TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Apparatus: The apparatus further comprises multiple axial vortex inducers vertically arranged within the tubes to provide rotational mixing of the aqueous medium. The adjacent axial vortex inducers are arranged with opposite clockwise and counterclockwise twists. Preferably, the tubes are arranged horizontally along the ground. The apparatus further comprises two flexible tubes and two peristaltic rollers, each tube operably coupled to a single peristaltic roller. It further comprises a first and second control housing operably coupled to the ends of the two tubes to form a biologically closed system.The apparatus also comprises a whirlpool device in the first control housing to concentrate algae or other aquatic organisms or to remove mucilage or foam. It also comprises one or more sipper tubes operably coupled to the whirlpool device to remove concentrated algae or other products from the apparatus. The apparatus further comprises a gas bubbler in the second control housing to provide CO2 to the aqueous medium. The movement of the peristaltic rollers along the tubes removes oxygen or other dissolved gases from the medium.The apparatus further comprises a thermal barrier within the tubes to regulate the temperature of the medium, where the medium may be alternatively directed above or below the barrier to expose or isolate the medium from its thermal environment. It further comprises a mechanism within the first control housing to direct the medium above or below the barrier, where the mechanism comprises at least one stiff septum linked to at least one actuator that positions the septum to direct the medium above or below the barrier.The apparatus further comprises a gas bubbler in the second control housing to provide CO2 to the aqueous medium, where the gas bubbler comprises a perforated neoprene membrane through which gas is bubbled. The gas bubbles are introduced at the bottom of a water column, the water moving in a downward direction and the gas bubbles moving in an upward direction.Preferred Method: The method further comprises separating algae from the medium, removing oil from the algae, and producing biodiesel from the oil. The biodiesel is produced by transesterification. The method further comprises circulating the algae through the bioreactor using peristaltic rollers. The algae within the tubes are rotationally circulated using axial vortex inducers in the tubes. It further comprises introducing CO2 gas into the medium using one or more CO2 bubblers. Algae are partially separated from the medium using a whirlpool device. The method further comprises separating non-oil products from the algae, where the non-oil products comprise carbohydrates. Carbohydrates are converted into hydrogen gas, methane gas, and/or ethanol. It also comprises harvesting the algae for use in animal or human food. Preferably, the algae are Spirulina, Dunaliella, or Tetraselmis. The method also comprises using the algae as food for an algae-eating aquatic species, where the aquatic species is a peneid shrimp.Preferred System: In the system for producing biodiesel from algae, the mechanism for harvesting algae comprises a whirlpool device and one or more sipper tubes, or comprises at least one centrifuge. The apparatus for converting oil into biodiesel utilizes a transesterification process. The closed bioreactor comprises one or more rollers on one or more tracks, the rollers arranged to roll down the length of the flexible tubes to move the aqueous suspension through the tubes. The rollers in contact with the tubes are arranged so that they compress the tubes to 85% of the height of the uncompressed tubes. Movement of the aqueous suspension through the tubes results in a whirlpool fluid movement at one end of the tubes, where the whirlpool fluid movement results in a partial separation of oil-containing algae from the aqueous medium.The tubes contain a thermal barrier arranged within the tube, parallel to the ground surface, to regulate the temperature of the aqueous suspension within the tubes. The height of the thermal barrier above the ground may be adjusted to control the temperature of the aqueous suspension. During daylight hours the flow of the aqueous suspension is directed below the thermal barrier to maintain the temperature of the suspension at ground temperature and above the thermal barrier to warm the suspension. During nighttime hours the flow of the aqueous suspension is directed above the thermal barrier to cool the suspension and below the thermal barrier to maintain the temperature of the suspension at ground temperature.The thermal barrier is comprised of 1.0 inch thick polyethylene foam or other air filled cell construction. The upper surface of the thermal barrier comprises a layer of sand, a translucent ceramic or plastic, a silicate or glass. It also exhibits an infrared emissivity of close to 1.0. Movement of the rollers collects oxygen and other gases from the medium for removal from the system. The outer layer of plastic is indented with a linear Frenel pattern that collects sunlight from a lower Snell's law angle and directs it into the algae growing medium. The tubes are laid out perpendicular to the low angle southern sun for the winter months in temperate climates.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The outer surface of the tubes is comprised of a plastic selected from polyethylene, polypropylene, polyurethane, polycarbonate, polyvinylpyrrolidone, polyvinylchloride, polystyrene, poly(ethylene terephthate), poly(ethylene naphthalate), poly(1,4-cyclohexane dimethylene terephthalate), polyolefin, polybutylene, polyacrylate, or polyvinylidene chloride. Preferably, the outer surface of the tubes is comprised of 0.01 inch thick polyethylene.