In phototrophic cultures, microalgae can be grown in two distinct production systems: open pond systems and enclosed PBRs. These production units control the environmental (viz. light, temperature, pH, salinity, nutrient qualitative and quanti­tative profiles, and dissolved oxygen), biological impact factors (viz. predation, viruses, competition and growth of epiphytes) and operational factors (viz. hydrau­lic residence time, harvesting rate, gas transfer rate, mixing equipment, shear rates and light exposure) that affect the growth of microalgae [106]. Full-scale operations of both open ponds and enclosed PBRs for biofuel-directed microalgae production are still mostly in demonstration phase, hence, their long-term operation perfor­mance will be required to counter the many uncertainties that prevail [162].