Tests on performance and operation of the Closed Plant Experiment Facility (CPEF) of the Closed Ecology Experiment Facilities (CEEF) are currently under way. Tests on photosynthesis/transpiration measuring systems and procedures have been conducted since 1996. The CPEF has four independently controlled closed cultivation rooms, in which rates of photosynthesis and transpiration as the whole plant stand can be monitored simultaneously. Comparison of net photosynthetic (CO₂ exchange) rate of a 30m² rice stand calculated by multiplying the rate of CO₂ draw-down by room air volume, with the rate calculated from the mass of supplied CO₂ needed to hold steady state showed no difference exceeding 10% of each other between them. Changes in CO₂ exchange rate of rice stand calculated using the former method with changes in PPFD, temperature and CO₂ concentration were compared. Transpiration rate of rice stand with changes in PPFD, temperature and CO₂ concentration were also monitored by tracking both difference in water vapor concentrations calculated from inlet and outlet dew points and air flow rates.

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Experiments to elucidate effects of temperature on elimination properties of catalyst filter, of which main components were Copper and Manganese oxide and aluminosilicate, for typical contaminants in controlled ecological environment were carried out. Results of experiments for dimethyl sulfide and trimetyl amine with 100ppm of inlet concentration and 12859hr-1 of space velocity showed that elimination efficiency, average change rate of elimination efficiency, and total weight of eliminated contaminants were increased with increasing temperature ranging from 25t to 250°C. Although, effects of temperature for methyl mercaptan on these properties was not significantly actualized in the experimental conditions due to high efficiency at 25°C generation of condensation products, such as, dimethyl disulfide and dimethyl trisulfide was not detected at 150°C and 250°C of the experimental temperature. Typical behavior of an abrupt catalytic deactivation occurred in experiments for hydrogen sulfide and ammonia with the condition of 500ppm inlet concentration and 12859hr-1 of space velocity. In case of hydrogen sulfide, manganese sulfide was contained in the resultant catalyst filter, and elemental sulfur were observed in a ceramic pipe in which the samples were installed. Any change of outward appearance of the resultant catalyst filters set in the experiment for ammonia was not observed. An oxidation of contaminants containing sulfur to elemental sulfur, being typical catalytic, poison via manganese sulfide could be the main cause of catalytic deactivation of the filter. Through the all experiments, no different contaminant was converted from the inlet contaminants by the catalyst filter, except condensation products of methyl mercaptan at 25°C. Evaluation of the properties revealed in the experiments derived that control of operation temperature is a promising method for the application of the catalyst filter to CELSS.

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A long-term feeding experiment with tilapia, Oreochromis niloticus, in a fish-rearing closed tank (air-tight tank) with an O₂/CO₂ exchange unit was conducted to establish a closed ecological recirculating aquaculture system (CERAS). In this experiment, with the exception of evaporation/condensation to/from the air, and of use for water analysis, the water was not changed. The experiment was conducted for 189 days at 28°C with two other open tank systems having different experimental conditions respectively. One was exchanged rearing water (control tank) and the other minimized water exchanges (open tank). Fish density was adjusted every three weeks and fish fed a commercial diet daily. The water qualities, NH₄-N, NO₂-N and NO₃-N were periodically monitored. Dissolved oxygen (DO), flow rate and pH were continuously recorded by a personal computer. The biofilter holding the bacterial community from an established tilapia aquarium (cultured for one month before the experiment) was effective to nitrify ammonia to nitrate. Thus, toxic ammonia and nitrite in the water were negligible, while nitrate increased by the end of experiment (over 450mg NO₃-N/1). Replacement of the O₂/CO₂ exchange unit was required four times because of decreasing DO and water flow during this experiment.
In this closed system, tilapia showed normal growth and high feed efficiency compared with the recirculating open tank under a high concentration of NO₃-N over the 189-day period. After the experiment, nitrogen and phosphorus budgets in the closed system were calculated; 38.2% of N and 50.7% of P in the diet supplied were retained as fish growth; 3.4% of N and 38.5% of P were removed from the system as solid waste; and 49.3% of N and 1.4% of P were accumulated in the rearing-water.

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“Development of Closed Seedling Production System” by Prof. T. Kozai of Chiba University and “On Eco-material” by Prof. R. Yamamoto of University of Tokyo were given as lectures at Regular CELSS Research Meeting on March10, 1999. Outlines of these lectures are described focusing on global problems and material circulation on Earth.

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There is some confusion among society members due to wide scope that the society treats. Concept for Japan Society for Controlled Ecological Life Support Systems was revealed through discussions among members in Planning Division of the society. The obtained concept concerns life support systems for space systems and earth. Human's activities in many areas have led to the global problems, which should be treated in light of material circulation in a closed system.

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