Energy

Optimizing Nannochloropsis Growing Conditions for Biodiesel Production Through Analysis of Lipid Content

Steven Liu Shady Side Academy Senior School
,

Abstract

Fossil fuels have propelled society to our current technology, but the future of energy lies in renewable resources, starting with vehicles. Despite constituting only 5% of the total vehicles in the United States, medium to heavy-duty trucks, which consume diesel fuel, are responsible for an astounding 23% of annual CO2 emissions in the transportation sector. The full implementation of greener biodiesel is often deemed an infeasible method for mitigating pollution because the production of such biodiesel directly competes with the agricultural industry for the available arable land. Energy-dense algae are more suitable feedstocks for biodiesel and circumvent many of the problems posed by current biodiesel feedstocks, and their potential can be used to propel the biodiesel industry into the future of sustainable energy. Nannochloropsis is a promising genus of algae due to its high productivity and lipid content. Here I show how to optimize the growing medium composition for increased biodiesel quality while maintaining high productivity by quantifying the constituent fatty acid type and composition using gas chromatography (GC). The algae are grown in two groups of three 2.5 L glass jugs spanning three concentration levels of nitrates and phosphates. A growing “f/2” medium is kept constant across trials. The algae are harvested using a flocculating solution of aluminum sulfate and vacuum filtration. In situ transesterification is used to achieve maximum conversion of fatty acids into fatty acid methyl esters, which are then analyzed using GC. The algae grown in low, medium, and high nutrient concentrations produced average absorbance values (a measure of biomass concentration) at 750 nm of 0.91, 0.99, and 1.18, respectively, after 32 days of growth. The maximum monounsaturated fatty acid (MUFA) concentration of 62.68% of total fatty acids was reached in a low nutrient concentration, which corresponds to high-quality biodiesel. Through this study, a scientific breakthrough was achieved by maximizing both the quality of biodiesel produced, which is beyond any currently available biodiesel, and also the quantity with a productivity of greater than 100 times the current biodiesel feedstocks.

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