Bacteria do the work in the biodigester to turn excreta into phosphorus. The anaerobic digestion process starts as soon as waste enters the biodigester. The bacteria break down the materials into carbon dioxide, methane gas, and phosphorus. The gasses evaporate and exit through the ventilation in the upper portion of the biodigester.
The filter inside of the biodigester separates the liquids from the solids, siphoning them out through a drainage well where it is filtered through rock, gravel and sand before being release to permeate the subsoil as treated water.
Having been stripped of gasses and liquids, the remaining solids – primarily phosphorus – accumulate at the bottom of the tank. After a year of anaerobic activity there, a quick turn of the faucet will allow gravity to pull it to the secondary container where it should be left to dry for a further two months.
Once mixed with a little common lime, what was once a messy problem becomes a potent fertilizer for the garden.