Advancing Renewable Fuel Production from the Macroalga Ulva lactuca through Integrated Optimization of Biodiesel Yield and Physicochemical Properties

Abstract Algae-derived lipids are promising renewable feedstocks for biodiesel production. However, efficient conversion requires optimization of transesterification conditions to maximize biodiesel yield. This study aimed to optimize biodiesel production from Ulva lactuca lipids using potassium hydroxide-catalyzed transesterification. Lipids were extracted from dried biomass using Soxhlet extraction, and Response Surface Methodology (RSM) was applied to evaluate the effects of catalyst loading, reaction temperature, and reaction time through 14 experimental runs. The developed model identified optimum conditions of 0.1 wt % catalyst loading, 75 °C, and 75 min, achieving a maximum experimental biodiesel yield of 89%. The produced biodiesel exhibited a density of 862 kg/m3, kinematic viscosity of 5.50 mm2/s, flash point of 179 °C, and acid value of 1.68 mg KOH/g. While several properties met the applicable ASTM D6751 and/or EN 14214 specifications, the acid value exceeded the specified limit, indicating the need for further improvement in fuel quality. The RSM effectively identified suitable transesterification conditions for maximizing biodiesel yield from Ulva lactuca lipids, supporting its potential as a nonfood feedstock for renewable fuel production. These findings demonstrate the value of process optimization in advancing Ulva lactuca as an alternative nonfood lipid resource for sustainable biodiesel development.