Study finds algae growth, harvesting are root of energy ROI

By Erin Voegele | July 27, 2011

A study recently published by researchers at the University of Texas, Austin asserts that the crux of algae’s case as an economically feasible oil feedstock and energy source rests not in its processing but in the ability to affordably grow and harvest it. The study, titled “Energy Return on Energy Investment for Algal Biocrude: Results for a Research Production Facility,” was funded by algae process technology developer OpenAlgae LLC and published in the scientific journal BioEnergy Research.

The energy return on investment (EROI) study focused on algae oil production at a University of Texas, Austin research facility. An abstract for the research notes that as part of the assessment algae were grown on several different scales and processed using centrifugation, electromechanical cell lysing and a microporous hollow fiber membrane. The study elaborates that algae used involved in the evaluation were grown in four stages, including flasks in a lab, indoor photobioreactors, greenhouse tanks, and covered outdoor ponds. “To determine the EROI, a second-order analysis was conducted, which includes direct and indirect energy flows, but does not include energy expenses associated with capital investments,” state the authors in the study.

According to the study, the evaluation represents the first known experimental results with end-to-end measurements for determining the EROI of an integrated algae-based biocrude plant. While the EROI for the process evaluated by the study was less than one, the authors point out the result of a single, research system that was not designed to optimize EROI. In comparison, the study notes that the EROI for the production of oil and gas, coal, wind energy and corn ethanol have been estimated to be set at relative levels of 15, 80, 19 and one.

“Under the conditions modeled with new processing technologies, the cost to lyse cells and separate algal oil from water and biomass can be just 1 percent of the total production cost of algal oil,” said Dr. Peter Kipp, vice president at OpenAlgae. “New technologies are also driving down the cost of harvesting dilute algae.”

OpenAlgae has developed concentration, electromechanical cell lysis and solvent-free oil recovery technologies for renewable oil platforms. The company elaborates that a significant benefit of its oil separation technique is that solvents are not used. OpenAlgae said that the lack of solvents could potentially open new, higher-value markets for de-oiled biomass than anaerobic digestion.

“This research confirms what we’ve been hearing from algae growers,” said OpenAlgae CEO Hoyt Thomas. “Enormous effort is going into improving productivities of algae, both through the use of waste streams and through improved biology to achieve higher cell densities.  The last hurdle on the processing side is harvesting; higher density algae cultures will also be harvested more cost effectively. OpenAlgae’s oil recovery technologies offer radically improved economics and opportunities over traditional separation methods like solvent extraction, because there are no waste streams.”


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