Researchers from Wageningen University have demonstrated that urine, in the form of the mineral struvite, can be used as a fertilizer for crop cultivation on Mars and the Moon.
Even though it may take a while for the first human to set foot on Mars, scientists are already busy speculating our potential to reside on Mars and other planets. These ambitions bring more hurdles to overcome beyond the apparent lack of breathable atmosphere. Mars is on average about 220 million kilometers away from Earth – a one-way trip could easily take about six months. If we plan an extended stay on the planet, we would need to bring a considerable amount of supplies, unless we could grow food locally.
The ‘Food for Mars and Moon’ project
The research team from Wageningen University, in collaboration with the B.A.S.E. project, is exploring exactly this: through their ‘Food for Mars and Moon’ project. The team investigates how to grow crops on Mars and the Moon, using the resources available there: regolith (loose, often weathered material on the surface of a planet or moon) and ice. Since actual Mars and moon regolith are respectively not available and scarce on Earth, the researchers used simulants that mimic these materials’ composition and texture to figure out how best to cultivate crops in those alien soils.
Fertile soil?
It’s quite the challenge, as the soils of Mars and the Moon are not known for their fertility. Regolith naturally contains little amounts of ammonium, nitrate, and phosphate, as well other essential plant nutrients . To farm crops there, we would need to improve the soil. A closed and sustainable agriculture system is crucial for this, the researchers say. In the past, the research team successfully cultivated various crops on regolith simulants, like potatoes, carrots, peas, tomatoes, garden cress, and radish. However, this was not a circular process and would not be sustainable in the long run. This project aims to make food production completely circular, eventually even including pollination by insects and the use of bacteria, fungi, and worms.
Struvite as Fertilizer?
Surprisingly, urine plays a role in this process too. “The urine sourced from mobile toilets at festivals in Amsterdam,” says lead researcher Wieger Wamelink. The useful substances from this urine were used in this research to grow green beans on the simulated Mars and Moon soil, successfully. The only problem? Regolith (and thus simulants) may contain traces of toxic metals that could end up in the plants. The researchers have not yet eaten the cultivated green beans for this reason. Additionally, ‘struvite’ (a pure mineral that can be extracted from urine and mainly consists of magnesium, ammonium, and phosphate) is not yet officially allowed as a fertilizer for edible crops.
But that could change. “Our research has shown that struvite can be an excellent fertilizer,” says Wamelink. “By applying struvite extracted from urine, we can close one of the links in the golden circle of crop production.” Wamelink emphasizes that this does not apply just to Mars and the Moon but also here on Earth. “In this way, we can use human urine in a safe and efficient manner. It stimulates plant growth and can greatly increase the harvest.”
