Production of Spirulina biomass in closed photobioreactors

The results of a six year investigation on the outdoor mass culture of Spirulina platensis and S. maxima in closed tubular photobioreactors are reported. On average, under the climatic conditions of central Italy, the annual yield of biomass obtained from the closed culture units was equivalent to 33 t dry weight ha -1 year-k In the same climatic conditions the yield of the same organisms grown in open ponds was about 18 t ha -I year -1. This considerable difference is due primarily to better temperature conditions in the closed culture system. The main problems encountered relate to the control of temperature and oxygen concentration in the culture suspension. This will require an appropriate design and management of the photobioreactor as well as the selection of strains specifically adapted to grow at high temperature and high oxygen concentration. Key words: Spirulina, outdoor mass culture, tubular reactor, photobioreactor