PHOTOSYNTHETIC CO2 CONVERSION TECHNOLOGIES USING A PHOTOBIOREACTOR INCORPORATING MICROALGAE - ENERGY AND MATERIAL BALANCES

Since microalgae have a high photosynthetic capability, solar energy-d riven CO2 fixation technologies using microalgae have the potential to convert CO2 in the stack gas from a thermal power station into energy -rich biomass. We investigated a new design of photobioreator in order to achieve efficient photosynthetic performance. The system has sever al advantages over the conventional mass culture system of microalgae. We have investigated the energy and material balances of microalgal b iomass production in a photobioreactor system both theoretically and e xperimentally. CO2 conversion to microalgal biomass in the laboratory scale conical-shaped helical tubular photobioreactor incorporating Spi rulina platensis was investigated. The photobioreactor system was cons tructed with a basal area of 0.255 m(2). The total volume of photostag e was 6.23 litre with 0.651 m(2) light absorbing area ( inner surface of cone). The photostage was illuminated with cool white fluorescent l amps, the daily energy input of the photosynthetic active radiation (P AR, 400-700 nm) into the photobioreactor was 1249 kJ. The productivity of Spirulina platensis of this photobioreactor was 15.9 g dry biomass per m(2) (basal area) per day, or 0.51 g dry biomass litre(-1) day(-1 ). This corresponded to a photosynthetic efficiency of 6.83% (PAR). Ac cording to these results, a large scale microalgal production using a unit basic type photobioreactor (1 m(2) basal area) is discussed.