Photosynthetic oil production in a two-stage reactor

A system and method are provided for producing algae with high oil content. The system includes a chemostat formed with a conduit for growing algae, an input port for feeding a medium into the conduit, and an output port for passing an effluence from the conduit. Further, the chemostat includes a paddlewheel or other device that moves the medium around the conduit. Also, the system includes a plug flow reactor for receiving the effluence from the chemostat. In order to trigger high oil production in the algae, a modified nutrient mix is added to the effluence in the plug flow reactor. Specifically, the modified nutrient mix comprises a limited amount of a selected constituent to trigger oil production in the algae. Further, the system includes an algae separator for removing high oil content algae from the plug flow reactor.