Earthships use both indoor and outdoor botanical treatment cells to use, store and reuse all sewage produced in the dwellings. This helps with food production, as well as the ability to landscape without polluting aquifers. Toilets use treated gray water, which does not have an odor, to flush with.
Water in an Earthship is used 4 times:
First, as fresh water – water used in sinks, showers and baths.
Second, this water, now known as gray water, is cleaned in the interior botanical cells and used for indoor plant and garden watering.
The third use is the water becoming toilet water, after which the water is contained and cleaned again.
Finally, it is used a fourth time with the exterior botanical cells and used for fertilizing outdoor plants and gardens.
Exterior Botanical cells can be added as needed to the outdoor system. Additional cells can be added to the controlled aspect of landscaping the home. By containing the outdoor system, it is more manageable.
The goal of the exterior botanical cells is to get multiple water uses from the water catchments and to eliminate the need for public sewage systems and septic systems. The sewage treatment system is used by Earthship is set up to flow entirely into either a septic tank or leachfield.