OPTIMIZING SUSTAINABLE 3RD GENERATION BIOFUEL PRODUCTION FROM MICROALGAE: CULTIVATION, HARVESTING AND EXTRACTION STRATEGIES

Abstract

The increasing requirement for alternative energy sources has created lot of interest in biodiesel from microalgae such that it is a potential alternative to traditional fossil fuels. This study focuses on optimizing the lipid production from Gonyostomum sp., a microalga, cultivated in two media, synthetic (Conway) and biobased (cow dung infused). Four groups of extraction methods of lipids were tested, Hexane-Methanol extraction with Cow dung infused media (HCD) produced the highest lipid content 23.75 ± 0.20. Further, two different types of FAME extraction were used Type 1 (MeOH + H₂SO₄ + n-hexane) and Type 2 (AOAC Method 991.39). FAME yield was 95.58 ± 0.11%, the highest in AOAC Method 991.39 extraction with Cow dung infused media (Type2s). Fatty acid composition was analyzed by Gas Chromatography-Mass Spectrometry (GC-MS) in order to determine the quality of the biofuel of the lipids. Fatty acid profiles of Gonyostomum sp. were dominated by saturated fatty acids (SFAs) like C16:0 (Palmitic Acid), C18:0 (Stearic Acid), and monounsaturated fatty acids (MUFAs) like C18:1 (Oleic Acid), which are of utmost significance for the production of biodiesel. Extraction with MeOH + H₂SO₄ + n-hexane, Conway Media (Type1c) had the maximum amount of saturated fatty acids (31.65%), while AOAC Method 991.39 extraction with Cow dung infused media (Type2s) had the maximum proportion of unsaturated fatty acids (MUFAs and PUFAs). Iodine value (IV), cetane number (CN), and higher heating value (HHV) were also determined to assess the quality of the biodiesel. Cetane number (CN) values ranged between 58.85 ± 0.00945 for AOAC Method 991.39 extraction with Cow dung infused media (Type2s), the highest. Iodine value (IV) values of all the samples were below 120 g Iodine/100g, which are in accordance with the European biodiesel standards. ANOVA and Tukey's post hoc test was utilized to determine the significance of differences between extraction processes. From the results, maximum efficiency for sustainable production of biodiesel from Gonyostomum sp. is achieved through the integration of biobased (cow dung infused) medium with hexane-methanol and AOAC Method 991.39 Extraction.