Abstract: A life support system for providing a growth medium for at least one photosynthetic micro-organism and for converting CO2 to O2, with reduced water use that is as low as about 4 percent of the corresponding amount of water normally required for conventional micro-organism growth. The system includes a liquid transport capillary channel, a mixed culture photosynthetic biofilm and a liquid transport substrate that is positioned between and contiguous to the capillary channel and the biofilm, where the liquid transport rate is adjustable by adjustment of the local humidity. Approximately uniform radiation is received by the biofilm and contributes to microorganism growth.