What the Marshian is all about
If sustainable, long-term settlements are to be established in space, we need a way to recycle waste in order to have a closed loop food system.
The wetland can be recreated on earth or in space with local resources, with minimal need for imported materials.
The Marshian uses a modified version of the French reed bed system to remediate human waste through a vertical flow waste treatment wetland.
Biomass produced by the wetland becomes available for a variety of uses, including food supplements, pharmaceuticals, and biofuel.
Modern ECLSS (Environmental Control and Life Support System) technology for recovering water from urine is highly efficient, but solid waste management is comparatively neglected. Current methods of managing human solid waste are geared more towards the remediation and disposal of waste rather than repurposing nutrients. The ISS handles fecal waste by bagging it and sending it back to Earth where it burns upon reentry. Even analogous sites on Earth use similar strategies; many Antarctic research bases and analog astronaut habitats report discarding feces into crevasses or storing them in a septic tank for removal after the mission. Given the extremely high costs of transportation in space, treating human solid waste in a cost-efficient way that allows for the repurposing of nutrients is critical.
The Marshian project addresses this issue through the construction of an artificial wetland in a closed atmosphere environment. This system would allow for the recycling of nutrients and the treatment of human waste, with an emphasis on using in-situ resources.
The proposed Marshian project incorporates a “French reed bed,” a vertical flow system that uses gravity to drive waste water through a series of terraced filters. First, wastewater enters the wetland and solid particles are removed through filtration and sedimentation. Biological processes (largely microbial) then degrade the remaining dissolved organic matter. With the nutrients removed from the wastewater, the retention basin stores the water and treats any remaining contaminants not removed in previous steps, rendering the water available for use.
A condensation system will facilitate the hydrological cycle and conservation of water in the enclosed system, which could reduce both energy costs as well as improve reliability.
Light and Thermal Control
Almost every point on the moon’s surface is exposed to 14 days of continuous daylight followed by 14 consecutive “nights.” The dark periods of time present a challenge for a photosynthetic system like the wetland, as well as the additional obstacle of thermal control. Potential solutions include locating the wetland in a Peaks of Eternal Light (PEL) region—rare areas of the moon exposed to nearly constant daylight. This may prove difficult, as this is likely to be competitive lunar real estate. If the Marshian cannot be located in a PEL region, other methods such as surface and space-based solar power, solar collectors, stellar reflectors, or nuclear energy are all potential solutions to light control. Additionally, bioregenerative strategies may be used to complement the solutions outlined above, including biofuel produced by the wetland, microbial fuel cells, and artificial photosynthesis.
Operations and Maintenance
Operations for the Marshian can be broken down into five phases: set-up, use, idle, harvest, and maintenance. The set-up phase, when the wetland is assembled, places a strong emphasis on the use of in-situ resources such as regolith (moon dust) sorted gravel and regolith-derived pipes. In the use phase, astronauts actively produce the wastewater input for the wetland. During the idle phase, astronauts are absent and/or not producing wastewater for the system. During this stage, it is crucial that the wetland is able to self-sustain in absence of crew members. Finally, during the harvest and maintenance phases, the biomass produced by the wetland system can be used for a variety of purposes, such as food supplements.
Continuously importing materials from Earth to sustain outposts in space is impractical long-term—not to mention, at about $10,000 per kilogram, expensive. In-situ resource utilization thus becomes crucial in creating sustainable life in space. A key component of the Marshian project is that it is as low-tech as possible. The idea is to enable construction with whatever local resources are available, be they on Earth or on the Moon.
One of the moon’s most abundant resources is lunar regolith, which is known to be a somewhat harsh material as neither wind nor water smoothes its edges. However, regolith is not entirely incapable of sustaining life (read more about how the Spring Institute is working to transform lunar regolith into fertile soil through low-cost bioremediation methods here).
By incorporating the use of regolith, the Marshian upholds the tenet of sustainability; the wetland needs very few inputs that can’t be found on site (exceptions include seeds and bacteria, which weigh very little and are therefore comparatively much easier and cheaper to transport).
Ecosystem successfully growing in simulant regolith, suggesting the capacity of the material for sustaining life.