How human sewage might transform dead space dirt into fertile soil
If humanity is ever going to establish permanent outposts on the moon or Mars, astronauts will need to grow their own food. And the key ingredient? Their own waste.
As explained here, a new experiment led by Harrison Coker of Texas A&M University has shown that human sewage, when combined with lunar or Martian regolith—the inorganic dirt found on the surfaces of these worlds—can unlock nutrients trapped inside surface minerals, potentially making it possible to grow crops in space.
“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,” Coker explained.
The problem with space dirt
The dirt on the moon and Mars isn’t really “soil” in any meaningful sense. Scientists call it regolith—a purely inorganic material that, while it does contain nutrients locked inside minerals, makes those nutrients almost entirely inaccessible to plant life. Growing crops directly in it is, for now, essentially impossible.
Previous attempts to fix this have involved heat treatment, hydroponics, ionic liquids, and electro-deoxidation. But all of these approaches share the same fundamental flaw: they require chemicals, energy, and technology to be continuously imported from Earth, making them expensive and unsustainable for long-term space habitation.
Sewage as a solution
Coker’s team took a different approach, focusing on in-situ resource utilization—using only what astronauts would already have available. The two ingredients: regolith and human waste.
Working with scientists at NASA’s Kennedy Space Center, the researchers used a prototype bio-regenerative life support system called the Organic Processing Assembly (OPA)—a series of bioreactors and filters that takes raw sewage in at one end and produces a nutrient-dense, toxin-free liquid effluent at the other.
That effluent was then mixed with simulated lunar and Martian regolith and placed in a shaker for 24 hours to simulate the natural weathering process. The results were promising: the lunar simulant released significant amounts of sulfur, calcium, and magnesium, while the Martian simulant released those same nutrients plus sodium—all of which are essential for plant growth.
Under a microscope, the physical transformation of the regolith was also visible. Lunar simulant particles developed tiny pits on their surfaces, while Martian simulant particles became coated in nanoparticles—both signs of the kind of weathering that begins to turn dead regolith into something closer to real, living soil.
The concept isn’t entirely new to science fiction fans—it mirrors the actions of stranded astronaut Mark Watney in “The Martian,” who famously fertilizes Martian dirt with human waste to grow potatoes and survive.
Still a work in progress
The results are exciting, but the researchers are careful to note the limitations. Plants need a far broader range of nutrients than what was released in these experiments—iron, zinc, and copper were notably absent. The OPA technology is also not yet fully efficient, and the simulants used are only approximations of real lunar and Martian regolith, which could behave quite differently.
Mars presents additional challenges. Its regolith tends to be dense and clay-like, which can suffocate plant roots by blocking oxygen. It also contains perchlorate, a powerful and toxic oxidizer that poses serious risks to plant life and any biological processes involved in soil treatment.
A growing body of research
This study is part of a broader and rapidly expanding field of research into how future space settlers could live off the land. In January 2025, a separate study found that crops grow better in fertilized lunar regolith than Martian regolith, citing the density and perchlorate toxicity of Martian soil as key obstacles.
Other researchers have explored using bacteria to address Mars’s hostile soil conditions and even to construct building materials. Scientists at the Indian Space Research Organisation have shown how certain bacterial strains can bind Martian regolith into brick-like structures suitable for building habitats—though the perchlorate toxicity required finding more robust bacterial strains to survive the harsh conditions. Similar techniques have been applied to lunar construction, where bacteria-derived sealants are used to fill cracks in sintered regolith bricks.
Turning human sewage into a farming resource may sound unpleasant, but in the context of deep space survival, it’s an elegant solution. Waste is one resource that astronauts will always produce in abundance—and if it can be harnessed to feed them in return, it could prove to be one of the most valuable tools in humanity’s push to colonize Mars and beyond.