An air buffer system of a Plant Cultivation Module in a Closed Ecology Experiment Facility (CEEF) was developed. The system controled a pressure difference between inside and outside of the module. Additionally, it kept low positive pressure inside the module. In this paper, major specifications were introduced and discussed. Moreover, simulation results of the system performance were presented and discussed.

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Appearence of colonies in microcosm in which three organisms, chlorella, bacteria, and protozoa, live together was simulated by using A-Life simulation method to show that the formation of colonies is essential for the stability of the microcosm at its mature stage. Though generic definition of the word “A-Life” is still not clear, we use it to indicate the behavior of complex systems governed by local rules between elements instead of global rules, i. e. differential equations.

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We have investigated microalgae culture systems for CO₂ elimination and O₂ regeneration in the closed system containing low CO₂ concentration (800ppm to 1%). A stainless steel reaction vessel (20l) with fluorescent lamps (20W×11) was constructed. We have already studied the effects of temperature, pH, O₂ concentration in supply gas using the reactor aerated with low CO₂ concentration on the cell growth of Chlorella sorokiniana ATCC22521 and the CO₂ elimination rate in the reaction vessel.
CO₂ elimination and O₂ regeneration were investigated with Chlorella sorokiniana ATCC-22521 under two light energy conditions (using 20W×11 fluorescent lamps and 20W×6 fluorescent lamps).
As the result, both cell growth of Chlorella and CO₂ elimination rate under the high light energy condition were higher than that under the low light energy conditions. But in comparison to the photosynthetic activity based on the chlorophyll content in the Chlorella cell was almost the same under two lighting condition.
We further investigated culture conditions for operating the system continuously with a half-batch culture.
We confirmed that the microalgae culture system maintained the ability of continuous CO₂elimination and O₂ generation when cell number and the concentration of nitrogen source in the medium were kept under the adequate conditions. However bacterial contamination in the vessel inhibited of the CO₂ elimination.

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Photocatalytic reactors are usually operated by suspending photocatalyst particles or packing with photocatalyst immobilized on any solid support, which provide heterogeneous reaction systems where reactions take place on the two-dimensional plane. Thus, these conventional reactors have unavoidable limitation to enhancement in the reaction rate because it is difficult to acquire a sufficient reaction field. On the other hand, titanium dioxide (TiO₂) can be dissolved in an aqueous solution of H₂O₂ to provide a transparent yellow solution, which enables to prepare a transparent TiO₂ thin film on the surface of a solid support. Based on this coating technique, two types of photocatalytic reactors were constructed; 1) consisting of a glass column packed with glass beads or short glass tubes and 2) a circular arrangement of 19 glass tubes linked in series and a fluorescent light positioned in the center. To investigate the performance of these two reactors, photocatalytic degradation of 2, 4-dinitrophenol was carried out in a batchwise recirculation system. Furthermore, the latter reactor was applied to oxidation of ethylene as an example of application to CELSS.

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