CAL POLY STATE UNIVERSITY SAN LUIS OBISPO GRANT FOR A LOW-COST, WASTE-GROWN ALGAE BIOFUEL FEEDSTOCK PRODUCTION PROJECT
California Polytechnic State University in San Luis Obispo, CA, is in the process of demonstrating a pilot system called Reclamation of Nutrients, Energy, and Water (RNEW™). RNEW™ will grow and collect oil-rich algae that could be feedstock for biodiesel while also treating wastewater. Cal Poly is determining how to grow an algal bloom and then starve it into producing oil.
The RNEW™ process uses only untreated wastewater, not fresh water. An algae biomass growing system was built inside a protective berm at the City of San Luis Obispo's water reclamation teaching facility. Students built nine oblong raceway ponds of cement blocks and waterproof pond liner 30 m2 each. They designed and built plastic paddle wheels that turn on one axle to stir all 9 experiments at the same rate. Plastic piping from the primary clarifer goes under a road to provide the variable nutrients of municipal waste water to three constant-head reservoirs. Three student-designed, simple, wide-cup, rotating dipper systems continuously deliver waste water to three groups of 3 ponds as a “non-clogging pump”. Protozoa and bacteria inhibit wild algae as it grows, but wild birds are kept out with netting. Sensors and a wireless transmitter send pH, temperature, and dissolved oxygen records to campus. Water exits through one algae settling collector (Imhoff cone) for each pond, yielding a 10-15% solids slurry, and the water gets pumped back to the primary clarifier. System construction was complete January 2012 and will be maintained as a teaching facility.
$442,000 from the project's participants.
The process has already achieved lipid production levels equivalent to 1,200 gallons of oil per acre each year. The RNEW™ process is entirely dependent on untreated wastewater and does not require fresh water. Power for the project will come from a co-generation power plant fueled by biomethane from an anaerobic digester that uses spent algal biomass as feedstock. According to Cal Poly San Luis Obispo, a 400-hectare (about 1.5 square mile) system would have a very low greenhouse gas contribution. Based on the average observed oil content in the 30-m2 ponds, 12%, GHG emissions are 1.12 gCO2e/MJ well-to-wheel total. When the goal of 30% oil content is reached, the GHG emissions increase for algae biodiesel to 26 gCO2/MJ (Figure 5.4). From a GHG perspective, producing more biogas electricity and less liquid fuel is superior. Yet high production liquid fuel is more economically desirable.
Their analysis shows that a 400-hectare system would require 52 full-time operators. The technology can be replicated at wastewater treatment facilities, animal waste and some industrial water applications.
Grant Agreement Number: ARV-10-027