Figure 1. A conceptual process for producing microalgal oil for biodiesel. Water, inorganic nutrients, carbon dioxide and light are provided to microalgal culture during the
biomass-production stage. In the biomass-recovery stage, the cells suspended in the broth are separated from the water and residual nutrients, which are then recycled to
the biomass-production stage. The recovered biomass is used for extracting the algal oil that is further converted to biodiesel in a separate process. Some of the spent
biomass can be used as animal feed and for recovering other possible high value products that might be present in the biomass. Most of the biomass undergoes anaerobic
digestion, which produces biogas to generate electricity. Effluents from the anaerobic digester are used as a nutrient-rich fertilizer and as irrigation water. Most of the power
generated from the biogas is consumed within the biomass-production process and any excess energy is sold to grid. Carbon dioxide emissions from the power generation
stage are fed into the biomass production.