Oxygenic microalgae and cyanobacteria, which utilize solar energy, H₂O, and CO₂, to produce biomass, are rapidly being developed as alternative to plants for production of biofuels and other biotechnology products.  Currently, research aimed at increasing the productivity of photosynthetic microorganisms is conducted with pure cultures using open-pond systems or closed photobioreactors.  This approach has a number of drawbacks: simultaneous fixation of CO₂ and subsequent conversion of the photosynthate by a monoculture creates specific metabolic engineering and cultivation challenges.  To address these issues, we developed an approach utilizing binary photoautotroph-heterotroph cultures that spatially separate the processes of photosynthesis and photosynthate conversion into useful products.  Binary cultures allow cultivation of readily-engineered heterotrophic strains for major biotechnology products using CO₂ and light instead of commodities such as glucose, sucrose, and agricultural feedstocks.  Moreover, O₂ as well as carbon and energy source(s) for the heterotrophic organism will be uniformly produced in the liquid culture, ensuring absence of shock by periodic excess or deficiency of nutrients and oxidants that conventional types of cultivation usually suffer.  The heterotrophic organism will consume O₂ produced as the result of photosynthesis, thus dramatically decreasing mass transfer energy expenditure and simplifying photobioreactor design and operation.  The binary culture approach also allows the utilization of various carbon sources ranging from CO₂ from power plants to municipal wastes.  Because of the robustness of the phototroph-heterotroph association, the binary cultivation provides a novel platform for the development of consolidated bio-processing methods leading to production of carbon-neutral energy at reduced economic and energetic costs.