Images of the PBRs being tested for use on the Moon. Credit: Acta Astronautica (2025). DOI: 10.1016/j.actaastro.2025.07.033
Astronauts exploring the moon will need all the help they can get, and scientists have spent lots of time and plenty of money coming up with different systems to do so. Two of the critical needs of any long-term lunar mission are food and oxygen, both of which are expensive to ship to the moon from Earth.
So, a research team from the Technical University of Munich spent some of their time analyzing the effectiveness of using local lunar resources to build a photobioreactor (PBR), the results of which were recently published in a paper in Acta Astronautica.
The concept around PBRs is simple enough—enclose some sort of biological system, like algae, give it the raw material it needs to live, such as carbon dioxide and water, and harvest the resulting “waste” products, like oxygen and the algae itself. Nature has a way of optimizing its processes, so depending on the design of the PBR, and especially on the choice of algae, they can be extremely effective at creating those useful outputs with very little waste.
However, they’re not so great at doing so on the lunar surface, which is why they would need to be enclosed in a system protected from the lunar environment, which includes direct sunlight since the radiation that goes along with it would kill the living organisms inside the reactor. Harvesting the materials needed to build that protective system is the focal point of the paper.
It considered two different types of PBR—a “tubular” air lift and a “flat panel” airlift (FPA). The FPA variety was more efficient, but required more maintenance than its tubular counterpart. Building either variety would result in a cost savings of at least a few million dollars per system, assuming a $100,000/kg launch cost to the moon. For the tubular system, it could be even more, with some estimates ranging up to $50M in savings by building it out of local resources.
Resources for most of the structural materials are already abundant on the moon, and there has already been plenty of work on making the metals out of lunar regolith that would be required to build its base structure. However, the algae inside the PBR require light, and that has to either come from internal lighting, which is extremely power intensive and requires advanced components like LEDs, or can come from the sun, which would require clear glass in at least part of the exterior housing. So far, no one has successfully created clear glass out of lunar resources, though that is an area of ongoing research.
LEDs are an example of another necessary component that is much harder to produce locally—electronics, and, to go along with that, plastics, such as sealing o-rings or the baseboards for printed circuit board assemblies. Research into how to make plastic on the moon is also ongoing, but still a long way off from utilization in a mission. However, the algae itself in the PBRs could be used as a biological feedstock for the plastic, though that would still require at least a beginning seed from Earth to get the process going.
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Phosphorus is another critical element of life that needs to be somehow collected on the moon in order for a long-term biological presence there, as Fraser discusses with Harry Brodsky, a Ph.D. student at UC Boulder.
Unfortunately, carbon, one of the primary ingredients in plastics, is relatively rare on the moon, as are elements critical for the long-term survivability of the algae, such as nitrogen and chlorine. To ensure none of those precious materials are wasted, the authors suggest recycling astronaut waste water, which will also contain at least some of those elements, as a way to “close the loop.”
However, there are plenty of challenges to overcome if PBRs are to be integrated as a mission-critical component of any long-term lunar mission. The authors themselves suggest a hybrid approach that utilizes more traditional in-situ resource utilization (ISRU) methods, like Molten Regolith Electrolysis, for oxygen production, while utilizing PBRs for their combination of food production alongside oxygen production.
Both technologies are useful, and will eventually find their place in a lunar colony. Until that time, though, research will continue on the best way to get the most out of the lunar resources we can access, and we’ll undoubtedly see some improved designs of PBRs, lunar-derived glass, and even algae harvesting methods by then.
More information:
Lina Salman et al, In-situ manufacturing of photobioreactors on the Moon using local resources, Acta Astronautica (2025). DOI: 10.1016/j.actaastro.2025.07.033
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