(812e) Sustainable Algae Oil Production: Integrating Waste Water

Microalgae have excellent potential for industrial applications that require the production of lipids/oil. Algae oil can be used to produce biodiesel fuel and other valuable products. Yet large scale production of microalgae is energy and water intensive. Clearly improvements in the algae growth process that would decrease the fresh water requirements, lower the energy use and make the process greener are highly desirable.

Goals: The goals of this project are to improve the oil production in algae while lowering the energy and fresh water requirements. This research has experimented with integrating the use of waste water in microalgae growth to reduce the fresh water requirement, and replacing fluorescent light with low energy LEDs to make the growth process more energy efficient. Based on analysis of the algae chlorophyll spectrum two sets of LEDs were selected, red and red-blue.

Experiments: Algae (Chlorella vulgaris) were cultivated in two liter clear plastic photobioreactors in the Biodiesel Lab. Scale-up studies were done in an 80 L clear plastic PBR. Air was bubbled in all photobioreactors to supply CO2 and effect stirring of the PBR contents. The PBRs which were exposed to lights 24 h/day and operated at room temperature. Three light sources were used; Fluorescent lights, Red LEDs panels and Red-Blue LED panels. Each panel was 30 cm X 30 cm and contained 225 LEDs. The Total energy saving using LEDs relative to fluorescent light is about 48.5%. Two algae growth medium were used: Fresh Water obtained from a reverse osmosis (R.O.) unit. Municipal waste water used was obtained from the Dover NH wastewater treatment plant. Typical properties of the waste water used were pH=6.83, total nitrogen (TN) =14 mg/L, total phosphate (TP) =1.3 mg/L, Biological oxygen demand (BOD) =10 mg/L, Total suspended solids (TSS) =7 mg/L. 

Results:The experimental data collected show that the highest algae lipid production (12.5 mg/L solution-day) was obtained from algal biomass cultivated in fresh water using red-blue LEDs with light intensity of 2000 Lux. Light source has much less effect on algae lipid production from algal biomass cultivated in waste water compared to fresh water. The lipid production from algal biomass cultivated in waste water is 30% of that in fresh water. Scaling–up microalgae growth using 80L photobioreactor illuminated by fluorescent light makes waste water more promising. Almost the same algae biomass production rate of 36.75 and 36.6 mg dry algae/L solution-day were obtained from algae growing in fresh water and waste water respectively at room temperature. Lipid yields of 4.3 and 2.27 g lipids/100 g dry algae were obtained from algal biomass cultivated in fresh water and waste water respectively. Results will be presented and discussed.