Research and Development of Operation Technology on the Waste Processing System of the Closed Ecology Experiment Facilities for Circulation of Carbon in an Experimental Closed Ecosystem Comprised of Humans, Goats and Crops

Before a series of overall material circulation in an experimental system including crops, animals and humans, technical examinations for the development of a waste processing system were conducted for incorporating the system to the Closed Ecology Experiment Facilities (CEEF). The examinations are intended to validate the function of the carbonization and incineration processing units which were installed in the CEEF in 2006. Using different mock-up samples, examinations have been carried out to verify the function and capability of the whole system, including the waste carbonization processing unit, incineration processing unit, exhaust gas tank and the exhaust gas processing unit. In an examination using filter paper pulp as a mock-up sample, processing time in each unit was checked. The processing times needed for carbonization and incineration processing were 5.7 and 2.6 hours, respectively. In an examination, using chaff as substitute for inedible plant parts, the carbonization of 400 g of the chaff generated 170-175 g of carbonized substances, and it generated 54-76 g of ash residue in the subsequent incineration process. In the exhaust gas processing unit, satisfactory capability of CO₂ separation could not be realized because of the influence of moisture in the exhaust gas. However, several measures to solve these problems were adopted in an experiment in 2007. In the habitation experiments in 2007, wastes discharged from the CEEF were actually processed. The remaining inedible plant parts after using as feed for animals were carbonized in the carbonization processing unit. The urine of the econauts was added to drainage from washing the animal pen; this drainage also contained the excrement and urine of the goats. This combined waste water was dried and carbonized in the carbonization processing unit. The carbonized inedible plant parts, the carbonized human and goat urine and goat excrement, and the carbonized human excrement that was generated by the dry-toilet system, were burned in the incineration processing unit. Gaseous CO₂ separated from the exhaust gas of the carbonization and incineration processing units in the exhaust gas processing system was sent to CO₂ tanks, and was used for plant cultivation. Moreover, minerals extracted from ash residue produced by incineration were added to nutrient solution for plant cultivation. Equipments for toxic gas elimination of the waste processing system worked efficiently during the closed habitation experiments in 2007. As a result, the maximum concentrations of CO, NO₂ and SO₂ in the PM were 8.0, N.D. (less than 0.02) and N.D. (less than 0.05) umol mol^-1, respectively. And the maximum concentrations of CO, NO₂, and SO₂ in the AHM were 8.0, 0.06 and N.D. (less than 0.05) umol mol^-1, respectively.