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Prototype bioreactor using internal lighting mechanism was manufactured for biological CO2/O2 conversion system. Microalgae culturing experiments were carried out on Chlorella ellipsoidea C-27 to estimate the effect of light intensity on photosynthetic activity in the reactor. The light energy source used was an Xe(xenon) lamp, from which light is transferred through optical fibers and diffused from the surface of rods made of acrylic resin. Total surface area of the rods was 0.12m2. Tests under the continuous lighting (600W) condition indicated a highest specific growth rate of 8.54 (h-1), a highest cell density of 1.3 × 108 (cells/ml), and a maximum overall photosynthetic rate (CO2 absorption rate) of 171.84 (mg-CO2 absorption/Ir-medium/day). In contrast, the maximum CO2 absorption per chlorophyll content (mg-CO2 absorption/mg-chl/h) was reached under the alternating lighting condition.

We have constructed a unit that uses microalgae to treat atmospheres containing low (i.e., (1000 ppm to 1%) concentrations of carbon dioxide. This experimental unit consists of a 20 l microalgae cultivation tank with eleven fluorescent lamps installed uniformly inside; and an analyzer with aeration/discharge, cultivation solutions supply/discharge function, and control capabilities. Using this unit, we conducted a series of experiments designed to reduce CO2 concentration in air from about 1000 ppm to atmospheric levels, and to regenerate oxygen. We used Chlorella sorokiniana ATCC22521, a species of green algae, which is said to have a relatively high growth rate. We studied a number of necessary conditions. We performed a series of experiments under various cultivation temperature conditions.