NOVELTY - Closed system photobioreactor comprises closed photobioreactor chambers surrounded by water basin, where the photobioreactor is capable of growing the photosynthetic microorganisms, or closed photobioreactor chambers comprised of flexible, transparent plastic or composite film, with an air tube comprised of plastic film at the bottom of each photobioreactor chamber to provide sparging air bubbles to the chamber.    USE - The closed system photobioreactor is useful for cultivating algae for producing biodiesel and other biofuels, where the photosynthetic algae includes microalgae or cyanobacterium such as Nannochloropsis oculata, N.salina, N.sp., Tetraselmis suecica, T.chuii, Botrycoccus braunii, Chlorella sp., Chlorella ellipsoidea, Chlorella emersonii, Chlorella minutissima, Chlorella protothecoides, Chlorella pyrenoidosa, Chlorella salina, Chlorella sorokiniana, Chlorella vulgaris, Chroomonas salina, Cyclotella cryptica, Cyclotella sp., Dunaliella salina, Dunaliella bardawil, Dunaliella tertiolecta, Euglena gracilis, Gymnodinium nelsoni, Haematococcus pluvialis, Isochrysis galbana, Monoraphidium minutum, Monoraphidium sp., Nannochloris sp., Neochloris oleoabundans, Nitzschia laevis, Onoraphidium sp., Pavlova lutheri, Phaeodactylum tricornutum, Porphyridium cruentum, Scenedesmus obliquus, Scenedesmus quadricaula, Scenedesmus sp., Skeletonema, Stichococcus bacillaris, Spirulina platensis, and Thalassiosira sp. (all claimed).    ADVANTAGE - The closed system photobioreactors can be manufactured inexpensively.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for method of producing a biofuel which involves growing photosynthetic microorganisms in growth medium in a closed system photobioreactor, where the photobioreactor comprises one or more closed photobioreactor chambers surrounded by water basin, harvesting the photosynthetic microorganisms in continuous, semi-continuous or batch mode process, and converting lipids or carbohydrates from the photosynthetic microorganisms into a biofuel.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of photobioreactor system.    Heating system (120)    Cooling system (125)    Control box (130)    Low shear pump (135)    Common medium header (140)    Medium mixing (155)