Fuels Researchers Flock to Aquatic Feedstock

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  • By Joseph Gordon, Edwin Corporan
  • Propulsion
WRIGHT-PATTERSON AIR FORCE BASE, Ohio --  Given that "flocculation" is an essential step in amassing aquatic microalgae for subsequent harvest as biofuel feedstock, a lab-sponsored program at the University of Puerto Rico-Mayagüez is researching methods for efficiently performing this all-important concentrating/partitioning process. The scientific community has identified the use of flocculation agents as an efficient means for achieving solid-liquid separation based on its lower costs and energy demands compared to conventional techniques (e.g., centrifugation and filtration). Consequently, Dr. José Colucci and Dr. Govind Nadathur and their students have established the capacity of two specific chemical compounds--ferric chloride (FeCl3) and aluminum sulfate (AlSO4)--to propagate high flocculation efficiency in several local and more common algae strains.

A primary challenge to creating algae-derived fuels lies in the energy-intensive, fairly inefficient processes of separating algae from water and then extracting oil from algae. The work of
Drs. Colucci and Nadathur thus represents a key milestone with respect to the Department of Defense pursuit of alternative (non-petroleum-based) fuel products. Also of significance is the pair's discovery that an FeCl3-AlSO4 combination exhibits flocculation effectiveness greater than that achieved by each agent individually. In addition to demonstrating the viability of
these flocculants, the researchers are investigating ultrasound (via different frequencies and amplitudes and with varying solution pH values) as a mechanism for evaluating algae concentration levels, another principal facet of the preharvest checklist. Thus far, they have identified more efficient flocculation at higher solution pH values and cell concentrations. Finally, the team's study of Soxhlet and Gregar algae oil extractors reveals Gregar as more efficient than the more common Soxhlet unit. While the analytical techniques employed for characterizing algae oil in this project will undergo further development, future studies leveraging these and other innovative techniques will extend the current investigation to include several additional algae strains.