Effect of extraction temperature, time, and solvent type on the oil yield and biodiesel quality of aquatic <i>Azolla pinnata</i>

Ethiopia has faced significant energy challenges arising from its overreliance on fossil fuels and traditional biomass, which deplete natural resources and hinder sustainable socio-economic development. Biodiesel production from locally available aquatic plant species would offer a feasible and sustainable energy alternative. Azolla pinnata, a fast-growing aquatic fern with higher biomass productivity, has been emerged as a promising feedstock for biodiesel production. However, the optimization of processing conditions and their effect on oil yield and fuel quality parameters remain insufficiently understood. The present study, therefore, sought to evaluate the effect of extraction temperature, time, and solvent type on the oil yield and fuel quality of biodiesel derived from Azolla pinnata. The highest oil yield (20.24 ± 0.21%) was obtained from Soxhlet extraction performed at 80 °C for 8 hrs using a 2:1 chloroform-methanol volume ratio. The free fatty acid content, saponification value, and kinematic viscosity of the oil ranged between 0.5–0.6%, 149.70–164.00 mg NaOH/g oil, and 50.29–52.11 mm2/s, respectively. The GC-MS analysis revealed that biodiesel was predominated by saturated stearic (63.4%) and lignoceric (24.7%) fatty acids. The fuel properties predicted from oil’s fatty acid profile, including kinematic viscosity, density, cold filter plugging point, and cetane numbers met the EN14214 and ASTM D6751 standards.