Propulsion and Power Rapid Response Research and Development (R&D) Support. Task Order 0004: Advanced Propulsion Fuels R&D, Subtask: Optimization of Lipid Production and Processing of Microalgae for the Development of Biofuels

Abstract : Microalgae are considered a suitable feedstock to produce biofuels or bio-oils. Some species are known to naturally accumulate large amounts of lipids as storage metabolites. In the initial phases of this research, native algae were isolated. Techniques for the purification of these algae from field samples were developed, which resulted in the isolation of twenty different microalgae cultures. The major task of this phase was the evaluation and improvement of biomass and lipid production of potential microalgae strains. For this, a direct method was developed for rapid estimation of lipid content of the microalgae of interest. Several laboratory techniques to process microalgae broth were evaluated. Ultrasound at frequencies of 3 MHz, and quartz crystal microbalance (QCM) techniques were tested in terms of response as well as performance to flocculate microalgae cells. Two lipid extraction devices (Soxhlet and Gregar) were tested using different acetone-hexane combinations. Results show that hexane is an appropriate solvent based on the reproducibility and stability in both devices. An economic analysis was performed to determine the most cost-effective algae harvesting process assuming a fix pond site and supercritical extraction unit with an annual production of 222 million pounds of microalgae paste. Analyses show that a process plant, which considers the process of a pond - dewatering - freeze dryer - supercritical fluid extraction is the most attractive in terms of investment due to the lower fixed capital and annual operational costs.