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In a closed space system at a ground test facility with environmental control and life support system, carbon dioxide as the products of human and animals respiration is adsorbed and condensed by solid amine and desorbed by aqueous vapor (steam). The carbon dioxide is then reduced to methane and water using hydrogen. Oxygen is recovered from the produced water using an electrolytic system with a solid polymeric membrane and will be reused for respiration. This report describes the result of the fundamental research on individual technological elements: the reduction of carbon dioxide using hydrogen, the decomposition of produced methane and the water electrolysis.

The simulation test for the closed ecology experiment facility is planned by Institute for Environmental Sciences(IES) of Japan. The purpose of this test is to confirm that in the closed space, how the ecological factors influence the mass circulating system. The environmental and life support system in IES is based on the same principle as on the earth where the carbon dioxide produced by the respiration of human and animals is reduced to oxygen by the photosynthesis of the plants, but as an auxiliary system, artificial carbon dioxide reduction system is planned to be attached. This report describes about the loop test for the reduction of carbon dioxide using the Sabatier method: the reduction of carbon dioxide using hydrogen, the decomposition of produced methane and the water electrolysis. (See Figure 1)

One of the important feature in the Environment Control and Life Support System required to support long duration mission at the Space Station is an oxygen supply for the human metabolism. The recovery of oxygen from the concentrated carbon dioxide through chemical methods will give significant advantage to the Space Station by reducing the supply requirement of the consumables, such as oxygen bottles. Oxygen recovery plants using the Bosch reaction and the Sabatier reaction are experimentally developed and tested. The Bosch reaction has been considered to produce carbon and water directly from carbon dioxide by the hydrogenization process. But it seems to proceed through two steps with carbon monoxide as the intermediate product. Also the total production rate is relatively low and the carbon deposited is less solid. The Sabatier reaction requires two steps to achieve carbon and water, with methane as the intermediate product.