Environmentally Friendly Biodiesel Synthesis from Marine Microalgae Using Calcium Methoxide as a Novel Catalyst

Abstract Biodiesel derived from lipid-rich oils extracted from microalgae holds promise for fulfilling future energy consumption. Three microalgae varieties, namely Nannochloropsis, Tetraselmis, and Isochrysis, were assessed. A novel aspect of this study is the use of calcium methoxide (C₂H₆CaO₂) as a catalyst for transesterification in the production of biodiesel from marine microalgae. Oil yields from 80g of microalgae were determined as follows: 45 ml for Nannochloropsis, 30 ml for Isochrysis, and 20 ml for TetraselmisTop of Form. Furthermore, the calcium methoxide catalyst enhanced biodiesel yield for Nannochloropsis, Tetraselmis, and Isochrysis microalgae by 96%, 93%, and 90%, respectively. Tetra microalgae oil showcases exceptional characteristics with notably low viscosity (13.3 cSt at 40°C), contrasting sharply with Nanno's higher viscosity (39.1 cSt), while Iso falls in between at 25.2 cSt. In colder conditions, Tetra (-3.3°C) and Nanno (-4°C) oils perform well without solidifying, although Iso's slightly superior cloud point (-1.2°C) outperforms Tetra's in lower temperatures. Nanno's high flash point (274°C) ensures greater safety, while its density of 915 kg/m³ stands out among the three, potentially impacting its performance across various applications. Both Tetra (-10°C) and Nanno (-17°C) demonstrate lower pour points, making them more effective in colder environments compared to Iso. The composition of fatty acids differs across these oils: Tetra microalgae oil contains primarily Linoleic acid (50.60±1.2%) and Oleic acid (38.2±0.7%), while ISO sp microalgae oil is predominantly Oleic acid (60.5±1.5%), and NANNO sp contains the highest percentage of Oleic acid (54.7±0.9%) with minimal Linoleic acid (0.4±0.6%). In terms of microalgae biodiesel, Nanno exhibited a viscosity of 6.2 cSt, Tetra had 7.976 cSt, and Iso showed 7.6 cSt, reflecting their individual flow characteristics. Their flash points Nanno at 100.5°C, Tetra at 99.9°C, and Iso at 99.1°C highlight safety during handling. Additionally, Nanno (-39°C), Tetra (-40.8°C), and Iso (-45°C) biodiesels' cloud points imply superior performance in colder temperatures, minimizing the risks of fuel solidification and filter issues. These parameters indicated that marine microalgae biodiesel has the potential to not only meet stringent green fuel standards but also significantly reduce CO₂ emissions across its entire lifecycle, spanning from production to combustion.