typical Western diet urinates about 130 gallons a year, enough to fill three standard bathtubs. And despite the gross-out potential, urine is practically sterile when it leaves the body, Heinonen-Tanski pointed out.

The nutrients in urine are also in just the right form for plants to drink them up, said Håkan Jönsson, a researcher at the Swedish University of Agricultural Sciences in Uppsala who was not involved in the beet study but has researched urine recycling for over 15 years. Food gives us nutrients like nitrogen as parts of complex organic molecules, but our digestive system strips them down into the basic mineral form that plants need — so “we have done half of the job,” Jönsson said.

A small but dedicated contingent of organic gardeners in the United States and Europe already fertilize with urine at home, and researchers in Scandinavia have run pilot projects to recycle locally collected urine on small farms. But urine recycling may never become a part of large-scale farming in industrialized countries, because implementing it would mean drastically remodeling the sewage system in order to collect and transport liquid waste.

It would also mean swapping regular flush toilets for separating toilets, where a divided bowl and independent set of pipes sort the urine out from everything else. This detail is a roadblock, Jönsson said, because many people don’t want a toilet that looks strange. “Acceptance is a big problem for this kind of system.”

For the recent experiment with beets, the urine was obtained from specialized toilets in private homes. Heinonen-Tanski’s group planted four plots of beets and treated one with mineral fertilizer, one with urine and wood ash, one with urine alone, and one with no fertilizer as a control.

After 84 days, about 280 beets were harvested. The beetroots from the urine- and urine-and-ash-fertilized plants were found to be, respectively, 10 percent and 27 percent larger by mass than those grown in mineral fertilizer. By grinding some beets to powder and subjecting them to chemical analysis, the researchers determined that all the beets had comparable nutrient contents — and according to a blind taste-testing panel, the taste was indistinguishable. The results were published in the February 10 issue of the Journal of Agricultural and Food Chemistry.

Effective fertilization isn’t the only benefit of recycling urine, Heinonen-Taski suggested in a review paper in the January 2010 issue of the journal Sustainability. The separating toilets that collect urine use less water than flush toilets, she writes, and the simplified waste stream requires less energy in sewage treatment.

“Agricultural and health organizations should encourage people to use human urine as a fertilizer,” Heinonen-Tanski concluded in that paper, especially in areas where wastewater treatment is unavailable or ineffective.

Though he’s skeptical that it will ever happen on a large scale, Jönsson does practice urine fertilization himself: He and his wife use what they collect from their separating toilet to nourish their garden at home in Sweden. The urine one person produces can fertilize about ten square feet of soil a day, Jönsson said — but there’s been less to go around since his three children left home.

“It’s enough for the vegetables and the flowers,” he said, “but I can only fertilize very lightly on the lawn. Otherwise I run out of urine.”

About the Author

Mara Grunbaum

Mara Grunbaum studied English and environmental science at NYU. Before returning to New York, she worked for several years as a freelance reporter in Portland, Oregon, where she wrote about local politics, poverty and social justice. As a science reporter, she’s most interested in biology, ecology and most anything having to do with the ocean. You can also read her blog or follow her on Twitter.



Adam says:

Interesting, although I feel I compelled to point out that whenever I’m in the garden I just pee on my compost heap. The compost seems pretty effective.

Carrot Juice says:

Ok, So im all about organic. I actually live on a farm, but will never pee in my vege. garden. I understand the sceince behind it, but i must draw a line. There are many other ways to do it organically.

Liz says:

I’m actually intrigued and trying to get my husband to pee on our vegie patch. He’s not that keen unfortunately ;)
Question: won’t it start to smell?

Hendrik says:

Human urine was collected in some Western European cities until the early 20th century and then used as a fertilizer. It is still being done in other parts of the world. See this thoroughly researched article in Dutch: http://www.lowtechmagazine.be/2010/02/kunstmest-landbouw-humanure-compost.html

Uncle B says:

American ignorance and arrogance combined with a heavy handed approach to survival brought on by the WWII victory and the influence of the all powerful atomic bomb notion of invincibility here at home have taken first place over the sensible and practical. We have taken to waste for the sake of convenience and live like royalty – the very folks we emigrated to escape! Slowly the tides of time and economic realities will morph us back to a more realistic society and science with technologies new and old will show the way to a more practical and sustainable life style. We will compost, humanure,and grow gardens or die in the unsusustainable world of supermarkets, factory farmed foods, over weight, and sloth!
The great warriors we once were, those that won WWII were depression hardened individuals, not the great supermarket fed slobs of today!America has withdrawn from Iraq, unvictorious and without great victory marches and celebrations – We in a sense retreated to cut our losses to a worse situation in Afghanistan – not the noble folk who vanquished the Nazi armies but a gang of oil hungry marauders without glory or goals – the over-fed, fat assed supermarket variety American – fatted calf to the world and unsustainable in this world.

james says:

See “Farmers of Forty Centuries” by F. H. King.

It’s laughable that we need university researchers to tell us what we’ve known for millennia.


gaea303 says:

I just started doing this a few days ago and already my lemon bush is much greener and healthier looking! It amazing..

Liam says:

Only danger from this is from ladies using hormonal contraceptives.

These hormones are readily absorbed by the plants any over time would affect those eating them.

Gardenerd says:

My husband pees into our compost bin. Not only does it recycle nutrients back into the system, it helps kick-start the composting process, and you don’t have to worry about the “ick” factor.

marleen says:

Its a well-known old wives’ practice in the Asian world. My mum does it for her citrus plants. She also buries carcasses (e.g. rats) and spread ashes from the fireplace in her veggie patch and egg shells in her flower garden.

You will want to grab an old toothbrush to clean this tube out and remove all of the buildup from the inside of this tube. Breathing in the dust will not be a problem or a concern when the canister and filter are cleaned with care. They came quickly enough-two burly men who would have been a help at installation time.

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