ＲＩＴＥ−AＭＡＧＡＳＡＫＩ ＮＯ．２ LABORATORY
in Kansai Electric Power Company.

ＲＩＴＥ−NＡＮＫＯ LＡＢＯＲＡＴＯＲＹ
in Kansai Electric Power Company.

Hydrogen is a clean renewable form of energy, convenient to store and transport. Hydrogen production by biophotolysis of water based on microalgal photosynthesis in the carbon recycling system is thus an ideal solar energy conversion system for the sustainable human activities in harmony with the global environment.

Our biological hydrogen production system consists of the three steps as follows;

(1)photosynthetic starch accumulation in the green algae; (2)algal fermentation to produce organic compounds; (3)further conversion of the organic compounds to produce hydrogen by nitrogenase of the photosynthetic bacteria.

We are making research on the scaling up of this photosynthetic hydrogen production system in order to realize the industrial development of this system in a natural day-night cycle.

For the experiments of the scaling up studies, the marine green alga Chlamydomonas MGA 161 was cultivated in the raceway type cultivator of 400 L under sun light. The cultivated algal cells were concentrated to one third of the initial volume and transferred to the fermentation tank of 135 L, in which fermentative production of hydrogen and organic substances was done at 30℃ under dark anaerobic conditions. The organic substances were separated through hollow fiber filatration and transferred to the photobioreactor of 200 L, in which the organic substances were converted to hydrogen by photosynthetic bacterium Rhodovulum sulfidophilum W-1S at 30℃ under sun light and anaerobic condition with argon. As the results of these scaling up studies, we established the stable operation system of this pilot plant for the hydrogen production in a natural day/night cycle.

For easier separation of the bacterial cells from culture broth, we have also examined the immobilazation of photosynthetic bacteria, and the immobilization of the bacterial cells with a polyvinyl alcohol photopolymer was found to be effective.