A major hurdle to the sustainability of future human settlements on the Moon and Mars is their reliance on Earth-based fertilizers. According to new research published in the journal ACS Earth and Space Chemistry, organic waste processed by bioregenerative life support systems (BLiSS)—including human excrement—can react with local extraterrestrial rock (regolith) to provide essential nutrients for crops.
The study, authored by Harrison R. Coker of Texas A&M University alongside colleagues from NASA’s Kennedy Space Center, addresses a fundamental problem that future space colonists will inevitably face. Currently used inorganic nutrient solutions (such as Hoagland’s solution) are excellent for soilless plant growth but require continuous nutrient inputs sourced from Earth. Following the principles of in situ resource utilization (ISRU), scientists investigated whether lunar and Martian regolith simulants could be used to fortify nutrient solutions derived from locally generated waste.
BLiSS Technology and Recycling Human Waste
The cornerstones of sustainable space agriculture are Bioregenerative Life Support Systems (BLiSS). These systems attempt to fully recycle nutrients from organic wastes generated by astronauts—such as human waste and plant matter—and convert them into usable inorganic nutrient streams.
For this experiment, researchers utilized a high-fidelity liquid effluent from a working BLiSS prototype at NASA’s Kennedy Space Center (KSC), known as the Organic Processing Assembly (OPA). This system employs dual-stage anaerobic bioreactors, membrane filtration, and a phototrophic membrane bioreactor to completely oxidize nitrogen species and decompose organic matter.
The 24-Hour Experiment: Lunar and Martian Regolith in the Lab
The research team conducted a 24-hour batch experiment. During this period, the liquid effluent from NASA’s BLiSS system was reacted with two types of artificially produced rock dust designed to accurately mimic extraterrestrial soils:
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A lunar regolith simulant designated as JSC-1A.
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A Martian regolith simulant designated as MGS-1.
The results were then compared to control reactions conducted with pure water and a standard inorganic nutrient solution (Hoagland’s). The net sorption and dissolution of elements were quantified using inductively coupled plasma-optical emission spectroscopy (ICP-OES).
Chemical and Microscopic Results: Sulfur, Magnesium, and Calcium in Focus
Precision measurements revealed that the interaction between the simulants and the BLiSS effluent resulted in the dissolution of substantial quantities of useful elements, while certain materials were adsorbed:
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Phosphorus (P) demonstrated Langmuir sorption isotherms, while zinc (Zn) and potassium (K) demonstrated Freundlich sorption isotherms.
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The lunar simulant (JSC-1A) desorbed sizable quantities of sulfur (S), followed by calcium (Ca) and magnesium (Mg).
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The Martian simulant (MGS-1) also desorbed high amounts of sulfur (S), followed by magnesium (Mg), calcium (Ca), and sodium (Na).
The researchers also deployed X-ray photoelectron spectroscopy (XPS) and scanning electron microscope–electron dispersive spectroscopy (SEM-EDS) to observe physical and chemical changes in the solid phase. XPS analyses revealed elemental bonding of carbon (C), nitrogen (N), phosphorus (P), and calcium (Ca) on the simulants after reacting with the BLiSS solution. The SEM-EDS images—captured using electron beam energies ranging from 1 to 3 kV and an EDS set to 30 keV—clearly documented the physical weathering of the rocks: pitting was observed on the lunar simulant, while a covering of nanoparticles formed on the Martian simulant.
Conclusion
The study clearly highlighted marked differences between the reactions of traditional inorganic nutrient solutions and those of BLiSS effluents when interacting with regolith. The primary scientific takeaway is that lunar and Martian regoliths contain highly soluble components that can successfully fortify recycled human waste effluents with valuable metals and plant-essential nutrients, paving the way for more self-sustaining agriculture in future space outposts.
Official Source and Reference:
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ACS Earth and Space Chemistry (Original Study): Lunar and Martian Regolith Simulants Desorb and Weather after Exposure to Bioregenerative Life Support System Effluent