Science

Human urine may be Number 1 for fertilizing plants on Mars

Human urine may be Number 1 fo...
Bean plants grown without the urine-based fertilizer grew no taller than 25 cm (9.8 in)
Bean plants grown without the urine-based fertilizer grew no taller than 25 cm (9.8 in)
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On days without sufficient daylight, grow lamps were switched on
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On days without sufficient daylight, grow lamps were switched on
Bean plants grown without the urine-based fertilizer grew no taller than 25 cm (9.8 in)
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Bean plants grown without the urine-based fertilizer grew no taller than 25 cm (9.8 in)

Shipping fertilizer to colonies on Mars could be quite a hassle – it would certainly be better if the colonists were able to grow crops using whatever's on hand. The continuation of an existing study now indicates that urine might in fact serve as a perfectly good fertilizer.

It was back in 2016 that we first heard how scientists at The Netherlands' Wageningen University were trying to grow food plants in simulations of both lunar and Martian soil. At the time, it was found that while the plants didn't fare well in nothing but the soil, they did better when a fertilizer made of fresh-cut grass was added.

Unfortunately, though, the Red Planet isn't known for its lush lawns – and growing grass in Martian greenhouses would use up a lot of water and space. With that in mind, the researchers more recently looked to struvite – it's a phosphate mineral, which they obtained from human urine in wastewater treatment facilities.

In greenhouse tests, they planted string bean seeds in a total of 60 pots that were filled with either simulated lunar or Martian soil, or with regular Earth-type potting soil. Half of the pots additionally contained 15 grams of struvite, while the others had no added fertilizer. All of the plants were automatically watered daily, with the greenhouse being kept at a temperature of 20º C (68º F) at day and 18º C (64º F) at night.

On days without sufficient daylight, grow lamps were switched on
On days without sufficient daylight, grow lamps were switched on

As the bean plants sprouted, their length was monitored. The scientists noted that all of the struvite-fertilized plants showed the strongest growth, by quite a wide margin – particularly those grown in the lunar and potting soils.

The Martian-soil struvite plants did ultimately produce harvestable beans, although they did so a week later than the other two. That said, their growth rate might be boosted substantially if fertilizer obtained from human feces was also used.

Source: Wageningen University

4 comments
alan c
A few centuries ago human urine was a marketed commodity used as fertiliser. I've noticed that where my dog pees in the garden the grass first goes yellow, then grows far more strongly than surrounding areas.
Paul Smith
Alan, get your dog to pee in a bottle then dilute it and spray it evenly over the lawn.
ADVENTUREMUFFINffin
Works pretty well here on Earth too! Perfect Nitrogen, Phosphate, Potassium (NPK). Been using it exclusively in my garden for ten years now. https://permaculturenews.org/2016/06/14/biological-fertiliser-human-urine/
buzzclick
Some years back I learned that both urine and feces were beneficial to compost mixes. I would imagine that soil from the moon and mars have very little vegetative matter, and so would not be friendly to plant growth. Besides, if crucial water sources were limited, one would have to choose between drinking reprocessed urine or giving it to the plants. This is the main issue - water's availability. While this is being considered, I would think that hydroponics is the way to go for extra terrestrial greenhouses. We know there's some ice available. and the proportions of potassium, nitrogen and phosphates are not ideal in urine. Of course, if we use robots, none of this would be necessary.