Controlled Ecological Life Support Systems 



Waste Management. Issues that must be resolved in waste management include: 



• Recycling nitrogen from organic wastes and oxidizing the residue to recover 

 CO : and H : 



• Recycling mineral nutrients and H,0 from solid waste and condensate 



• Controlling contaminants and atmospheric regeneration. 



Although systems exist for recycling nitrogen from organic wastes and oxidizing 

 the residue to recover CO : and H 2 0, they must be tested within a sealed envi- 

 ronment and integrated in the context of the Breadboard Project. Research at ARC 

 to evaluate the efficiency of wet oxidation techniques, including supercritical wet 

 oxidation, will contribute to the choice, testing, and installation of a system for the 

 Breadboard Project. Power consumption and reliability of the system are major 

 concerns that must be resolved. 



Recycling of mineral nutrients in the context of a CELSS is not well understood. 

 Ashing of solid wastes, including unused plant biomass and human wastes, will 

 recover the mineral content, but the mineral nutrients must be in a form useful 

 for return to the nutrient solution. Also, sodium chloride (particularly from the 

 human waste) must be separated, perhaps by reverse dialysis, from material going 

 into the plant nutrient solution, to avoid toxic effects on plant growth. Wet 

 oxidation research may help address the problem of nutrient recovery in a CELSS 

 environment. 



Currently available technology can recover water as condensate. The procedure 

 will be a major source of water for plant nutrient solutions in the Breadboard Pro- 

 ject. 



Accumulation of volatile compounds is an important consideration when 

 engineering a sealed environment. Plants generate compounds, such as ethylene, 

 that inhibit plant growth and other compounds, including CO, terpenes, and 

 mustard oils, that are possibly harmful to humans in a sealed environment. Some 

 construction materials liberate gaseous contaminants. The Breadboard Project will 

 be a test bed for monitoring and controlling those contaminants. Initial studies 

 using off-the-shelf technology have indicated that a catalytic conversion system 

 may be adequate for control of volatile contaminants. Maintaining 2 and CO : bal- 

 ance in a sealed system involving plants and man must be demonstrated, but it 

 appears that atmospheric regeneration is feasible in such a system using a com- 

 bination of biological and physicochemical systems already known. The main 

 requirement is a reliable demonstration in a CELSS. 



Human Requirements. Indefinite maintenance of human life requirements 

 within the context of a CELSS is probably feasible, as the Soviets have 

 demonstrated in several closure studies. Issues that must be clearly understood 

 and managed involve provision of a balanced diet, including carbohydrates, fats, 

 proteins for adequate calories, the major minerals and water, as well as essential 

 amino acids, trace minerals, and vitamins. These must be presented as an 

 aesthetically acceptable food product. 



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