Effect of Time and Catalyst Type on Improved Extraction Yield and Lipid Quality as Biodiesel Feedstock from Marine Microalgae Nannochlropsis Oculata in Situ Transesterification Method Microwave Assisted Extraction

Abstract

This study investigates the effect of time and catalyst type on the extraction yield and lipid quality of biodiesel feedstock from marine microalgae Nannochloropsis oculata using the in-situ transesterification method with Microwave Assisted Extraction (MAE). The increasing human population has led to a higher demand for fuel, which is not proportional to the availability of fuel resources, making fuel shortages inevitable. One solution to reduce dependency on fossil fuels is to develop environmentally friendly alternative fuels, such as biodiesel. Biodiesel, derived from plant oils or animal fats, has properties similar to diesel oil. Among Indonesia's vast natural resources, microalgae have significant potential as an alternative raw material for biodiesel production, with Nannochloropsis oculata containing 31-68% lipids. This research explores the transesterification reaction of microalgae oil and methanol using H2SO4 and KOH catalysts, with reaction times of 40, 60, and 80 minutes. The lipid extraction process utilizes MAE, which involves both esterification and transesterification to yield crude biodiesel. Subsequent filtration separates the biodiesel from the formed glycerol. The study aims to determine the extraction yield, Fatty Acid Methyl Ester (FAME) composition, microalgae morphology, and biodiesel quality through % yield calculation, GC-MS analysis, SEM-EDS morphological analysis, and various SNI quality tests. Results indicate that the % yield of biodiesel increases with longer reaction times for both catalysts, with H2SO4 producing higher yields than KOH at all times. GC-MS analysis reveals that the primary FAME components using H2SO4 are methyl hexadecenoate (30.54%) and methyl hexadecenoic (30.08%), while KOH yields are dominated by methyl hexadecenoic (3.83%). SEM-EDS confirms the microalgae as Nannochloropsis oculata, consistent with its cell morphology and elemental composition. SNI tests show that H2SO4 increases density with reaction time (1.0127-1.0341 g/mL), while KOH decreases (0.8213-0.6716 g/mL), with the 40-minute KOH reaction yielding biodiesel closest to SNI standards (0.85-0.89 g/mL). Viscosity tests for both catalysts fall within SNI ranges (2.3-6.0), and acid numbers are well below maximum SNI limits, indicating excellent quality. Total glycerol values for both catalysts (0.1326%-0.2318%) meet SNI 7182:2015 standards, with the highest at H2SO4 40 minutes (0.2318%) and the lowest at H2SO4 60 minutes (0.1326%).