The use of photosynthesis in the control of enclosed environments.

Abstract

THE USE of photosynthesis in the control of enclosed environments is a specialized application of the process to the recovery of oxygen, water, and nutritive organic materials contained in the solid, liquid, and gaseous wastes of a man or group of men constituting the crew of a space vehicle. The possibility of applying photosynthesis to the gas exchange requirements of the occupants of a space vehicle has been recognized for some time, and many studies have been made on the subject.1-3 Although the stabilization of liquid and solid wastes through the use of bacteria, fungi, and protozoa had been considered and studies made on their application to enclosed environments,4'5 the incorporation of photosynthesis into the process was not considered feasible until research conducted at the University of California showed that it could be done successfully. The studies demonstrated that the complete process of environmental control, i.e., gas exchange and the treatment and recycling of materials contained in the wastes of the crew. can be integrated into a twophased process functioning through the activities of algae and bacteria. Bacteria convert the complex compounds contained in the liquid and solid wastes to carbon dioxide, water, ammonia, and various degradation products. Through photosynthetic activity, algae convert the bacterial decomposition products, as well as the carbon dioxide released by the crew, to new algal material, and, in so doing, release oxygen which can be used by the crew and by the bacteria. Since the original putrescible organic matter in the wastes is converted to algal and bacterial material which is removed, the water which remains is suitable for reuse. Although in the system of photosynthetic controls of enclosed environments described in the foregoing there is an overlapping of gas exchange and waste treatment, for the sake of convenience these subjects will be discussed separately.