Assessing the Potential of Different Oil Seeds for Biodiesel Synthesis Using Green Nano-Catalysts

Abstract

The present study is confined to identification of novel oil yielding seeds as potential feedstock for sustainable biodiesel production. In this project, eight different oil seeds were investigated systematically on the basis of considerable oil content. This research is focused on feedstock collection, morphological identification, scanning electron microscopic examination, mechanical oil extraction, free fatty acid value (FFA) determination, biodiesel yield optimization, biodiesel characterization via advance analytical techniques and fuel properties comparison with international standards i.e. ASTM D-6751. Different oil seeds selected in this study include Bischofia javanica Blume, Eryobotrya japonica (Thunb.) Lindl., Praecitrulus fistulosus (Stocks) Pangalo, Luffa acutangula (Linn.) Roxb., Diospyros lotus L., Cucumis melo var. Cantalupensis, Solanum surattense Burm. f. and Cucumis melo var. agrestis Naudin. Eight different, affordable, stable and efficient green nano-catalysts were synthesized from same feedstock via biosynthesis method. For this purpose, different plant parts (leaves, seed shells, seed cake, flowers, bark, peel, calyx and seed extract) were used to prepare respective extracts that act as reducing and capping agent. The synthesized green nano-catalysts were characterized by analytical techniques such as X-Ray Diffraction Spectroscopy (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDX) and Fourier Transform Infrared Spectroscopy (FT-IR). All selected seed oils have less than 3% FFA content therefore subjected to single step transesterification directly except non-edible seed oils of Luffa acutangula (3.91 mg/KOH) and Diospyros lotus (6.91 mg/KOH) that require pretreatment for FFA reduction. Hence, Luffa acutangula and Diospyros lotus seed oils were subjected to acid esterification with 1% Sulphuric acid (H2SO4) followed by transesterification. Furthermore, Response Surface Methodology (RSM) was used to optimize the biodiesel yield by adjusting the reaction variables. Results showed the highest biodiesel yield (98%) recorded for Cucumis melo var. Cantalupensis using Calcium oxide (CaO) green nano-catalyst (1:9 oil to methanol ratio, 1.05 wt. % catalyst loading at 70°C for 3h). However, the lowest biodiesel yield (87%) was observed in case of Diospyros lotus catalyzed by Nickle oxide (NiO) green nano-catalyst (1:9 oil to methanol ratio, 1.25 wt. % of NiO catalyst loading at 65°C for 2h). These outcomes clearly show that all the biosynthesized green nano-catalysts were (ZrO2, CoO, CuO, CdO, NiO, CaO, Ag2O and MgO) are renewable, prospective and dynamic for efficient conversion of seed oil I DRSML QAU to cost-effective biodiesel. Based on these experimental results, it is recommended that the renewable feedstocks used in this research for synthesis of both green nano-catalyst and biodiesel be employed for industrial implementation at a global level because it is readily available, economically feasible and ecologically viable. The study also suggests mass cultivation of such substantially innovative feedstock for green energy generation on a commercial scale.