Air revitalization In non-CELSS environments, air replenishment and processing typically consists of stored
air tanks and
scrubbers. The drawback to this method lies in the fact that upon depletion the tanks would have to be refilled; the scrubbers would also require replacement after they become ineffective. There is also the issue of processing
toxic fumes, which come from the
synthetic materials used in the construction of habitats. Therefore, the issue of how
air quality is maintained requires attention; in experiments, it was found that the plants also removed
volatile organic compounds offgassed by synthetic materials used thus far to build and maintain all man-made habitats. In CELSS, air is initially supplied by external supply, but is maintained by the use of
foliage plants, which create
oxygen in
photosynthesis (aided by the waste-byproduct of human
respiration, ). Eventually, the main goal of a CELSS environment is to have foliage plants take over the complete and total production of oxygen needs; this would make the system a
closed, instead of
controlled, system.
Food / consumables production As with all present forays into space, crews have had to store all
consumables they require prior to launch. Typically, hard-food consumables were
freeze dried so that the craft's weight could be reduced. Of course, in a self-sustaining ecosystem, a place for crops to grow would be set aside, allowing foods to be grown and cultivated. The larger the group of people, the more crops would have to be grown. As for water, experiments have shown that it would be derived from
condensate in the air (a byproduct of
air conditioning and vapors), as well as excess moisture from plants. It would then have to be filtered by some means, either by nature or by machine.
Waste-water treatment Early space-flight had travelers either ejecting their wastes into space or storing it for a return trip. CELSS studied means of breaking down
human wastes and, if possible, integrating the processed products back into the ecology. For instance,
urine was processed into water, which was safe for use in
toilets and watering plants. Wastewater treatment makes use of plants, particularly aquatic, to process the wastewater. It has been shown that the more waste is treated by the
aquatic plants (or, more specifically, their
root systems), the larger the aquatic plants grow. In tests, such as those done in the
BioHome, the plants also made viable
compost as a
growth medium for crops. ==Closed versus controlled==