Recycled Human Waste Could Help Grow Food on the Moon and Mars
On the moon, the soil is as sharp as glass. On Mars, it’s dusty, dry, and barren. Neither resembles the soft earth farmers depend on. Yet if humans are going to live beyond Earth, crops will have to grow in that material.
Rather than hauling tons of soil across millions of miles, scientists are exploring a different solution: turning waste produced inside a space habitat into a tool for transforming regolith — the loose rock and dust that blankets the moon and Mars — into something plants can use.
A new study published in ACS Earth and Space Chemistry suggests that recycled sewage could help create essential nutrients trapped inside extraterrestrial minerals. In other words, the key to farming in space may be what astronauts flush away.
The researchers used a treated, simulated sewage solution designed to mimic the recycled waste streams that future moon or Mars habitats would generate.
“In lunar and Martian outposts, organic wastes will be key to generating healthy, productive soils,” explained Harrison Coker, the first author on the study, in a press release. “By weathering simulant soils from the moon and Mars with organic waste streams, it was revealed that many essential plant nutrients can be harvested from surface minerals.”
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Why Regolith on the Moon and Mars Can’t Support Plants
At first glance, regolith looks like soil. But it lacks the critical ingredient of life.
Earth’s soil forms through the constant work of microbes, plant roots, water, and decaying organic matter. Over millions of years, those processes break down minerals and recycle nutrients into forms plants can absorb. Lunar and Martian regolith, by contrast, is sterile. It contains no organic material and no biological community to help release nutrients.
It is also physically harsh. The particles are angular and abrasive, shaped by impacts and volcanic activity rather than by wind and water. On its own, regolith offers little support for crops.
How Recycled Sewage Unlocks Nutrients in Regolith
At NASA’s Kennedy Space Center, scientists are developing bioregenerative life support systems designed to recycle waste inside future space habitats. These systems convert sewage into nutrient-rich liquids that can potentially be reused.
In the new study, researchers mixed an artificial sewage solution with simulated lunar and Martian regolith. After shaking the mixtures for 24 hours to encourage chemical reactions, they examined what had changed.
The regolith simulants released measurable amounts of essential plant nutrients, including sulfur, calcium, and magnesium. Under a microscope, the team observed clear signs of mineral weathering: tiny pits forming on lunar particles and nanoparticles coating Martian grains.
Weathering is the slow process that turns rock into soil on Earth. Here, the recycled waste solution appeared to accelerate that transformation, chemically breaking down minerals and making nutrients more available.
The process also seemed to dull the sharp edges of the particles, potentially making the material less hostile to delicate plant roots.
Building Soil for Farming on the Moon and Mars
The researchers caution that laboratory simulants are not identical to actual lunar or Martian regolith, and further testing will be needed before crops can realistically be grown in extraterrestrial material.
Still, the findings highlight a principle that will likely define long-term space exploration: nothing can be wasted.
In a sealed habitat on the moon or Mars, every resource must circulate in a closed loop. Water, air, and nutrients will need to be continuously recycled. If organic waste can help unlock nutrients trapped in regolith, astronauts could transform what was once discarded into the foundation of an agricultural system.
Growing food off-world will require more than seeds and sunlight. It will require building soil from scratch, and the raw materials for that soil may already be inside the habitat.
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