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Young Naturalist Probes Algae's Green Potential

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Sara conducted an experiment to see how environmental stresses affected the oil yield of algae. 
Photo courtesy of Sara.

Fifteen-year-old Sara knew that vegetable oils could be used as biofuels. But when she learned that algae might offer an alternative fuel source, she decided to learn more about these organisms’ potential to supply energy without using precious crop land.

Surveying gaps in current research, Sara decided to explore how growing conditions of algae might affect their oil yields. Sara received a 2011 Young Naturalist Award for her experiment, which she describes in her essay Enhancing Algae Biofuels: The Effects of Nitrogen Limitation and Carbon Dioxide Infusion on Nannochloropsis oculata.

Sara decided she would measure whether nitrogen limitation and carbon dioxide infusion could enhance algae growth and the amount of lipids produced. Though environmental “stresses” like a nitrogen deficit might slow overall growth rates, Sara hypothesized that some stresses might make algae a more efficient fuel source if they significantly increased lipid production.

Sara examined three groups of algal cultures: nitrogen-depleted cultures, carbon dioxide-infused cultures, and control cultures. She conducted the testing in a photobioreactor that she built. After testing, she measured the dry weight and lipid content of each of the cultures, and then divided the extracted lipid quantities by the original dry mass of the algae to get the relative amount of lipid per sample. By then multiplying the amount of lipid per sample with the overall amount of algae produced, she could estimate the oil yield and see whether the benefits of growing algae in these conditions outweighed any loss in biomass.

According to Sara’s calculations, the nitrogen-depleted cultures resulted in higher oil yields and higher lipid percentages. Her carbon dioxide-infused samples, however, quickly died off, most likely due to acidification of the culture by the CO2.

While Sara now understands more about optimizing algal biofuels, perhaps the most important lesson she learned was about the scientific process. “This experiment provided me with information not only on how COinfusion and nitrogen limitation affect N. oculata growth and lipid content, but also on how certain procedures tend to affect those results,” she writes in her essay. And since she learned a few new laboratory techniques during her investigation, Sara says she will now be equipped for her “future forays into the mysteries of algae.”

The Young Naturalist Awards is a nationwide, science-based research contest for students in grades 7 through 12 presented by the Museum. To learn more and to submit your own project, visit The deadline for the 2012 contest is March 9, 2012.

The Young Naturalist Awards are proudly supported by Alcoa Foundation.